577 research outputs found
The EBLM project. II. A very hot, low-mass M dwarf in an eccentric and long period eclipsing binary system from SuperWASP
In this paper, we derive the fundamental properties of
1SWASPJ011351.29+314909.7 (J0113+31), a metal-poor (-0.40 +/- 0.04 dex),
eclipsing binary in an eccentric orbit (~0.3) with an orbital period of ~14.277
d. Eclipsing M dwarfs orbiting solar-type stars (EBLMs), like J0113+31, have
been identified from WASP light curves and follow-up spectroscopy in the course
of the transiting planet search. We present the first binary of the EBLM sample
to be fully analysed, and thus, define here the methodology. The primary
component with a mass of 0.945 +/- 0.045 Msun has a large radius (1.378 +/-
0.058 Rsun) indicating that the system is quite old, ~9.5 Gyr. The M-dwarf
secondary mass of 0.186 +/- 0.010 Msun and radius of 0.209 +/- 0.011 Rsun are
fully consistent with stellar evolutionary models. However, from the
near-infrared secondary eclipse light curve, the M dwarf is found to have an
effective temperature of 3922 +/- 42 K, which is ~600 K hotter than predicted
by theoretical models. We discuss different scenarios to explain this
temperature discrepancy. The case of J0113+31 for which we can measure mass,
radius, temperature and metallicity, highlights the importance of deriving
mass, radius and temperature as a function of metallicity for M dwarfs to
better understand the lowest mass stars. The EBLM Project will define the
relationship between mass, radius, temperature and metallicity for M dwarfs
providing important empirical constraints at the bottom of the main sequence.Comment: 13 pages, 7 figures. Accepted for publication in A&
Magnetic Fields in Earth-like Exoplanets and Implications for Habitability around M-dwarfs
We present estimations of dipolar magnetic moments for terrestrial exoplanets
using the Olson & Christiansen (2006) scaling law and assuming their interior
structure is similar to Earth. We find that the dipolar moment of fast rotating
planets (where the Coriolis force dominates convection in the core), may amount
up to ~80 times the magnetic moment of Earth, M_Earth, for at least part of the
planets' lifetime. For very slow rotating planets (where the force of inertia
dominates), the dipolar magnetic moment only reaches up to ~1.5 M_Earth.
Applying our calculations to currently confirmed rocky exoplanets, we find that
CoRoT-7b, Kepler-10b and 55 Cnc e can sustain dynamos up to ~ 18, 15 and 13
M_Earth, respectively. Our results also indicate that the magnetic moment of
rocky exoplanets not only depends on their rotation rate, but also on their
formation history, thermal state, age and composition, as well as the geometry
of the field. These results apply to all rocky planets, but have important
implications for the particular case of exoplanets in the Habitable Zone of
M-dwarfs.Comment: 4 pages, 1 figure, to appear in the Origins 2011 ISSOL & IAU Meeting
Conference Proceedings, Montpellier, France, July 3-8 201
A transiting companion to the eclipsing binary KIC002856960
We present an early result from an automated search of Kepler eclipsing
binary systems for circumbinary companions. An intriguing tertiary signal has
been discovered in the short period eclipsing binary KIC002856960. This third
body leads to transit-like features in the light curve occurring every 204.2
days, while the two other components of the system display eclipses on a 6.2
hour period. The variations due to the tertiary body last for a duration of
\sim1.26 days, or 4.9 binary orbital periods. During each crossing of the
binary orbit with the tertiary body, multiple individual transits are observed
as the close binary stars repeatedly move in and out of alignment with the
tertiary object. We are at this stage unable to distinguish between a planetary
companion to a close eclipsing binary, or a hierarchical triply eclipsing
system of three stars. Both possibilities are explored, and the light curves
presented.Comment: Accepted into A&A Letters (5 pages & 3 figures
ANAIS status report
We report the status of the ANAIS (Annual modulation with NAI Scintillators) experiment focusing on the developments towards the improvement of the background level of our detectors and the reduction of the energy threshold
Variable order Mittag-Leffler fractional operators on isolated time scales and application to the calculus of variations
We introduce new fractional operators of variable order on isolated time
scales with Mittag-Leffler kernels. This allows a general formulation of a
class of fractional variational problems involving variable-order difference
operators. Main results give fractional integration by parts formulas and
necessary optimality conditions of Euler-Lagrange type.Comment: This is a preprint of a paper whose final and definite form is with
Springe
Solar axion search with the CAST experiment
The CAST (CERN Axion Solar Telescope) experiment is searching for solar
axions by their conversion into photons inside the magnet pipe of an LHC
dipole. The analysis of the data recorded during the first phase of the
experiment with vacuum in the magnet pipes has resulted in the most restrictive
experimental limit on the coupling constant of axions to photons. In the second
phase, CAST is operating with a buffer gas inside the magnet pipes in order to
extent the sensitivity of the experiment to higher axion masses. We will
present the first results on the data taking as well as the
system upgrades that have been operated in the last year in order to adapt the
experiment for the data taking. Expected sensitivities on the
coupling constant of axions to photons will be given for the recent run just started in March 2008.Comment: Proceedings of the ICHEP 2008 conferenc
YSOVAR: Mid-infrared Variability Among YSOs in the Star Formation Region GGD 12-15
S. J. Wolk, et al., “YSOVAR: Mid-infrared Variability Among YSOs in the Star Formation Region GGD 12-15”, The Astronomical Journal, Vol. 150(5), October 2015. © 2015. The American Astronomical Society. All rights reserved.We present an IR-monitoring survey with the Space Telescope of the star forming region GGD 12-15. Over 1000 objects were monitored including about 350 objects within the central 5 arcminutes which is found to be especially dense in cluster members. The monitoring took place over 38 days and is part of the Young Stellar Object VARiability (YSOVAR) project. The region was also the subject of a contemporaneous 67ks observation. The field includes 119 previously identified pre-main sequence star candidates. X-rays are detected from 164 objects, 90 of which are identified with cluster members. Overall, we find that about half the objects in the central 5 arcminutes are young stellar objects based on a combination of their spectral energy distribution, IR variability and X-ray emission. Most of the stars with IR excess relative to a photosphere show large amplitude (>0.1 mag) mid-IR variability. There are 39 periodic sources, all but one of these is found to be a cluster member. Almost half of the periodic sources do not show IR excesses. Overall, more than 85% of the Class I, flat spectrum, and Class II sources are found to vary. The amplitude of the variability is larger in more embedded young stellar objects. Most of the Class~I/II objects exhibit redder colors in a fainter state, compatible with time-variable extinction. A few become bluer when fainter, which can be explained with significant changes in the structure of the inner disk. A search for changes in the IR due to X-ray events is carried out, but the low number of flares prevented an analysis of the direct impact of X-ray flares on the IR lightcurves. However, we find that X-ray detected Class II sources have longer timescales for change in the mid-IR than a similar set of non-X-ray detected Class IIs.Peer reviewe
Search for low Energy solar Axions with CAST
We have started the development of a detector system, sensitive to single
photons in the eV energy range, to be suitably coupled to one of the CAST
magnet ports. This system should open to CAST a window on possible detection of
low energy Axion Like Particles emitted by the sun. Preliminary tests have
involved a cooled photomultiplier tube coupled to the CAST magnet via a
Galileian telescope and a switched 40 m long optical fiber. This system has
reached the limit background level of the detector alone in ideal conditions,
and two solar tracking runs have been performed with it at CAST. Such a
measurement has never been done before with an axion helioscope. We will
present results from these runs and briefly discuss future detector
developments.Comment: Paper submitted to the proceedings of the "4th Patras Workshop on
Axions, WIMPs and WISPs", DESY, Hamburg Site - Germany, 18-21 June 2008.
Author affiliations are reported on the title page of the paper. In version
2: 1 affiliation change, 3 references adde
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