GRB 150110B

P. A. Evans (U Leicester), S. D. Barthelmy (GSFC),
D. N. Burrows (PSU), N. Gehrels (NASA/GSFC),
C. J. Mountford (U Leicester) and K. L. Page (U Leicester) report on
behalf of the Swift Team:

At 22:08:30 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150110B (trigger=624606).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 289.360, +32.522, which is 
   RA(J2000)  =  19h 17m 26s
   Dec(J2000) = +32d 31' 20"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows multiple peaks
structure with a duration of about 12 sec.  The peak count rate
was ~2500 counts/sec (15-350 keV), at ~2 sec after the trigger. 

The XRT began observing the field at 22:09:31.0 UT, 61.0 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source with an enhanced position: RA, Dec 289.3749,
32.5233 which is equivalent to:
   RA(J2000)  = 19h 17m 29.97s
   Dec(J2000) = +32d 31' 24.0"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 45 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 (2.39 x
10^21 cm^-2, Willingale et al. 2013), with an excess column of 3
(+3.51/-2.95) x 10^21 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 65 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
0.20. 

Burst Advocate for this burst is P. A. Evans (pae9 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.)

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

Using 3739 s of XRT Photon Counting mode data and 6 UVOT
images for GRB 150110B, 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 = 289.37494, +32.52333 which is equivalent
to:

RA (J2000): 19h 17m 29.99s
Dec (J2000): +32d 31' 24.0"

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.

Matthew Stanbro (UAH) report on behalf of the Fermi GBM Team:

"At 22:08:31.91 UT on 10 January 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150110B (trigger 442620514 / 150110923)
which was also detected by the Swift/BAT (Evans et al. 2015, GCN 17291
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 )
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight is 22 degrees.

The GBM light curve consists of 1 peak
with a duration (T90) of about 2 s (50-300 keV).
The time-averaged spectrum from T0-1.54 s to T0+1.54 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.98 +/- 0.22 and
the cutoff energy, parameterized as Epeak, is 122.5 +/- 24.3 keV

The event fluence (10-1000 keV) in this time interval is
(5.30 +/- 0.61)E-07 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.06 s in the 8-1000 keV band
is 2.33 +/- 0.21 ph/s/cm^2.

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

N. P. M. Kuin (UCL-MSSL) and P. A. Evans (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150110B
65 s after the BAT trigger (Evans et al., GCN Circ. 17291
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 ).  No optical
afterglow consistent with the XRT position  (Beardmore et al., GCN
Circ. 17294
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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            65          215          147         >21.0
u_FC               277          527          246         >20.3
white               65        12665         1414         >21.7
v                  607         6471          452         >19.6
b                  532        11960         1140         >21.5
u                  277        11047         1394         >21.1
w1                 656         6881          452         >20.4
m2                 631         6676          452         >20.5
w2                 582         6267          452         >20.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.20 in the direction of the burst
(Schlegel et al. 1998).

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

We have analysed 8.9 ks of XRT data for GRB 150110B (Evans  et al. GCN
Circ. 17291
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 ),  from 73 s to 29.9 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. 17294
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 ).

The light curve can be modelled with  a power-law decay with a decay
index of alpha=1.01 (+/-0.07).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.06 (+0.28, -0.26). The
best-fitting absorption column is  6.0 (+1.9, -1.7) x 10^21 cm^-2, in
excess of the Galactic value of 2.4 x 10^21 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.1 x 10^-11 (7.1 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     6.0 (+1.9, -1.7) x 10^21 cm^-2
Galactic foreground: 2.4 x 10^21 cm^-2
Excess significance: 3.6 sigma
Photon index:	     2.06 (+0.28, -0.26)

If the light curve continues to decay with a power-law decay index of
1.01, the count rate at T+24 hours will be 1.9 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.8 x
10^-14 (1.4 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/00624606.

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

H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), P. A. Evans (U Leicester), N. Gehrels (GSFC),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (LANL)
(i.e. 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 150110B (trigger #624606)
(Evans, et al., GCN Circ. 17291
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 ).  The BAT ground-calculated position is
RA, Dec = 289.374, 32.529 deg, which is 
   RA(J2000)  =  19h 17m 29.7s 
   Dec(J2000) = +32d 31' 43.2" 
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.
 
The mask-weighted light curve shows two peaks starting at ~T-8 sec,
peaking at ~T-5 and ~T+2 sec, and ending at ~T+10 sec.
T90 (15-350 keV) is 10.6 +- 0.95 sec (estimated error including systematics).
 
The time-averaged spectrum from T-7.94 to T+3.77 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.89 +- 0.13.  The fluence in the 15-150 keV band is 4.9 +- 0.4 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+2.00 sec in the 15-150 keV band
is 1.4 +- 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/624606/BA/

E. Mazaeva (IKI), S. Schmalz (AIP), N. Tungalag (Research Center of 
Astronomy and Geophysics MAS),  A. Volnova (IKI), I.Molotov (KIAM), A. 
Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of GRB GRB 150110B (Evans et al., GCN 17291
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 ) with 
ORI-40 telescope of Khureltogot observatory. We obtained several 
unfiltered images on Jan. 10 starting on (UT) 22:31:36.  In a combined 
image of the first 40 frames we  do not detect any optical source within 
  enhanced Swift-XRT position (Beardmore et al., GCN 17294
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 ). A 
photometry of the combined image is following

Date        UT start  t-T0       Filter  Exp.   ULimit (3sigma)
                       (mid, days)        (s)

2015-01-10  22:31:36  0.03113    none    40*60  19.3


The photometry is based on USNO-B1.0 stars

USNO-B1_id       RA             DEC        R2
1224-0426323     289.294781   +32.470745   13.52
1225-0423392     289.295778   +32.569009   13.80

G. E. Anderson, R. P. Fender, T. D. Staley (University of Oxford),
A. J. van der Horst (George Washington University), A. Rowlinson (CASS)

We observed the position of GRB 150110B (Evans et al., GCN 17291
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 )
at 15 GHz with the Arcminute Microkelvin Imager (AMI-LA) starting on
2015 Jan 14.466 to 14.632 UT and 2015 Jan 16.415 to Jan 16.581,
corresponding to 3.5 and 5.5 days post-burst. On these two dates we
have detected a radio source coincident with the Swift-XRT position
(Beardmore et al., GCN 17294
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 ) with a preliminary flux of 0.25 +/- 0.05 mJy
and 0.47 +/- 0.05 mJy, respectively. There are no catalogued radio sources
at this position.

An earlier observation was conducted on 2015 Jan 11.434 to 11.580 UT,
corresponding to 0.5 days post-burst, yielding a 3 sigma flux upper limit
of 0.13 mJy.

Further AMI monitoring is planned. We thank the AMI staff for scheduling these observations.