- GCN Circular #32345
Aaron Tohuvavohu (U Toronto), James DeLaunay (UAlabama), Gayathri
Raman (PSU), Jamie A. Kennea (PSU), report:
Swift/BAT did not localize GRB 220708B onboard (T0:
2022-07-08T02:06:67 UTC, CALET trig #1341281218).
The CALET notice, distributed in near real-time, triggered the Swift
Mission Operations Center operated Gamma-ray Urgent Archiver for Novel
Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).
Upon trigger by this notice, GUANO sent a command to the Swift Burst
Alert Telescope (BAT) to save 90 seconds of BAT event-mode data from
[-45,+45] seconds around the time of the burst. All the requested
event mode data was delivered to the ground.
The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu,
arXiv:2111.01769), detects the burst in a 4.096 s analysis time bin
with a sqrt(TS) of 41.4.
The duration of the burst as seen by BAT is ~7 seconds.
A confident arcminute localization is found with DeltaLLHOut of 150
and a DeltaLLHPeak of 68.
See Section 9.1 and Figure 20 in the NITRATES paper for brief
descriptions and interpretations of sqrt(TS), DeltaLLHPeak, and
DeltaLLHOut.
The BAT position is
RA, Dec = 248.652, 36.338 deg which is
RA(J2000) = 16h 34m 36.48s
Dec(J2000) = +36d 20′ 16.8″
with an estimated uncertainty of 5 arcmin.
XRT and UVOT follow-up has been requested
Results of follow-up observations will be reported in future circulars.
GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.
A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/
- GCN Circular #32346
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Swift/BAT-GUANO GRB 220708B.
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021508
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Swift/BAT-GUANO event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a
GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
- GCN Circular #32350
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore
(U. Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) ,
M. Capalbi (INAF-IASFPA), B. Sbarufatti (PSU), 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
Swift/BAT-GUANO-detected burst GRB 220708B, collecting 1.7 ks of Photon
Counting (PC) mode data between T0+35.1 ks and T0+36.8 ks.
An uncatalogued X-ray source is detected and is above the RASS 3-sigma
upper limit at this position, and is therefore likely the GRB
afterglow. The position of this source is RA, Dec=248.5790, +36.3478
which is equivalent to:
RA (J2000): 16:34:18.97
Dec(J2000): +36:20:52.0
with an uncertainty of 4.0 arcsec (radius, 90% confidence). This
position is 3.6 arcmin from the Swift/BAT-GUANO position. The light
curve is consistent with a constant source of mean count rate 6.5e-02
ct/sec. A power-law fit gives an index of 0.0 (+0.0, -3.3).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.3 (+0.6, -0.5). The
best-fitting absorption column is 3.2 (+2.2, -1.7) x 10^21 cm^-2, in
excess of the Galactic value of 1.4 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 3.2 x 10^-11 (5.7 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 3.2 (+2.2, -1.7) x 10^21 cm^-2
Galactic foreground: 1.4 x 10^20 cm^-2
Excess significance: 2.9 sigma
Photon index: 2.3 (+0.6, -0.5)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00021508.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/ToO_GRBs/00021508.
This circular is an official product of the Swift-XRT team.
- GCN Circular #32355
S.Q. Jiang (NAOC), Z.P. Zhu (NAOC,HUST), S.Y. Fu , X. Liu, D. Xu (NAOC),
X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:
We observed the field of GRB 220708B detected by Swift/BAT-GUANO
(Tohuvavohu et al., GCN 32345) using the NEXT-0.6m telescope located at
Nanshan, Xinjiang, China. We obtained 10x200 s frames in the Sloan
r-band and 9x200 s frames in Sloan z-band, starting at 19:15:57.859 UT
on 2022-07-08,i.e.,17.15 hr after the BAT trigger.
No optical source is detected in our stacked images at the XRT
afterglow position (Osborne et al., GCN 32350), with upper limits as
follows:
T_mid-T0 (hr) Filter Upper limit(3-sigma)
17.42 r >21.60
17.96 z >19.54
calibrated with the nearby PanSTARRS field and not corrected for
Galactic extinction.
- GCN Circular #32356
K. Kobayashi (Waseda U), A. Yoshida, T. Sakamoto, S. Sugita (AGU),
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
Y. Asaoka (ICRR), S. Torii, Y. Akaike (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC),
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The long GRB 220708B (Swift/BAT-GUANO arcminute localization:
Tohuvavohu et al., GCN Circ. 32345) triggered the CALET Gamma-ray
Burst Monitor (CGBM) at 02:06:55.120 UTC on 8 July 2022
(http://cgbm.calet.jp/cgbm_trigger/flight/1341281218/index.html).
The burst signal was seen by all CGBM detectors.
The burst light curve shows a single pulse which starts
at T+2.6 sec, peaks at T+4.8 sec, and ends at T+6.5 sec.
The T90 and T50 durations measured by the SGM data are 3.4 +/- 0.3 sec
and 1.4 +/- 0.2 sec (40-1000 keV), respectively.
The ground processed light curve is available at
http://cgbm.calet.jp/cgbm_trigger/ground/1341281218/
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.
- GCN Circular #32358
D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin,
A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The long GRB 220708B (Swift/BAT-GUANO arcminute localization:
Tohuvavohu et al., GCN Circ 32345;
CALET-CGBM detection: Kobayashi et al., GCN Circ 32356)
triggered Konus-Wind (KW) at T0=7620.140 s UT (02:07:00.140).
The burst light curve shows two separated emission episodes.
The first episode (reported in GCNs 32345, 32356)
starts at ~T0-1 s and has a duration of ~4 s.
The second, much longer episode starts at ~T0-380 s and lasts to ~T0+450 s.
The emission is seen up to ~2 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB220708_T07620/
As observed by Konus-Wind, the burst had
a total fluence of (1.23 0.44)x10^-5 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 0.832 s,
of (2.03 0.39)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the first episode (measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 15 MeV range by a power law with exponential
cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.68(-0.22,+0.44) and Ep = 90(-9,+11) keV (chi2 = 77/97 dof).
Fitting this spectrum by a Band function yields the same values of alpha and Ep,
and an upper limit on the high energy photon index beta of -2.8 (chi2 = 76/96 dof).
The fluence in this time interval is (2.8 0.5)E-06 erg/cm^2.
The time-averaged spectrum of the second episode (measured from T0+377.088 to T0+450.816 s)
is best fit in the 20 keV - 15 MeV range by a CPL model
with alpha = -1.48(-0.31,+0.42) and Ep = 146(-45,+66) keV (chi2 = 90/98 dof).
A Band function fits the spectrum equally well with alpha = -1.20 (-0.56,+0.57),
beta = -2.29(-7.71, + 0.34), and Ep = 107 (-32, +68) keV (chi2 = 90/97 dof).
The fluence in this time interval is (9.5 3.9)E-06 erg/cm^2.
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
- GCN Circular #32359
D. Frederiks, on behalf of the Konus-Wind team:
The correct start time of the second episode of GRB 220708B reported in the KW GCN 32358 is T0+380 s.
We apologize for the typo and thank Jean-Luc Atteia for pointing this out.
- GCN Circular #32360
D. Turpin (CEA), C. Adami (LAM), B. Schneider,
E. Le Floch (CEA), S. Basa (LAM) report on behalf of
a larger collaboration:
We observed the field of GRB 220708B (Tohuvavohu et al. GCN 32345,
Kobayashi et al. GCN 32356, Frederiks et al. GCN 32358) using the T193cm
telescope at Observatoire de Haute-Provence (France) equipped with the
MISTRAL spectro-imager. Six exposures (6x600s) were obtained in the r band
using the bleu MISTRAL set-up from 2022 08 Jul 20:55:39 UT to 2022 08 Jul
22:14:27 UT (mid time ~19.5h after trigger). In the combined frame, we do not
detect any source within the 4 arcsec error circle of the XRT position
(Osborne et al. GCN 32350) down to the following 3-sigma limit:
r > 22.3 mag (AB)
The photometric calibration was performed using nearby stars
from the PanSTARRS catalog. The magnitude is not corrected
for Galactic extinction and it is consistent with the non-detections
reported by Jiang et al. (GCN 32355).
We express our deepest thanks to the Observatoire de Haute-Provence for its
support, in particular to Stphane Favard and Jrme Schmitt.
- GCN Circular #32363
V. Swain (IITB), H. Kumar (IITB), K. Angail (IAO), V. Bhalerao (IITB), G. C. Anupama (IIA), S. Barway (IIA) report on behalf of the GIT team:
We observed GRB 220708B detected by Swift (Tohuvavohu et al., GCN 32345; Evans et at., GCN 32350), CALET GBM (Kawakubo et al., GCN 32356) and Konus-Wind (Frederiks et al., GCN 32358), with the 0.7m GROWTH-India Telescope (GIT). The observations started at 21:04:33 UT on 2022-07-08, 18.96 hours after the Swift trigger. We obtained multiple 300-sec exposures in the g’, r' and i’ filters. We did not detect any new source in our stacked images within the 4 arcsec radius circle around R.A.= 16h 34m 18.97s, Dec.= +36d 20' 52.0” (Osborne et al. GCN #32350). The obtained upper limits follow as:
-------------------------------------------------------------------
JD (mid) | T_mid-T0(hrs) | Exposure (sec) | Filter | Lim_mag (5-sigma) |
-------------------------------------------------------------------
2459769.38578312 | 19.14 | 4 x 300 (stacked) | g' | > 21.03 |
2459769.39333163 | 19.32 | 4 x 300 (stacked) | r' | > 20.99 |
2459769.41415129 | 19.82 | 4 x 300 (stacked) | i' | > 19.83 |
-------------------------------------------------------------------
These upper limits are consistent with Jiang et al.(GCN #32355), Turpin et al.(GCN #32360). The magnitudes are calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction.
The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.
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