GRB 080315

K. L. Page (U Leicester), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), D. N. Burrows (PSU),
M. M. Chester (PSU), N. Gehrels (NASA/GSFC),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (CRESST/GSFC/UMD),
F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL),
M. Stamatikos (NASA/ORAU), E. Troja (U Leicester/INAF-IASFPA) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 02:25:01 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 080315 (trigger=306323).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 155.182, +41.729 which is 
   RA(J2000) = 10h 20m 44s
   Dec(J2000) = +41d 43' 44"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual for a 64-second image trigger,
the TDRSS light curve shows no obvious variation.  Further BAT analysis
will rely on the Malindi-downlinked data. 

The XRT began observing the field at 02:27:07.3 UT, 125.9 seconds after
the BAT trigger. No source was detected in the promptly available XRT
data. We are waiting for the full dataset to detect and localise the
XRT counterpart. 


UVOT took a finding chart exposure of 400 seconds with the V filter starting
125 seconds after the BAT trigger. No afterglow candidate has been found in the
initial data products. The 2.7'x2.7' sub-image covers 25% of the BAT error
circle. The typical 3-sigma upper limit has been about 18.5 mag. The 8'x8'
region for the list of sources generated on-board covers 100% of the BAT error
circle. The list of sources is typically complete to about 18.0 mag. No
correction has been made for the expected extinction of about 0.04 magnitudes. 




Burst Advocate for this burst is K. L. Page (kpa AT star.le.ac.uk). 
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.)

Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report:

We imaged the field of GRB 080315 detected by SWIFT
(trigger 306323) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 85.0s after the GRB trigger
(9.4s after the notice). The elevation of the field decreased from
from 45 degrees above horizon and weather conditions
were excellents.

The date of trigger : t0 = 2008-03-15T02:25:01.3

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect any OT with a limiting magnitude of:
t0+85.0s to t0+145.0s : R > 16.8

The second image is 30.0s exposure in tracking mode:
t0+152.1s to t0+182.1s : R > 18.3

We co-added a series of exposures:
t0+152.1s to t0+436.0s : R > 19.7

These images are unfiltered.

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

N.B. Galactic coordinates are lon=177.6257 lat=+56.0163
and the galactic extinction in R band less than 0.1 magnitude
estimated from D. Schlegel et al. 1998ApJ...500..525S.

This message may be cited.

A. de Ugarte Postigo (ESO, Chile), Virginie Chantry (U. Liege, Belgium),
A.J. Castro-Tirado, M. Jelinek, J. Gorosabel (IAA-CSIC, Spain),
C. Melo, A. Smette (ESO, Chile) report:

We have observed the field of GRB 080315 (Page et al., GCN 7416
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 ) with the
1.3m Mercator telescope at La Palma starting at 02:55 UT (30 min after
the burst).
The observation consisted on a series of 24x60s I-band exposures. The
combined
exposure, with mean time 3:26 UT (61.3 minutes after the burst), does not
show
any new source inside the 3 arcmin BAT error box down to a limiting
magnitude
of I~20.8 (USNO-B1.0 was used as photometric reference) as compared to
SDSS
i-band frame.

This message may be cited.

P. Schady (MSSL/UCL) and K. L. Page (U Leicester) report on behalf of the 
Swift UVOT team:

The Swift/UVOT observed the field of GRB 080315 starting 125 s after the 
BAT trigger (Page et al., GCN 7416
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 ). We do not find any source in any of 
the individual or co-added exposures, either within the BAT error circle 
or at the location of the weak source detected by XRT (Barthelmy et al. 
GCN 7420
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 ).

The 5-sigma upper limits for detecting a source at the position of the XRT 
candidate in the co-added images are:

Filter  T_start T_stop Exp      Mag
         (s)     (s)    (s)      (5-sigma upper limit)
-----------------------------------------------------
v       127     42160   6078.4  > 20.79
b       608     40422   5815.6  > 21.84
u       582     7467    620.7   > 20.30
uvw1    558     7281    468.7   > 19.82
uvm2    533     7075    858.7   > 20.00
uvw2    113     41328   5847.3  > 21.63
-----------------------------------------------------

The quoted upper limits have not been corrected for the expected Galactic 
extinction along the line of sight corresponding to a reddening of E(B-V) 
= 0.01 mag. All photometry is on the UVOT light flight system described in 
Poole et al. (2008, MNRAS, 383, 627).

P.A.Milne (Steward Obs) and A. Updike report on behalf of the
Super-LOTIS GRB team:
 
We observed the field of GRB 080315 starting at UT=02:43:58
(~19min since GRB) with the 2.3m Bok telescope at Kitt Peak, AZ.
We obtained 23 x 60-sec and 7 x 120-sec images in the R-band filter.
 
We do not detect emission at the location of the faint XRT source
(Palmer et al., GCN 7416
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 ) to a limiting magnitude of R~23.5.
 
We do not detect any sources other than ones apparent in the DSS,
to the limit of the DSS image. We do not detect a fading/rising source
between the initial 10 and final 10 images.
 
This message may be cited.

K.L. Page (U. Leicester) and N. Gehrels (NASA/GSFC) report on behalf of 
the Swift-XRT team:

Swift-XRT performed follow-up observations of the possible GRB 080315 (BAT 
trigger number 306323) about a month after the trigger, in order to 
determine whether or not the possible X-ray afterglow mentioned in GCN 
Circ. 7420
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  had faded. We find that this source is at a count rate 
consistent with that of our original observation, so conclude that it is 
not the afterglow. Thus, no afterglow was detected for this trigger.

Excluding this constant X-ray source, the 3-sigma upper limit within the 
BAT error circle from the observation directly following the trigger (25 
ks on 2008-03-15) was 5.9 x 10^-4 count s^-1; the late-time data (30 ks 
between 2008-04-16 and 2008-04-21) provide a limit of 5.2 x 10^-4 count 
s^-1. 

We cannot rule out that this was a real burst, but given the lack of XRT 
detection and marginal BAT detection it is not likely.