GRB 150819A

T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
S. B. Cenko (GSFC), V. D'Elia (ASDC), L. Izzo (URoma/ICRA),
J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC) and
B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team:

At 00:50:08 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 150819A (trigger=652643).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 42.337, +9.784 which is 
   RA(J2000)  =  02h 49m 21s
   Dec(J2000) = +09d 47' 02"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is typical for image triggers, the real-time
light curve does not show anything significant. 

The XRT began observing the field at 00:52:27.1 UT, 138.1 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 42.33146, 9.80665 which is
equivalent to:
   RA(J2000)  = 02h 49m 19.55s
   Dec(J2000) = +09d 48' 23.9"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 83 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 1.85
x 10^21 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 142 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
0.22. 

Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.com). 
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 150819A, we find an
enhanced XRT position of the afterglow: RA, Dec: 42.3335, 9.8075 which
is equivalent to:
   RA (J2000)  = 02 49 20.03
   Dec (J2000) = +09 48 26.9
with an uncertainty of 2.0 arcseconds (radius, 90% confidence).
Analysis of the promptly available data is online at
http://www.swift.ac.uk/sper/652643.

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.

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

Using 2467 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 150819A, 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 = 42.33310, +9.80748 which is equivalent
to:

RA (J2000): 02h 49m 19.94s
Dec (J2000): +09d 48' 26.9"

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.

A. A. Breeveld (UCL-MSSL) and T. N. Ukwatta (LANL)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150819A 
143 s after the BAT trigger (Ukwatta et al., GCN Circ. 18163
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 ).
No optical afterglow consistent with the XRT position (Evans et al. GCN 
Circ. 18167
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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           143          292          147         >21.0
u_FC               301          551          246         >20.2
white              143         7062          569         >21.4
v                  631         6037          274         >19.6
b                  557         6857          274         >20.3
u                  301         6652          501         >20.4
w1                 680         6447          274         >20.0
m2                 656         6242          274         >19.9
w2                 607         7135          346         >20.4

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.22 in the direction of the 
burst (Schlegel et al. 1998).

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

V. Lipunov, E. Gorbovskoy,  N.Tyurina, V.Kornilov,
P.Balanutsa,A.Kuznetsov,D.Kuvshinov,
Lomonosov Moscow State University, Sternberg Astronomical Institute

K.Ivanov, O.Gres, N.M.Budnev, S.Yazev,
Irkutsk State University

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

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

V.Yurkov, Yu.Sergienko, D.Varda, E.Sinyakov, A.Gabovich
Blagoveschensk Educational State University, Blagoveschensk

V.Krushinski, I.Zalozhnih
Ural Federal University, Kourovka

Hugo Levato and Carlos Saffe
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)

Claudio Mallamaci, Carlos Lopez and Federico Podest
Observatorio Astronomico Felix Aguilar (OAFA)

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in IAC was pointed to the  GRB150819.03 25 sec after notice time 
and 100 sec after trigger time at 2015-08-19 00:51:51 UT. On our first 
(20s exposure)  set we haven`t found optical transient  within SWIFT 
error-box (Ukwatta, Barthelmy  et al., GCN 18163
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 ; Evans, GCN 18165
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 ; 
Evans et al., GCN 18167
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 ). Zenit distance was aboute ~76 degrees.
The 5-sigma upper limit has been about 17.5 mag
Our results are:

T_start     T-Tmid  Expt.   Mlimit Coadd
00:51:51.6    112     20     17.5    1
00:51:51.6    163     90     18.0    3
00:54:05.5    337    180     18.9    3
00:51:51.6    536    760     19.8   10
01:06:31.0   1995   1800     20.4   10


The message may be cited.

T. Sakamoto (AGU), S. D. Barthelmy (GSFC), 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 downlinks,
we report further analysis of BAT GRB 150819A (trigger #652643)
(Ukwatta, et al., GCN Circ. `8`63).  The BAT ground-calculated position is
RA, Dec = 42.340, 9.787 deg, which is 
   RA(J2000)  =  02h 49m 21.5s 
   Dec(J2000) = +09d 47' 11.6" 
with an uncertainty of 2.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 93%.
 
the mask-weighted light curve shows a broad peaking starting at ~T+10 sec,
peaking at ~T+40 sec, and ending at ~T+70 sec.
T90 (15-350 keV) is 52.1 +- 12.9 sec (estimated error including systematics).
 
The time-averaged spectrum from T+14.18 to T+73.46 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.72 +- 0.27.  The fluence in the 15-150 keV band is 4.8 +- 0.9 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+17.70 sec in the 15-150 keV band
is 0.3 +- 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/652643/BA/

B.P. Gompertz (U. Leicester), A. D'ai (INAF-IASFPA), A. Maselli 
(INAF-IASFPA), A. Melandri (INAF-OAB), J.A. Kennea (PSU), B. Sbarufatti
(INAF-OAB/PSU), D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L.
Page (U. Leicester) and T.N. Ukwatta report on behalf of the Swift-XRT
team:

We have analysed 7.1 ks of XRT data for GRB 150819A (Ukwatta et al. GCN
Circ. 18163
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 ), from 122 s to 34.3 ks after the  BAT trigger. The data
comprise 43 s in Windowed Timing (WT) mode (the first 9 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 Evans et
al. (GCN Circ. 18165
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 ).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.62 (+/-0.09).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.42 (+0.24, -0.23). The
best-fitting absorption column is  6.6 (+2.3, -1.9) x 10^21 cm^-2, in
excess of the Galactic value of 1.8 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 6.1 x 10^-11 (7.8 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     6.6 (+2.3, -1.9) x 10^21 cm^-2
Galactic foreground: 1.8 x 10^21 cm^-2
Excess significance: 4.1 sigma
Photon index:	     1.42 (+0.24, -0.23)

If the light curve continues to decay with a power-law decay index of
1.62, the count rate at T+24 hours will be 2.0 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.2 x
10^-14 (1.6 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00652643.

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

Alan M. Watson (UNAM), Nat Butler (ASU), Alexander Kutyrev (GSFC), William 
H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier 
Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (ORAU/GSFC), 
Eleonora Troja (GSFC), Owen Littlejohns (ASU), Enrico Ramirez-Ruiz (UCSC), 
José A. de Diego (UNAM), Leonid Georgiev (UNAM), Jesús González (UNAM), 
Carlos Román-Zúñiga (UNAM), Neil Gehrels (GSFC), Harvey Moseley (GSFC), 
John Capone (UMD), V. Zach Golkhou (ASU), and Vicki Toy (UMD) report:

We observed the field of GRB 150819A (Ukwatta et al., GCN 18163
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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 Astronómico Nacional on 
Sierra San Pedro Mártir from 2015/08 19.33 to 2015/08 19.48 UTC (7.08 to 
10.60 hours after the BAT trigger), obtaining a total of 2.80 hours 
exposure in the r and i bands.

For a source within the enhanced Swift-XRT error circle (Evans et al., GCN 
18165
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 ), in comparison with the USNO-B1 and 2MASS catalogs, we obtain the 
following upper limits (3-sigma):

   r > 23.60
   i > 23.91

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 Astronómico Nacional in San Pedro 
Mártir.

S. Schulze (PUC, MAS), D. Malesani, J. P. U. Fynbo (DARK, NBI), J. Duus, T. Hinz-Berg, O. Busborg Jensen (NBI) and P. Jakobsson (U Iceland) report on behalf a larger collaboration:

We observed the field of GRB 150819A (Ukwatta et al., GCN 18163
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 ) with the Nordic Optical Telescope (NOT) equipped with ALFOSC. We obtained 4 images in the I band and 3 images in the z band with an individual sub-exposure time of 300 s. Observations started at 02:01 UT on August 19 (i.e. 1.19 hr after the burst).

We detect no credible source in the co-added I and z band images at the refined XRT localisation (Evans et al., GCN 18167
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 ). The limiting magnitude of the I-band image is 23 mag (3 sigma, Vega). This value is not corrected for foreground extinction. The flux calibration of the z-band image is still pending.

E. Mazaeva (IKI),  E. Klunko (ISTP), I. Reva (Fesenkov Astrophysical 
Institute), A. Kusakin (Fesenkov Astrophysical Institute), A. Volnova 
(IKI), I. Korobtsev (ISTP),  A. Pozanenko (IKI) report on behalf of 
larger GRB follow-up collaboration:

We observed the field of the Swift GRB 150819A (Ukwatta  et al., GCN 
18163
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 ) with AZT-33IK telescope of Sayan observatory (Mondy) and 
Zeiss-1000 (West) 1-m telescope of Tien Shan Astronomical Observatory. 
We obtained several images in R-filter in each telescope. We do not 
detect any source within enhanced XRT error circle (Evans et al., GCN 
18167
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 ).
Upper limits of the field are  following

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

2015-08-19 19:06:09   0.78197  R        30*120  22.7         AZT-33IK
2015-08-19 21:57:51   0.89889  R        10*300  19.4         Zeiss-1000

Photometry is based on USNO-B1.0 stars:
USNO-B.1_id    R2
0997-0042082 17.56
0997-0042080 18.70