GRB 210218A
GCN Circular 29573
Subject
GRB 210218A: Swift-XRT confirmation of afterglow
Date
2021-02-26T16:32:25Z (5 years ago)
From
Boris Sbarufatti at PSU <bxs60@psu.edu>
B. Sbarufatti (PSU), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team
Swift-XRT has performed follow up observations of GRB 210218A (Sbarufatti et al. GCN Circ. 29529).
The Swift-BAT trigger happened while the burst position in the sky was Moon constrained for XRT and UVOT observations.
A first follow up observation was performed when the target emerged from Moon constraint, with one uncatalogued X-ray source (source #3) detected inside the BAT error circle (Sbarufatti et al. GCN Circ. 29542).
Swift-XRT observed the field again, for a further 4.7 ks, from T+497 ks to T+549 ks. Source #3 has faded below detection, with a 3-sigma upper limit of 2.5E-3 cts s^-1 (equivalent to 4.6E-14 erg cm^-2 s^-1 ), and is thus confirmed to be the burst afterglow.
This circular is an official product of the Swift-XRT team.
GCN Circular 29556
Subject
GRB 210218A: Swift/UVOT observations
Date
2021-02-23T14:49:18Z (5 years ago)
From
Alexander Belles at PSU/Swift <aub1461@psu.edu>
A. Belles (PSU) and B. Sbarufatti (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210218A
approximately 170 ks after the BAT trigger (B. Sbarufatti et al., GCN 29529)
due to a Moon constraint. No optical afterglow consistent with the XRT
candidate position is detected (Osborne et al., GCN 29542).
Preliminary 3-sigma upper limit using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first exposure
is:
Filter T_start(s) T_stop(s) Exp(s) Mag
wh 170031 188263 1665 >21.65
The magnitude in the table is not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.19 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 29542
Subject
GRB 210218A: Swift-XRT observations
Date
2021-02-22T15:30:25Z (5 years ago)
From
Boris Sbarufatti at PSU <bxs60@psu.edu>
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore
(U. Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) ,
M. Capalbi (INAF-IASFPA), J. D. Gropp (PSU), J.A. Kennea (PSU), A.
Tohuvavohu (U. Toronto) and M. Stamatikos (OSU) report on behalf of the
Swift-XRT team:
We have analysed 2.7 ks of Photon Counting (PC) mode XRT data for the
Swift-BAT-detected burst GRB 210218A (Stamatikos et al. GCN Circ.
29537), collected between T0+170 ks and T0+210 ks s.
One uncatalogued X-ray source has been detected consistent with being
within 296 arcsec of the Swift-BAT position, it is below the RASS limit
and shows no definitive signs of fading. Therefore, at the present time
we cannot confirm this as the afterglow. Details of this source are
given below:
Source 3:
RA (J2000.0): 47.3236 = 03:09:17.67
Dec (J2000.0): +35.3240 = +35:19:26.5
Error: 4.8 arcsec (radius, 90% conf.)
Count-rate: (5.6 [+2.0, -1.6])e-3 ct s^-1
Distance: 164 arcsec from Swift-BAT position.
Flux: (1.03 [+0.36, -0.29])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)
Two uncatalogued sources were also detected too far from the GRB
position to be likely afterglow candidates.
The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/01033328.
This circular is an official product of the Swift-XRT team.
GCN Circular 29537
Subject
GRB 210218A: Swift-BAT refined analysis
Date
2021-02-19T02:01:49Z (5 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
M. Stamatikos (OSU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), B. Sbarufatti (PSU),
T. N. Ukwatta (LANL) (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 210218A (trigger #1033328)
(Sbarufatti et al., GCN Circ. 29529). The BAT ground-calculated position is
RA, Dec = 47.318, 35.322 deg which is
RA(J2000) = 03h 09m 16.3s
Dec(J2000) = +35d 19' 18.9"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 57%.
The mask-weighted light curve shows a multi-peaked structure that
starts at ~T-15 s and peaks at ~T0. The burst emission lasted
until the burst went out of the BAT FOV at T+287 s.
Using the available data, the lower limit of T90 is ~ 240 s.
The time-averaged spectrum from T-14.27 to T+266.26 sec is best fit by
a power law with an exponential cutoff. This fit gives a photon
index 0.77 +- 0.49, and Epeak of 91.3 +- 48.2 keV (chi squared 50.53
for 56 d.o.f.). For this model the total fluence in the 15-150 keV
band is 4.3 +- 0.3 x 10^-6 erg/cm2 and the 1-sec peak flux measured
from T+0.09 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 1.46 +- 0.11
(chi squared 57.43 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/1033328/BA/
GCN Circular 29532
Subject
GRB 210218A: MITSuME Akeno optical upper limits
Date
2021-02-18T15:33:22Z (5 years ago)
From
Ogawa Futa at Tokyo Institute of Technology <ogawa@hp.phys.titech.ac.jp>
F. Ogawa, R. Hosokawa, K. L. Murata, R. Adachi, M. Niwano, N.
Nakamura, N. Ito, S. Ogata, H. Takamatsu, H. Hara, Y. Yatsu, and N.
Kawai (TokyoTech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 210218A (Sbarufatti et al. GCN #29529,
Zhu et al. GCN #29530, Xin et al. GCN #29531) with the optical three
color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm
telescope of Akeno Observatory, Yamanashi, Japan. The observation with
a series of 10 sec exposures started at 2021-02-18 13:36:05 UT(46
seconds after the Swift BAT trigger). We stacked the images with good
conditions. We did not find any new point sources within the Swift BAT
circle (Sbarufatti et al. GCN #29529) in all three bands.
We obtained the 5-sigma limits of the stacked images as follows.
T0+[sec] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
46 14:03:01 1220 g'>17.3, Rc>17.5, Ic>16.7
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used the UCAC4 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 29531
Subject
GRB 210218A： GWAC-F60A optical upper limit
Date
2021-02-18T14:42:03Z (5 years ago)
From
Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>
L. P. Xin(NAOC), J. Wang(GXU), C. Gao(GXU), X. H. Han(NAOC), J. Y. Wei(NAOC),
G. W. LI(NAOC), L. H. Li(NAOC), C. Wu(NAOC), X. G. Wang(GXU),
E. W. Liang (GXU), R. S. Zhang(NAOC), Y. L. Qiu(NAOC),
and J. S. Deng(NAOC) report:
We began to observe GRB 210218A (Sbarufatti al., GCN 29529)
with Xinglong GWAC-F60A telescope, China, at 11:37:45 (UT),
18th. Feb. 2021, about 146 sec after the burst, under bad seeing condition.
A series of R, I images were obtained.
Preliminary analysis shows that no any new optical source
was found in single images within the Swift errorbox (Sbarufatti al., GCN 29529),
down to the 3 sigma upper limit of 15.0 mag in R band.
The upper limit is calibrated to the USNO B1.0 catalog.
This result is consistent with the previous report (Zhu et al., GCN 29530).
GCN Circular 29530
Subject
GRB 210218A: NEXT optical upper limit
Date
2021-02-18T14:28:05Z (5 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
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 210218A (Sbarufatti et al., GCN 29529)
using the NEXT-0.6m optical telescope located at Nanshan, Xinjiang,
China. Observations automatically started at 13:36:52 UT on 2021-02-18,
i.e., 93 s after the BAT trigger. We obtained 3x40 s, 4x60 s and 12x90 s
frames in the Sloan r-filter.
No credible optical transient is detected in our stacked image within
the Swift/BAT error circle, down to a limiting magnitude of r ~ 20.4,
calibrated with the nearby PanSTARRS field.
GCN Circular 29529
Subject
GRB 210218A: Swift detection of a burst
Date
2021-02-18T13:45:55Z (5 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
B. Sbarufatti (PSU), N. J. Klingler (PSU), N. P. M. Kuin (UCL-MSSL),
A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC) and
K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 13:35:19 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210218A (trigger=1033328). Swift did not slew
immediately due to an observing constraint.
The BAT on-board calculated location is
RA, Dec 47.291, +35.287 which is
RA(J2000) = 03h 09m 10s
Dec(J2000) = +35d 17' 14"
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 ~0 sec after the trigger.
Due to a Moon observing constraint, Swift cannot slew to the BAT
position until 11:37 UT on 2021 February 20. There will thus be no XRT
or UVOT data for this trigger before this time.
Burst Advocate for this burst is B. Sbarufatti (bxs60 AT psu.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/)