GRB 151022A

P. D'Avanzo (INAF-OAB), D. N. Burrows (PSU),
H. A. Krimm (CRESST/GSFC/USRA), A. Melandri (INAF-OAB),
P. T. O'Brien (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL) and B. Sbarufatti (INAF-OAB/PSU) report on behalf
of the Swift Team:

At 14:06:32 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 151022A (trigger=661036).  Swift slewed to the burst at 
T0+300 seconds.  The BAT on-board calculated location is 
RA, Dec 349.213, +55.813 which is 
   RA(J2000) = 23h 16m 51s
   Dec(J2000) = +55d 48' 48"
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 20 sec.  The peak count rate
was ~1400 counts/sec (15-350 keV), at ~6 sec after the trigger. 

The XRT began observing the field at 14:11:32.6 UT, 300.5 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 349.19815, 55.81207 which
is equivalent to:
   RA(J2000)  = 23h 16m 47.56s
   Dec(J2000) = +55d 48' 43.5"
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This
location is 30 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 4.74
x 10^21 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 304 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 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.)

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

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

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

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

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

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


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 Ural was pointed to the  GRB151022A  16 after notice time and 
76 sec after trigger time at 2015-10-22 14:07:48 UT in two polarizations. 
On our first (20s exposure)  set we haven`t found optical transient 
within SWIFT error-box (ra=23 16 51 dec=+55 48 47 r=0.05).
The 5-sigma upper limit has been about 16.0 mag
The reduction is continued.
The message may be cited.

[GCN OPS NOTE(23oct15):  The GRB name in the Subject line
was changed from "0922A" to "1022A".]

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

Using  promptly downlinked XRT event data for GRB 151022A, we find an
enhanced XRT position of the afterglow: RA, Dec: 349.1969, 55.8119
which is equivalent to:
   RA (J2000)  = 23 16 47.25
   Dec (J2000) = +55 48 42.9
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/661036.

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.

K. S. Kawabata, R. Itoh, T. Nakaoka, M. Yoshida (Hiroshima Univ.), K. Tsumura
(Tohoku Univ.), and K. Arimatsu (NAOJ) report on behalf of Kanata team:

We performed a series of optical imaging-polarimetry for the optical afterglow 
of GRB151022A (D'Avanzo et al., GCN 18436
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 ) from 119 sec after the Swift/BAT 
trigger with HOWPol attached to the 1.5-m Kanata telescope at Higashi-Hiroshima
Observatory, Japan.

We could not detect any afterglow within the XRT error circle reported in the 
GCN 18436
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 . We obtained the following preliminary upper limits (3-sigma) in our 
first image (mid-time 134 sec after the trigger) calibrated with UCAC4:

Rc > 17.0

Further analysis is ongoing.

K. Yanagisawa, D. Kuroda, Y. Shimizu, H. Izumiura(OAO/NAOJ),
M. Yoshida (Hiroshima), K. Ohta(Kyoto) and N. Kawai(Tokyo Tech.)
report on behalf of the MITSuME collaboration:

We observed the field of GRB 151022A (D'Avanzo et al., GCN 18436
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 )
in Ks-band with a wide-field near infrared imager at Okayama
Astrophysical Observatory (Japan).  The imager has effective
aperture of 0.91 m.

Observations started from 14:13 UT on 22th October, 0.12h after
the BAT trigger, to 14:56 UT. The total exposure of 17.0 min
was successfully obtained.

In our co-add image, we did not find any new point source within
the enhanced XRT error circle (Evans et al., GCN 18438
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 ) down to limiting
magnitude of Ks=14.8 (Vega, S/N=10). The photometric calibration was
made against 2MASS field stars.

T0+[sec]    MID-UT     T-EXP[sec]      Ks
---------------------------------------------------
 +1,721     14:35      1,020.0         >14.8
---------------------------------------------------
T0+ : Elapsed time after the burt [sec]
T-EXP: Total Exposure time [sec]

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

We observed the field of Swift GRB 151022A (D'Avanzo et al., GCN 18436
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 ) 
with AZT-33IK telescope of Sayan observatory (Mondy) starting on Oct. 22 
(UT) 15:05:04. We obtained several images in R-filter of 30 s exposure. 
    Within XRT error circle (Evans, GCN 18438
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 )  we do not detect any 
optical source in any single image. Upper limit (3 sigma) of a single 
image is R ~ 19.4m. Photometry is based on nearly USNO-B1.0 (R2) stars.

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

Using 2395 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 151022A, 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 = 349.19671, +55.81182 which is equivalent
to:

RA (J2000): 23h 16m 47.21s
Dec (J2000): +55d 48' 42.6"

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.

D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ),
S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech)
report on behalf of MITSuME and OISTER collaboration:

We observed the field of GRB 151022A (D'Avanzo et al., GCNC 18436)
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.

The observation started on 2015-10-22 14:08:12 UT (~100 sec after the burst).
We did not find any new point source within the enhanced XRT circle
(Beardmore et al., GCNC 18444) in all the three bands.

Three sigma upper limits of the OT are listed below.
We used SDSS-DR8 catalog for flux calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'    Rc     Ic
-----------------------------------------------------
0.00471    14:13:19     540.0   >19.0  >19.0  >18.3
0.04291    15:08:20    6240.0   >20.1  >19.9  >19.1
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]

S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), A. Maselli	(INAF-IASFPA), A. Melandri (INAF-OAB), B.
Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R. Roegiers (PSU)
and P. D'Avanzo report on behalf of the Swift-XRT team:

We have analysed 6.4 ks of XRT data for GRB 151022A (D'Avanzo et al.
GCN Circ. 18436
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 ), from 286 s to 31.4 ks after the  BAT trigger. The
data comprise 17 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
Beardmore et al. (GCN Circ. 18438
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 ).

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.82 (+0.17, -0.14).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.39 (+0.26, -0.24). The
best-fitting absorption column is  6.2 (+2.6, -1.5) x 10^21 cm^-2,
consistent with the Galactic value of 4.7 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 (7.7 x
10^-11) erg cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     6.2 (+2.6, -1.5) x 10^21 cm^-2
Galactic foreground: 4.7 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.39 (+0.26, -0.24)

If the light curve continues to decay with a power-law decay index of
1.82, the count rate at T+24 hours will be 7.2 x 10^-5 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.4 x
10^-15 (5.5 x 10^-15) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00661036.

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

[GCN OPS NOTE(15Jun16):  Because of a processing error, two circulars
received the same ID Number.  The second was given an "a' suffix.]

GCN OPS NOTE: The new GCN database requires the GCN Circular ID to be a number. Therefore, the previous GCN number assigned as 18448a was modified to 18448.5 during the GCN Circulars migration in April 2023.

Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Antonino Cucchiara (GSFC/STScI), 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 151022A (D'Avanzo, et al., GCN 18436
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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 2015/10 23.16 to 2015/10 23.18 UTC (13.77 to 14.17 hours after the BAT trigger), obtaining a total of 0.36 hours exposure in the r, i, and z bands.  For a source within the Swift-XRT error circle (Beardmore, et al., GCN 18444
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 ), in comparison with the SDSS DR9, we obtain the following upper limits (3-sigma):

   r > 23.11
   i > 23.04
   z > 19.84

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.

A. Y. Lien (GSFC/UMBC),S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
P. D'Avanzo (INAF-OAB), N. Gehrels (GSFC),H. A. Krimm (GSFC/USRA),
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-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 151022A (trigger #661036)
(D'Avanzo, et al., GCN Circ. 18436
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 ).  The BAT ground-calculated position is
RA, Dec = 349.223, 55.812 deg which is
  RA(J2000)  =  23h 16m 53.5s
  Dec(J2000) = +55d 48' 43.4"
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 35%.

The mask-weighted light curve shows a single FRED-like peak, with some
superimposed structure, peaking near the trigger time and fading to near
background by ~200 seconds. T90 (15-350 keV) is 116.7 +/- 23.0 sec
(estimated error including systematics).

The time-averaged spectrum from T-1.5 to T+132.8 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.98 +- 0.29.  The fluence in the 15-150 keV band is 1.1 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+10.37 sec in the 15-150 keV band
is 0.8 +- 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/661036/BA/

B. G. Balzer (PSU) 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 151022A
304 s after the BAT trigger (D'Avanzo et al., GCN Circ. 18436
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 ).
No optical afterglow consistent with the XRT position
(Evans GCN Circ. 18438
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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           304          454          147         >21.2
white              304         7836          902         >22.0
v                  461         8247          646         >20.1
b                  560         7632          430         >21.0
u                  535         7426          430         >21.2
w1                 510        12075          553         >19.7
m2                 486         8452          646         >20.3
w2                 609         8042          627         >20.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.56 in the direction of the burst
(Schlegel et al. 1998).

S. R. Oates (IAA-CSIC), S. Jeong (IAA-CSIC/SKKU), V. Casanova, J. C. Tello (IAA-CSIC) and
A. J. Castro-Tirado (IAA-CSIC/UMA), report on behalf of a larger collaboration:

We observed the field of GRB 151022A (D'Avanzo et al., GCN Circ. 18436
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 ) with the 1.5m
OSN telescope at Observatorio de Sierra Nevada (Spain). The observations
were carried out in the I band on Oct 22.79163 - 22.84025 (4.89 - 6.06 hours
post bust). We do not detect any new optical source within the enhanced XRT 
error circle (Beardmore et al., GCN Circ. 18444
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 ) down to a limiting magnitude of I ~21.5 mag.