Gamma-ray Burst 150413A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 13 Apr 15 13:56:16 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     637899,   Seg_Num: 0
GRB_RA:          190.385d {+12h 41m 32s} (J2000),
                 190.534d {+12h 42m 08s} (current),
                 189.895d {+12h 39m 35s} (1950)
GRB_DEC:         +71.824d {+71d 49' 26"} (J2000),
                 +71.740d {+71d 44' 25"} (current),
                 +72.098d {+72d 05' 52"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       0 [cnts]    Image_Peak=1104 [image_cnts]
TRIGGER_DUR:     64.000 [sec] 
TRIGGER_INDEX:   20000     E_range: 15-50 keV
BKG_INTEN:       0 [cnts]
BKG_TIME:        0.00 SOD {00:00:00.00} UT
BKG_DUR:         0 [sec]
GRB_DATE:        17125 TJD;   103 DOY;   15/04/13
GRB_TIME:        50098.55 SOD {13:54:58.55} UT
GRB_PHI:         144.56 [deg]
GRB_THETA:        36.14 [deg]
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    7.29 [sigma]
MERIT_PARAMS:     +1  +0  +0  +6  +1  -3  +0  +0 +15  +0 
SUN_POSTN:        21.59d {+01h 26m 21s}   +9.06d {+09d 03' 42"}
SUN_DIST:         98.87 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      313.06d {+20h 52m 14s}  -13.00d {-13d 00' 08"}
MOON_DIST:       112.20 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      124.03, 45.28 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      133.24, 63.39 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is an image trigger.  (The RATE_SIGNIF & BKG_{INTEN, TIME, DUR} are undefined.)  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 320.55,20.26 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 13 Apr 15 13:58:56 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     637899,   Seg_Num: 0
GRB_RA:          190.385d {+12h 41m 32s} (J2000),
                 190.534d {+12h 42m 08s} (current),
                 189.895d {+12h 39m 35s} (1950)
GRB_DEC:         +71.824d {+71d 49' 26"} (J2000),
                 +71.740d {+71d 44' 25"} (current),
                 +72.098d {+72d 05' 52"} (1950)
GRB_DATE:        17125 TJD;   103 DOY;   15/04/13
GRB_TIME:        50098.55 SOD {13:54:58.55} UT
TRIGGER_INDEX:   20000
GRB_PHI:         144.56 [deg]
GRB_THETA:        36.14 [deg]
DELTA_TIME:      0.00 [sec]
TRIGGER_DUR:     64.000 [sec] 
SOLN_STATUS:     0x13
RATE_SIGNIF:     0.00 [sigma]
IMAGE_SIGNIF:    7.29 [sigma]
LC_URL:          sw00637899000msb.lc
SUN_POSTN:        21.59d {+01h 26m 21s}   +9.06d {+09d 03' 44"}
SUN_DIST:         98.86 [deg]   Sun_angle= -11.3 [hr] (East of Sun)
MOON_POSTN:      313.09d {+20h 52m 20s}  -13.00d {-12d 59' 47"}
MOON_DIST:       112.20 [deg]
MOON_ILLUM:      34 [%]
GAL_COORDS:      124.03, 45.28 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      133.24, 63.39 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        The next comments were copied from the BAT_POS Notice:  
COMMENTS:        This is an image trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 320.55,20.26 [deg].

GCN Circular #17688
C. B. Markwardt (NASA/GSFC), M. M. Chester (PSU), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), C. Pagani (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL) and T. N. Ukwatta (LANL) report on behalf of the Swift Team:
At 13:54:58 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 150413A (trigger=637899). Swift did not slew immediately to the burst due to an observing constraint. The BAT on-board calculated location is RA, Dec 190.385, +71.824 which is
```
   RA(J2000) = 12h 41m 32s
   Dec(J2000) = +71d 49' 26"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 120 sec. The peak count rate was ~1100 counts/sec (15-350 keV), at ~2 sec after the trigger.
Due to an observing constraint, Swift cannot observe until T0+4 days. There will be no XRT or UVOT data until this time.
Burst Advocate for this burst is C. B. Markwardt (Craig.Markwardt AT nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
GCN Circular #17689 / ATEL #7381
K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University
E. Gorbovskoy, V. Lipunov, N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov, D.Kuvshinov, Lomonosov Moscow State University, Sternberg Astronomical Institute
D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory
A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory
V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk
V.Krushinski, I.Zalozhnih, A. Popov Ural Federal University, Kourovka
Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
Claudio Mallamaci, Carlos Lopez and Federico Podest Observatorio Astronomico Felix Aguilar (OAFA)
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Tunka was pointed to the GRB150413A (Markwardt et al. GCN 17688) 132 sec after trigger time at 2015-04-13 13:57:10 UT in two polarizations.
We see bright OT at:
```
RA, Dec = 12 41 41.98   +71 50 28.0
Mag = 16.1 (unfiltered 0.2B +0.8R UsnoB1)
```
The discovery image is available at https://master.sai.msu.ru/static/OT/grb150413A.jpg The message may be cited.
GCN Circular #17690
N.Tyurina, E. Gorbovskoy, N.Tyurina, V.Kornilov, P.Balanutsa, A.Kuznetsov, D.Kuvshinov, Lomonosov Moscow State University, Sternberg Astronomical Institute
K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University
D.Buckley, S. Potter, A.Kniazev, M.Kotze South African Astronomical Observatory
A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Sennik Kislovodsk Solar Station of the Pulkovo Observatory
V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk
V.Krushinski, I.Zalozhnih, A. Popov Ural Federal University, Kourovka
Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
Claudio Mallamaci, Carlos Lopez and Federico Podest Observatorio Astronomico Felix Aguilar (OAFA)
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Tunka was pointed to the GRB150413A (Markwardt et al. GCN 17688) 132 s. After MASTER OT J124141.98+715028.0 detection (Ivanov et all, GCN 17689) we see obvious brightening on next 4 expozition sets in two polarizations.
After 18 min MASTER OT J124141.98+715028.0 is about 14.7 !
The message may be cited.
GCN Circular #17691 / ATEL #7381
M. Serino (RIKEN), H. Negoro (Nihon U.), S. Nakahira (JAXA), S. Ueno, H. Tomida, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA), T. Mihara, M. Sugizaki, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, T. Yoshii, Y. Tachibana (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, R. Imatani (Osaka U.), M. Nakajima, T. Namba, M. Fujita, F. Honda, K. Tanaka, T. Masumitsu (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori (Kyoto U.), Y. Tsuboi, S. Kanetou (Chuo U.), M. Yamauchi, D. Itoh (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Morii (ISM) report on behalf of the MAXI team:
At 13:56:30 UT, the MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at the position (R.A., Dec) = (190.278 deg, 71.742 deg) = (12 41 07, +71 44 31) (J2000). The position is consistent with that reported by Markwardt et al. (GCN 17688).
The X-ray flux averaged over the scan was 440 +- 40 mCrab (4-10keV, 1 sigma error). There was no significant excess flux in the previous transit at UT 12:24 with an upper limit of 20 mCrab.
GCN Circular #17692
S. Schmalz (AIP), A. Pozanenko (IKI), N. Tungalag (Research Center of Astronomy and Geophysics MAS), E. Mazaeva (IKI), A. Volnova (IKI), I.Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the GRB 150413A (Markwardt et al., GCN 17688; Serino et al., GCN 17691) with ORI-40 telescope of Khureltogot observatory starting on Apr., 13 (UT) 14:08:52, i.e. ~10 minutes after burst trigger. Within BAT/Swift error circle we clearly detect fading optical source (Ivanov et al. GCN 17689, Tyurina et al. GCN 17690). Preliminary photometry of the source in single images is following
```
Date        UT start   t-T0  Filter    Exp.   OT  OT_err
                       (mid, days)      (s)

2015-04-13  14:08:52   0.0069 none     60  14.7 0.1
2015-04-13  14:39:52   0.0318 none     60  15.6 0.1
2015-04-13  15:11:54   0.0541 none     60  16.3 0.1
```
Photometry is based on nearby USNO-B1.0 stars, R2 mags. Observation is continuing.
GCN Circular #17693
D. Xu (NAOC), X. Zhang, C.-H. Bai, G.-J. Feng, A. Esamdin, L. Ma, J.-Z. Liu (XAO), Y. Qin (Geneva Observatory), J.-P. Yuan, Z.-G. Wen (XAO) report:
We observed the field of GRB 150413A (Markwardt et al., GCN 17688; Serino et al., GCN 17691) using the 1m telescope located at Nanshan, Xinjiang, China. Observations started at 15:00:38 UT on 2015-04-13, i.e., 1.09 hr after the burst and a series of 150s R-band images were obtained and observations are ongoing.
The OT reported by MASTER (Ivanov et al., GCN 17689; Tyurina et al., GCN 17690) is within the BAT error circle, and it is clearly detected in each of our images. Preliminary reduction shows that the OT has been decaying very slowly since our observations. It has m(R) ~ 15.4 at 1.115 hr post-burst and has m(R) ~ 15.8 at 1.724 hr post-burst, calibrated with the same USNO B1 star (#1618-0098185, R=15.59, close to R1=16.02). The OT's lightcurve behavior is unusual compared to normal GRB optical afterglows, although it indeed could be the afterglow of the GRB.
We note that there is a bright and much extended galaxy within the BAT error circle. However, we didn't find any apparent new point source within the galaxy, compared to DSS.
In addition, we observed the field using the Nanshan 25m radio dish in the timing mode, to check if there is any radio pulse mimicking a fast radio burst and following the BAT trigger.
GCN Circular #17694
S. Klose, S. Schmidl, B. Stecklum, A. Nicuesa Guelbenzu, D. A. Kann, and F. Ludwig (TLS Tautenburg) report:
Tautenburg observed the afterglow of GRB 150413A (Markwardt et al., GCN 17688; Ivanov et al., GCN 17689; Tyurina et al., GCN 17690; Serino et al., GCN 17691; Schmalz et al., GCN 17692; Xu et al., GCN 17693) with the 1.34m Schmidt telescope under good weather conditions.
At a mean time of 19:23 UT we measure a preliminary magnitude of R = 17.2 +/- 0.1, calibrated against the USNO B1 star #1618-0098185 (Xu et al.).
Observations are continuing.
GCN Circular #17695
S. Schmalz (AIP), N. Tungalag (Research Center of Astronomy and Geophysics MAS), A. Pozanenko (IKI), E. Mazaeva (IKI), A. Volnova (IKI), I. Molotov (KIAM), report on behalf of larger GRB follow-up collaboration:
We observed the field of the GRB 150413A (Markwardt et al., GCN 17688; Serino et al., GCN 17691) with ORI-40 telescope of Khureltogot observatory starting on Apr., 13 (UT) 14:08:52 and finishing on Apr. 13 (UT) 20:08:39. The afterglow (Ivanov et al., GCN 17689, Tyurina et al., GCN 17690, Schmalz et al., GCN 17692, Xu et al., GCN 17693, Klose et al., GCN 17694) is detected up to the end of our observations. Preliminary light curve obtained for single unfiltered images and calibrated against nearby USNO-B1.0 stars (R2 mags) can be found in http://grb.rssi.ru/GRB150413A/GRB150413A_ORI40_lc.jpg
In particular, our photometry on Apr., 13 (UT) 19:21:35 R=17.2+/-0.1 is compatible with photometry at (UT) 19:23 reported by Klose et al. (GCN 17694).
GCN Circular #17696
D. A. Perley (Caltech) and S. B. Cenko (GSFC) report:
The Palomar 60-inch telescope observed the location of the optical counterpart of GRB 150413A (Markwardt et al., GCN 17688; Ivanov et al., GCN 17689) starting at 03:15:21 UT on 2015-04-14. We acquired 3x180s images in griz filters under good conditions.
The optical transient is well-detected in all four filters. Calibrating relative to USNO stars in the field, we measure a magnitude of R = 19.1 (+/- 0.1) mag at this time (t = 0.560 days after the BAT trigger), indicating significant fading since the early observations.
Further follow-up is planned.
GCN Circular #17697
R. Sanchez-Ramirez (UPV/EHU, IAA-CSIC), A. J. Castro-Tirado (IAA-CSIC, ISA-UMA), F. Hoyos and J. Aceituno (CAHA), on behalf of a larger collaboration, report:
Following the detection of GRB 150413A by Swift (Markwardt et al. GCNC 17688) we have obtained a 1200s+1800s spectrum at the position of the optical afterglow (Ivanov et al. GCNC 17689, Serino et al. GCNC 17691, Schmalz et al. GCNC 17692, Xu et al. GCNC 17693, Klose et al. GCNC 17694). Observations were carried out with the 2.2m CAHA telescope (+ CAFOS) at the German-Spanish Calar Alto Observatory, starting at 20:25 UT. (i.e. 6.5 hr post-burst) under poor weather and seeing conditions. After a preliminary reduction, we have detected a broad absorption line which we identify as Lyman-alpha at a reshift of z = 3.2. Due the low SNR of the combined spectrum, we only detect several lines at low significance (Ni II, Si IV, C IV, Fe II,=85) consistent with this redshift, which we propose to be the redshift of GRB 150413A.
We acknowledge excellent support of the CAHA staff.
ATEL #7391
L. Tomasella, S. Benetti, E. Cappellaro, N. Elias-Rosa, P. Ochner, A. Pastorello, L. Tartaglia, G. Terreran, M. Turatto (INAF OAPd)
In the framework of the Asiago Transient Classification Program (Tomasella et al. 2014, AN, 335, 841), we have spectroscopically observed the OT of GRB150413A detected by MASTER (Atel #7381) with the Asiago 1.82 m Copernico Telescope (+AFOSC; range 340-820 nm; resolution 1.4 nm), on 20150413.87 UT, that is about 7.0h after detection.
The spectrum of the optical transient shows an almost flat continuum with a saturated, broad absorption centered at 5025 A. If this absorption is identified with Lyman alpha corresponds to a redshift z=3.17.
Optical photometry has also been obtained, providing the following sloan filter magnitudes: r=18.3 (13.900 UT), i=17.9 (13.901 UT) and g = 19.3 (13.903 UT).
The Asiago classification spectra are posted at the website http://sngroup.oapd.inaf.it.
Padova Asiago Supernova group: http://sngroup.oapd.inaf.it
GCN Circular #17698
I. van de Stadt (AWSV Metius, Alkmaar, The Netherlands) and K. Wiersema (U. of Leicester) report:
We observed the field of GRB 150413A (Markwardt et al. GCN 17688; Ivanov et al., GCN 17689) using the ABT, a 10-inch remote controlled observatory in Alkmaar, The Netherlands. In a series of I band exposures, with midpoint 0.55 days after burst, the afterglow is not detected, with a 5-sigma upper limit of 18.7 mag (calibrated using APASS field stars and the Jordi et al. (2005) conversions). This limit is in agreement with the light curve break seen by Schmalz et al. (GCN 17695).
GCN Circular #17700
Kosmas Gazeas and Konstantinos Sapountzis (National Univ. of Athens) report:
On 13 April 2015, we observed the GRB candidate optical counterpart GRB150413A, as reported by Markwardt et al., GCN 17688 and Serino et al., GCN 17691. The observations have been obtained with the 0.40 m f/8 robotic telescope at the University of Athens in R-band (Bessell specifications). Data collection has started on Apr., 13 (UT) 17:38:58 and finishing on Apr. 13 (UT) 18:08:08 (mid-exposure time). A sum of 15 exposures of 120 sec each was collected and all data were combined into a single image, although the optical afterglow was barley seen in each individual exposure. Photometry with a 3 pixel (approximately 4 arcsec) radius aperture yields an R magnitude estimation of R = 17.9 +- 0.3 mag for GRB150413A, as compared with respect to the nearby USNO-B1.0 stars, which lie within a radius of 3-4 arcminutes around the source. No absolute photometric calibration has been applied on these data.
This message is quotable in publications.
GCN Circular #17701
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 150413A (trigger #637899) (Markwardt, et al., GCN Circ. 17688). The BAT ground-calculated position is RA, Dec = 190.396, 71.839 deg which is
```
  RA(J2000)  =  12h 41m 35.1s
  Dec(J2000) = +71d 50' 21.9"
```
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 35%.
The mask-weighted light curve shows a multi-peaked structure that starts at ~ T-100 s and ends at ~ T+200 s. The most prominent pulse starts at ~ T+90 s, peaks at ~ T+110 s, and ends at ~ T+120 s. T90 (15-350 keV) is 263.6 +- 36.7 sec (estimated error including systematics).
The time-averaged spectrum from T-93.0 to T+209.8 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.75 +- 0.14. The fluence in the 15-150 keV band is 4.3 +- 0.4 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+110.78 sec in the 15-150 keV band is 1.6 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/637899/BA/
GCN Circular #17702
Veli-Pekka Hentunen, Markku Nissinen and Tuomo Salmi (Taurus Hill Observatory, Varkaus, Finland) report:
We have detected GRB 150413A optical afterglow at iTelescope observatory T7 and T18 (AstroCamp Observatory, Nerpio, Spain) using T7 0.43-m/6.8 and T18 0.32-m/8.0 astrographs. The observations were started at 2015-04-13 20:29:13 (UT) and stopped at 23:54:26 (UT). Fifteen unfiltered images and four photometric R filter images with 120 sec exposure time were made.
The afterglow was detected at the following position RA 21:41:41.88 and DEC +71:50:27.9.
The following magnitude were obtained from the observations using USNO-B1.0 1618-0098208 (R1=14.38) as a comparison star:
```
Telescope   Tmid(h)+T0    Filter             Exp. time         Mag
T7                6.611          unfiltered        2x120s          17.2CR  
T7                6.728          unfiltered        3x120s          17.4CR  
T7                6.976            R                 2x120s          17.7R 
T7                7.184            R                 2x120s          17.9R 
T18              9.508          unfiltered        4x120s          18.0CR
T18              9.685          unfiltered        4x120s          18.0CR
T18              9.904          unfiltered        2x120s          18.0CR
```
GCN Circular #17704
U.Quadri, L.Strabla and R.Girelli report:
We imaged the field of GRB 150413A detected by SWIFT(trigger 637899) with the robotic telescope of (IAU station 565) Bassano Bresciano Observatory, Italy (member of ISSP:Italian Supernovae Search Project)
The observations started 5.44 hour after the GRB trigger, at the end of twilight, with our schmidt telescope D=320/400 mm F/D=3.1.
Weather conditions were good.
We co-added 13 series of 10 exposures of 120 sec each.
```
Start T0+      End T0+      Vlim
---------------------------------
5.44 hour    10.26 hour     19.5
```
We clearly detect the optical counterpart at the following coordinates:
12h 41m 41.78s +71d 50m 27s +-2 arcsc.
Magnitudes were estimated with the UCAC4 cat. and are not corrected for galactic dust extinction:
```
----------------------
      JD        CV mag  
----------------------
2457126.30650   17.92 
2457126.32100   17.94 
2457126.33532   18.10 
2457126.34963   17.83 
2457126.36395   17.99 
2457126.37827   18.02 
2457126.39258   18.21 
2457126.40691   18.10 
2457126.42122   18.21 
2457126.43482   18.28 
2457126.47849   18.54 
2457126.49282   18.78 
2457126.50714   19.20 
```
The image, and magnitude plot are available at: http://www.osservatoriobassano.org/GRB.asp
The message may be cited.
GCN Circular #17705
M.M.M. Santangelo and S. Gambogi report:
We performed R and I bands CCD imagery of the field of GRB 150413A with the 0.60-meter f/9.83 Cassegrain reflector of Capannori Astronomical= Observatory, Italy. Weather conditions were good, the seeing was fairly good, and the night-s= ky brightness at zenith was 20.15 mag/arcsec2 in V band. We clearly detected the optical counterpart of GRB 150413A. Magnitudes in Johnson/Cousins R and I bands derived by means of Mira prof= essional 7 UE software are as follows:
```
Date           UT         Exposure   Band   mag =C2=B1 sigma
2015-04-13   20:56:22   300 s	   I	  17.2 =C2=B1 0.2
2015-04-13   21:04:43   180 s	   R	  17.6 =C2=B1 0.1
2015-04-13   21:11:02   360 s	   I	  17.29 =C2=B1 0.04
```
Photometry is based on the nearby GSC 4397:1311 star, with magnitudes of = comparison star from PPMXL. This message may be cited.
GCN Circular #17706
G. Masi and P. L. Catalano, the Virtual Telescope Project - Italy, report:
We started time-series observations of GRB 150413A (C. B. Markwardt et al., GCN 17688) with the 17" robotic unit part of the Virtual Telescope (Ceccano, Italy) at 21:25:00 UT, that is 7.5 hours after the burst.
An optical source is visible where described by K.Ivanov et al. (GCN 117689) on 60s and 120s exposures, unfiltered. The position of the source is RA: 12 41 41.97 Decl.: +71 50 27.7 (J2000.0, mean residuals of 0.2") and the magnitude was estimated to be 18.0, assuming R mags for the reference stars from UCAC-4.
We covered the source for about one hour, detecting a fadind of about 0.4 mags from the start to the end of the series.
Details are available on the page: http://goo.gl/8jCkhs
This message can be cited.
GCN Circular #17707
D. A. Perley (Caltech) and S. B. Cenko (GSFC) report:
We have continued to follow the optical counterpart of GRB 150413A (Markwardt et al., GCN 17688; Ivanov et al., GCN 17689) with the Palomar 60-inch robotic telescope. A second griz epoch was acquired between 10:08:52 and 10:49:31 UT on the night of 2015-04-14, followed by two deeper epochs (one gri, one r only) on the night of UT 2015-04-15.
Calibrating our r-band observations to a common set of USNO R-band reference stars, we derive the following photometry (statistical uncertainties only):
```
dt_mid = 0.5602 day :  R = 19.13 +/- 0.03
dt_mid = 0.8464 day :  R = 20.23 +/- 0.06
dt_mid = 1.6034 day :  R = 21.52 +/- 0.16
dt_mid = 1.8652 day :  R = 21.74 +/- 0.18
```
This suggests steep decay over this period (decay index ~ 2.2).
GCN Circular #17708
G.E. Anderson, R.P. Fender, T.D. Staley, K. Mooley (University of Oxford), A.J. van der Horst (George Washington University), A. Rowlinson (CASS)
We observed the position of GRB 150413A (Markwardt et al., GCN 17688) at 15 GHz with the Arcminute Microkelvin Imager (AMI-LA) starting on 2015 April 14.745 to 14.973 UT, corresponding to 1.2 days post-burst. On this date we possibly detected a radio source coincident with the MASTER=92s optical position (Ivanov et al., GCN 17689) with a preliminary flux of 0.19 +/- 0.04 mJy. There are no catalogued radio sources at this position.
An earlier observation was conducted on 2015 April 13.747 to 13.914 UT, corresponding to 0.2 days post-burst, yielding a 3 sigma flux upper limit of 0.15 mJy.
Further AMI monitoring is planned. We thank the AMI staff for scheduling these observations.
GCN Circular #17709
J. Mao, C. Wang and J.-M. Bai report:
We observed the field of GRB 150413A (Markwardt et al., GCN 17688) with the 2.4-meter optical telescope at Gao-Mei-Gu (GMG) station of Yunnan Observatory. Observations began from 13:35:29 UT, April 14, 2015, about 23.7 hours after the trigger. We marginally detected the optical counterpart and estimated the magnitude as I~20.3.
GCN Circular #17710
A. de Ugarte Postigo (IAA-CSIC, DARK/NBI) and L. Tomasella (INAF-OAPd) report:
We have reanalysed the spectra of the afterglow of GRB 150413A (Markwardt =20 et al. GCN 17688, Ivanov et al. GCN 17689) obtained by the Asiago Transient=20 Classification Program (Tomasella et al. 2014, AN, 335, 841) with the Asiago=20 1.82 m Copernico Telescope +AFOSC (Tomasella et al. ATel 7391). In addition=20 to the Ly-alpha feature already reported, we identify absorption features of SiII,=20 SiII*, CII, SiIV, CIV, FeII and AlII at a common redshift of 3.139+/-0.003, slightly=20 lower than previously reported by Sanchez-Ram=EDrez (GCN 17697) and by=20 Tomasella et al. (ATel 7391). In addition we report a tentative detection of a MgII=20 intervening absorber at z=3D0.950+/-0.003.
GCN Circular #17713
Changsu Choi, Myungshin Im (CEOU/SNU), Hyun-Il Sung (KASI), and Yuji Urata (NCU), on behalf of EAFON
We observed the field of GRB 150413A, Swift GRB 150413A (Markwardt et al., GCN 17688) in B,R-band using the 1-m telescope at Mt. Lemmon Optical Observatory (LOAO) in Arizona, US
We obtained B, R-band images on Apr. 14. We identified the optical afterglow in both band. The photometric calibraton is based on APASS catalog(AAVSO) in the observed field.
Details of Photometry are below:
```
UT                               Filter       Mag                 Hour
after detetion trigger(2015/04/13T 13:54:58)
2015/04/14T 04:54:07    B            20.95 +-0.25    15.13583

2015/04/14T 05:08:05    R            19.82 +-0.14    15.36861
```
GCN Circular #17714
A. S. Moskvitin (SAO RAS) report on behalf of larger GRB follow-up collaboration:
The field of GRB 150413A (Markwardt et al., GCNC 17688) was observed with the Zeiss-1000, 1-m telescope of SAO RAS. The observations were carried out on the April, 16, 20:00:28--21:31:31 UT (T-T0 = 3.285 days). 16 x 300 sec. frames in Rc filter were obtained. The OT (Ivanov et al.,GCNC 17689) is absent in the stacked image, therefore R > 23.0. The limiting value is based on the R2 magnitudes of nearby USNO-B1 stars.
We acknowledge A. S. Pozanenko, O. I. Spiridovova and V. S. Bychkova for the help in observations.
GCN Circular #17715
T.Fujiwara, Y. Saito, T. Yoshii, Y. Tachibana, H. Ohuchi, Y. Yano, S.Kurita, Y. Ono, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 150413A (C. B. Markwardt et al. GCN Circular #17688) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan.
The observation started on 2015-04-13 15:58:02 UT (~2.1 h after the burst). We detected the previously reported optical afterglow (K.Ivanov et al. GCN Circular #17689) in the Ic band.
The measured magnitudes are listed below.
```
T0+  MID-UT  T-EXP[sec]    g'                Rc             Ic
----------------------------------------------------------------------
263 min   4/13 18:17:28  240     > 17.3  > 17.2  16.09 +/- 0.30
2.04 days   4/15 14:52:50  15960    > 21.7  > 21.5  > 20.2
----------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
```
We used GSC2.3 catalog for flux calibration.
GCN Circular #17718
E. Mazaeva (IKI), A. Stepura (UAFO, ISON), A. Matkin (UAFO, ISON), A. Volnova (IKI), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the GRB 150413A (Markwardt et al., GCN 17688) with SANTEL-650 (0.65m) telescope of UAFO/ISON-Ussuriysk observatory sstarting on Apr., 14 (UT) 11:48:05. The afterglow (Ivanov et al., GCN 17689) is clearly detected in a combined image. Preliminary photometry the unfiltered combined image is following
```
Date            UT start   t-T0        Filter     Exp.     OT      OT_err
                                 (mid, days)          (s)

2015-04-14  11:48:05  0.95859   none     117*60  20.35   0.15
```
The photometry is based on nearby USNO-B1.0 stars
GCN Circular #17721
I. Bikmaev, E. Irtuganov, N. Sakhibullin (KFU/AST), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), I. Khamitov, H. Kirbiyik (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.)
report:
The field of the optical afterglow of GRB 150413A (Markwardt et al., GCN 17688, Ivanov et al., GCN 17689) was observed with Russian-Turkish 1.5-m telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey) using the TFOSC instrument.
We obtained series of Rc exposures in April 13/14 (50 frames x 300 sec, UT = 20:27 - 02:30 ) and in April 14/15 (4 frames x 600 sec, UT = 22:43 - 00:28, in partially cloudy conditions). The optical transient is clearly detected in each images.
Using USNO-B1 1618-0098185 star at RA,DEC = 12:41:09.18 +71:50:32.4 (J2000) with R2 = 15.59 mag as a reference we estimated the R-magnitudes of the afterglow:
```
T-T0, Mag. +/- Mag.err
(days)
0.2932 17.39 +/- 0.03
0.5200 18.70 +/- 0.05
1.4318 21.4  +/- 0.2
```
RTT-150 light curve in April 13/14, 2015, can be found at:
http://hea.iki.rssi.ru/grb/150413a/indexeng.html
The break in the light curve at (T-T0) = 0.33 days is evident (break is seen also in V-band data of Bassano Bresciano Observatory, Quadri et al, GCN 17704).
Before the break at (T-T0) = 0.33 days, the power law decay index is =~0.9, and it is close to 3.0 after that. Note, that decay index is close to 2.0 after (T-T0) = 0.7 days. Therefore, there are multiple breaks in the OT light curve.
GCN Circular #17723
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani (U. Leicester), V. D'Elia (ASDC), M. de Pasquale (INAF-IASFPA), A. Maselli (INAF-IASFPA), D.N. Burrows (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU) and C. B. Markwardt (NASA/GSFC) report on behalf of the Swift-XRT team:
We have analysed 6.2 ks of XRT data for the Swift/BAT-detected burst GRB 150413A (Markwardt et al., GCN Circ. 17688). The data are entirely in Photon Counting (PC) mode, collected between T0+303.3 ks and T0+550.9 ks.
No X-ray sources have been detected inside or close to the Swift/BAT error region. The 3-sigma upper limit at the position of the optical afterglow (Ivanov et al., GCN Circ. 17689) is 0.003 ct s^-1, corresponding to a 0.3-10 keV observed flux of 1.2e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum).
The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/ToO_GRBs/00637899.
This circular is an official product of the Swift-XRT team.
GCN Circular #17731
S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, and T. Cline on behalf of the Konus-Wind team, and
T. Sakamoto (AGU), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC), D. Palmer (LANL), M. Stamatikos (OSU) and T. Ukwatta (GWU), report:
We performed the Konus-Wind and the Swift/BAT joint spectral analysis of GRB 150413A (Swift/BAT trigger #637899: Markwardt et al., GCN Circ. 17688; Stamatikos et al., GCN Circ. 17701). Since the Konus-Wind observed this GRB in the waiting mode, we only have 3 channel spectral data for the Konus-Wind which cover the energy range from 20 keV to 1.2 MeV.
The joint spectral analysis of the Konus-Wind and the Swift/BAT data allows us to derive the broad-band spectral parameters of this burst.
The time intervals of the spectral data for each instrument are chosen from T0(BAT)-102.150 s to T0(BAT)+159.866 s (the time-integrated spectrum) and from T0(BAT)+95.098 s to T0(BAT)+118.650 s (the spectrum of the most prominent pulse) where T0(BAT) is the trigger time of BAT at 13:54:58 UTC.
The energy ranges which we used in the joint spectral analysis are 20-1200 keV and 15-150 keV for the Konus-Wind and the Swift/BAT respectively. The spectral data of two instruments are fitted with the spectral model multiplied by the constant factor to take into account the systematic effective area uncertainties in the response matrices of each instrument.
The spectrum of the most prominent pulse is well fitted with a power-law with exponential cutoff model: dN/dE ~ E^{alpha}*exp(-(2+alpha)*E/Epeak). No systematic residual from the best fit model is seen in the spectral data of each instrument.
The BAT constant factor is 0.71(-0.12,+0.16) (the KW constant factor is fixed to 1). The best fit spectral parameters are:
```
alpha = -1.01(-0.44,+0.65), and
Epeak = 96(-22,+56) keV (chi2/dof = 60/57).
```
The best fit spectral parameters for the GRB (Band) model fixing beta = -2.5 are:
```
alpha =  -1.00(-0.51,+0.84), and
Epeak = 91(-26,+77) keV
(chi2/dof = 63/57).
```
The time-integrated spectrum is well fitted with a power-law model with the the photon index 1.77(-0.09,+0.09), chi2/dof = 68/58. The BAT constant factor is 0.70(-0.09,+0.11) (the KW constant factor is fixed to 1). The energy fluence in the 15-1200 keV band calculated by a power-law model for this 262.016 s interval is 1.42(-0.19,+0.20)x10^-5 erg/cm2.
Assuming a redshift of 3.139 (de Ugarte Postigo and Tomasella, GCN Circ. 17710) and a standard cosmology model with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, Omega_Lambda = 0.685, the isotropic energy release in the 1 keV - 10 MeV energy range is E_iso = 6.53(-1.29,+1.62)x10^53 erg.
All the quoted errors are at the 90% confidence level.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB150413A/

GCN Circular #17784
V. Rumyantsev (CrAO), K. Antoniuk (CrAO), E. Mazaeva (IKI), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the GRB 150413A (Markwardt et al., GCN 17688) with AZT-11 telescope of CrAO observatory starting on Apr. 13 (UT) 17:39:02. Several images were take in R-filter. The afterglow (Ivanov et al., GCN 17689) is clearly detected in all single images of 180 s exposure. Preliminary photometry is following

Date,       UT start,    OT,    OT_err

2015-04-13  17 40 32.11  16.56  0.12
2015-04-13  17 43 36.17  16.97  0.30
2015-04-13  17 46 40.21  16.48  0.07
2015-04-13  17 49 44.26  16.73  0.11
2015-04-13  17 52 48.30  16.48  0.15
2015-04-13  17 55 52.37  16.62  0.13
2015-04-13  17 58 56.41  16.74  0.09
2015-04-13  18 02 00.58  16.63  0.13
2015-04-13  18 05 04.68  16.78  0.10
2015-04-13  18 08 08.76  16.77  0.09
2015-04-13  18 11 12.83  16.63  0.07
2015-04-13  18 14 16.87  16.74  0.06
2015-04-13  18 17 20.95  16.74  0.04
2015-04-13  18 20 25.30  16.76  0.06
2015-04-13  18 23 29.10  16.77  0.10
2015-04-13  18 26 33.15  16.90  0.08
2015-04-13  18 29 37.20  16.74  0.07
2015-04-13  18 32 41.25  16.71  0.05
2015-04-13  18 35 45.30  16.78  0.04
2015-04-13  18 38 49.36  16.77  0.03
2015-04-13  18 44 31.44  16.88  0.03
2015-04-13  18 47 35.48  16.81  0.03
2015-04-13  18 50 39.57  16.87  0.03
2015-04-13  18 53 43.66  16.92  0.03
2015-04-13  18 56 47.73  16.98  0.03
2015-04-13  18 59 51.90  17.02  0.03
2015-04-13  19 02 55.98  16.95  0.04
2015-04-13  19 06 00.64  16.94  0.04
2015-04-13  19 09 04.22  17.08  0.07
2015-04-13  19 12 08.35  17.05  0.06

The photometry is based on nearby USNO-B1.0 1618-0098185 (Xu et al., GCN 17693) assuming R=15.59.

GCN Circular #17797
G. E. Anderson, R. P. Fender, T. D. Staley, K. Mooley (University of Oxford), A. J. van der Horst (George Washington University), A. Rowlinson (CASS)
We re-observed the position of GRB 150413A (Markwardt et al., GCN 17688, Ivanov et al., GCN 17689) at 15 GHz with the Arcminute Microkelvin Imager (AMI-LA) following the possible detection of its radio counterpart reported in Anderson et al., GCN 17708. This observation took place on 2015 April 15.798 to 15.964 UT, corresponding to 2.2 days post-burst, resulting in a flux of 0.20 +/- 0.04 mJy. A follow-up AMI observation on 2015 April 23.947 to 24.114 UT, corresponding to 10.4 days post-burst, did not detection the radio counterpart with a 3 sigma upper limit of 0.1 mJy. We therefore confirm that the coincident radio source reported in Anderson et al., GCN 17708 is the radio counterpart to GRB 150413A.
We thank the AMI staff for scheduling these observations.
1511.02641 from 10 Nov 15
E. S. Gorbovskoy et al.: Early polarization observations of the optical emission of gamma-ray bursts: GRB150301B and GRB150413A
We report early optical linear polarization observations of two gamma-ray bursts made with the MASTER robotic telescope network. We found the minimum polarization for GRB150301B to be 8% at the beginning of the initial stage, whereas we detected no polarization for GRB150413A either at the rising branch or after the burst reached the power-law afterglow stage. This is the earliest measurement of the polarization (in cosmological rest frame) of gamma-ray bursts. The primary intent of the paper is to discover optical emission and publish extremely rare (unique) high-quality light curves of the prompt optical emission of gamma-ray bursts during the non-monotonic stage of their evolution. We report that our team has discovered the optical counterpart of one of the bursts, GRB150413A.

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