GRB 150202A

H. A. Krimm (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC),
M. M. Chester (PSU), J. A. Kennea (PSU), K. L. Page (U Leicester),
D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/PSU) and
T. N. Ukwatta (LANL) report on behalf of the Swift Team:

At 23:10:02 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150202A (trigger=629547).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 39.236, -33.150, which is 
   RA(J2000)  =  02h 36m 57s
   Dec(J2000) = -33d 08' 59"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve show several peaks
swith a total duration of about 30 sec.  The peak count rate
was ~1600 counts/sec (15-350 keV), at ~4 sec after the trigger. 

The XRT began observing the field at 23:11:30.3 UT, 88.0 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 39.2275,
-33.1485 which is equivalent to:
   RA(J2000)  = 02h 36m 54.61s
   Dec(J2000) = -33d 08' 54.5"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 26 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (2.54 x
10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.3
(+1.96/-1.74) x 10^21 cm^-2 (90% confidence). 

  UVOT took a finding chart exposure of 250 seconds with the U filter
starting  304 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 19.2 mag. Data  from the list of sources
generated on-board are not available at this time. No  correction has
been made for the expected extinction corresponding to E(B-V) of 
0.02. 

Burst Advocate for this burst is H. A. Krimm (hans.krimm 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.)

C. Delvaux, K. Varela and J. Greiner (all MPE Garching) report on behalf
of the GROND team:

We observed the field of GRB 150202A (SWIFT-629547; Krimm et al., GCN
#17376
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 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla
Observatory (Chile).

Observations started on February 3rd, 2015, at 00:43 UT, 1.5 hrs after the
GRB trigger. They were performed at an average seeing of 1.1" and at an
average airmass of 1.7.

We do not detect a source inside the 2.1� error circle reported by Krimm
et al. (GCN #17376
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 ). Based on a total exposure of 2.07 hours in
g'r'i'z'and 1.73 hours in JHK, at a midtime of 2 hours after the burst, we
measure the following preliminary upper limits (AB magnitudes system):

g' > 24.2 mag,
r' > 24.7 mag,
i' > 24.4 mag,
z' > 24.4 mag,
J  > 22.1 mag,
H  > 21.5 mag, and
K  > 18.0 mag.

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) = 0.02 mag in the
direction of the burst (Schlegel et al. 1998).

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

Using 3966 s of XRT Photon Counting mode data and 6 UVOT
images for GRB 150202A, 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 = 39.22744, -33.14804 which is equivalent
to:

RA (J2000): 02h 36m 54.59s
Dec (J2000): -33d 08' 53.0"

with an uncertainty of 1.7 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.

P.A. Evans (U. Leicester), B.P. Gompertz (U. Leicester), V. D'Elia
(ASDC), M. de Pasquale (INAF-IASFPA), A. Maselli  (INAF-IASFPA), D.N.
Burrows (PSU), J.A. Kennea (PSU), V. Mangano (PSU), J.P. Osborne (U.
Leicester) and H.A. Krimm report on behalf of the Swift-XRT team:

We have analysed 6.0 ks of XRT data for GRB 150202A (Krimm et al. GCN
Circ. 17376
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 ), from 98 s to 24.9 ks after the  BAT trigger. The data are
entirely in Photon Counting (PC) mode. The enhanced XRT position for
this burst was given by Beardmore et al. (GCN Circ. 17382
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 ).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.62 (+0.12, -0.13), followed by a break at T+1352 s to
an alpha of 1.26 (+0.30, -0.11).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.00 (+/-0.17). The
best-fitting absorption column is  1.7 (+0.6, -0.5) x 10^21 cm^-2, in
excess of the Galactic value of 2.5 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 3.5 x 10^-11 (4.6 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.7 (+0.6, -0.5) x 10^21 cm^-2
Galactic foreground: 2.5 x 10^20 cm^-2
Excess significance: 4.6 sigma
Photon index:	     2.00 (+/-0.17)

If the light curve continues to decay with a power-law decay index of
1.26, the count rate at T+24 hours will be 2.5 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.5 x
10^-14 (1.1 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00629547.

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

M. M. Chester (PSU) and H. A. Krimm (CRESST/GSFC/USRA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150202A
93 s after the BAT trigger (Krimm et al., GCN Circ. 17376
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 ).
No optical afterglow consistent with the XRT position (Beardmore et al. 
GCN Circ. 17382
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 ) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

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

white_FC            93          243          147         >20.6
u_FC               305          555          246         >20.2
white               93         6568          624         >21.5
v                  634         6980          530         >20.4
b                  560         7617          350         >21.3
u                  305         7594          756         >20.7
w1                 683         7390          510         >20.9
m2                 658         7185          452         >21.7
w2                 610         6774          490         >20.7

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).

T. Sakamoto (AGU), S. D. Barthelmy (GSFC),  W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):

Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 150202A (trigger #629547)
(Krimm, et al., GCN Circ. 17376
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 ).  The BAT ground-calculated position is
RA, Dec = 39.261, -33.132 deg which is
    RA(J2000)  =  02h 37m 02.6s
    Dec(J2000) = -33d 07' 56.1"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 60%.

The mask-weighted light curve shows a complex structure with multiple peaks. The 
first emission episode runs from T-2 to T+10 sec and then second episode from 
T+12 to ~T+30 sec. T90 (15-350 keV) is 25.7 +- 4.3 sec (estimated error 
including systematics).

The time-averaged spectrum from T-1.7 to T+27.1 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.50 +- 0.19.  The fluence in the 15-150 keV band is 6.1 +- 0.7 x 10^-7 erg/cm2. 
The 1-sec peak photon flux measured from T+17.40 sec in the 15-150 keV band is 
1.0 +- 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/629547/BA/