GRB 131024B

H. A. Krimm (CRESST/GSFC/USRA), M. M. Chester (PSU),
S. T. Holland (STScI), J. A. Kennea (PSU), V. Mangano (PSU),
C. B. Markwardt (NASA/GSFC), F. E. Marshall (NASA/GSFC),
A. Maselli (INAF-IASFPA), J. L. Racusin (NASA/GSFC),
B. Sbarufatti (INAF-OAB/PSU), C. A. Swenson (PSU),
E. Troja (NASA/GSFC/UMCP) and B.-B. Zhang (UAH) report on behalf of
the Swift Team:

At 21:35:31 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 131024B (trigger=575754).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 144.403, +44.240 which is 
   RA(J2000) = 09h 37m 37s
   Dec(J2000) = +44d 14' 23"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multiple-peak
structure with a duration of about 30 sec.  The peak count rate
was ~1000 counts/sec (15-350 keV), at ~2 sec after the trigger. 

The XRT began observing the field at 21:37:21.8 UT, 110.5 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
fading, uncatalogued X-ray source with an enhanced position: RA, Dec
144.5032, 44.2715 which is equivalent to:
   RA(J2000)  = 09h 38m 00.76s
   Dec(J2000) = +44d 16' 17.6"
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This
location is 282 arcseconds from the BAT onboard position. 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 (1.27 x
10^20 cm^-2, Kalberla et al. 2005), with an excess column of 2.6
(+1.51/-1.36) x 10^21 cm^-2 (90% confidence). 

The initial flux in the 2.5 s image was 5.91e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 250 seconds with the U filter starting
278 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 19.2 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 18.0 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.02. 

Burst Advocate for this burst is H. A. Krimm (krimm AT milkyway.gsfc.nasa.gov). 
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.)

[GCN OPS NOTE(24oct13):  The Admin changed the burst name from an "A" to a "B"
in the first sentence.]

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

Using 1402 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 131024B, 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 = 144.50331, +44.27151 which is equivalent
to:

RA (J2000): 09h 38m 0.79s
Dec (J2000): +44d 16' 17.4"

with an uncertainty of 2.8 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. Xu (DARK/NBI), X. Zhang, C-H. Bai, A. Esamdin, L. Ma (XAO) report:

We observed the field of GRB 131024B (Krimm et al., GCN 15371
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 ) using the 1m
telescope located on Mt. Nanshan, Xinjiang, China. We obtained 4x300s
R-band frames at a mean time of  2013-10-24 23:21:53 UT, i.e., 1.773 hr
after the BAT trigger.

No optical source is detected within the XRT error circle in the stacked
image down to a limiting magnitude of R=21.0, calibrated with nearby SDSS
field.

H. A. Krimm (CRESST/GSFC/USRA), A. Maselli (INAF-IASFPA) and P. A.
Evans (U. Leicester) report on behalf of the Swift-XRT team:

We have analysed 5.5 ks of XRT data for GRB 131024B (Krimm  et al. GCN
Circ. 15371
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 ),  from 100 s to 29.1 ks after the	BAT trigger. The data
comprise 185 s in Windowed Timing (WT) mode (the first 8 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 15374).

The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=1.30 (+0.22, -0.47). At T+232 s  the decay
steepens to an alpha of 3.4 (+2.8, -1.0) before breaking again at T+328
s to a final decay with index alpha=1.72 (+0.13, -0.11).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.60 (+/-0.14). The
best-fitting absorption column is  1.9 (+0.5, -0.4) x 10^21 cm^-2, in
excess of the Galactic value of 1.3 x 10^20 cm^-2 (Kalberla et al.
2005). The PC mode spectrum has a photon index of 1.79 (+0.25, -0.23)
and a best-fitting absorption column of 1.0 (+/-0.6) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 4.1 x 10^-11 (5.0 x 10^-11) erg cm^-2
count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.0 (+/-0.6) x 10^21 cm^-2
Galactic foreground: 1.3 x 10^20 cm^-2
Excess significance: 2.6 sigma
Photon index:	     1.79 (+0.25, -0.23)

If the light curve continues to decay with a power-law decay index of
1.72, the count rate at T+24 hours will be 1.2 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.0 x
10^-15 (6.0 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/00575754.

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

L. P. Xin,   J. Y. Wei,   Y. L. Qiu, J. S. Deng,  J. Wang,  
X. H. Han and C. Wu on behalf of EAFON report:

We began to observe GRB 131024B  (Krimm et al., GCN 15371
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 ) 
with Xinglong 0.8-m TNT telescope at 21:38:56  (UT), 
about 3.4 min after the burst.  3*300 sec  R-band images were obtained. 

No any optical counterpart within the XRT error circle  was detected 
down to a limit of 18.4 mag in R band, calibrated by USNO B1.0 R2mag 
at the mean time of 11.25 min after the burst.

This message may be cited.

M. M. Chester (PSU) and H. A. Krimm (CRESST/GSFC/USRA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 131024B
121 s after the BAT trigger (Krimm et al., GCN Circ. 15371
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 ).
No optical afterglow consistent with the XRT position (Beardmore et 
al. GCN Circ. 15374
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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 second 
finding chart (FC) exposure and subsequent exposures are given in 
the following table.  (The first finding chart in White was 
incomplete and is not included in the analysis.)

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

u_FC               278          528          246         >19.7
white              559         5579          413         >21.8
v                  609         5990          413         >20.6
b                  535         5374          228         >20.5
u                  278         6484          539         >20.3
w1                 658         6401          413         >20.4
m2                4558         6195          393         >20.9
w2                 585         5785          413         >21.3

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).
************************************************************************
Dr. Margaret Chester				
Swift Deputy Mission Director              U.S. Mail:	
The Pennsylvania State University          Swift Explorer Program
Department of Astronomy & Astrophysics     2582 Gateway Drive
Office:  (814) 865-7746                    State College, PA  16801
Cell:  (814) 359-9026                      FAX:  (814) 865-9100

Antonino Cucchiara (ORAU/GSFC), Nat Butler (ASU), Alan M. Watson (UNAM), 
Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), 
Chris Klein (UCB), Ori Fox (UCB), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), 
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), and Harvey Moseley (GSFC) report:

We observed the field of GRB 131024B (Krimm, et al., GCN 15371
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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 2013/10 25.41 to 2013/10 25.52 UTC (12.28
to 14.87 hours after the BAT trigger), obtaining a total of 1.78 hours
exposure in the r and i bands and 0.74 hours exposure in the Z,
Y, J, and H bands.

For a source within the Swift-XRT error circle, in comparison with the SDSS DR9 
and 2MASS, we obtain the following upper limits (3-sigma):

  r > 23.68
  i > 23.35
  Z > 22.44
  Y > 22.01
  J > 21.75
  H > 21.49

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.

Bin-Bin Zhang (UAH) reports on behalf of the Fermi GBM Team:

"At 21:35:28.85 UT on October 24 2013, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 131024B (trigger 404343331/131024900), which was also
detected by Swift (Krimm et al., GCN 15371
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 ). The GBM on-ground location
 is consistent with the Swift/XRT position (Beardmore et al., GCN 15374
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 ). The angle from
the Fermi LAT boresight is 83 degrees.

The GBM light curve consists of a multiple-peak structure with a duration
of about 52 s (50-300 keV). The time-averaged spectrum from T0+0 s to T0+41 s
is well best fit with a power law function with an exponential high-energy cutoff
parameterized as Epeak = 1047 +/- 627 keV and an Index = -1.01 +/- 0.12. The event
fluence (10-1000 keV) in this time interval is (6.35 +/- 0.61)E-06 erg/cm^2. The
1.0-sec peak photon flux measured starting from T0+1 s in the 10-1000 keV band
is 1.48 +/- 0.2 ph/s/cm^2.

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

W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC),
T. N. Ukwatta (MSU) (i.e. the Swift-BAT team):

Using the data set from T-61 to T+242 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 131024B (trigger #575754)
(Krimm, et al., GCN Circ. 15371
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 ).  The BAT ground-calculated position is
RA, Dec = 144.464, 44.284 deg which is
    RA(J2000)  =  09h 37m 51.3s
    Dec(J2000) = +44d 17' 02.1"
with an uncertainty of 2.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 40%.

The mask-weighted light curve shows activity starting around T-10 sec and
continuing to ~T+100 sec.  There are several weak peak superimposed.
T90 (15-350 keV) is 64.00 +- 22 sec (estimated error including systematics).

The time-averaged spectrum from T-12.59 to T+51.41 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
0.85 +- 0.23.  The fluence in the 15-150 keV band is 1.2 +- 0.2 x 10^-6 erg/cm2. 
  The 1-sec peak photon flux measured from T+10.91 sec in the 15-150 keV band is 
0.1 +- 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/575754/BA/

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

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

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

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

V. Krushinski, I. Zalozhnich,  A. Popov, A. Bourdanov
Ural Federal University

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

C. Mallamaci, C. Lopez and F. Podest
Observatorio Astronomico Felix Aguilar (OAFA)

MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in Kislovodsk was pointed to the  GRB131024B 27 sec s after notice 
time and 36 sec after GRB time at 2013-10-24T21-36-07.864 UT. On our first 
(10s exposure) set we haven`t found optical transient  within SWIFT 
error-box (Krimm et. al GCN15371
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 ).
The 5-sigma upper limit has been about 17.2 mag.
This is the prompt observations becaus GRB duration time T_90 = 64+-22 sec 
(Baumgartner et al., GCN Baumgartner).
Such long circular delay was due to with daily power cut on observatory.
The message may be cited.

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

We observed the field of the Swift GRB 131024B (Krimm et al., GCN 15371
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 ) 
with AZT-33IK telescope of Sayan observatory (Mondy) starting Oct., 24 
(UT) 21:49:49, i.e. in ~14 minutes after the burst trigger. We obtained 
several images in R-filter with exposure of 30 and 60 seconds. Within 
the enhanced XRT circle (Beardmore et al., GCN 15374
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 ) we did not detect 
any optical counterpart.

The details of the photometry are the following:

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

21:49:49    0.02074       R       1860   n/d   21.8
21:49:49    0.03325       R       4020   n/d   22.5

The photometry is based 3 SDSS stars, R (gri -> R transformations by 
Lupton 2005):

SDSS id             R
J093757.56+441843.7 15.803
J093748.35+441919.6 17.774
J093744.86+441756.7 15.530

A. Volnova (IKI), R. Inasaridze (AAO), G. Inasaridze (AAO), V. 
Zhuzhunadze (AAO), Yu. Krugly (IA KhNU), I. Molotov (KIAM), A. Pozanenko 
(IKI) report on behalf of larger GRB follow-up collaboration:

We observed the field of Swift GRB 131024B (Krimm et al., GCN 15371
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 ) 
with AS-32 telescope of Abastumani Observatory starting Oct., 25 (UT) 
00:26:12. We obtained several unfiltered images with exposures of 120 s. 
On stacked images within the enhanced XRT circle (Beardmore et al., GCN 
15374
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 ) we did not detect any optical counterpart.

The details of the photometry are the following:

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

00:26:12   0.16094     None   46x120   n/d     22.6

The photometry is based 3 SDSS stars, R (gri -> R transformations by
Lupton 2005):

SDSS id             R
J093757.56+441843.7 15.803
J093748.35+441919.6 17.774
J093744.86+441756.7 15.530

Y. Ishida, M. Tashiro, Y. Terada, T. Yasuda, H. Ueno, S. Sugimoto
(Saitama U.), M. Ohno, K. Takaki, T. Kawano, R. Nakamura, S. Furui,
Y. Fukazawa (Hiroshima U.), M. Yamauchi, N. Ohmori, M. Akiyama
(Univ. of Miyazaki), K. Yamaoka (Nagoya U.), S. Sugita (Ehime U.),
Y. E. Nakagawa, M. Kokubun, T. Takahashi (ISAS/JAXA), W. Iwakiri
(RIKEN), Y. Hanabata (ICRR), Y. Urata (NCU), K. Nakazawa,
K. Makishima (Univ. of Tokyo) on behalf of the Suzaku WAM team, report:

The long GRB 131024B (Krimm et al. GCN 15371
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 ) was detected by the the
Suzaku Wide-band All-sky Monitor (WAM) which covers an energy range of
50 keV - 5 MeV at 21:35:31 UT (=T0).

The observed light curve shows a single peak with a duration (T90) of
about 45 seconds.
The fluence in 100 - 1000 keV was 4.26 (+0.84/-2.27) x 10^-6 erg/cm^2.
The 1-s peak flux measured from T0+2 s was
0.73 (+0.26/-0.55) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-5 s to
T0+5 s is well fitted by a single power-law with a photon index of
2.13 (+0.28/-0.36) (chi^2/d.o.f = 12.4/14).

All the quoted errors are at statistical 90% confidence level, in which
the systematic uncertainties are not included.

The light curves for this burst will be available at:

http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB/grb/untrig/grb_table.html