GRB 250330A
GCN Circular 39938
Subject
GRB 250330A: Swift detection of a burst
Date
2025-03-30T06:28:16Z (3 months ago)
From
K.L. Page at U Leicester <klp5@leicester.ac.uk>
Via
email
S. B. Cenko (GSFC), K. L. Page (U Leicester) and M. H. Siegel (PSU)
report on behalf of the Neil Gehrels Swift Observatory Team:
At 06:07:38 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 250330A (trigger=1299776). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 252.790, -86.870 which is
RA(J2000) = 16h 51m 10s
Dec(J2000) = -86d 52' 11"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single peak
structure with a duration of about 10 sec. The peak count rate
was ~5800 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 06:08:51.3 UT, 73.2 seconds after
the BAT trigger. Due to the proximity of Swift to the SAA, XRT centroided on
a cosmic ray. Given the short visibility window, no other data are available
at this time.
UVOT data are not available at this time.
Although this trigger occurred while Swift was close to the SAA, the
BAT light-curve shows a definite peak, and Fermi-GBM also triggered at the
same time.
Burst Advocate for this burst is S. B. Cenko (brad.cenko 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/)
GCN Circular 39940
Subject
GRB 250330A: Prompt Swift-XRT position
Date
2025-03-30T09:00:27Z (3 months ago)
From
K.L. Page at U Leicester <klp5@leicester.ac.uk>
Via
email
K.L. Page and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT
team:
Because of the location of Swift with respect to the South Atlantic
Anomaly at the time of the burst, XRT began collecting Photon Counting
mode data for GRB 250330A (GCN Circ. 39938) around 4 ks after the trigger.
Using promptly downlinked data we find an uncatalogued X-ray source
located at RA, Dec = 252.9515, -86.87972 which is equivalent to
RA (J2000): 16h 51m 48.36s
Dec (J2000): -86d 52' 47.0"
with an uncertainty of 3.9 arcsec (radius, 90% confidence). This is 47
arcseconds from the BAT position, inside the BAT error circle.
This circular is an official product of the Swift-XRT team.
GCN Circular 39941
Subject
GRB 250330A: VLT/FORS2 Optical Observations
Date
2025-03-30T10:22:23Z (3 months ago)
From
Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra@roma2.infn.it>
Via
Web form
Rosa Becerra (U Rome), Eleonora Troja (U Rome), Muskan Yadav (U Rome), Roberto Ricci (U Rome) report on behalf of the ERC BHianca team:
We observed the field of GRB 250330A (Cenko et al., GCN 39938) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began at T+1.25 hours after the trigger and were carried out in the R filter at an average seeing of 0.7" and airmass about 2.2.
Image subtraction against the SkyMapper Southern Survey (SMSS) Fourth Data Release (DR4) catalog (Onken et al., 2024) shows no new uncataloged source down to r~21.5 AB. Several fainter objects are visible within the XRT position (Page et al., GCN 39940), however, additional observations are required to assess their variability
We thank the staff at the VLT for the rapid execution of these observations.
GCN Circular 39944
Subject
GRB 250330A: Fermi GBM Final Localization
Date
2025-03-30T12:59:41Z (3 months ago)
From
Utkarsh Pathak at IIT Bombay <utkarshpathak.07@gmail.com>
Via
Web form
The Fermi GBM team reports the detection of a likely LONG GRB
"At 06:07:38.42 UT on 30 March 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250330A (trigger 765007663/250330255).
The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 254.96, Dec = -66.02 (J2000 degrees, equivalent to J2000 16h 51m, -86d 52'),
with a statistical uncertainty of 6.9 degrees. This localization is consistent
with Swift-BAT location (Cenko et al. 2025, GCN 39938) and Swift-XRT (Page et al. 2025, 39940).
The angle from the Fermi LAT boresight is 46 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330255/quicklook/glg_skymap_all_bn250330255.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330255/quicklook/glg_healpix_all_bn250330255.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330255/quicklook/glg_lc_medres34_bn250330255.gif"
GCN Circular 39947
Subject
GRB 250330A: Swift-XRT afterglow detection
Date
2025-03-30T16:52:55Z (3 months ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
J.P. Osborne (U. Leicester), R. Brivio (INAF-OAB), A. D'Ai
(INAF-IASFPA), A. Melandri (INAF-OAR), D.N. Burrows (PSU), M. A.
Williams (PSU), S. Dichiara (PSU), K.L. Page (U. Leicester) and P.A.
Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the
Swift-BAT-detected burst GRB 250330A. We searched for X-ray sources in
1.4 ks of Photon Counting (PC) mode data. The total exposure at the
position of the afterglow (see below) is 5.1 ks, obtained between
T0+3.9 ks and T0+28.0 ks.
Two uncatalogued X-ray sources are detected within the estimated
3-sigma Swift-BAT error region (296 arcsec), of which one ("Source 1")
is above the LSXPS 3-sigma upper limit at this position and fading with
>3-sigma significance, and is therefore likely the GRB afterglow. Using
1474 s of PC mode data and 4 UVOT images, we find an enhanced XRT
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 252.94482, -86.88053 which is
equivalent to:
RA (J2000): 16h 51m 46.76s
Dec(J2000): -86d 52' 49.9"
with an uncertainty of 2.3 arcsec (radius, 90% confidence). This
position is 48 arcsec from the Swift-BAT position.
The light curve can be modelled with a power-law decay with a decay
index of alpha=1.01 (+0.15, -0.14).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.3 (+0.4, -0.3). The
best-fitting absorption column is 4.9 (+1.9, -1.5) x 10^21 cm^-2, in
excess of the Galactic value of 1.2 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 3.6 x 10^-11 (7.0 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 4.9 (+1.9, -1.5) x 10^21 cm^-2
Galactic foreground: 1.2 x 10^21 cm^-2
Excess significance: 3.9 sigma
Photon index: 2.3 (+0.4, -0.3)
If the light curve continues to decay with a power-law decay index of
1.01, the count rate at T+24 hours will be 7.8 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x
10^-13 (5.4 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/01299776.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/ToO_GRBs/01299776.
This circular is an official product of the Swift-XRT team.
GCN Circular 39948
Subject
GRB 250330A: Swift/UVOT Upper Limits
Date
2025-03-30T17:15:45Z (3 months ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
Via
Web form
M. H. Siegel (PSU) and S. B. Cenko (GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250330A
3944 s after the BAT trigger (Cenko et al., GCN Circ. 39938).
No optical afterglow consistent with the XRT position (Osborne et al., GCN
Circ. 39947) 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 3944 4094 147 >21.2
white 3944 4094 147 >21.2
v 4101 4300 197 >20.0
b 4921 5109 185 >20.9
u 4716 4915 197 >20.0
w1 4511 4711 197 >21.3
m2 4306 4505 197 >19.8
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.147 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 39949
Subject
GRB 250330A: BOOTES-7 early optical upper limit
Date
2025-03-30T18:13:56Z (3 months ago)
From
I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg@iaa.es>
Via
Web form
I. Perez-Garcia, A. J. Castro-Tirado, E. Fernandez-Garcia, S.-Y. Wu, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy (IAA-CSIC), C. Perez del Pulgar (Univ. de Malaga), G. Garcia-Segura (Inst. de Astronomia, UNAM), M. Gritsevich (Univ. of Helsinki), D. R. Xiong (Yunnan Observatories of CAS), Y.-D. Hu (GuangXi Univ.), B.-B. Zhang (Nanjing Univ.) and A. Maury (Space, San Pedro de Atacama), on behalf of a larger collaboration, report:
Following the detection of GRB 250330A by Swift/BAT (Cenko et al., GCNC [39938](https://gcn.nasa.gov/circulars/39938)) and Fermi (Fermi GRB Team, GCNC [39944](https://gcn.nasa.gov/circulars/39944)), the 0.6m BOOTES-7 robotic telescope at San Pedro de Atacama (Chile) responded to the alert on Nov. 9, 06:08:48 UT (i.e. 57s after trigger, and 70s after the event). Within the reported Swift/XRT error circle (Page et al., GCNC [39940](https://gcn.nasa.gov/circulars/39940)) , no optical transient is detected down to 17.6 mag (clear filter). On a coadd (620s) of images at 06:31:17 UT (mid exposure time; i.e. 23.8 min post burst), nothing is detected down to 19.3 mag, in agreement with the deeper VLT/FORS2 observations taken later on (Becerra et al., GCNC [39941](https://gcn.nasa.gov/circulars/39941)).
We thank the staff at San Pedro de Atacama Celestial Observations for their excellent support.
GCN Circular 39950
Subject
Fermi GRB 250330A: Global MASTER-Net observations report
Date
2025-03-30T19:16:02Z (3 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko,
A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin,
V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250330A ( Fermi GBM team, GCN 39944) errorbox 41642 sec after notice time and 41678 sec after trigger time at 2025-03-30 17:42:16 UT, with upper limit up to 18.5 mag. Observations started at twilight. The observations began at zenith distance = 69 deg. The sun altitude is -14.6 deg.
The galactic latitude b = -16 deg., longitude l = 316 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2828018
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
41709 | 2025-03-30 17:42:16 | MASTER-SAAO | (16h 01m 09.95s , -72d 45m 24.7s) | C | 60 | 18.1 |
41788 | 2025-03-30 17:43:36 | MASTER-SAAO | (16h 28m 26.03s , -72d 45m 15.7s) | C | 60 | 18.2 |
41868 | 2025-03-30 17:44:56 | MASTER-SAAO | (16h 02m 18.38s , -74d 39m 19.9s) | C | 60 | 18.0 |
41947 | 2025-03-30 17:46:15 | MASTER-SAAO | (16h 32m 49.13s , -74d 37m 47.3s) | C | 60 | 18.3 |
42026 | 2025-03-30 17:47:34 | MASTER-SAAO | (15h 04m 24.83s , -74d 37m 14.9s) | C | 60 | 18.4 |
42106 | 2025-03-30 17:48:54 | MASTER-SAAO | (15h 34m 57.62s , -74d 38m 25.7s) | C | 60 | 18.4 |
42186 | 2025-03-30 17:50:14 | MASTER-SAAO | (15h 09m 38.19s , -72d 45m 00.7s) | C | 60 | 18.2 |
42265 | 2025-03-30 17:51:33 | MASTER-SAAO | (15h 36m 45.01s , -72d 44m 01.7s) | C | 60 | 18.3 |
42345 | 2025-03-30 17:52:52 | MASTER-SAAO | (16h 01m 11.29s , -72d 45m 24.8s) | C | 60 | 18.2 |
42424 | 2025-03-30 17:54:12 | MASTER-SAAO | (16h 28m 23.83s , -72d 44m 12.1s) | C | 60 | 18.2 |
42866 | 2025-03-30 18:01:34 | MASTER-SAAO | (16h 02m 13.55s , -74d 39m 54.2s) | C | 60 | 17.9 |
42945 | 2025-03-30 18:02:53 | MASTER-SAAO | (16h 32m 48.33s , -74d 40m 05.2s) | C | 60 | 18.3 |
43025 | 2025-03-30 18:04:13 | MASTER-SAAO | (15h 04m 23.51s , -74d 37m 45.9s) | C | 60 | 18.4 |
43104 | 2025-03-30 18:05:32 | MASTER-SAAO | (15h 34m 50.67s , -74d 39m 22.5s) | C | 60 | 18.5 |
43184 | 2025-03-30 18:06:52 | MASTER-SAAO | (15h 09m 34.64s , -72d 44m 00.2s) | C | 60 | 18.2 |
43263 | 2025-03-30 18:08:11 | MASTER-SAAO | (15h 36m 38.09s , -72d 44m 59.8s) | C | 60 | 18.3 |
43343 | 2025-03-30 18:09:31 | MASTER-SAAO | (16h 01m 06.13s , -72d 44m 09.8s) | C | 60 | 18.2 |
45719 | 2025-03-30 18:49:07 | MASTER-SAAO | (16h 28m 13.93s , -72d 47m 17.6s) | C | 60 | 18.2 |
45798 | 2025-03-30 18:50:26 | MASTER-SAAO | (16h 02m 10.31s , -74d 39m 28.3s) | C | 60 | 18.1 |
45878 | 2025-03-30 18:51:46 | MASTER-SAAO | (16h 32m 34.04s , -74d 40m 31.3s) | C | 60 | 18.3 |
46778 | 2025-03-30 19:06:46 | MASTER-SAAO | (15h 04m 04.80s , -74d 39m 00.1s) | C | 60 | 18.5 |
46858 | 2025-03-30 19:08:05 | MASTER-SAAO | (15h 34m 34.17s , -74d 41m 15.3s) | C | 60 | 18.4 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 39957
Subject
GRB 250330A: SVOM/VT optical upper limit
Date
2025-03-31T04:35:08Z (3 months ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Z.M. Wang, A. Li (BNU), L.P. Xin, H.L. Li, Y. L. Qiu, C. Wu, Z.H. Yao, Y. Xu, P.P. Zhang, J. Wang, Y.N. Ma, X.H. Han, H.B. Cai, J.Y. Wei(NAOC) report on behalf of the SVOM/VT team:
SVOM performed two Target of Opportunity observations of GRB 250330A (Cenko et al., GCN 39938; Pathak, GCN 39944; Osborne et al., GCN 39947) in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously， starting at 2025-03-30T09:17:44 UT, and 2025-03-30T12:40:58 UT, respectively.
No sources were detected in the stacked images within the XRT source position (Page, GCN 39940).
The 3 sigma limits in VT_R is 21.7 mag (AB) with the exposure time of 3 x 100s at the medium time of 3.2 hours after the Swift BAT trigger, and 23.0 mag with the exposure of 12*120s, at the medium time of 6.8 hours after the burst.
This result is consistent with the reports (Becerra, GCN 39941; Siegel et al., GCN 39948; Perez-Garcia et al., GCN 39949; Lipunov et al., GCN 39950).
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS.
GCN Circular 39964
Subject
GRB 250330A: Fermi GBM Observation
Date
2025-03-31T06:48:11Z (3 months ago)
From
Utkarsh Pathak at IIT Bombay <utkarshpathak.07@gmail.com>
Via
Web form
U. Pathak (IITB), R. Sonawane (IISER, TVM) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:
"At 06:07:38.42 UT on 30 March 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250330A (trigger 765007663/250330255).
which was also detected by Swift-BAT (Cenko et al. 2025, GCN 39938).
The afterglow has been detected by Swift-XRT (Osborne et al. 2025, GCN 39947).
The Fermi GBM Final Localization (GCN 39944) is consistent with the Swift-BAT
and Swift-XRT positions (Page et al. 2025, GCN 39940).
The angle from the Fermi LAT boresight is 46 degrees.
The GBM light curve consists of a single emission episode with a duration
(T90) of about 4.8 s (50-300 keV). The time-averaged spectrum
from T0-0.6 to T0+6.53 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.9 +/- 0.1 and the cutoff energy,
parameterized as Epeak, is 95 +/- 8 keV.
The event fluence (10-1000 keV) in this time interval is
(1.50 +/- 0.08)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.26 s in the 10-1000 keV band is 6.5 +/- 0.3 ph/s/cm^2.
A Band function fits the spectrum equally well
with Epeak= 86 +/- 10 keV, alpha = -0.8 +/- 0.2 and beta = -2.7 +/- 0.4.
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 39970
Subject
GRB 250330A: VLT/FORS2 Afterglow Detection
Date
2025-03-31T12:35:19Z (3 months ago)
From
Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra@roma2.infn.it>
Via
Web form
Rosa L. Becerra (U Rome), Yu-Han Yang (U Rome), Simone Dichiara (PSU),
Muskan Yadav (U Rome), Eleonora Troja (U Rome), Lei Hu (CMU) and Roberto Ricci (U Rome) report on behalf of the ERC BHianca team:
We reobserved the field of GRB 250330A (Cenko et al., GCN 39938) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began at T+19.8 hours after the trigger and were carried out in the R filter at an average seeing of 1.0" and airmass about 2.5.
A comparison to our first epoch (Becerra et al., GCN 39941) reveals a fading source within
the XRT enhanced position (Evans et al., GCN 39947), located at RA, Dec (J2000) = 16:51:47.01, -86:52:51.85.
We estimate a preliminary magnitude of R~23.2 AB mag at 1.25 h post-trigger, calibrated using nearby stars from the SkyMapper Southern Survey (SMSS) Fourth Data Release (DR4) catalog (Onken et al., 2024) and not corrected for Galactic extinction.
We thank the staff at the VLT for the rapid execution of these observations.
GCN Circular 40055
Subject
GRB 250330A Swift-BAT refined analysis
Date
2025-04-04T16:15:22Z (3 months ago)
From
Mike Moss at NASA GSFC <mikejmoss3@gmail.com>
Via
Web form
H. A. Krimm (NSF), S. D. Barthelmy (GSFC),
S. B. Cenko (GSFC), R. Gupta (GSFC),
S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa),
C. B. Markwardt (GSFC), M. J. Moss (GSFC),
D. M. Palmer (LANL), T. Parsotan (GSFC),
D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU)
(i.e. the Swift-BAT team):
Using the data set from T-137 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 250330A (trigger #1299776)
(Cenko, et al., GCN Circ. 39938). The BAT ground-calculated position is
RA, Dec = 252.685, -86.875 deg which is
RA(J2000) = 16h 50m 44.5s
Dec(J2000) = -86d 52' 29.6"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 98%.
The mask-weighted light curve shows a single well defined fast-rise exponential-
decay pulse shape. the T90 (15-350 keV) is 11.27 +- 2.53 sec (estimated error
including systematics).
The time-averaged spectrum from T-0.16 to T+14.33 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.72 +- 0.10. The fluence in the 15-150 keV band is 9.2 +- 0.6 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+0.26 sec in the 15-150 keV band
is 4.0 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1299776