GRB 210802A
GCN Circular 30622
Subject
GRB 210802A: Further Swift/XRT observation and afterglow confirmation
Date
2021-08-09T13:55:33Z (5 years ago)
From
Valerio D'Elia at ASDC <valerio.delia@ssdc.asi.it>
V. D'Elia (ASI-SSDC & INAF-OAR) and S.B. Cenko (GSFC) report on behalf of the Swift-XRT team:
Swift-XRT has performed further follow-up observations of the Fermi burst (Longo et al., GCN Circ. 30589; Roberts et al., GCN Circ. 30590).
The possible afterglow reported in Sbarufatti et al. (GCN Circ. 30591, "source 7") is no longer detected in a 4 ks observation, down to a three sigma upper limit of 4.8E-3 cts/s (corresponding to 1.28E-13 erg/cm^2/s) at the position of the transient. This value is significantly below the previously reported flux value for the candidate, thus confirming ���source 7��� as the afterglow of GRB 210802A.
The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/xrt_curves/00021456/.
This circular is an official product of the Swift-XRT team.
GCN Circular 30596
Subject
GRB 210802A: MITSuME Okayama optical upper limits
Date
2021-08-04T12:26:45Z (5 years ago)
From
Ryohei Hosokawa at Tokyo Institute of Technology <hosokawa@hp.phys.titech.ac.jp>
R. Hosokawa, N. Ito, Y. Imai, K. L. Murata, M. Niwano, H. Takamatsu,
R. Noto, S. Sato, M. Takaku, R. Yamaguchi, Y. Yatsu, and N. Kawai
(TokyoTech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 210802A (V. Lipunov et al. GCN Circular
#30586, P. A. Evans et al. GCN Circular #30587, F. Longo et al. GCN
Circular #30589, O.J. Roberts et al. GCN Circular #30590, B.
Sbarufatti et al. GCN Circular #30591, Y.-D. Hu et al. GCN Circular
#30592, Alan M. Watson et al. GCN Circular #30593) with the optical
three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm
telescope Okayama. The observation with a series of 60 sec exposures
started at 2021-08-03 10:34:24 UT (14.4 hours after Fermi trigger). We
stacked the images with good conditions. We did not detect any
uncatalogued sources within the XRT error region (B. Sbarufatti et al.
GCN Circular #30591). We obtained the 5-sigma limits of the stacked
images as follows.
T0+[hour] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
15.8 2021-08-03 11:54:24 1080 Rc>17.2, Ic>16.9
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used PS1 catalog for flux calibration.
The magnitudes are expressed in the AB system.
The images were processed in real-time through the MITSuME GPU
reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages
4-24; https://github.com/MNiwano/Eclaire).
GCN Circular 30593
Subject
GRB 210802A: DDOTI Upper Limits
Date
2021-08-04T00:14:44Z (5 years ago)
From
Alan M Watson at UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Nat Butler (ASU), Eleonora Troja (GSFC/UMD), Rosa L.
Becerra (UNAM), Simone Dichiara (GSFC/UMD), Alexander Kutyrev (GSFC/UMD),
William H. Lee (UNAM), Diego Gonzalez (UNAM), Oc��lotl Lopez (UNAM), Margarita
Pereyra (UNAM), and Srihari Ravi (ASU) report:
We observed the field of the Fermi GBM/LAT event GRB 210802A (Longo et al., GCN
Circ., 30589; Roberts et al., GCN Circ., 30590) with the DDOTI wide-field imager
at the Observatorio Astron��mico Nacional on Sierra San Pedro Martir (
http://ddoti.astroscu.unam.mx) from 2021-08-03 03:35 to 07:37 UTC (7.45 to 11.48
hours after the trigger).
We observed a region of about 14 degrees in RA by 10 degrees in declination,
with a 1 x 2 grid of pointings centered on the Fermi GBM Final Position
15:19:40.80 +30:18:00.0 (J2000) and including the entire LAT uncertainty region
(Longo et al., GCN Circ., 30589). We obtained about 105 minutes exposure on the
LAT uncertainty region. We obtained AB photometry by calibration against the
APASS catalog.
Comparing to the Pan-STARRS DR1 catalog, we detect no uncatalogued point sources
in the LAT uncertainty region to a 10-sigma limiting magnitude of w = 21.0.
At the position of the candidate X-ray afterglow (Sbarufatti et al., GCN Circ.,
30591), we detect no point source to a 5-sigma limiting magnitude of w = 21.8.
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro M��rtir.
GCN Circular 30592
Subject
GRB 210802A: BOOTES-2/TELMA optical upper limit
Date
2021-08-03T22:25:19Z (5 years ago)
From
Youdong HU at IAA-CSIC <huyoudong072@hotmail.com>
Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia, A. J. Castro-Tirado, M.D. Caballero-Garcia (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), R. Fernandez-Munoz (IHSM/UMA-CSIC) and M. Jelinek (ASU-CAS), on behalf of a larger collaboration, report:
Following the Fermi trigger of GRB 210802A (Longo GCNC 30589, Roberts et al. GCNC 30590), we triggered the 60cm BOOTES-2/TELMA robotic telescope at IHSM La Mayora (UMA-CSIC) in Algarrobo Costa (Malaga, Spain) after the twilight as soon as it was possible. Useful images were taken only after 20:12 UT on 03 Aug (~1 day after trigger). In the co-added 12 x 60 s exposure image (clear filter), no optical afterglow is detected within the X-ary afterglow position reported by XRT/Swift (Sbarufatti et al. GCNC 30591) down to 20.3 mag.
We thank the staff at La Mayora for its excellent support.
GCN Circular 30591
Subject
GRB 210802A: Swift-XRT afterglow detection
Date
2021-08-03T19:23:02Z (5 years ago)
From
Valerio D'Elia at ASDC <valerio.delia@ssdc.asi.it>
B. Sbarufatti (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E.
Ambrosi (INAF-IASFPA) , D.N. Burrows (PSU), J. D. Gropp (PSU) 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 210802A (Longo et al. GCN Circ. 30589) in
a series of observations tiled on the sky. The total exposure time is
5.2 ks, distributed over 4 tiles; the maximum exposure at a single sky
location was 2.3 ks. The data were collected between T0+41.7 ks and
T0+43.0 ks, and are entirely in Photon Counting (PC) mode.
Twenty-eight uncatalogued X-ray sources are detected. Many of these
sources are in the bottom tile (likely a high background effect), and
in the left tile (possibly an extended emission related to a nearby
cluster of galaxies). One of the most significant sources ("Source 7")
is above the 2SXPS 3-sigma upper limit at this position, and is
therefore likely the GRB afterglow. Using 1246 s of PC mode data and 1
UVOT image, we find an enhanced XRT position (using the XRT-UVOT
alignment and matching UVOT field sources to the USNO-B1 catalogue):
RA, Dec = 230.72285, +29.90180 which is equivalent to:
RA (J2000): 15h 22m 53.48s
Dec(J2000): +29d 54' 06.5"
with an uncertainty of 3.5 arcsec (radius, 90% confidence). This
position is 9.8 arcmin from the Fermi/LAT position. While we cannot
determine at the present time whether the source is fading, we note
that a previous 1 ks Swift-XRT visit of the field showed no sign of
Source 7 (https://www.swift.ac.uk/2SXPS/Fields/10000004351).
The results of the XRT-team automatic analysis of the likely afterglow
are at https://www.swift.ac.uk/xrt_products/TILED_GRB00100/Source7.php.
The results of the full analysis of the tiled XRT observations are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00100.
This circular is an official product of the Swift-XRT team.
GCN Circular 30590
Subject
GRB 210802A: Fermi GBM detection
Date
2021-08-03T14:58:46Z (5 years ago)
From
Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>
O.J. Roberts (USRA/NASA-MSFC) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 20:08:06.49 UT on 02 August 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210802A (trigger 649627691 / 210802839), which was
also detected by Fermi-LAT (F. Longo et al. 2021, GCN 30589).
The Fermi GBM on-ground location is consistent with the LAT position.
The angle from the Fermi LAT boresight at the GBM trigger time is 51 degrees.
The GBM light curve consists of multiple bright pulses
with a duration (T90) of about 11 s (50-300 keV).
The time-averaged spectrum from T0-0.3 s to T0+12.8 s is
well fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.66 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 372 +/- 12 keV.
The event fluence (10-1000 keV) in this time interval is
(2.10 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+6.6 s in the 10-1000 keV band
is 16.4 +/- 0.3 ph/s/cm^2.
A Band function fits the spectrum equally well
with Epeak= 365 +/- 15 keV, alpha = -0.65 +/- 0.03 and beta = -3.22 +/- 0.75.
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 30589
Subject
GRB 210802A: Fermi-LAT detection
Date
2021-08-03T13:12:38Z (5 years ago)
From
Magnus Axelsson at Stockholm U. <magaxe@kth.se>
F. Longo (University and INFN, Trieste), M. Arimoto (Kanazawa Univ.), E. Bissaldi (Politecnico and INFN, Bari), M. Axelsson (KTH & Stockholm Univ.) and M. Ohno (Hiroshima Univ. & E��tv��s Univ.) report on behalf of the Fermi-LAT Collaboration:
On 2 August 2021, Fermi-LAT detected high-energy emission from GRB 210802A which was also detected by Fermi-GBM (trigger 649627691/210802839). The best LAT on-ground location is found to be
RA, Dec = 230.9, 29.8 (degrees, J2000)
with an error radius of 0.35 deg (90% containment, statistical error only). This was 51 deg from the LAT boresight at the time of the GBM trigger:
T0 = 20:08:06.49 UT.
The data from the Fermi-LAT show a significant increase in the event rate after the GBM trigger that is spatially and temporally correlated with the GBM emission with high significance.
The photon flux above 100 MeV in the time interval 0-1000 s after the GBM trigger is (1.0 +/- 0.3) E-5 ph/cm2/s.
The estimated photon index above 100 MeV is -2.3 +/- 0.3.
The highest-energy photon is a 1.4 GeV event which is observed 3 seconds after the GBM trigger.
A Swift ToO has been approved for this burst.
The Fermi-LAT point of contact for this burst is Elisabetta Bissaldi (elisabetta.bissaldi@ba.infn.it<mailto:elisabetta.bissaldi@ba.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 30587
Subject
GRB 210802A: Tiled Swift observations
Date
2021-08-03T07:42:50Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
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 210802A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00100
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.