GRB 120909A

S. Immler (CRESST/GSFC/UMD), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
S. T. Holland (STScI), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL) and M. H. Siegel (PSU)
report on behalf of the Swift Team:

At 01:42:03 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 120909A (trigger=533060).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 275.685, -59.426 which is 
   RA(J2000)  =  18h 22m 44s
   Dec(J2000) = -59d 25' 34"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows one, possibly two, peaks
with a duration of about 5 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 01:43:36.6 UT, 93.4 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 275.7388, -59.4485 which is equivalent to:
   RA(J2000)  = +18h 22m 57.31s
   Dec(J2000) = -59d 26' 54.6"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 127 arcseconds from the BAT onboard position, within the
BAT error circle. No event data are yet available to determine the
column density using X-ray spectroscopy. 

The initial flux in the 2.5 s image was 7.55e-09 erg cm^-2 s^-1 (0.2-10
keV). 

Because of an earth limb constraint, Swift slewed away before UVOT 
could take its initial exposures.  Subsequent orbits will include 
UVOT observations. 

Burst Advocate for this burst is S. Immler (stefan.immler AT nasa.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/too.html.)

J. Haislip, A. LaCluyze, K. Ivarsen, D. Reichart, J. Moore, H. T. 
Cromartie, R. Egger, A. Foster, N. Frank, M. Nysewander, A. Oza, E. 
Speckhard, A.Trotter, and J. A. Crain report:

Skynet observed the field of GRB120909A (GCN 13727
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 , Swift trigger #533060) 
with the PROMPT telescopes located at CTIO in Chile beginning ~4 minutes 
after the burst. We detect a fading, uncataloged source at RA 18:22:56.72 
DEC -59:26:54.0, roughly coinciding with the location of the Swift trigger 
with an initial magnitude of ~16.3 in R, calibrated to the NOMAD catalog.

Further observations are ongoing.

V. Sudilovsky (MPE Garching), S. Schmidl (TLS Tautenburg), D.A. Kann (MPE
Garching) and J. Greiner (MPE Garching) report on behalf of the GROND
team:

We observed the field of GRB 120909A (Swift trigger 533060; Immler et al.,
GCN #13727
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 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla
Observatory (Chile).

Observations started at 01:44 UT, September 09, 140s after the burst, and
are continuing. They were performed at an average seeing of 1".6 and at an
average airmass of 1.2 .

We found a single point source within the 4".8 Swift-XRT error circle
reported by Immler et al. (GCN #13727
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 ) at

RA (J2000.0) = 18h 22m 56.72s

DEC (J2000.0) = -59d 26' 54".1

with an uncertainty of 0".5 in each coordinate, which is consistent with
the position reported by Haislip et al. (GCN #13728
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 )   .

Based on the first 141s of total exposures in g'r'i'z' and 240s in JHK,
we estimate preliminary magnitudes (all in AB) of

g' = 18.4 +- 0.1,
r' = 16.6 +- 0.1,
i' = 15.8 +- 0.1,
z' = 15.5 +- 0.1,
J = 14.8 +- 0.1,
H = 14.5 +- 0.1, and
K = 14.3 +- 0.1.

Based on the the significantly lower flux in g', this suggests a 
redshift z>3.

Given magnitudes are calibrated against GROND zeropoints as well as 2MASS
field stars and are not corrected for the expected Galactic foreground
extinction corresponding to a reddening of E_(B-V)=0.08 mag in the
direction of the burst (Schlegel et al. 1998).

O. E. Hartoog (Uva, NL), D. Malesani (DARK/NBI), K. Wiersema (U. Leicester,
UK), T. Kruehler (DARK/NBI),  S. Schulze (PUC and MCSS), A. de Ugarte
Postigo (IAA/CSIC and DARK/NBI), V. D'Elia (INAF/Roma and ASI/ASDC), J. P.
U. Fynbo (DARK/NBI), report on behalf of the X-shooter GRB GTO
collaboration:

We observed the optical counterpart of GRB 120909A (Immler et al., GCN
13727
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 ; Haislip et al., GCN 13728
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 ; Sudilovsky et al., GCN 13729
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 ) with the
ESO VLT equipped with the X-shooter spectrograph. Observations were carried
out starting on 2012 Sep 9.14 UT (1.7 hr after the GRB), for a total
exposure time of 20 min, covering the wavelength range 3000-25000 AA.

We detect several absorption features, including Ly-a, FeII, NiII, SiII,
SII, AlII, AlIII, CII, OI, CIV, ZnII all at a common redshift z = 3.93. In
particular, the presence of fine-structure lines (Fe II*, SiII*, OI*, OI**,
CII*) makes the redshift securely associated to the GRB.

We acknowledge support from the VLT staff, in particular Giovanni Carraro
and Giacomo Beccari.

J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 1720 s of XRT Photon Counting mode data and 5 UVOT
images for GRB 120909A, 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 = 275.73656, -59.44863 which is equivalent
to:

RA (J2000): 18h 22m 56.78s
Dec (J2000): -59d 26' 55.1"

with an uncertainty of 1.4 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.

T. N. Ukwatta (MSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
S. Immler (CRESST/GSFC/UMD), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (OSU), J. Tueller (GSFC)
(i.e. the Swift-BAT team):
 
Using the data set from T-41 to T+556 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 120909A (trigger #533060)
(Immler, et al., GCN Circ. 13727
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 ).  The BAT ground-calculated position is
RA, Dec = 275.735, -59.432 deg which is 
   RA(J2000)  =  18h 22m 56.5s 
   Dec(J2000) = -59d 25' 55.2" 
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 48%.
 
The mask-weighted light curve shows multiple overlapping peaks. The burst was
already occurring when Swift-BAT came out of the SAA at ~T-40 sec.
The observed peaks occurred at ~T-38, ~T+1, ~T+28, and ~T+48 sec.
The burst returned to baseline at ~T+200 sec.  There is a possible peak
at ~T+490 to ~T+580 sec, at which point Swift had to slew due to an observing
constraint and the location went out of the BAT FoV.
 
The time-averaged spectrum from T-38.98 to T+95.17 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.39 +- 0.06.  The fluence in the 15-150 keV band is 6.8 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.88 sec in the 15-150 keV band
is 1.8 +- 0.3 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/533060/BA/

V. Mangano (INAF-IASFPA), A. Melandri (INAF-OAB), M.C. Stroh (PSU),
D.N. Burrows (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), C.
Pagani (U. Leicester), A.P. Beardmore (U. Leicester), B. Sbarufatti
(INAF-OAB/PSU) and S. Immler report on behalf of the Swift-XRT team:

We have analysed 9.3 ks of XRT data for GRB 120909A (Immler  et al. GCN
Circ. 13727
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 ), from 3.3 ks to 33.3 ks after the	BAT trigger. The data
comprise 173 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Osborne et al. (GCN. Circ 13732).

The light curve can be modelled with  a power-law decay with a decay
index of alpha=1.19 (+/-0.06).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.04 (+/-0.09). The
best-fitting absorption column is  1.9 (+0.8, -0.7) x 10^22 cm^-2, at a
redshift of 3.93, in addition to the Galactic value of 6.5 x 10^20
cm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed)
0.3-10 keV flux conversion factor deduced from this spectrum  is 3.5 x
10^-11 (4.7 x 10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Galactic foreground: 6.5 x 10^20 cm^-2
Intrinsic column:    1.9 (+0.8, -0.7) x 10^22 cm^-2 at z=3.93
Photon index:	     2.04 (+/-0.09)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00533060.

This circular is an official product of the Swift-XRT team.

A. A. Breeveld (MSSL-UCL) and S. Immler (CRESST/GSFC/UMD) report on 
behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 120909A
3308 s after the BAT trigger (Immler et al., GCN Circ. 13727
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 ).
A source consistent with the optical position (Sudilovsky et al. GCN 
Circ. 13729
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 ), is detected in the initial UVOT exposures.

Preliminary detections and 3-sigma upper limits using the UVOT 
photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for 
the early exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white             3308         4690          344         20.75 � 0.20
v                 3465        16690         1261        >20.2
b                 4285        23216          937        >21.5
u                 4080        22450         1848        >21.4
w1                3875        21536         1968        >21.6
m2                3670        17445         1820        >21.4
w2                4696        15776         1082        >21.6

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.09 in the direction of the 
burst (Schlegel et al. 1998).

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

The long GRB 120909A (Swift-BAT trigger #533060:
Immler et al., GCN 13727
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 ; Ukwatta et al., GCN 13733
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 )
was detected by Konus-Wind in the waiting mode
starting at 6069 s UT (01:41:09), ~54s before the T0(BAT).

The burst light curve shows a multi-peaked structure
with a total duration of ~115s.

The K-W light curve of this burst is available at
http://www.ioffe.rssi.ru/LEA/GRBs/GRB120909A/

As observed by Konus-Wind, the burst had a fluence
of (2.3 � 0.2)x10-5 erg/cm2 and a peak energy flux,
measured on the 2.944-s scale, of (6.1 � 0.8)x10-7 erg/cm2
(both in the 20 - 1500 keV energy range).

Modelling the K-W 3-channel time-integrated spectrum
(from T0(BAT)-54s to T0(BAT)+61 s)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -1.23 � 0.04, and Ep = 335 � 25 keV

Assuming X-Shooter redshift of z=3.93 (Hartoog et al., GCN 13730
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 )
and a standard cosmology model with H_0 = 71 km/s/Mpc, Omega_M = 0.27, 
Omega_Lambda = 0.73:
the isotropic energy release E_iso is (6.9 � 0.5)x10^53 erg,
the isotropic peak luminosity L_iso_max is (9.0 � 1.2)x10^52 erg/s,
and Ep_rest is (1650 � 120) keV.

All the quoted errors are estimated at the 1 sigma confidence level.

V.Chaplin (UAH) reports on behalf of the Fermi GBM Team:

At 01:41:22.40 UT on 09 September 2012, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 120909A (trigger 368847685 / 120909070), 
which was also detected by the Swift/BAT (Immler et al. 2012, GCN 13727
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 )
The GBM on-ground location is consistent with the Swift position.
The angle to the Fermi LAT boresight is 66 degrees.

The GBM light curve consists of several peaks between T0
and T0+100 seconds, with a total duration (T90) of about 
112 s (50-300 keV).

The time-averaged spectrum from T0-2.8 s to T0+104.7 s is
best fit by a power law with exponential cutoff having 
an index of -1.3 +/- 0.1 and cutoff energy 370 +/- 140 keV.
The event fluence (10-1000 keV) in this time interval is
(2.1 +/- 0.2)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+3.26 s in the 10-1000 keV band
is 3.0 +/- 0.2 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog.

T.Batsch,A.Cwiek,A.Majcher,A.Majczyna,K.Nawrocki,M.Sokolowski,G.Wrochna 
(NCBJ, Swierk),
M.Cwiok,L.W.Piotrowski,M.Zaremba,A.F.Zarnecki (University of Warsaw),
K.Malek,L.Mankiewicz,R.Opiela,M.Siudek,V.Repei (CFT PAN),
G.Kasprowicz (Warsaw University of Technology),
from the "Pi of the Sky" collaboration ( http://grb.fuw.edu.pl ).

The wide field "Pi of the Sky South" telescope, installed in
the private observatory of Alain Maury in San Pedro de Atacama 
(http://grb.fuw.edu.pl/pi/index.html#spda_site.htm) observed coordinates 
of the GRB 120909A, starting 10 s exposure 94 s after the reported SWIFT 
BAT detection. No new source was identified. The limiting magnitude is 
11.6, based on the reference star magnitudo in V filter.

We acknowledge support received from Alain Maury at SPdA Observatory.

This message can be cited.

Klotz A. (IRAP-CNRS-OMP), Gendre B. (ASDC/INAF-OAR),
Boer M. (UNS-CNRS-OCA), Atteia J.L. (IRAP-CNRS-OMP) report:

We imaged the field of GRB 120909A detected by SWIFT
(trigger 533060) with the TAROT robotic telescope (D=25cm)
located at the European Southern Observatory,
La Silla observatory, Chile.

The observations started 40s after the GRB trigger
(14s after the notice). The elevation of the field decreased
from 54 degrees above horizon and weather conditions
were good.

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We detect the optical transient discovered by
Haislip et al. (GCNC 13728).

Relative photometric analysis is done using R=14.37
for the star NOMAD1 0305-0869420 (R.A.=275.7585731
Decl=-59.4476147 J2000).

The careful analysis of the trail is compatible with a
constant magnitude of R=17.1 from T+40s to T+100s.
There is not optical peak during the gamma peak
at T+48s reported by Ukwatta et al. (GCNC 13733).

After the trailed image, a technical problem caused the
lost of images until T+439s. Following images have been
acquired using the classical diurnal drift.

Summary of the first observations is:

Start  Stop  Rmag  Error
   40s  100s  17.1    0.1 (continuous photometry)
  439s  529s  16.5    0.1
  539s  629s  18.9    0.1
  640s  729s  19.1    0.2
  744s  834s  19.3    0.2
  845s  935s  19.7    0.2

Magnitudes are not corrected for galactic dust extinction
(which should be about 0.4 magnitude in the R band according
to D. Schlegel et al. 1998ApJ...500..525S).

This message may be cited.