16 research outputs found
Fabrication and current optical performance of a large diamond-machined ZnSe immersion grating
Abstract not provide
When Do Internal Shocks End and External Shocks Begin? Early-Time Broadband Modelling of GRB 051111
Even with the renaissance in gamma-ray burst (GRB) research fostered by the
Swift satellite, few bursts have both contemporaneous observations at long
wavelengths and exquisite observations at later times across the
electromagnetic spectrum. We present here contemporaneous imaging with the KAIT
robotic optical telescope, dense optical sampling with Lulin, and supplemented
with infrared data from PAIRITEL and radio to gamma-ray data from the
literature. For the first time, we can test the constancy of microphysical
parameters in the internal-external shock paradigm and carefully trace the flow
of energy from the GRB to the surrounding medium. KAIT data taken <~1 minute
after the start of GRB051111 and coinciding with the fading gamma-ray tail of
the prompt emission indicate a smooth re-injection of energy into the shock. No
color change is apparent in observations beginning ~1.5 minutes after the GRB
and lasting for the first hour after the burst. There are achromatic flux
modulations about the best-fit model at late (t~10^4 s) times, possibly due to
variations in the external density. We find that the host-galaxy extinction is
well fit by a curve similar to that ofthe Small Magellanic Cloud. Low visual
extinction, A_V~0.2 mag, combined with high column densities determined from
the X-ray and optical spectroscopy (N_H> 10^21 cm^-2), indicate a low
dust-to-metals ratio and a possible over-abundance of the light metals. An
apparent small ratio of total to selective extinction (R_V~2) argues against
dust destruction by the GRB. Time constancy of both the IR/optical/UV spectral
energy distribution and the soft X-ray absorption suggests that the absorbing
material is not local to the GRB.Comment: 21 pages, 6 figures, to Appear in ApJ v653, December, 10 200
DISCOVERY OF DRAMATIC OPTICAL VARIABILITY IN SDSS J1100+4421: A PECULIAR RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXY?
We present our discovery of dramatic variability in SDSS J1100+4421 by the high-cadence transient survey Kiso Supernova Survey (KISS). The source brightened in the optical by at least a factor of three within about half a day. Spectroscopic observations suggest that this object is likely a narrow-line Seyfert 1 galaxy (NLS1) at z=0.840, however with unusually strong narrow emission lines. The estimated black hole mass of ~ 10^7 Msun implies bolometric nuclear luminosity close to the Eddington limit. SDSS J1100+4421 is also extremely radio-loud, with a radio loudness parameter of R ~ 4 x 10^2 - 3 x 10^3, which implies the presence of relativistic jets. Rapid and large-amplitude optical variability of the target, reminiscent of that found in a few radio- and gamma-ray loud NLS1s, is therefore produced most likely in a blazar-like core. The 1.4 GHz radio image of the source shows an extended structure with a linear size of about 100 kpc. If SDSS J1100+4421 is a genuine NLS1, as suggested here, this radio structure would then be the largest ever discovered in this type of active galaxie
OISTER optical and near-infrared monitoring observations of peculiar radio-loud active galactic nucleus SDSS J110006.07+442144.3
We present monitoring campaign observations at optical and near-infrared (NIR) wavelengths for a radio-loud active galactic nucleus (AGN) at z = 0.840, SDSS J110006.07+442144.3 (hereafter, J1100+4421), which was identified during a flare phase in late 2014 February. The campaigns consist of three intensive observing runs from the discovery to 2015 March, mostly within the scheme of the OISTER collaboration. Optical-NIR light curves and simultaneous spectral energy distributions (SEDs) are obtained. Our measurements show the strongest brightening in 2015 March. We found that the optical-NIR SEDs of J1100+4421 show an almost steady shape despite the large and rapid intranight variability. This constant SED shape is confirmed to extend to ∼5 μm in the observed frame using the archival WISE data. Given the lack of absorption lines and the steep power-law spectrum of α ν ∼ -1.4, where fνναν, synchrotron radiation by a relativistic jet with no or small contributions from the host galaxy and the accretion disk seems most plausible as an optical-NIR emission mechanism. The steep optical-NIR spectral shape and the large amplitude of variability are consistent with this object being a low ν peak jet-dominated AGN. In addition, sub-arcsecond resolution optical imaging data taken with Subaru Hyper Suprime-Cam does not show a clear extended component and the spatial scales are significantly smaller than the large extensions detected at radio wavelengths. The optical spectrum of a possible faint companion galaxy does not show any emission lines at the same redshift, and hence a merging hypothesis for this AGN-related activity is not supported by our observations. © The Author 2017. Published by Oxford University Press on behalf of the Astronomical Society of Japan. All rights reserved
Thermo-physical properties of 162173 (1999 JU3), a potential flyby and rendezvous target for interplanetary missions
Near-Earth asteroid 162173 (1999 JU3) is a potential flyby and rendezvous
target for interplanetary missions because of its easy to reach orbit. The
physical and thermal properties of the asteroid are relevant for establishing
the scientific mission goals and also important in the context of near-Earth
object studies in general. Our goal was to derive key physical parameters such
as shape, spin-vector, size, geometric albedo, and surface properties of 162173
(1999 JU3). With three sets of published thermal observations (ground-based
N-band, Akari IRC, Spitzer IRS), we applied a thermophysical model to derive
the radiometric properties of the asteroid. The calculations were performed for
the full range of possible shape and spin-vector solutions derived from the
available sample of visual lightcurve observations. The near-Earth asteroid
162173 (1999 JU3) has an effective diameter of 0.87 +/- 0.03 km and a geometric
albedo of 0.070 +/- 0.006. The chi2-test reveals a strong preference for a
retrograde sense of rotation with a spin-axis orientation of lambda_ecl = 73
deg, beta_ecl = -62 deg and P_sid = 7.63 +/- 0.01 h. The most likely thermal
inertia ranges between 200 and 600 Jm-2s-0.5K-1, about a factor of 2 lower than
the value for 25143 Itokawa. This indicates that the surface lies somewhere
between a thick-dust regolith and a rock/boulder/cm-sized, gravel-dominated
surface like that of 25143 Itokawa. Our analysis represents the first time that
shape and spin-vector information has been derived from a combined data set of
visual lightcurves (reflected light) and mid-infrared photometry and
spectroscopy (thermal emission).Comment: 6 pages, 5 figures, 2 tables, accepted for publication in A&A (date
of acceptance 05/Nov/2010
Thermo-physical properties of 162173 (1999 JU3), a potential flyby and rendezvous target for interplanetary missions
Context. Near-Earth asteroid 162173 (1999 JU3) is a potential flyby and
rendezvous target for interplanetary missions because of its easy-to-reach orbit. The
physical and thermal properties of the asteroid are relevant for establishing the
scientific mission goals and also important in the context of near-Earth object studies in
general.
Aims. Our goal was to derive key physical parameters such as shape,
spin-vector, size, geometric albedo, and surface properties of 162173 (1999 JU3).
Methods. With three sets of published thermal observations (ground-based
N-band, Akari IRC, Spitzer IRS), we applied a thermophysical model to
derive the radiometric properties of the asteroid. The calculations were performed for the
full range of possible shape and spin-vector solutions derived from the available sample
of visual lightcurve observations.
Results. The near-Earth asteroid 162173 (1999 JU3) has an effective
diameter of 0.87 ± 0.03 km and a geometric albedo of 0.070 ± 0.006. The
χ2-test reveals a strong preference for a retrograde sense
of rotation with a spin-axis orientation of
λecl = 73°,
βecl = −62° and
Psid = 7.63 ± 0.01 h. The most likely thermal inertia ranges
between 200 and 600 J m-2 s-0.5 K-1, about a factor of
2 lower than the value for 25143 Itokawa. This indicates that the surface lies somewhere
between a thick-dust regolith and a rock/boulder/cm-sized, gravel-dominated surface like
that of 25143 Itokawa. Our analysis represents the first time that shape and spin-vector
information has been derived from a combined data set of visual lightcurves (reflected
light) and mid-infrared photometry and spectroscopy (thermal emission)