GRB 070509

E.S. Rykoff (U Mich), W. Rujopakarn (Steward), B. E. Schaefer (Louisiana 
State), report on behalf of the ROTSE collaboration:

ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, 
responded to GRB 070509 (Swift trigger 278903), producing images 
beginning 7.4 s after the GCN notice time. An automated response took 
the first image at 02:56:22.4 UT, 475.1 s after the burst, under fair 
conditions. We took 10 5-sec, 10 20-sec and continuing 60-sec exposures. 
These unfiltered images are calibrated relative to USNO A2.0 (R).

Comparison to the DSS (second epoch) reveals no new sources within the 
3-sigma BAT error circle or the XRT error circle, for both single images 
and coadding into sets of 10. Individual images have limiting magnitudes 
ranging from 15.2-16.2; we set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
02:56:22.4   02:56:27.4         5     15.3          475.1       N
02:56:22.4   02:57:39.6        77     16.6          475.1       Y
02:57:53.8   03:02:39.5       285     17.2          566.5       Y

L. Vetere (PSU), S. D. Barthelmy (GSFC), M. M. Chester (PSU),
D. Grupe (PSU), S. T. Holland (CRESST/GSFC/USRA), J. A. Kennea (PSU),
C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC),
C. Pagani (PSU), D. M. Palmer (LANL), J. L. Racusin (PSU),
M. Stamatikos (NASA/ORAU) and D. E. Vanden Berk (PSU) report on
behalf of the Swift Team:

At 02:48:27 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 070509 (trigger=278903).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 237.927, -78.681 which is 
   RA(J2000)  =  15h 51m 42s
   Dec(J2000) = -78d 40' 49"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single FRED-like peak
with a duration of about 10 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began taking data at 02:49:35 UT, 68 seconds after the BAT
trigger. XRT found a faint, uncatalogued X-ray source. The ground 
calculated location is  RA, Dec 237.9592, -78.6511 which is   
   RA(J2000) = 15h 51m 50.2s   
   Dec(J2000) = -78d 39'04.0" 
with an uncertainty of 4.6 arcsec (radius, 90% containment,
including  systematic uncertainty). This location is 1.8 arcmin from
the BAT on-board position, within the BAT error circle. 

UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 72 seconds after the BAT trigger, and a
finding chart exposure of 400 seconds in V starting 177 seconds after
the BAT trigger. No afterglow candidate has been found in the initial
data products. The 2.7'x2.7' sub-image covers none of the XRT error
circle; 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 0.14.

S. Piranomonte, S. Covino, L.A. Antonelli, A. Burzi, L. Calzoletti,   
S. Campana, G.  Chincarini, M.L. Conciatore, S. Cutini, P.  
D'Avanzo,   V. D'Elia, F. Dalessio, F.  Fiore, D. Fugazza, P.  
Goldoni, D. Guetta,  C. Guidorzi, G.L. Israel,  D. Malesani, N.  
Masetti, A. Melandri, E. Meurs, L. Nicastro, E. Palazzi, E. Pian, D.  
Rizzuto,  L.  Stella, G.  Stratta, G. Tagliaferri, G. Tosti, V.  
Testa, S.D. Vergani,  F. Vitali   report on behalf of the REM team:

We observed the field of the GRB 070509 (Vetere et al., GCN 6394
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 )  
with the robotic 60-cm REM telescope located at La Silla (Chile). A  
set of observations was performed automatically in the optical and  
near infrared filters (V, R, I and J, H, K, z) starting at 02:56:52  
UT (33 sec after the Swift alert; more than 8 minutes after the burst).

Preliminary analysis does not show any source down to the 2MASS limit  
in the XRT error circle (Vetere et al., GCN 6394
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 ).

Further analyses are in progress.

This message may be cited.

J. Cummings (GSFC/UMBC), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), L. Vetere (PSU)
on behalf of the Swift-BAT team:
 
Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 070509 (trigger #278903)
(Vetere, et al., GCN Circ. PSU).  The BAT ground-calculated position is
RA, Dec = 237.874, -78.657 deg, which is 
   RA(J2000)  =  15h 51m 29.8s 
   Dec(J2000) = -78d 39' 24.0" 
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 92%.
 
The mask-weighted lightcurve shows a single FRED-like pulse starting at
T-2 sec, peaking at T_0, and ending at ~T+10 sec.  T90 (15-350 keV) is
7.7 +- 0.3 sec (estimated error including systematics).
 
The time-averaged spectrum from T-1.1 to T+7.9 is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.33 +- 0.25.  The fluence in the 15-150 keV band is 1.7 +- 0.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.31 sec in the 15-150 keV band
is 0.7 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

We note that the initial TDRSS messages for this burst were delayed ~6 min
in transmission to the ground because the burst occurred during a Malindi
downlink session.

L. Vetere, J. L. Racusin, D. Grupe, C. Pagani (PSU) and M. Perri (ASDC) report
on behalf of the Swift Team:

We have analysed the first 6.2ks of Swift XRT data from GRB
070509 (trigger number 278903, GCN 6394
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 ).
The first orbit  Photon Counting mode image (1.5ks) provides a
refined XRT position at
RA,DEC(J200) = 237.9588, -78.6508 which is

RA(J2000)  = 15h 51m 50.1s
Dec(J2000) = -78d 39' 03.1"

with an uncertainty of 4.1 arcsec (radius, 90% containment).
This is  0.9 arcsec from the initial X-ray position (GCN 6394
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 )
and 1.0 arcmin from BAT refined position (Cummings et al. GCN 6397
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 ).

The XRT light curve can be modeled with a broken power law with the
following parameters:
alpha1= -0.3 +/- 0.2
tbreak=  341 +/- 120
alpha2= -1.1 +/- 0.2

The X-ray spectrum of the first orbit PC data can be fitted with an
absorbed power law (photon index = 0.8+/-0.2) with an absorbed column
density fixed to the Galactic value (0.91e21 cm^-2; Dickey & Lockman,
1990). The absorbed (unabsorbed) 0.3-10.0keV flux for this spectrum
was 8.8E-12 (9.1E-12) ergs cm^-2 s^-1.

Assuming the source continues to decay at the same rate, we predict
an XRT count rate of 3.5E-4 counts/s at T+24 hours, which corresponds
to an observed (unabsorbed) flux of 5.1E-14 (5.3E-14) ergs cm^-2 s^-1.

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

S. T. Holland (CRESST/GSFC/USRA) and L. Vetere (PSU)
report on the behalf of the Swift UVOT team:


       The Swift/UVOT observed the field of GRB 070509 starting 73 s
after the BAT trigger (Vetere et al. 2007, GCN Circ. 6394
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 ).  We do
not find any source, in any of the UVOT observations, inside the
refined XRT error circle (Vetere et al., 2007 GCN Circ. 6400
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 ).

       The 3-sigma upper limits for detecting a source anywhere inside
the refined XRT error circle in the co-added frames are:


Filter    T_start   T_stop    Exp(s)    Mag (3-sigma upper limit)
-----------------------------------------------------------------
V             179     6074      1003    20.6
B             657     1468        39    18.6
U             633     1443        58    18.4
UVW1          609     1419        58    18.0
UVM2          584     6085        65    17.5
UVW2          686     5869       236    19.3
White          73     1482       225    21.1
-----------------------------------------------------------------

The values quoted above are not corrected for the expected Galactic
extinction corresponding to a reddening of E_{B-V} = 0.14 mag towards
the direction of the burst (Schlegel et al. 1998).

D. Malesani, C.C. Thoene (DARK), A. Williams (Perth Obs.), J.P.U. Fynbo
(DARK), A.O. Jaunsen (Univ. Oslo) and P.M. Vreeswijk (ESO) report on
behalf of a larger collaboration:

We observed the field of GRB 070509 (Vetere et al., GCN 6394
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 ) with the ESO
VLT UT2 equipped with the FORS1 instrument. Short BVRI observations were
carried out between 2007 May 9.144 and 9.155 UT (starting 0.65 hr after
the GRB). We detect three objects close to the XRT position, at the
following coordinates (J2000, 0.5" error):

A:  RA = 15:51:49.29   Dec = -78:39:01.7   R = 23.48 +- 0.24
B:  RA = 15:51:50.37   Dec = -78:39:06.4   R = 23.52 +- 0.25
C:  RA = 15:51:50.91   Dec = -78:39:10.2   R = 22.71 +- 0.16

Objects A and B are inside the XRT error circle as reported by Vetere et
al. (GCN 6400
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 ), while objects B and C are inside the XRT error circle as
provided in Nat Butler's web page (revision 1.2,
http://astro.berkeley.edu/~nat/swift/xrt_pos.html). Objects A and C are
extended. Magnitudes are computed at the mean time 9.149 UT (0.78 hr after
the GRB) and are calibrated against the USNO-B1 catalog. The 3-sigma limit
is R = 23.8. A finding chart of the field can be seen here:

http://www.astro.ku.dk/~malesani/GRB/070509/finder_VLT.jpg

Further R-band observations were carried out with the 1.54m Danish
telescope located in La Silla (Chile) and equipped with DFOSC on 2007 May
9.141 (4500 s) and May 13.134 UT (3000 s). Object C is marginally detected
in both images, while objects A and B are below the detection limit.

At this stage, we cannot claim association between the GRB and any of the
above mentioned objects.

We acknowledge excellent support from the observing staff in Paranal, in
particular Alain Smette and Gael James. CT acknowledges Pisco and Bacardi
support from the GROND staff at La Silla.