The TAROT telescopes (Telescopes a Action Rapide pour les Objets Transitoires) are two robotic observatories designed to observe the prompt optical emission counterpart and the early afterglow of gamma ray bursts (GRBs). We present data acquired between 2001 and 2008 and discuss the properties of the optical emission of GRBs, noting various interesting results. The optical emission observed during the prompt GRB phase is rarely very bright: we estimate that 5% to 20% of GRBs exhibit a bright optical flash (R<14) during the prompt gamma-ray emission, and that more than 50% of the GRBs have an optical emission fainter than R=15.5 when the gamma-ray emission is active. We study the apparent optical brightness distribution of GRBs at 1000 s showing that our observations confirm the distribution derived by other groups. The combination of these results with those obtained by other rapid slewing telescopes allows us to better characterize the early optical emission of GRBs and to emphasize the importance of very early multi-wavelength GRB studies for the understanding of the physics of the ejecta.

Early optical observations of GRBs by the TAROT telescopes: period 2001-2008

The Telescopes a Action Rapide pour les Objets Transitoires telescopes are two robotic observatories designed to observe the prompt optical emission counterpart and the early afterglow of gamma-ray bursts (GRBs). We present data acquired between 2001 and 2008 and discuss the properties of the optical emission of GRBs, noting various interesting results. The optical emission observed during the prompt GRB phase is rarely very bright: we estimate that 5%-20% of GRBs exhibit a bright optical flash (R < 14) during the prompt gamma-ray emission, and that more than 50% of the GRBs have an optical emission fainter than R = 15.5 when the gamma-ray emission is active. We study the apparent optical brightness distribution of GRBs at 1000 s showing that our observations confirm the distribution derived by other groups. The combination of these results with those obtained by other rapid slewing telescopes allows us to better characterize the early optical emission of GRBs and to emphasize the importance of very early multiwavelength GRB studies for the understanding of the physics of the ejecta.

http://iopscience.iop.org/article/10.1088/0004-6256/137/5/4100/pdf

Early Optical Observations of Gamma-Ray Bursts by the TAROT Telescopes: Period 2001-2008

We present a summary of GRB follow-ups carried out with robotic telescopes driven by RTS2: BART, the BOOTES network, FRAM and Watcher We describe various set-ups which RTS2 controls We discuss GRBs followed by those telescopes

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Status of robotics telescopes driven by RTS2 (BART, BOOTES, FRAM and Watcher)

Rapido is a robotic telescope designed to be duplicated in order to build a network that answers specific requirements of fast transients. The challenge of Rapido is to be a low cost, very fast pointing telescope, with high reliability and a little maintenance cost. Mechanics is based on a coil winding winch. Optics and electronics are commercials. Mount of Rapido is home made and is described in details and tests on the sky are reported. The first mount of Rapido is now operated as TAROT Reunion.

TAROT Reunion a telescope based on the Rapido design for reliable optical observations of fast transients

Most of the small 1m-class telescopes designed for fast tracking of transient object, like GRBs, are equipped with infrared and visible cameras, fed through a dichroic. We stud ied a new concept for a fast and compact multi-band visible camera, using successive dichroics, to cover simultaneously many visible bands (U,B,V,R, and I), sampled with one more CCD detectors. This extended spectral coverage will help to observe transient faint objects. To keep envelope size, weight and overall cost at a reasonable level, a trade-off has been carried out. Keywords: Visible camera, 1m-class telescopes, multi-band, dichroic, GRB 1. INTRODUCTION This paper presents the study and design of some optical elements necessary in order to build instruments with the possibility to produce simultaneous acquisitions of the same source in different spectral customizable bands. Many astrophysical fields can benefit from such an instrument, mainly in the monitoring of fast transient sources. In particular, we can gain the possibility to measure the spectral energy distribution in one exposure. Some of the most appealing sources to be monitored with th is kind of instruments will be the Gamma Ray Bursts (GRB), the Active Galactic Nuclei (AGN), variable st ars, objects with peculiar spectral features. One of the pioneering instruments that use the principle of simultaneous acquisition in different bands is GROND, a seven-channel instrument installed at MPI/ESO 2.2m, at La Silla (Chile) [1]. We are proposing the translation of the principle into instruments suitable for smaller 1-m class telescopes. This idea comes from the availability of small telescopes dedicated to the monitoring of fast transient like GRB. In this paper we will present solutions for the optical arm for the two 60-cm telescopes, REM and BOOTES, respectively installed on La Silla (Chile) and Sierra Nevada (Spain).

Compact multi-band visible camera for 1m-class fast telescopes

BOOTES-IR: Near IR follow-up GRB observations by a robotic system

"BOOTES-IR" is the extension of the BOOTES experiment, which has been operating in Southern Spain since 
1998, to the near-infrared (nIR). The goal is to follow up the early stage of the gamma ray burst (GRB) 
afterglow emission in the nIR, as 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 HETE-2, INTEGRAL and 
SWIFT (and GLAST in the future). 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. Combined observations by BOOTES-IR and BOOTES-1 
and BOOTES-2 since 2006 can allow for real time identification of trustworthy candidates to have a ultra-high 
redshift (z > 6). It is expected that, few minutes after a GRB, the nIR magnitudes be H ~ 10-15, hence very 
high quality spectra can be obtained for objects as far as z = 10 by much larger ground-based telescopes. A 
significant fraction of observing time will be available for other scientific projects of interest, objects relatively 
bright and variable, like Solar System objects, brown dwarfs, variable stars, planetary nebulae, compact objects 
in binary systems and blazars.

J. Díaz Verdejo

Papers

BOOTES-IR: Near IR follow-up GRB observations by a robotic system

BOOTES-IR: a robotic nIR astronomical observatory devoted to follow-up of transient phenomena