GRB 210912A
GCN Circular 30861
Subject
GRB 210912A: LBT optical observations
Date
2021-09-22T11:41:40Z (4 years ago)
From
Andrea Melandri at INAF-OAB <andrea.melandri@inaf.it>
A. Rossi (INAF-OAS Bologna) report on behalf of the CIBO collaboration:
We observed the field of GRB 210912A (Troja et al., GCN 30820) in the r' band with the LBC imager mounted on LBT (Mt Graham, AZ, USA). We obtained 10min of imaging at the midtime 11:20 UT on 2021-09-17 (~5 days after the burst trigger).
We clearly detect the optical afterglow (Hu et al., GCN 30823; Pankov et al., GCN 30825; Kuin & Troja, GCN 30832; Kann et al. GCN 30834; Nicuesa Guelbenzu et al. GCN 30837) with the following preliminary AB magnitude:
r = 22.73 +- 0.05
calibrated against Pan-STARRS field stars. It is likely that this flux is significantly affected by host galaxy contamination (Kann et al. GCN 30829).
We acknowledge the excellent support from the LBTO and LBT-INAF staff, particularly A. Cardwell, J. Williams and D. Paris, in obtaining these observations.
GCN Circular 30844
Subject
GRB 210912A: BOOTES-5/JGT optical afterglow candidate (Correction to GCNC 30823)
Date
2021-09-17T11:55:37Z (4 years ago)
From
Youdong HU at IAA-CSIC <huyoudong072@hotmail.com>
Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia, A. J. Castro-Tirado, R. Sanchez-Ramirez and M.D. Caballero-Garcia (IAA-CSIC), D. Hiriart and W. H. Lee (UNAM), C. J. Perez del Pulgar and I. Carrasco (UMA), I. H. Park (SKKU) on behalf of a larger collaboration, report:
The 60cm BOOTES-5/JGT robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically responded in 13 s to the Swift trigger for GRB 210912A (Troja et al., GCNC 30820). In the co-added clear image (30 x 1 s), we find an uncataloged optical source at (J2000) coordinates RA: 8:39:34.30, DEC:+79:13:17.5, which is located at the edge of the XRT error box (Troja et al., GCNC 30820) and for which we measure R = 18.5 mag. We propose this source to be the GRB 210912A optical afterglow, pending confirmation of its variability. Further observations are ongoing.
We thank the staff at San Pedro Martir for their support.
In the GCNC 30823, we have a typo of the GRB name in the text and it was corrected now. We apologize for the possible confusion and inconvenience.
GCN Circular 30839
Subject
GRB 210912A: Swift-BAT refined analysis
Date
2021-09-13T23:34:08Z (4 years ago)
From
Sibasish Laha at GSFC <sibasish.laha@nasa.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),
D. M. Palmer (LANL), T. Sakamoto (AGU),
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210912A (trigger #1072990)
(Troja et al., GCN Circ. 30820). The BAT ground-calculated position is
RA, Dec = 129.874, 79.216 deg which is
RA(J2000) = 08h 39m 29.7s
Dec(J2000) = +79d 12' 59.3"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
The BAT light curve showed a complex structure with a duration of about ~30 sec.
T90 (15-350 keV) is 28.35 +- 14.34 sec (estimated error including systematics).
The time-averaged spectrum from T-23 to T+25 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.61 +- 0.13. The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+0.23 sec in the 15-150 keV band
is 1.7 +- 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/1072990/BA/
GCN Circular 30837
Subject
GRB 210912A: Tautenburg observations
Date
2021-09-13T16:25:04Z (4 years ago)
From
Ana Nicuesa at TLS Tautenburg <ana@tls-tautenburg.de>
A. Nicuesa Guelbenzu, S. Klose, S. Melnikov, B. Stecklum, C. Hoegner (all
TLS Tautenburg) report:
We observed the field of GRB 210912A (Troja et al., GCN 30820) with the
Tautenburg 1.34m Schmidt telescope equipped with the TAUKAM 6kx6k CCD
camera and the Sloan r-band filter.
Observations were performed on September 12, at a midtime of 19.33 UT,
22.17 UT, and 02:36 UT (Sep 13). The optical transient (Hu et al., GCN
30823; Pankov et al., GCN 30825; Kuin & Troja, GCN 30832; Kann et al. GCN
30833) is detected with the following preliminary AB magnitudes:
r_1 = 21.95 +- 0.19,
r_2 = 22.17 +- 0.19,
r_3 = 22.53 +- 0.19.
Magnitudes are calibrated against the Pan-STARRS catalogue.
A comparison with the previous observations suggests that around 0.6 days
the decay index of the light curve has increased from a rather modest
value of alpha = 0.4 to alpha about 1. Further observations are required
in order to provide a more precise decay index.
GCN Circular 30834
Subject
GRB 210912A: CAHA 2.2m Detection
Date
2021-09-13T09:35:41Z (4 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC,
DARK/NBI), C. Thoene, M. Blazek, J. F. Agui Fernandez (all
HETH/IAA-CSIC), and S. Gongora (CAHA) report:
We observed GRB 210912A (Swift detection: Troja et al., GCN #30820) with
CAFOS mounted on the 2.2m CAHA telescope at Calar Alto, Almeria, Spain.
We obtained 7 x 60 s in the SDSS i' band under passing clouds, starting
at 20:04:34 UT (9.056 hrs after the trigger; further observations at a
later time were prevented by cloud cover). The afterglow (Hu et al., GCN
#30823; Pankov et al., GCN #30825; Kuin & Troja, GCN #30832) is faintly
detected in the stacked image.
Compared to a nearby Pan-STARRS comparison star, we measure (AB mag) i'
= 21.66 +/- 0.15 mag at 0.38146 d after the GRB, further confirming the
decaying afterglow. This is still significantly brighter than the
potential underlying host galaxy (Kann, GCN #30829).
GCN Circular 30833
Subject
GRB 210912A: Swift-XRT refined Analysis
Date
2021-09-13T09:18:53Z (4 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A.P. Beardmore (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC
& INAF-OAR), V. D'Elia (SSDC & INAF-OAR), D.N. Burrows (PSU), J. D.
Gropp (PSU), J.A. Kennea (PSU), P.A. Evans (U. Leicester), J.P. Osborne
(U. Leicester) and E. Troja report on behalf of the Swift-XRT team:
We have analysed 4.1 ks of XRT data for GRB 210912A (Troja et al. GCN
Circ. 30820), from 46 s to 29.0 ks after the BAT trigger. The data
comprise 32 s in Windowed Timing (WT) mode (the first 5 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Evans et
al. (GCN Circ. 30830).
The light curve can be modelled with an initial power-law decay with an
index of alpha=3.4 (+/-0.4), followed by a break at T+140 s to an alpha
of 0.68 (+/-0.05).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.67 (+0.25, -0.23). The
best-fitting absorption column is 1.2 (+0.9, -0.7) x 10^21 cm^-2, in
excess of the Galactic value of 2.4 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 4.1 x 10^-11 (4.7 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.2 (+0.9, -0.7) x 10^21 cm^-2
Galactic foreground: 2.4 x 10^20 cm^-2
Excess significance: 2.2 sigma
Photon index: 1.67 (+0.25, -0.23)
If the light curve continues to decay with a power-law decay index of
0.68, the count rate at T+24 hours will be 0.014 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.7 x
10^-13 (6.6 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01072990.
This circular is an official product of the Swift-XRT team.
GCN Circular 30832
Subject
GRB 210912A: Swift/UVOT Detection
Date
2021-09-13T07:47:54Z (4 years ago)
From
Paul Kuin at MSSL <npkuin@gmail.com>
N. P. M. Kuin (UCL-MSSL) and E. Troja (NASA/GSFC/UMCP)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210912A
60 s after the BAT trigger (Troja et al., GCN Circ. 30820).
A source consistent with the optical position
(Hu et al. GCN Circ. 30823)
is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 08:39:34.27 = 129.89280 (deg.)
Dec (J2000) = +79:13:17.1 = 79.22141 (deg.)
with an estimated uncertainty of 0.47 arc sec. (radius, 90% confidence).
Preliminary detections and 3-sigma upper limits using the UVOT photometric
system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures
are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 60 209 147 18.73 +/- 0.08
v 602 621 19 >17.8
b 528 547 19 >18.3
u 272 490 214 19.56 +/- 0.31
w2 577 597 19 >18.8
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.027 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 30830
Subject
GRB 210912A: Enhanced Swift-XRT position
Date
2021-09-12T20:48:34Z (4 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester)
report on behalf of the Swift-XRT team.
Using 526 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 210912A, 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 = 129.88990, +79.22148 which is equivalent
to:
RA (J2000): 08h 39m 33.58s
Dec (J2000): +79d 13' 17.3"
with an uncertainty of 2.6 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the
Swift-XRT team.
GCN Circular 30829
Subject
GRB 210912A: Host-galaxy candidate in PanSTARRS
Date
2021-09-12T18:48:08Z (4 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
D. A. Kann (HETH/IAA-CSIC) reports:
At the afterglow position (Hu et al., GCN #30823, see also Pankov et
al., GCN #30825) of the Swift GRB 210912A (Troja et al., GCN #30820), an
object is visible in Pan-STARRS pre-imaging at position (J2000):
RA = 129.89171813
Dec. = +79.22157927
in agreement with the position given by Hu et al., GCN #30823,
with magnitudes:
g' = 23.19 +/- 0.23 mag,
r' = 23.09 +/- 0.36 mag,
i' = 22.48 +/- 0.13 mag,
z' = 22.43 +/- 0.25 mag.
It is undetected in Y.
We suggest this object to be the host galaxy of GRB 210912A. This may be
indicative that this is a low-redshift event which may be followed by a
detectable supernova.
Further follow-up despite the very northerly position is warranted.
GCN Circular 30825
Subject
GRB 210912A: Mondy optical afterglow confirmation
Date
2021-09-12T17:21:48Z (4 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
N. Pankov (HSE), S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP)
report on behalf of GRB IKI FuN:
We observed the field of GRB 210912A (Troja et al., GCN 30820) with
AZT-33IK telescope of Sayan observatory (Mondy) starting on
2021-09-12(UT) 12:57:48. We obtained 30 images in R-filter. We confirm
the fading object suggested by Hu et al. (GCN 30823) as the optic
afterglow of GRB 210912A. Preliminary photometry of the object in
stacked images is following
Date UT start t-T0 Filter Exp. OT Err. UL(3sigma)
(mid, days) (s)
2021-09-12 12:57:48 0.10112 R 29*120 21.33 0.14 22.5
The photometry is based on the nearby USNO-B1.0 stars
RA DEC R2
08:39:12.26208 +79:12:37.1304 15.88
08:39:10.94880 +79:16:33.8916 15.26
GCN Circular 30824
Subject
Swift GRB 210912A: Global MASTER-Net observations report
Date
2021-09-12T16:40:30Z (4 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin,
V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva,
D.Kuvshinov, D. Cheryasov
(Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile
(Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra
(The Instituto de Astrofisica de Canarias),
D. Buckley
(South African Astronomical Observatory),
O.A. Gres, N.M. Budnev, O.Ershova
(Irkutsk State University, API),
A. Tlatov, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich, Yu. Sergienko
(Blagoveschensk Educational State University)
MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 210912A ( E. Troja et al., GCN 30820) errorbox 19826 sec after notice time and 19878 sec after trigger time at 2021-09-12 16:32:29 UT, with upper limit up to 15.0 mag. Observations started at twilight. The observations began at zenith distance = 57 deg. The sun altitude is -12.6 deg.
The galactic latitude b = 32 deg., longitude l = 134 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=1718486
We obtain a following upper limits.
Tmid-T0 | Site |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________
5800 | MASTER- | C | 25 | 13.0 |
8423 | MASTER- | C | 20 | 17.6 |
8423 | MASTER- | C | 20 | 13.9 |
19968 | MASTER-Kislovodsk | C | 180 | 15.0 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 30823
Subject
GRB 210912A: BOOTES-5/JGT optical afterglow candidate
Date
2021-09-12T15:04:10Z (4 years ago)
From
Youdong HU at IAA-CSIC <huyoudong072@hotmail.com>
Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia, A. J. Castro-Tirado, R. Sanchez-Ramirez and M.D. Caballero-Garcia (IAA-CSIC), D. Hiriart and W. H. Lee (UNAM), C. J. Perez del Pulgar and I. Carrasco (UMA), I. H. Park (SKKU) on behalf of a larger collaboration, report:
The 60cm BOOTES-5/JGT robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically responded in 13 s to the Swift trigger for GRB 210912A (Troja et al., GCNC 30820). In the co-added clear image (30 x 1 s), we find an uncataloged optical source at (J2000) coordinates RA: 8:39:34.30, DEC:+79:13:17.5, which is located at the edge of the XRT error box (Troja et al., GCNC 30820) and for which we measure R = 18.5 mag. We propose this source to be the GRB 210219A optical afterglow, pending confirmation of its variability. Further observations are ongoing.
We thak the staff at San Pedro Martir for their support.
GCN Circular 30820
Subject
GRB 210912A: Swift detection of a burst
Date
2021-09-12T11:18:18Z (4 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
E. Troja (NASA/GSFC/UMCP), A. P. Beardmore (U Leicester),
R. Caputo (NASA/GSFC), N. J. Klingler (GSFC/UMBC/CRESSTII),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester) and
D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 11:01:11 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210912A (trigger=1072990). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 129.769, +79.194 which is
RA(J2000) = 08h 39m 04s
Dec(J2000) = +79d 11' 38"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a complex
structure with a duration of about 40 sec. The peak count rate
was ~2800 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 11:02:04.1 UT, 52.6 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source located at RA, Dec 129.88358,
79.22292 which is equivalent to:
RA(J2000) = 08h 39m 32.06s
Dec(J2000) = +79d 13' 22.5"
with an uncertainty of 7.5 arcseconds (radius, 90% containment). This
location is 129 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
https://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 2.40
x 10^20 cm^-2 (Willingale et al. 2013).
The initial flux in the 2.5 s image was 6.40e-10 erg cm^-2 s^-1 (0.2-10
keV).
There are no UVOT data available.
Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov).
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/)