GRB 090929B

C. Pagani (PSU), A. P. Beardmore (U Leicester), S. Campana (INAF-OAB),
V. D'Elia (ASDC), C. Gronwall (PSU), D. Grupe (PSU),
C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC),
N. P. M. Kuin (MSSL), J. Mao (INAF-OAB), P. T. O'Brien (U Leicester),
J. P. Osborne (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL), P. Romano (INAF-IASFPA),
B. Sbarufatti (INAF-IASFPA), T. N. Ukwatta (GSFC/GWU) and
L. Vetere (PSU) report on behalf of the Swift Team:

At 10:09:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090929B (trigger=371050).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 117.705, -0.632 which is 
   RA(J2000) = 07h 50m 49s
   Dec(J2000) = -00d 37' 55"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex structure
with most activity in multiple peaks from T-10 sec to T+50 s, and additional
peaks at T+150 sec, during the XRT observations.  The peak count rate
was ~7000 counts/sec (15-350 keV), at ~40 sec after the trigger. 

The XRT began observing the field at 10:10:31.3 UT, 84.1 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 117.7202, -0.6574 which is equivalent to:
   RA(J2000)  = 07h 50m 52.84s
   Dec(J2000) = -00d 39' 26.6"
with an uncertainty of 5.3 arcseconds (radius, 90% containment). This
location is 106 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 1.49e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of  97 seconds with the White
filter  starting 93 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 expected extinction corresponding to
E(B-V) of  0.07.  We note there is a bright (10th mag) star less than
2 arcsec from the XRT position which complicates the analysis of the
UVOT data. 

Burst Advocate for this burst is C. Pagani (pagani AT astro.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.)

K.L. Page (U. Leicester) reports on behalf of the Swift-XRT team:

GCN Circ. 9964
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  referred to GRB 090929 when, in fact, the position given 
is for GRB 090929B (GCN Circ. 9963
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 ). The correct text should read

Using 2438 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 090929B, 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 = 117.72015, -0.65764 which is 
equivalent
to:

RA (J2000): 07h 50m 52.84s
Dec (J2000): -00d 39' 27.5"

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).

We apologise for any confusion.

J. Wren, W.T. Vestrand, P.R. Wozniak, H. Davis, B. Norman
of Los Alamos National Laboratory report:

The RAPTOR telescope system responded to Swift trigger
371050 (Pagani et al., GCN 9963
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 ) under good observing conditions.
Our narrow-field instruments began observing the location at
10:20:53.37 UTC, 11.77 minutes after the initial BAT trigger.
Our initial images show an R~16.8 optical counterpart at the enhanced
XRT location (Page et al., GCN 9965
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 ).  The object fades steadily
reaching R~18.0 at 10:50 UTC.  Our unfiltered images were calibrated
against the USNO-B1 R-band. Unfortunately, an 11th magnitude star is
only 19 arcseconds away, limiting our photometric accuracy.  Further
analysis is ongoing.

P.A. Curran (MSSL-UCL), F. Marshall (GSFC), S. Holland (GSFC) and C.
Pagani (PSU) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 090929B 94s 
after the BAT trigger (Pagani et al., GCN Circ. 9963
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 ). No optical 
afterglow is detected in the b, u or uvw2 UVOT exposures. There is a 
detection in the white filter, consistent with the enhanced XRT position 
(Goad et al. GCN 9964
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 , Page et al. GCN 9965
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 ), the proposed optical 
counterpart (Wren et al. GCN 9967
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 ) and a USNO catalogued star (R2=19.3). 
Since the photometry is contaminated by a bright (R = 9.5), near-by star, 
we cannot determine the nature of the source at this time.


Preliminary magnitudes and 3-sigma upper limits using the UVOT photometric 
system (Poole et al. 2008, MNRAS, 383, 627) for the initial exposures are:

Filter       T_start(s)   T_stop(s)     Exp(s)      Mag
----------------------------------------------------------------
white        94           4032          292         18.7 +/- 0.5
b            3627         3827          197         >20.5
u            3422         3622          197         >20.3
uvw2         4038         4224          183         >20.3

The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.07 in the direction of the burst
(Schlegel et al. 1998).

J. Haislip, D. Reichart, A. Smith, D. Caton, L. Hawkins, K. Ivarsen, M. 
Schubel, A. LaCluyze, A. Foster, J. Moore, A. Oza, M. Schubel, J. Styblova, 
A. Trotter, J. A. Crain, and M. Nysewander report:

Skynet observed the Swift/BAT localization of GRB 090929B (Pagani et al., 
GCN 9963
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 ) with the 14" Dark Sky Observatory telescope in North Carolina 
beginning 12.0 minutes after the trigger in I.

We do not detect the afterglow (Pagani et al., GCN 9963
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 , Wren et al., GCN 
9967
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 ) within the enhanced Swift/XRT localization (Goad et al., 9964; Page, 
GCN 9965
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 ).  However, the nearby I = 9.07 mag (USNO B1) star complicates 
photometry.

mean                                                     1-sig.   1-sig.
time                              3-sig.                 sys.     stat.
since                             lim.     cal.          cal.     cal.
trig.   tel.     exp.      fil.   mag.     stars         unc.     unc.
(h)              (# x s)                                 (mag)    (mag)

12.0    DSO-14   1 x 80    I      17.1     183 USNO B1   0.400    0.001

A. Cucchiara, D. B. Fox (PSU), N. Tanvir (U. Leicester),
E. Berger (Harvard U.) and A. Levan (U. Warwick) report:

On September 29.58 UT we observed the field of GRB 090929B
(Pagani et al. GCN 9963
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 ) with Gemini-North + NIRI.
We took a sequence of YJHK bands images under twilight conditions.

No clear afterglow candidate has been found in the XRT refined error
circle (GCN 9964
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  and 9965
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 ) to the following limits (3-sigma):

J > 21.10 mag
H > 19.53 mag
K > 18.06 mag

Our limits are estimated using detected 2MASS objects at comparable
distance to the bright star (R = 9.5) which is located near the XRT
error circle.
We note the presence of a USNO catalogued star inside the refined
error circle; the above limits are exclusive of that star.

We thank the Gemini staff for performing these observations, in
particular Ricardo Schiavon.

C. Pagani and L. Vetere (PSU) report on behalf of the Swift-XRT team:

We have analysed 3.7 ks of XRT data for GRB 090929B (Pagani et al. GCN Circ.
9963
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 ), from 90 s to 16.3 ks after the BAT trigger. The first orbit of data was
entirely taken in Windowed Timing (WT) mode for a total of 100 s.  The
remaining orbits are in Photon Counting (PC) mode. The enhanced XRT position
for this burst was given by Page (GCN. Circ 9965).

The light curve shows intense flaring activity during the first orbit with the
strongest emission at approximately 180 counts s^-1 at T+150 s, during a peak
also detected by the BAT (GCN Circ. 9963
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 ).  The following orbits can be modeled
with a broken power-law decay with an shallow phase of index of alpha=0.5 (+1.0,
-0.6) followed by a steeper decay of index alpha=1.2+/-0.3 after ~T+5.6 ks.

A spectrum formed from the WT mode data can be fitted with an absorbed power-law
with a photon spectral index of 1.68 (+/-0.05). The best-fitting absorption
column is 2.2 (+/-0.1) x 10^21 cm^-2, in excess of the Galactic value of 5.4 x
10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of
2.01 (+0.18, -0.17) and a best-fitting absorption column of 1.6 (+0.5, -0.4) x
10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 4.1 x 10^-11 (5.7 x 10^-11) erg cm^-2
count^-1.

If the light curve continues to decay with a power-law decay index of 1.2, the
count rate at T+24 hours will be 0.015 count s^-1, corresponding to an observed
(unabsorbed) 0.3-10 keV flux of 6.1 x 10^-12 (8.6 x 10^-12) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00371050.

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

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 090929B (Swift-BAT trigger #371050: Pagani et al., GCN 
9963
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 ) triggered Konus-Wind at T0=36565.377 s UT (10:09:25.377).

The burst light curve shows a multipeaked structure with a total
duration of ~20 s.

As observed by Konus-Wind the burst
had a fluence of (1.16 +/- 0.12)x10^-5 erg/cm2,
and a 256-ms peak flux measured from T0+16.208 s
of (3.80 +/- 0.90)x10^-6 erg/cm2/s
(both in the 20 keV - 1 MeV energy range).

The time-integrated spectrum of the burst
(from T0 to T0+16.640 s) is well fitted (in the 20 keV - 1 MeV
range) by GRB (Band) model for which:
the low-energy photon index alpha = -0.41 (-0.77, +1.16),
the high energy photon index beta = -1.82(-0.59, +0.24),
the peak energy Ep = 282(-78, +169) keV (chi2 = 52.4/59 dof).

All the quoted errors are at the 90% confidence level.

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.ru/LEA/GRBs/GRB090929_T36565/

H. A. Krimm (GSFC/USRA),
S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC),
E. E. Fenimore (LANL),
N. Gehrels (GSFC),
C. B. Markwardt (GSFC/UMD),
C. Pagani (PSU),
D. M. Palmer (LANL),
A. M. Parsons (GSFC),
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-239 to T+691 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 090929 (trigger
#371050) (Pagani, et al., GCN Circ. 9963
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 ).  The BAT ground-calculated
position is RA, Dec = 117.712, -0.645 deg which is
    RA(J2000)  =  07h 50m 50.9s
    Dec(J2000) = -00d 38' 41.2"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 63%.

The mask-weighted lightcurve shows many peaks interspersed with
intervals with no detected flux, from T-10 to T+380 sec when the source
left the coded field of view due to a observing constraint. There may
have been small and/or low-energy peaks beyond this time.  The largest
peak was at about T+30 to T+40 sec. T90 (15-350 keV) was 360 +- 20 sec
(estimated error including systematics).

The time-averaged spectrum from T-9.8 to T+371.0 sec is best fit by a
simple power-law model.  The power law index of the time-averaged
spectrum is 1.85 +- 0.08.  The fluence in the 15-150 keV band is
5.9 +- 0.3 x 10^-06 erg/cm2.  The 1-sec peak photon flux measured from
T+30.67 sec in the 15-150 keV band is 3.3 +- 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/371050/BA/

N. Ohmori, E. Sonoda, K. Kono, H. Hayashi, A. Daikyuji, 
Y. Nishioka, K. Noda, M. Yamauchi (Univ. of Miyazaki),
K. Yamaoka (Aoyama Gakuin U.), Y. Hanabata, T. Uehara, 
T. Takahashi, Y. Fukazawa (Hiroshima U.), M. Ohno, M. Suzuki, 
M. Kokubun, T. Takahashi (ISAS/JAXA), W. Iwakiri, M. Tashiro, 
Y. Terada, A. Endo, K. Onda, T. Sugasahara (Saitama U.), 
Y. Urata (NCU), T. Enoto, K. Nakazawa, K. Makishima (Univ. of Tokyo), 
Y. E. Nakagawa, T. Tamagawa (RIKEN), S. Hong (Nihon U.), 
S. Sugita (Nagoya U.), N. Vasquez (Tokyo Tech.),
on behalf of the Suzaku WAM team, report:

The long GRB 090929B (Swift-BAT trigger #371050; Pagani et al., GCN 9963
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 , 
 Krimm et al. GCN 9979
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 ) was detected by the Suzaku Wide-band All-sky 
Monitor (WAM) which covers an energy range of 50 keV - 5 MeV at 
10:09:23.633 UT (=T0).

The observed light curve shows a multi-peaked structure, starting at
T0-2 s and ending at T0+20 s, with a total duration (T90) of about 18 s.
The fluence in 100 - 1000 keV was (3.92 $B!^(B 0.63) x 10-6 erg/cm2.
The 1-s peak flux measured from T0+1 s was 1.42 (-0.25. +0.24)
photons/cm2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from
T0-2 s to T0+20 s is well fitted by a single power-law with 
 a photon index of 1.96 (-0.17, +0.20) (chi2/d.o.f = 23.4/27).
 
All the quoted errors are at statistical 90% confidence level,
in which the systematic uncertainties are not included.

The light curves for this burst will be available at:
http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/untrig/grb_table.html