GRB 080905A
GCN Circular 8208
Subject
GRB080905A: Swift/UVOT Upper Limits
Date
2008-09-10T13:18:20Z (17 years ago)
From
Peter Brown at PSU <pbrown@astro.psu.edu>
P. J. Brown and C. Pagani (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT observed the field of GRB 080905A
starting about 114 s after the BAT detection
(Pagani et al., GCN Circ. 8180). We do not detect
any source in the revised XRT error circle (Evans et
al., GCN Circ. 8203) including the faint optical afterglow
seen by Malesani et al. (GCN Circ. 8190)
in any of the UVOT filters down to the following 3 sigma
upper limits (where T_start and T_stop represent the
elapsed time since the BAT trigger in seconds).
Filter T_start(s) T_stop Exp(s) MagLimit
white 114 970 198 >21.3
uvw2 730 750 19 >18.1
uvm2 626 4520 95 >19.2
uvw1 651 825 39 >18.8
u 675 850 39 >19.2
b 700 865 15 >18.9
v 220 1250 1014 >20.6
The above magnitudes are not corrected for the Galactic extinction
corresponding to a reddening of E(B-V) = 0.14 mag (Schlegel et al.,
1998, ApJS, 500, 525). The photometry is on the UVOT photometric
system described in Poole et al. (2008, MNRAS, 383,627).
GCN Circular 8204
Subject
GRB 080905A: Fermi Gamma-ray Burst Monitor detection
Date
2008-09-09T12:03:02Z (17 years ago)
From
Elisabetta Bissaldi at MPE <ebs@mpe.mpg.de>
E. Bissaldi, S. McBreen (MPE), V. Connaughton (UAH) and
A. von Kienlin (MPE) report on behalf of the
Fermi Gamma-ray Burst Monitor Team:
"At 11:58:55 UT on 5 September 2008, the Fermi GBM triggered
and located GRB 080905A (trigger 242308736 / 080905499), which was
also detected by Swift (Pagani et al., GCN 8180). The on-ground
calculated location, using the Fermi GBM trigger data, is
RA = 286.3, Dec = -18.2 (J2000 degrees) (equivalent to J2000
19h 05m, -18d 12'), with a statistical uncertainty of 4.6 degree
(radius, 1-sigma containment; there is additionally a systematic
error which is currently estimated to be 2 to 3 degrees).
This position is 1.5 deg from the Swift refined position
(Evans et al., GCN 8203). The angle from the Fermi LAT boresight
to the Swift position is 28 degrees.
This short GRB consists of two peaks, the first from T0 to
T0+0.4 sec and the second from T0+0.6 sec to T0+1.1 sec.
The first peak shows substructure in agreement with
the Swift-BAT refined analysis (J. Cummings et al., GCN 8187).
T90 (50-300 keV) is about 1 sec.
The time-averaged spectrum from T0 to T0+1 sec is well fit
by a power law function with index -0.96 +/- 0.05.
The fluence (50-300 keV) is 2.8(+/-0.2)E-07 erg/cm2
and the peak flux (50-300 keV) is 6.1 +/- 0.8 ph/cm2/s.
The spectral analysis results presented above are preliminary;
final results will be published in the Fermi GBM GRB Catalog."
GCN Circular 8203
Subject
GRB 080905A: Enhanced Swift-XRT position
Date
2008-09-08T15:06:05Z (17 years ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
P.A. Evans, J.P. Osborne and M.R. Goad (U. Leicester) report on behalf
of the Swift-XRT team:
Using more data than were available at the time of de Ugarte Postigo et
al. (GCN Circ 8195), the UVOT-enhanced X-ray position of GRB 080905A has
been improved to RA, Dec = 287.67390, -18.88022 which is equivalent to:
RA (J2000): 19 10 41.74
Dec (J2000): -18 52 48.8
with an uncertainty of 1.6 arcsec (90% confidence). This position lies
1.5" from the optical counterpart identified by Malesani et al (GCN
Circ. 8190), consistent with that position.
Position enhancement, using the XRT-UVOT alignment and matching to the
USNO-B1 catalogue, is described by Goad et al. (2007, A&A, 476, 1401
http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is
an extension of this method.
This circular is an official product of the Swift-XRT team.
GCN Circular 8202
Subject
GRB 080905A: MITSuME Akeno optical upper limits
Date
2008-09-08T13:33:19Z (17 years ago)
From
Nobuyuki Kawai at Tokyo Tech <nkawai@hp.phys.titech.ac.jp>
H. Nakajima, T. Shimokawabe, Y.A. Mori, Y. Kudou, and N. Kawai (Tokyo
Tech) report on behalf of the MITSuME collaboration:
We performed optical imaging observation of the field of GRB 080905A
(C. Pagani et al. GCN 8180) with the 3-color 50cm MITSuME Telescope at
Akeno, Japan from 12:40:12 UT (42min after the trigger) to 14:32:07 UT.
In the co-added images of Ic, Rc, and g' bands, we did not detect any
afterglow candidate in the XRT error circle. The 3-sigma limiting
magnitudes based on USNO-B1.0 (I-band) and NOMAD (R-band,g'-band)
stars are following:
Filter Start(UT) End(UT) Exposure LimitMag
---------------------------------------------------
g' 12:40:12 13:14:31 30 x 60 s 17.1
Rc 12:40:12 13:14:31 30 x 60 s 17.6
Ic 12:40:12 13:14:31 30 x 60 s 17.6
---------------------------------------------------
GCN Circular 8195
Subject
GRB 080905A: optical afterglow
Date
2008-09-07T10:35:30Z (17 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@astro.ku.dk>
A. de Ugarte Postigo (ESO), D. Malesani (DARK/NBI), A. J. Levan (Univ.
Warwick), J. Hjorth (DARK/NBI), N. R. Tanvir (Univ. Leicester), report
on behalf of a larger collaboration:
We observed again the field of the short GRB 080905A (Pagani et al., GCN
8180) with the ESO VLT equipped with FORS2. R-band observations were
carried out starting on 2008 Sep 7.004 UT (1.50 days after the GRB) and
the total exposure time was 40 minutes.
The object located inside the XRT error circle visible in our early VLT
images (Malesani et al., GCN 8190) has clearly faded between the two
observations, and is thus likely the optical afterglow of GRB 080905A.
We note that this object is located outside the revised 2.2"-radius
(90%) UVOT-enhanced XRT error circle (distance from center 4.6"), as
provided at http://www.swift.ac.uk/xrt_positions/index.php (value of Sep
7.4 UT).
In our second epoch image, which is deeper and has a better seeing
(~0.9"), we also note the presence of a bright extended object, possibly
a spiral galaxy, about 9" S, 3" E of the afterglow (partially covered by
foreground stars).
Finding charts can be found at
http://www.astro.ku.dk/~malesani/GRB/080905A/#epoch2
We acknowledge significant support from the ESO observing staff at
Paranal, in particular Elena Mason, Andres Pino and Swetlana Hubrig.
GCN Circular 8190
Subject
GRB 080905A: NOT and VLT observations
Date
2008-09-06T18:40:26Z (17 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@astro.ku.dk>
D. Malesani (DARK/NBI), A. de Ugarte Postigo (ESO), J. P. U. Fynbo
(DARK/NBI), A. J. Levan (Univ. Warwick), E. Rol (Univ. Leicester), N. R.
Tanvir (Univ. Leicester), C. C. Thoene (DARK/NBI), J. Telting (NOT), A.
Baran (Cracow Univ.), report on behalf of a larger collaboration:
We observed the field of the short GRB 080905A (Pagani et al., GCN 8180)
with the NOT and the VLT telescopes equipped with ALFOSC and FORS2,
respectively. The NOT observations started on 2008 Sep 5.854 UT (8.51 hr
after the GRB) and the total exposure time was 30 min. The VLT
observations started on 2008 Sep 6.097 UT (14.3 hr after the GRB) and
the total exposure was 40 min. All images were taken with the R filter.
Inside the XRT error circle, we detect a single, faint source with R ~
24 (against USNO-B1 stars), visible in both the NOT and VLT images. No
variability of the source can be robustly determined, hence we cannot
assess the relationship of this object with the GRB, especially given
the relatively crowded field (Galactic latitude -12.6). Further
observations are planned.
The coordinates of this object are:
RA(J2000) = 19:10:41.73
Dec(J2000) = -18:52:47.3
with an error of ~0.6".
We note that in our NOT images (seeing ~1"), the extended objects
identified by Tristram et al. (GCN 8181) appear resolved into several
pointlike sources.
Finding charts can be found at the following URL:
http://www.astro.ku.dk/~malesani/GRB/080905A
We acknowledge significant support from the observing staff at Paranal,
in particular Swetlana Hubrig, Elena Mason and Andres Pino.
GCN Circular 8187
Subject
GRB 080905A, Swift-BAT refined analysis
Date
2008-09-06T16:51:33Z (17 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
J. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. Baumgartner (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), D. Palmer (LANL), C. Pagani (PSU),
T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. Ukwatta (GWU)
(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 080905A (trigger #323870)
(Pagani, et al., GCN Circ. 8180). The BAT ground-calculated position is
RA, Dec = 287.663, -18.865 deg, which is
RA(J2000) = 19h 10m 39.1s
Dec(J2000) = -18d 51' 55.4"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 56%.
The mask-weighted light curve shows three peaks; the first two are partially
overlapping, starting at T+0.0 and ending at ~T+0.4 sec. The third peak
starts at ~T+0.6 and ends at ~T+1.3 sec. T90 (15-350 keV) is 1.0 +- 0.1 sec
(estimated error including systematics).
The time-averaged spectrum from T+0.0 to T+1.1 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
0.85 +- 0.24. The fluence in the 15-150 keV band is 1.4 +- 0.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.04 sec in the 15-150 keV band
is 1.3 +- 0.2 ph/cm2/sec. 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/323870/BA/
GCN Circular 8185
Subject
GRB 080905A: Swift-XRT Refined Analysis
Date
2008-09-06T02:31:56Z (17 years ago)
From
Claudio Pagani at PSU/Swift-XRT <pagani@astro.psu.edu>
C. Pagani and J. Racusin (PSU) report on behalf of the Swift-XRT team:
We have analyzed the first orbit of Swift-XRT data for the short GRB 080905A
(Pagani et al., GCN 8180) beginning at T0+130 seconds to T0+1.1 ks.
The enhanced XRT position given in GCN Circ 8180 is 40 arcseconds from the BAT
onboard position, within the BAT error circle.
The XRT lightcurve shows an initial count rate of approximately 6 counts/s for
the first 100 seconds of observations, followed by a steep decay and a
shallower phase. The decaying lightcurve can be fit with a broken power-law
with an initial decay index of 6.4+/-2.0, a break at approximately T0+400
seconds and a later decay index of 1.0+/-0.5.
The spectrum of 1 ks of Photon counting mode data from the first orbit can be
fit by an absorbed power-law with a photon index of 1.3+/-0.3 and absorption
consistent with the Galactic value along the line of sight (9e20 cm^-2,
Kalberla et al. 2005). The average observed (unabsorbed) flux of the PC mode
data is 2.9e-9 (3.1e-10) ergs cm^-2 s^-1.
Assuming the X-ray emission continues to decline at the same rate, we predict a
0.3-10.0 keV XRT count rate of 0.001 counts/s at T+24hr, which corresponds to
an observed flux of 7e-14 ergs cm^-2 s^-1.
This Circular is an official product of the Swift-XRT team.