179 research outputs found
II.3 Exposure based algorithm for removing systematics out of the CoRoT light curves
This book is dedicated to all the people interested in the CoRoT mission and the beautiful data that were delivered during its six year duration. Either amateurs, professional, young or senior researchers, they will find treasures not only at the time of this publication but also in the future twenty or thirty years. It presents the data in their final version, explains how they have been obtained, how to handle them, describes the tools necessary to understand them, and where to find them. It also highlights the most striking first results obtained up to now. CoRoT has opened several unexpected directions of research and certainly new ones still to be discovered
Kepler KOI-13.01 - Detection of beaming and ellipsoidal modulations pointing to a massive hot Jupiter
KOI-13 was presented by the Kepler team as a candidate for having a giant
planet - KOI-13.01, with orbital period of 1.7 d and transit depth of ~0.8%. We
have analyzed the Kepler Q2 data of KOI-13, which was publicly available at the
time of the submission of this paper, and derived the amplitudes of the
beaming, ellipsoidal and reflection modulations: 8.6 +/- 1.1, 66.8 +/- 1.6 and
72.0 +/- 1.5 ppm (parts per million), respectively. After the paper was
submitted, Q3 data were released, so we repeated the analysis with the newly
available light curve. The results of the two quarters were quite similar. From
the amplitude of the beaming modulation we derived a mass of 10 +/- 2 M_Jup for
the secondary, suggesting that KOI-13.01 was a massive planet, with one of the
largest known radii. We also found in the data a periodicity of unknown origin
with a period of 1.0595 d and a peak-to-peak modulation of ~60 ppm. The light
curve of Q3 revealed a few more small-amplitude periodicities with similar
frequencies. It seemed as if the secondary occultation of KOI-13 was slightly
deeper than the reflection peak-to-peak modulation by 16.8 +/- 4.5 ppm. If
real, this small difference was a measure of the thermal emission from the
night side of KOI-13.01. We estimated the effective temperature to be 2600 +/-
150 K, using a simplistic black-body emissivity approximation. We then derived
the planetary geometrical and Bond albedos as a function of the day-side
temperature. Our analysis suggested that the Bond albedo of KOI-13.01 might be
substantially larger than the geometrical albedo.Comment: 15 pages, 8 figures, accepted for publication in Astronomy and
Astrophysic
Physics of Eclipsing Binaries: Modelling in the new era of ultra-high precision photometry
Recent ultra-high precision observations of eclipsing binaries, especially data acquired by the Kepler satellite, have made accurate light curve modelling increasingly challenging but also more rewarding. In this contribution, we discuss low-amplitude signals in light curves that can now be used to derive physical information about eclipsing binaries but that were unaccessible before the Kepler era. A notable example is the detection of Doppler beaming, which leads to an increase in flux when a star moves towards the satellite and a decrease in flux when it moves away. Similarly, Rømer delays, or light travel time effects, also have to taken into account when modelling the supreme quality data that is now available. The detection of offsets between primary and secondary eclipse phases in binaries with extreme mass ratios, and the observation of Rømer delays in the signals of pulsators in binary stars, have allowed us to determine the orbits of several binaries without the need for spectroscopy. A third example of a small-scale effect that has to be taken into account when modelling specific binary systems, are lensing effects. A new binary light curve modelling code, PHOEBE 2.0, that takes all these effect into account is currently being developed
CoRoT 101186644: A transiting low-mass dense M-dwarf on an eccentric 20.7-day period orbit around a late F-star
We present the study of the CoRoT transiting planet candidate 101186644, also
named LRc01_E1_4780. Analysis of the CoRoT lightcurve and the HARPS
spectroscopic follow-up observations of this faint (m_V = 16) candidate
revealed an eclipsing binary composed of a late F-type primary (T_eff = 6090
+/- 200 K) and a low-mass, dense late M-dwarf secondary on an eccentric (e =
0.4) orbit with a period of ~20.7 days. The M-dwarf has a mass of 0.096 +/-
0.011 M_Sun, and a radius of 0.104 +0.026/-0.006 R_Sun, which possibly makes it
the smallest and densest late M-dwarf reported so far. Unlike the claim that
theoretical models predict radii that are 5%-15% smaller than measured for
low-mass stars, this one seems to have a radius that is consistent and might
even be below the radius predicted by theoretical models.Comment: Accepted for publication in Astronomy & Astrophysics, 8 pages, 10
figure
A massive exoplanet candidate around KOI-13: Independent confirmation by ellipsoidal variations
We present an analysis of the KOI-13.01 candidate exoplanet system included
in the September 2011 Kepler data release. The host star is a known and
relatively bright visual binary with a separation
significantly smaller (0.8 arcsec) than the size of a Kepler pixel (4 arcsec
per pixel). The Kepler light curve shows both primary and secondary eclipses,
as well as significant out-of-eclipse light curve variations. We confirm that
the transit occurs round the brighter of the two stars. We model the relative
contributions from (i) thermal emission from the companion, (ii) planetary
reflected light, (iii) Doppler beaming, and (iv) ellipsoidal variations in the
host-star arising from the tidal distortion of the host star by its companion.
Our analysis, based on the light curve alone, enables us to constrain the mass
of the KOI-13.01 companion to be and thus
demonstrates that the transiting companion is a planet (rather than a brown
dwarf which was recently proposed by \cite{b7}). The high temperature of the
host star (Spectral Type A5-7V, K), combined with the
proximity of its companion KOI-13.01, may make it one of the hottest exoplanets
known, with a detectable thermal contribution to the light curve even in the
Kepler optical passband. However, the single passband of the Kepler light curve
does not enable us to unambiguously distinguish between the thermal and
reflected components of the planetary emission. Infrared observations may help
to break the degeneracy, while radial velocity follow-up with 100
m s precision should confirm the mass of the planet.Comment: 7 pages, 5 figure
Detection of the ellipsoidal and the relativistic beaming effects in the CoRoT-3 lightcurve
CoRoT-3b is a 22 Jupiter-mass massive-planet/brown-dwarf object, orbiting an
F3-star with a period of 4.3 days. We analyzed the out-of-transit CoRoT-3
red-channel lightcurve obtained by the CoRoT mission and detected the
ellipsoidal modulation, with half the orbital period and amplitude of 59+/-9
ppm (parts per million) and the relativistic beaming effect, with the orbital
period and an amplitude of 27+/-9 ppm. Phases and amplitudes of both
modulations were consistent with our theoretical approximation.Comment: Published in Astronomy & Astrophysics. 5 pages, 2 figure
Photometric detection of non-transiting short-period low-mass companions through the beaming, ellipsoidal and reflection effects in Kepler and CoRoT lightcurves
We present a simple algorithm, BEER, to search for a combination of the
BEaming, Ellipsoidal and the Reflection/heating periodic modulations, induced
by short-period non-transiting low-mass companions. The beaming effect is due
to the increase (decrease) of the brightness of any light source approaching
(receding from) the observer. To first order, the beaming and the
reflection/heating effects modulate the stellar brightness at the orbital
period, with phases separated by a quarter of a period, whereas the ellipsoidal
effect is modulated with the orbital first harmonic. The phase and harmonic
differences between the three modulations allow the algorithm to search for a
combination of the three effects and identify stellar candidates for low-mass
companions. The paper presents the algorithm, including an assignment of a
likelihood factor to any possible detection, based on the expected ratio of the
beaming and ellipsoidal effects, given an order-of-magnitude estimate of the
three effects. As predicted by Loeb & Gaudi (2003) and Zucker, Mazeh &
Alexander (2007), the Kepler and the CoRoT lightcurves are precise enough to
allow detection of massive planets and brown-dwarf/low-mass-stellar companions
with orbital period up to 10-30 days. To demonstrate the feasibility of the
algorithm, we bring two examples of candidates found in the first 33 days of
the Q1 Kepler lightcurves. Although we used relatively short timespan, the
lightcurves were precise enough to enable the detection of periodic effects
with amplitudes as small as one part in 10,000 of the stellar flux.Comment: 19 pages, 6 figures and 1 table; Accepted for publication in MNRA
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