GRB 150201A

J. K. Cannizzo (NASA/UMBC), A. P. Beardmore (U Leicester),
N. Gehrels (NASA/GSFC), H. A. Krimm (CRESST/GSFC/USRA),
D. Malesani (DARK/NBI), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester) and T. N. Ukwatta (LANL) report on behalf of
the Swift Team:

At 13:46:59 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150201A (trigger=629302).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 11.832, -37.625 which is 
   RA(J2000) = 00h 47m 20s
   Dec(J2000) = -37d 37' 29"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a double-peaked
structure with a duration of about 20 sec.  The peak count rate
was ~21500 counts/sec (15-350 keV), at ~2 sec before the trigger. 

The XRT began observing the field at 13:48:26.8 UT, 87.2 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 11.8325, -37.6193 which is equivalent to:
   RA(J2000)  = +00h 47m 19.80s
   Dec(J2000) = -37d 37' 09.5"
with an uncertainty of 5.0 arcseconds (radius, 90% containment). This
location is 20 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 3.03e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 92 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
0.01. 

Burst Advocate for this burst is J. K. Cannizzo (cannizzo AT milkyway.gsfc.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.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 308 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 150201A, 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 = 11.83271, -37.61883 which is equivalent
to:

RA (J2000): 00h 47m 19.85s
Dec (J2000): -37d 37' 07.8"

with an uncertainty of 1.6 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.

H.-F. Yu (MPE) and V. Pelassa (UAH) report on behalf of the Fermi GBM Team:

"At 13:46:55.15 UT on 01 Feb 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150201A (trigger 444491218 / 150201574),
which was also detected by the Swift (Cannizzo et al. 2015, GCN 17368
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 ).
The GBM on-ground location is consistent with the Swift position.
The trigger resulted in an Autonomous Repoint Request (ARR) that was
accepted and the spacecraft slewed to the GBM in-flight location.
The angle from the Fermi LAT boresight is about 60 degrees.

The GBM light curve shows a double-peaked pulse with a duration (T90)
of about 16 s (50-300 keV). The time-averaged spectrum from T0-2.816 s
to T0+36.097 s is well fit by a Band function with Epeak = 131 +/- 2 keV,
alpha = -1.02 +/- 0.01, and beta = -2.70 +/- 0.06. The event fluence
(10-1000 keV) in this time interval is (6.63 +/- 0.05)E-05 erg/cm^2.
The 1.024-sec peak photon flux measured starting from T0+4.608 s in
the 10-1000 keV band is 88.7 +/- 0.7 ph/s/cm^2.

GBM triggered on GRB 150201590 23 minutes after GRB 150201A,
at 14:09:56 UT (MET 444492598). The GBM localization of this 2nd trigger
is RA, Dec = 2.1, -40.7 with an uncertainty of 2.7 deg (radius, 1-sigma
containment,statistical only; there is additionally a systematic error
which is currently estimated to be 2 to 3 degrees).  This is consistent
with the position of GRB 150201A.

As seen by GBM, this second event shows a multi-peaked pulse with a
duration (T90) of about 26 s (50-300 keV). The time-averaged spectrum
from T0-0.512 s to T0+22.016 s is well fit by a power law function with
an exponential high-energy cutoff. The power law index is -0.61 +/- 0.15
and the cutoff energy, parameterized as Epeak, is 105 +/- 8 keV. The
event fluence (10-1000 keV) in this time interval is
(2.13 +/- 0.11)E-06 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+7.104 s in the 10-1000 keV band is 2.1 +/- 0.2 ph/s/cm^2.

At the time of this 2nd trigger the position of 150201A was occulted by
the Earth to the Swift spacecraft. The GBM data suggest the two events may
have a common origin. Because of the uncertainty in the GBM localization,
we cannot exclude the possibility that this is a chance coincidence and
that GRB 150201590 is unrelated to GRB 150201A.

Owing to the possible relationship between the two triggers, which would make
this an unusually long GRB, Fermi is observing the position of GRB 150201A
as a target of opportunity for a period of 24 hours, subject to Earth limb
constraints.

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

A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), B.P. Gompertz
(U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), M. de
Pasquale (INAF-IASFPA), M.C. Stroh (PSU), D.N. Burrows (PSU), J.A.
Kennea (PSU) and J.K. Cannizzo report on behalf of the Swift-XRT team:

We have analysed 7.9 ks of XRT data for GRB 150201A (Cannizzo et al.
GCN Circ. 17368
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 ), from 75 s to 51.9 ks after the  BAT trigger. The data
comprise 823 s in Windowed Timing (WT) mode (the first 7 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Osborne et
al. (GCN Circ. 17369
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 ).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=1.12 (+0.15, -0.13). At T+161 s  the decay
flattens to an alpha of 0.62 (+0.03, -0.04) before breaking again at
T+833 s to a final decay with index alpha=1.256 (+0.032, -0.026).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.86 (+/-0.04). The
best-fitting absorption column is  3.82 (+0.21, -0.20) x 10^21 cm^-2,
in excess of the Galactic value of 5.8 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 2.30 (+0.17, -0.16)
and a best-fitting absorption column of 4.7 (+0.8, -0.7) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.4 x 10^-11 (6.7 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     4.7 (+0.8, -0.7) x 10^21 cm^-2
Galactic foreground: 5.8 x 10^20 cm^-2
Excess significance: 9.3 sigma
Photon index:	     2.30 (+0.17, -0.16)

If the light curve continues to decay with a power-law decay index of
1.256, the count rate at T+24 hours will be 0.037 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x
10^-12 (2.4 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/00629302.

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

F. Knust, T. Schweyer, J. Bolmer, J. Greiner (all MPE Garching) report on behalf of the GROND team: 

We
 observed the field of GRB 150201A (Swift trigger 629302; J. K. Cannizzo
 et al., GCN #17368
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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 telescope at ESO La
 Silla Observatory (Chile). Observations
 started at  00:47 UT on 2015-02-02, 11hrs after the GRB trigger. They 
were performed at an average seeing of 1.64" and at an average airmass 
of 2.1. We do not detect a source within the Swift-XRT error circle reported by J.P. Osborne et al. (GCN #17369
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 ) down to 

g' > 23.2 mag, r' > 23.1 mag, i' > 23.5 mag, z' > 23.6 mag, J > 21.5 mag, H > 21.0 mag, and K > 19.4 mag. 
The
 given limits are derived based on calibrating the images against GROND 
zeropoints and 2MASS field stars and are not corrected for the Galactic 
foreground extinction corresponding to a reddening of E_(B-V)= 0.012 in 
the direction of the burst (Schlegel et al. 1998).

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

The long-duration, intense GRB 150201A
(Swift BAT trigger 629302: Cannizzo et al., GCN 17368
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 ;
Fermi-GBM detection: Yu and Pelassa, GCN 17370
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 )
triggered Konus-Wind at T0=49611.653 s UT (13:46:51.653).

The burst light curve shows a double-peaked pulse with a total duration 
of ~26 s.
The emission is seen up to ~10 MeV.
No post-burst activity was observed by Konus-Wind until ~T0+450s;
also, since the instrument switched to the read-out mode,
there are no triggered or waiting mode data available for the time
of the second GBM trigger 150201590 (14:09:56 UT; GCN 17370
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 ).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150201_T49611/

As observed by Konus-Wind, the burst
had a fluence of 6.18(-0.22,+0.23)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+1.712 s,
of 2.10(-0.28,+0.30)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+22.272 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.20(-0.11,+0.13),
the high energy photon index beta = -2.89(-0.27,+0.17),
the peak energy 123(-6,+5) keV
(chi2 = 88/93 dof)

The spectrum near the maximum count rate
(measured from T0 to T0+2.048 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.77(-0.12,+0.14),
the high energy photon index beta = -2.47(-0.25,+0.17),
the peak energy 193(-20,+21) keV
(chi2 = 65/50 dof)

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

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

Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 150201A (trigger #629302)
(Cannizzo, et al., GCN Circ. 17368
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 ).  The BAT ground-calculated position is
RA, Dec = 11.820 -37.620 deg which is
    RA(J2000)  = 00h 47m 16.8s
    Dec(J2000) =  -37d 37' 10"
with an uncertainty of 1.7 arcmin,(radius, sys+stat, 90% containment).
It is 0.6 arcmin from the XRT enhanced position. The partial coding was 3%.

The burst was outside the BAT calibrated field of view.  It came into the field
during the slew to point the narrow-field instruments. The earliest calibrated
event data starts at about T+22 s. The non-weighted light curve shows two main
peaks at about T-3 and T+1 seconds. The emission is detectable out to
approximately T+50 sec.  T90 (15-350 keV) is 26.1 +- 5.2 sec (estimated error 
including systematics).

The time-averaged spectrum from T+22.2 to T+49.0 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.32 +- 0.24.  The fluence in the 15-150 keV band is 7.8 +- 1.2 x 10^-07 
erg/cm2. This calibrated fluence is on the order of 5% of the total fluence.
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/629302/BA/

F. E. Marshall (NASA/GSFC) and J. K. Cannizzo (CRESST/GSFC/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150201A
93 s after the BAT trigger (Cannizzo et al., GCN Circ. 17368
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 ).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 17369
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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         >21.0
u_FC               306          556          246         >20.4
white               93          913          239         >21.5
v                  635          829           39         >18.6
b                  561          755           35         >19.8
u                  306          729          265         >20.3
w1                 685          705           19         >19.6
w2                 784          804           19         >19.6

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).