Gamma-ray Burst 231017A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 17 Oct 23 08:05:33 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      46
TRIGGER_NUM:     719222708
GRB_RA:           93.617d {+06h 14m 28s} (J2000),
                  94.114d {+06h 16m 27s} (current),
                  92.571d {+06h 10m 17s} (1950)
GRB_DEC:         +55.517d {+55d 31' 00"} (J2000),
                 +55.508d {+55d 30' 28"} (current),
                 +55.532d {+55d 31' 54"} (1950)
GRB_ERROR:       8.40 [deg radius, statistical plus systematic]
GRB_INTEN:       277 [cnts/sec]
DATA_SIGNIF:     13.30 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        20234 TJD;   290 DOY;   23/10/17
GRB_TIME:        29103.30 SOD {08:05:03.30} UT
GRB_PHI:         112.00 [deg]
GRB_THETA:        55.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      0.85
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      95%  GRB
2nd_MOST_LIKELY:   2%  GRO_J0422_32
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 1,1,0, 0,0,
SUN_POSTN:       201.93d {+13h 27m 44s}   -9.20d {-09d 11' 49"}
SUN_DIST:        107.63 [deg]   Sun_angle= 7.2 [hr] (West of Sun)
MOON_POSTN:      230.89d {+15h 23m 33s}  -21.19d {-21d 11' 23"}
MOON_DIST:       133.05 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      158.72, 17.15 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       92.42, 32.11 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231017337/quicklook/glg_lc_medres34_bn231017337.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 320.98,12.20 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 17 Oct 23 08:05:51 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      58
TRIGGER_NUM:     719222708
GRB_RA:           84.480d {+05h 37m 55s} (J2000),
                  84.983d {+05h 39m 56s} (current),
                  83.425d {+05h 33m 42s} (1950)
GRB_DEC:         +56.280d {+56d 16' 48"} (J2000),
                 +56.292d {+56d 17' 32"} (current),
                 +56.251d {+56d 15' 02"} (1950)
GRB_ERROR:       5.82 [deg radius, statistical only]
DATA_SIGNIF:     16.40 [sigma]
DATA_INTERVAL:   2.048 [sec]
GRB_DATE:        20234 TJD;   290 DOY;   23/10/17
GRB_TIME:        29103.30 SOD {08:05:03.30} UT
GRB_PHI:         117.00 [deg]
GRB_THETA:        58.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       201.93d {+13h 27m 44s}   -9.20d {-09d 11' 49"}
SUN_DIST:        112.41 [deg]   Sun_angle= 7.8 [hr] (West of Sun)
MOON_POSTN:      230.89d {+15h 23m 34s}  -21.19d {-21d 11' 26"}
MOON_DIST:       136.82 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      155.65, 12.91 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       86.35, 32.91 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231017337/quicklook/glg_lc_medres34_bn231017337.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_719222708.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
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.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 17 Oct 23 08:14:32 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     719222708
GRB_RA:           88.810d {+05h 55m 14s} (J2000),
                  89.320d {+05h 57m 17s} (current),
                  87.738d {+05h 50m 57s} (1950)
GRB_DEC:         +57.160d {+57d 09' 36"} (J2000),
                 +57.162d {+57d 09' 44"} (current),
                 +57.152d {+57d 09' 06"} (1950)
GRB_ERROR:       5.66 [deg radius, statistical only]
GRB_DATE:        20234 TJD;   290 DOY;   23/10/17
GRB_TIME:        29103.30 SOD {08:05:03.30} UT
GRB_PHI:         114.00 [deg]
GRB_THETA:        58.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       201.94d {+13h 27m 46s}   -9.20d {-09d 11' 57"}
SUN_DIST:        109.89 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:      230.97d {+15h 23m 53s}  -21.22d {-21d 12' 59"}
MOON_DIST:       134.47 [deg]
MOON_ILLUM:      7 [%]
GAL_COORDS:      156.01, 15.42 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       89.22, 33.72 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231017337/quicklook/glg_lc_medres34_bn231017337.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231017337/quicklook/glg_locplot_all_bn231017337.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:        This is likely a Long GRB.

GCN Circular #34822
The Fermi GBM team reports the detection of a likely Long GRB.
At 08:05:03.30 UT on 17 October 2023, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB231017A (trigger 719222708 / 231017337).
The on-ground calculated location, using the GBM trigger data, is RA = 88.8, DEC = 57.2 (J2000 degrees, equivalent to 5h 55m, 57d 09'), with a statistical uncertainty of 5.7 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).
The angle from the Fermi LAT boresight at the GBM trigger time is 58 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231017337/quicklook/glg_skymap_all_bn231017337.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/bn231017337/quicklook/glg_healpix_all_bn231017337.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn231017337/quicklook/glg_lc_medres34_bn231017337.gif
View this GCN Circular online at https://gcn.nasa.gov/circulars/34822.
GCN Circular #34824
FROM: Jimmy DeLaunay at University of Alabama
James DeLaunay (U Alabama, PSU), Aaron Tohuvavohu (U Toronto), Gayathri Ram= an (PSU), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC) report:
Swift/BAT did not localize GRB 231017A onboard (T0: 2023-10-17T08:05:03.30 = UTC, Fermi/GBM GCN 34822, Trigger 719222708).
The Fermi notice, distributed in near real-time, triggered the Swift Missio= n Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunit= ies (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).=20
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 burs= t with a sqrt(TS) of 15 in a 2.048 s analysis time bin, starting at T0 - 0.= 512 s.=20
A candidate arcminute localization is found with DeltaLLHOut of 17 and a De= ltaLLHPeak of 6.
See Section 9.1 and Figures 10 and 17 in the NITRATES paper for brief descr= iptions and interpretations of sqrt(TS), DeltaLLHPeak, and DeltaLLHOut.
The BAT position is RA, Dec =3D 86.191, +56.666 deg which is
```
   RA(J2000)  =3D 05 44m 45.84s
   Dec(J2000) =3D +56d 39=E2=80=B2 57.6=E2=80=B3
```
with an estimated uncertainty of 6 arcmin radius.
XRT and UVOT follow-up has been requested. Results of follow-up observations will be reported in future circulars.
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 #34825
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Swift/BAT-GUANO GRB 231017A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021623
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 Swift/BAT-GUANO 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 #34829
S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), A. Tohuvavohu (U. Toronto) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the Swift/BAT-GUANO-detected burst GRB 231017A (GCN Circ. 34824, DeLaunay et al.), collecting 4.2 ks of Photon Counting (PC) mode data between T0+32.7 ks and T0+101.7 ks.
One uncatalogued X-ray source has been detected consistent with being within 493 arcsec of the Swift/BAT-GUANO position, it is below the RASS limit and shows no definitive signs of fading. Therefore, at the present time we cannot confirm this as the afterglow. Details of this source are given below:
Source 2:
```
  RA (J2000.0):  86.1666  =  05:44:39.99
  Dec (J2000.0): +56.7487  =  +56:44:55.3
  Error: 8.4 arcsec (radius, 90% conf.)
  Count-rate: (2.09 [+1.11, -0.84])e-3 ct s^-1	 
  Distance: 301 arcsec from Swift/BAT-GUANO position.
  Flux: (3.3 [+1.8, -1.3])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)
```
Two uncatalogued sources were also detected too far from the GRB position to be likely afterglow candidates.
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/00021623.
This circular is an official product of the Swift-XRT team.
GCN Circular #34830
J.Mangan (CNRS/IJCLab), E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 08:05:03.30 UT on 17 October 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 231017A (trigger 719222708/231017337), which was also detected by the Swift/BAT-GUANO (DeLaunay et al. 2023, GCN 34824).
The Fermi GBM Final Real-time Localization is reported in GCN 34822.
The GBM light curve consists of a single emission episode with a duration (T90) of about 4.8 s (50-300 keV). The time-averaged spectrum from T0-3.5 to T0+4.7 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.1 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 270 +/- 82 keV.
A Band function fits the spectrum equally well with Epeak= 175 +/- 92 keV, alpha = -0.9 +/- 0.3 and beta = -1.9 +/- 0.3.
The event fluence (10-1000 keV) in this time interval is (1.7 +/- 0.2)E-06 erg/cm^2. The 64-msec peak photon flux measured starting from T0+0.77 s in the 10-1000 keV band is 7.8 +/- 1.6 ph/s/cm^2.
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 #34833
R. Kumar, A. Salgundi, R. Sharma, Y. Wagh, V. Swain, V. Bhalerao (IIT Bombay), S. Barway, G. C. Anupama (IIA), K. Angail (IAO)
We observed the field of GRB 231017A detected by Fermi (Fermi GBM team GCN 34822) with 0.7m GROWTH-India Telescope (GIT). GIT was triggered at 2023-10-18 15:49:46.29 UT, i.e., 1.32 days after the Fermi trigger, as a response to the Swift/GUANO trigger (J DeLaunay et al., GCN 34824). We obtained multiple frames in the g' and r' bands, covering the localisation reported by Swift/XRT (P. A. Evans et al., GCN 34825). We searched individual images and the stacked image for an afterglow, but do not detect any. Our upper limits on the magnitude of the afterglow are:
```
JD (mid) | t_mid-t0 (days)| Filter | Exposure (s) | Limiting Magnitude (5 sigma) |

2460236.187750 | 1.351 | g' | 3 x 300 | 19.27 |
2460236.171885 | 1.335 | r' | 6 x 300 | 21.08 |
2460236.250104 | 1.413 | g' | 2 x 400 | 19.98 |
```
The magnitudes are calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction.
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 #34834
R. Strausbaugh (Eastern Illinois University), A. Cucchiara (NASA) report on behalf of a larger collaboration:
We observed the Fermi GRB 231017A field (Fermi GBM team, GCN 34822) with the LCOGT 1-meter Sinistro instrument at the Teide Observatory, Tenerife site, on October 18, from 01:01 to 01:34 UT (corresponding to 15.93 to 16.48 hours from the GRB trigger time) with the SDSS r and i filters.
We performed a series of 3x300s exposures in each band. We do not detect a source within the Swift-XRT error region around the candidate X-ray source (Dichiara et al., GCN 34829) in either band.
The following upper limits are calculated using the PanSTARRS catalog as reference:
```
r > 23.0
i > 22.6
```
These magnitudes are not corrected for galactic extinction.
GCN Circular #34836
M. Shrestha (Univ. of Arizona), D. Sand (Univ. of Arizona), K. D. Alexander (Univ. of Arizona), J. Andrews (Gemini), J. Pearson (Univ. of Arizona), N. Smith (Univ. of Arizona), K. Bostroem (Univ. of Arizona) D. A. Howell (LCO/UCSB), C. McCully (LCO/UCSB), M. Newsome (LCO/UCSB), E Padilla Gonzalez (LCO/UCSB), C. Pellegrino (LCO/UCSB), G. Terreran (LCO/UCSB), J. Farah (LCO/UCSB) report on behalf of a wider Global Supernova Project collaboration:
We observed the field of GRB 231017A (Fermi GBM team GCN 34822, Trigger 719222708) localized by Swift/BAT-GUANO (DeLaunay et al. GCN 34824) with the 1-m telescope, on 2023-10-18T02:56:38.021 UT (60235.12 MJD, ~0.8 days after the trigger) using the Sinistro instrument in V, g, r, i bands. We do not detect any new optical counterpart within the error region of BAT-GUANO with upper limit of:
```
g> 22.5
r> 21.2
i> 20.9
```
These values were calculated with respect to ATLAS-REFCAT2 (Tonry et al. 2018, ApJ 867 105) catalog are not corrected for galactic extinction. This non-detection is in agreement with Strausbaugh et al., GCN 34834 and Kumar et al., GCN 34833.
GCN Circular #34840
D. Xu, X. Liu, S.Q. Jiang, Z.P. Zhu, S.Y. Fu, J. An, T.H. Lu (NAOC), J.Z. Liu (XAO) report on behalf of a large collaboration:
We observed the field of GRB 231017A detected by Fermi/GBM (Fermi GBM team, GCN 34822) and Swift/BAT-GUANO (DeLaunay et al. GCN 34824) using the No.2 50cm telescope (50B) located at Altay, Xinjiang, China. We obtained 20x180 s frames in the Sloan r-band, starting at 15:41:21 UT on 2023-10-17, i.e. 7.6 hr after the trigger.
No optical transient is detected in our stacked image within the error region of the Swift/BAT-GUANO, with the Swift-XRT Source 2 candidate inside the error region (Dichiara et al. GCN 34829), down to a limiting magnitude of r>20.5, calibrated with the nearby PanSTARRS field.
Altay Astronomical Time-Domain Project (JinShan Project for short) is located on the southern side of the Altay mountains in Xinjiang, China. It has geographical Longitude 88 43 35 E, Latitude +47 35 24 N, and Altitude 1025 meters. Altay and JinShan have the same meaning of Gold Mountain. The project 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 has different filters. JinShan is now at its early commissioning stage.
View this GCN Circular online at https://gcn.nasa.gov/circulars/34840.
GCN Circular #34841
S. Belkin; K. Ackley; A. Kumar; B. P. Gompertz; B. Godson; R. Starling; M. J. Dyer; J. Lyman; K. Ulaczyk; F. Jimenez-Ibarra; D. O'Neill; D. Steeghs; 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:
We report on observations with the Gravitational-wave Optical Transient Obs= erver (GOTO; Steeghs et al. 2022) in response to GRB 231017A (Fermi GBM tea= m, GCN 34822). Targeted observations were performed between 00:20:50 UT on 2023-10-18 and 02:37:04 UT on 2023-10-18 (starting ~16.25 hours after trigg= er). Each observation consisted of 4x90s exposures in the GOTO L-band (400-= 700 nm).
We identify no candidate optical counterparts within the Swift/BAT-GUANO lo= calisation region (DeLaunay et al., GCN 34824) or at the positions of the 9= sources identified in XRT pointed observations (Evans et al., GCN 34825; D= ichiara et al., GCN 34829). The mean 5-sigma limiting magnitude was L > 20.= 2 mag. This result is consistent with other observations (=E2=80=8B=E2=80= =8BKumar et al., GCN 34833; Strausbaugh et al., GCN 34834; Shrestha et al., GCN 34836; Xu et al., GCN 34840).
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a net= work of telescopes that is principally funded by the STFC and operated at t= he Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring= Observatory in NSW, Australia, on behalf of a consortium including the Uni= versity of Warwick, Monash University, Armagh Observatory & Planetarium, th= e University of Leicester, the University of Sheffield, the National Astron= omical Research Institute of Thailand (NARIT), the University of Turku, the= University of Portsmouth, the University of Manchester and the Instituto d= e Astrofisica de Canarias (IAC).
GCN Circular #34844
A. A. Breeveld (UCL-MSSL) and T. Parsotan (GSFC/UMBC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 231017A 73640 s after the GBM trigger (Mangan et al., GCN Circ. 34822). No new sources are seen in the UVOT data. A preliminary 3-sigma upper limit using the UVOT photometric system, (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) at the position of the XRT candidate (Source 2) given by Dichiara et al. (GCN Circ. 34829) is:
Filter T_start(s) T_stop(s) Exp(s) Mag
u 73640 101690 4839 >21.0
The magnitude in the table is not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.252 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #34853
Amit K. Ror, Rahul Gupta, Amar Aryan, Shashi B. Pandey, Rishi C., and Neelam Panwar (ARIES) report:
We observed the field of Fermi, and Swift detected GRB 231017A (Fermi GCM Team GCN 34822; Mangan et al. 2023, GCN 34830; DeLaunay et al. 2023, GCN 34824; and Swift team GCN 34825) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2023-10-18 at 22:19:07 UT, i.e., ~ 1.6 days after the GBM trigger. We have taken multiple frames with an exposure time of 100 s in the R filter. We stacked the images after the alignment. We did not detect any optical afterglow in our stacked image within the error box of Swift-XRT observation (Dichiara et al., 2023, GCN 34829). We obtain the following preliminary 3-sigma upper limit in the stacked image:
```
Date Start_UT T_start-T0 (days) Filter  Exp time (s)  Limiting magnitude

=========================================================

2023-10-18 22:19:07     1.6     R     100*36     > 21.6
```
Our non-detection is consistent with Kumar et al. 2023, GCN 34833; Strausbaugh et al. 2023, GCN 34834; Shrestha et al. 2023, GCN 34836; Xu et al. 2023, GCN 34840; and Belkin et al. 2023, GCN 34841.
The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalog. This circular may be cited.
GCN Circular #34867
S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (HSE) report on behalf of GRB IKI FuN:
We observed the field of GBM/Fermi and Swift/BAT-GUANO candidate of GRB 231017A (Fermi GCM Team GCN 34822; Mangan et al. 2023, GCN 34830; DeLaunay et al. 2023, GCN 34824; GCN 34825) with AZT-33IK telescope of Mondy observatory in R-filter on 2023-10-20 starting (UT) 18:02:43. We detect only one object within Swift-XRT X2 candidate error circle (Dichiara et al. GCN 34829) at coordinates of (J2000) 05:44:40.6245 +56:44:54.767. The object position is 5.3 arcsec apart from Swift-XRT center of the XRT X2 error circle. However, at the moment we cannot say about the variability of the object. We may propose the object as a candidate for an afterglow or host galaxy of GRB 230420A.
Preliminary photometry of the object is following
```
Date       UT start  t-T0     Exp.  Filter   OT     Err.  UL(3sigma)
                   (mid, days)  (s)
2023-10-20 18:02:43  3.43519  29x120 R       22.98  0.20   23.5
```
The photometry is based on nearby USNO-B1.0 R2 stars USNO-B1.0
```
RA DEC R2
05:44:36.1893600 +56:44:30.523200 15.96
05:44:49.0394400 +56:45:26.060400 16.24
05:44:55.8448800 +56:45:12.002400 16.30
05:44:44.9767200 +56:47:48.480000 16.48
```

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