3,412 research outputs found
Detection of a very bright optical flare from a gamma-ray burst at redshift 6.29
In this letter we discuss the flux and the behavior of the bright optical
flare emission detected by the 25 cm TAROT robotic telescope during the prompt
high-energy emission and the early afterglow. We combine our data with
simultaneous observations performed in X-rays and we analyze the broad-band
spectrum. These observations lead us to emphasize the similarity of GRB 050904
with GRB 990123, a remarkable gamma-ray burst whose optical emission reached
9th magnitude. While GRB 990123 was, until now, considered as a unique event,
this observation suggests the existence of a population of GRBs which have very
large isotropic equivalent energies and extremely bright optical counterparts.
The luminosity of these GRBs is such that they are easily detectable through
the entire universe. Since we can detect them to very high redshift even with
small aperture telescopes like TAROT, they will constitute powerful tools for
the exploration of the high-redshift Universe and might be used to probe the
first generation of stars.Comment: 9 pages, 3 figures. Accepted in ApJ
Hands-On TAROT: Intercontinental use of the TAROT for Education and Public Outreach
The TAROT telescope has for primary goal the search for the prompt optical
counterpart of Cosmic Gamma-Ray Bursts. It is a completely autonomous 25cm
telescope installed near Nice (France), able to point any location of the sky
within 1-2 seconds. The control, scheduling, and data processing activities are
completely automated, so the instrument is completely autonomous. In addition
to its un-manned modes, we added recently the possibility to remotely control
the telescope, as a request of the "Hands-On Universe" (HOU) program for
exchange of time within automatic telescopes for the education and public
outreach. To this purpose we developed a simple control interface. A webcam was
installed to visualize the telescope. Access to the data is possible through a
web interface. The images can be processed by the HOU software, a program
specially suited for use within the classroom. We experienced these feature
during the open days of the University of California Berkeley and the Astronomy
Festival of Fleurance (France). We plan a regular use for an astronomy course
of the Museum of Tokyo, as well as for French schools. Not only does Hands-On
TAROT gives the general public an access to professional astronomy, but it is
also a more general tool to demonstrate the use of a complex automated system,
the techniques of data processing and automation. Last but not least, through
the use of telescopes located in many countries over the globe, a form of
powerful and genuine cooperation between teachers and children from various
countries is promoted, with a clear educational goal.Comment: 4 pages, Based on a demonstration presented at the ADASS X
Conference, Boston, MA, USA, October 2000, to appear in ASP Conf. Serie
The ultra-long GRB 111209A - II. Prompt to afterglow and afterglow properties
The "ultra-long" Gamma Ray Burst GRB 111209A at redshift z=0.677, is so far
the longest GRB ever observed, with rest frame prompt emission duration of ~4
hours. In order to explain the bursts exceptional longevity, a low metallicity
blue supergiant progenitor has been invoked. In this work, we further
investigate this peculiar burst by performing a multi-band temporal and
spectral analysis of both the prompt and the afterglow emission. We use
proprietary and publicly available data from Swift, Konus Wind, XMM-Newton,
TAROT as well as from other ground based optical and radio telescopes. We find
some peculiar properties that are possibly connected to the exceptional nature
of this burst, namely: i) an unprecedented large optical delay of 410+/-50 s is
measured between the peak epochs of a marked flare observed also in gamma-rays
after about 2 ks from the first Swift/BAT trigger; ii) if the optical and
X-ray/gamma-ray photons during the prompt emission share a common origin, as
suggested by their similar temporal behavior, a certain amount of dust in the
circumburst environment should be introduced, with rest frame visual dust
extinction of AV=0.3-1.5 mag; iii) at the end of the X-ray "steep decay phase"
and before the start of the X-ray afterglow, we detect the presence of a hard
spectral extra power law component never revealed so far. On the contrary, the
optical afterglow since the end of the prompt emission shows more common
properties, with a flux power law decay with index alpha=1.6+/-0.1 and a late
re-brightening feature at 1.1 day. We discuss our findings in the context of
several possible interpretations given so far to the complex multi-band GRB
phenomenology. We also attempt to exploit our results to further constrain the
progenitor nature properties of this exceptionally long GRB, suggesting a
binary channel formation for the proposed blue supergiant progenitor.Comment: ApJ accepted. Revised version with substantial adjustments, the main
results remain unchange
Development of a unique polyurethane primer/topcoat
USBI Company, a Division of Pratt & Whitney Government Engines and Space Propulsion, is involved in corrosion and environmental research and development activities both at their headquarters in Huntsville, Alabama and their Florida Operations at Kennedy Space Center, Florida. The programs involve the development of environmentally compatible materials that improve the corrosion protection of expensive Solid Rocket Boosters (SRB) that are part of the Space Shuttle systems developed and managed by Marshall Space Flight Center in Huntsville, Alabama. Coatings For Industry, a paint manufacturer in Souderton, PA helped formulate and produce the first lot of BOOSTERCOAT paint. High strength aluminum aerospace flight hardware exposed to harsh seacoast environments and seawater immersion presently uses high volatile organic compound (VOC) chromated and lead bearing primers and epoxy topcoats for corrosion protection. Epoxy paint tends to be brittle and has relatively low ultraviolet (UV) exposure resistance. A unique, environmentally compatible, non-leaded/non-chromated, low VOC polyurethane single coat (primer/topcoat) trade named BOOSTERCOAT has been developed for excellent corrosion protection, flexibility, adhesion, chemical and solvent resistance properties. This report will discuss the development of BOOSTERCOAT and the potential opportunities for commercial use in the energy, transportation, chemical, maritime, structural fields
Continuous optical monitoring during the prompt emission of GRB 060111B
We present the time-resolved optical emission of GRB 060111B during its
prompt phase, measured with the TAROT robotic observatory. This is the first
time that the optical emission from a gamma-ray burst has been continuously
monitored with a temporal resolution of a few seconds during the prompt
gamma-ray phase. The temporal evolution of the prompt optical emission at the
level of several seconds is used to provide a clue to the origin of this
emission. The optical emission was found to decay steadily from our first
measure, 28s after the trigger, in contrast to the gamma-ray emission, which
exhibits strong variability at the same time. This behaviour strongly suggests
that the optical emission is due to the reverse shock
Photoconductivity analyzed in the frequency domain - an introductory case study of strontium titanate
Strontium titanate (STO, SrTiO3) has been used for many applications in solid state electrochemistry and is considered a standard and model material. Its characteristics, and those of its derivatives such as STF (SrTi0.65Fe0.35O3-x), have been characterized by many groups on various aspects, such as electronic/ionic conductivity, oxygen exchange kinetics and the impact of doping. Recently, the interaction of light with STO/STF has been of increased interest. A persistent photoconductivity has been observed [1] and enhanced oxygen exchange kinetics have been detected, opening up new fields of application, such as a light-driven fuel cell [2].
The reasons behind these effects remain subject to discussion or even speculation as the relation to the relatively large bandgap and the photoresponse at long wavelengths remains unclear. What makes the analysis of these effects difficult is the interplay of many electrochemical and photoelectrochemical processes that contribute to the photoresponse including the electronic and ionic conductivity, the number and nature of charge carriers, charge traps, phonon related effects, and surface reactions. With electrochemical impedance spectroscopy (EIS), one can distinguish diverse processes on the basis of their time constants and how they evolve as a function of operating conditions, such as temperature, atmosphere (leading to stoichiometry changes) and illumination. However, the impact of light can only be characterized implicitly as a change in other processes that also prevail in the dark.
Intensity modulated photocurrent/-voltage spectroscopy (IMPS/IMVS) have been shown to reveal valuable information about charge carrier dynamics for photoelectrodes and photovoltaic cells [3]. To the best of our knowledge, these techniques have never been applied to devices or materials that are not photoactive, or in other words, that do not show a photovoltage, such as a symmetrical model cells based on STO or STF. However, with the small signal light perturbation that is the key element of IMPS and IMVS, we can trigger the light effect directly and analyze the system response by its current and voltage signals.
In this contribution, we will begin with a brief introduction into IMPS and IMVS and show how these techniques can be applied to model electrodes consisting of STO and STF. The results are compared to EIS under different illumination and we will show how to extract the relevant information about the photoresponse. By evaluating the activation energies of the different electrochemical and photoelectrochemical processes, we can attribute those to physical effects and clarify some of the previously unknown processes that lead to anomalies observed in STO/STF under illumination.
The capacity of IMPS and IMVS have been underestimated so far and in this contribution, we will conclude with an outlook for their potential to other fields of application, such as ionic motion in perovskite solar cells that are thought to be responsible for their accelerated degradation under illumination.
This work was supported by JSPS Core-to-Core Program, A. Advanced Research Networks: “Solid Oxide Interfaces for Faster Ion Transport”.
References
[1] M. C. Tarun et al., Phys. Rev. Lett. 111, 187403, 2013.
[2] G. C. Bunauer, Adv. Funct. Mater. 26, 120, 2016.
[3] D. Klotz et al., Phys. Chem. Chem. Phys. 18, 23438, 2016
Early optical observations of GRBs by the TAROT telescopes: period 2001-2008
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.Comment: 13 pages, 2 color figures, 5 b&w figures. Accepted for publication in
Astronomical Journa
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