GRB 060912A, GRB 060912

P. Jakobsson, A. Levan, R. Chapman (U. Hertfordshire), E. Rol,
N. Tanvir (U. Leicester), P. Vreeswijk (ESO), D. Watson (DARK, NBI)

We obtained 6*1200 s spectra of the proposed host galaxy of
GRB 060912A (Levan et al. GCN 5573
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 ), using FORS2 on the VLT.
The combined spectrum shows a very strong emission line at 7218A
which we identify with [OII] 3727A at a redshift of z = 0.937. At
the same redshift we also identify H-gamma in emission and possibly
NeIII 3869A. The properties of this host galaxy (in particular
strong [OII] emission) are similar to those seen in long-duration
GRB hosts. We conclude that the proximity of this burst to a low
redshift elliptical galaxy was most likely coincidental.

We thank the VLT staff for their assistance in these observations.

P. Chandra (UVA/NRAO) and  D. A. Frail (NRAO) report on behalf of
the Caltech-NRAO-Carnegie GRB Collaboration:

"We observed the field centered on the BAT position of the Swift burst GRB
060912A (GCN#5562
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 ) using the VLA at a frequency of 8.46 GHz and starting
at 8.19 UT on September 14, 2006.  There is no detection of the GRB with
2-sigma upper limit of 65 microJy.

The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc."

A.J. Levan, P. Jakobsson, R. Chapman (U. Hertfordshire), N. Tanvir, E.Rol
(U. Leicester) report for a larger collaboration:

We observed the location of GRB 050912A using the VLT and FORS1 in the VRI
bands beginning at Sept 14. 03:51 UT. At the location of the optical
afterglow given by Hurkett et al. (GCN Circ. 5558
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 ) we find an extended
source which we suggest is the host galaxy of GRB 060912A. The location
of the afterglow lies at the eastern end of this galaxy and the afterglow
may still contribute significantly at this time.

Images of the field can be found at

http://star-www.herts.ac.uk/~levan/060912A/

We thank the staff of the VLT for their assistance with these
observations.

S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and
T. Cline on behalf of the Konus-Wind team report:

The GRB 060912 (Swift-BAT trigger 229185, GCN 5558
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 )
triggered Konus-Wind at 50157.788 s UT (13:55:57.788).
As observed by Konus-Wind, it had a duration of ~8 s.
Its spectrum is well fitted by a power law model in
the energy range 20 keV - 2 MeV, with
alpha = -1.94 +/- 0.2 for time interval T0 - (T0 + 8s).

The burst fluence is ~4x10-6 erg/cm2 and the 256-ms peak flux
is 1.8x10-6 erg/cm2 s (both in the 20 keV - 2 MeV energy range).

E. Berger (Carnegie Observatories) reports on behalf of a larger 
collaboration:

"Starting on 2006 Sep. 13.22 UT we used GMOS on Gemini-South to obtain an 
1800 sec spectrum of the bright 2MASS galaxy located 11" away from the 
optical afterglow position of GRB 060912 (GCN 5558
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 ), at a position angle 
that also included the afterglow position.  The spectrum of the 2MASS 
galaxy it typical of an early-type galaxy with CaII H&K, Mg b, and Na D 
absorption features at a redshift, z=0.0936.  At the position of the 
afterglow we do not detect any clear continuum emission or emission lines 
(4000-7000 A).  If the 2MASS galaxy is in fact the host galaxy of GRB 
060912, then the isotropic-equivalent gamma-ray energy is only 2.6e49 erg. 
Moreover, the nature of the host galaxy would suggest that the GRB is most 
likely to be a short burst.  Deep imaging observations to search for a 
faint galaxy at the position of the afterglow are planned."

B. Hafizov,  M. Ibrahimov  (MAO),  A. Pozanenko (IKI), on behalf of larger
GRB follow up collaboration report:

We observed the afterglow of GRB060912 (Hurkett et al. GCN 5558
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 ) with 1.5m
telescope of Maidanak Astronomical Observatory (MAO) in BR-bands on
September 12  between  (UT) 17:25 and 19:30.  The afterglow candidate
(Hurkett et al. GCN 5558
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 ,   Zhai et al. GCN 5560
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 ) is detected on a single
120 s images. Preliminary photometry of the optical transient in R-band at
Sep. 12 17:30 (UT)  is R~20.5m.

P. J. Brown (PSU) & C. P. Hurkett (U Leicester)
report on behalf of the Swift UVOT team:

Swift/UVOT began settled observations of
GRB060912 (BAT trigger 229185) at 13:57:47 UT,
113 seconds after the initial Swift BAT trigger
(Hurkett et al., GCN Circ. 5558
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 ).  The fading
optical counterpart seen in the white finding
charts was also detected by UVOT in V, B, U, UVW1
and marginally in UVM2.  The relatively shallow
upper limit in UVW2 prevents us from constraining
the redshift well.

The magnitudes from early observations and the
upper limit in UVW2 are tabulated below.

Filter  T_range(s)    Exp(s)     Magnitude

White   113-212       100        16.0 +/- 0.1
White   859-958       100        18.1 +/- 0.1

V       219-618       400        17.4 +/- 0.1
V       964-1363      400        18.4 +/- 0.2

B       697-1776      79         19.5 +/- 0.4

U       672-691       20         17.6 +/- 0.2

UVW1    649-668       20         18.51 +/- 0.4

UVM2    624-1861      119        19.3 +/- 0.4

UVW2    725-1814      78       > 19.5 (3.0-sigma)

T_range is the span of the exposure in seconds
from the BAT trigger.

The values quoted above are not corrected for
the expected Galactic extinction corresponding
to a reddening of E(B-V)=0.05.

A. Stefanescu, F. Schrey, S. Duscha, M. Muehlegger, N. Primak,
G. Kanbach, H. Steinle (MPE Garching) of the OPTIMA-Burst Team report 
the following:

"OPTIMA-Burst at the 1.3m Skinakas Observatory, of the University of
Crete, Greece observed the Swift XRT-errorcircle of GRB 060912 (GCN 
Circ. 5558
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 , C.P. Hurkett et al.) starting at 19:21UT (~5.5h after the 
Burst).

We detect a source consistent with the source reported by C.P. Hurkett 
et al. and M. Zhai et al. (GCN Circ. 5560
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 ). We estimate the magnitude of 
the source as R=21.6 +- 0.2

There is no known minor planet brighter than 23 mag within 5' of the 
source according to MPChecker"

C. P. Hurkett, K.L. Page and E. Rol (U Leicester)
report on behalf of the Swift XRT team:

We have analysed the Swift XRT data from the first orbit observation
of GRB 060912 (Hurkett et al., GCN 5558
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 ), with a total exposure of
1.7 ks seconds.  The refined XRT position is:

   RA(J2000) =  00 21 08.23
  Dec(J2000) = +20 58 15.8

This position is 10.9 arcseconds from the BAT position given in GCN
5558
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  (Hurkett et al. 2006), 2.8 arcseconds from the XRT position and
2.0 arcseconds from the UVOT given in the same GCN. We estimate an
uncertainty of 3.6 arcseconds radius (90% containment).

The 0.3-10.0 keV Photon Counting (PC) mode starts 135 seconds after the 
BAT trigger (T0). The count rate is declining with a decay slope of 0.62 
(+/-0.12).

A preliminary spectral fit to the PC data gives a spectral power law 
photon index of 2.08 +/- 0.20 in the [0.3-10] keV band, with a free 
absorption of 0.17 (+/- 0.06)e22 cm^-2 (Galactic absorption at this 
location is 4.20e20 cm^-2).  The average (in the time range 135-1860 
seconds from trigger) estimated unabsorbed 0.3-10 keV flux is then about 
2.9E-11 erg/cm2/s.

The XRT count rate extrapolated to T0+24 hr is estimated to be about 0.025 
cps, corresponding to an unabsorbed 0.3-10 keV flux of about 1.73E-12 
erg/cm2/s.

This Circular is an official product of the Swift XRT Team.

A. Parsons (GSFC), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMD), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (BYU-Idaho), C. P. Hurkett (U Leicester), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), J. Norris (GSFC), D. Palmer (LANL),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC)
on behalf of the Swift-BAT team:
 
Using the data set from T-120 to T+183 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 060912 (trigger #229185)
(Hurkett, et al., GCN Circ. 5558
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 ).  The BAT ground-calculated position
is RA,Dec = 5.286,+20.971 deg {0h 21m 8.7s,+20d 58' 16.3"} (J2000)
+- 0.9 arcmin, (radius, sys+stat, 90% containment).  The partial coding was 33%.
 
The mask-weighted lightcurve has a single peak with a faster rise than decay.
T90 (15-350 keV) is 5.0 +- 0.5 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.6 to T+6.1 is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.74 +- 0.09.  The fluence in the 15-150 keV band is 1.3 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T-0.02 sec in the 15-150 keV
band is 8.5 +- 0.4 ph/cm2/sec.  All the quoted errors are at the 90%
confidence level. 

The spectral lag calculation (Norris & Bonnell, ApJ, 2006) shows this
burst to be clearly in the long-burst class.  The lag is 190 +28 -40 ms
between the 15-25 and 50-100 keV bands and 83 +43 -43 ms
between the 25-50 and 100-350 bands.

M.Zhai, L.P. Xing, Y.L. Qiu, J.Y. Wei, J.Y. Hu,
J.S. Deng, Y. Urata and W.K. Zheng,
on behalf of EAFON report:

We have imaged the field of GRB 060912 with the TNT 0.8m telescope at
Xinglong Observatory.The first image was taken at 13:57:23 UT, 89s
after the burst. The optical counterpart (Hurkett et al. GCN 5558
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 )
were well detected in our clear and R band images.Preliminary analysis
shows the OT fade to ~19 about 35 minutes after the burst in our white
images. We encourage deeper observation.
Further analysis is under progress.

This message may be cited.

We apologize for the mistake about the character format.

This is a multi-part message in MIME format.

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C. P. Hurkett (U Leicester), S. D. Barthelmy (GSFC),
P. J. Brown (PSU), D. N. Burrows (PSU), M. M. Chester (PSU),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
O. Godet (U Leicester), C. Guidorzi (Univ Bicocca&INAF-OAB),
S. T. Holland (GSFC/USRA), S. Immler (GSFC/USRA), J. A. Kennea (PSU),
H. A. Krimm (GSFC/USRA), F. E. Marshall (NASA/GSFC),
K. M. McLean (LANL/UTD), P. T. O'Brien (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC),
P. Romano (INAF-OAB), T. Sakamoto (NASA/ORAU), G. Sato (GSFC/ISAS),
M. Stamatikos (NASA/ORAU) and H. Ziaeepour (UCL-MSSL) report on
behalf of the Swift Team:

At 13:55:54 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 060912 (trigger=229185).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA,Dec 5.286, +20.971 {00h 21m 09s, +20d 58' 17"} (J2000)
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single FRED-like peak
(FWHM ~3 sec) with a total duration of about 7 sec.  The peak count rate
was ~6000 counts/sec (15-350 keV), at ~1 sec after the trigger.  We note that the 
spectrum is hard and the main emission is confined to ~3 sec.  It is possible that 
the burst is short, although it appears with existing data to be long.  A lag 
analysis will be done with the event data in ~3 hours. 

The XRT began taking data at 13:57:43 UT, 109 seconds after the BAT
trigger. The XRT on-board centroid algorithm did not find a source in
the image but ground analysis of flight data reveals a fading source
at Ra, Dec 00h 21m 08.2 +20 58 18.6 (J2000), with an uncertainty of
3.9" (radius, 90% containment). This is 7 arcseconds from the BAT
position and 1 arcsecond from the UVOT position. 

UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 113 seconds after the BAT trigger. There
is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image
at RA(J2000) = 00:21:08.16 (5.2840) DEC(J2000) = +20:58:17.8
(20.9716) with a 1-sigma error radius of about 0.5 arc sec. This
position is 7.0 arc sec. from the center of the BAT error circle. The
estimated magnitude is 16.1 with a 1-sigma error of about 0.5 mag. The
afterglow fades to about 18th magnitude in the subsequent white
finding chart. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.05. 

We note that there is a 2MASS galaxy in the Hyperleda catalog
at  00:21:08.6 20:58:08 (PGC # 1639821), 11.5 arc sec from the UVOT 
position.  The diameter of the galaxy is 0.36 arcmin.