65 research outputs found
BART 2001–2004: An intelligent robotic observatory
BART is a robotic observatory located at the Astronomical Institute in Ondrejov, Czech Republic. It is a relatively low-cost (25 cm + two wide-field lenses) device developed for rapid follow-ups of GRBs. Since 2001 when it started
to observe, it has done several such observations. Meanwhile, photometric monitoring tasks are performed, using an intelligent selection algorithm. Not only the
telescope is automatic, the entire observatory does not require human presence: system prepares the schedule, observes, registers the images and stores them into
database without human intervention: human assistance is reduced to maintenance and weather checking. BART is a primary developing platform for RTS2, the robotic
telescope operation software, which allows for unattended observation as well as control of the entire observatory
The bright optical flash from GRB 060117
We present a discovery and observation of an extraordinarily bright prompt
optical emission of the GRB 060117 obtained by a wide-field camera atop the
robotic telescope FRAM of the Pierre Auger Observatory from 2 to 10 minutes
after the GRB. We found rapid average temporal flux decay of alpha = -1.7 +-
0.1 and a peak brightness R = 10.1 mag. Later observations by other instruments
set a strong limit on the optical and radio transient fluxes, unveiling an
unexpectedly rapid further decay. We present an interpretation featuring a
relatively steep electron-distribution parameter p ~ 3.0 and providing a
straightforward solution for the overall fast decay of this optical transient
as a transition between reverse and forward shock.Comment: Accepted to A&A, 4 pages, corected few typos pointed out by X.F. W
A photometric redshift of for the \agile GRB 080514B
Aims: The AGILE gamma-ray burst GRB 080514B is the first burst with detected
emission above 30 MeV and an optical afterglow. However, no spectroscopic
redshift for this burst is known.
Methods: We compiled ground-based photometric optical/NIR and millimeter data
from several observatories, including the multi-channel imager GROND, as well
as ultraviolet \swift UVOT and X-ray XRT observations. The spectral energy
distribution of the optical/NIR afterglow shows a sharp drop in the \swift UVOT
UV filters that can be utilized for the estimation of a redshift.
Results: Fitting the SED from the \swift UVOT band to the band, we
estimate a photometric redshift of , consistent with the
pseudo redshift reported by Pelangeon & Atteia (2008) based on the gamma-ray
data.
Conclusions: The afterglow properties of GRB 080514B do not differ from those
exhibited by the global sample of long bursts, supporting the view that
afterglow properties are basically independent of prompt emission properties.Comment: submitted to A&A letter
Comprehensive multi-wavelength modelling of the afterglow of GRB050525A
The Swift era has posed a challenge to the standard blast-wave model of Gamma
Ray Burst (GRB) afterglows. The key observational features expected within the
model are rarely observed, such as the achromatic steepening (`jet-break') of
the light curves. The observed afterglow light curves showcase additional
complex features requiring modifications within the standard model. Here we
present optical/NIR observations, millimeter upper limits and comprehensive
broadband modelling of the afterglow of the bright GRB 0505025A, detected by
Swift. This afterglow cannot be explained by the simplistic form of the
standard blast-wave model. We attempt modelling the multi-wavelength light
curves using (i) a forward-reverse shock model, (ii) a two-component outflow
model and (iii) blast-wave model with a wind termination shock. The
forward-reverse shock model cannot explain the evolution of the afterglow. The
two component model is able to explain the average behaviour of the afterglow
very well but cannot reproduce the fluctuations in the early X-ray light curve.
The wind termination shock model reproduces the early light curves well but
deviates from the global behaviour of the late-time afterglow.Comment: 20 pages, 6 figures, accepted for publication in MNRA
Simultaneous and optical follow-up GRB observations by BOOTES
Since 1998 BOOTES has provided follow-up observations for more than 70 GRBs; the most important results obtained so far are the detection of an OT in the GRB 000313 error box and the non-detection of optical emission simultaneous to the high-energy emission for several GRBs (both long/soft and short/hard events)
BOOTES-IR: Near IR follow-up GRB observations by a robotic system
“BOOTES-IR” is the extension of the BOOTES experiment, which
operates in Southern Spain since 1998, to the near IR (NIR). The goal is to follow up the early stage of the gamma ray burst (GRB) afterglow emission in the NIR, alike BOOTES does already at optical wavelengths. The scientific case that drives the BOOTES-IR performance is the study of GRBs with the support of spacecraft like INTEGRAL, SWIFT and GLAST. Given that the afterglow emission in both, the NIR and the optical, in the instances immediately following a GRB, is extremely bright (reached V = 8.9 in one case), it should be possible to detect this prompt emission at NIR wavelengths too. The combined observations by BOOTES-IR and
BOOTES-1 and BOOTES-2 will allow for real time identification of trustworthy candidates to have a high redshift (z > 5). It is expected that, few minutes after
a GRB, the IR magnitudes be H ∼ 7–10, hence very high quality spectra can be obtained for objects as far as z = 10 by larger instruments
Detection of the high z GRB 080913 and its implications on progenitors and energy extraction mechanisms
Aims: We present multiwavelength observations of one of the most distant
gamma-ray bursts detected so far, GRB 080913. Based on these observations, we
consider whether it could be classified as a short-duration GRB and discuss the
implications for the progenitor nature and energy extraction mechanisms.
Methods: Multiwavelength X-ray, near IR and millimetre observations were made
between 20.7 hours and 16.8 days after the event.
Results: Whereas a very faint afterglow was seen at the 3.5m CAHA telescope
in the nIR, the X-ray afterglow was clearly detected in both Swift and
XMM-Newton observations. An upper limit is reported in the mm range. We have
modeled the data assuming a collimated 3 blast
wave with an energy injection at 0.5 days carrying erg or
approximately 12 times the initial energy of the blast wave. We find that GRB
080913 shares many of the gamma-ray diagnostics with the more recent burst GRB
090423 for being classified as short had they ocurred at low redshift. If the
progenitor were a compact binary merger, it is likely composed by a NS and BH.
The Blandford-Znajek (BZ) mechanism is the preferred one to extract energy from
the central, maximally-rotating BH. Both the magnetic field close to the event
horizon (B) and the BH mass () are restricted within a relatively
narrow range, such that . Similar constraints on the central BH hold for collapsar-like progenitor
systems if the BZ-mechanism works for the system at hand.Comment: 7 pages, 4 figures. Accepted for publication in A&
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
GRB 090313 and the Origin of Optical Peaks in Gamma-Ray Burst Light Curves: Implications for Lorentz Factors and Radio Flares
We use a sample of 19 gamma-ray bursts (GRBs) that exhibit single-peaked optical light curves to test the standard fireball model by investigating the relationship between the time of the onset of the afterglow and the temporal rising index. Our sample includes GRBs and X-ray flashes for which we derive a wide range of initial Lorentz factors (40 < Γ < 450). Using plausible model parameters, the typical frequency of the forward shock is expected to lie close to the optical band; within this low typical frequency framework, we use the optical data to constrain epsilon e and show that values derived from the early time light-curve properties are consistent with published typical values derived from other afterglow studies. We produce expected radio light curves by predicting the temporal evolution of the expected radio emission from forward and reverse shock components, including synchrotron self-absorption effects at early time. Although a number of GRBs in this sample do not have published radio measurements, we demonstrate the effectiveness of this method in the case of Swift GRB 090313, for which millimetric and centimetric observations were available, and conclude that future detections of reverse-shock radio flares with new radio facilities such as the EVLA and ALMA will test the low-frequency model and provide constraints on magnetic models
- …