- GCN Circular #13487
K. Hurley, and J. Goldsten, on behalf of the MESSENGER GRNS GRB team,
S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks,
D. Svinkin, and T. Cline on behalf of the Konus-Wind team,
V. Connaughton, M. Briggs, and C. Meegan, on behalf of the Fermi
GBM team,
A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo, and C.
Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, and
K. Yamaoka, M. Ohno, Y. Hanabata, Y. Fukazawa, T. Takahashi, M. Tashiro,
Y. Terada, T. Murakami, and K. Makishima on behalf of the Suzaku WAM
team, report:
The long-duration GRB 120716A has been observed by Fermi (GBM: trigger
364151106), Konus-Wind, INTEGRAL (SPI-ACS), Suzaku (WAM), and MESSENGER
(GRNS), so far, at about 61504 s UT (17:05:04).
The burst light curve shows a short initial pulse followed in ~170 s
period of quiescence by two long pulses with a total duration of ~60 s.
We have triangulated both emission episodes and have revealed that they
came from the same direction.
We have localized the burst to a preliminary, 3 sigma error box whose
coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
313.089 (20h 52m 21s) +9.558 ( +9d 33' 28")
Corners:
311.595 (20h 46m 23s) +9.913 ( +9d 54' 46")
313.791 (20h 55m 10s) +10.049 (+10d 02' 56")
314.615 (20h 58m 28s) +9.110 ( +9d 06' 36")
312.407 (20h 49m 38s) +9.046 ( +9d 02' 45")
---------------------------------------------
The error box area is 2.04 sq. deg, and its maximum dimension is 3.1 deg.
This box can be improved.
A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB120716_T61507/IPN/
The time history and spectrum will be given in a forthcoming GCN Circular.
- GCN Circular #13488
S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin,
P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf
of the Konus-Wind team, report:
The long-duration unusual GRB 120716A
(IPN detection and localization: Hurley at al., GCN 13487)
triggered Konus-Wind at T0=3D61507.357s UT (17:05:07.357)
The light curve started with a short (~0.9 s) pulse followed,
after ~170 s, by a double-peaked structure lasting for ~60 s.
The total duration of the burst is ~230 s.
This GRB is similar to GRB 041219A, GRB 050820A, and GRB 060124,
which display a rather short precursor, a ~200 s long period
of quiescence, and the main episode of emission. For this burst,
the precursor is relatively short and bright and the main part
is shorter and dimmer.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB120716_T61507/
As observed by Konus-Wind:
- the precursor had a fluence of 1.4(-0.3,+1.0)x10-6 erg/cm2,
and a 64-ms peak flux, measured from T0-0.064 s,
of 3.3(-0.8,+2.7)x10-6 erg/cm2/s;
- the main part of the burst
had a fluence of 1.3(-0.3,+0.3)x10-5 erg/cm2,
and a 256-ms peak flux, measured from T0+181.760 s,
of 8.8(-0.15,+0.15)x10-7 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The 3-channel spectrum of the precursor (from T0-0.256 to T0+0.512 s)
can be modeled (in the 20-1200 keV range) by a power law
with exponential cutoff model with alpha =3D -1.3 =B1 0.1
and Ep =3D 380 =B1 50 keV (one-sigma errors are given for this fit).
The time-integrated spectrum of the main emission episode
(measured from T0+172.288 to T0+213.248 s)
is well fit in the 20 keV - 5 MeV range
by a power law with exponential cutoff model, for which:
alpha =3D -1.50 (-0.2, +0.2),
and Ep =3D 190(-44, +110) keV,
chi2 =3D 59.2/75 dof.
Fitting this spectrum with the GRB (Band) function yields
the following model parameters:
the low-energy photon index alpha =3D -1.5 (-0.2, +0.3),
the high energy photon index beta =3D -2.4 (<-2.0),
the peak energy Ep =3D 175(-73, +96) keV,
chi2 =3D 58.2/74 dof.
The spectrum at the maximum count rate
(measured from T0+180.480 to T0+188.672 s) is best fitted
is best fit in the 20 keV - 5 MeV range
by a power law with exponential cutoff model, for which:
alpha =3D -1.1 (-0.3, +0.3),
and Ep =3D 180(-37, +68) keV,
chi2 =3D 66.5/75 dof.
All the quoted results are preliminary.
All the quoted errors are at the 90% confidence level.
- GCN Circular #13489
S. B. Cenko (UC Berkeley), E. O. Ofek (Weizmann Institute of Science), and
P. E. Nugent (Lawrence Berkeley National Laboratory / UC Berkeley) report
on behalf of a larger collaboration:
We have imaged the location of the IPN GRB 120716A (Hurley et al., GCN
13487) with the Palomar 48 inch Oschin Schmidt telescope as part of the
Palomar Transient Factory (PTF). Images were obtained in the r' filter
beginning at 4:25 UT on 18 July 2012 (~ 1.5 d after the IPN trigger).
Within the IPN localization, we identify a new point source with
coordinates:
RA: 20:52:12.10 Dec: +09:35:53.7 (J2000.0)
Using several nearby stars from the Sloan Digital Sky Survey for
reference, we measure a magnitude of r' ~ 20.4 at this time.
Nothing is detected at this location in previous PTF imaging of this
field, with images beginning in June 2011. Furthermore, no source is
detected in archival SDSS imaging of this location (a faint nearby object
in the SDSS database, SDSS J205212.01+093551.9, appears to be of very low
significance). However, our most recent epoch of PTF imaging was obtained
in March 2012, so we cannot currently rule out the chance alignment of an
unassociated foreground or background transient.
Further observations of this candidate optical afterglow are planned.
- GCN Circular #13490
D. Xu (WIS), N. Groeneboom, K. Mikkelsen (U. Oslo) report on behalf of
a larger collaboration:
We observed the field of the candidate optical afterglow (Cenko et
al., GCN 13489) of GRB 120716A (Hurley et al., GCN 13487), using the
2.5m Nordic Optical Telescope (NOT) equipped with ALFOSC. Observations
started 04:03 UT on 2012-07-19 (i.e., 2.455 days after the IPN
trigger) and 5x300s SDSS r'-band images were obtained in a seeing of
~0.7".
The optical source reported in GCN 13489 is well detected in each NOT
image at coordinates
RA(J2000)=20:52:12.17
Dec(J2000)=+09:35:53.9
with an uncertainty of ~0.1 arcsec radius, being consistent with the
PTF position.
The source had r(AB)=20.10+/-0.04, calibrated with nearby SDSS stars.
The decay between the PTF and NOT epochs indicates that the source may
be the optical afterglow of GRB 120716A.
- GCN Circular #13491
D. Xu (WIS) reports
The magnitude in GCN 13490 should be r'(AB)=21.00 rather than
r'(AB)=20.10. Otherwise there would be no decay compared with the
previous PTF magnitude of r'~20.4. Thanks to Brad Cenko for pointing
out this.
- GCN Circular #13492
P. Schady (MPE Garching), M. Nardini (Universita degli studi di
Milano-Bicocca ) and J. Greiner (MPE Garching) report on behalf of the
GROND team:
We observed the field of GRB 120716A (Hurley et al., GCN #13487) at the
position of the afterglow candidate (Cenko et al., GCN #13489)
simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120,
405) mounted at the 2.2 m MPG/ESO telescope at La Silla Observatory
(Chile).
Observations started at 05:07 UT on 2012-07-19, 2.5 days after the GRB
trigger. They were performed at an average seeing of 1.4" and at an
average airmass of 1.3.
We found a single point source at a position consistent the afterglow
candidate reported in Cenko et al. (GCN #13489) and Xu et al. (GCN
#13490). Based on the first 460s of total exposures in g'r'i'z' and 480 s
in JHK, we estimate preliminary magnitudes (all in AB system) of
g' = 21.8 +- 0.1 mag,
r' = 20.9 +- 0.1 mag,
i' = 20.5 +- 0.1 mag,
z' = 20.3 +- 0.1 mag,
J = 19.9 +- 0.2 mag,
H = 19.6 +- 0.2 mag and
K = 18.8 +- 0.5 mag
The optical/NIR SED is well fit by a power-law with a spectral slope of
~1.3, typical for GRB afterglows, confirming this to be the afterglow of
GRB120716A.
Given magnitudes are calibrated against SDSS zeropoints as well as 2MASS
field stars and are not corrected for the expected Galactic foreground
extinction corresponding to a reddening of E_(B-V)=0.07 mag in the
direction of the burst (Schlegel et al. 1998).
- GCN Circular #13493
Jochen Greiner, Arne Rau, Patricia Schady (all MPE), Ivo Saviane (ESO),
and Brad Cenko (UC Berkeley) report on behalf of a larger collaboration.
We observed the afterglow candidate of GRB 120716A (Hurley et al., GCN
13454; Cenko et al. GCN 13489; Xu et al, GCN 13490; Schady et al. CGN
13492) with the ESO VLT equipped with the FORS2 spectrograph.
Observations with the 600B grism, covering a spectral range of
350-610nm) started at ~06:54 UT on July 19th 2012 (~58.2 hr after the
gamma-ray trigger) and lasted for ~ 1.5hr.
The spectrum shows a prominent, broad absorption trough centered at
~4250A, interpreted as Lyman-alpha, together with numerous metal lines
(SiII, OI, SiIV, CIV) at longer wavelength. We find a common redshift of
these features of z=2.48.
- GCN Circular #13494
V. D'Elia (ASDC/INAF-OAR), P. Goldoni (APC,CEA/Irfu),
D. Xu (WIS), T. Kruehler, J. P. U. Fynbo, D. Malesani (DARK/NBI), O.E.
Hartoog (UvA, Netherland), N. R. Tanvir (U. of Leicester)
report on behalf of the X-shooter GRB GTO collaboration:
We observed the GRB 120716A (Hurley et. al GCN 13487) optical counterpart
(Cenko et al. GCN 13489, Xu et al. GCN 13490, Schady et al. GCN 13492) with
X-shooter at the VLT (Paranal, Chile). Observations started on 19 July
at 8:40 UT
(2.6 days after the burst) and consisted of a total observing
time of 3600 s in each of the UVB, VIS and NIR arms, covering the range
between 3000 and 18000 A.
The spectrum shows a broad absorption trough at ~4250A which we interpret
as due to Lyman-alpha. At the same redshift z=3D2.486 we detect plenty of
metal
absorption lines, such as (CII, SiII, OI, FeII, CIV, SiIV), fine
structure (CII*, SiII* FeII*) and metastable (NiII) lines.
We thus confirm the redshift reported by Greiner et al. (GCN 13493).
We acknowledge excellent support from the ESO staff, in particular Dimitri
Gadotti, Lorena Faundez, Fernando Selman and Jonathan Smoker.
- GCN Circular #13495
D. Xu (WIS) reports on behalf of a larger collaboration:
The Swift satellite observed the field of the decaying optical
transient (Cenko et al. GCN 13489; Xu et al. GCN 13490; Schady et al.
GCN 13492), which is very likely the optical afterglow of GRB 120716A
(Hurley et al., GCN 13487). Initial observation started at 12:47 UT
and ended at 13:12 UT on 2012-07-19 (i.e., a median time of 2.83 d
after the IPN trigger), and consisted of a total observing time of
1470s for Swift/XRT.
Preliminary XRT data reduction reveals a S/N~2 source at coordinates
RA(J2000) = 20:52:12.4
Dec(J2000) = +09:35:51.1
with an uncertainty of 7.7 arcsec radius, being consistent with the
position of the optical source. Currently we don't know whether the
X-ray source is decaying or not.
We thank the Swift team for carrying out a quick ToO observation.
- GCN Circular #13496
V. D'Elia (ASDC), J. Gelbord and J. Kennea (PSU) report on behalf of
the Swift-XRT team:
Swift began a target of opportunity observation of GRB120716A on July
19, 2012 at 14:22 UT, approximately 2.9 days after the discovery
(Hurley et al. GCN 13487). Swift data for these observations utilize
Target ID 20225.
Preliminary analysis of the 1.5 ks downlinked XRT data finds an
uncatalogued X-ray source at RA, Dec =3D 313.05050, 9.59850 which is
equivalent to:
RA(J2000) =3D =A020h 52m 12.12s
Dec(J2000)=3D +09d 35m 54.6s,
with an error radius of 3.4 arcsecs (position enhanced by UVOT field
astrometry).
The above position is consistent with the optical afterglow detection
reported by Cenko et al. (GCN 13489), Xu et al. (GCN 13490), Schady et
al. (GCN 13492). In addition, no known X-ray object is present at the
XRT coordinates, so this is likely the X-ray afterglow of GRB120716A.
The count rate of the XRT source is 8.32E-03+/-2.9E-03 cts/s. We
cannot determine at the present time whether the
source is fading.
This circular is an official product of the Swift-XRT team.
- GCN Circular #13497
A. Zauderer, T. Laskar, A. Soderberg and E. Berger (Harvard) report on
behalf of a larger collaboration:
"We observed the position of GRB 120716A (Hurley et al.; GCN 13487) with
the EVLA beginning 2012 July 19.26 (dt ~ 2.5 d). At a mean frequency of
6 and 22 GHz, we detect a radio source (10 and 6 sigma, respectively)
consistent with optical candidates (e.g. Cenko et al.; GCN 13489) and
the Swift-XRT detection (D'Elia et al.; GCN 13496).
Followup observations are planned."
- GCN Circular #13498
David Gruber (MPE) and Adam Goldstein (UAH)
report on behalf of the Fermi GBM Team:
"At 17:05:03.91 UT on 16 July 2012, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 120716A (trigger 364151106 / 120716712).
This burst was localized by the IPN (Hurley et al., GCN 13487).
The GBM on-ground calculated location is consistent with the
IPN location.
The angle from the Fermi LAT boresight is 63 degrees.
This burst was also independently detected by INTEGRAL SPI-ACS.
The GBM light curve consists of a bright precursor, followed
by a double-peaked main emission after ~ 160 s.
The duration (T90) is about 234 s (50-300 keV).
The time-averaged spectrum of the precursor is best fit by
a power law function with an exponential
high-energy cutoff. The power law index is -0.84 +/- 0.11 and
the cutoff energy, parameterized as Epeak, is 173 +/- 18 keV.
A Band function fits the spectrum equally well
with Epeak= 115 +/- 19 keV, alpha = -0.48 +/- 0.22 and beta = -2.19 +/- 0.17.
The time-averaged spectrum of the main emission is best fit by
a Band function with Epeak= 114 +/- 12 keV, alpha = -1.00 +/- 0.08
and beta= -2.08 +/- 0.07.
The event fluence (10-1000 keV) is (1.47 +/- 0.01)E-05 erg/cm^2.
The 1-sec peak photon flux measured starting from T0-0.13 s
in the 10-1000 keV band is 8.37 +/- 0.32 ph/s/cm^2.
Using the redshift of 2.48 (Greiner et al., GCN 13493; D'Elia et al., GCN 13494)
and a standard cosmology model with H_0 = 71 km/s/Mpc, Omega_M = 0.27,
Omega_Lambda = 0.73, this corresponds to an isotropic
energy release of ~ 3E+53 erg.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
- GCN Circular #13518
V. Rumyantsev, N. Pit (CrAO), A. Pozanenko (IKI) report on behalf of larger
GRB follow-up collaboration:
We observed the region of optical afterglow (Cenko et al., GCN 13489) of
IPN localized GRB 120716A (Hurley et al., GCN 13487) with AZT-11 telescope
of CrAO observatory starting on July 19 (UT) 18:51 under seeing of about
3.3 arsces. We do not detected optical afterglow up to R=20.8. The
photometry is based on the USNO-B1.0 star 0996-0576906 (20 52 01.46 +09 36
17.8) assuming R=15.97:
T0+ Filter, Exposure, OT, uplim (3 sigma)
(mid, d) (s)
2.0972 R 22x180 n/d 20.8
- GCN Circular #13523
A. Pozanenko (IKI), A. Sergeev (Institute of Radio Astronomy NASU), A.
Volnova (SAI MSU), O. Burhonov (UBAI), I. Molotov (KIAM) report on behalf of
larger GRB follow-up collaboration:
We observed the region of the optical afterglow (Cenko et al., GCN 13489)
of IPN localized GRB 120716A (Hurley et al., GCN 13487) with AZT-22
telescope of Maidanak observatory on Jul. 19 (UT) 17:57:06 and Jul. 21
(UT) 18:46:16 under mean seeing of about 0.6 arcsec. Totally we obtained 8
images of 600 s exposure in R filter. In each particular image we clearly
see the optical afterglow (Cenko et al., GCN 13489; Xu et al., GCN 13490;
Schady et al., GCN 13492) in coordinates (J2000) 20:52:12.15 +09:35:54.2
(uncertainty of 0.13 arcsec in both coordinates).
Preliminary photometry of the afterglow is based on USNO-B1.0 nearby stars:
T0+ Filter, Exposure, OT
(mid, d) (s)
date t_start (UT) filter exp,s OT
2012-07-19 17:57:06 R 4*600 20.71+/-0.04
2012-07-21 18:46:16 R 4*600 21.01+/-0.04
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