Gamma-ray Burst 231115A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 15 Nov 23 15:36:50 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      48
TRIGGER_NUM:     721755386
GRB_RA:          152.767d {+10h 11m 04s} (J2000),
                 153.193d {+10h 12m 46s} (current),
                 151.866d {+10h 07m 28s} (1950)
GRB_DEC:         +63.417d {+63d 25' 00"} (J2000),
                 +63.298d {+63d 17' 54"} (current),
                 +63.663d {+63d 39' 48"} (1950)
GRB_ERROR:       6.38 [deg radius, statistical plus systematic]
GRB_INTEN:       1446 [cnts/sec]
DATA_SIGNIF:     17.40 [sigma]
INTEG_TIME:      0.064 [sec]
GRB_DATE:        20263 TJD;   319 DOY;   23/11/15
GRB_TIME:        56181.20 SOD {15:36:21.20} UT
GRB_PHI:         243.00 [deg]
GRB_THETA:        40.00 [deg]
DATA_TIME_SCALE: 0.0640 [sec]
HARD_RATIO:      0.15
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      98%  GRB
2nd_MOST_LIKELY:   1%  Generic SGR
DETECTORS:       0,0,0, 1,0,0, 1,1,1, 1,1,1, 0,0,
SUN_POSTN:       230.61d {+15h 22m 26s}  -18.52d {-18d 31' 15"}
SUN_DIST:        101.01 [deg]   Sun_angle= 5.2 [hr] (West of Sun)
MOON_POSTN:      259.73d {+17h 18m 55s}  -27.40d {-27d 23' 51"}
MOON_DIST:       121.64 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      147.18, 45.44 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      126.20, 47.65 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231115650/quicklook/glg_lc_medres34_bn231115650.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 354.20,17.85 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the INTEGRAL event (trignum=10427).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 15 Nov 23 15:37:16 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      59
TRIGGER_NUM:     721755386
GRB_RA:          138.650d {+09h 14m 36s} (J2000),
                 139.215d {+09h 16m 52s} (current),
                 137.452d {+09h 09m 48s} (1950)
GRB_DEC:         +71.450d {+71d 27' 00"} (J2000),
                 +71.350d {+71d 20' 59"} (current),
                 +71.657d {+71d 39' 25"} (1950)
GRB_ERROR:       7.22 [deg radius, statistical only]
DATA_SIGNIF:     22.90 [sigma]
DATA_INTERVAL:   0.064 [sec]
GRB_DATE:        20263 TJD;   319 DOY;   23/11/15
GRB_TIME:        56181.20 SOD {15:36:21.20} UT
GRB_PHI:         228.00 [deg]
GRB_THETA:        38.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       230.61d {+15h 22m 26s}  -18.52d {-18d 31' 16"}
SUN_DIST:        107.96 [deg]   Sun_angle= 6.1 [hr] (West of Sun)
MOON_POSTN:      259.73d {+17h 18m 56s}  -27.40d {-27d 23' 53"}
MOON_DIST:       125.46 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      141.71, 36.72 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      112.73, 51.83 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231115650/quicklook/glg_lc_medres34_bn231115650.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_721755386.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        Bright hard burst in the GBM.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the INTEGRAL event (trignum=10427).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 15 Nov 23 15:45:37 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     721755386
GRB_RA:          131.010d {+08h 44m 02s} (J2000),
                 131.652d {+08h 46m 36s} (current),
                 129.649d {+08h 38m 36s} (1950)
GRB_DEC:         +73.490d {+73d 29' 24"} (J2000),
                 +73.402d {+73d 24' 08"} (current),
                 +73.670d {+73d 40' 13"} (1950)
GRB_ERROR:       8.67 [deg radius, statistical only]
GRB_DATE:        20263 TJD;   319 DOY;   23/11/15
GRB_TIME:        56181.20 SOD {15:36:21.20} UT
GRB_PHI:         223.00 [deg]
GRB_THETA:        38.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       230.61d {+15h 22m 28s}  -18.52d {-18d 31' 21"}
SUN_DIST:        110.28 [deg]   Sun_angle= 6.6 [hr] (West of Sun)
MOON_POSTN:      259.82d {+17h 19m 17s}  -27.41d {-27d 24' 28"}
MOON_DIST:       126.72 [deg]
MOON_ILLUM:      6 [%]
GAL_COORDS:      140.48, 33.81 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      107.88, 52.59 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231115650/quicklook/glg_lc_medres34_bn231115650.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231115650/quicklook/glg_locplot_all_bn231115650.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice was generated completely by automated pipeline processing.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        Bright hard burst in the GBM.  
COMMENTS:        This is likely a Short GRB.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the INTEGRAL event (trignum=10427).

GCN Circular #35035
The Fermi GBM team reports the detection of a likely SHORT GRB
At 15:36:21 UT on 15 Nov 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 231115A (trigger 721755386.20138 / 231115650).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 131.0, Dec = 73.5 (J2000 degrees, equivalent to J2000 08h 43m, 73d 30'), with a statistical uncertainty of 8.7 degrees.
The angle from the Fermi LAT boresight is 38.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231115650/quicklook/glg_skymap_all_bn231115650.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231115650/quicklook/glg_healpix_all_bn231115650.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231115650/quicklook/glg_lc_medres34_bn231115650.gif
GCN Circular #35036
P. D=E2=80=99Avanzo (INAF - OAB), E. Palazzi (INAF - OAS), S. Campana (INAF - OAB), M. G. Bernardini (INAF - OAB), D. B. Malesani (DAWN/NBI & Radboud Univ.) on behalf of the CIBO collaboratio report:
GRB 231115A has been recently detected by Fermi/GBM (Fermi GBM team, GCN Circ. 35035) and INTEGRAL (https://gcn.gsfc.nasa.gov/other/10427.integral ).
We note that the INTEGRAL position (which has an uncertainty radius or 3 arcmin) is consistent with the position of the M 82 galaxy (luminosity distance of ~ 3.5 Mpc).
Follow-up observations are encouraged.
GCN Circular #35037
S.Mereghetti (INAF, IASF-Milano), D.Gotz (CEA, Saclay), C.Ferrigno, E.Bozzo, V.Savchenko (ISDC, Versoix), L.Ducci (IAAT, Germany and ISDC, Versoix) and J.Borkowski (CAMK, Torun) report:
a short hard burst lasting about 150 ms has been detected by IBAS in the IBIS/ISGRI data at 15:36:22 UT of November 15, 2023.
The refined coordinates (J2000) are:
```
R.A.= 149.000901 [degrees] 
DEC.=  69.680130  [degrees]
```
with an uncertainty of 2 arcmin (90% c.l.).
We note that this position is consistent with the galaxy M82, so this event, which also triggered Fermi/GBM, may be due to a magnetar giant flare or to a nearby merger. So we encourage follow-up at other wavelengths.
A plot of the light curve will be posted at http://ibas.iasf-milano.inaf.it/IBAS_Results.html
GCN Circular #35038
Eric Burns (LSU)
INTEGRAL has localized the GRB 231115A to be coincident with the nearby, star-forming galaxy M82, suggesting a possible giant flare origin (S.Mereghetti et al., GCN 35037). Using the method in [1] we estimate the Bayes factor that this is a giant flare from M82 vs neutron star merger GRB with a chance alignment to be approximately 180,000 to 1. The corresponding value for GRB 200415A, the previous most confident event is 6,000 to 1. The false alarm rate for GRB 231115A is beyond 4.5 sigma in Gaussian-equivalent significance. This is a lower bound as the necessary background simulations for more confident constraints will take weeks to run. We report this to support additional follow-up
We emphasize this is a very preliminary significance estimate, using code which had to be quickly modified and updated to handle Python package updates that occurred since it was last used, and it has not been checked carefully.
[1] E Burns et al., ApjL 907 2 2021

GCN Circular #35039
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko, G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gress, N.M. Budnev, O.Ershova (Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich (Blagoveschensk Educational State University)
MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 231115A ( Fermi GBM team, GCN 35035) errorbox 4601 sec after notice time and 4635 sec after trigger time at 2023-11-15 16:53:37 UT, with upper limit up to 18.8 mag. The observations began at zenith distance = 47 deg. The sun altitude is -57.5 deg.
The galactic latitude b = 34 deg., longitude l = 141 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2306520
We obtain a following upper limits.

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    4726 | 2023-11-15 16:53:37 |        MASTER-Tunka | (09h 52m 05.00s , +66d 57m 09.9s) |   C |   180 | 14.1 |        
    4726 | 2023-11-15 16:53:37 |        MASTER-Tunka | (09h 53m 24.26s , +67d 39m 25.7s) |   C |   180 | 18.8 |        
    4890 | 2023-11-15 16:57:06 |        MASTER-Tunka | (09h 52m 11.37s , +66d 56m 35.9s) |   C |    90 | 15.5 |        
    4890 | 2023-11-15 16:57:06 |        MASTER-Tunka | (09h 53m 31.95s , +67d 38m 26.3s) |   C |    90 | 18.1 |        
    5007 | 2023-11-15 16:59:02 |        MASTER-Tunka | (09h 52m 07.51s , +66d 55m 13.1s) |   C |    90 | 13.3 |        
    5007 | 2023-11-15 16:59:03 |        MASTER-Tunka | (09h 53m 26.66s , +67d 37m 26.5s) |   C |    90 | 18.0 |        
    5124 | 2023-11-15 17:01:00 |        MASTER-Tunka | (09h 52m 12.62s , +66d 55m 43.4s) |   C |    90 | 15.3 |        
    5124 | 2023-11-15 17:01:00 |        MASTER-Tunka | (09h 53m 33.01s , +67d 37m 31.8s) |   C |    90 | 18.0 |        
    5242 | 2023-11-15 17:02:58 |        MASTER-Tunka | (09h 52m 11.14s , +66d 57m 23.6s) |   C |    90 | 15.4 |        
    5242 | 2023-11-15 17:02:58 |        MASTER-Tunka | (09h 53m 31.53s , +67d 39m 11.8s) |   C |    90 | 17.9 |        
    5356 | 2023-11-15 17:04:52 |        MASTER-Tunka | (09h 53m 32.24s , +67d 37m 28.1s) |   C |    90 | 17.6 |        
    5475 | 2023-11-15 17:06:50 |        MASTER-Tunka | (09h 52m 15.59s , +66d 57m 34.6s) |   C |    90 | 15.3 |        
    5475 | 2023-11-15 17:06:51 |        MASTER-Tunka | (09h 53m 35.65s , +67d 39m 20.1s) |   C |    90 | 17.6 |        
    5593 | 2023-11-15 17:08:49 |        MASTER-Tunka | (09h 52m 10.80s , +66d 56m 43.7s) |   C |    90 | 15.1 |        
    5593 | 2023-11-15 17:08:49 |        MASTER-Tunka | (09h 53m 30.64s , +67d 38m 28.1s) |   C |    90 | 17.7 |        
    5710 | 2023-11-15 17:10:46 |        MASTER-Tunka | (09h 52m 11.18s , +66d 57m 44.6s) |   C |    90 | 15.0 |        
    5710 | 2023-11-15 17:10:46 |        MASTER-Tunka | (09h 53m 30.87s , +67d 39m 28.0s) |   C |    90 | 17.6 |

Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.

GCN Circular #35040
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the INTEGRAL GRB 231115A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021625
Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the INTEGRAL event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular #35041
R. Kumar, A. Salgundi, V. Swain, Y. Wagh, V. Bhalerao (IIT Bombay), G. C. Anupama, S. Barway (IIA), R. Norboo (IAO), T. Ahumada, V. Karambelkar, M. M. Kasliwal (Caltech) report on behalf of a larger collaboration
We observed the field of GRB 231115A (Fermi GBM Team, GCN 35035) with 0.7m GROWTH India telescope. We started observations at 2023-11-15 16:47:58.140 UT, 1.19 hours after the fermi trigger (as soon as the source became visible). We obtained multiple 300s exposures in multiple filters. We have multiple detections of a transient AT 2023xvj at RA = 09:56:00.2, Dec = 69:40:29.2, with r' = 19.2. Owing to the dense background, current total astrometric uncertainty is about 0.6". The source is 0.3' from the reported Integral position, consistent with their 2' uncertainty. The magnitudes are calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction.
At this stage, we cannot rule out that this might be Nova or some other transient in M82. Further imaging and analysis is under way. We strongly encourage follow-up observations.
The GROWTH India Telescope (GIT, Kumar et al., 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.
GCN Circular #35042
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko, G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gress, N.M. Budnev, O.Ershova (Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich (Blagoveschensk Educational State University)
MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the Integral GRB231115.65 (trigger No 10427,09h 56m 07.98s , +69d 41m 21.3s, R=0.0511667) errorbox 4607 sec after notice time and 4634 sec after trigger time at 2023-11-15 16:53:37 UT, with upper limit up to 20.0 mag. The observations began at zenith distance = 47 deg. The sun altitude is -57.5 deg.
The galactic latitude b = 41 deg., longitude l = 141 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2306494
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

    4725 |        MASTER-Tunka |   C |   180 | 18.8 |        
    5241 |        MASTER-Tunka |   C |    90 | 17.9 |        
    5473 |        MASTER-Tunka |   C |    90 | 17.6 |        
    5708 |        MASTER-Tunka |   C |    90 | 17.6 |        
   10669 |        MASTER-Tunka |   C |   180 | 19.2 |        
   10829 |        MASTER-Tunka |   C |    90 | 18.8 |        
   11178 |        MASTER-Tunka |   C |    90 | 19.2 |        
   11409 |        MASTER-Tunka |   C |    90 | 19.4 |        
   11524 |        MASTER-Tunka |   C |    90 | 19.5 |        
   11638 |        MASTER-Tunka |   C |    90 | 19.6 |        
   11724 |        MASTER-Tunka |   C |    30 | 19.8 |        
   11840 |        MASTER-Tunka |   C |    30 | 20.0 |        
   11898 |        MASTER-Tunka |   C |    30 | 20.0 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #35043
A.J. Levan (Radboud), B. Gompertz (Birmingham), D.B. Malesani (DAWN/NBI) report:
The field of GRB 231115A (Mereghetti et al. GCN 35037) has been previously observed on several occasions by the Hubble Space Telescope via targeted observations of M82. Visual inspection of the location of the suggested candidate identified by Kumar et al. (GCN 35041) indicates that the environment is unremarkable. In blue observations obtained in F435W (GO 10776, 29-03-2006), the source lies on the stellar field of the host galaxy, but no readily identifiable discrete sources can be seen (e.g. massive stars or star-forming regions). In the IR, the field resolves into a larger number of discrete sources, likely due to the smaller extinction. Several sources are present within the 0.6=E2=80=9D error region in F110W observations (GO 11360, 01-01-2010) with magnitudes around F110W=3D22 (AB). However, the density of such sources at this location in the galaxy is such that none is an outstanding candidate to be physically associated with the optical transient identified by Kumar et al.
We note that this location is relatively remote from the bulk of M82 and is not obviously associated with substantial star-forming activity. Although not unprecedented, this would be a somewhat unusual location for a magnetar giant flare.
GCN Circular #35044
S. Dalessi (UAH), O.J. Roberts (USRA/NASA-MSFC), P. Veres (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 15:36:21.20 UT on 15 November 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 231115A (trigger 721755386/231115650). which was also detected by Integral (P. D'Avanzo et al. 2023, GCN 35036 and S.Mereghetti et al. 2023, GCN 35037). The Fermi GBM Final Real-time Localization is reported in GCN 35035 and is consistent with the Integral position.
The angle from the Fermi LAT boresight is 38 degrees.
The GBM light curve single peak with a duration (T90) of about 0.03 s (50-300 keV). The time-averaged spectrum from T0-0.02 to T0+0.02 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is 0.5 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 580 +/- 60 keV.
The event fluence (10-1000 keV) in this time interval is (6.3 +/- 0.4)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 11 +/- 1 ph/s/cm^2.
Using the distance to M82 of 3.5 Mpc (P. D'Avanzo et al. 2023, GCN 35036), we derive an Eiso of 1.4e45 ergs and Liso of 1.9e46 erg s-1 (64 ms, 1-10,000 keV). This with the rise time of ~2 ms, hard spectral slope and soft-hard-soft spectral evolution of the event, are consistent with an MGF origin.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular #35045
C.C. Cheung, M. Kerr, J. E. Grove, R. Woolf (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge (MSFC), and M.S. Briggs (UAH) report:
The Glowbug gamma-ray telescope [1,2], operating on the International Space Station, reports the detection of GRB 231115A, which was also detected by Fermi/GBM and IBAS, and found to be positionally consistent with M82 (GCN 35035, 35036, 35037, 35038, 35044).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2023-11-15 15:36:20.184 with a duration of 0.064 s and a total significance of about 23.3 sigma. The light curve comprises a single peak.
Using a standard power-law function with an exponential high-energy cutoff [3] to model the emission over this duration results in a photon index dN/dE~E^x of x=3D1.0 and a cutoff energy ("Epeak") of 561 keV. The modeled 10-10000 keV fluence is 4e-07 erg/cm^2.
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program=E2=80=99s STP-H9 to the ISS. The detector comprises 12 large-area (15 cm x 15 cm) CsI:Tl panels covering the surface of a half cube, and two hexagonal (5-cm diameter, 10-cm length) CLLB scintillators, giving it a large field of view (instantaneous FoV ~2/3 sky) over a wide energy band of 50 keV to >2 MeV.
```
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Goldstein, A. et al. 2020, ApJ 895, 40, arXiv :1909.03006
```
Distribution Statement A: Approved for public release. Distribution is unlimited.

GCN Circular #35046
P.Balanutsa (Lomonosov MSU), N.Budnev, O.Gress (ISU,API),A.Sankovich V. Lipunov, E. Gorbovskoy, N. Tiurina, D.Vlasenko, Yu.Tselik, Ya.Kechin, A.Kuznetsov, K.Zhirkov, A.Chasovnikov, I.Gorbunov, D.Zimnukhov, V.Senik, V.Topolev, D.Cheryasov, A.Sosnovskij, V.Senik (Lomonosov Moscow State University, SAI, Physics Department), R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico FelixAguilar OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational State University)
MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the GRB 231115A (Fermi GBM Team GCN 35035, Mereghetti et al., GCN 35037) errorbox 4607 sec after notice time and 4634 sec after trigger time at 2023-11-15 16:53:37 UT, with upper limit up to 21.3 mag.
Our first images (till T0+10669) are ruined due to bad weather conditions. Sinces T0+10669, during the observations the weather improved. The list of limits up to 21.3 is presented in the table below. In pictures with the maximum limit we do not see the source. In all our frames, the object GAIA 1070550388423847680 with a magnitude of 19.44, closest to the indicated area in (Kumar et al GCN 35041), is clearly visible. The localization region of OT (Kumar et al GCN 35041) has a diffuse structure, but we definitely do not see a source there with a brightness of 19.5 or brighterat given position. Despite the presence of images with deeper upper limits, due to the diffuse structure of the galaxy in the localization region, it is difficult to talk about weaker sources in the preliminary analysis.
We obtain a following upper limits.

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

    4725 |        MASTER-Tunka |   C |   180 | 18.8 |
    5241 |        MASTER-Tunka |   C |    90 | 17.9 |
    5473 |        MASTER-Tunka |   C |    90 | 17.6 |
    5708 |        MASTER-Tunka |   C |    90 | 17.6 |
   10669 |        MASTER-Tunka |   C |   180 | 19.2 |
   10829 |        MASTER-Tunka |   C |    90 | 18.8 |
   11178 |        MASTER-Tunka |   C |    90 | 19.2 |
   11409 |        MASTER-Tunka |   C |    90 | 19.4 |
   11524 |        MASTER-Tunka |   C |    90 | 19.5 |
   11638 |        MASTER-Tunka |   C |    90 | 19.6 |
   11724 |        MASTER-Tunka |   C |    30 | 19.8 |
   11840 |        MASTER-Tunka |   C |    30 | 20.0 |
   11885 |        MASTER-Tunka |   C |   120 | 20.7 |  Coadd
   12230 |        MASTER-Tunka |   C |   810 | 21.1 |  Coadd
   11898 |        MASTER-Tunka |   C |    30 | 20.0 |
   11968 |        MASTER-Tunka |   C |    60 | 14.5 |
   11968 |        MASTER-Tunka |   C |    60 | 20.2 |
   12056 |        MASTER-Tunka |   C |    60 | 20.4 |
   12146 |        MASTER-Tunka |   C |   240 | 20.4 |  Coadd
   12158 |        MASTER-Tunka |   C |    90 | 19.9 |
   12273 |        MASTER-Tunka |   C |    90 | 19.9 |
   12399 |        MASTER-Tunka |   C |    90 | 20.0 |
   12489 |        MASTER-Tunka |   C |   270 | 20.4 |  Coadd
   12514 |        MASTER-Tunka |   C |    90 | 20.0 |
   12630 |        MASTER-Tunka |   C |    90 | 20.0 |
   12848 |        MASTER-Tunka |   C |    90 | 19.9 |
   13045 |        MASTER-Tunka |   C |    60 | 20.5 |
   13105 |        MASTER-Tunka |   C |   180 | 21.1 |  Coadd
   13285 |        MASTER-Tunka |   C |   540 | 21.0 |  Coadd
   13132 |        MASTER-Tunka |   C |    60 | 20.5 |
   13218 |        MASTER-Tunka |   C |    60 | 20.5 |
   13306 |        MASTER-Tunka |   C |    60 | 20.5 |
   13366 |        MASTER-Tunka |   C |   180 | 21.0 |  Coadd
   13391 |        MASTER-Tunka |   C |    60 | 20.5 |
   13478 |        MASTER-Tunka |   C |    60 | 20.5 |
   13564 |        MASTER-Tunka |   C |    60 | 20.5 |
   13624 |        MASTER-Tunka |   C |   180 | 21.1 |  Coadd
   13648 |        MASTER-Tunka |   C |    60 | 14.9 |
   13648 |        MASTER-Tunka |   C |    60 | 20.5 |
   13733 |        MASTER-Tunka |   C |    60 | 20.5 |
   13820 |        MASTER-Tunka |   C |    60 | 15.2 |
   13821 |        MASTER-Tunka |   C |    60 | 20.5 |
   13881 |        MASTER-Tunka |   C |   180 | 21.0 |  Coadd
   13907 |        MASTER-Tunka |   C |    60 | 20.5 |
   13993 |        MASTER-Tunka |   C |    60 | 20.5 |
   14095 |        MASTER-Tunka |   C |    90 | 19.9 |
   14201 |        MASTER-Tunka |   C |    60 | 20.5 |
   14261 |        MASTER-Tunka |   C |   180 | 21.2 |  Coadd
   14288 |        MASTER-Tunka |   C |    60 | 20.5 |
   14377 |        MASTER-Tunka |   C |    60 | 20.5 |
   14463 |        MASTER-Tunka |   C |    60 | 15.6 |
   14463 |        MASTER-Tunka |   C |    60 | 20.5 |
   14523 |        MASTER-Tunka |   C |   180 | 21.1 |  Coadd
   14548 |        MASTER-Tunka |   C |    60 | 20.5 |
   14633 |        MASTER-Tunka |   C |    60 | 20.5 |
   14717 |        MASTER-Tunka |   C |    60 | 15.5 |
   14718 |        MASTER-Tunka |   C |    60 | 20.5 |
   14778 |        MASTER-Tunka |   C |   180 | 21.2 |  Coadd
   14805 |        MASTER-Tunka |   C |    60 | 20.6 |
   14885 |        MASTER-Tunka |   C |    60 | 20.6 |
   14973 |        MASTER-Tunka |   C |    60 | 20.6 |
   15033 |        MASTER-Tunka |   C |   180 | 21.3 |  Coadd
   15060 |        MASTER-Tunka |   C |    60 | 15.4 |
   15061 |        MASTER-Tunka |   C |    60 | 20.6 |
   15147 |        MASTER-Tunka |   C |    60 | 20.6 |
   15233 |        MASTER-Tunka |   C |    60 | 15.6 |
   15233 |        MASTER-Tunka |   C |    60 | 20.5 |
   15293 |        MASTER-Tunka |   C |   180 | 21.1 |  Coadd
   15381 |        MASTER-Tunka |   C |   180 | 20.6 |
   15533 |        MASTER-Tunka |   C |    60 | 20.5 |
   15620 |        MASTER-Tunka |   C |    60 | 20.5 |
   15705 |        MASTER-Tunka |   C |    60 | 20.3 |
   15765 |        MASTER-Tunka |   C |   180 | 20.8 |  Coadd
   15796 |        MASTER-Tunka |   C |    60 | 20.3 |
   15885 |        MASTER-Tunka |   C |    60 | 20.4 |
   15966 |        MASTER-Tunka |   C |    60 | 20.4 |
   16051 |        MASTER-Tunka |   C |    60 | 14.6 |
   16051 |        MASTER-Tunka |   C |    60 | 20.3 |

Filter C is a clear (unfiltred) band.
Real time updated cover map and actual upper limits list available here: https://master.sai.msu.ru/site/master2/observ.php?id=2306494
The observations began at zenith distance = 47 deg. The sun altitude is -57.5 deg. The galactic latitude b = 41 deg., longitude l = 141 deg. The message may be cited.

GCN Circular #35048
FROM: Tomas Ahumada Mena at Caltech
Tomas Ahumada (CIT), Jacob Wise (LJMU), Michael Coughlin (UMN), on behalf o= f the ZTF and GROWTH collaboration:=20
We serendipitously observed the localization region of GRB 231115A (GCN 350= 35) as part of routine Zwicky Transient Facility (ZTF; Graham et al., 2019;= Bellm et al., 2019) survey operations. We most recently obtained images in= the g-, and r-bands beginning ~1.2 days before the trigger time. We repor= t recent upper limits for the GRB optical counterpart candidate AT 2023xvj/= GIT231115aa (GCN 35041) in the table below:=20
```
Filter | mjd | mag lim (AB mag)
----------------------
r  | 60262.4944329 | 20.47
g | 60262.4463542 | 20.37
```
Additionally, we ran forced photometry on ZTF images (Masci et al. 2019) at= the location of the transient, and found no previous activity at the 4 sig= ma level since the beginning of the ZTF survey (March 2018).
We note the latest ATLAS (Tonry et al. 2018, Smith et al. 2020) observations of the field were 7 days prior to the burst, reaching a limit of 19.2 mag in the r-band.
ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, = USA; WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germa= ny; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IITB, Ind= ia; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and USyd, Australia. ZTF ackn= owledges the generous support of the NSF under AST MSIP Grant No 1440341. G= ROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949.= Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). A= lert database searches are done by AMPEL (Nordin et al. 2019) and Kowalski = (Duev et al. 2019). GROWTH India telescope is located at the Indian Astrono= mical Observatory (Hanle), operated by the Indian Institute of Astrophysics= (IIA). GROWTH-India project is supported by SERB and administered by IUSST= F, under grant number IUSSTF/PIRE Program/GROWTH/2015-16 and IUCAA. Fritz a= nd SkyPortal acknowledge the generous support of The Gordon and Betty Moore= Foundation, through the Data-Driven Investigator Program.
GCN Circular #35049
The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report:
At the time of GRB 231115A, the LIGO Hanford Observatory (H1) was observing with a binary neutron star (BNS) merger average sensitive range of ~150 Mpc. The low-latency pipelines for compact binary mergers [1-4] were operational at the time of the GRB. No gravitational-wave candidates were found in a window of [-5, +1] seconds around GRB 231115A [5]. We find that H1 was sensitive to gravitational waves from both Fermi (GCN 35035) and INTEGRAL (GCN 35036, 35037) sky positions. An offline analysis will be performed to search for extremely weak gravitational-wave signals and determine exclusion limits.
```
[1] Tsukada et al. PRD 108, 043004 (2023) and Ewing et al. arXiv:2305.05625 (2023)
[2] Aubin et al. CQG 38, 095004 (2021)
[3] Dal Canton et al. ApJ 923, 254 (2021)
[4] Chu et al. PRD 105, 024023 (2022)
[5] Urban, A. L. 2016, Ph.D. Thesis https://dc.uwm.edu/etd/1218 and Piotrzkowski, B. J. 2022, Ph.D. Thesis https://dc.uwm.edu/etd/3060 
```
GCN Circular #35050
K. Ackley, D. Steeghs, B. P. Gompertz, A. J. Levan, D. B. Malesani, R. Starling, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, A. Kumar, D. O'Neill, D. K. Galloway, V. Dhillon, P. O'Brien; G. Ramsay, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Pall'e and D. Pollacco report on behalf of the GOTO collaboration:
The Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022) serendipitously covered the field of GRB 231115A (Fermi GBM Team, GCN 35035; Mereghetti et al, GCN 35037; Cheung et al. GCN 35045) at 04:44:17 UT on 2023-11-15. This is 10.87 hours before trigger and 16.9 hours later than the limits reported in Ahumada et al. (GCN 25048). The observation consisted of a 12x60s exposure set in the GOTO L-band (400-700 nm).
Analysis at the location of the potential optical transient https://www.wis-tns.org/object/2023xvj (Kumar et al. GCN 35041) does not show evidence of the source to a 3-sigma limiting AB magnitude of L > 20.1.
Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed manually on the stacked set using recent survey observations of the same pointings.
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.
Further observations are scheduled during the coming nights.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).
GCN Circular #35051
A. Iskandar (XAO), F. Wang (THU/BJP), J. Zhu (BJP), L. Wang, X. Zeng, C. An= drade (UMN), A. de Ugarte Postigo (CNRS/OCA), D. Akl (AUS), E. Broens (KNC)= , S. Antier (OCA-Artemis), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), = D. Turpin (CEA-Saclay/Irfu), T. Pradier (Unistra/IPHC), M. Coughlin (UMN), = S. Karpov (FZU), J. Peloton (IJCLab) report on behalf of the GRANDMA collab= oration:
We observed the field of GRB 231115A (Fermi GBM team, GCN 35035) covering t= he complete INTEGRAL error box (D=E2=80=99Avanzo et al. GCN 35036;Mereghett= i et al. GCN 35037) within the GRANDMA collaboration. Imaging with the 0.4m= SNOVA telescope did not find any candidate in r-band around 2023-11-15 17:= 37:53 (e.g 2h after the trigger time) down to an upper limit of 18.9 (5-sig= ma threshold) or 19.3 (3-sigma threshold) using PS1 catalog as photometric = comparison. We also looked carefully at the location of AT 2023xvj (Kumar e= t al. GCN 35041).
The amateur contribution to GRANDMA, Kilonova Catcher (KNC), made no detect= ion with a 30x180s image using a clear filter on 2023-11-15T20:00 UTC (TGRB + 3.28h). We determine a detection limit of 20 mag in r-band, using PS1 fo= r calibration and color term correction. At 2023-11-15T18:53:25.219, we obt= ained R>18 from 5x180s exposure. The upper limit is given at 5-sigma averag= ed over all the images.
These upper limits are consistent with previous reports by MASTER (Lipunov et al. GCN 35046).
GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophy= sics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the ci= tizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).
GCN Circular #35052
T.-W. Chen, C.-S. Lin (both NCUIA), A.J. Levan (Radboud), S. Schulze (CIERA= , NW), M. Fraser (UCD), P. D'Avanzo (INAF - OAB), J. Lyman (Warwick), Y.-C. Cheng, C.-H. Wang (both NTNU), S. Yang (HNAS), M.-H. Lee, Y.-C. Pan, C.-C. Ngeow, H.-Y. Hsiao, W.-J. Hou, J.-K. Guo (all NCUIA), M. Fulton, S. Srivas= tav, T. Moore, C. Angus, A. Aamer (all QUB) and S. Smartt (Oxford/QUB) report:
We observed the field of GRB 231115A, a short GRB discovered by the Fermi G= BM (Fermi GBM Team, GCN 35035). The GRB position is consistent with M 82 ga= laxy (D=E2=80=99Avanzo et al., GCN 35036). This burst is also detected by I= BAS (Mereghetti et al., GCN 35037), INTEGRAL (Burns, GCN 35038) and Glowbug on the ISS (Cheung et al., GCN 35045). The GROWTH-India discovery of a pot= ential optical counterpart AT 2023xvj with r~19.2 (Kumar et al., GCN 35041), taken on 1.19 hours after the Fermi trigger.
We used the 40cm SLT at Lulin Observatory, Taiwan to obtain r, i and z-band images of the field of M82, as part of the Kinder collaboration (Chen et al., AstroNote 2021-92). The first SLT epoch of observations started at 16:46 UT on 15 of November 2= 023 (MJD =3D 60263.699), 1.15 hours after the Fermi GBM trigger. The images= were combined from 7 frames with a 300-second exposure time for the r band= , taken under seeing conditions of an average of 1.6" and at a median airma= ss of 2.14. We then took i-band images for 15 frames started at 18:56 UT, e= ach with 300-second exposure time, taken under seeing conditions of an aver= age of 2.2" and at a median airmass of 1.58. Finally, starting at 20:10 UT = we observed z-band images for 13 frames, each with 300-second exposure time= , taken under seeing conditions of an average of 2.0" and at a median airma= ss of 1.49.
We used the Kinder pipeline (Yang et al. A&A 646, A22) to measure the 3-sig= ma limits on the source location. We obtained the following preliminary mag= nitudes (in the AB system):
```
r > 19.23 mag,
i > 19.48 mag and,
z > 18.53 mag.
```
The given limit is derived based on calibrating against Pan-STARRS1 field s= tars and is not corrected for the expected Galactic foreground extinction c= orresponding to a reddening of E_(B-V) =3D 0.14 mag in the direction of the= burst (Schlafly & Finkbeiner 2011).
We do not see the source AT 2023xvj in the combined r, i and z-band images, nor in a subtraction against images obtained from the Legacy survey. However, the relatively poor conditions combined with high underlying surface brightness from the galaxy substantially reduce our sensitivity, and we would at best have marginally detected the transient identified by Kumar et al. (GCN 35041).
GCN Circular #35053
The IceCube Collaboration (http://icecube.wisc.edu/) reports:
IceCube has performed a search for track-like muon neutrino events arriving from the direction of GRB 231115A (GCN Circ. 35035<https://gcn.nasa.gov/circulars/35035> (Fermi-GBM), INTEGRAL GCN Notice 10427), a likely magnetar giant flare in M82 (D'Avanzo et al., GCN Circ. 35036; Mereghetti et al., GCN Circ 35037; Burns, GCN Circ 35038).
We searched a time window off +/- 2000 seconds from the initial trigger reported by INTEGRAL (23/11/15 15:36:22.88 UT), during which IceCube was collecting good quality data. We used the offline direction reported by INTEGRAL (INTEGRAL GCN Notice 10427<https://gcn.gsfc.nasa.gov/other/10427.integral>). Zero track-like events are found in coincidence with the position of the GRB. We accordingly derive a time-integrated muon-neutrino flux upper limit for this source of E^2 dN/ dE = 7.6*10^-2 GeV cm^-2 at 90% CL, under the assumption of an E^-2 power-law spectrum. 90% of events IceCube would detect from a source at this declination with an E^-2 spectrum have energies in the approximate energy range between 500 GeV and 130 TeV.
The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc@icecube.wisc.edu.
[1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021)
GCN Circular #35054
A.K.H. Kong (NTHU), K.-L. Li (NCKU) report:
Following the discovery of GRB 231115A (GCN 35035) in the direction of M82 and its optical counterpart candidate AT 2023xvj (GCN 35041), we searched for X-ray emission from the progenitor with the Chandra X-ray Observatory. Chandra observed M82 with the ACIS detector 32 times between 2000 and 2016, with a total exposure time of about 561 ks. We combined all the observations and no source is visible at the position of the optical transient. We derive a 3-sigma luminosity limit of 2.3e37 erg/s (0.3-10 keV; D=3.5 Mpc) by assuming an absorbed power-law model with a photon index of 2.
GCN Circular #35055
R. Kumar (IIT Bombay), V. Karambelkar (Caltech), V. Swain, V. Bhalerao, A. Salgundi, Y. Wagh (IIT Bombay), G. C. Anupama, S. Barway (IIA), R. Norboo (IAO), T. Ahumada, M. M. Kasliwal (Caltech) report on behalf of a larger collaboration
We undertook refined analysis of GIT231115AA / AT2023xvj (Kumar et al, GCN 35041). The source is detected in 25 individual r-band images obtained by GIT (https://sites.google.com/view/growthindia/results/at2023xvj), as well as in a stacked image.
We investigated the reference images from PanSTARRS used for image subtraction and find a small, fuzzy, "negative" artifact at the location of the source (see link above), which may boost the counts at the source location. This had been considered in the original report, and excluded due to three reasons: first, the measured source flux is varying despite fixed exposure times, which makes it unlikely that they are all caused due to the same artifact. Second, there are similar artifacts at other locations in the reference images which do not create such bright spurious sources. Third, the source shows a PSF-like profile while the reference image artifact does not.
Other groups have reported non-detections which are broadly consistent with our detection: Balanutsa et al, (GCN 35046) report an upper limit of 21.3 which is comparable to our image sensitivity of 21.45 (5-sigma). However, the candidate is in a high background region which will result in shallower upper limits. Upper limits reported by Iskandar et al (GCN 35051 - 18.9 mag), and Chen et al (GCN 35052 - 19.2 mag) are consistent with our measurement.
Given the complex nature of background in the M82 field and the potential artifact, we undertook manual image subtraction using SDSS images as a reference. In this scenario, the subtraction is noisier, and we do not detect any source at the location of GIT231115AA / AT2023xvj, to a limiting magnitude of 19.3 (5-sigma).
Given this analysis, we caution observers that AT2023xvj be treated as a candidate, not a secure counterpart.
GCN Circular #35056
S.Q. Jiang, X. Liu, S.Y. Fu, J. An, Z.P. Zhu, T.H. Lu, D. Xu (NAOC), L.F. Huo, S.W. Luo, M.M. Yang, Z. K. Feng (GYZO) report:
We observed the field of GRB 231115A, a short GRB detected by the Fermi GBM (Fermi GBM Team, GCN 35035), INTEGRAL (Mereghetti et al., GCN 35037), and Glowbug (Cheung et al., GCN 35045), using the GOT-0.5m telescope located at Gaoyazi, Xinjiang, China. Observations started at 16:36:59 UT on 2023-11-15, i.e., 1.01 hr after the Fermi/GBM trigger, and we obtained 40x60 s frames in the Sloan r-filter and 40x90 s frames in the Sloan z-filter.
No credible optical transient is detected in our stacked images within and beside the error region of the INTEGRAL by the means of catalogue cross-match and image subtraction, down to 3-sigma limiting magnitudes of r>20.1 @ 1.38 hr and z>18.0 @ 2.86 hr post-burst, calibrated with nearby PanSTARRS stars. The magnitude is not corrected for Galactic extinction.
The field is also covered by the GW survey program at the GOT. The latest template was taken on 2023-10-05 and it gives upper limit down to r>18.8 within the INTEGRAL/IBAS error region.
GCN Circular #35057
S. Hayatsu, N. Higuchi, I. Takahashi, M. Sasada (Tokyo Tech), K. L. Murata (Kyoto U), M. Niwano, S. Sato, H. Seki, H. Takei, Y. Yatsu and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We observed a field of GRB 231115A ( Fermi GBM Team GCN Circular #35035) with optical three-color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescopes Akeno and Okayama.
The observation started at 2023-11-15 17:17:29 UT (6068 seconds after the Fermi/GBM trigger). We stacked the images with good conditions. We did not detect any obvious point sources at the position reported by Kumar et al. GCN Circular #35041. We obtained the 5-sigma limits of the stacked images as follows.
```
T0+[sec] | MID-UT | T-EXP[sec] | 5-sigma limits
------------------------------------------------------------------------------------------------
# MITSuME Akeno
6482 | 2023-11-15 17:24:23 | 600.0 | g'>19.6, Rc>19.5, Ic>19.0
7527 | 2023-11-15 17:41:48 | 1200.0 | g'>20.0, Rc>19.8, Ic>19.3
9612 | 2023-11-15 18:16:33 | 2400.0 | g'>20.4, Rc>20.2, Ic>19.7
# MITSuME Okayama
12526 | 2023-11-15 19:05:07 | 7380.0 | g'>19.1, Rc>19.9, Ic>19.2
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
```
We used the PS1 catalog for flux calibration. The catalog magnitudes in PS1 g, r and i bands were converted to our g', Rc and Ic band magnitudes following Tonry et al. (2012), Table 6. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages 4-24; https://github.com/MNiwano/Eclaire).
GCN Circular #35059
P. Minaev (IKI), A. Pozanenko (IKI) report on behalf of GRB IKI FuN:
We analyzed GRB 231115A, detected till now by GBM/Fermi (GCN 35035, GCN 350= 44) and INTEGRAL (GCN 35037), Glowbug (GCN 35045), using publicly available= data of GBM/Fermi. The light curve of the burst is FRED-like with duration= of T_90 =3D 0.06 +/- 0.01 s in (7, 850) keV energy range. The spectral ana= lysis in a time interval of (-0.05, 0.05) s since GBM trigger, the best fit= is obtained for CPL model with following parameters: E_p =3D 613 (- 60, +7= 4) keV, alpha =3D 0.33 +/- 0.21. The fluence of F =3D (7.2 +/- 0.5)E-7 erg/= cm**2 is obtained in 10 - 1000 keV energy band, Eiso =3D (1.24 +/- 0.14)E45= erg in (1, 10000) keV energy range for D_L =3D 3.5 Mpc of M82. Using Ep,i = =E2=80=93 Eiso correlation and T_90,i - EH diagram [1,2] we classify the bu= rst as the SGR giant flare. Taking into account the non-detection of gravit= ational waves with LIGO/Virgo/KAGRA (LIGO Scientific Collaboration, Virgo C= ollaboration, KAGRA Collaboration, GCN 35049) we can suggest the GRB 231115= A as the giant flash of a new SG! R in M82 galaxy.
Ep,i =E2=80=93 Eiso correlation can be found at http://grb.rssi.ru/GRB231115A/GRB231115A_Ep-Eiso.png
T_90,i - EH diagram can be found at http://grb.rssi.ru/GRB231115A/GRB231115A_EHD.png
```
[1] - Minaev et al., MNRAS, 492, 1919, 2020=20
[2] - Minaev et al., Astronomy Letters, 46, 9, 573, 2020
```
GCN Circular #35060
W. C. Xue, S. L. Xiong, X. B. Li and C. K. Li report on behalf of the Insight-HXMT team:
At 2023-11-15T15:36:21.200 (T0), Insight-HXMT/HE detected GRB 231115A (trigger ID: HEB231115650) in a routine search of the data, which was also observed by Fermi/GBM (Fermi GBM Team, GCN 35035 & 35044), INTEGRAL (P. D'Avanzo et al., GCN 35036, S. Mereghetti et al. GCN 35037) and Glowbug (C. C. Cheung et al., GCN 35045). This burst is probably a giant flare from a magnetar in the nearby galaxy M82.
The Insight-HXMT/HE light curve mainly consists of single pulse with a duration (T90) of 0.08 s measured from T0-0.01 s. The 1-ms peak rate, measured from T0-0.01 s, is 16611 cnts/sec. The total counts from this burst is 210 counts. URL_LC: https://twikinew.ihep.ac.cn/pubhxmt/HXMT/GRBList/HEB231115650_lc.jpg
All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 80-800 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside the telescope.
Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org.
GCN Circular #35061
C. Pittori, F. Verrecchia (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), C. Casentini, L. Foffano (INAF/IAPS), G. Piano (INAF/IAPS), A. Ursi (ASI and INAF/IAPS), L. Baroncelli, A. Bulgarelli, A. Ciabattoni, A. Di Piano, V. Fioretti, G. Panebianco, N. Parmiggiani (INAF/OAS-Bologna), M. Pilia (INAF/OA-Cagliari), P.W. Cattaneo (INFN Pavia), F. Cutrona (Univ. Milano Bicocca), F. Longo (Univ. Trieste, and INFN Trieste), report on behalf of the AGILE Team:
AGILE observed the short GRB 231115A first reported by Fermi GBM at T0 =3D 15:36:21 UT on 15 Nov 2023 (GCN #35035) and significantly localized by INTEGRAL in M82 (GCN #35036, #35037, #35038), suggesting a possible magnetar giant flare origin (also GCN #35044).
The GRB location was fully accessible to the AGILE MCAL at about 70 degrees off-axis, but no trigger occured around +/- 50 sec from T0.
The three-sigma upper limit (UL) obtained for a 1 s integration time at=C2=A0 the GRB position is 1.3E-06 erg cm^-2 (assuming as spectral model = a single power law with photon index 1.5).
The AGILE-MCAL detector is a CsI detector with a 4 pi FoV, sensitive in the energy range 0.4-100 MeV. Additional analysis of AGILE data is in progress.
GCN Circular #35062
FROM: Dmitry Frederiks at Ioffe Institute
D. Frederiks, D. Svinkin, A.Lysenko, A. Ridnaia, Yu. Temiraev, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
The short duration, hard spectrum GRB 231115A (Fermi GBM detection: Fermi GBM team GCN 35035, Dalessi et al. GCN 35044; INTEGRAL (IBAS) detection: Mereghetti et al., GCN 35037; Glowbug detection: Cheung et al., GCN 35045) triggered Konus-Wind (KW) at T0=3D 56183.509 s UT (15:36:23.509).
The burst light curve shows a single FRED-like pulse, which starts, at ~T0-0.028 s with the fast (<4 ms) rise of the emission intensity, which peaks at ~T0-0.016 s and has a total duration of ~66 ms.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB231115_T56183/
As observed by Konus-Wind, the burst had a fluence of (7.3 =C2=B1 0.1)x10^-7 erg/cm^2 and a 16-ms peak energy flux, measured from T0 - 0.018 s, of (2.2 =C2=B1 0.45)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy r= ange).
The time-integrated spectrum (measured from T0-0.028 s to T0+0.036 s) is best fit in the 20 keV - 1.5 MeV range by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha =3D 0.69(-0.54,+0.96) and Ep =3D 495(-77,+118) keV. A blackbody (BB) spectral model fits the spectrum equally well, with the BB temperature kT =3D 114(-10,+9) keV.
Assuming the likely GRB 231115A association with the nearby M82 galaxy at ~3.5 Mpc (D=E2=80=99Avanzo et al., GCN 35036; Mereghetti et al., GCN 35037; Burns GCN 35038), we estimate the burst isotropic energy Eiso to ~1.1x10^45 erg and the 16-ms peak luminosity Liso to ~3.2x10^46 erg/s. These values are in the range the of the energetics of initial pulses of magnetar giant flares (MGFs), which, assuming the short rise time and the hard energy spectrum of the burst, supports its MGF origin.
At 3.5 Mpc, the characteristic radius of the emission region, estimated from the KW blackbody spectral fit, is R~30 km, the same order of magnitude as the radius of a neutron star or its magnetos= phere.
All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary.
GCN Circular #35064
J.P. Osborne (U. Leicester), B. Sbarufatti (INAF-OAB), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), J. D. Gropp (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans (U. Leicester) and S. R. Oates (Lancaster U.) report on behalf of the Swift-XRT and the Swift-UVOT teams:
Swift-XRT has performed follow-up observations of the INTEGRAL-detected burst GRB 231115A, which is likely not a GRB, but it is likely a MGF (Burns GCN Circular 35038) and whose position is consistent with M82 galaxy (D'Avanzo et al. GCN Circ. 35036; Mereghetti et al. GCN Circ. 35037), collecting 4.4 ks of Photon Counting (PC) mode data between T0+9.0 ks and T0+39.2 ks.
No uncatalogued X-ray sources have been detected consistent with being within 303 arcsec of the INTEGRAL position. The 3-sigma upper limit in the field ranges from ~0.002 to ~0.003 ct s^-1, corresponding to a 0.3-10 keV observed flux of 8.2e-14 to 1.2e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum).
Six previously-catalogued X-ray sources have been detected consistent with being within 303 arcsec of the INTEGRAL position, however their status as catalogued objects makes them unlikely to be the X-ray counterpart.
An uncatalogued object was detected, however this was too far from the GRB position to be the X-ray counterpart.
We note that the diffuse X-ray emission from the M82 galaxy affects a significant fraction of the INTEGRAL error circle. This likely reduces the sensitivity for source detection.
The results of the XRT-team automatic analysis of the XRT observations, including a position specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021625.
No optical counterpart consistent with the INTEGRAL position (Mereghetti et al., GCN Circ. 35037) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) are:
```
Filter	       T_start(s)   T_stop(s)	   Exp(s)	  Mag

w1		   9253       39224	    4283	>17.4
```
The magnitude in the table is not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.155 in the direction of the burst (Schlegel et al. 1998).
This circular is an official product of the Swift team.
GCN Circular #35065
Samuele Ronchini (PSU), Aaron Tohuvavohu (U Toronto), James DeLaunay (PSU), Gayathri Raman (PSU), Tyler Parsotan (NASA GSFC), Jamie A. Kennea (PSU) report:
Swift/BAT did not localize GRB 231115A onboard (T0: 2023-11-15T15:36:21.2 UTC, Fermi GCN 35035, Integral GCN 35037, Glowbug GCN 35045, Insight-HXMT/HE GCN 35060, Konus-Wind GCN 35062).
The Fermi and Integral notices, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).
Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground.
The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 20.26 in a 0.128 s analysis time bin, starting at T0.
NNITRATES results, independently, are ambiguous with respect to whether this burst originates from in or outside the BAT coded FOV, with a DeltaLLHOut of 8.9. The Integral localization, coincident with M82, is consistent with being outside the BAT coded FOV.
The very short duration and the large E_peak (best fit value from the spectral template of 720 keV) are consistent with the Magnetar Giant Flare scenario (GCN 35044, GCN 35059).
See Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief descriptions and interpretation of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut.
GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches.
A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/
GCN Circular #35066
B. Grefenstette and M. Brightman (Caltech) for the NuSTAR Team
NuSTAR performed follow-up observations of GRB 231115A / magnetar giant flare (Burns GCN Circular 35038) in the direction of M82 (D'Avanzo et al. GCN Circ. 35036; Mereghetti et al. GCN Circ. 35037). The NuSTAR observation was centered on the potential optical counterpart location from GROWTH India (Kumar et al. GCN Circ 35041, Kumar et al., GCN Circ 35055).
NuSTAR began observing at 2023-11-15T22:21:09, only ~four hours after the ToO trigger was approved. We report on the first ~40-ks of data.
M82 has a number of bright point sources as well as extended emission that is unresolved by the NuSTAR PSF (see, e.g., Brightman et al 2020 ApJ 889 71, DOI:10.3847/1538-4357/ab629a). The NuSTR observation does not reveal any significant point sources outside of the central ~1-arcmin region of M82. No significant emission from the location of optical transient AT2023xvj at RA = 09:56:00.2, Dec = 69:40:29.2 (RA=149.000,Dec=+69.675) is seen, though this overlaps with the wings of the NuSTAR PSF from the central emission from M82 as well as extended emission in the galaxy. These observations are on-going.
The NuSTAR SINGS pipeline did not trigger on the GRB 231115A transient. We performed an off-line analysis of the NuSTAR shield data and the count rates from the X-ray detectors and do not see the transient in either set of data. This is unsurprising, as the NuSTAR CsI shield data are only stored at 1-Hz and short signals such as from this GRB are difficult to identify. The source was ~80 degrees from the Earth horizon and ~35-deg from the instrument boresight, which may also have been an unfavorable geometry for detecting the source in the CdZnTe detectors.
GCN Circular #35067
D. A. Perley (LJMU), K.-R. Hinds (LJMU), J. Wise (LJMU), V. Karambelkar (Caltech), T. F. Ahumada (Caltech), and M. M. Kasliwal, (Caltech) report:
We obtained optical imaging of M82, the potential host of GRB 231115A (Fermi GBM Team, GCN 35035; Mereghetti et al., GCN 35037), using the IO:O imager on the 2m Liverpool Telescope. Two exposures of 195s each were taken in the g, r, i, and z filters between 03:45 and 04:14 on 2023-11-16 (UT), approximately 0.5 days after the GRB. Conditions were generally good throughout.
We performed image subtraction of the g-band and z-band images using Pan-STARRS 1 survey images as a reference. The PS1 r-band and i-band images show artifacts at the location of the potential optical source AT2023xfj reported by Kumar et al. (GCN 35041) and were unsuitable (see also Kumar et al., GCN 35055), so references were taken from the Sloan Digital Sky Survey for these filters instead.
We do not detect a source at the location of AT2023xfj, to approximate limits (3-sigma) of g>21.9, r>21.6, i>21.7, z>21.0 mag (AB). There are no other candidate transients detected in the difference image consistent with the disk of M82, with the possible exception of a red source at RA=09:55:53.079, +69:40:23.28 (J2000). However, this source is also visible as a point source in the reference images, suggesting it may be a foreground variable. The effective limiting magnitude of the subtraction is significantly shallower in the innermost regions of M82 due to the variable background.
GCN Circular #35068
The MAGIC telescopes observed GRB 231115A (RA:09:56:00.22, Dec:+69:40:48.00= ), a candidate Magnetar Giant Flare from M82 (GCN 35044) after the alert i= ssued by INTEGRAL (GCN/INTEGRAL NOTICE 10427). The observations in the very= -high-energy (VHE; >100 GeV) range were performed on the night of November = 15th starting at ~T0+8h, for about 2 hours, at large zenith angles. The f= ast and preliminary analysis does not show any significant detection (<2 si= gma) above 250 GeV. The preliminary integral flux upper limit (95% confide= nce level) at 300 GeV is 8e-12 cm-2 s-1.
The contact persons for the MAGIC collaboration are Alicia L=C3=B3pez-Orama= s (alicia.lopez@iac.es), Alessandra Lamastra (alessandra.lamastra@inaf.it) = and Giuseppe Silvestri (giuseppe.silvestri@studenti.unipd.it). MAGIC is a = system of two 17m-diameter Imaging Atmospheric Cherenkov Telescopes located= at the Observatory Roque de Los Muchachos of the Instituto de Astrof=C3=AD= =C2=ADsica de Canarias (IAC) on the Canary island of La Palma, Spain (https= ://magic.mpp.mpg.de).
GCN Circular #35070
Alice P. Curtin (McGill University) for the CHIME/FRB Collaboration:
At 15:36:21 UTC on 15 November 2023, GRB 231115A was detected by Fermi/GBM (Fermi GBM Team, GCN 35035 & 35044), INTEGRAL (P. D'Avanzo et al., GCN 35036, S. Mereghetti et al., GCN 35037), Glowbug (C. C. Cheung et al., GCN 35045), and Insight-HXMT (Insight-HXMT team, GCN 35060). The position of GRB 231115A (RA=149.00, DEC=69.68 with an uncertainty of 2 arcmin) is consistent with that of the M82 galaxy (S. Mereghetti et al. GCN 35037). Additionally, the spectrotemporal properties of GRB 231115A suggest it is likely due to a magnetar giant flare (Fermi/GBM Team, GCN 35044, S. Ronchini et al., GCN 35065).
At the time of the high-energy (HE) emission, GRB 231115A was ~20 degrees from the meridian of the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project (CHIME/FRB). No radio emission was detected from the source at the time of the HE emission. In addition to searching for radio emission at the time of the Fermi/GBM trigger, we also searched within the CHIME/FRB database for bursts from this position within the last two years, yet did not find any definitive astrophysical associations.
Using a pipeline described in Curtin et al. (2023), we constrain the FRB-like radio emission from this source in the 400-800 MHz band to be <260 Jy or <720 Jy ms (assuming a 10 ms pulse width) at the time of the Fermi/GBM trigger. The HE fluence reported by Fermi/GBM in the 10-1000 keV range is (6.3 +/- 0.4)e-7 erg/cm^2 (Fermi/GBM Team, GCN 35044). This implies a radio-to-HE emission ratio of <4.5e-9 (unitless assuming a 400 MHz bandwidth). Additionally, using a luminosity distance of 3.5 Mpc to the M82 galaxy (P. D'Avanzo et al. 2023, GCN 35036), our derived radio flux limit corresponds to an upper limit on the radio luminosity of <3.8e30 erg s^-1 Hz^-1.
While GRB 231115A was ~20 degrees from the meridian of CHIME/FRB at the time of the Fermi/GBM trigger, it transited directly overhead CHIME/FRB at 14:18:45 UTC on 15 November 2023. Thus, our best radio constraints for this source are ~80 minutes prior to the Fermi/GBM trigger. As no radio emission was similarly detected at this time, we constrain the radio flux at this time to be <0.5 Jy and the fluence to be <1.2 Jy ms assuming a burst width of 10 ms. This corresponds to a radio luminosity limit of <7.3e27 erg s^-1 Hz^-1 and a radio-to-HE fluence ratio of <7.6e-12 (unitless assuming a 400 MHz bandwidth).
References
Curtin, A.P., Tendulkar, S.P., Josephy, A., et al., 2023, ApJ, 954, 154. doi:10.3847/1538-4357/ace52f
GCN Circular #35077
P. D'Avanzo (INAF-OAB), A. Reguitti (INAF-OAB / INAF-OAPd), L. Tomasella (INAF-OAPd), E. Cappellaro (INAF-OAPd), M. T. Botticella (INAF-OAC), F. Onori (INAF-OAAb), L. Tartaglia (INAF-OAAb), F. De Luise (INAF OAAB), M. G. Bernardini (INAF-OAB), S. Campana (INAF-OAB), S. Covino (INAF-OAB), V. D'Elia (ASI/SSDC & INAF/OAR), M . De Pasquale (Univ. of Messina), D. B. Malesani (DAWN/NBI & Radboud Univ.), E. Palazzi (INAF-OAS), A. Rossi (INAF-OAS), R. Salvaterra (INAF-IASF Mi), G. Tagliaferri (INAF-OAB), A. Melandri (INAF-OAR), E. Brocato (INAF-OAAb), M. Pedani, C. P. Padilla-Torres (INAF/TNG) report on behalf ot the CIBO and of the GRAWITA collaborations:
We carried out follow-up optical observations of the high-energy event detected by Fermi/GBM, INTEGRAL, Glowbug, Insight-HMXT/HE, Konus-Wind, Swift/BAT on 2023-11-15 at 15:36:21 UT, initially classified as the short/hard GRB 231115A and subsequently as a likely magnetar giant flare located in the M82 galaxy (Fermi GBM team, GCN Circ. 35035; D'Avanzo et al., GCN Circ. 35036; Mereghetti et al., GCN Circ. 35037; Dalessi et al., GCN Circ. 35044; Cheung et al., GCN Circ. 35045; Xue et al. GCN Circ. 35060; Frederiks et al., GCN Circ. 35062; Ronchini et al., GCN Circ. 35065).
Observations from the INAF - Padova Astronomical Observatory located in Asiago (Italy) have been carried out with the Schmidt telescope starting on 2023-11-15 at 20:40:03 UT (~ 5 hours after the event T0) with the g, r and i filters. Preliminary analysis, which includes image subtraction with SDSS templates, does not show evidence for promising candidate counterparts within the INTEGRAL error circle (Mereghetti et al., GCN Circ. 35037). The typical 3sigma limiting AB magnitudes at the position of the candidate counterpart AT2023xfj (Kumar et al., GCN Circ. 35041 and 35055) are g ~ 19.5 mag, r ~ 18.4 mag and i ~ 20.3 mag.
Observations the from INAF - Abruzzo Astronomical Observatory located in Campo Imperatore (Italy) have been carried out starting on 2023-11-15 at 21:38:00 UT (~ 6 hours after the event T0) with the g, i and z filters. Preliminary analysis, which includes image subtraction with SDSS templates, does not show evidence for promising candidate counterparts within the INTEGRAL error circle. The typical 3sigma limiting AB magnitudes at the position of the candidate counterpart AT2023xfj are g ~ 18.7 mag, i ~ 17.2 mag and z ~ 17.2 mag.
Observations the from INAF - TNG located in Canary Islands (Spain) have have been carried out starting on 2023-11-16 at 03:27:28 UT (~ 12 hours after the event T0) with the r, i and z filters. Preliminary analysis, which includes image subtraction with SDSS and archival TNG templates, does not show evidence for promising candidate counterparts within the INTEGRAL error circle. The typical 3sigma limiting AB magnitude at the position of the candidate counterpart AT2023xfj in the r filter is of ~ 22.0 mag.
GCN Circular #35078
D. Turpin (CEA Paris-Saclay), W. Thuillot (Obs. Paris/IMCCE), D. Souami (Obs. Paris/LESIA), C. Adami (LAM), E. Le Floc'h, D. G=C3=B6tz, F. Sch=C3=BCssler (CEA Paris-Saclay), A. de Ugarte Postigo (OCA/CNRS), S. Basa (Pytheas/OHP/LAM), S. D. Vergani (GEPI, Obs. de Paris), report on behalf of a larger collaboration:
We observed the field of GRB 231115A, likely a Giant flare from a magnetar in M82 (Fermi GBM Team, GCN 35035; Mereghetti et al., GCN 35037, Dalessi et al. GCN 35044, Cheung et al. GCN 35045, Xue et al., GCN 35060, Frederiks et al. GCN 35062) using the T120cm telescope at Observatoire de Haute-Provence (France). We began our observations of the M82 field on 2023 15 November 22:57:23.78 (~7.35h after the INTEGRAL trigger time) with a series of R-band (1400s), V-band (600s) and sdss-i (300s) images. The limiting magnitudes of our images are R> 21.1, V>20.9 and i>19.2 but are strongly reduced in the vicinity of M82 due to its bright diffuse background light.
After inspecting our residual images from the subtraction of both the PS1 catalog images and our archival own M82 images, we do not detect any new source inside the INTEGRAL localization. We also do not detect any credible counterpart at the location of the transient candidate reported by Kumar et al. GCN 35041.
The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitude is not corrected for Galactic extinction.
We acknowledge the excellent support from Observatoire de Haute-Provence.
GCN Circular #35091
J. An, S.Q. Jiang, X. Liu, S.Y. Fu, Z.P. Zhu, T.H. Lu, D. Xu (NAOC), J.Z. Liu (XAO) report on behalf of a large collaboration:
We observed the field of GRB 231115A detected by the Fermi GBM (Fermi GBM Team, GCN 35035), INTEGRAL (Mereghetti et al., GCN 35037), and Glowbug (Cheung et al., GCN 35045), using two 50cm telescopes (50A, 50B) located at Altay, Xinjiang, China. Observations started at 17:30:51 UT on 2023-11-15, i.e., 1.91 hr after the Fermi/GBM trigger, in the Sloan g-/r-/i-/z- bands.
No credible optical transient is detected in our stacked images within and beside the error region of the INTEGRAL. Preliminary results are as follows:
```
-----------------------------------------------------------------
              Tmid(UT)      exp(s)   filter      UL(3-sigma)
-----------------------------------------------------------------
2023-11-15T17:47:17  60sx30      g           20.4
2023-11-15T18:20:18  60sx30      r            20.3
2023-11-15T18:34:16  30sx60      i            18.1
2023-11-15T17:54:39  30sx66      z           16.0
-----------------------------------------------------------------
```
calibrated with nearby PanSTARRS stars. The magnitude is not corrected for Galactic extinction. The z-band upper limit is shallower than expected due to a technical issue.
Altay Astronomical Time-Domain Project (JinShan Project for short) consists of four 50cm telescopes with FOV of 1.7x1.7 deg^2 for each (50A, 50B, 50C, and 50D), two 100cm telescopes with FOV of 1.4x1.4 deg^2 for each (100A and 100B), and one 100cm telescope with FOV of 14x14 arcmin^2 (100C). Each telescope is equipped with different filters. JinShan is now at its early commissioning stage.
GCN Circular #35092
Lei Hu (CMU), Malte Busman (LMU), Daniel Gruen (LMU), Antonella Palmese (C= MU), Brendan O=E2=80=99Connor (CMU), Arno Riffeser (LMU/MPE), Ananya Shanka= r (LMU), Raphael Zoeller (LMU) report:
We observed the position of GRB 231115A (Fermi GBM team, GCN 35035) with th= e 2m Fraunhofer telescope at Wendelstein Observatory, Germany. Observations= were obtained using the 3kk imager in the r, i, and J bands simultaneously= , and then in r, i, and H bands. Observations started on 2023-11-16 at 00:3= 9 UT with a total exposure time of 7200 seconds in r and i, and 3600 second= s in J, H.
We performed difference imaging in r band with deep archival Wendelstein Wi= de Field Imager observations of M82 using the SFFT pipeline (Hu et al. 2022= ). We do not detect any source at the location of GIT231115AA / AT2023xvj (= Kumar et al, GCN 35041) to depth r> 22.5 (5sigma depth). We identify 2 new = sources:
```
Name | RA (J2000 deg) | dec (J2000 deg) | r (AB mag)
----------------------
W231115a | 148.9711390 | 69.6730597 | 20.54 +/- 0.04
W231115b | 148.9950500 | 69.6912555 | 21.26 +/- 0.08=20
```
W231115a is also detected in i, J, and H, while W231115b is only detected i= n r and i. We cannot exclude that these are variable objects associated wit= h previously detected sources in archival HST data. Further analysis is und= erway.
The magnitudes are not corrected for Milky Way extinction and the photometry was calibrated against nearby stars in the PS1 and 2MASS catalogs. We thank the staff of the Wendelstein Observatory for obtaining these observations.
GCN Circular #35115
Y. Kawakubo (LSU), A. Yoshida, T. Sakamoto, S. Sugita (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration:
The CALET Gamma-ray Burst Monitor (CGBM) was operating at the trigger time of the short GRB 231115A T0 = 2023-11-15 15:36:21.20 UT (Fermi GCN: #35035, #35044; Integral GCN: #35037; Glowbug GCN #35045; Insight-HXMT/HE GCN #35060; Konus-Wind GCN #35062; Swift-BAT GCN #35065).
No CGBM onboard trigger occurred around T0. Based on the IBAS localization, the incident angles to HXM and SGM are 79 degrees and 85 degrees, respectively (#35037). Based on the analysis of the light curve data with 0.125 sec time resolution, we found a hint of the burst emission around the trigger time in HXM2 and SGM data. However, the significance of 4.8 (HXM2) and 4.7 (SGM) sigma is below our detection criterion to the CGBM data.
The five sigma upper limit of SGM for a 0.125 integration time is 3.0e-6 erg/cm^2/s (10 - 1000 keV), assuming a power-law with an exponential cutoff (alpha = 0.5, Epeak = 580 keV, reference to #35044) and the IBAS position.
The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University.
GCN Circular #35175
M. Rigoselli, D. P. Pacholski, S. Mereghetti, R. Salvaterra (INAF, IASF-Milano) and S. Campana (INAF, OAB) on behalf of a larger collaboration report:
XMM-Newton carried out a target of opportunity observation of GRB 231115A (Mereghetti et al., GCN 35037; Fermi GBM Team, GCN 35035) which is likely a magnetar giant flare in the M82 galaxy (D=E2=80=99Avanzo et al., GCN 35036; Burns, GCN 35038) and was also detected by Glowbug (Cheung et al., GCN 35045), Insight-HXMT (Xue et al., GCN 35060), Konus-Wind (Frederiks et al. GCN 35062) and Swift/BAT (Ronchini et al., GCN 35065).
The burst location was observed with the EPIC instrument on 2023-11-16 from 08:27 UT to 21:19 UT (To+16.8 hr to To+29.7 hr). A large fraction of the ~46 ks long observation was affected by high background, resulting in cleaned exposure times of 8.4 ks for the pn camera and 19.0 and 23.6 ks for the MOS1 and MOS2 cameras, respectively.
Comparison of images in various energy ranges with those of the EPIC observations of M82 in 2021 and 2022, does not reveal any new source inside the INTEGRAL IBAS error circle (2 arcmin radius, Mereghetti et al., GCN 35037).
For about 50% of the error region, we derived a 3 sigma count rate upper limit of 0.004 pn cts/s in the 2-10 keV energy range. For an absorbed power law spectrum with photon index 2 and N_H=3D6.5E20 cm-2 this corresponds to about 3E-14 erg/cm2/s (2-10 keV).=20
Diffuse X-ray emission from the central part of M82 affects the error region, resulting in limits higher than 0.01 pn cts/s (2-10 keV) in less than 20% of the error region.
The lack of detection of an X-ray afterglow associated to GRB 231115A in the XMM-Newton observation 16.8 hours after the trigger provides further evidence that the burst is likely a magnetar giant flare in the M82 galaxy.
GCN Circular #35296
R. Strausbaugh (Eastern Illinois University), Daniel Warshofsky (UMN), Pat Kelly (UMN), Mandeep S. S. Gill (UMN), Alexandre Toscano (UMN), Yilin Lu(UMN), Sydney Leggio (UMN), Aksinya Kamenshikova (UMN) report on behalf of a larger collaboration:
We observed M82, including the localization region for the Fermi GRB 231115A (Fermi GBM team, GCN 35035), with the Total-Coverage Ultrafast Response to Binary-Mergers Observatory (TURBO) prototype telescope in St. Paul, Minnesota, USA, as part of a high-cadence ongoing survey for transients in nearby galaxies. We visited the field 55 times on November 15 UT, with the last visit occurring at 9:06 UT in SDSS r and g bands respectively (corresponding to 6.5 hours before the GRB trigger time).
Each exposure is 30 seconds. We do not detect a source at the same location as the GROWTH-India counterpart (Kumar et al., GCN 35041) in either band.
The 3-sigma upper limits in the table below are calculated using the Pan-STARRS catalog as reference, and are not corrected for Galactic extinction.
The TURBO prototype in St. Paul consists of two co-mounted 11-inch telescopes each with a 6.6 square degree field of view.
TURBO, which is under construction, will consist of two arrays of 8 pairs of co-mounted 11-inch telescopes at two dark-sky sites: Magdalena Ridge Observatory, New Mexico, USA and Skinakas Observatory, Crete, Greece.
mjd
g upper limit (AB)
r upper limit (AB)
60262.97035880
-
16.0
60262.97244213
16.9
-
60263.00063657408
-
15.9
60263.00407407407
-
15.7
60263.007106481484
-
16.1
60263.012094907404
-
15.6
60263.015555555554
-
15.9
60263.01940972222
-
16.0
60263.02327546296
-
15.9
60263.02715277778
-
16.3
60263.03057870371
-
16.1
60263.034212962964
-
16.1
60263.03765046296
-
16.4
60263.04111111111
-
15.7
60263.04293981481
-
15.8
60263.04591435185
16.5
15.7
60263.04896990741
-
16.4
60263.05202546297
16.5
15.8
60263.055
16.5
15.6
60263.058020833334
-
15.8
60263.061006944445
-
16.0
60263.06407407407
-
15.9
60263.070497685185
-
16.3
60263.07403935185
-
16.2
60263.07748842592
-
15.8
60263.080462962964
-
16.3
60263.08472222222
-
16.1
60263.087592592594
16.5
16.4
60263.09365740741
16.4
16.3
60263.09645833333
15.9
16.5
60263.099375
-
16.4
60263.1171412037
-
16.7
60263.120150462964
16.3
16.3
60263.12315972222
-
15.4
60263.14434027778
16.6
15.6
60263.14716435185
16.0
15.7
60263.15039351852
15.7
16.1
60263.15372685185
16.5
16.0
60263.156539351854
15.8
16.0
60263.159421296295
16.0
16.3
60263.162314814814
16.6
15.8
60263.165138888886
15.8
16.8
60263.16957175926
16.3
16.2
60263.172997685186
16.4
-
60263.176516203705
16.5
16.5
60263.19818287037
16.8
15.8
60263.21885416667
16.9
16.8
60263.22230324074
17.4
17.0
60263.24633101852
17.3
16.4
60263.268900462965
17.3
16.6
60263.27537037037
16.9
16.9
60263.27885416667
17.3
17.0
60263.283229166664
17.0
16.9
60263.28666666667
16.9
17.0
60263.29603009259
17.4
16.8

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Jochen Greiner, last update: 06-Dec-2023 [Disclaimer]