GRB 151027A
GCN Circular 18635
Subject
GRB 151027A: Maidanak optical observations
Date
2015-11-22T21:48:09Z (11 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
A. Pozanenko (IKI), E. Mazaeva (IKI), A. Volnova (IKI), O. Burhonov
(UBAI) report on behalf of larger GRB follow-up collaboration:
We observed the Swift GRB 151027A (Maselli et al., GCN 18478) with
AZT-22 telescope of Maidanak observatory equipped with SNUCAM in R
filter. We obtained several images in R-filter on Oct., 30, Nov., 6 and
Nov., 9 under mean FWHM of about 0.9". The afterglow (Maselli et al.,
GCN 18478; Zheng and Filippenko, GCN 18479) is clearly detected in each
epoch. The afterglow is well separated from nearby source (Dichiara et
al.GCN 18510; Mazaeva et al., GCN 18559).
Preliminary photometry of the afterglow is following
Date UT start t-T0 Filter Exp. OT Err.
(mid, days) (s)
2015-11-06 15:04:07 10.474 R 10*300 23.30 0.24
2015-11-09 14:06:04 13.443 R 10*300 23.33 0.20
The photometry is based on nearby USNO-B1.0 stars
USNO-B.1_id R2
1513-0237223 16.66
1513-0237251 16.81
1513-0237270 16.78
A preliminary light curve of the afterglow can be found in
http://grb.rssi.ru/GRB151027A/GRB151027A_lc.png
At this time it is unclear what is a reason of flattening of the light
curve at 11-13 days. It might be SN signature or it is continuing bumps
of the light curve previously seen at least on ~ 1.3 days and ~3 days.
GCN Circular 18620
Subject
610 MHz detection of GRB 151027A with the GMRT
Date
2015-11-19T10:52:47Z (11 years ago)
From
Poonam Chandra at TIFR <poonam@ncra.tifr.res.in>
Poonam Chandra (NCRA-TIFR) and A. J. Nayana (NCRA-TIFR) reports:
We carried out Giant Metrewave Radio Telescope (GMRT) observations of
GRB 151027A (GCN Circ. 18478) at 610 MHz band on 2015 Nov 19.19 UT. We
detect the radio afterglow of the GRB in the Swift error circle (GCN
Circ. 18482).
The 610 MHz band flux density of the afterglow is 522+/-94 uJy. Map rms is
56 uJy.
Further observations are planned. We thank GMRT staff for making these
observations possible.
--
_________________________________________
Poonam Chandra
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research
Pune University Campus, Ganeshkhind
Pune 411007, Maharashtra, INDIA
Phone: +91 20 2571 9290
Fax: +91 20 2569 7257
Email: poonam@ncra.tifr.res.in
Web: www.ncra.tifr.res.in:8081/~poonam/
_________________________________________
GCN Circular 18616
Subject
GRB 151027A: SAO RAS and Mt. Terskol observations
Date
2015-11-18T12:41:05Z (11 years ago)
From
Moskvitin Alexander at SAO RAS <mosk@sao.ru>
A. S. Moskvitin (SAO RAS), I. V. Sokolov (Terskol Branch of INASAN)
report on behalf of larger GRB follow-up team.
We observed the field of GRB 151027A twice: with 2-m Zeiss-2000
+ FLI CCD (Mt. Terskol) and 1-m Zeiss-1000 + EEV 42-40 CCD (SAO RAS)
on November 6 and 12 respectively (T-T0 = 10.5 and 16.5 days).
We have obtained 10x300 and 24x300 sec. frames in R band.
We do not detect the GRB OT (Maselli et al., GCNC #18478)
down to the limiting magnitude R_lim = 22.8 in both stacked images.
As the standard stars we used USNO-B1 objects from GCNCs #18521,
18558 and 18559.
We should note that nearby USNO-B1 source reported by
S. Dichiara et al. (GCNC #18510) and E. Mazaeva et al. (GCNC #18559)
is clearly detected in our images.
GCN Circular 18609
Subject
GRB151027A; Optical observations
Date
2015-11-16T12:16:29Z (11 years ago)
From
G.C. Anupama at IIA,Bangalore <gca@iiap.res.in>
We observed the field of GRB 151027A (Maselli et al., GCN 18478) using
the 2m Himalayan Chandra Telescope of Indian Astronmical Observatory,
Hanle,
India. The GRB field was observed in Bessells R band, during 14:56 UT
to
16:20 UT on 2015-10-27. We obtained 20 frames, each of 150 seconds
exposure time. The optical afterglow of GRB 151027A (e.g., Maselli et
al.,
GCN 18478; Zheng & Filippenko, GCN 18479; Elenin et al., GCN 18480;
Perley & Cenko, GCN 18481) is clearly detected in each image. The
measured magnitudes, calibrated using nearby USNO B1.0 (R2 magnitudes)
stars are listed below.
---------------------------------------------------------------------
Time (UT start) Filter Mag error
14:56 R 16.60 0.06
15:36 R 16.67 0.07
16:20 R 16.86 0.08
-----------------------------------------------------------------------
This message may be cited.
D.K. Sahu and G.C. Anupama (Indian Institute of Astrophysics, Bengaluru)
GCN Circular 18608
Subject
GMRT radio detection of GRB 151027A
Date
2015-11-16T11:43:16Z (11 years ago)
From
Poonam Chandra at TIFR <poonam@ncra.tifr.res.in>
Poonam Chandra (NCRA-TIFR) and A. J. Nayana (NCRA-TIFR) reports:
We carried out Giant Metrewave Radio Telescope (GMRT) observations of
GRB 151027A (GCN Circ. 18478) at 1390 MHz band on 2015 Nov 15.19 UT. We
detect the radio afterglow of the GRB in the Swift error circle (GCN
Circ. 18482).
The 1390 MHz band flux density of the afterglow is 312+/-64 uJy. Map rms is
37 uJy.
Further observations are planned. We thank GMRT staff for making these
observations possible.
--
_________________________________________
Poonam Chandra
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research
Pune University Campus, Ganeshkhind
Pune 411007, Maharashtra, INDIA
Phone: +91 20 2571 9290
Fax: +91 20 2569 7257
Email: poonam@ncra.tifr.res.in
Web: www.ncra.tifr.res.in:8081/~poonam/
_________________________________________
GCN Circular 18575
Subject
GRB 151027A: continued Mondy optical observations
Date
2015-11-10T19:10:04Z (11 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
E. Mazaeva (IKI), E. Klunko (ISTP), A. Volnova (IKI), I. Korobtsev
(ISTP), A. Pozanenko (IKI) report on behalf of larger GRB follow-up
collaboration:
We continue observations (GCN 18559) of the Swift GRB 151027A (Maselli
et al., GCN 18478) with AZT-33IK telescope of Sayan observatory
(Mondy). We obtained images in R-filter on Nov., 4, 5, 7-9. In a
combined image obtained on Nov. 7 we clearly detect a galaxy which
coincide with the object 1513-0237216 of USNO-B1.0 catalog. The object
was also mentioned in GCN 18510 (Dichiara et al.) and GCN 18559 (Mazaeva
et al.)
The finding chart can be found in
http://grb.rssi.ru/GRB151027A/GRB151027A_20151107_AZT33IK_host.png
The afterglow (Maselli et al., GCN 18478; Zheng and Filippenko, GCN
18479) is not well detected. The afterglow might overlap with
North-East wing of the galaxy. The galaxy could be suggested as a host
galaxy of GRB 151027A.
Preliminary photometry of the galaxy is R= 20.60+/-0.04 at November, 7.
The photometry is based on nearby USNO-B1.0 stars referenced in GCN 18559.
GCN Circular 18567
Subject
GRB 151027A: Hankasalmi optical observations
Date
2015-11-08T09:04:54Z (11 years ago)
From
Arto Oksanen at Nyrola Obs., Finland <oksanen@nyrola.jklsirius.fi>
Arto Oksanen (Hankasalmi Obs., Hankasalmi, Finland) reports the
following observations of GRB 151027A (Maselli et al. 2015, GCN Circular
#18478; Zheng et al. 2015, GCN Circular #18479, and many subsequent
Circulars) to the AAVSO High Energy Network:
A. Oksanen observed the location of GRB 151027A using the Hankasalmi
Observatory 0.4-m Richey-Chretien telescope using an SBIG STL-1001E
camera. Time-series images were obtained with both Rc and clear
filters, with fifty 60-second frames obtained in each filter. Clear
filtered images were obtained between 16:27:07 UT and 22:01:23 UT on
2015 October 27, and Rc-filtered images were obtained between 18:59:58
and 21:45.04 UT. Photometry was performed using an ensemble of
comparison stars with APASS photometry available from AAVSO VSP
(www.aavso.org/vsp). The afterglow is detected in both Rc- and
clear-filtered observations, with evidence of fading between the start
and end of the observing run.
Photometry of co-added groups of images yields the following:
Clear filter:
t-t0(d) m(CR) err(CR)
0.5235 16.872 0.030
0.5334 16.816 0.030
0.6531 17.160 0.044
0.6644 17.322 0.047
0.7468 17.575 0.065
Rc filter:
t-t0(d) m(R) err(R)
0.6365 17.257 0.058
0.6848 17.544 0.074
0.7353 17.580 0.118
These magnitudes of GRB 151027A are consistent with other magnitudes
obtained at similar epochs of this burst (e.g. Hentunen et al. GCN
Circular #18503; Sonbas et al. #18518).
GCN Circular 18559
Subject
GRB 151027A: Mondy optical observations
Date
2015-11-04T17:58:29Z (11 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
E. Mazaeva (IKI), A. Volnova (IKI), E. Klunko (ISTP), I. Korobtsev (ISTP),
A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the Swift GRB 151027A (Maselli et al., GCN 18478) with
AZT-33IK telescope of Sayan observatory (Mondy) on several epochs. We
obtained
images in R-filter on Oct., 27-- Nov., 1 . The afterglow (Maselli et al.,
GCN 18478; Zheng and Filippenko, GCN 18479) is clearly detected in each
epoch. Coordinates of the afterglow are (J2000) 18 09 56.66 +61 21 13.0 with
uncertainties of 0.3 arcsec in each coordinate. We also detected the
USNO-B1.0 source mentioned in GCN 18510 (Dichiara et al.) in a position
(J2000) 18 09 56.44 +61 21 10.8 with uncertainties of 0.3 arcsec in each
coordinate.
Preliminary photometry of the afterglow on October-29 -- November, 1 is
following
Date UT start t-T0 Filter Exp. OT Err.
(mid, days) (s)
2015-10-29 13:18:41 2.4082 R 55*60 19.84 0.05
2015-10-30 12:11:18 3.3736 R 78*60 20.32 0.06
2015-10-31 12:47:18 4.3958 R 41*120 21.25 0.07
2015-11-01 12:28:18 5.3694 R 19*120 21.50 0.12
The photometry is based on nearby USNO-B1.0 stars
USNO-B.1_id R2
1513-0237223 16.66
1513-0237170 15.58
1513-0237251 16.81
1513-0237270 16.78
Late time photometry could be influenced by the nearby USNO-B1.0 source.
The overall light curve of our observations as well as photometry reported
in GCNs 18480, 18521,18558 can be found in
http://grb.rssi.ru/GRB151027A/GRB151027A_lc.png
GCN Circular 18558
Subject
GRB 151027A: Mt. Terskol observatory optical observation
Date
2015-11-04T10:08:22Z (11 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
V. Kozlov (IC AMER, NASU), M. Andreev (Terskol Branch of INASAN), E.
Mazaeva (IKI), A. Sergeev (Terskol Branch of INASAN), A. Volnova (IKI), A.
Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of GRB 151027A (Maselli et al., GCN 18478) with
Zeiss-600 telescope of Mt. Terskol observatory in R-filter starting on Oct.
28 (UT) 21:23:11. We obtained several images in R-filter. The afterglow
(Maselli et al., GCN 18478; Zheng and Filippenko, GCN 18479) is clearly
detected in a combined image. The photometry of the combined image is
following
Date UT start t-T0 Filter Exp. OT Err
(mid, days) (s)
2015-10-28 21:23:11 1.7431 R 25*120 19.56 0.12
The photometry is based on nearby USNO-B1.0 stars
USNO-B.1_id R2
1513-0237223 16.66
1513-0237170 15.58
1513-0237251 16.81
1513-0237270 16.78
GCN Circular 18555
Subject
GRB 151027A: the missing GeV component
Date
2015-11-03T18:21:32Z (11 years ago)
From
Remo Rufinni at ICRA <ruffini@icra.it>
R. Ruffini, Y. Aimuratov, U. Barres, R. Belvedere, C.L. Bianco, M. Enderli, M. Kovacevic, R. Moradi, M. Muccino, A. Penacchioni, G.B. Pisani, J.A. Rueda, Y. Wang report:
From its overlapping [1] with GRB 090618, the prototype of binary-driven hypernovae (BdHNe), we can assert that this GRB belongs to the class of long GRBs originating in a binary system composed of a carbon-oxygen core and a companion neutron star (Rueda & Ruffini, 2012; Fryer et al. 2014).
At the redshift of z=0.81 (Perley et al, GCN 18487) the isotropic energy is Eiso ~ 4x10^(52) erg and the rest-frame spectral peak energy is Ep,i ~ 615 keV (Toelge et al., GCN 18492). A SN should appear after 13-15 days in rest-frame, namely between November 19th and November 23rd.
The exceptional feature of GRB 151027A is that, even if it belongs to the BdHN class, there is no high energy emission associated as of today although it was in the Fermi-LAT field of view (Toelge et al., GCN 18492). If confirmed this can be of support to probe the angular distribution of the high energy emission. Additional data in all wavelengths are requested for this most peculiar source.
[1] http://www.icranet.org/documents/GRB151027A.pdf
GCN Circular 18552
Subject
GRB 151027A: Correction to GCN 18519
Date
2015-11-02T19:12:53Z (11 years ago)
From
Zach Cano at U of Iceland <zewcano@gmail.com>
���Z. Cano (U. Iceland) reports on behalf of a larger collaboration:
Upon further investigation, it was discovered that the magnitudes given in
GCN Circ. 18519 are incorrect. The presented photometry was not for the
optical and NIR afterglow of GRB 151027A, but rather the fainter object
that is 3.1 arcsec SW of the afterglow (Dichiara et al. GCN Circ. 18510).
A revised summary of the NOT observations follows:
Filter t-t0 (hr) Mag +- Merr
-----------------------------------------
B 17.94 18.2 +- 0.1
R 18.17 17.9 +- 0.1
I 18.28 17.4 +- 0.1
J 16.92 16.4 +- 0.1
H 17.38 15.5 +- 0.1
K 17.60 15.1 +- 0.1
The optical filters are calibrated to USNO-B1 and the NIR filters to 2MASS,
where a single star that appears in both catalogs was used for the
zeropoint calculation. These magnitudes are not corrected for foreground
extinction.
When these extinguished magnitudes are converted to monochromatic fluxes
(using the zeropoints from Fukugita et al. 1995; Hewett et al. 2006), a
single power-law with an exponent of -0.8 provides a good fit to the
optical-to-NIR spectral energy distribution.
My apologies for the confusion.���
GCN Circular 18539
Subject
GRB 151027A: optical follow-up observations
Date
2015-10-31T06:39:13Z (11 years ago)
From
Patrick Wiggins at Wiggins Obs <paw@digis.net>
P. Wiggins reports:
Observed GRB 151027A with a .35-meter optical telescope at my home observatory, IAU 718, on 2015 October 27 from 0433 to 0732 UTC using a clear filter and obtained the following:
GRB Countpart: 18h 09m 56.71s +61d 21m 12.78s
Reference One: 18h 10m 05.68s +61d 23m 14.97s
Reference Two: 18h 09m 51.53s +61d 22m 48.87s
Julian Date Date Ref. C Ref. K Var. V C-K Differential
Mid Exposure yyyy-mm-dd.ddddd Raw Mag. Raw Mag. Raw Mag. Differ. Mag.
-------------- ---------------- --------- --------- --------- --------- ------------
2457322.689715 2015 10 27.18972 -2.937 -3.111 -1.085 0.174 15.051
2457322.692866 2015 10 27.19287 -2.433 -2.622 -1.355 0.190 14.278
2457322.700101 2015 10 27.20010 -2.732 -2.925 -1.433 0.192 14.499
2457322.703174 2015 10 27.20317 -2.921 -3.112 -1.605 0.191 14.516
2457322.724392 2015 10 27.22439 -2.909 -3.088 -1.391 0.180 14.718
2457322.758285 2015 10 27.25829 -2.949 -3.142 -1.151 0.193 14.998
2457322.786495 2015 10 27.28649 -2.906 -3.085 -0.916 0.180 15.189
2457322.801286 2015 10 27.30129 -2.901 -3.108 -0.722 0.207 15.379
2457322.814370 2015 10 27.31437 -2.879 -3.079 -0.406 0.201 15.673
END
GCN Circular 18537
Subject
GRB 151027A: Continued P60 Monitoring
Date
2015-10-30T14:37:08Z (11 years ago)
From
S. Bradley Cenko at NASA/GSFC <brad.cenko@nasa.gov>
S. B. Cenko (NASA-GSFC) and D. A. Perley (DARK/NBI) report on behalf of a larger collaboration:
We have continued to image the optical afterglow of GRB151027A (Maselli et al., GCN 18478) with the robotic Palomar 60-inch telescope (see Perley et al., GCN 18481). We report the following r�-band photometry, calibrated with respect to nearby point sources from the APASS survey:
t_mid time since burst (d) Magnitude
���������������������������������
2015-10-29T02:14:14 1.93 19.63 +/- 0.04
2015-10-30T02:02:28 2.92 20.48 +/- 0.08
This implies a relatively steep power-law decay index of ~ 1.9 at these times.
Continued observations are planned.
GCN Circular 18533
Subject
GRB 151027A: Optical counterpart detection
Date
2015-10-29T21:34:24Z (11 years ago)
From
Valentyna Golovnya at Main Astro Obs,Kyiv <golov_v@ukr.net>
Yu. Protsyuk (RI NAO), O. Kovalchuk (RI NAO) report:
��
We observed the field of the Swift GRB 151027A (Maselli et al.
GCN 18478) with 0.5-m telescope Mobitel KT-50 of Nikolaev observatory
with Alta-U9000 CCD-camera with R filter in robotic mode
from Oct., 28 (UTC) 20:34:16 till 20:59:59.
We obtained 19 unfiltered images of 60 s exposure and calculated
coordinates and magnitudes of all detected objects in UCAC4 system.
We don't detect any optical counterpart of GRB 151027A (Maselli et al.
GCN 18478; Zheng and Filippenko, GCN 18479) in coordinates near (J2000)
18 09 56 +61 21 12 up to ~17.2- 17.5 m .
After that we filtered all images and detected optical
counterpart��in 6 images��in coordinates (J2000)
18 09 56.680 (SD=0.s081) +61 21 12.08 (SD=0."63)
with brightness near 18.3m (SD=0.3m)
GCN Circular 18525
Subject
GRB 151027A: MAXI/GSC detection
Date
2015-10-29T11:01:12Z (11 years ago)
From
H. Negoro at Nihon U. <negoro@phys.cst.nihon-u.ac.jp>
T. Masumitsu, H. Negoro, (Nihon U.), N. Kawai (Tokyo Tech), T. Sakamoto (AGU),
S. Ueno, H. Tomida, S. Nakahira, M. Kimura, M. Ishikawa, Y. E. Nakagawa (JAXA),
T. Mihara, M. Sugizaki, M. Serino, M. Shidatsu, J. Sugimoto,
T. Takagi, M. Matsuoka (RIKEN), T. Yoshii, Y. Tachibana (Tokyo Tech),
A. Yoshida, Y. Kawakubo, H. Ohtsuki (AGU), H. Tsunemi, R. Imatani (Osaka U.),
M. Nakajima, K. Tanaka (Nihon U.), Y. Ueda, T. Kawamuro, T. Hori (Kyoto U.),
Y. Tsuboi, S. Kanetou (Chuo U.), M. Yamauchi, D. Itoh (Miyazaki U.),
K. Yamaoka (Nagoya U.), M. Morii (ISM)
report on behalf of the MAXI team:
MAXI/GSC performed scanning observations at the region of
GRB 151027A (Maselli et al. GCN 18478) for 48 sec each
at the centroid time 03:38:56, 1168 s before the Swift trigger, and
05:11:32, 4388 s after the Swift trigger.
No positive 4-10 keV flux was obtained at the former scan transit
with the 3 sigma upper limit of 0.037 photons/cm2/s (~ 31 mCrab).
At the latter scan transit, the 4-10 keV flux was 0.0166 +/- 0.0175
photons/cm2/s (~ 14 +/- 15 mCrab).
The detection is not significant, but the flux is consistent with
the interpolation from the Swift/XRT light curve (V. D'Elica et al. #18509).
GCN Circular 18521
Subject
GRB 151027A: SAO RAS optical observations
Date
2015-10-28T23:18:01Z (11 years ago)
From
Moskvitin Alexander at SAO RAS <mosk@sao.ru>
A. Moskvitin (SAO RAS, Russia), report on behalf of the larger GRB
follow-up team:
The field of the GRB 151027A (Maselli et al., GCNC #18478) was observed
with the Zeiss-1000, 1 meter telescope of SAO RAS on the October, 28.
The observations started 36.3 hours after the trigger.
Two series of 300 sec. images in Rc band: 6 frames (16:13:57--16:56:20 UT)
and 3 frames (17:32:15--17:50:33 UT) were obtained under the tolerable
weather conditions.
The OT is clearly detected in the stacked frames:
# T_mid-T0,h exp,s R_mag
1 36.612 6 x 300 18.7 +/- 0.1
2 37.717 3 x 300 18.9 +/- 0.1
The photometry is based on nearby USNO-B1 stars proposed
by A. Pozanenko (IKI RAS). The observations were provided with the help
of the SAO RAS staff: V. Komarov, O. Spiridonova and R. Uklein.
GCN Circular 18519
Subject
GRB 151027A: NOT optical and NIR observations
Date
2015-10-28T18:13:41Z (11 years ago)
From
Zach Cano at U of Iceland <zewcano@gmail.com>
Z. Cano (U. Iceland), D. Malesani (DARK/NBI), Jussi Harmanen (NOT & U.
Turku), Thomas Reynolds (NOT & U. Turku.), Pere Blay Serrano (IAC/NOT) and
P. Jakobsson (U. Iceland) report on behalf of a larger collaboration:
We observed the field of Swift GRB 151027A (Maselli et al., GCN Circ.
18478) with the Nordic Optical Telescope equipped with the StanCam
(optical) and NOTCam (NIR) imagers, in filters BVRI and JHK, respectively.
Observations started at 20:53 UT on 27 October 2015. The OT (Maselli et
al.) is detected all filters.
A summary of our observations follows:
Filter t-t0 (hr) Mag +- Merr
-----------------------------------------
B 17.94 21.4 +- 0.2
R 18.17 20.6 +- 0.1
I 18.28 19.2 +- 0.1
J 16.92 18.2 +- 0.1
H 17.38 18.3 +- 0.1
K 17.60 17.2 +- 0.2
The optical filters are calibrated to USNO-B1 and the NIR filters to 2MASS,
where a single star that appeared in both catalogs was used for the
zeropoint calculation. These magnitudes are not corrected for foreground
extinction.
When these extinguished magnitudes are converted to monochromatic fluxes
(using the zeropoints from Fukugita et al. 1995; Hewett et al. 2006), a
single power-law with an exponent of -1.25 provides an acceptable fit to
the optical-to-NIR spectral energy distribution.
���
GCN Circular 18518
Subject
GRB 151027A: T100 observations
Date
2015-10-28T17:37:17Z (11 years ago)
From
Eda Sonbas at NASA/GSFC <edasonbas@gmail.com>
E. Sonbas (Adiyaman Univ.), T. Guver (Istanbul Univ.), E. Gogus (Sabanci
Univ.), O. Erece, M. Kocak, S. Eryilmaz, H. Kirbiyik (TUG) report on behalf
of a larger collaboration
We observed the field of Swift GRB 151027A (Maselli et al., GCN#18478) with
the 1.0 meter T100 telescope (Bakirlitepe, TUBITAK National Observatory,
Turkey), starting October, 27, 18:32:21 UT (~ 14.5 hours after the
trigger). Observations were carried out in the R filter. The afterglow is
detected in the R band images with an exposure time of 150 s.
Using USNO-B1 star USNO-B1 1513-0237223 (R.A.=272.49, Dec=+61.37) in the
field, the magnitudes of the OT were estimated as follows;
t-t0 (hr) exp.(s) filt mag err (+/-)
14.56 150 R 16.8 0.06
14.61 150 R 17.2 0.08
Analysis of further observations with the same filter is ongoing.
We thank to TUBITAK National Observatory for a partial support in using
T100 telescope with project number 10CT100-95 and technical support.
GCN Circular 18516
Subject
Konus-Wind observation of GRB 151027A
Date
2015-10-28T14:43:29Z (11 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team, report:
The long-duration GRB 151027A
(Swift-BAT trigger #661775: Maselli et al., GCN Circ. 18478,
Palmer et al., GCN Circ. 18496;
Fermi GBM detection: Toelge et al., GCN Circ. 18492)
triggered Konus-Wind at T0=14304.154 s UT (03:58:24.154).
The burst light curve consists of at least three pulses
with a total duration of ~120 s.
The emission is seen up to ~5 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB151027_T14304/
As observed by Konus-Wind, the burst
had a fluence of 1.42(-0.21,+0.37)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+0.432 s,
of 2.22(-0.61,+0.62)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+131.328 s)
is best fit in the 20 keV - 5 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.44(-0.21,+0.24)
and Ep = 173(-46,+135) keV (chi2 = 78/77 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.0
(chi2 = 77/76 dof)
The spectrum near the maximum count rate
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.96(-0.28,+0.32)
and Ep = 91(-11,+14) keV (chi2 = 56/61 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.7
(chi2 = 56/60 dof)
Assuming the redshift z=0.81 (Perley et al., GCN Circ. 18487)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.27, and Omega_Lambda = 0.73,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~2.4x10^52 erg,
the peak luminosity L_iso is ~7x10^51 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,i, is ~310 keV.
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 18515
Subject
GRB 151027A : Xinglong TNT optical observation
Date
2015-10-28T14:37:57Z (11 years ago)
From
L.P. Xin at NAOC <xlp@bao.ac.cn>
L. P. Xin, X. F. Wang, J. Y. Wei, Y. L. Qiu, J. S. Deng,
J. Wang, X. H. Han and C. Wu on behalf of EAFON report:
We observed GRB 151027A (Maselli et al., GCN 18478)
with Xinglong 0.8-m TNT telescope at 2015-10-27 and 2015-10-28.
The optical afterglow (Maselli et al., GCN 18478; Zheng & Filippenko
GCN 18479; Elenin et al., GCN 18480; Perley & Cenko GCN 18481; Xu et al, 18485;
Zhang et al., GCN 18513) was clearly detected in our multi-band images.
The brightness of the optical afterglow is decayed for about 2.5 mag in R-band
during our observations as shown in follows:
==============================
Date Time(UT) filter mag merr
2015-10-27 11:21:59 R 16.2 0.1
2015-10-28 11:04:00 R 18.7 0.1
==============================
Calibrated by the USNO B1.0 R2 mag
More observations are encouraged.
The message may be cited.
GCN Circular 18513
Subject
GRB 151027A: continued GMG observation
Date
2015-10-28T14:16:34Z (11 years ago)
From
Jirong Mao at Yunnan Obs <jirongmao_obs@ynao.ac.cn>
J. Zhang, J. Mao and J. Bai (YNAO) report:
We observed the field of GRB 151027A (Maselli et al., GCN 18478) with the 2.4-meter optical telescope at Gao-Mei-Gu of Yunnan
Observatories. Observations began at 11:32:30 UT, Oct. 28, 2015, about 31.5 hr after the trigger. We clearly detected the
afterglow of GRB 151027A. The magnitude was estimated as R=18.9 +/- 0.1 mag.
GCN Circular 18510
Subject
GRB 151027A: LCOGT-McDonald afterglow observations
Date
2015-10-28T12:16:09Z (11 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
S. Dichiara (U. Ferrara, ICRANet), D. Kopac (U. Ljubljana), C. Guidorzi
(U. Ferrara), S. Kobayashi (LJMU), A. Gomboc (U. Ljubljana) on behalf of
a larger collaboration report:
The 1-m LCOGT McDonald observatory began observing Swift GRB 151027A
(Maselli et al. GCN 18478) on October 28, 01:29:27 UT (0.90 days after
the burst trigger) with SDSS R and I filters. We clearly detect the
optical afterglow (Maselli et al.; Zheng & Filippenko GCN 18479; Elenin
et al. GCN 18480; Perley & Cenko GCN 18481; Xu et al. GCN 18485) with
the following magnitudes:
Mid Time Exposure Filter Magnitude
(days) (s)
-------------------------------------------------------
0.90 5x120 R 16.87 +- 0.04
0.91 6x120 I 17.26 +- 0.05
-------------------------------------------------------
Calibration is done against nearby USNOB-1 star RA(J2000)=18:09:53.742,
DEC(J2000)=+61:20:57.27, assuming R2=17.21 mag and I=17.17 mag. We note
the presence of another USNOB-1 object at RA(J2000)=18:09:56.489,
DEC(J2000)=+61:21:10.64, lying at 3.1 arcsec from the GRB afterglow.
GCN Circular 18508
Subject
GRB 151027A: VLA detection
Date
2015-10-28T08:47:38Z (11 years ago)
From
Tanmoy Laskar at UC Berkeley <tanmoylaskar@gmail.com>
T. Laskar (NRAO / UC Berkeley), K. Alexander, and E. Berger (Harvard)
report on behalf of a larger collaboration:
"We observed GRB 151027A (Maselli et al.; GCN 18478) at multiple
frequencies with the VLA beginning on 2015 October 27.95 UT (0.78 days
after the burst). At a mean frequency of 21.8 GHz, we detect a bright radio
source with a preliminary flux density of ~ 1.7 mJy at
RA = 18:09:56.691 +/- 0.001
Dec = 61:21:13.03 +/- 0.02
consistent with the enhanced Swift/XRT position (Goad et al.; GCN 18482)
and the optical position (Maselli et al.; GCN 18478, Zheng et al.; GCN
18479, Hentunen et al.; GCN 18503). Follow-up observations are planned. We
thank the VLA staff for rapidly scheduling these observations."
GCN Circular 18503
Subject
GRB 151027A: THO optical observations
Date
2015-10-28T02:54:58Z (11 years ago)
From
Veli-Pekka Hentunen at Taurus Hill Obs,A95 <veli-pekka.hentunen@kassiopeia.net>
Veli-Pekka Hentunen, Markku Nissinen and Tuomo Salmi (Taurus Hill
Observatory, Varkaus, Finland) report:
We have detected GRB 151027A optical afterglow at Taurus Hill Observatory
(A95) using Meade 16" ACF 0.40-m/8.0 telescope and SBIG ST-8XME CCD.
The observations were started at 2015-10-27 17:11:39 (UT). Eight photometric
R filter and eight photometric V filter images with 300 sec exposure time were
taken.
The afterglow was detected at the following position RA 18:09:56.72 and
DEC +61:21:13.2.
The following magnitudes were obtained from the observations using
NOMAD1 1512-0243178 (R=13.200 and V=13.670) as a comparison star:
Tmid(h)+T0 Filter Exp. time Mag Mag. Err.
13.393 R 4x300s 17.06 0.12
13.747 V 4x300s 17.56 0.25
14.103 R 4x300s 17.06 0.09
14.457 V 4x300s 17.49 0.10
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
GCN Circular 18502
Subject
GRB 151027A: UVOT Observations
Date
2015-10-28T01:04:14Z (11 years ago)
From
Mike Siegel at PSU/Swift MOC <siegel@swift.psu.edu>
B. G. Balzer (PSU), M. H. Siegel (PSU) and A. Maselli (INAF-IASFPA)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 151027A
96 s after the BAT trigger (Maselli et al., GCN Circ. 18478). We confirm
the source initially reported by Maselli et al. (GCN Circ. 18478) and
since observed by numerous ground-based observatories (Zheng and Filippenko,
GCN Circ. 18479; Elenin et al., GCN Circ. 18480; Perley and Cenko, GCN Circ.
18481; Xu et al., GCN Circ. 18485; Yano et al., GCN Circ. 18491; Wren et al.,
GCN Circ. 18495). We report a position of:
RA(J2000) = +18h 09m 57.26s
Dec(J2000) = +61d 21' 05.4"
The light curve shows complex behavior, with marginal evidence of brightening
after the initial finding chart, then fading with a decay slope of 0.6-0.8 over
the first orbit. The second orbit magnitudes are consistent with no fading
from those measured at the end of the first orbit while the third orbit
shows significant fading.
Preliminary detections using the UVOT photometric system (Breeveld et al. 2011,
AIP Conf. Proc. 1358, 373) for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
white (fc) 95 245 147 14.52+-0.02
white 589 609 19 14.44+-0.04
white 762 782 19 14.71+-0.04
white 858 1008 147 14.81+-0.02
white 1161 1354 38 15.07+-0.04
white 1510 1529 19 15.23+-0.04
white 6449 6649 197 15.28+-0.01
white 23966 24662 677 17.14+-0.01
v 639 1579 116 15.12+-0.04
b 564 1505 97 15.37+-0.03
u 308 1479 323 14.00+-0.03
w1 688 1455 77 14.71+-0.05
m2 663 1598 88 14.98+-0.06
w2 615 1555 116 15.12+-0.05
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 18496
Subject
GRB 151027A: Swift-BAT refined analysis
Date
2015-10-27T18:51:53Z (11 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
D. M. Palmer (LANL), 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), A. Maselli (INAF-IASFPA), 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 151027A (trigger #661775)
(Maselli et al., GCN Circ. 18478). The BAT ground-calculated position is
RA, Dec = 272.498, 61.361 deg which is
RA(J2000) = 18h 09m 59.6s
Dec(J2000) = +61d 21' 39.6"
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 18%.
The mask-weighted light curve shows a complex structure with roughly two main
pulses. The first pulse starts at ~T0, peaks at ~T+1 s, and ends at ~T+5 s. The
second pulse starts at ~T+90 s, peaks at ~T+110 s, and ends at ~T+170 s.
T90 (15-350 keV) is 129.69 +- 5.55 sec (estimated error including systematics).
The time-averaged spectrum from T-0.74 to T+164.70 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.72 +- 0.05. The fluence in the 15-150 keV band is 7.8 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.20 sec in the 15-150 keV band
is 6.8 +- 0.6 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/661775/BA/
GCN Circular 18495
Subject
GRB 151027A: Early RAPTOR Observations
Date
2015-10-27T18:16:09Z (11 years ago)
From
James Wren at LANL <jwren@lanl.gov>
J. Wren, W.T. Vestrand, P. Wozniak, and H. Davis,
of Los Alamos National Laboratory report:
The RAPTOR network of robotic optical telescopes made follow-up observations
of Swift trigger 661775 (Maselli et al., GCN 18478). Our narrow-field
instruments in Los Alamos, NM USA, began imaging at 03:58:48.01 UT (23.86 s
after the BAT trigger time). From the first frame we detected a bright optical
counterpart at the location reported by UVOT. Starting with a magnitude of R~13.7
the RAPTOR telescopes measured a complex, fading lightcurve with seveal
re-brightening intervals.
GCN Circular 18493
Subject
GRB 151027A: GMG observation
Date
2015-10-27T16:43:32Z (11 years ago)
From
Jirong Mao at Yunnan Obs <jirongmao_obs@ynao.ac.cn>
J. Zhang, J. Mao and J. Bai (YNAO) report:
We observed the field of GRB 151027A (Maselli et al., GCN 18478) with the 2.4-meter optical telescope at Gao-Mei-Gu of Yunnan Observatories. Observations began at 11:34:08 UT, Oct 27, 2015, about 7.5 hr after the trigger. We obtained a low S/N spectrum. The feature of absorption line identified as MgII by Perley et al. (GCN 18487) is clearly shown, and redshift is 0.81. However, we noticed that some possible absorption lines might be identified as OVI and NaID, indicating a redshift of 0.33. We cannot have confirmation due to the low S/N of the spectrum. We also performed multi-band photometry and we obtained R~16.9 mag.
Further analysis is ongoing.
GCN Circular 18492
Subject
GRB 151027A: Fermi GBM observation
Date
2015-10-27T16:31:56Z (11 years ago)
From
Hoi-Fung Yu at MPE <sptfung@mpe.mpg.de>
Kilian Toelge, Hoi-Fung Yu (both MPE), and Charles A. Meegan (USRA)
report on behalf of the Fermi GBM Team:
"At 03:58:24.03 UT on 27 Oct 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 151027A (trigger 467611108 / 151027166),
which was also detected by the Swift (Maselli et al. 2015, GCN 18478)
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 10 degrees.
This burst was also independently detected by INTEGRAL SPI-ACS.
The GBM light curve consists of three pulses
with a duration (T90) of about 124 s (50-300 keV).
The time-averaged spectrum from T0-2.048 s to T0+133.120 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.41 +/- 0.04 and
the cutoff energy, parameterized as Epeak, is 340 +/- 63 keV.
The event fluence (10-1000 keV) in this time interval is
(1.94 +/- 0.09)E-05 erg/cm^2. The 1.024-sec peak photon flux measured
starting from T0+0.3840 s in the 10-1000 keV band
is 11.37 +/- 0.34 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 18491
Subject
GRB 151027A: MITSuME Akeno Optical observation
Date
2015-10-27T16:23:13Z (11 years ago)
From
Taketoshi Yoshii at Tokyo Tech <yoshii.t.ac@m.titech.ac.jp>
Y. Yano, T. Yoshii, Y. Saito, Y. Tachibana, H. Ohuchi,
S. Kurita, Y. Ono, T. Fujiwara, S. Harita, Y. Muraki, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We observed the field of GRB 151027A (A. Maselli et al., GCN Circular #18478) with the
optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm
telescope of Akeno Observatory, Yamanashi, Japan.
The observation started on 2015-10-27 09:13:52 UT ( 5.25 h after the burst).
We detected the previously reported optical afterglow of GRB 151027A
(WeiKang Zheng et al., GCN Circular #18479) in the g',Rc and Ic band.
The measured magnitudes are listed below.
T0+[sec] MID-UT T-EXP[sec] g' Rc Ic
------------------------------------------------------------------------------------------------------------------
18928 09:34:24 2220 16.72+/-0.06 15.62+/-0.05 16.00+/-0.04
------------------------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
We used GSC2.3 catalog for flux calibration.
GCN Circular 18490
Subject
GRB 151027A: Swift-XRT refined Analysis
Date
2015-10-27T16:16:03Z (11 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
K.L. Page (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A.
D'ai (INAF-IASFPA), T.G.R. Roegiers (PSU), L.M. McCauley (PSU), J.A.
Kennea (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester)
and A. Maselli report on behalf of the Swift-XRT team:
We have analysed 6.0 ks of XRT data for GRB 151027A (Maselli et al. GCN
Circ. 18478), from 80 s to 18.9 ks after the BAT trigger. The data
comprise 1.6 ks in Windowed Timing (WT) mode (the first 5 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 Goad et al.
(GCN Circ. 18482).
The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=4.1 (+1.1, -1.0). At T+208 s the decay
flattens to an alpha of 1.46 (+0.10, -0.14). The light curve breaks
again at T+537 s to a decay with alpha=0.04 (+0.06, -0.09), and again
at T+2494 s s to alpha=1.11 (+0.15, -0.26), before a final break at
T+11.6 ks s after which the decay index is 2.01 (+0.26, -0.25).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.851 (+0.024, -0.023). The
best-fitting absorption column is 1.96 (+0.18, -0.17) x 10^21 cm^-2,
at a redshift of 0.81, in addition to the Galactic value of 3.8 x 10^20
cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index
of 1.99 (+/-0.08) and a best-fitting absorption column of 3.3 (+/-0.6)
x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.7 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Galactic foreground: 3.8 x 10^20 cm^-2
Intrinsic column: 3.3 (+/-0.6) x 10^21 cm^-2 at z=0.81
Photon index: 1.99 (+/-0.08)
If the light curve continues to decay with a power-law decay index of
2.01, the count rate at T+24 hours will be 0.035 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.3 x
10^-12 (1.7 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/00661775.
This circular is an official product of the Swift-XRT team.
GCN Circular 18487
Subject
GRB 151027A: Keck/HIRES redshift
Date
2015-10-27T13:57:31Z (11 years ago)
From
Daniel Perley at Caltech <dperley@astro.caltech.edu>
D. A. Perley (DARK/NBI), L. Hillenbrand (Caltech), and J. X. Prochaska
(UCO/Lick) report:
We obtained a 900s spectrum of the optical afterglow of GRB 151027A
(Maselli et al., GCN 18478) with Keck/HIRES starting at UT 06:54 on
2015-10-27. In the preliminary reduction, we identify a series of
strong absorption lines including the MgII doublet at z=0.81. Associated
MgI, FeII, and (likely) FeII* are also present, indicating that this is
the redshift of the GRB. Analysis is ongoing.
GCN Circular 18485
Subject
GRB 151027A: Weihai optical observations
Date
2015-10-27T12:17:48Z (11 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
D. Xu (NAOC/CAS), C.-M. Zhang, C. Cao, S.-M. Hu (SDU) report:
We observed the field of GRB 151027A (Maselli et al., GCN 18478) using
the 1m telescope located at Weihai, Shandong, China. Observations
started at 09:44 UT on 2015-07-27, i.e., 5.77 hr after the burst. We
obtained 5x300s R-band and 5x150s I-band frames.
The afterglow (e.g., Maselli et al., GCN 18478; Zheng & Filippenko, GCN
18479; Elenin et al., GCN 18480; Perley & Cenko, GCN 18481) is clearly
detected in each image, and it has decayed to m(R) = 16.0 +/- 0.1 mag
for the first R-band exposure, calibrated with the nearby USNO B1 stars
(with R2 magnitudes).
GCN Circular 18483
Subject
Tentative redshift for GRB 151027A from Swift-XRT data
Date
2015-10-27T10:03:40Z (11 years ago)
From
Sergio Campana at INAF-OAB <sergio.campana@brera.inaf.it>
S. Campana (INAF-OAB) report on behalf of the Swift Team:
Swift BAT triggered on the early activity of GRB 151027A (Maselli et
al. 2015, GCN 18478). Swift XRT started observing 87 s after the
trigger observing the main event. By using the Swift/XRT spectrum
repository at http://www.swift.ac.uk/xrt_spectra/ (see Evans et al.
2009, MNRAS, 397, 1177) we selected a time interval with an almost
constant hardness ratio, starting at 150 s after the burst onset
and lasting 281 s. We then fit the Window Timing (WT) spectrum with
XSPEC using the model tbabs*ztbabs*pow.
We assume a Galactic column density of 3.75x10^20 cm^-2 (Willingale et
al. 2013, MNRAS, 431, 394) and we allow for a 30% uncertainty in the fit.
We fit the spectrum using C-statistics (C-stat=593.74 with 637 d.o.f.).
In the intrinsic column density vs. redshift plane there is just one
deep minimum
hinting for a redshift z=0.38+/-0.17 (90% confidence level) and an
intrinsic column density N_H(z)=(3.6+/-0.7)x10^21 cm^-2.
The X-ray spectrum is soft with Gamma=2.6, (assuming a cut-off power
law spectrum the allowed redshift range expands to 0.27-1.38).
The contour plot is available at
http://www.brera.inaf.it/utenti/campana/151027.gif
GCN Circular 18482
Subject
GRB 151027A: Enhanced Swift-XRT position
Date
2015-10-27T09:37:18Z (11 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester)
report on behalf of the Swift-XRT team.
Using 1445 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 151027A, 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 = 272.48695, +61.35344 which is equivalent
to:
RA (J2000): 18h 09m 56.87s
Dec (J2000): +61d 21' 12.4"
with an uncertainty of 1.7 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.
GCN Circular 18481
Subject
GRB 151027A: P60 afterglow confirmation and rebrightening
Date
2015-10-27T05:57:03Z (11 years ago)
From
Daniel Perley at Caltech <dperley@astro.caltech.edu>
D. A. Perley (DARK/NBI) and S. B. Cenko (NASA/GSFC) report:
The Palomar 60-inch robotic telescope responded automatically to the
alert for GRB 151027A (Maselli et al., GCN151027A) and began a sequence
of i, r, and z-band imaging at 04:00:49 UT, 145 seconds after the BAT
trigger. We identify a very bright afterglow consistent with the UVOT
and KAIT (Zheng et al., GCN18479) positions in all filters.
The preliminary afterglow light curve shows a slow rise to a peak at
about ~5 minutes after the GRB trigger, then slowly fades by about 1
magnitude between then and approximately 30 minutes after the trigger.
Over the next 20 minutes it then rapidly rebrightens by about 0.7
magnitude. Little or no fading is seen after that point (through to at
least 90 minutes after the trigger.)
Continued monitoring is encouraged, and should remain possible even from
small telescopes for quite some time. High-resolution spectroscopy is
also strongly encouraged.
GCN Circular 18480
Subject
GRB 151027A : ISON-NM early optical detection
Date
2015-10-27T05:47:05Z (11 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
L. Elenin (KIAM), E. Mazaeva (IKI), A. Volnova (IKI), I. Molotov (KIAM),
A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration:
We observed the field of the Swift GRB 151027A (Maselli et al., GCN 18478)
with 0.4-m telescope of ISON-NM observatory in robotic mode starting on
Oct., 27 (UT) 03:59:43 i.e. 79 seconds after burst trigger. We obtained 50
unfiltered images of 30 s exposure. We clearly detect the optical
counterpart of GRB 151027A (Maselli et al., GCN 18478; Zheng and
Filippenko, GCN 18479) in coordinates (J2000) 18 09 56.69 +61 21 13.2. In
the first image we estimated brightness of the optical counterpart as ~14m.
GCN Circular 18479
Subject
GRB 151027A: KAIT optical afterglow confirmation
Date
2015-10-27T04:22:02Z (11 years ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report
on behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRB 151027A (Maselli et al.,
GCN 18478) immediately after receiving the trigger. Observations were
performed with an automatic sequence in the clear (roughly R), V,
and I filters, and the exposure time was 20 s per image.
Inside the XRT error circle we detected an un-cataloged varying
source with coordinates of :
RA = 18:09:56.70 (J2000)
DEC= +61:21:13.01 (J2000)
The object location is consistent with the position reported
from UVOT (Maselli et al., GCN 18478). The object has clear band mag
of ~13.0 at the moment.
Follow-up observations are encouraged.
GCN Circular 18478
Subject
GRB 151027A: Swift detection of a burst with a bright optical afterglow
Date
2015-10-27T04:16:31Z (11 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
A. Maselli (INAF-IASFPA), A. D'Ai (INAF-IASFPA),
A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL),
B. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU),
M. Stamatikos (OSU/NASA/GSFC) and T. N. Ukwatta (LANL) report on
behalf of the Swift Team:
At 03:58:24 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 151027A (trigger=661775). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 272.491, +61.381 which is
RA(J2000) = 18h 09m 58s
Dec(J2000) = +61d 22' 51"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a complex
peaked structure lasting at least 150 seconds. The peak count rate
was ~6000 counts/sec (15-350 keV), at ~110 sec after the trigger.
The XRT began observing the field at 03:59:51.1 UT, 87.0 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 272.4886, 61.3515 which is equivalent to:
RA(J2000) = +18h 09m 57.26s
Dec(J2000) = +61d 21' 05.4"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 106 arcseconds from the BAT onboard position, within the
BAT error circle. No event data are yet available to determine the
column density using X-ray spectroscopy.
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 95 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 18:09:56.68 = 272.48615
DEC(J2000) = +61:21:13.4 = 61.35373
with a 90%-confidence error radius of about 0.61 arc sec. This position is 9.06
arc sec. from the center of the XRT error circle. The estimated magnitude is
14.46 with a 1-sigma error of about 0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.05.
Burst Advocate for this burst is A. Maselli (maselli AT ifc.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.)