17 research outputs found
the rem observing software
The Rapid Eye Mount (REM) is a 60 cm robotic telescope located at La Silla, Chile. Its Observing Software (REMOS) is constituted by a set of distributed intercommunicating processes organized around a central manager. Together they grant the system safety, automatically schedule and perform observations with two simultaneous cameras of user-defined targets, and drive fast reaction to satellite alerts. Subsequent data reduction is left to pipelines managed by each camera
REM: Automatic for the People
We present the result of a year-long effort to think, design, build, realize, and manage the robotic, autonomous REM observatory, placed since June 2003 on the cerro La Silla, ESO Chile. The various aspects of the management and control are here surveyed, with the nice ideas and the wrong dead ends we encountered under way. Now REM is offered to the international astronomical community, a real, schedulable telescope, automatic for the People
Models for the Type Ic Hypernova SN 2003lw associated with GRB 031203
The Gamma-Ray Burst 031203 at a redshift z=0.1055 revealed a highly reddened
Type Ic Supernova, SN 2003lw, in its afterglow light. This is the third well
established case of a link between a long-duration GRB and a type Ic SN. The SN
light curve is obtained subtracting the galaxy contribution and is modelled
together with two spectra at near-maximum epochs. A red VLT grism 150I spectrum
of the SN near peak is used to extend the spectral coverage, and in particular
to constrain the uncertain reddening, the most likely value for which is
E_{G+H}(B-V) about 1.07 +/- 0.05. Accounting for reddening, SN 2003lw is about
0.3 mag brighter than the prototypical GRB-SN 1998bw. Light curve models yield
a 56Ni mass of about 0.55 solar mass. The optimal explosion model is somewhat
more massive (ejecta mass about 13 solar mass) and energetic (kinetic energy
about 6 times 10^52 erg) than the model for SN 1998bw, implying a massive
progenitor (40 - 50 solar mass). The mass at high velocity is not very large
(1.4 solar mass above 30000 km/s, but only 0.1 solar mass above 60000 km/s),
but is sufficient to cause the observed broad lines. The similarity of SNe
2003lw and 1998bw and the weakness of their related GRBs, GRB031203 and
GRB980425, suggest that both GRBs may be normal events viewed slightly off-axis
or a weaker but possibly more frequent type of GRB.Comment: 19 pages, 8 figures, accepted for publication in Ap
A magnetar powering the ordinary monster GRB 130427A?
We present the analysis of the extraordinarily bright Gamma-Ray Burst (GRB)
130427A under the hypothesis that the GRB central engine is an
accretion-powered magnetar. In this framework, initially proposed to explain
GRBs with precursor activity, the prompt emission is produced by accretion of
matter onto a newly-born magnetar, and the observed power is related to the
accretion rate. The emission is eventually halted if the centrifugal forces are
able to pause accretion. We show that the X-ray and optical afterglow is well
explained as the forward shock emission with a jet break plus a contribution
from the spin-down of the magnetar. Our modelling does not require any
contribution from the reverse shock, that may still influence the afterglow
light curve at radio and mm frequencies, or in the optical at early times. We
derive the magnetic field ( G) and the spin period (
ms) of the magnetar and obtain an independent estimate of the minimum
luminosity for accretion. This minimum luminosity results well below the prompt
emission luminosity of GRB 130427A, providing a strong consistency check for
the scenario where the entire prompt emission is the result of continuous
accretion onto the magnetar. This is in agreement with the relatively long spin
period of the magnetar. GRB 130427A was a well monitored GRB showing a very
standard behavior and, thus, is a well-suited benchmark to show that an
accretion-powered magnetar gives a unique view of the properties of long GRBs.Comment: 5 pages, 1 figure, accepted for publication in MNRAS Letter
The ASTRI SST-2M prototype for the Cherenkov Telescope Array: status after the commissioning phase of the telescope
ASTRI SST-2M is an imaging atmospheric Cherenkov telescope developed by the Italian National Institute of Astrophysics (INAF) in the framework of the Cherenkov Telescope Array (CTA) project as an end-to-end prototype for the Small Size array. Large-, medium-, and small-sized telescopes will compose the CTA observatory that represents the next generation of imaging atmospheric Cherenkov telescopes and will explore the very high-energy domain from a few tens of GeV up to few hundreds of TeV. The ASTRI SST-2M telescope has been installed at the INAF-Catania observing station at Serra La Nave, on Mt. Etna (Sicily, Italy) in September 2014. In these 3 years of open-air operations the telescope has been commissioned and its opto-mechanical performance is now well understood. The apparatus was made ready to host its main scientific instrument, the camera with Silicon-Photomultiplier based detectors. This contribution is a status report on the complete ASTRI SST-2M telescope assembly including the electro-mechanical structure and the optical system
The ASTRI SST-2M prototype for the Cherenkov Telescope Array: opto-mechanical performance
ASTRI SST-2M is an end-to-end telescope prototype developed by the Italian National Institute of Astrophysics (INAF) in the framework of the Cherenkov Telescope Array (CTA). The CTA observatory, with a combination of large-, medium-, and small-sized telescopes (LST, MST and SST, respectively), will represent the next generation of imaging atmospheric Cherenkov telescopes. It will explore the very high-energy domain from a few tens of GeV up to few hundreds of TeV. The ASTRI SST-2M telescope structure and mirrors have been installed at the INAF observing station at Serra La Nave, on Mt. Etna (Sicily, Italy) in September 2014. Its performance verification phase began in autumn 2015. Part of the scheduled activities foresees the study and characterization of the optical and opto-mechanical performance of the telescope prototype. In this contribution we report the results achieved in terms of kinematic model analysis, mirrors reflectivity evolution, telescopes positioning, flexures and pointing model and the thermal behavior
A Path to the Stars: The Evolution of the Species
During the last years, a number of telescopes have been dedicated to the followup of the GRBs. But after the Swift launch, the average observed intensity of the GRBs showed to be lower than thought before. Our experience with the robotic 60 cm REM telescope confirmed this evidence, with a large number oflostGRBs. Then, we proposed to study the feasibility of a 4 m fast pointing class telescope, equipped with a multichannel imagers, from Visible to Near Infrared. In this paper, we present the main result of the feasibility study we performed so far
SN 2003lw and GRB 031203: A Bright Supernova for a Faint Gamma-ray Burst
Optical and near-infrared observations of the gamma-ray burst GRB 031203, at
z = 0.1055, are reported. A very faint afterglow is detected superimposed to
the host galaxy in our first infrared JHK observations, carried out ~9 hours
after the burst. Subsequently, a rebrightening is detected in all bands,
peaking in the R band about 18 rest-frame days after the burst. The
rebrightening closely resembles the light curve of a supernova like SN 1998bw,
assuming that the GRB and the SN went off almost simultaneously, but with a
somewhat slower evolution. Spectra taken close to the maximum of the
rebrightening show extremely broad features as in SN 1998bw. The determination
of the absolute magnitude of this SN (SN 2003lw) is difficult owing to the
large and uncertain extinction, but likely this event was brighter than SN
1998bw by 0.5 mag in the VRI bands, reaching an absolute magnitude M_V =
-19.75+-0.15.Comment: 6 pages, 4 figures. Accepted to ApJ Letters. Fig. 4 will not appear
in the journal version due to space limitations. Typos fixed in Table 1
(thanks to Dr. Alexander Kann for pointing out the problem). No measurements
change
Variability of Disk Emission in Pre-Main Sequence and Related Stars. II. Variability in the Gas and Dust Emission of the Herbig Fe Star SAO 206462
We present thirteen epochs of near-infrared (0.8-5 micron) spectroscopic
observations of the pre-transitional, "gapped" disk system in SAO 206462 (=HD
135344B). In all, six gas emission lines (including Br gamma, Pa beta, and the
0.8446 micron line of O I) along with continuum measurements made near the
standard J, H, K, and L photometric bands were measured. A mass accretion rate
of approximately 2 x 10^-8 solar masses per year was derived from the Br gamma
and Pa beta lines. However, the fluxes of these lines varied by a factor of
over two during the course of a few months. The continuum also varied, but by
only ~30%, and even decreased at a time when the gas emission was increasing.
The H I line at 1.083 microns was also found to vary in a manner inconsistent
with that of either the hydrogen lines or the dust. Both the gas and dust
variabilities indicate significant changes in the region of the inner gas and
the inner dust belt that may be common to many young disk systems. If planets
are responsible for defining the inner edge of the gap, they could interact
with the material on time scales commensurate with what is observed for the
variations in the dust, while other disk instabilities (thermal,
magnetorotational) would operate there on longer time scales than we observe
for the inner dust belt. For SAO 206462, the orbital period would likely be 1-3
years. If the changes are being induced in the disk material closer to the star
than the gap, a variety of mechanisms (disk instabilities, interactions via
planets) might be responsible for the changes seen. The He I feature is most
likely due to a wind whose orientation changes with respect to the observer on
time scales of a day or less. To further constrain the origin of the gas and
dust emission will require multiple spectroscopic and interferometric
observations on both shorter and longer time scales that have been sampled so
far.Comment: 42 pages, 10 figure