16 research outputs found
Prompt, early, and afterglow optical observations of five gamma-ray bursts (GRBs 100901A, 100902A, 100905A, 100906A, and 101020A)
We present results of the prompt, early, and afterglow optical observations
of five gamma-ray bursts, GRBs 100901A, 100902A, 100905A, 100906A, and 101020A,
made with the Mobile Astronomical System of TElescope-Robots in Russia
(MASTER-II net), the 1.5-m telescope of Sierra-Nevada Observatory, and the
2.56-m Nordic Optical Telescope. For two sources, GRB 100901A and GRB 100906A,
we detected optical counterparts and obtained light curves starting before
cessation of gamma-ray emission, at 113 s and 48 s after the trigger,
respectively. Observations of GRB 100906A were conducted with two polarizing
filters. Observations of the other three bursts gave the upper limits on the
optical flux; their properties are briefly discussed. More detailed analysis of
GRB 100901A and GRB 100906A supplemented by Swift data provides the following
results and indicates different origins of the prompt optical radiation in the
two bursts. The light curves patterns and spectral distributions suggest a
common production site of the prompt optical and high-energy emission in GRB
100901A. Results of spectral fits for GRB 100901A in the range from the optical
to X-rays favor power-law energy distributions with similar values of the
optical extinction in the host galaxy. GRB 100906A produced a smoothly peaking
optical light curve suggesting that the prompt optical radiation in this GRB
originated in a front shock. This is supported by a spectral analysis. We have
found that the Amati and Ghirlanda relations are satisfied for GRB 100906A. An
upper limit on the value of the optical extinction on the host of GRB 100906A
is obtained.Comment: 18 pages, 14 figures, 14 tables, 5 machine readable tables; accepted
for publication in MNRA
The MASTER-II network of robotic optical telescopes. First results
The main stages in the creation of the Russian segment of the MASTER network of robotic telescopes is described. This network is designed for studies of the prompt optical emission of gammaray bursts (GRBs; optical emission synchronous with the gamma-ray radiation) and surveys of the sky aimed at discovering uncataloged objects and photometric studies for various programs. The first results obtained by the network, during its construction and immediately after its completion in December 2010, are presented. Eighty-nine alert pointings at GRBs (in most cases, being the first ground telescopes to point at the GRBs) were made from September 2006 through July 2011. The MASTER network holds first place in the world in terms of the total number of first pointings, and currently more than half of first pointings at GRBs by ground telescopes are made by the MASTER network. Photometric light curves of GRB 091020, GRB 091127, GRB 100901A, GRB 100906A, GRB 10925A, GRB 110106A, GRB 110422A, and GRB 110530A are presented. It is especially important that prompt emission was observed for GRB 100901A and GRB 100906A, and thar GRB 091127, GRB 110422A, and GRB 110106A were observed from the first seconds in two polarizations. Very-wide-field cameras carried out synchronous observations of the prompt emission of GRB 081102, GRB 081130B, GRB 090305B, GRB 090320B, GRB 090328, and GRB 090424. Discoveries of Type Ia supernovae are ongoing (among them the brightest supernova in 2009): 2008gy, 2009nr, 2010V, and others. In all, photometry of 387 supernovae has been carried out, 43 of which were either discovered or first observed with MASTER telescopes; more than half of these are Type Ia supernovae. Photometric studies of the open clusters NGC 7129 and NGC 7142 have been conducted, leading to the discovery of 38 variable stars. Sixty-nine optical transients have been discovered. © 2013 Pleiades Publishing, Ltd
A Reverse Shock in GRB 181201A
We present comprehensive multiwavelength radio to X-ray observations of GRB 181201A spanning from â150 s to â163 days after the burst, comprising the first joint ALMA-VLA-GMRT observations of a gamma-ray burst (GRB) afterglow. The radio and millimeter-band data reveal a distinct signature at â3.9 days, which we interpret as reverse-shock (RS) emission. Our observations present the first time that a single radio-frequency spectral energy distribution can be decomposed directly into RS and forward shock (FS) components. We perform detailed modeling of the full multiwavelength data set, using Markov Chain Monte Carlo sampling to construct the joint posterior density function of the underlying physical parameters describing the RS and FS synchrotron emission. We uncover and account for all discovered degeneracies in the model parameters. The joint RS-FS modeling reveals a weakly magnetized (Ï â 3 Ă 10-3), mildly relativistic RS, from which we derive an initial bulk Lorentz factor of Î0 â 103 for the GRB jet. Our results support the hypothesis that low-density environments are conducive to the observability of RS emission. We compare our observations to other events with strong RS detections and find a likely observational bias selecting for longer lasting, nonrelativistic RSs. We present and begin to address new challenges in modeling posed by the present generation of comprehensive, multifrequency data sets
Multi-messenger observations of a binary neutron star merger
On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transientâs position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta
Đ Đ°ĐœĐœĐžĐ” ĐŸĐżŃĐžŃĐ”ŃĐșОД ĐœĐ°Đ±Đ»ŃĐŽĐ”ĐœĐžŃ ŃĐ”ĐŒĐž ĐłĐ°ĐŒĐŒĐ°-ĐČŃплДŃĐșĐŸĐČ ĐČ ŃŃĐ°ĐČĐœĐ”ĐœĐžĐž Ń ĐžŃ ĐłĐ°ĐŒĐŒĐ°-ŃĐ”ĐœŃĐłĐ”ĐœĐŸĐČŃĐșĐžĐŒĐž Ń Đ°ŃĐ°ĐșŃĐ”ŃĐžŃŃĐžĐșĐ°ĐŒĐž ĐœĐ° ĐłĐ»ĐŸĐ±Đ°Đ»ŃĐœĐŸĐč ŃĐ”ŃĐž ŃДлДŃĐșĐŸĐżĐŸĐČ-ŃĐŸĐ±ĐŸŃĐŸĐČ ĐĐĐŁ ĐĐĐĄĐąĐĐ
Seven gamma-ray bursts â GRB 130907A, GRB 140311B, GRB 140129B, GRB 160227A, GRB 120404A, GRB 110801A, and GRB 120811C were observed by the MSU MASTER (Mobile Astronomical System of TElescope Robots) Global Network. Full automation of the observations provided for obtaining unique data on the properties of early optical radiation accompanying gamma-ray bursts. The data are compared in the optical (MASTER), X-ray (SWIFT X-ray Telescope, XRT) and gamma (SWIFT Burst Alert Telescope, BAT) ranges. Based on the data obtained, two groups are identified, and their radiation mechanisms are revealed. The effect of gamma-ray bursts on the biosphere of the Earth is determined, and the estimates and the scale of such an effect are considered.Đ ŃŃĐ°ŃŃĐ” ĐżŃДЎŃŃĐ°ĐČĐ»Đ”ĐœŃ ŃДзŃĐ»ŃŃĐ°ŃŃ ĐœĐ°Đ±Đ»ŃĐŽĐ”ĐœĐžĐč ŃĐ”ĐŒĐž ĐłĐ°ĐŒĐŒĐ°-ĐČŃплДŃĐșĐŸĐČ â GRB 130907A, GRB 140311B, GRB 140129B, GRB 160227A, GRB 120404A, GRB 110801A, GRB 120811C, ĐżĐŸĐ»ŃŃĐ”ĐœĐœŃĐ” ĐœĐ° ŃДлДŃĐșĐŸĐżĐ°Ń
-ŃĐŸĐ±ĐŸŃĐ°Ń
ĐłĐ»ĐŸĐ±Đ°Đ»ŃĐœĐŸĐč ŃĐ”ŃĐž ĐĐĐŁ «ĐĐĐĄĐąĐР». ĐĐŸĐ»ĐœĐ°Ń Đ°ĐČŃĐŸĐŒĐ°ŃОзаŃĐžŃ ĐœĐ°Đ±Đ»ŃĐŽĐ”ĐœĐžĐč ĐżĐŸĐ·ĐČĐŸĐ»ĐžĐ»Đ° ĐżĐŸĐ»ŃŃĐžŃŃ ŃĐœĐžĐșĐ°Đ»ŃĐœŃĐ” ĐŽĐ°ĐœĐœŃĐ” ĐŸ ŃĐČĐŸĐčŃŃĐČĐ°Ń
ŃĐ°ĐœĐœĐ”ĐłĐŸ ĐŸĐżŃĐžŃĐ”ŃĐșĐŸĐłĐŸ ОзлŃŃĐ”ĐœĐžŃ, ŃĐŸĐżŃĐŸĐČĐŸĐ¶ĐŽĐ°ĐČŃĐ”ĐłĐŸ ĐłĐ°ĐŒĐŒĐ°-ĐČŃплДŃĐșĐž. ĐŃĐżĐŸĐ»ĐœĐ”ĐœĐŸ ŃŃĐ°ĐČĐœĐ”ĐœĐžĐ” ĐŽĐ°ĐœĐœŃŃ
ĐČ ĐŸĐżŃĐžŃĐ”ŃĐșĐŸĐŒ (ĐĐĐĄĐąĐĐ ), ŃĐ”ĐœŃĐłĐ”ĐœĐŸĐČŃĐșĐŸĐŒ (SWIFTX-rayTelescope (XRT)) Đž ĐłĐ°ĐŒĐŒĐ° (SWIFTBurstAlertTelescope (BAT)) ĐŽĐžĐ°ĐżĐ°Đ·ĐŸĐœĐ°Ń
. ĐĐ° ĐŸŃĐœĐŸĐČĐ°ĐœĐžĐž ĐżĐŸĐ»ŃŃĐ”ĐœĐœŃŃ
ĐŽĐ°ĐœĐœŃŃ
ĐČŃĐŽĐ”Đ»Đ”ĐœŃ ĐŽĐČĐ” ĐłŃŃппŃ, ĐŽĐ»Ń ĐșĐŸŃĐŸŃŃŃ
ĐŸĐżŃĐ”ĐŽĐ”Đ»Đ”Đœ ĐŒĐ”Ń
Đ°ĐœĐžĐ·ĐŒ ОзлŃŃĐ”ĐœĐžŃ. йаĐșжД ĐŸĐżŃĐ”ĐŽĐ”Đ»Đ”ĐœĐŸ ĐČĐŸĐ·ĐŽĐ”ĐčŃŃĐČОД ĐłĐ°ĐŒĐŒĐ°-ĐČŃплДŃĐșĐŸĐČ ĐœĐ° Đ±ĐžĐŸŃŃĐ”ŃŃ ĐĐ”ĐŒĐ»Đž Đž ŃĐ°ŃŃĐŒĐŸŃŃĐ”ĐœŃ ĐŸŃĐ”ĐœĐșĐž Đž ĐŒĐ°ŃŃŃаб ŃĐ°ĐșĐŸĐłĐŸ ĐČлОŃĐœĐžŃ
Multi-messenger Observations of a Binary Neutron Star Merger
On 2017 August 17 a binary neutron star coalescence candidate (later
designated GW170817) with merger time 12:41:04 UTC was observed through
gravitational waves by the Advanced LIGO and Advanced Virgo detectors.
The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray
burst (GRB 170817A) with a time delay of ⌠1.7 {{s}} with respect to
the merger time. From the gravitational-wave signal, the source was
initially localized to a sky region of 31 deg2 at a
luminosity distance of {40}-8+8 Mpc and with
component masses consistent with neutron stars. The component masses
were later measured to be in the range 0.86 to 2.26 {M}ÈŻ
. An extensive observing campaign was launched across the
electromagnetic spectrum leading to the discovery of a bright optical
transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC
4993 (at ⌠40 {{Mpc}}) less than 11 hours after the merger by the
One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The
optical transient was independently detected by multiple teams within an
hour. Subsequent observations targeted the object and its environment.
Early ultraviolet observations revealed a blue transient that faded
within 48 hours. Optical and infrared observations showed a redward
evolution over âŒ10 days. Following early non-detections, X-ray and
radio emission were discovered at the transientâs position ⌠9
and ⌠16 days, respectively, after the merger. Both the X-ray and
radio emission likely arise from a physical process that is distinct
from the one that generates the UV/optical/near-infrared emission. No
ultra-high-energy gamma-rays and no neutrino candidates consistent with
the source were found in follow-up searches. These observations support
the hypothesis that GW170817 was produced by the merger of two neutron
stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and
a kilonova/macronova powered by the radioactive decay of r-process
nuclei synthesized in the ejecta.</p