GRB 230420A
GCN Circular 33658
Subject
GRB 230420A: Swift detection of a burst
Date
2023-04-20T10:36:21Z (2 years ago)
From
Jamie Kennea at Penn State U <jak51@psu.edu>
N. J. Klingler (GSFC/UMBC/CRESSTII), R. Brivio (INAF-OAB),
R. A. J. Eyles-Ferris (U Leicester), J.D. Gropp (PSU),
J. A. Kennea (PSU), K. L. Page (U Leicester),
T. M. Parsotan (GSFC/UMBC/CRESSTII), C. Salvaggio (INAF-OAB) and
B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 10:19:01 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 230420A (trigger=1164980). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 161.013, +32.087 which is
RA(J2000) = 10h 44m 03s
Dec(J2000) = +32d 05' 11"
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 30 sec. The peak count rate
was ~800 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 10:20:32.9 UT, 91.8 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source with an enhanced position: RA, Dec 161.04899,
32.10766 which is equivalent to:
RA(J2000) = 10h 44m 11.76s
Dec(J2000) = +32d 06' 27.6"
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This
location is 132 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. We cannot determine whether the source
is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (1.71 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 2.1
(+2.19/-1.93) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 3.05e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 99 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag.
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.017.
Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu).
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 33661
Subject
GRB 230420A: Enhanced Swift-XRT position
Date
2023-04-20T19:32:25Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester)
report on behalf of the Swift-XRT team.
Using 1619 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 230420A, 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 = 161.04816, +32.10769 which is equivalent
to:
RA (J2000): 10h 44m 11.56s
Dec (J2000): +32d 06' 27.7"
with an uncertainty of 2.2 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 33662
Subject
GRB 230420A: LCOGT Optical Upper Limit
Date
2023-04-20T23:21:17Z (2 years ago)
From
Robert Strausbaugh at University of Minnesota <rstrausb@umn.edu>
R. Strausbaugh (University of Minnesota), A. Cucchiara (NASA) report on
behalf of a larger collaboration:
We observed the GRB 230420A (Klingler et al., GCN 33658) field with the
LCOGT 1-meter Sinistro instrument at the Teide Observatory, Tenerife site,
on April 20, from 20:28 to 20:55 UT (corresponding to 11.15 to 11.72 hours
from the GRB trigger time) with the SDSS r and i filters.
We performed a series of 3x300s exposures in each band. We do not detect a
source within the Swift-XRT enhanced error region (Osborne et al., GCN
33661) in either band.
The following upper limits are calculated using the PanSTARRS catalog as
reference:
r > 22.3
i > 21.8
These magnitudes are not corrected for galactic extinction.
GCN Circular 33663
Subject
GRB 230420A: BOOTES-5/JGT optical afterglow detection
Date
2023-04-21T07:47:36Z (2 years ago)
From
Youdong HU at IAA-CSIC <huyoudong072@hotmail.com>
Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado, I. Perez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy (IAA-CSIC), D. Hiriart and W. H. Lee (UNAM), C. J. Perez del Pulgar (UMA) and I. Carrasco (SMA) and I. H. Park (SKKU), on behalf of a larger collaboration, report:
Following the detection of GRB 230420A by Swift (Klingler et al. GCNC 33658), the BOOTES-5/JGT 0.6m robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically observed the GRB location starting on Apr. 20, 10:21:03 UT (~ 122 s after trigger). A series of images in clear filter were gathered. A new optical transient was found within the enhanced Swift/XRT position (Osborne et al. GCNC 33661) for which we measure a magnitude of 17.7 on the initial 10 s exposure frame, which we propose to be the optical afterglow for GRB 230420A.
We thank the staff at Observatorio Astronomico Nacional in San Pedro Martir for their excellent support.
GCN Circular 33664
Subject
GRB 230420A: Gaoyazi/GOT optical upper limit
Date
2023-04-21T09:07:17Z (2 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
S.Y. Fu, S.Q. Jiang, X. Liu, T.H. Lu, D Xu (NAOC), Z.P. Zhu (NAOC, HUST), S.W. Luo, M.M. Yang, Z. K. Feng (GYZO, NAOC) report
We observed the field of GRB 230420A detected by Swift (Klingler et al., GCN 33658) with the 0.5-meter Gaoyazi Optical Telescope (GOT) located at Gaoyazi, Xinjiang, China. Observations started at 17:23:51 UT on 2023-04-20, i.e., 0.30 days after the Swift/BAT trigger, and 20 x 180 s images were obtained in the Sloan r filter.
No optical source is detected in our stacked image at the enhanced XRT position (Osborne et al,. GCN 33661), down to a limiting (3-sigma) magnitude of r > 21.6 at 0.32 days post-burst, calibrated with nearby PanSTARRS stars.
GCN Circular 33665
Subject
GRB 230420A: NOT optical afterglow confirmation
Date
2023-04-21T10:27:21Z (2 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
S.Y. Fu (NAOC), K.E. Heintz (DAWN/NBI), D.B. Malesani (Radboud, DAWN/NBI), D. Xu (NAOC), M. Linares (NTNU & UPC), M. Turchetta (NTNU) report on behalf of a larger collaboration:
We observed the field of GRB 230420A detected by Swift (Klingler et al., GCN 33658) using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started at 00:31:32 UT on 2023-04-21, i.e., ~14.2 hr after the Swift/BAT trigger, and 3 x 300 s images in the Sloan r-filter and 5 x 200 s images in the Sloan z-filter were obtained, respectively.
We detect an uncatalogued source in the stacked images within the enhanced XRT error circle (Osborne et al., GCN 33661) at coordinates:
R.A. (J2000) = 10:44:11.55
Dec. (J2000) = +32:06:28.34
with an uncertainty of ~0.3 arcsec. The source has m(r) = 23.2 +/- 0.2 (AB) at 14.34 hr post-burst and m(z) = 22.3 +/- 0.2 (AB) at 14.64 hr post-burst, calibrated with nearby field stars from the Pan-STARRS catalog.
This source is likely the same as the one observed by BOOTES-5/JGT (Hu et al., GCN 33663), as both sources lie within the very small XRT error circle. The fading confirms that this source is the optical afterglow of GRB 230420A.
GCN Circular 33666
Subject
GRB 230420A: MITSuME Akeno optical observation
Date
2023-04-21T11:43:58Z (2 years ago)
From
Narikazu Higuchi at Tokyo Tech <higuchi@hp.phys.titech.ac.jp>
N. Higuchi, I. Takahashi, M. Sasada, S. Sato, R. Hosokawa, M. Niwano, Y.
Yatsu (Tokyo Tech), K. L. Murata (Kyoto U) and N. Kawai (Riken) report on
behalf of the MITSuME collaboration:
We observed the field of GRB 230420A (N. J. Klingler et al. #33658, J.P.
Osborne et al. #33661,R. Strausbaugh et al. #33662, Y.-D. Hu et al.
#33663, S.Y.
Fu et al. #33664, S.Y. Fu et al. #33665) with the optical three color (g',
Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope Akeno.
The observation with a series of 60 sec exposures started at 2023-04-20
10:23:41 UT (280 seconds after the Swift/BAT detection). We stacked the
images with good conditions. Here we report the Rc and Ic band magnitudes
by the forced-photometry at the enhanced Swift/XRT position (J.P. Osborne
et al. GCN Circular #33661), and the 5-sigma limit of the stacked images in
the g' band.
T0+[sec] |MID-UT | T-EXP[sec] | magnitudes of forced-photometry
------------------------------------------------------------------------------------------------
588 | 2023-04-20 10:28:49| 540 | g'>18.3, Rc=18.3+/- 0.3, Ic=17.3 +/- 0.2
------------------------------------------------------------------------------------------------
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 33667
Subject
GRB 230420A: Swift-XRT refined Analysis
Date
2023-04-21T12:21:34Z (2 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
E. Ambrosi (INAF-IASFPA) , S. Dichiara (PSU), J.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto), A.P. Beardmore (U. Leicester), P.A. Evans (U.
Leicester), J.P. Osborne (U. Leicester), M. Capalbi (INAF-IASFPA), M.
Perri (SSDC & INAF-OAR) and report on behalf of the Swift-XRT team:
We have analysed 7.2 ks of XRT data for GRB 230420A, from 98 s to 84.8
ks after the BAT trigger. The data comprise 102 s in Windowed Timing
(WT) mode with the remainder in Photon Counting (PC) mode.
The light curve can be modelled with an initial power-law decay with an
index of alpha=4.13 (+0.26, -0.18), followed by a break at T+316 s to
an alpha of 0.83 (+0.10, -0.07).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.59 (+/-0.09). The
best-fitting absorption column is 4.6 (+2.5, -2.3) x 10^20 cm^-2, in
excess of the Galactic value of 1.7 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.82 (+0.21, -0.11)
and a best-fitting absorption column consistent with the Galactic
value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 3.5 x 10^-11 (3.6 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.7 (+4.0, -0.0) x 10^20 cm^-2
Galactic foreground: 1.7 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.82 (+0.21, -0.11)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01164980.
This circular is an official product of the Swift-XRT team.
GCN Circular 33670
Subject
GRB 230420A: Swift-BAT refined analysis
Date
2023-04-21T14:58:39Z (2 years ago)
From
Tyler Parsotan at NASA GSFC <tyler.parsotan@nasa.gov>
T. Sakamoto (AGU), 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. Parsotan (GSFC/UMBC), M. Stamatikos (OSU) (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 230420A (trigger #1164980) (Klingler, et al., GCN Circ. 33658). The BAT ground-calculated position is
RA, Dec = 161.040, 32.111 deg which is
RA(J2000) = 10h 44m 09.5s
Dec(J2000) = +32d 06' 38.3"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).The partial coding was 100%.
The mask-weighted light curve shows possible pre-trigger activity with extended emission out to ~100 seconds. T90 (15-350 keV) is 111.75 +- 12.02 sec (estimated error including systematics).
The time-averaged spectrum from T-34.75 to T+100.80 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.96 +- 0.46, and Epeak of 70.6 +- 28.2 keV (chi squared 53.29 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 2.7 +- 0.2 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T+1.41 sec in the 15-150 keV band is 1.0 +- 0.2 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.64 +- 0.10 (chi squared 60.99 for 57 d.o.f.). 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/1164980/BA/
GCN Circular 33671
Subject
GRB230420A: VLT optical observation
Date
2023-04-21T17:10:28Z (2 years ago)
From
Hallie Fausey at George Washington U <hfausey@gwmail.gwu.edu>
H. Fausey (GWU), B. Schneider (MIT), C. C. Thoene (ASU-CAS), D. B. Malesani (Radboud Univ. and DAWN/NBI), and S. Campana (INAF-OAB) report on behalf of the Stargate collaboration:
We observed the field of GRB230420A (Klinger et al., GCN33658) with the ESO VLT UT3 (Melipal) using the acquisition camera of the X-shooter spectrograph. We took a 300s r-band image on 2023 April 20.105 UT (16 hours after the BAT trigger).
At the coordinates of the optical afterglow (Hu et al., GCN 33663; Fu et al., GCN 33665), we detect a faint source with magnitude r' = 23.2 +/- 0.1 (AB). The magnitude is consistent, within the errors, to the value reported by Fu et al. (GCN 33665). We note the presence of a marginally-detected object in the Legacy Survey at the same coordinates, which, if real, could be the GRB host galaxy.
We acknowledge the excellent support from the ESO observing staff in Paranal, in particular Zahed Wahhaj.
GCN Circular 33673
Subject
GRB 230420A: Swift/UVOT Upper Limits
Date
2023-04-21T20:14:30Z (2 years ago)
From
Samantha Oates at University of Birmingham <samantha.oates@alumni.ucl.ac.uk>
S. R. Oates (U.Birmingham) and N. J. Klingler (GSFC/UMBC/CRESSTII)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 230420A
99 s after the BAT trigger (Klingler et al., GCN Circ. 33658).
No optical afterglow consistent with the XRT position
(Osborne et al., GCN Circ. 33661) 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 99 249 147 >21.1
u_FC 258 508 246 >20.5
white 99 1190 353 >21.7
v 590 4885 255 >19.5
b 514 1165 58 >19.9
u 258 1141 285 >20.6
w1 814 5109 52 >19.1
w2 4481 4681 197 >19.8
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.017 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 33680
Subject
GRB 230420A: Lowell Discovery Telescope Optical Detection
Date
2023-04-24T17:00:41Z (2 years ago)
From
Brendan O'Connor at UMD <oconnorb@umd.edu>
B. O'Connor (UMD, GWU), E. Hammerstein (UMD), S.B. Cenko (UMD, NASA-GSFC), report on behalf of a larger collaboration:
We observed GRB 230420A (Klingler et al. GCN 33658) with the Large Monolithic Imager (LMI) on the 4.3m Lowell Discovery Telescope (LDT). Observations began on 2023-04-23 at 05:14:37 UT corresponding to ~2.8 d after the GRB trigger. Observations were carried out in r-band and i-band for 1800 s each at airmass 1.05 under seeing of ~1.6".
At the location of the optical counterpart (Hu et al. GCN 33663, Fu et al. GCN 33665, Fausey et al. GCN 33671) we detect a weak source in each filter. We measure magnitudes r~25.0+/-0.4 AB mag and i~24.2+/-0.2 AB mag. This is likely dominated by the contribution from the possible host galaxy (Fausey et al. GCN 33671).
Magnitudes are calibrated against the PS1 catalog and are not corrected for Galactic extinction.
We thank the staff of the Lowell Discovery Telescope for assistance with these observations.
GCN Circular 33717
Subject
GRB 230420A: AROMA-N Optical Upper Limit
Date
2023-05-02T09:00:50Z (2 years ago)
From
Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp>
Y. Koyanagi, T. Sakamoto (AGU)
We observed the field of GRB 230420A detected by Swift
(Klingler et al., GCN Circ. 33658) with the 14-inch AGU Robotic
Optical Monitor for Astrophysical object - Narrow (AROMA-N)
located at the Sagamihara campus of Aoyama Gakuin University.
13 images of 60 sec exposures were taken in the R filter
starting from April 20 11:41:42 (UT) about 1.37 hours
after the trigger and stopped on April 20 11:59:16 (UT).
We do not detect the optical afterglow both in the individual
images and the stacked image. The estimated five sigma
upper limit of the combined image (total exposure of 780 sec)
is ~17.1 mag using the USNO-B1 catalog.
GCN Circular 33725
Subject
GRB 230420A: Mondy optical afterglow detection, TSHAO, CrAO optical upper limit
Date
2023-05-05T22:18:02Z (2 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
N. Pankov (HSE), A. Pozanenko (IKI), E. Klunko (ISTP), I. Reva (FAPI), V. Rumyantsev (CrAO), S. Belkin (IKI) report on behalf of GRB IKI FuN:
We observed the field of Swift GRB 230420A (Klingler et al. GCN 33658) with AZT-33IK telescope of Mondy observatory in R-filter on 2023-04-20 starting (UT) 13:31:08, with Zeiss-1000 telescope of of Tien Shan Astronomical Observatory on 2023-04-20 starting (UT) 22:11:07, with Shajn 2.6m telescope of CrAO on 2023-04-22 and 2023-04-23. We detect the afterglow (Hu et al., GCN 33663; Fu et al., GCN 33665; Fausey et al., GCN 33671; O'Connor et al., GCN 33680) in Mondy observatory and obtained upper limits in TSHAO and CrAO observatories. The afterglow is detected at coordinates of (J2000) 10 44 11.53 +32 06 28.4 which are compatible with NOT estimated coordinates (Fu et al., GCN 33665) and are within Swift XRT enhanced position (Osborneet al. GCN 33661).
Preliminary photometry of stacked images is following
Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) Observ.
(mid, days) (s)
2023-04-20 13:31:08 0.15424 30*120 R 22.0 0.1 22.8 Mondy
2023-04-20 16:49:25 0.28431 20*120 R 22.7 0.3 22.7 Mondy
2023-04-20 22:11:07 0.36494 31*120 R n/d n/d 22.1 TSHAO
2023-04-21 15:23:44 1.25189 27*120 R n/d n/d 22.5 Mondy
2023-04-22 18:33:32 2.52854 49*120 R n/d n/d 22.6 CrAO
2023-04-23 19:22:36 3.41915 60*120 R n/d n/d 23.1 CrAO
2023-04-22+2023-04-23 2.97385 109*120 R n/d n/d 23.5 CrAO
The photometry is based on nearby USNO-B1.0 R2 stars.