Gamma-ray Burst 160509A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/MAXI NOTICE
NOTICE_DATE:     Mon 09 May 16 09:18:30 UT
NOTICE_TYPE:     MAXI Unknown Source Position
EVENT_ID_NUM:    517316334
EVENT_RA:        311.31d {+20h 45m 16s} (J2000),
                 311.25d {+20h 45m 00s} (current),
                 311.51d {+20h 46m 01s} (1950)
EVENT_DEC:       +75.99d {+75d 59' 38"} (J2000),
                 +76.05d {+76d 03' 14"} (current),
                 +75.81d {+75d 48' 35"} (1950)
EVENT_ERROR:     1.0 [deg radius, stat+sys, 90% containment]
EVENT_FLUX:      2894.0 +- 0.0 [mCrab]
EVENT_DATE:      17517 TJD;   130 DOY;   16/05/09
EVENT_TIME:      32688.00 SOD {09:04:48.00} UT
EVENT_TSCALE:    1day
EVENT_EBAND:     Low, 2-4 keV
SUN_POSTN:        46.73d {+03h 06m 55s}  +17.52d {+17d 31' 04"}
SUN_DIST:         74.32 [deg] 
MOON_POSTN:       85.02d {+05h 40m 04s}  +18.31d {+18d 18' 41"}
MOON_DIST:        81.57 [deg] 
MOON_ILLUM:      10 [%] 
GAL_COORDS:      109.86, 19.86 [deg] galactic lon,lat of the burst (or transient)      
ECL_COORDS:       53.91, 74.26 [deg] ecliptic lon,lat of the burst (or transient)       
COMMENTS:        MAXI Unknown Source Position. GRB or unknown X-ray Transient.

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/MAXI NOTICE
NOTICE_DATE:     Mon 09 May 16 09:39:20 UT
NOTICE_TYPE:     MAXI Unknown Source Position
EVENT_ID_NUM:    517316334
EVENT_RA:        312.13d {+20h 48m 31s} (J2000),
                 312.07d {+20h 48m 17s} (current),
                 312.30d {+20h 49m 12s} (1950)
EVENT_DEC:       +75.81d {+75d 48' 36"} (J2000),
                 +75.87d {+75d 52' 16"} (current),
                 +75.62d {+75d 37' 23"} (1950)
EVENT_ERROR:     1.0 [deg radius, stat+sys, 90% containment]
EVENT_FLUX:      1307.0 +- 0.0 [mCrab]
EVENT_DATE:      17517 TJD;   130 DOY;   16/05/09
EVENT_TIME:      32688.00 SOD {09:04:48.00} UT
EVENT_TSCALE:    1day
EVENT_EBAND:     Low, 2-4 keV
SUN_POSTN:        46.74d {+03h 06m 58s}  +17.52d {+17d 31' 18"}
SUN_DIST:         74.16 [deg] 
MOON_POSTN:       85.24d {+05h 40m 57s}  +18.32d {+18d 19' 11"}
MOON_DIST:        81.59 [deg] 
MOON_ILLUM:      10 [%] 
GAL_COORDS:      109.81, 19.60 [deg] galactic lon,lat of the burst (or transient)      
ECL_COORDS:       53.08, 74.11 [deg] ecliptic lon,lat of the burst (or transient)       
COMMENTS:        MAXI Unknown Source Position. GRB or unknown X-ray Transient.

GCN Circular #19403
F.Longo (University and INFN, Trieste), E.Bissaldi (Politecnico and INFN, Bari), J. Bregeon (CNRS/IN2P3/LUPM), J. McEnery (NASA/GSFC), M. Ohno (Hiroshima U), S. Zhu (AEI Potsdam-Golm/AEI Hannover) report on behalf of the Fermi-LAT team:
At 08:59:04.36 UTC on May 09, 2016, Fermi-LAT triggered on high-energy emission from GRB 160509A, also detected by GBM (trigger 484477130/160509374).
The onboard location is
RA, Dec 310.1, 76.0 (J2000)
with an estimated error radius of 0.50 deg (90% containment, systematic error only). This was 31.8 deg from the LAT boresight at the time of the trigger.
We anticipate providing a refined location within the next 12 hours when the LAT science data for this burst is downlinked and processed.
We note that this is an extraordinarily bright GRB, and strongly encourage additional observations.
The Fermi-LAT point of contact for this burst is Francesco Longo (francesco.longo@ts.infn.it).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular #19404
```
TITLE:   GCN CIRCULAR
NUMBER:  19404 
SUBJECT: GRB 160227A: MAXI/GSC detection
DATE:    16/05/09 10:09:49 GMT    
FROM:    Taketoshi Yoshii at Tokyo Tech  
```
Y.Ono (Tokyo Tech), S. Ueno, H. Tomida, S. Nakahira, M. Ishikawa, Y. E. Nakagawa, Y. Sugawara (JAXA), T. Mihara, M. Sugizaki, M. Serino, W. Iwakiri, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, N.Isobe, S.Sugita, T. Yoshii, Y. Tachibana, T. Fujiwara (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, Y. Kitaoka (AGU), H. Tsunemi, R.Imatani (Osaka U.), H. Negoro, M. Nakajima, K. Tanaka, T. Masumitsu, T. Kawase (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori, A. Tanimoto (Kyoto U.), Y. Tsuboi, Y. Nakamura, R. Sasaki (Chuo U.), M. Yamauchi, K. Furuya (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team:
The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at UT 2016-05-09T09:04:16.
Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (312.131 deg, 75.810 deg) = (20 48 31, +75 48 36) (J2000) with a 90% C.L. statistical error of 0.06 deg and an additional systematic +uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 1307 +- 69 mCrab (4-10keV, 1 sigma error). Without assumptions on the source constancy,we obtain a rectangular error box for the transient source with the following corners:
```
 
(310.897 deg, 75.728 deg) = (20 43 35, +75 43 40) (J2000) 
(311.105 deg, 75.626 deg) = (20 44 25, +75 37 34) (J2000) 
(313.379 deg, 75.887 deg) = (20 53 30, +75 53 14) (J2000) 
(313.181 deg, 75.991 deg) = (20 52 43, +75 59 27) (J2000) 
```
There was no significant excess flux in the previous transit at UT 2016-0509T07:32 with an upper limit of 20 mCrab.
GCN Circular #19405
```
TITLE:   GCN CIRCULAR
NUMBER:  19405 
SUBJECT: Correction to GCN 19404; GRB 160509A: MAXI/GSC detection
DATE:    16/05/09 10:20:07 GMT    
FROM:    Taketoshi Yoshii at Tokyo Tech  
```
Y.Ono (Tokyo Tech), S. Ueno, H. Tomida, S. Nakahira, M. Ishikawa, Y. E. Nakagawa, Y. Sugawara (JAXA), T. Mihara, M. Sugizaki, M. Serino, W. Iwakiri, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, N.Isobe, S.Sugita, T. Yoshii, Y. Tachibana, T. Fujiwara (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, Y. Kitaoka (AGU), H. Tsunemi, R.Imatani (Osaka U.), H. Negoro, M. Nakajima, K. Tanaka, T. Masumitsu, T. Kawase (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori, A. Tanimoto (Kyoto U.), Y. Tsuboi, Y. Nakamura, R. Sasaki (Chuo U.), M. Yamauchi, K. Furuya (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team:
The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at UT 2016-05-09T09:04:16.
Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (312.131 deg, 75.810 deg) = (20 48 31, +75 48 36) (J2000) with a 90% C.L. statistical error of 0.06 deg and an additional systematic +uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 1307 +- 69 mCrab (4-10keV, 1 sigma error). Without assumptions on the source constancy,we obtain a rectangular error box for the transient source with the following corners:
```
(310.897 deg, 75.728 deg) = (20 43 35, +75 43 40) (J2000)
(311.105 deg, 75.626 deg) = (20 44 25, +75 37 34) (J2000)
(313.379 deg, 75.887 deg) = (20 53 30, +75 53 14) (J2000)
(313.181 deg, 75.991 deg) = (20 52 43, +75 59 27) (J2000)
```
There was no significant excess flux in the previous transit at UT 2016-0509T07:32 with an upper limit of 20 mCrab.
GCN Circular #19406
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a series of observations, tiled on the sky, of the Fermi/LAT GRB 160509A. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00054
Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. The probability of finding serendipitous sources, unrelated to the Fermi/LAT event is high: 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 #19407
J. A. Kennea (PSU) reports on behalf of the Swift team:
Swift performed a target of opportunity observation of the Fermi/LAT detected GRB 160509A (GCN 19403). In rapid analysis of XRT downlinked data we find a bright uncatalogued point source at the following location: RA/Dec (J2000) = 311.74406, 76.10634, which is equivalent to:
```
RA(J2000) = 20h 46m 58.6s
Dec(J2000) = +76d 06m 22.8s
```
with an estimated uncertainty of 8 arcseconds (90% confidence). This position lies 24.6' away from the LAT onboard position, and 8 arcminutes from a LAT ground refined position (Racusin, private communication), so we suggest this is likely the afterglow of GRB 160509A. A refined position will be issued soon. Swift observations of this burst are on-going.
GCN Circular #19408
J. A. Kennea (PSU), T.G.R. Roegiers (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), D.N. Burrows (PSU), L.M. McCauley (PSU), C. Pagani (U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 160509A (Longo et al. GCN Circ. 19403) in a series of observations tiled on the sky. The total exposure time is 1.7 ks, distributed over 7 tiles; the maximum exposure at a single sky location was 560 s. The data were collected between T0+7.3 ks and T0+7.5 ks, and are entirely in Photon Counting (PC) mode.
Using 250 s of XRT Photon Counting mode data and 1 UVOT images, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 311.75375, 76.10837 which is equivalent to:
```
RA (J2000):  20 47 00.90
Dec (J2000): +76 06 30.1
```
with an uncertainty of 2.3 arcsec (radius, 90% confidence). This position is 24.8 arcmin from the Fermi/LAT position, and 11 arcseconds from the preliminary XRT position (GCN 19407). The light curve is consistent with a constant source of mean count rate 1.4 ct/sec. We cannot determine fading at this time.
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.7 (+/-0.3). The best-fitting absorption column is 4.6 (+2.3, -1.8) x 10^21 cm^-2, in excess of the Galactic value of 2.1 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.9 x 10^-11 (6.6 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     4.6 (+2.3, -1.8) x 10^21 cm^-2
Galactic foreground: 2.1 x 10^21 cm^-2
Excess significance: 2.2 sigma
Photon index:	     1.7 (+/-0.3)
```
The results of the XRT-team automatic analysis of the likely afterglow are at http://www.swift.ac.uk/xrt_products/TILED_GRB00054/index_2.php. The results of the full analysis of the tiled XRT observations are available at http://www.swift.ac.uk/xrt_products/TILED_GRB00054.
This circular is an official product of the Swift-XRT team.
GCN Circular #19409
L.Izzo (IAA-CSIC), A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), C. Thoene (IAA-CSIC) report:
We observed the field of GRB 160509A (Longo et al., GCN 19403; Ono et al., GCN 19404) with the iTelescope.Net <http://itelescope.net> ( http://www.itelescope.net) T11 (Planewave CDK 0.51m) telescope located at the Mayhill observatory (NM). A single image of 300 s was obtained in the R filter, starting at 10:32:32 UT, 1.56 hr after the GRB trigger. We do not detect any optical afterglow candidate at the refined Swift-XRT position (Kennea et al. GCN 19408). We estimate an upper limit magnitude of R = 19.5 mag (3-sigma), using the USNO-B1 catalog as reference. We note that our image covers also the complete error box of the MAXI (Ono et al., GCN 19404). Data are available on request.
An image of the field of view can be seen at http://goo.gl/dKTki3
GCN Circular #19410
A. J. Levan (U. Warwick), N. R. Tanvir (U. Leicester), S. B. Cenko (NASA/GSFC), D. Perley (DARK) report on behalf of a larger collaboration:
We observed the field of Fermi/LAT GRB 160509A (Longo et al. GCN 19403) with the Gemini North telescope on Mauna Kea, beginning at 14:45 UT during morning twilight, approximately 5.75 hr post-burst. Consistent with the refined X-ray afterglow position reported by Kennea et al. (GCN 19408) we detect a faint source with preliminary magnitudes of r=23.52+/-0.15, z=21.35+/-0.30 (calibrated via SDSS stars in the field). We cannot make any statement about the variability of this source at the present time.
The position of the source is 20:47:00.93 +76:06:29.2 (J2000), accurate to about 0.5" in each coordinate.
The fairly red r-z colour could be explained if the burst was at a high redshift of z=5-6, or alternatively at a more moderate redshift with some extinction in the host galaxy.
We acknowledge the rapid response of the Gemini staff, in obtaining these observations.
GCN Circular #19411
O.J. Roberts (UCD), G. Fitzpatrick (UCD) and P. Veres (UAH) report on behalf of the Fermi GBM Team:
"At 08:59:04.36 UT on 09 May 2016, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 160509A (trigger 484477148/160509374). The trigger resulted in an Autonomous Repoint Request (ARR) by the GBM Flight Software owing to the high peak flux of the GRB. This ARR was accepted and the spacecraft slewed to the GBM in-flight location. The GRB was also detected by the LAT (F. Longo et al. 2016, GCN 19403), MAXI/GSC (Y. Ono et al. 2016, GCN 19404) and Swift XRT (J.A. Kennea et al. 2016, GCN 19408). The GBM on-ground location is consistent with these positions.
The angle from the Fermi LAT boresight at the GBM trigger time using the LAT position, is 32 degrees.
The GBM light curve consists of multiple peaks with a duration (T90) of about 371 s (50-300 keV). The time-averaged spectrum from T0-1.5 s to T0+39.4 s is best fit by a BAND function, with Epeak = 370 +/- 7 keV, alpha = -0.89 +/- 0.01, and beta = -2.11 +/- 0.02.
The event fluence (10-1000 keV) in this time interval is (1.51 +/- 0.01)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+16.6 s in the 8-1000 keV band is 75.5 +/- 0.6 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN Circular #19412
F. E. Marshall (NASA/GSFC) and T.G.R. Roegiers (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the Swift-XRT afterglow (Kennea et al., GCN Circ. 19408) 7259 s after the LAT trigger (Longo et al., GCN Circ. 19403). No UVOT source consistent with the position of Swift-XRT afterglow or the position of the optical afterglow candidate (Levan et al., GCN Circ. 19410) is found in the initial exposure. The preliminary upper limit using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) is:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

u                7259         7531          268          >20.5 
```
The magnitude in the table is not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.31 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #19413
F. Longo (University and INFN, Trieste), E. Bissaldi (Politecnico and INFN, Bari), G. Vianello (Stanford U.), E. Moretti (MPI, Munich), N. Omodei (Stanford U.), J. Bregeon (CNRS/IN2P3/LUPM), F. Dirirsa (Johannesburg U.), M. Yassine (LUPM, Montpellier), D. Kocevski, J. Racusin, J. McEnery (all NASA/GSFC), M. Ohno (Hiroshima U.) and S. Zhu (AEI Potsdam-Golm / AEI Hannover) report on behalf of the Fermi-LAT Team:
Using LAT source class events >100 MeV from 0 until 2660 seconds after the LAT trigger, we find a LAT localization of
RA, Dec = 311.3, 76.1 (J2000 deg)
with a 90% containment radius of 0.12 degrees (statistical only). The LAT executed an autonomous repoint 2 minutes after the trigger to follow the burst for 2.5 hours. A Fermi ToO for the next 36 hours has been issued.
Following our detection, Swift followed the GRB and detected the X-ray afterglow with the Swift/XRT (Kennea et al. GCN 19408).
The highest-energy photon is a 52 GeV event, which is observed 77 seconds after the GBM trigger.
The LAT Low Energy (LLE) emission consists of two bright structured peaks (around T0+12 and T0+18 s), in coincidence with the main GBM emission episode.
The >100 MeV emission spectrum during the main GBM emission episode (from T0 to T0+40 s, see Roberts et al. GCN 19411) is fit by a soft power-law with index -3.4 +/- 0.2, resulting in a flux of (0.56 +/- 0.06)E-4 ph cm^-2 s^-1.
The >100 MeV emission spectrum after 40 s and up to the currently available data (up to 2660 s) is fit by a power-law with index -2.0 +/- 0.1.
The Fermi LAT point of contact for this burst is Francesco Longo (francesco.longo@ts.infn.it).
The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular #19414
K. D. Alexander (Harvard), T. Laskar (NRAO / UC Berkeley), and E. Berger (Harvard) report on behalf of a larger collaboration:
We observed the Fermi/LAT GRB 160509A (Longo et al. GCN 19403) at multiple frequencies with the Karl G. Jansky Very Large Array (VLA) beginning 2016 May 9.72 UT (8.33 hours after the burst). At a mean frequency of 6.0 GHz, we detect a radio source with a preliminary flux density of ~80 uJy at
```
RA (J2000) = 20:47:00.89 +/- 0.11
Dec (J2000) = +76:06:28.92 +/- 1.2
```
consistent with the position of the candidate optical afterglow reported by Levan et al. (GCN 19410) and the refined Swift/XRT position (Kennea et al. GCN 19408). Follow-up observations are planned.
We thank the VLA staff for rapidly executing these observations.
GCN Circular #19415
H. Negoro (Nihon U.), S. Nakahira (JAXA), T. Mihara (RIKEN), S. Ueno, H. Tomida, M. Ishikawa, Y. E. Nakagawa, Y. Sugawara (JAXA), M. Sugizaki, M. Serino, W. Iwakiri, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), N. Kawai, N. Isobe, S. Sugita, T. Yoshii, Y. Tachibana, Y. Ono, T. Fujiwara (Tokyo Tech), A. Yoshida, T. Sakamoto, Y. Kawakubo, Y. Kitaoka (AGU), H. Tsunemi, R.Imatani (Osaka U.), M. Nakajima, K. Tanaka, T. Masumitsu, T. Kawase (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori, A. Tanimoto (Kyoto U.), Y. Tsuboi, Y. Nakamura, R. Sasaki (Chuo U.), M. Yamauchi, K. Furuya (Miyazaki U.), K. Yamaoka (Nagoya U.) report on behalf of the MAXI team:
We reexamined the localization of GRB 160509A (Longo et al. GCN 19403; Ono et al. GCN 19404,19405) only using the GSC camera 7 (Bcam1), and not using an uncalibrated GSC camera 0 (Acam0) which was also used in the previous analysis (GCN 19404, 19405).
We obtain the source position for a constant flux source at (R.A., Dec) = (311.521 deg, 76.057 deg) = (20 46 05, +76 03 24) (J2000) with a 90% C.L. statistical error of 0.12 deg and an additional systematic uncertainty of 0.1 deg (90% containment radius), and a rectangular error box for a variable flux source with the following corners:
```
(R.A., Dec) = (310.806 deg, 76.105 deg) = (20 43 13, +76 06 16) (J2000)
(R.A., Dec) = (311.249 deg, 75.892 deg) = (20 44 59, +75 53 32) (J2000)
(R.A., Dec) = (312.671 deg, 76.056 deg) = (20 50 41, +76 03 21) (J2000)
(R.A., Dec) = (312.242 deg, 76.270 deg) = (20 48 57, +76 16 13) (J2000)
```
The Swift/XRT source position (Kennea et al. GCN 19408; Levan et al. GCN 19410; Alexander et al. GCN 19414) is 0.076 arc-degree from the refined best position, and also within the rectangular region.
A GSC spectrum is roughly represented by an absorbed power-law with a photon spectral index of 1.26 +/- 0.16, and the resultant 2-10 keV flux is 2.78e-08 ergs/cm^2/s. The absorption column is fixed to 4.6 x 10^21 cm^-2 in the fit (Kennea et al. GCN 19408).
We also note that there was no significant excess flux in the next transit at 10:37 UT on 2016 May 9 with an upper limit of 20 mCrab.
GCN Circular #19416
S. B. Cenko (NASA GSFC), E. Troja (NASA GSFC), and S. Tegler (NAU) report= on behalf of a larger collaboration:
We imaged the location of the Fermi GBM (Roberts et al., GCN 19411), Fermi LAT (Longo et al., GCN 19403), and MAXI GSC (Ono et al, GCN 19405) GRB 160509A with the Large Monolithic Imager on the 4.3 m Discovery Channel Telescope in Happy Jack, AZ. Observations were obtained in the g', r', i', and z' filters beginning at 9:40 UT on 10 May 2016 (~ 1.03 d after the trigger).
At the location of the candidate optical afterglow (Levan et al., GCN 19410), we detect a source in all four filters. We report the following preliminary photometry (using nearby point sources from SDSS for calibration):
```
g' = 25.03 +/- 0.15
r' = 24.05 +/- 0.14
```
The source has faded since the Gemini observations reported by Levan et al. (GCN 19410), indicating that it is indeed the afterglow of GRB160509A. However, the detection in g=EF=BF=BD limits the host redshift to be z <~ 3.5, requiring significant dust extinction along the line of sight.
GCN Circular #19417
D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline, on behalf of the Konus-Wind team, report:
The very bright, long-duration GRB 160509A (Fermi-LAT detection: Longo et al., GCN 19403; MAXI/GSC detection: Ono et al., GCNs 19404; Fermi-GBM detection: Roberts, Fitzpatrick & Veres, GCN 19411) triggered Konus-Wind at T0=32326.696 s UT (08:58:46.696).
The light curve shows a broad, multi-peaked pulse in the interval from ~T0-10 s to ~T0+30 s, followed by several weaker emission episodes until ~T0+380 s. The emission is seen up to ~15 MeV.
As observed by Konus-Wind, the burst had a fluence of 2.90(-0.35,+0.35)x10^-4 erg/cm2, and a 64-ms peak flux, measured from T0+12.096 s, of 2.8(-0.2,+0.2)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum (measured from T0 to T0+370.944 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.99 (-0.08,+0.10), the high energy photon index beta = -2.08 (-0.17,+0.12), the peak energy Ep = 288 (-45,+48) keV, chi2 = 51.3/97 dof.
The spectrum near the peak count rate (measured from T0+11.264 to T0+12.800 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.71 (-0.07,+0.07), the high energy photon index beta = -2.27 (-0.14,+0.11), the peak energy Ep = 311 (-32,+35) keV, chi2 = 96.7/77 dof.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB160509_T32326/
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
GCN Circular #19419
N. R. Tanvir (U. Leicester), A. J. Levan (U. Warwick), S. B. Cenko (NASA/GSFC), D. Perley (DARK), A. Cucchiara (GSFC/STScI), K. Roth (Gemini), K. Wiersema (U. Leicester), A. Fruchter (STScI), T. Laskar (NRAO/U.C. Berkeley) report on behalf of a larger collaboration:
We observed the optical counterpart of Fermi/LAT GRB 160509A (Levan et al. GCN 19410) with the Gemini North telescope on Mauna Kea, beginning at 2016-05-10 13:15 UT obtaining both optical spectroscopy with GMOS-N and near-IR imaging with NIRI.
Our spectroscopy covers a wavelength range of about 5900 AA to 10100 AA, and reveals a single, well detected emission line which we interpret as [OII] 3727 AA at a redshift of z=1.17 (provisional analysis). Alternative possible identifications for this line are ruled out by the absence of other lines in the spectrum.
Our infrared imaging shows the source, presumably some combination of host and afterglow, to be very red with K(Vega)~16.6 and J(Vega)~19.7 calibrated via 2MASS stars in the field. This would be consistent with a heavily dust extinguished event. We also note that the source is apparently unresolved in K-band seeing of 0.55 arcsec.
We acknowledge the excellent support of the Gemini staff, in particular Michael Hoenig, and kind cooperation of the visiting observers, in expediting these observations. We also thank Gemini Head of Science, Nancy Levenson, for approving this request.
GCN Circular #19420
F. E. Marshall (NASA/GSFC) and T.G.R. Roegiers (PSU) report on behalf of the Swift/UVOT team:
The afterglow of the LAT-triggered GRB 160509A (Longo et al., GCN Circ. 19403) has been detected in the X-ray (Kennea et al., GCN Circ. 19408), optical (Levan et al., GCN Circ. 19410; Cenko et al., GCN Circ. 19416), near-IR (Tanvir et al., GCN Circ. 19419), and radio (Alexander et al. GCN Circ. 19414) bands. No afterglow was seen in the initial UVOT observation in the u filter (Marshall and Roegiers, GCN Circ. 19412). As detailed in the table below, additional UVOT observations also show no detections. All the upper limits are at 2-sigma confidence.
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

u                7259        19794          626          >21.6
u               24201        36310         1802          >22.2
v               25452        36990         1257          >21.4
white           24826        36919         1802          >23.2
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.31 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #19421
S. Schmidl, D. A. Kann, U. Laux (all TLS Tautenburg), S. Schulze (PUC), S. Klose, and A. Nicuesa Guelbenzu (both TLS Tautenburg) report:
We observed the location of the afterglow of the bright Fermi LAT/GBM (Longo et al., GCN 19403, Roberts et al., GCN 19411) GRB 160509A, localized in the X-rays by Kennea (GCN 19407) and Kennea et al. (GCN 19408), in the optical/NIR by Levan et al. (GCN 19411) and Cenko et al. (GCN 19416), as well as in the radio band by Alexander et al. (GCN 19414), with the 1.34m Schmidt telescope of the Thueringer Landessternwarte Tautenburg, in good conditions.
We obtained a total of 26 x 600 s images in the Rc band, starting at 20:46:04 UT, 11.78 hrs after the GRB. The total stack has an integration time of 15600 s, centered 0.583 days after the GRB.
At the afterglow position, we detect an extended source. Comparing to the higher resolution DCT image (Cenko & Tanvir, priv. comm.), there is a nearby source which is somewhat blended with the afterglow in our image. Therefore, we use a small aperature to measure the afterglow magnitude. Using four comparison stars in the surroundings, whose SDSS magnitudes were transformed to the Rc band using the transformation equations of Lupton (2005), we obtained a magnitude of:
Rc = 23.6 +/- 0.3 mag.
This is in good agreement with the detections derived by Levan et al. and Cenko et al. after transforming their results from AB to Vega mags.
The magnitude is not corrected for the Galactic extinction along the line of sight of E(B-V) = 0.25 mag (Schlafly & Finkbeiner 2011).
Using the prompt emission results of Konus-Wind (Frederiks et al., GCN 19417) and the redshift z = 1.17 (Tanvir et al., GCN 19419), we derive a bolometric (1 keV - 10 MeV in the source frame) isotropic energy release of (8.56 +/- 1.1)E53 erg, and a E_peak,rest = 625 keV. The isotropic energy release is very similar to that of GRB 130427A, and we note the light curve also shows similarities.
PS.: We also wish to point out that this GRB occurred on the 11th anniversary of the first ever detected short-GRB X-ray afterglow, that of GRB 050509A (Gehrels et al. 2005).
GCN Circular #19423
D. Lennarz (Michigan State University), I. Taboada (Georgia Tech) report on behalf of the HAWC collaboration (http://www.hawc-observatory.org/collaboration/):
We used data from the HAWC detector to perform a search for VHE emission in temporal coincidence with GRB 160509A (F.Longo et al., GCN 19403). At the time of the LAT trigger, the elevation of the burst in HAWC's field of view was only 27.98 degrees (it was rising, but culminated at an elevation of 33 degrees). The sensitivity of HAWC at this elevation is more than 2 orders of magnitude poorer than near the zenith. Furthermore, the energy threshold towards the horizon is much higher. Combined with the moderate redshift of z=1.17 (N. R. Tanvir et al., GCN 19419) it makes a detection by HAWC unlikely.
We used four search windows with respect to the LAT trigger time: one in the range -5 s to 45 s, which covers the main GBM emission episode (O.J. Roberts et al., GCN 19411) and appears to be correlated with the >100 MeV soft emission observed by the LAT (F.Longo et al., GCN 19413), a window from -5 s to 375 s, which extends slightly beyond the T90 observed by GBM and a time window from 45 s to 375 s, where the LAT data is fit with a power-law of index -2.0 +/- 0.1. We also searched -20 s to 20 s around the time of the highest-energy LAT photon (52 GeV) 77 seconds after the GBM trigger. A 2 degree angular bin is defined around the position of the Swift-XRT afterglow position (J. A. Kennea et al., GCN 19408) and the number of background events is estimated using an ON/OFF method. We find the counts in the search bin to deviate by 1.9 / 0.9 / 0.2 / -1.4 sigma from the background expectation. Our observations are consistent with background only.
The search was conducted using the main data acquisition that reconstructs the incident direction of showers. It uses data reconstructed at the HAWC site, not applying gamma-hadron separation. The implications of this non-detection with respect to the VHE fluence of this GRB will be reported elsewhere.
HAWC is a very-high-energy gamma-ray observatory operating in Central Mexico at a latitude of 19 deg north. HAWC has an instantaneous field of view of 2 sr and surveys 2/3 of the sky every day. A detailed description of the sensitivity of HAWC to GRBs can be found in A.U. Abeysekara et al., Astroparticle Physics 35, 641-650 (2012).
GCN Circular #19424
A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama, Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena) and the CALET collaboration:
The long-duration GRB 160509A (Longo et al., GCN circ. 19403; Ono et al., GCN circ. 19404; Roberts et al., GCN circ. 19411; Frederiks et al., GCN circ. 19417) triggered the CALET Gamma-Ray Burst Monitor (CGBM) at 08:58:51.21 on 9 May 2016. The burst signal was seen by all CGBM instruments. The angular separations between the GRB position (Kennea et al., GCN 19408) and the boresignt of the HXM and the SGM instrument at the trigger time were 108 deg. and 104 deg., respectively. Therefore, the GRB was outside the field of view of the CAL instrument.
The light curve of the SGM shows multiple overlapping pulses with a broad structure starting from T0-5 sec, peaking at T0+9 sec and ending at T0+30 sec. A hint of the emission is seen at T0+~370 sec. The T90 duration measured by the SGM data is 14.6 +- 0.6 sec (40-1000 keV).
The CGBM data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University.
GCN Circular #19425
V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov Blagoveschensk Educational State University, Blagoveschensk
V. Lipunov, E. Gorbovskoy, 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
K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk Irkutsk State University
A. Tlatov, A.V. Parhomenko, D. Dormidontov, V.Senik Kislovodsk Solar Station of the Pulkovo Observatory
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)
R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias
MASTER II robotic telescope (MASTER-Net: http://observ.pereplet.ru) located in Blagoveschensk was pointed to the GRB160509A (Longo et al GCN 19403) 15306 sec after trigger time at 2016-05-09 13:14:10 UT directly after sunset. On our first (180s exposure) set we not found optical transient brighter then 18.5m on single (180 s) and 20.0m on coadd (total exposure 1800 s) images at x-ray (Kennea et al GCN 19408) and optical (Levan et al 19410, Alexander et al GCN 19414, Cenko et al GCN 19416, Schmidl et al GCN 19421) position.
The message may be cited.
GCN Circular #19428
S. B. Cenko (NASA GSFC), S. Vogel (U. Maryland), D. A. Perley (DARK), and A. Fruchter (STScI) report on behalf of a larger collaboration:
We have imaged the location of the radio afterglow (Alexander et al., GCN 19414) of GRB 160509A (Longo et al., GCN 19403; Roberts et al., GCN 19411; Ono et al, GCN 19405) with the Very Large Array beginning at 10:11 UT on 2016 May 11 (2.0 d after the Fermi-GBM trigger time) in both C and X bands. The radio counterpart has brightened significantly since the early observations reported in Alexander et al., GCN 19414. We measure a preliminary flux density of ~ 0.7 mJy in X-band (9.0 GHz) and ~ 0.5 mJy in C-band (6.0 GHz), corresponding to a spectral index beta ~ 0.8 (fnu ~ nu^beta).
Further observations are planned.
GCN Circular #19532
K. P. Mooley, T. D. Staley, R. P. Fender (Oxford), G. E. Anderson (Curtin), T. Cantwell (Manchester), C. Rumsey, D. Titterington, S. H. Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods, P. Scott (Cambridge), K. Grainge, A. Scaife (Manchester)
We observed the Fermi/LAT GRB 160509A (Longo et al., GCN 19403) with the AMI Large Array at 15 GHz on 2016 May 23.25 and May 26.21 (UT) as part of the 4pisky program. We do not detect any source at the VLA location (Alexander et al., GCN 19414), with 3sigma upper limits of 137 uJy and 152 uJy respectively.
We thank the AMI staff for scheduling these observations. The AMI-GRB database is a log of all GRB follow up observations with the AMI, and is available at http://4pisky.org/ami-grb/.
1606.08873 from 30 Jun 16
Tanmoy Laskar et al.: A Reverse Shock in GRB 160509A
We present the second multi-frequency radio detection of a reverse shock in a $\gamma$-ray burst. By combining our extensive radio observations of the Fermi-LAT GRB 160509A at $z = 1.17$ up to $20$ days after the burst with Swift X-ray observations and ground-based optical and near-infrared data, we show that the afterglow emission comprises distinct reverse shock and forward shock contributions: the reverse shock emission dominates in the radio band at $\lesssim10~$days, while the forward shock emission dominates in the X-ray, optical, and near-infrared bands. Through multi-wavelength modeling, we determine a circumburst density of $n_0\approx10^{-3}~$cm$^{-3}$, supporting our previous suggestion that a low-density circumburst environment is conducive to the production of long-lasting reverse shock radiation in the radio band. We infer the presence of a large excess X-ray absorption column, $N_{\rm H} \approx 1.5\times10^{22}~$cm$^{-2}$, and a high rest-frame optical extinction, $A_{\rm V}\approx3.4~$mag. We identify a jet break in the X-ray light curve at $t_{\rm jet}\approx6~$d, and thus derive a jet opening angle of $\theta_{\rm jet}\approx4~$deg, yielding a beaming-corrected kinetic energy and radiated $\gamma$-ray energy of $E_{\rm K}\approx4\times10^{50}~$erg and $E_{\gamma}\approx1.3\times10^{51}~$erg ($1$-$10^4~$keV, rest frame), respectively. Consistency arguments connecting the forward and reverse shocks suggest a deceleration time of $t_{\rm dec} \approx 460~$s$~\approx T_{90}$, a Lorentz factor of $\Gamma(t_{\rm dec})\approx330$, and a reverse shock to forward shock fractional magnetic energy density ratio of $R_{\rm B}\equiv\epsilon_{\rm B,RS}/\epsilon_{\rm B,FS}\approx8$.
1607.08043 from 28 Jul 16
Haowei Xu et al.: Light speed variation from gamma ray burst GRB 160509A
It is postulated in Einstein's relativity that the speed of light in vacuum is a constant for all observers. However, the effect of quantum gravity could bring an energy dependence of light speed. Even a tiny speed variation, when amplified by the cosmological distance, may be revealed by the observed time lags between photons with different energies from astrophysical sources. From the newly detected long gamma ray burst GRB~160509A, we find evidence to support the prediction for a linear form modification of light speed in cosmological space.

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Jochen Greiner, last update: 28-Jul-2016 [Disclaimer]