GRBS Followed-up by the bootes network Guziy, S.; Castro-Tirado, A.; Jelínek, M. ...
EAS Publications Series,
2013, 2013-00-00, 20130101, Letnik:
61
Journal Article
The Burst Observer and Optical Transient Exploring System (BOOTES), is a global robotic observatory network, which started in 1998 with Spanish leadership devoted to study optical emissions from ...gamma ray bursts (GRBs) that occur in the Universe. We present shot history and current status of BOOTES network. The Network philosophy, science and some details of 117 GRBs followed-up are discussed.
Aims. We study the dark nature of GRB 130528A through multi-wavelength observations and conclude that the main reason for the optical darkness is local extinction inside of the host galaxy. Methods. ...Automatic observations were performed at the Burst Optical Observer and Transient Exploring System (BOOTES)-4/MET robotic telescope. We also triggered target of opportunity (ToO) observations at Observatorio de Sierra Nevada (OSN), IRAM Plateau de Bure Interferometer (PdBI) and Gran Telescopio Canarias (GTC + OSIRIS). The host galaxy photometric observations in optical to near-infrared (nIR) wavelengths were achieved through large ground-based aperture telescopes, such as 10.4 m Gran Telescopio Canarias (GTC), 4.2 m William Herschel Telescope (WHT), 6 m Bolshoi Teleskop Alt-azimutalnyi (BTA) telescope, and 2 m Liverpool Telescope (LT). Based on these observations, spectral energy distributions (SED) for the host galaxy and afterglow were constructed. Results. Thanks to millimetre (mm) observations at PdBI, we confirm the presence of a mm source within the XRT error circle that faded over the course of our observations and identify the host galaxy. However, we do not find any credible optical source within early observations with BOOTES-4/MET and 1.5 m OSN telescopes. Spectroscopic observation of this galaxy by GTC showed a single faint emission line that likely corresponds to OII 3727 Å at a redshift of 1.250 ± 0.001, implying a star formation rate (M⊙/yr) > 6.18 M⊙/yr without correcting for dust extinction. The probable line-of-sight extinction towards GRB 130528A is revealed through analysis of the afterglow SED, resulting in a value of \hbox{$A^{\rm GRB}_{V}$}AVGRB≥ 0.9 at the rest frame; this is comparable to extinction levels found among other dark GRBs. The SED of the host galaxy is explained well (χ2/d.o.f. = 0.564) by a luminous (MB = −21.16), low-extinction (AV = 0, rest frame), and aged (2.6 Gyr) stellar population. We can explain this apparent contradiction in global and line-of-sight extinction if the GRB birth place happened to lie in a local dense environment. In light of having relatively small specific star formation rate ~5.3 M⊙/yr (L/L⋆)-1, this also could explain the age of the old stellar population of host galaxy.
Additive manufacturing enables design of multi-material composite materials with tunable mechanical properties. Previous studies on epoxy-based composites containing silica, clays or fiber showed ...that favorable mechanical properties can be achieved by controlling the fiber orientation and architecture. In this work the effect of the build direction and whiskers orientation on the wear properties of 3D printed epoxy-based nanocomposites is investigated. Epoxy-nanoclay-PTFE-SiC nanocomposites are fabricated using a direct-write additive manufacturing method that enables one to orient the SiC whiskers along the printing path. Tribological results show that variations in build direction and whiskers orientation relative to the sliding direction cause anisotropy in wear and friction in these nanocomposites. The best wear performance was achieved with the nanocomposites printed with whiskers oriented perpendicular to the sliding steel counter-surface and slid orthogonally to the build direction and print path orientation. All nanocomposites had significantly better wear properties than the unfilled epoxy sample. The results suggest that optimizing the whisker orientation and alignment in epoxy-based nanocomposites through direct-write additive manufacturing increases the wear performance. This enables an additional design paradigm when optimizing multifunctional, 3D-printed epoxy nanocomposites.
ABSTRACT We present results from a multi-chord Pluto stellar occultation observed on 2015 June 29 from New Zealand and Australia. This occurred only two weeks before the NASA New Horizons flyby of ...the Pluto system and serves as a useful comparison between ground-based and space results. We find that Pluto's atmosphere is still expanding, with a significant pressure increase of 5 2% since 2013 and a factor of almost three since 1988. This trend rules out, as of today, an atmospheric collapse associated with Pluto's recession from the Sun. A central flash, a rare occurrence, was observed from several sites in New Zealand. The flash shape and amplitude are compatible with a spherical and transparent atmospheric layer of roughly 3 km in thickness whose base lies at about 4 km above Pluto's surface, and where an average thermal gradient of about 5 K km−1 prevails. We discuss the possibility that small departures between the observed and modeled flash are caused by local topographic features (mountains) along Pluto's limb that block the stellar light. Finally, using two possible temperature profiles, and extrapolating our pressure profile from our deepest accessible level down to the surface, we obtain a possible range of 11.9-13.7 bar for the surface pressure.
Magnetars are young neutron stars with very strong magnetic fields of the order of 1014-1015 G. They are detected in our Galaxy either as soft -ray repeaters or anomalous X-ray pulsars. Soft -ray ...repeaters are a rare type of -ray transient sources that are occasionally detected as bursters in the high-energy sky. No optical counterpart to the -ray flares or the quiescent source has yet been identified. Here we report multi-wavelength observations of a puzzling source, SWIFT J195509+261406. We detected more than 40 flaring episodes in the optical band over a time span of three days, and a faint infrared flare 11 days later, after which the source returned to quiescence. Our radio observations confirm a Galactic nature and establish a lower distance limit of ∼3.7 kpc. We suggest that SWIFT J195509+261406 could be an isolated magnetar whose bursting activity has been detected at optical wavelengths, and for which the long-term X-ray emission is short-lived. In this case, a new manifestation of magnetar activity has been recorded and we can consider SWIFT J195509+261406 to be a link between the 'persistent' soft -ray repeaters/anomalous X-ray pulsars and dim isolated neutron stars.
Dark GRBs constitute a significant fraction of the GRB population. In this paper, we present the multiwavelength analysis of an intense two-episodic GRB 150309A observed early on to ~114 days ...post-burst. Despite the strong gamma-ray emission, no optical afterglow was detected for this burst. However, we discovered near-infrared afterglow (\(K_{\rm S}\)-band), ~5.2 hours post burst, with the CIRCE instrument mounted at the 10.4m GTC. We used Fermi observations of GRB 150309A to understand the prompt emission mechanisms and jet composition. We performed the early optical observations using the BOOTES robotic telescope and late-time afterglow observations using the GTC. A potential faint host galaxy is also detected at optical wavelength using the GTC. We modelled the potential host galaxy of GRB 150309A in order to explore the environment of the burst. The time-resolved spectral analysis of Fermi data indicates a hybrid jet composition consisting of a matter-dominated fireball and magnetic-dominated Poynting flux. GTC observations of the afterglow revealed that the counterpart of GRB 150309A was very red, with H-\(K_{\rm S}\) > 2.1 mag (95 \(\%\) confidence). The red counterpart was not discovered in any bluer filters of Swift UVOT, indicative of high redshift origin. This possibility was discarded based on multiple arguments, such as spectral analysis of X-ray afterglow constrain z < 4.15 and a moderate redshift value obtained using spectral energy distribution modelling of the potential galaxy. The broadband afterglow SED implies a very dusty host galaxy with deeply embedded GRB (suggesting \(A_{\rm V}\) \(\gtrsim\) 35 mag). The environment of GRB 150309A demands a high extinction towards the line of sight, demanding dust obscuration is the most probable origin of optical darkness and the very red afterglow of GRB 150309A. This result makes GRB 150309A the highest extinguished GRB known to date.
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