GRB 191024A

S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), K. L. Page (U Leicester)
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 191024A (trigger #931242)
(Page et al., GCN Circ. 26063
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 ).  The BAT ground-calculated position is
RA, Dec = 10.129, -67.138 deg which is
   RA(J2000)  =  00h 40m 30.9s
   Dec(J2000) = -67d 08' 17.1"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 90%.

The mask-weighted light curve shows a single-pulsed structure that starts
and peaks at ~T0, and ends at ~T+8 s. T90 (15-350 keV) is 7.08 +- 0.98 sec
(estimated error including systematics).

The time-averaged spectrum from T-0.96 to T+7.45 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.78 +- 0.14.  The fluence in the 15-150 keV band is 4.7 +- 0.4 x 10^-7
erg/cm2.
The 1-sec peak photon flux measured from T-0.31 sec in the 15-150 keV band
is 1.6 +- 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/931242/BA/

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 191024A 833 s after the BAT trigger
(Page et al., GCN Circ. 26063
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 ).
No optical afterglow consistent with the XRT position (Beardmore et al., GCN Circ. 26064
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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           833          982          147         >21.2
white              833        13531          360         >22.0
v                  989         6893          274         >19.9
b                 1087        13389         1043         >21.6
u                 1062        19531          716         >21.3
w1                1038        19072         1160         >21.1
m2                6898         7098          197         >20.2
w2                1137         1506           39         >19.7

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).

R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:

We observed Swift GRB 191024A (Palmer et al., GCN 26063
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 ) with the LCO 1-m Sinistro instrument at Las Cumbres, Chile site, on October 24, from 05:18 to 05:23 UT (corresponding to 0.13 to 0.22 hours from the GRB trigger time) with Bessel R filter.

We performed a series of 2x120s exposures in R-band. We do not detect any sources in the Swift 90% confidence region (Evans et al., GCN 26064
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 ).  Using the USNO-B.1 catalog as reference, we obtain the following 3-sigma upper limit:


R > 17.08

These observations were possible thanks to the USVI NASA-EPSCoR Research Infrastructure Development (RID) grant NNX16AL44A.

A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), A. Tohuvavohu (U.
Toronto), J.A. Kennea (PSU), B. Sbarufatti (PSU), J.P. Osborne (U.
Leicester), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB)
and K.L. Page report on behalf of the Swift-XRT team:

We have analysed 6.6 ks of XRT data for GRB 191024A (Page et al. GCN
Circ. 26063
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 ), from 837 s to 31.5 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. 26064
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 ).

The light curve can be modelled with a power-law decay with a decay
index of alpha=0.87 (+0.22, -0.18).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.8 (+0.7, -0.6). The
best-fitting absorption column is  3.2 (+4.0, -2.6) x 10^21 cm^-2, in
excess of the Galactic value of 2.7 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 4.1 x 10^-11 (5.7 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     3.2 (+4.0, -2.6) x 10^21 cm^-2
Galactic foreground: 2.7 x 10^20 cm^-2
Excess significance: 1.8 sigma
Photon index:	     1.8 (+0.7, -0.6)

If the light curve continues to decay with a power-law decay index of
0.87, the count rate at T+24 hours will be 1.4 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.9 x
10^-14 (8.1 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/00931242.

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

D. Xu (NAOC), J.T. Palmerio (CNRS - Obs. de Paris/GEPI), D. B. Malesani 
(DTU space), K. E. Heintz (Univ. of Iceland), N. R. Tanvir (Univ. 
Leicester), J. P. U. Fynbo (DAWN/NBI), A. J. Levan (Radboud Univ.), G. 
Pugliese (Univ. Amsterdam), C. Kouveliotou (GWU, APSIS), report on 
behalf of the Stargate collaboration:

We observed the field of GRB 191024A (Page et al., GCN 26063
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 ) using the 
ESO VLT UT2 (Kueyen) equipped with the X-shooter camera. Observations 
started at 06:14:13 UT on 2019-10-14 (i.e., 1.523 hr after the BAT 
trigger) and 3x40 s, 3x30 s , 3x60 s frames were obtained in the Sloan 
g- / r- / z- bands, respectively.

No optical source is detected in our stacked image within the enhanced 
XRT error circle (Beardmore et al., GCN 26064
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 ), down to a limiting 
magnitude of r ~ 24.3 AB mag.

However, there exist two sources just outside and south of the XRT error 
circle in all the stacked g-, r-, and z-band images. Their coordinates 
and magnitudes are as follows

S1
R.A.(J2000) = 0:40:27.360
Dec.(J2000) = -67:08:44.800
Distance from the XRT center: 2.8"
m(r) ~ 24.1 AB mag

S2
R.A.(J2000) = 00:40:27.480
Dec.(J2000) = -67:08:45.800
Distance from the XRT center: 3.6"
m(r) ~ 23.7 AB mag

Due to small FOV, the magnitudes are calculated using only one DSS-2 
reference star at R.A. (J2000) = 00:40:29.68 and Dec. (J2000) = 
-67:08:43.99 with R1=19.68.  And due to only one epoch of photometry, it 
is not clear if either of the two sources is related to the burst. 
Further observations are required to check for variability.

We acknowledge excellent support from the ESO observing staff in 
Paranal, in particular Trystyn Berg and Marcela Espinoza.

[GCN OPS NOTE(24oct19): Per author's request, "Marcela Espinoza"
was added to the last sentence.]

J. Bolmer (MPE Garching), and P. Schady (Univ. of Bath),  report:

We observed the field of GRB 191024A (Swift trigger 931242; Page et al., GCN #26063
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 )
simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted
at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile).

Observations started at 04:45:40 UT on 24th October, 3 minutes after the GRB trigger.
They were performed at an average seeing of 1.2" and at an average airmass of 1.4.

We do not detect a source at the enhanced position of the Swift-XRT afterglow
(Beardmore et al., GCN #26064
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 ) ��� down to the following 3-sigma limits (all AB magnitude) ��� 
in the stacked images of observations taken between 168 and 5906 seconds post trigger
(total integration time of 95 min).

g' > 25.5 mag
r' > 25.6 mag
i' > 24.8 mag
z' > 23.4 mag
J > 21.9 mag
H > 21.4 mag
K > 20.2 mag


Given limits are calibrated against Sky-Mapper and 2MASS field stars and are not
corrected for the Galactic foreground extinction corresponding to a reddening of
E_(B-V)= 0.01 in the direction of the burst (Schlafly & Finkbeiner 2011).

V. Lipunov, E. Gorbovskoy, V.Kornilov, F.Balakin,N.Tyurina,P.Balanutsa,A.Kuznetsov, V.Vladimirov, D. Vlasenko, I.Gorbunov,
D.Zimnukhov,V.Senik, T.Pogrosheva, K.Pozdnyakov,A.Chasovnikov, V.Topolev, D.Kuvshinov(Lomonosov Moscow State University, SAI,Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile(Observatorio Astronomico FelixAguilar OAFA),
H.Levato(Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE),
R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias),
D. Buckley(South African Astronomical Observatory),
O.A. Gres, N.M. Budnev, O.Ershova(Irkutsk State University, API),
A. Tlatov, D. Dormidontov(Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich, Yu. Sergienko(Blagoveschensk Educational State University)

MASTER-OAFA 
(MASTER Global Robotic Net http://observ.pereplet.ru, Lipunov et al.,2010,Advances in Astronomy, vol.2010, 30L)
located in Argentina (OAFA observatory of San Juan National University) 
was pointed to the SWIFT GRB191024A
(Page et al.GCN #26063, Beardmore et al. GCN 26064
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  trigger No 931242, XRT R.A.Dec(2000)=00h 40m 27.53s -67d 08' 42.2")
errorbox  37 sec after trigger time at 2019-10-24 04:43:29 UT,
with upper limit up to  14.4 on 10s images (18.2 mag on 1800s sum)
There is no OT on first images.

The observations began at zenith distance = 38 deg. The sun  altitude  was -47.1 deg.

The galactic latitude b = -60 deg., longitude l = 98 deg.

Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/event.php?id=1175693

We obtained the following upper limits:

Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

       42 |         MASTER-OAFA |   C |    10 | 14.4 |
       83 |         MASTER-OAFA |   C |    10 | 13.8 |
      131 |         MASTER-OAFA |   C |    20 | 14.5 |
      187 |         MASTER-OAFA |   C |    30 | 14.6 |
      237 |         MASTER-OAFA |   C |   130 | 15.3 |  Coadd
      253 |         MASTER-OAFA |   C |    40 | 14.3 |
      335 |         MASTER-OAFA |   C |    60 | 14.9 |
      436 |         MASTER-OAFA |   C |    80 | 15.6 |
      546 |         MASTER-OAFA |   C |   300 | 16.1 |  Coadd
      558 |         MASTER-OAFA |   C |   100 | 15.2 |
      700 |         MASTER-OAFA |   C |   120 | 15.4 |
      866 |         MASTER-OAFA |   C |   150 | 16.3 |
     1873 |         MASTER-OAFA |   C |  1800 | 17.7 |  Coadd
     6099 |         MASTER-OAFA |   C |  1800 | 18.2 |  Coadd


Reduction will be continued.
The message may be cited.

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

Using 839 s of XRT Photon Counting mode data and 1 UVOT
images for GRB 191024A, 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 = 10.11473, -67.14506 which is equivalent
to:

RA (J2000): 00h 40m 27.53s
Dec (J2000): -67d 08' 42.2"

with an uncertainty of 2.4 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.

K. L. Page (U Leicester), J.D. Gropp (PSU), N. J. Klingler (PSU),
D. M. Palmer (LANL) and A. Tohuvavohu (Toronto) report on behalf of
the Neil Gehrels Swift Observatory Team:

At 04:42:52 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 191024A (trigger=931242).  Swift slewed to the burst after
a delay to clear the Earth limb observing constraint. 
The BAT on-board calculated location is 
RA, Dec 10.147, -67.139 which is 
   RA(J2000) = 00h 40m 35s
   Dec(J2000) = -67d 08' 21"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The first 8 seconds of the BAT light curve 
showed a FRED structure structure with an extrapolated duration of 
about 12 sec.  (Further light curve data will not be available until
the full dataset is downlinked to the ground.)  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 04:56:41.7 UT, 829.1 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 10.11387, -67.14323 which is equivalent
to:
   RA(J2000)  = 00h 40m 27.33s
   Dec(J2000) = -67d 08' 35.6"
with an uncertainty of 4.5 arcseconds (radius, 90% containment). This
location is 48 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 832 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
0.02. 

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/)