GRB 180410A
GCN Circular 22620
Subject
GRB 180410A: Swift detection of a burst or a Galactic transient.
Date
2018-04-10T08:27:45Z (7 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
J.D. Gropp (PSU), A. Deich (PSU), P. A. Evans (U Leicester),
C. Gronwall (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC) and
K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 08:02:59 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180410A or a Galactic transient (trigger=824063).
Swift slewed immediately to the source.
The BAT on-board calculated location is
RA, Dec 95.981, +12.808 which is
RA(J2000) = 06h 23m 56s
Dec(J2000) = +12d 48' 28"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a complex structure
structure with a duration of about 100 sec. The peak count rate
was ~800 counts/sec (15-350 keV), at ~26 sec after the trigger.
The XRT began observing the field at 08:05:49.8 UT, 170.7 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
95.9570, 12.8110 which is equivalent to:
RA(J2000) = 06h 23m 49.68s
Dec(J2000) = +12d 48' 39.4"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 84 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 http://www.swift.ac.uk/sper.
A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 6.56
x 10^21 cm^-2 (Willingale et al. 2013).
The initial flux in the 2.5 s image was 1.55e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 179 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.
Given the source's proximity (0.17 degrees) to the Galactic Plane, and
the fact that this is a BAT image trigger, we cannot rule out that
this may be a new Galactic Transient, rather than a GRB. If it is a
transient, we name it Swift J0623.9+1248.
Burst Advocate for this burst is J.D. Gropp (jdg44 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/too.html.)
GCN Circular 22622
Subject
GRB 180410A: Enhanced Swift-XRT position
Date
2018-04-10T11:09:33Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester)
report on behalf of the Swift-XRT team.
Using 1707 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 180410A, 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 = 95.95717, +12.81143 which is equivalent
to:
RA (J2000): 06h 23m 49.72s
Dec (J2000): +12d 48' 41.1"
with an uncertainty of 1.8 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 22623
Subject
GRB 180410A: MITSuME Akeno optical upper limits
Date
2018-04-10T12:31:10Z (7 years ago)
From
Ryosuke Itoh at Tokyo Institute of Tech. <itoh@hp.phys.titech.ac.jp>
R. Itoh, K. L. Murata, Y. Tachibana, S. Harita, K. Morita, T. Ozawa, H. Mamiya,
K. Shiraishi, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We searched for the optical counterpart of GRB 180410A (J. D. Gropp et
al., GCN Circular #22620)
with the optical three color (g', Rc, and Ic) CCD cameras attached to
the MITSuME 50cm telescope
of Akeno Observatory, Yamanashi, Japan.
The observation started on 2018-04-10 10:02:24 UT.
We did not find any point source at the position of the XRT error
circle (P. A. Evans et al., GCN Circular #22622)
in all three bands. We obtained following limits for the magnitudes.
T0+[hour] MID-UT T-EXP[sec] g' Rc Ic
-------------------------------------------------------------------------------------------------------
~2.0 10:27:25 2,700 >18.8 >18.7 >18.0
-------------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used UCAC-4 catalog for flux calibration.
GCN Circular 22627
Subject
GRB 180410A: Swift/UVOT Upper Limits
Date
2018-04-10T18:18:04Z (7 years ago)
From
Frank Marshall at Swift/UVOT <marshall@milkyway.gsfc.nasa.gov>
F. E. Marshall (NASA/GSFC) and J. D. Gropp (PSU)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 180410A
179 s after the BAT trigger (Gropp et al., GCN Circ. 22620).
No optical afterglow consistent with the enhanced XRT position
(Evans et al. GCN Circ. 22622)
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 179 329 147 >20.6
u_FC 338 587 246 >20.0
white 179 2068 450 >20.9
v 669 1943 156 >19.2
b 594 2043 156 >20.1
u 338 2017 382 >20.4
w1 718 1993 136 >20.1
m2 693 1968 136 >20.3
w2 644 2093 175 >19.9
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.92 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 22628
Subject
GRB 180410A: Swift-BAT refined analysis
Date
2018-04-10T21:03:41Z (7 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
A. Y. Lien (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), J. D. Gropp (PSU),
H. A. Krimm (NSF/USRA), C. B. Markwardt (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-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180410A (trigger #824063)
(Gropp et al., GCN Circ. 22620). The BAT ground-calculated position is
RA, Dec = 95.974, 12.804 deg which is
RA(J2000) = 06h 23m 53.7s
Dec(J2000) = +12d 48' 15.2"
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 53%.
The mask-weighted light curve shows a weak-long pulse that starts and peak
at ~ T+25 s, and ends at ~T+150 s. T90 (15-350 keV) is 100.7 +- 13.8 sec
(estimated error including systematics).
The time-averaged spectrum from T+25.16 to T+153.67 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.46 +- 0.13. The fluence in the 15-150 keV band is 2.2 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+25.70 sec in the 15-150 keV band
is 0.7 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The spectral and temporal behaviors are consistent with those of a GRB. However,
due to the proximity to the Galactic plane (0.17 degrees), we cannot rule out the
possibility that this is a Galactic transient.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/824063/BA/
GCN Circular 22629
Subject
GRB 180410A: Swift-XRT refined Analysis
Date
2018-04-10T23:40:51Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), Z. Liu (NAOC /
U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri
(INAF-OAB), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), D.N.
Burrows (PSU) and J.D. Gropp report on behalf of the Swift-XRT team:
We have analysed 6.8 ks of XRT data for GRB 180410A (Gropp et al. GCN
Circ. 22620), from 176 s to 45.6 ks after the BAT trigger. The data
comprise 201 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Evans et al. (GCN Circ. 22622).
The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=1.39 (+0.22, -0.28). At T+321 s the decay
steepens to an alpha of 2.9 (+0.4, -0.3) before breaking again at T+866
s to a final decay with index alpha=1.48 (+0.15, -0.13).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.87 (+0.07, -0.05). The
best-fitting absorption column is consistent with the Galactic value
of 6.6 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has
a photon index of 1.45 (+0.21, -0.19) and a best-fitting absorption
column of 7.7 (+2.3, -1.2) x 10^21 cm^-2. The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum is 6.2 x 10^-11 (8.1 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 7.7 (+2.3, -1.2) x 10^21 cm^-2
Galactic foreground: 6.6 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.45 (+0.21, -0.19)
If the light curve continues to decay with a power-law decay index of
1.48, the count rate at T+24 hours will be 6.1 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.7 x
10^-14 (4.9 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/00824063.
This circular is an official product of the Swift-XRT team.
GCN Circular 22631
Subject
GRB 180410A: RATIR Optical Observations
Date
2018-04-11T16:03:38Z (7 years ago)
From
Alan M. Watson at Instituto de Astronomia UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC),
William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI),
J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara
(UVI), Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico
Ramirez-Ruiz (UCSC), Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM),
Harvey Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and
Vicki Toy (UMD) report:
We observed the field of GRB 180410A (Gropp et al., GCN 22620) with the
Reionization and Transients Infrared Camera (RATIR; www.ratir.org) on the
1.5m Harold Johnson Telescope at the Observatorio Astron��mico Nacional on
Sierra San Pedro M��rtir from 2018/04 11.13 to 2018/04 11.25 UTC (19.10
to 21.87 hours after the BAT trigger), obtaining a total of 2.13 hours
exposure in the r and i bands.
For a source within the Swift-XRT error circle, in comparison with the USNO-B1 and 2MASS catalogs, we
obtain the following upper limits (3-sigma):
r > 24.20
i > 23.90
These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.
The XRT error region is only 2.8 arcsec from a previously cataloged star with r = 18.1 and i = 17.4. Thus, our formal upper limits given above may be optimistic.
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.
GCN Circular 22636
Subject
GRB 180410A: Fermi GBM observation
Date
2018-04-12T08:27:16Z (7 years ago)
From
Elisabetta Bissaldi at INFN,Bari <elisabetta.bissaldi@ba.infn.it>
E. Bissaldi (Politecnico & INFN Bari)
reports on behalf of the Fermi GBM Team:
"At 08:03:27.79 UT on 10 April 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180410A (trigger 545040212 / 180410336),
which was also detected by the Swift/BAT
(Gropp et al. 2018, GCN 22620, Lien et al., GCN 22628).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 108 degrees.
The GBM light curve consists of an initial peak followed by a weaker
emission episode with a duration (T90) of about 100 s (50-300 keV).
The time-averaged spectrum from T0-3 s to T0+47 s is
adequately fit by a simple power law function with index -1.53 +/- 0.04.
The event fluence (10-1000 keV) in this time interval is
(3.1 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-1.5 s in the 10-1000 keV band
is 1.51 +/- 0.27 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."