GRB 190630B
GCN Circular 24913
Subject
Swift Trigger 912102: possible GRB 190630B
Date
2019-06-30T06:24:47Z (6 years ago)
From
Hans Krimm at NSF/NASA-GSFC <hkrimm@nsf.gov>
H. A. Krimm (NSF), N. J. Klingler (PSU), K. L. Page (U Leicester) and
A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 06:02:08 UT, the Swift Burst Alert Telescope (BAT) triggered and
located possible GRB 190630B (trigger=912102). Swift slewed immediately to the location.
The BAT on-board calculated location is
RA, Dec 223.669, +41.521 which is
RA(J2000) = 14h 54m 41s
Dec(J2000) = +41d 31' 16"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a single-peaked
structure with a duration of about 5 sec. The peak count rate
was ~1000 counts/sec (15-350 keV), at ~0 sec after the trigger.
This increase in flux occurred during a rise in background due to
entry to the SAA, so it is not immediately clear from the BAT data
alone that this is indeed a burst rather than a noise event.
The XRT began observing the field at 06:03:10.7 UT, 62.1 seconds after
the BAT trigger. No source was detected in the 2.5-s promptly available
image. We are waiting for the full dataset to detect and localise the
XRT counterpart.
UVOT took a finding chart exposure of 66 seconds with the White filter
starting 65 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 25% of
the BAT 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
BAT 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
0.01.
Due to the high background in the BAT and the lack of immediate
counterpart detection in the XRT, the Swift team will not be able to
confirm or deny whether this event is a GRB without further data.
Burst Advocate for this burst is H. A. Krimm (hkrimm AT nsf.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 24918
Subject
GRB 190630B, Swift-BAT refined analysis
Date
2019-06-30T16:01:10Z (6 years ago)
From
Hans Krimm at NSF/NASA-GSFC <hkrimm@nsf.gov>
J. R. Cummings (CPI), S. D. Barthelmy (GSFC), H. A. Krimm (NSF),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), F. Marshall (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU),
T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+50 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 190630B (trigger #912102)
(Krimm, et al., GCN Circ. 24913). The BAT ground-calculated position is
RA, Dec = 223.729, 41.528 deg which is
RA(J2000) = 14h 54m 55.0s
Dec(J2000) = +41d 31' 42.4"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
The mask-weighted light curve shows a single, weak pulse with a FRED-like
shape, starting from T-3 sec, peaking at T+1 sec and fading to background by
T+6 sec. We note that data is available until approximately T+250 sec. However,
after T+50 sec, the background cannot be properly subtracted due to high
background levels arising from Swift���s entry into the SAA. Therefore we only
use data prior to T+50 sec for analysis. The raw light curve shows no sign of any
burst activity after the initial pulse. T90 (15-350 keV) is 5.6 +- 0.9 sec
(estimated error including systematics).
The time-averaged spectrum from T-1.7 to T+4.7 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.36 +- 0.24. The fluence in the 15-150 keV band is 2.8 +- 0.4 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.19 sec in the 15-150 keV band
is 1.1 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
In the initial circular for GRB 190630B (Krimm, et al., GCN Circ. 24913), this event
was reported as a possible burst. After the more complete analysis carried out here,
we conclude that Swift trigger 912102 is indeed a GRB.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/912102/BA/
GCN Circular 24919
Subject
GRB 190630B: Swift-XRT refined Analysis
Date
2019-06-30T17:37:06Z (6 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
K.L. Page (U. Leicester), P.A. Evans (U. Leicester) and F.E. Marshall
(NASA/GSFC) report on behalf of the Swift-XRT team:
We have analysed 2.4 ks of XRT data for GRB 190630B, from 47 s to 28.2
ks after the BAT trigger. The data comprise 8 s in Windowed Timing
(WT) mode (taken while Swift was slewing), with the remainder in Photon
Counting (PC) mode. Using 307 s of PC mode data and 1 UVOT image, we
find an enhanced XRT position (using the XRT-UVOT alignment and
matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
223.70024, +41.52614 which is equivalent to:
RA (J2000): 14h 54m 48.06s
Dec(J2000): +41d 31' 34.1"
with an uncertainty of 3.1 arcsec (radius, 90% confidence).
The light curve can be modelled with a power-law decay with a decay
index of alpha=1.32 (+0.08, -0.07).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 3.0 (+1.1, -0.4). The
best-fitting absorption column is consistent with the Galactic value
of 1.4 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 3.0 x 10^-11 (3.3 x 10^-11) erg cm^-2 count^-1.
A summary of the WT-mode spectrum is thus:
Total column: 1 (+/-20) x 10^20 cm^-2
Galactic foreground: 1.4 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 3.0 (+1.1, -0.4)
If the light curve continues to decay with a power-law decay index of
1.32, the count rate at T+24 hours will be 6.5 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.0 x
10^-14 (2.1 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00912102.
This circular is an official product of the Swift-XRT team.
GCN Circular 24931
Subject
GRB 190630B: KAIT Optical Afterglow Confirmation
Date
2019-07-01T05:41:45Z (6 years ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to the Swift GRB 190630B (Krimm et al.,
GCN 24913; Cummings et al. GCN 24918) starting at 310s after the burst.
Observations were performed with a sequence in the clear (roughly R),
V, and I filters, and the exposure time was 60 s per image. Further
analysis on our reported afterglow candidate (Zheng & Filippenko, GCN
24914) shows that the candidate position is within the enhanced XRT
error circle (Page et al., GCN 24919), and its brightness faded more than
2 magnitude during our ~2 hours observing range. We therefore confirm
this is the optical afterglow of GRB 190630B. A preliminary KAIT clear
band light curve is available at:
http://w.astro.berkeley.edu/~zwk/grb/GRB190630B/GRB190630B_kait.jpg
GCN Circular 24943
Subject
GRB 190630B: Swift/UVOT Upper Limits
Date
2019-07-01T17:59:50Z (6 years ago)
From
Kira Simpson at PSU <kira.simpson1984@gmail.com>
GRB 190630B: Swift/UVOT Upper Limits
K. K. Simpson (PSU) and F. E. Marshall (NASA/GSFC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 190630B
65 s after the BAT trigger (Krimm et al., GCN Circ. 24913).
No optical afterglow consistent with the optical position
(Zheng and Filippenko GCN Circ. 24914)
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 initial exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white 65 131 65 >20.5
b 57357 57675 308 >20.69
uvm2 39177 40077 885 >20.36
u 46044 46193 145 >19.89
v 55313 55640 317 >18.87
uvw1 40084 40453 363 >20.02
uvw2 49543 49700 155 >19.09
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 24949
Subject
GRB 190630B: Tien Shan and Koshka Zeiss-1000 optical upper limits
Date
2019-07-01T21:13:42Z (6 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Kusakin (FAPHI), I. Reva (FAPHI), A. Novichonok
(KIAM), A. Pozanenko (IKI), E. Mazaeva (IKI), A. Volnova (IKI), I.
Molotov (KIAM) report on behalf of larger GRB IKI FuN collaboration:
We observed the field of GRB 190630B (Krimm, et al., GCN 24913) with
Zeiss-1000 1-m telescope of Tien Shan Astronomical Observatory starting
on June, 30 (UT) 18:40:21 and Koshka Observatory starting on June, 30
(UT) 20:38:42 in R-filter. We do not detect the afterglow (Zheng, et
al., GCN 24914; Zheng, et al., GCN 24931). Preliminary photometry of
the field is following
Date UT start t-T0 Filter Exp. OT Err. UL Observatory
(mid, days) (s)
2019-06-30 18:40:21 0.55999 R 6720 n/d n/d 22.3 TSHAO
2019-06-30 20:38:42 0.63060 R 3780 n/d n/d 21.9 Koshka
The photometry is based on several nearby USNO-B1.0 stars.
USNO-B1.0_id R2
1315-0255078 18.06
1314-0253302 17.18
1314-0253267 15.88