GRB 090417A
GCN Circular 9136
Subject
GRB 090417A: nearby galaxy redshift
Date
2009-04-17T16:27:39Z (16 years ago)
From
Nial Tanvir at IofA U.Cambridge <nrt@ast.cam.ac.uk>
P. T. O'Brien and N. R. Tanvir (U. Leicester) report:
We note that the bright 2MASS galaxy at the edge of the BAT error
circle, pointed out by Fox (GCN 9134), has a spectrum measured as part
of the 6dF survey, which gives a redshift of z=0.088. This
corresponds to a luminosity distance of about 400 Mpc in standard
cosmology, which would be very large for an SGR giant flare, but quite
plausible for a short-GRB comparable in luminosity to several others
which have been seen at moderate redshifts.
The spectrum can be seen at the following link:
http://www-wfau.roe.ac.uk/6dFGS/cgi-bin/show.cgi?release=dr3&name=g0219477-071201&tid=-1&specid=123101
GCN Circular 9137
Subject
GRB 090417A: Early-type nature of the putative host
Date
2009-04-17T17:35:29Z (16 years ago)
From
Josh Bloom at UC Berkeley <jbloom@astron.berkeley.edu>
J. S. Bloom (UC Berkeley), D. Fox (PSU), N. R. Tanvir, P. T. O'Brien
(U. Leicester), William Lee (UNAM), J. X. Prochaska (UCO/Lick) report:
We further note that the galaxy possibly associated (Fox GCN 9134)
with GRB 090417A (Mangano et al., GCN 9133) appears both visually and
spectrally to be of an early-type (smooth morphology, prominent Ca
H&K). In the 6df spectrum (O'Brien & Tanvir, GCN 9136), there is some
low-level H�� emission apparent suggesting some low-level star-
formation. However no other Balmer lines appear prominently detected
and there is no apparent [OIII] or [OII] as seen in the host galaxies
of essentially all long-soft GRB (LSB) hosts. Without a detailed
analysis, we classify this galaxy as a S0/lenticular or (more likely)
an elliptical. Given the connection of several other SHBs to
ellipticals at moderate redshift, we feel this identification can be
taken as weak observational support for a connection between this
galaxy and 090417A and further suggests that the burst was unlikely to
be due to an SGR flare-type event (O'Brien & Tanvir, GCN 9136). The
fact that the galaxy is at the edge of the BAT error circle does not
necessarily argue against it being the host: the offset from the
center of the circle, which amounts to ~320 kpc at this redshift, is
certainly within the range of plausible natal kicks of a compact
binary progenitor (~1 Gyr merger time for a 500 km/s kick).
GCN Circular 9138
Subject
GRB 090417A: Swift-BAT refined analysis
Date
2009-04-17T19:50:47Z (16 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
V. Mangano (INAF-IASFPA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL),
T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-119 to T+261 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 090417A (trigger #349447)
(Mangano, et al., GCN Circ. 9133). The BAT ground-calculated position is
RA, Dec = 34.993, -7.141 deg which is
RA(J2000) = 02h 19m 58.3s
Dec(J2000) = -07d 08' 28.9"
with an uncertainty of 2.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 30%.
The mask-weighted light curve shows a single peak starting at T-0.06 sec,
peaking at T+0.04 sec, and ending at T+0.09 sec. There appears to be
no extended emmission out to T+55 sec, at which point the burst location
went out of the BAT FOV during a planned target slew. T90 (15-350 keV)
is 0.072 +- 0.018 sec (estimated error including systematics).
The time-averaged spectrum from T-0.0 to T+0.1 sec is best fit by a power law
with an exponential cutoff. This fit gives a photon index -0.65 +- 2.11,
and Epeak of 40.3 +- 12.7 keV (chi squared 67.41 for 56 d.o.f.). For this
model the total fluence in the 15-150 keV band is 1.9 +- 0.5 x 10^-8 erg/cm2
and the 1-sec peak flux measured from T-0.46 sec in the 15-150 keV band is
3.6 +- 1.0 ph/cm2/sec. A fit to a simple power law gives a photon index
of 2.99 +- 0.36 (chi squared 77.85 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/349447/BA/
GCN Circular 9160
Subject
VLA observations of short burst GRB 090417A
Date
2009-04-19T13:23:35Z (16 years ago)
From
Poonam Chandra at U Virginia/NRAO <pc8s@virginia.edu>
P. Chandra (RMC) and D. A. Frail (NRAO) report on behalf of a larger
collaboration:
"We have used the Very Large Array (VLA) to image a field centered on
the 2MASS galaxy suggested by Fox (GCN #9134) to be a possible host of
the short duration burst 090417A (GCN # 9133, 9138). The VLA observed
the burst at a frequency of 8.46 GHz on two epochs, April 17.92 UT and
April 18.90 UT. Within a radius of 1.5 arcmin around the 2MASS galaxy
there are no radio sources detected at either epoch to a 4-sigma limit
of 104 uJy and 84 uJy, respectively. No further observations are planned.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."