GRB 180314B

P. D'Avanzo (INAF-OAB), A. Deich (PSU), J.D. Gropp (PSU),
J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL),
B. Sbarufatti (PSU), M. H. Siegel (PSU) and A. Tohuvavohu (PSU) report
on behalf of the Neil Gehrels Swift Observatory Team:

At 22:23:36 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180314B (trigger=814305).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 297.866, +23.623 which is 
   RA(J2000) = 19h 51m 28s
   Dec(J2000) = +23d 37' 24"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a complex
structure with a duration of about 50 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 22:25:03.9 UT, 87.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 297.88663, 23.62434 which
is equivalent to:
   RA(J2000)  = 19h 51m 32.79s
   Dec(J2000) = +23d 37' 27.6"
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This
location is 68 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 consistent with the Galactic value of 8.94
x 10^21 cm^-2 (Willingale et al. 2013). 

The initial flux in the 2.5 s image was 6.44e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 94 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. Because of the density of
catalogued stars, further analysis is required to report an upper limit for any
afterglow in the region. No correction has been made for the large, but
uncertain, extinction expected. 

Burst Advocate for this burst is P. D'Avanzo (paolo.davanzo AT brera.inaf.it). 
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 180314B, we find an
enhanced XRT position of the afterglow: RA, Dec: 297.8867, 23.6243
which is equivalent to:
   RA (J2000)  = 19 51 32.82
   Dec (J2000) = +23 37 27.4
with an uncertainty of 1.9 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/814305.

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 2454 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 180314B, 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 = 297.88665, +23.62406 which is equivalent
to:

RA (J2000): 19h 51m 32.80s
Dec (J2000): +23d 37' 26.6"

with an uncertainty of 1.5 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.

J.A. Kennea (PSU), P.A. Evans (U. Leicester), S.L. Gibson (U.
Leicester), J.P. Osborne (U. Leicester), A. Melandri (INAF-OAB), V.
D'Elia (ASDC), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU) and P.
D'Avanzo report on behalf of the Swift-XRT team:

We have analysed 6.4 ks of XRT data for GRB 180314B (D'Avanzo et al.
GCN Circ. 22491
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 ), from 102 s to 19.8 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.
22492
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 ).

The light curve can be modelled with an initial power-law decay with an
index of alpha=0.08 (+0.09, -0.07), followed by a break at T+1503 s to
an alpha of 1.42 (+/-0.08).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.55 (+0.21, -0.20). The
best-fitting absorption column is  2.14 (+0.29, -0.27) x 10^22 cm^-2,
in excess of the Galactic value of 8.9 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 4.8 x 10^-11 (1.9 x 10^-10) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     2.14 (+0.29, -0.27) x 10^22 cm^-2
Galactic foreground: 8.9 x 10^21 cm^-2
Excess significance: 7.6 sigma
Photon index:	     2.55 (+0.21, -0.20)

If the light curve continues to decay with a power-law decay index of
1.42, the count rate at T+24 hours will be 5.5 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.7 x
10^-13 (1.1 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/00814305.

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

S. R. Oates (U.Warwick) and P. D'Avanzo (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180314B
94 s after the BAT trigger (D'Avanzo et al., GCN Circ. 22491
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 ).
No optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 22494
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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            94          244          147         >19.6
u_FC               308          558          246         >19.3
white               94         7249          666         >19.7
v                  638         7660          607         >18.4
b                  563        11580          471         >19.3
u                  308         8274          834         >19.6
w1                 687         8070          588         >19.5
m2                 662         7865          607         >20.4
w2                 614         7455          607         >20.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 2.21 in the direction of the burst
(Schlegel et al. 1998).

E. Mazaeva (IKI), A. Pozanenko (IKI),  A. Novichonok (KIAM, PetrSU),  I. 
Nikolenko (CrAO), A. Volnova (IKI), I. Molotov (KIAM) report on behalf 
of larger GRB follow-up collaboration:

We observed the field of  Swift GRB 180314B (D'Avanzo et al., GCN 22491
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 ) 
with Zeiss-1000/Koshka (CrAO) telescope starting March 15 (UT) 01:55:39.
We obtained several  images in R-filter. We do not detect any source 
within enhanced Swift-XRT position (Beardmore et al., GCN 22494
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 ). 
Preliminary photometry of the field is following.

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

2018-03-15  01:55:39  0.15459    R     7*180  n/d   n/d   22.2

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

USNO-B1_id   R1
1135-0426232 15.02
1135-0426125 15.64
1136-0433074 16.46

S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
P. D'Avanzo (INAF-OAB), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), 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+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180314B (trigger #814305)
(D'Avanzo et al., GCN Circ. 22491
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 ).  The BAT ground-calculated position is
RA, Dec = 297.855, 23.634 deg which is
  RA(J2000)  =  19h 51m 25.3s
  Dec(J2000) = +23d 38' 04.1"
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 66%.

The mask-weighted light curve shows a multi-peaked structure that starts
at ~ T-50 sec and ends at ~ T+35 s. The main peak occurs at ~ T0.
T90 (15-350 keV) is 73.0 +- 9.4 sec (estimated error including systematics).

The time-averaged spectrum from T-47.6 to T+34.4 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.41 +- 0.25.  The fluence in the 15-150 keV band is 9.6 +- 1.4 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.57 sec in the 15-150 keV band
is 1.1 +- 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/814305/BA/

Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC),
William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J.
Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (UVI),
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz
(UCSC), Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey
Moseley (GSFC), John Capone (UMD), V. Zach Golkhou (U. Wash.), and Vicki
Toy (UMD) report:

We observed the field of GRB 180314B (D'Avanzo et al., GCN 22491
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 ) with
the Reionization and Transients Infrared Camera (RATIR; www.ratir.org)
on the 1.5m Harold Johnson Telescope at the Observatorio Astron��mico
Nacional on Sierra San Pedro M��rtir from 2018/03 15.46 to 2018/03 15.52
UTC (12.55 to 13.99 hours after the BAT trigger), obtaining a total of
1.07 hours exposure in the r and i bands.

For a source within the Swift-XRT error circle, in comparison with the
USNO-B1 and 2MASS catalogs, we obtain the following 3-sigma upper
limits:

 r	> 23.29
 i	> 22.90

These magnitudes are in the AB system and are not corrected for Galactic
extinction in the direction of the GRB.

We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.