GRB 220907A
GCN Circular 32525
Subject
GRB 220907A: Fermi GBM Final Real-time Localization
Date
2022-09-07T14:15:57Z (3 years ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
The Fermi GBM team reports the detection of a likely SHORT GRB
At 14:05:26 UT on 7 Sep 2022, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 220907A (trigger 684252331.480966 / 220907587).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 269.6, Dec = -18.7 (J2000 degrees, equivalent to J2000 17h 58m, -18d 41'), with a statistical uncertainty of 6.9 degrees.
The angle from the Fermi LAT boresight is 75.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220907587/quicklook/glg_skymap_all_bn220907587.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220907587/quicklook/glg_healpix_all_bn220907587.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220907587/quicklook/glg_lc_medres34_bn220907587.gif
GCN Circular 32526
Subject
GRB 220907A: Swift detection of a burst
Date
2022-09-07T14:24:33Z (3 years ago)
From
Kim Page at U.of Leicester <kimlpage1978@gmail.com>
K. L. Page (U Leicester), P. A. Evans (U Leicester),
R. A. J. Eyles-Ferris (U Leicester), J.D. Gropp (PSU),
J. A. Kennea (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII),
H. A. Krimm (NSF), N. P. M. Kuin (UCL-MSSL),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL),
B. Sbarufatti (INAF-OAB), M. H. Siegel (PSU),
A. Tohuvavohu (U Toronto) and M. A. Williams (PSU) report on behalf of
the Neil Gehrels Swift Observatory Team:
At 14:05:25 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 220907A (trigger=1123129). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 268.870, -20.315 which is
RA(J2000) = 17h 55m 29s
Dec(J2000) = -20d 18' 54"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a complex peak
structure with a duration of about 20 sec. The peak count rate
was ~2000 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 14:06:56.5 UT, 90.7 seconds after
the BAT trigger. No source was detected in 188 s of promptly downlinked
data. We are waiting for the full dataset to detect and localise the
XRT counterpart.
No prompt UVOT data products are available.
Although there is no counterpart found in the (short) XRT exposure,
the high significance of the BAT detection (8.5 sigma) and the
simultaneous detection by Fermi/GBM (GCN #32525)
indicates that this is an astrophysical event.
Burst Advocate for this burst is K. L. Page (kimlpage1978 AT gmail.com).
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/)
GCN Circular 32527
Subject
GRB 220907A: Swift-XRT position
Date
2022-09-07T17:09:56Z (3 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
K. L. Page and P. A. Evans (U Leicester) reports on behalf of the
Swift-XRT team:
We have analysed 678 s of XRT data for GRB 220907A (Page et al. GCN Circ.
32526), from 74 s to 4.1 ks after the BAT trigger. An X-ray source is now
detected within the BAT error circle. The refined XRT position is RA, Dec
= 268.8714, -20.2879 which is equivalent to:
RA (J2000): 17 55 29.14
Dec(J2000): -20 17 16.6
with an uncertainty of 5.0 arcsec (radius, 90% confidence).
This circular is an official product of the Swift-XRT team.
GCN Circular 32530
Subject
GRB 220907A: Swift-XRT refined Analysis
Date
2022-09-08T07:04:49Z (3 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
K. L. Page (U Leicester) reports on behalf of the Swift-XRT team:
We have analysed 5.6 ks of XRT data for GRB 220907A (Page et al. GCN
Circ. 32526), from 100 s to 21.5 ks after the BAT trigger. The data
are entirely in Photon Counting (PC) mode. Using 188 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 = 268.87315, -20.28950 which is equivalent to:
RA (J2000): 17h 55m 29.56s
Dec(J2000): -20d 17' 22.2"
with an uncertainty of 4.0 arcsec (radius, 90% confidence). The source
is fading with alpha >0.4.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01123129.
This circular is an official product of the Swift-XRT team.
GCN Circular 32531
Subject
GRB 220907A: Swift/UVOT Upper Limits
Date
2022-09-08T12:26:27Z (3 years ago)
From
Samantha Oates at MSSL <samantha.oates@alumni.ucl.ac.uk>
S. R. Oates (U. Birmingham) and K. L. Page (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 220907A
95 s after the BAT trigger (Page et al., GCN Circ. 32526).
No optical afterglow consistent with the enhanced XRT position
(Page and Evans GCN Circ. 32530)
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white_FC 95 245 147 >20.2
white 95 5001 298 >20.6
v 3823 4023 197 >18.6
b 4644 4844 197 >19.7
u 4438 4638 197 >19.4
w1 4234 4433 197 >19.2
m2 4028 4228 197 >19.2
w2 3618 3818 197 >19.2
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 1.637 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 32532
Subject
GRB 220907A: Nanshan/NEXT optical upper limits
Date
2022-09-08T13:04:59Z (3 years ago)
From
Zipei Zhu at NAOC <zpzhu@nao.cas.cn>
Z.P. Zhu (NAOC,HUST), S.Y. Fu(NAOC), S.Q. Jiang, X. Liu, T.H. Lu, D. Xu, X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:
We observed the field of GRB 220907A detected by Swift (Page et al., GCN 32526) and Fermi/GBM (GCN 32525) using the NEXT-0.6m telescope located at Nanshan, Xinjiang, China. We obtained a series of frames in the Sloan r-band and Sloan z-band, starting at 14:07:13 UT on 2022-09-07, i.e., 108s after the BAT trigger.
No uncatalogued optical source is detected in our stacked images at the XRT position (Page eta al., GCN32527), with upper limits as follows:
T_mid-T0 (min) Filter Upper limit(3-sigma)
15.5 r >19.5
34.5 z >18.1
calibrated with the nearby PanSTARRS field and not corrected for Galactic extinction.
GCN Circular 32533
Subject
GRB 220907A: Fermi GBM observation
Date
2022-09-08T14:27:54Z (3 years ago)
From
Peter Veres at UAH <veresp@gmail.com>
S. Dalessi, C. Meegan and P. Veres (all UAH)
report on behalf of the Fermi GBM Team:
"At 14:05:26.48 UT on 07 September 2022, the Fermi Gamma-Ray Burst
Monitor (GBM) triggered and located GRB 220907A (trigger 684252331 /
220907587), which was also detected by the Swift/BAT (Page et al.
2022, GCN 32526, 32530). The Fermi GBM Final Real-time Localization
(GCN 32525) is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 50 degrees.
The GBM light curve shows a single peak with a duration (T90) of about
9 s (50-300 keV). The time-averaged spectrum from T0-2.8 s to T0+5.4 s
is best fit by a power law function with index = -1.48 +/- 0.07.
The event fluence (10-1000 keV) in this time interval is (1.13 +/-
0.12)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from
T0+1.02 s in the 10-1000 keV band is 2.32 +/- 0.24 ph/s/cm^2.
A power law function with an exponential high-energy cutoff fits the
spectrum equally well. The power law index is -1.01 +/- 0.29 and the
cutoff energy, parameterized as Epeak, is 320 +/- 170 keV and fluence
(1.02 +/-0.22)E-6 erg/cm^2.
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 32537
Subject
GRB 220907A: Swift-BAT refined analysis
Date
2022-09-08T20:58:07Z (3 years ago)
From
Hans Krimm at NSF/NASA-GSFC <hkrimm@nsf.gov>
M. Stamatikos (OSU), S. D. Barthelmy (GSFC), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC),
T. Sakamoto (AGU), (i.e. the Swift-BAT team):
Using the data set from T-240 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 220907A (trigger #1123129)
(Page, et al., GCN Circ.32526). The BAT ground-calculated position is
RA, Dec = 268.869, -20.303 deg which is
RA(J2000) = 17h 55m 28.6s
Dec(J2000) = -20d 18' 10.8"
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 90%.
The mask-weighted light curve shows a single peak of ten seconds approximate
duration starting at T-1 sec. A spacecraft maneuver took the source out of the BAT
field of view at approximately 400 seconds. T90 (15-350 keV) is 8.49 +- 1.56 sec
(estimated error including systematics).
The time-averaged spectrum from T-0.60 to T+10.29 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
0.99 +- 0.24. The fluence in the 15-150 keV band is 4.1 +- 0.6 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.70 sec in the 15-150 keV band
is 1.0 +- 0.2 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/1123129/BA/