GRB 180102A

K. L. Page (U Leicester), A. A. Breeveld (UCL-MSSL),
D. N. Burrows (PSU), A. Deich (PSU), C. Gronwall (PSU),
J.D. Gropp (PSU), J. A. Kennea (PSU), H. A. Krimm (NSF/USRA),
N. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC),
A. Melandri (INAF-OAB), D. M. Palmer (LANL), M. H. Siegel (PSU) and
A. Tohuvavohu (PSU) report on behalf of the Swift Team:

At 15:49:44 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180102A (trigger=802999).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 203.115, +62.148 which is 
   RA(J2000) = 13h 32m 28s
   Dec(J2000) = +62d 08' 53"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked
structure with a duration of about 40 sec.  The peak count rate
was ~1800 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began observing the field at 15:50:54.4 UT, 70.2 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 203.06761, 62.17091 which is equivalent
to:
   RA(J2000)  = 13h 32m 16.23s
   Dec(J2000) = +62d 10' 15.3"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 114 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.  We cannot determine whether the source is
fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 1.88
x 10^20 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 73 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 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 0.01. 

Burst Advocate for this burst is K. L. Page (klp5 AT leicester.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.)

P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:

Using  promptly downlinked XRT event data for GRB 180102A, we find an
enhanced XRT position of the afterglow: RA, Dec: 203.0669, 62.1718
which is equivalent to:
   RA (J2000)  = 13 32 16.07
   Dec (J2000) = +62 10 18.6
with an uncertainty of 2.1 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/802999.

Position enhancement is is described by Goad et al. (2007, A&A, 476,
1401) and Evans et al. (2009, MNRAS, 397, 1177).

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

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

Using 611 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 180102A, 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 = 203.06658, +62.17177 which is equivalent
to:

RA (J2000): 13h 32m 15.98s
Dec (J2000): +62d 10' 18.4"

with an uncertainty of 2.0 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. Veres (UAH) reports on behalf of the Fermi GBM Team:

"At 15:49:47.21 UT on 2 January 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180102A (trigger 536600992 / 180102660) which
was also detected by Swift/BAT (Page et al., GCN 22292
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 ).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 60 degrees.

The GBM light curve consists of a single pulse
with a duration (T90) of about 16 s (50-300 keV).
The time-averaged spectrum from T0-6.1 s to T0+2.0 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.40 +/- 0.44 and
the cutoff energy, parameterized as Epeak, is 54.9 +/- 6.7 keV.

The event fluence (10-1000 keV) in this time interval is
(4.31 +/- 0.45)E-7 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.7 s in the 10-1000 keV band
is 1.76 +/- 0.19 ph/s/cm^2.

A Band function fits the spectrum equally well with Epeak= 41.8 +/- 9.2 keV,
 alpha = 0.59 +/- 1.18 and beta = 2.52 +/- 0.35.

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

A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), D.N. Burrows (PSU), A.
Tohuvavohu (PSU), S. J. LaPorte (PSU), J.P. Osborne (U. Leicester),
A.P. Beardmore (U. Leicester), P. D'Avanzo (INAF-OAB) and K.L. Page
report on behalf of the Swift-XRT team:

We have analysed 6.7 ks of XRT data for GRB 180102A (Page et al. GCN
Circ. 22292
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 ), from 82 s to 19.2 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. 22293
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 ).

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.55 (+/-0.06).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.31 (+0.32, -0.30). The
best-fitting absorption column is  4.0 (+1.4, -1.2) x 10^21 cm^-2, in
excess of the Galactic value of 1.9 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 3.3 x 10^-11 (6.3 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     4.0 (+1.4, -1.2) x 10^21 cm^-2
Galactic foreground: 1.9 x 10^20 cm^-2
Excess significance: 5.2 sigma
Photon index:	     2.31 (+0.32, -0.30)

If the light curve continues to decay with a power-law decay index of
0.55, the count rate at T+24 hours will be 6.5 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.2 x
10^-13 (4.1 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/00802999.

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

V. Lipunov, E. Gorbovskoy, N.Tyurina,  V.Kornilov, D.Kuvshinov, 
A.V.Krylov, I.Gorbunov, P.Balanutsa, A.Kuznetsov, V.V.Chazov, D. Vlasenko
Lomonosov Moscow State University, Sternberg Astronomical Institut of MSU

V.Yurkov, Yu.Sergienko
Blagoveschensk Educational State University, Blagoveschensk

R.Podesta, C.Lopez, F. Podesta Observatorio Astronomico Felix Aguilar (OAFA),
National University of San Juan, Argentina

H. Levato, C. Saffe
Instituto de Ciencias Astronomicas,de la Tierra y del Espacio (ICATE),
San Juan, Argentina

D.Buckley, S. Potter, A.Kniazev, M.Kotze
South African Astronomical Observatory

R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias

O.Gres, K.Ivanov, S.Yazev, N.M.Budnev, O.Gres, O.Chuvalaev, V.A.Poleshchuk,
Irkutsk State University

A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory


MASTER-Kislovodsk  robotic telescope (MASTER-Net: 
http://observ.pereplet.ru) 
located in Kislovodsk was pointed to the  GRB180102A 23 sec after notice 
time and 43 sec after trigger time at 2018-01-02 15:50:27 UT (Page et 
al., GCN #22292
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 ;  Veres GCN22295
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 ). On our first 
(10s exposure)  set we haven`t found optical transient  within Swift 
error-box (D'Ai et al., GCN #22296
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 ; Beardmore et al., GCN 22294
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 ).
The 5-sigma upper limit has been about 13.7 mag
The message may be cited.


The observations made on zenit distance = 74 degrees, galaxy latitude b = 
55 degree.
The moon (99 % bright part) is 14 degrees above the horizon. The distance 
between  moon and  object is 73
The sun  altitude  is -22.3 degree.
The object can be observed till sunrise at 2018-01-03 04:41:55.

MASTER-Tavrida  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Crimea was pointed to the  GRB180102.66 3221 sec after notice 
time and 3247 sec after trigger time at 2018-01-02 16:43:51 UT. On our 
22-th (180s exposure)  set we haven`t found optical transient  within 
SWIFT error-box (ra=203.113 dec=62.1472 r=0.05).
The message may be cited.


The observations made on zenit distance = 73 degrees, galaxy latitude b = 
55 degree.
The moon (99 % bright part) is 18 degrees above the horizon. The distance 
between  moon and  object is 73
The sun  altitude  is -25.8 degree.
The object can be observed till sunrise at 2018-01-03 05:20:03.

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Blagoveschensk was pointed to the  GRB180102.66 21451 sec after 
notice time and 21471 sec after trigger time at 2018-01-02 21:47:35 UT. We 
not optical transient within  SWIFT error-box (ra=203.113 dec=62.1472 
r=0.05) brighter then 16.7.

The 5-sigma upper limit has been about 16.24mag
The message may be cited.

The observations made on zenit distance = 12 degrees, galaxy latitude b = 
55 degree.
The moon (99 % bright part) is 20 degrees above the horizon. The distance 
between  moon and  object is 72
Observations started at twilight.
The sun  altitude  is -15.2 degree.
The object can be observed till sunrise at 2018-01-03 23:26:49

This message can be cited.

D. Malesani (DARK/NBI), K. E. Heintz (Univ. Iceland and DARK/NBI), A. 
Sagues Carracedo (NOT), Andreas Kjaer Dideriksen (Aarhus Univ.), report 
on behalf of a larger collaboration:

We observed the field of GRB 180102A (Page et al., GCN 22292
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 ; Veres, GCN 
22295
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 ) with the Nordic Optical Telescope (NOT) equipped with the AlFOSC 
camera. Observations were carried out in the SDSS r and z filters (900 
and 1000 s exposure, respectively), with a seeing of 1.5", and started 
on 2018 Jan 3.1769 UT (12.42 hr after the GRB trigger).

At the position of the X-ray counterpart (D'Ai et al., GCN 22296
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 ), no 
objects are detected down to (preliminary) limiting magnitudes r = 22.5, 
z = 22.0 (all AB, calibrated with reference to nearby Pan-STARRS stars).

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

The Swift/UVOT began settled observations of the field of GRB 180102A 74 
s after the BAT trigger (Page et al., GCN Circ. 22292
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 ).
No optical afterglow consistent with the XRT position (Beardmore et al. 
GCN Circ. 22294
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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            74          224          147         >20.8
u_FC               286          535          246         >19.9
white               74         7508          824         >21.3
v                  616         6484          352         >19.3
b                  541         7303          529         >20.3
u                  286         7098          717         >20.4
w1                 665         6893          529         >20.1
m2                 640         6688          350         >19.7
w2                 591         7692          528         >20.1

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).

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

Using the data set from T-61 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180102A (trigger #802999)
(Page et al. GCN Circ. 22292
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 ).  The BAT ground-calculated position is
RA, Dec = 203.078, 62.161 deg which is
  RA(J2000)  =  13h 32m 18.8s
  Dec(J2000) = +62d 09' 38.1"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 95%.

The mask-weighted light curve shows two overlapping pulses that starts
at ~ T-8 s and ends at ~ T+6 s. The main peak occurs at ~T+1 s.
T90 (15-350 keV) is 10.8 +- 1.7 sec (estimated error including systematics).

The time-averaged spectrum from T-7.62 to T+6.30 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.01 +- 0.18.  The fluence in the 15-150 keV band is 3.5 +- 0.4 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.80 sec in the 15-150 keV band
is 1.0 +- 0.1 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/802999/BA/

E. Mazaeva (IKI), A. Pozanenko (IKI), I. Reva (FAPHI), M. Krugov 
(FAPHI),  A. Volnova (IKI), A. Kusakin (FAPHI) report on behalf of 
larger GRB follow-up collaboration:

We observed the field of GRB 180102A (Page  et al., GCN 22292
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 )   with 
Zeiss-1000 1-m telescope of Tien Shan Astronomical Observatory starting 
on Jan. 02 (UT) 21:34:54. We took several images in R-filter.  We do not 
detect any new sources within enhanced XRT error circle (Beardmore et 
al., GCN 22294
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 ).  Preliminary photometry of the field is following.

Date        UT start t-T0     Filter Exp.    OT    Err.  UL
                       (mid, days)    (s)

2018-01-02  21:34:54 0.25428  R      21*120  n/d   n/d   20.6


The photometry is based on several nearby USNO-B1.0 stars.

Y. Kitaoka, T. Sakamoto (AGU)

We observed the field of GRB 180102A detected by Swift
(Page et al. GCN circ. 22292
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 ) with the 0.3 m AROMA-N telescope
located at Aoyama Gakuin University (Sagamihara, Japan).

10 images of 60 sec exposures were taken in the R filter starting
from January 2 on 15:52:26 (UT) about 3 minutes after the trigger
and stopped on 16:04:28 (UT).  We do not detect the optical afterglow
both in the individual images and the stacked image at the location of
the X-ray afterglow (Beardmore et al. GCN circ. 22294
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 ).  The estimated
five sigma upper limit is ~16.0 mag using the USNO-B1 catalog.