725 research outputs found
KELT-10b: The First Transiting Exoplanet from the KELT-South Survey -- A Hot Sub-Jupiter Transiting a V = 10.7 Early G-Star
We report the discovery of KELT-10b, the first transiting exoplanet
discovered using the KELT-South telescope. KELT-10b is a highly inflated
sub-Jupiter mass planet transiting a relatively bright star (TYC
8378-64-1), with T = K, =
and [Fe/H] = , an inferred mass
M = M and radius R =
R. The planet has a radius R =
R and mass M =
M. The planet has an eccentricity consistent with zero and a semi-major
axis = AU. The best fitting linear
ephemeris is = 2457066.720450.00027 BJD and P =
4.16627390.0000063 days. This planet joins a group of highly inflated
transiting exoplanets with a radius much larger and a mass much less than those
of Jupiter. The planet, which boasts deep transits of 1.4%, has a relatively
high equilibrium temperature of T = K, assuming zero
albedo and perfect heat redistribution. KELT-10b receives an estimated
insolation of 10 erg s cm,
which places it far above the insolation threshold above which hot Jupiters
exhibit increasing amounts of radius inflation. Evolutionary analysis of the
host star suggests that KELT-10b is unlikely to survive beyond the current
subgiant phase, due to a concomitant in-spiral of the planet over the next
1 Gyr. The planet transits a relatively bright star and exhibits the
third largest transit depth of all transiting exoplanets with V 11 in the
southern hemisphere, making it a promising candidate for future atmospheric
characterization studies.Comment: 20 pages, 13 figures, 7 tables, accepted for publication in MNRA
Implementation and testing of the first prompt search for gravitational wave transients with electromagnetic counterparts
Aims. A transient astrophysical event observed in both gravitational wave
(GW) and electromagnetic (EM) channels would yield rich scientific rewards. A
first program initiating EM follow-ups to possible transient GW events has been
developed and exercised by the LIGO and Virgo community in association with
several partners. In this paper, we describe and evaluate the methods used to
promptly identify and localize GW event candidates and to request images of
targeted sky locations.
Methods. During two observing periods (Dec 17 2009 to Jan 8 2010 and Sep 2 to
Oct 20 2010), a low-latency analysis pipeline was used to identify GW event
candidates and to reconstruct maps of possible sky locations. A catalog of
nearby galaxies and Milky Way globular clusters was used to select the most
promising sky positions to be imaged, and this directional information was
delivered to EM observatories with time lags of about thirty minutes. A Monte
Carlo simulation has been used to evaluate the low-latency GW pipeline's
ability to reconstruct source positions correctly.
Results. For signals near the detection threshold, our low-latency algorithms
often localized simulated GW burst signals to tens of square degrees, while
neutron star/neutron star inspirals and neutron star/black hole inspirals were
localized to a few hundred square degrees. Localization precision improves for
moderately stronger signals. The correct sky location of signals well above
threshold and originating from nearby galaxies may be observed with ~50% or
better probability with a few pointings of wide-field telescopes.Comment: 17 pages. This version (v2) includes two tables and 1 section not
included in v1. Accepted for publication in Astronomy & Astrophysic
System description and first light-curves of HAT, an autonomous observatory for variability search
Having been operational at Kitt Peak for more than a year, the prototype of
the Hungarian Automated Telescope (HAT-1) has been used for all-sky variability
search of the northern hemisphere. The small autonomous observatory is
recording brightness of stars in the range of I~6--13m with a telephoto lens
and its 9x9 degree field of view, yielding a data rate of ~10^6 photometric
measurements per night. We give brief hardware and software description of the
system, controlled by a single PC running RealTime Linux operating system. We
overview site-specific details, and quantify the astrometric and photometric
capabilities of HAT. As a demonstration of system performance we give a sample
of 60 short period variables in a single selected field, all bright, with I <
13m, of which only 14 were known before. Depending on the observing strategy,
search for extrasolar planet transits is also a feasible observing program. We
conclude with a short discussion on future directions. Further information can
be found at the HAT homepage: http://www-cfa.harvard.edu/~gbakos/HAT/Comment: Submitted to PASP, 18 pages, 8 figures. See
http://www-cfa.harvard.edu/~gbakos/HAT/Publ/ for more information and
hi-resolution figure
The contribution of the major planet search surveys to EChO target selection
The EChO core science will be based on a three tier survey, each with
increasing sensitivity, in order to study the population of exo-planets from
super-Earths to Jupiter-like planets, in the very hot to temperate zones
(temperatures of 300 K - 3000 K) of F to M-type host stars. To achieve a
meaningful outcome an accurate selection of the target sample is needed. In
this paper we analyse the targets, suitable for EChO observations, expected to
result from a sample of present and forthcoming detection surveys. Exoplanets
currently known are already sufficient to provide a large and diverse sample.
However we expect the results from these surveys to increase the sample of
smaller planets that will allow us to optimize the EChO sample selection.Comment: Submitted to Experimental Astronom
Tracking control for a cascade perturbed control system using the active disturbance rejection paradigm
In this paper the stability of a closed-loop cascade control system in the
trajectory tracking task is addressed. The considered plant consists of
underlying second-order fully actuated perturbed dynamics and the first order
system which describes dynamics of the input. The main theoretical result
presented in the paper concerns stability conditions formulated based on the
Lyapunov analysis for the cascade control structure taking advantage of the
active rejection disturbance approach. In particular, limitations imposed on a
feasible set of an observer bandwidth are discussed. In order to illustrate
characteristics of the closed-loop control system simulation results are
presented. Furthermore, the controller is verified experimentally using a
two-axis telescope mount. The obtained results confirm that the considered
control strategy can be efficiently applied for mechanical systems when a high
tracking precision is required.Comment: 17 pages, 8 figures, 2 table
Remote Access Observatories in Low Earth Orbit -A Low-Cost Concept for a Small Scientific Spacecraft
In parallel with the evolution of large observatory spacecraft such as the Einstein, Copernicus, and IUE, and the yet-to-be-Iaunched Hubble Space Telescope and Gamma Ray Observatory, Increasingly large ground telescopes are in construction which will allow ground astronomy to compete favorably with elaborate and expensive space systems in the quest for new discoveries. Sometimes overlooked in this pursuit of new discoveries, with the limited observational time on the space Instruments, or the oversubscribed large ground Instruments, Is the recent development of smaller, low-cost robotic ground observatories designed for routine - but vital - collection of synoptic data. High-quality stellar observations are now being made by exploitation of new computer and detector technologies in unattended remote ground observatories, typically by modest aperture Instruments tailored to the Job. These Instruments operate in modes similar to those employed in the observatory spacecraft. Recent developments In the small satellite technology, some being reported at this conference, allow a reduced cost of payload delivery Into orbit and suggest that another look Is deserved at the 1960s\u27 concept of small astronomical satellites, which would be operable by simple command systems to conduct monitoring of variable, flare, and cataclysmic stars, perhaps limited only to precision filter photometry or simple Imaging In wavelengths not accessible from the ground. These would allow conduct of bread-and-butter astronomy at and accuracies wavelengths available only In space on objects Identified by the larger research Instruments, undertaking science too costly to pursue over long periods with multi-billion dollar systems. This paper will explore small spacecraft provided with low-cost attitude systems (LCAS) for stabilization, modest telescope optics, and low-power communications and spacecraft computer sub-systems which could perform autonomous celestial acquisitions and photometric data collection
The Mass-Radius(-Rotation?) Relation for Low-Mass Stars
The fundamental properties of low-mass stars are not as well understood as
those of their more massive counterparts. The best method for constraining
these properties, especially masses and radii, is to study eclipsing binary
systems, but only a small number of late-type (M0 or later) systems have been
identified and well-characterized to date. We present the discovery and
characterization of six new M dwarf eclipsing binary systems. The twelve stars
in these eclipsing systems have masses spanning 0.38-0.59 Msun and orbital
periods of 0.6--1.7 days, with typical uncertainties of ~0.3% in mass and
0.5--2.0% in radius. Combined with six known systems with high-precision
measurements, our results reveal an intriguing trend in the low-mass regime.
For stars with M=0.35-0.80 Msun, components in short-period binary systems (P<1
day; 12 stars) have radii which are inflated by up to 10% (mean=4.8+/-1.0%)
with respect to evolutionary models for low-mass main-sequence stars, whereas
components in longer-period systems (>1.5 days; 12 stars) tend to have smaller
radii (mean=1.7+/-0.7%). This trend supports the hypothesis that short-period
systems are inflated by the influence of the close companion, most likely
because they are tidally locked into very high rotation speeds that enhance
activity and inhibit convection. In summary, very close binary systems are not
representative of typical M dwarfs, but our results for longer-period systems
indicate that the evolutionary models are broadly valid in the M~0.35-0.80 Msun
regime.Comment: Accepted to ApJ; 21 pages, 10 figures, 8 tables in emulateapj format.
The full contents of Table 4 are included in the submission as tab4.tx
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