GRB 220430A
GCN Circular 31999
Subject
GRB 220430A: Nanshan/NEXT optical upper limit
Date
2022-05-06T04:58:07Z (4 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
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 220430A detected by Swift (Ambrosi et al.,
GCN 31972) and AGILE (Ursi et al., GCN 31975) using the NEXT-0.6m
telescope located at Nanshan, Xinjiang, China. Observations started at
14:13:38 UT on 2022-04-30 (i.e., 20.39 min after the BAT trigger). We
obtained 3x40, 6x60, 3x90, 6x200 s frames in the Sloan r-band and
3x60,3x90,6x200 s frames in Sloan z-band.
No optical source is detected in our stacked image at the XRT enhanced
position (Osborne et al., GCN 31973), with upper limits as follows
Tmid-T0 (hr) Filter UpperLimit (3sigma)
0.953 r >20.7
0.923 z >19.0
calibrated with the nearby PanSTARRS field.
GCN Circular 31998
Subject
GRB 220430A: Nanshan/HMT optical upper limit
Date
2022-05-06T04:52:43Z (4 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
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 220430A detected by Swift (Ambrosi et al.,
GCN 31972) and AGILE (Ursi et al., GCN 31975) using the HMT-0.5m
telescope located at Nanshan, Xinjiang, China. Observations started at
13:58:51 UT on 2022-04-30 (i.e., 5.6 min after the BAT trigger), and
3x20, 3x40, 4x60, 12x90 s unfiltered frames were obtained.
No optical source is detected in our stacked image at the XRT position
(Osborne et al., GCN 31973), down to a limiting magnitude of ~19.2,
calibrated with the Gaia DR2 stars.
GCN Circular 31997
Subject
GRB 220430A: GIT optical upper limits
Date
2022-05-05T00:54:08Z (4 years ago)
From
Varun Bhalerao at Indian Inst of Tech <varunb@iitb.ac.in>
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 220430A detected by Swift (Ambrosi et al. GCN #31972) and AGILE (Ursi et al. GCN #31975), with a 0.7m GROWTH-India Telescope (GIT). The observation started on 2022-04-30 at 14:23:56 UT, 30.65 min after the SWIFT BAT trigger. We obtained multiple 100-sec exposures in the r' and i' filters. The images were shallower than usual due to poor observing conditions. We did not detect any new source in our stacked image within the 2.0" circle around R.A.= 06h 30m 26.92s, Dec.= +09d 32' 51.1" (J.P. Osborne et al. GCN #31973). The obtained upper limits follow as:
-------------------------------------------------------------------
JD (mid) | T_mid-T0(hrs) | Exposure (sec) | Filter | Lim_mag (5-sigma) |
-------------------------------------------------------------------
2459700.10382 | 0.60 | 300 (stacked) | r' | > 19.26 |
2459700.10763 | 0.69 | 300 (stacked) | i' | > 18.68 |
-------------------------------------------------------------------
The upper limits are consistent with the Ambrosi et al., (GCN #31972), Groot et al. (GCN #31974), Pankov et al.(GCNC #31976), Dornic et al. (GCN #31977), V. Lipunov et al.(GCN #31978) and Y.-D. Hu et al. (GCN #31980). 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/.
GCN Circular 31987
Subject
GRB 220430A: AstroSat CZTI detection
Date
2022-05-02T07:40:42Z (4 years ago)
From
Gaurav Waratkar at IIT,Bombay <gauravwaratkar@iitb.ac.in>
R. Gopalakrishnan (IUCAA), V. Prasad (IUCAA), G. Waratkar (IITB), A.
Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat
CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al.,
2021, JApA, 42, 73) showed detection of a long GRB 220430A which was
also reported by Swift (Ambrosi et al., GCN 31972; Osborne et al., GCN
31973; Barthelmy et al., GCN 31981), and AGILE (Ursi et al., GCN 31975).
The source was clearly detected in the 20-200 keV energy range. The
light curve showed multiple peaks of emission with the strongest peak at
2022-04-30 13:53:58.50 UT. The measured peak count rate associated with
the burst is 892 (+60, -62) counts/s above the background in the
combined data of all the quadrants, with a total of 11896 (+669, -639)
counts. The local mean background count rate was 484 (+2, -2) counts/s.
Using cumulative rates, we measure a T90 of 40 (+4, -2) s.
It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. The light curve showed multiple peaks
of emission with the strongest peak at 2022-04-30 13:53:58.52 UT. The
measured peak count rate is 3131 (+109, -98) counts/s above the
background in the combined Veto data of four quadrants, with a total of
48203 (+1134, -1252) counts. The local mean background count rate was
1614 (+3, -5) counts/s. We measure a T90 of 41 (+1, -2) s from the
cumulative Veto light curve.
CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb [1]. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC,
and PRL. The Indian Space Research Organisation funded, managed, and
facilitated the project.
Links:
------
[1] http://astrosat.iucaa.in/czti/?q=grb
GCN Circular 31981
Subject
GRB 220430A: Swift-BAT refined analysis
Date
2022-05-01T15:16:28Z (4 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
S. D. Barthelmy (GSFC), E. Ambrosi (INAF-IASFPA),
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),
T. Sakamoto (AGU), M. Stamatikos (OSU)
(i.e. the Swift-BAT team):
Using the data set from T-204 to T+843 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 220430A (trigger #1104692)
(Ambrosi et al., GCN Circ. 31972). The BAT ground-calculated position is
RA, Dec = 97.616, 9.547 deg which is
RA(J2000) = 06h 30m 27.9s
Dec(J2000) = +09d 32' 50.1"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
The mask-weighted light curve shows two major pulse emissions. The first
one starts at ~T-7 s, peaks at ~T+20 s, and ends at ~T+30 s. It is
followed by another larger pulse with several peaks. The largest peak
occurs at ~T+42 s. The burst emission ends at ~T+100 s. T90 (15-350 keV)
is 43.10 +- 0.57 sec (estimated error including systematics).
The time-averaged spectrum from T-6.53 to T+94.36 sec is best fit by
a simple power-law model. The power law index of the time-averaged
spectrum is 1.24 +- 0.02. The fluence in the 15-150 keV band is
4.4 +- 0.05 x 10^-5 erg/cm2. The 1-sec peak photon flux measured from
T+42.00 sec in the 15-150 keV band is 29.6 +- 0.6 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/1104692/BA/
GCN Circular 31980
Subject
GRB 220430A: CAHA 2.2m telescope optical limit
Date
2022-05-01T09:53:15Z (4 years ago)
From
Youdong HU at IAA-CSIC <huyoudong072@hotmail.com>
Y.-D. Hu, T.-R. Sun, M. D. Caballero-Garcia, R. Sanchez-Ramirez, I. Perez-Garcia and A. J. Castro-Tirado (IAA-CSIC), R. Minguez and I. Vico (CAHA) on behalf of a larger collaboration, report:
Following the detection of GRB 220430A by Swift (Ambrosi et al. GCNC 31972) and AGILE (Ursi et al. GCNC 31975), we triggered the 2.2m CAHA telescope (+ CAFOS) at the Calar Alto Observatory (Almeria, Spain). Images were gathered after the twilight starting on Apr. 30 20:15 UT (i.e. 6.4 hrs post trigger) in Sloan-gri at high airmass. On the co-added Sloan-i band image (8x60s), no optical transient down to 22.1 mag is detected at the X-ray afterglow candidate position reported by Swift/XRT (Ambrosi et al. GCNC 31972, J.P. Osborne et al. GCNC 31973). This non-detection is consistent with the report from Groot et al. (GCNC 31974), Pankov et al.(GCNC 31976), Dornic et al. (GCNC 31977) and V. Lipunov et al.(GCNC 31978).
We thank the staff at Calar Alto observatory for their excellent support.
GCN Circular 31979
Subject
GRB 220430A: Swift-XRT refined Analysis
Date
2022-05-01T03:34:28Z (4 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), M. Capalbi
(INAF-IASFPA), M. Perri (SSDC & INAF-OAR), J.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), K.L. Page (U. Leicester)
and E. Ambrosi report on behalf of the Swift-XRT team:
We have analysed 7.6 ks of XRT data for GRB 220430A (Ambrosi et al. GCN
Circ. 31972), from 39 s to 39.2 ks after the BAT trigger. The data
comprise 539 s in Windowed Timing (WT) mode (the first 11 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 Osborne et
al. (GCN Circ. 31973).
The late-time light curve (from T0+4.2 ks) can be modelled with a
power-law decay with a decay index of alpha=1.35 (+/-0.09).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.65 (+/-0.05). The
best-fitting absorption column is 1.05 (+0.07, -0.06) x 10^22 cm^-2,
in excess of the Galactic value of 6.5 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.85 (+0.17, -0.16)
and a best-fitting absorption column of 1.03 (+0.19, -0.17) x 10^22
cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 5.3 x 10^-11 (8.9 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.03 (+0.19, -0.17) x 10^22 cm^-2
Galactic foreground: 6.5 x 10^21 cm^-2
Excess significance: 3.8 sigma
Photon index: 1.85 (+0.17, -0.16)
If the light curve continues to decay with a power-law decay index of
1.35, the count rate at T+24 hours will be 0.015 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.0 x
10^-13 (1.4 x 10^-12) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01104692.
This circular is an official product of the Swift-XRT team.
GCN Circular 31978
Subject
Swift GRB 220430A: Global MASTER-Net observations report
Date
2022-05-01T03:04:33Z (4 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko,
G.Antipov, D.Zimnukhov, V.Senik, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D.Cheryasov, Ya.Kechin
(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
(Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez
(INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov
(Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov
(Blagoveschensk Educational State University)
MASTER-OAGH robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) was pointed to the Swift GRB 220430A ( E. Ambrosi et al., GCN 31972) errorbox 46599 sec after notice time and 46878 sec after trigger time at 2022-05-01 02:54:34 UT, with upper limit up to 15.0 mag. Observations started at twilight. The observations began at zenith distance = 56 deg. The sun altitude is -12.3 deg.
The galactic latitude b = 0 deg., longitude l = 202 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=1959132
We obtain a following upper limits.
Tmid-T0 | Site |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________
46968 | MASTER-OAGH | C | 180 | 15.0 |
46968 | MASTER-OAGH | C | 180 | 14.9 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 31977
Subject
GRB 220430A: GRANDMA observations
Date
2022-05-01T00:24:17Z (4 years ago)
From
Alain Klotz at IRAP-CNRS-OMP <Alain.Klotz@free.fr>
D. Dornic (CPPM), A. Klotz (CNRS-OMP-IRAP), A. Sabahaddin (ShaO),
T. Midavaine (KNC), V. Rupchandani (AUS), P. A. Duverne (IJCLAB),
Y. Rajabov (UBAI), X. Song (BJP), X. F. Wang (THU/BJP), J. Zhu (BJP),
L. Wang,�� X. Zeng, A. Iskandar (XAO), P. Thierry (AGORA),
A. Kaeouach (Tanger), Z. Benkhaldoun (OUCA),
S. Antier, A. de Ugarte Postigo (CNRS-OCA-ARTEMIS)
report on behalf of GRANDMA collaboration:
The GRANDMA telescope network responded to the alert of GRB 220430A
(Ambrosi et al. GCN 31972, Osborne et al., GCN 31973,
Groot et al., GCN 31974, Ursi�� et al., GCN 31975,
Pozanenko et al. GCN 31976). The first observations
started 34 min after the SWIFT BAT trigger time.
We did not detect any optical transient within the XRT error box
during the first 2.9 hours. We report our 3-sigma upper limits.
Magnitudes are given in the AB system.
T-T0 (hr)| MJD������������ | Obser.���� |Exposure| Filter| Upp.Lim. (AB)
0.56111�� |59699.60204| SNOVA �������� | 4x300s | Clear | 19.0
2.59194�� |59699.68666| Makes-T60| 10x120s| Clear | 19.5
6.24347�� |59699.83880| HAO���������� | 20x120s| L�������� | 20.6
6.33472�� |59699.84260| MOSS�������� | 30x60s | Clear | 21.0
The images have been calibrated with SDSS DR7.
T-T0 is the started date.
GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr)
devoted to the observation of transients in the context of multi-messenger
astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is
the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).
GCN Circular 31976
Subject
GRB 220430A: Mondy and AbAO optical upper limits
Date
2022-04-30T21:25:52Z (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), R. Ya. Inasaridze (AbAO) report on behalf of GRB IKI FuN:
We observed the field of Swift GRB 220430A (Ambrosi et al., GCN 31972)
also detected by AGILE (Ursi et al., GCN 31975) with AZT-33 telescope
of Mondy observatory starting on April, 30 (UT) 14:20:53 and AS-32
telescope of Abastumani observatory starting on April, 30 (UT)
16:59:12. We do not detect any sources in the enhanced position of
Swift-XRT (Osborne et al., GCN 31973) consistent with the observations
of Swit/UVOT (Ambrosi et al., GCN 31972) and MeerLICHT (Groot et al.,
GCN 31974).
Preliminary photometry of the combined images is following
Date, UT start, t-T0, Exp., Filter, OT, Err, UL(3 sigma)
(mid, days)
2022-04-30 14:20:53 0.01953 1*60 R n/d n/d 19.5
2022-04-30 14:20:53 0.02613 20*60 R n/d n/d 20.5
2022-04-30 16:59:12 0.14962 59*60 R n/d n/d 21.0
The photometry is based on nearby USNO-B1.0 stars, R2 magnitude
USNO-B1.0_id R2
0995-0113632 16.50
0995-0113723 15.94
GCN Circular 31975
Subject
GRB 220430A: AGILE detection
Date
2022-04-30T19:06:05Z (4 years ago)
From
Alessandro Ursi at INAF/IAPS <alessandro.ursi@gmail.com>
A. Ursi (INAF/IAPS), F. Longo (Univ. Trieste and INFN Trieste), F.
Verrecchia, C. Pittori (SSDC, and INAF/OAR), M. Tavani (INAF/IAPS, and
Univ. Roma Tor Vergata), A. Argan, M. Cardillo, C. Casentini, Y.
Evangelista, E. Menegoni, L. Foffano, G. Piano (INAF/IAPS), F. Lucarelli
(SSDC, and INAF/OAR), A. Bulgarelli, A. Di Piano, V. Fioretti, F. Fuschino,
N. Parmiggiani (INAF/OAS-Bologna), M. Marisaldi (INAF/OAS-Bologna, and
Bergen University), M. Pilia, A. Trois (INAF/OA-Cagliari), I. Donnarumma
(ASI), A. Giuliani (INAF/IASF-Mi), report on behalf of the AGILE Team:
The AGILE satellite detected the GRB 220430A at T0 = 2022-04-30 13:53:45
(UTC), reported by Swift (GCNs #31972 and #31973).
The burst is clearly visible in the AGILE scientific ratemeters of the
SuperAGILE detector (SA; 20-60 keV) and in all the five panels of the
AntiCoincidence system (AC Top, 50-200 keV; AC Lat, 80-200 keV). The event
lasted about 25 s and it released a total number of 2685 counts in the SA
detector (above a background rate of 100 Hz), 25765 counts in the MCAL
detector (above a background rate of 1070 Hz), and 67565 counts in the AC
detector (above a background rate of 2710 Hz). The AGILE ratemeter light
curves can be found at
http://www.agilescienceapp.it/notices/GRB220430A_AGILE_RM.png .
As pointed out in GCN #31972, we notice that this event took place at the
end of an intense X-class solar flare, clearly detected by all the AGILE
scientific ratemeters. A more extended light curve can be found at
http://www.agilescienceapp.it/notices/GRB220430A_AGILE_RM_all.png .
Additional analysis of AGILE data is in progress. Automatic MCAL GRB alert
Notices can be found at: https://gcn.gsfc.nasa.gov/agile_mcal.html.
GCN Circular 31974
Subject
GRB 220430A: MeerLICHT optical upper limits
Date
2022-04-30T19:04:51Z (4 years ago)
From
Paul Groot at Radboud University Nijmegen <p.groot@astro.ru.nl>
P.J. Groot (Radboud/UCT/SAAO), S.de Wet (UCT), D.B. Malesani
(Radboud, DAWN/NBI), A.J. Levan (Radboud), P.M. Vreeswijk (Radboud),
report on behalf of the MeerLICHT consortium:
GRB220430A (Ambrosi et al., GCN 31972) triggered automatic observations
with the 0.6m wide-field MeerLICHT telescope, located at Sutherland,
South Africa. Observations started at 2022-04-30, 17:10:19 UT in a
series of 60s integrations in an alternating sequence of the
u,g,q,r,i,z bands. Observations were stopped after 2022-04-30,
17:27:48 UT due to the visibility of the source location.
A preliminary analysis of the u, q and i-band images shows no new
optical transient in these bands within the Swift-BAT error circle,
including the position of the new X-ray source detected in the Swift-XRT
observations.
Five-sigma limiting magnitudes for an optical transient located at the
Swift-XRT position are:
u > 19.0 at 17:11:46 UT,
q > 20.4 at 17:13:14 UT,
i > 18.6 at 17:20:32 UT.
Further analysis is ongoing
MeerLICHT is built and run by a consortium consisting of Radboud
University, the University of Cape Town, the South African Astronomical
Observatory, the University of Oxford, the University of Manchester
and the University of Amsterdam.
GCN Circular 31973
Subject
GRB 220430A: Enhanced Swift-XRT position
Date
2022-04-30T18:35:16Z (4 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.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 1120 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 220430A, 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 = 97.61218, +9.54754 which is equivalent
to:
RA (J2000): 06h 30m 26.92s
Dec (J2000): +09d 32' 51.1"
with an uncertainty of 2.0 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 31972
Subject
GRB 220430A: Swift detection of a burst or Swift J0630.4+0932
Date
2022-04-30T14:22:26Z (4 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
E. Ambrosi (INAF-IASFPA), A. D'Ai (INAF-IASFPA),
V. D'Elia (SSDC & INAF-OAR), C. Gronwall (PSU), J.D. Gropp (PSU),
J. A. Kennea (PSU), A. Y. Lien (U Tampa), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 13:53:15 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 220430A (trigger=1104692). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 97.611, +9.510 which is
RA(J2000) = 06h 30m 27s
Dec(J2000) = +09d 30' 36"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve appears to show a
double-peaked structure with the second peak larger, and a total
duration of about 70 sec. The peak count rate was ~35000 counts/sec
(15-350 keV), at ~38 sec after the trigger.
However, near the time of the GRB the Sun also produced an X-class
solar flare which may be the cause of some or all of the apparent
lightcurve activity. The GRB emission will be independently
determined once the mask-tagged BAT data has been received.
The XRT began observing the field at 13:54:07.7 UT, 51.7 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source with an enhanced position: RA, Dec 97.61267,
9.54730 which is equivalent to:
RA(J2000) = 06h 30m 27.04s
Dec(J2000) = +09d 32' 50.3"
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This
location is 134 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 in excess of the Galactic value (6.47 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 1.1
(+0.75/-0.59) x 10^22 cm^-2 (90% confidence).
The initial flux in the 0.1 s image was 4.31e-08 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 60 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 large, but uncertain, extinction expected.
Although this looks like a GRB both in terms of its lightcurve and
the presence of strong flux above 100 keV, its location near the
Galactic plane (lon=202.05, lat=-0.26) raises the possibility of it
being a Galactic transient. In addition, as noted above, the
apparent lightcurve may be due to solar activity. If further
analysis shows that it is a Galactic transient, we will use the
name Swift J0630.4+0932.
Burst Advocate for this burst is E. Ambrosi (elena.ambrosi AT inaf.it).
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/)