20 research outputs found
BEER analysis of Kepler and CoRoT light curves. III. Spectroscopic confirmation of seventy new beaming binaries discovered in CoRoT light curves
(abridged for arXiv) The BEER algorithm searches stellar light curves for the
BEaming, Ellipsoidal, and Reflection photometric modulations that are caused by
a short-period companion. Applying the search to the first five long-run center
CoRoT fields, we identified non-eclipsing candidates with periodic flux
amplitudes of mmag. Optimizing the Anglo-Australian-Telescope pointing
coordinates and the AAOmega fiber-allocations with dedicated softwares, we
acquired six spectra for candidates and seven spectra for another
candidates in a seven-night campaign. Analysis of the red-arm AAOmega spectra,
which covered the range of , yielded a radial-velocity
precision of km/s. Spectra containing lines of more than one star were
analyzed with the two-dimensional correlation algorithm TODCOR. The measured
radial velocities confirmed the binarity of seventy of the BEER candidates
single-line binaries, double-line binaries, and diluted binaries. We
show that red giants introduce a major source of false candidates and
demonstrate a way to improve BEER's performance in extracting higher fidelity
samples from future searches of CoRoT light curves. The periods of the
confirmed binaries span a range of days and show a rise in the number
of binaries per log toward longer periods. The estimated mass ratios
of the double-line binaries and the mass ratios assigned to the single-line
binaries, assuming an isotropic inclination distribution, span a range of
. On the low-mass end, we have detected two brown-dwarf candidates on a
day period orbit. This is the first time non-eclipsing beaming binaries
are detected in CoRoT data, and we estimate that such binaries can be
detected in the CoRoT long-run light curves.Comment: 28 pages, 15 figures, and 11 tables. Accepted for publication in A&
Seventy new non-eclipsing BEER binaries discovered in CoRoT lightcurves and confirmed by RVs from AAOmega
We applied the BEER algorithm to the CoRoT lightcurves from the first five
LRc fields and identified non-eclipsing BEER candidates with periodic
lightcurve modulations and amplitudes of mmag. Medium-resolution
spectra of candidates were obtained in a seven-night AAOmega
radial-velocity (RV) campaign, with a precision of km/s. The RVs
confirmed the binarity of of the BEER candidates, with periods of
days.Comment: 2 pages, 1 figure, to appear in the CoRoT Symposium 3, Kepler KASC-7
joint meeting, EPJ Web of Conference
Features of Gaia DR3 Spectroscopic Binaries I. Tidal circularization of Main-Sequence Stars
Previous studies pointed out that many observed samples of short-period
binaries display a cutoff period, , such that almost all binaries
with periods shorter than have circular orbits. This feature is
probably due to long-term circularization processes induced by tidal
interaction between the two stars of each binary. It seemed as if coeval
main-sequence (MS) samples of open clusters display that depends
on the sample age. Using the unprecedentedly large sample of MS spectroscopic
orbits recently released by we have found that the does not depend on the stellar age but, instead, varies with stellar
temperature, decreasing linearly from day at K to
day at K. was derived by a new algorithm that
relied on clear upper envelopes displayed in the period-eccentricity diagrams.
Our determines both the border between the circular and eccentric
binaries and the location of the upper envelope. The results are inconsistent
with the theory which assumes circularization occurs during the stellar MS
phase, a theory that was adopted by many studies. The circularization has
probably taken place at the pre-main-sequence phase, as suggested already in
1989 by Zahn and Bouchet, and later by Khaluillin and Khaluillina in 2011. Our
results suggest that the weak dependence of on the cluster age is
not significant, and/or might be due to the different temperatures of the
samples. If indeed true, this has far-reaching implications for the theory of
binary and exoplanet circularization, synchronization, and alignment.Comment: 13 pages, 12 figures, 2 tables. Accepted for publication in MNRA
BEER analysis of Kepler and CoRoT light curves: I. Discovery of Kepler-76b: A hot Jupiter with evidence for superrotation
We present the first case in which the BEER algorithm identified a hot
Jupiter in the Kepler light curve, and its reality was confirmed by orbital
solutions based on follow-up spectroscopy. The companion Kepler-76b was
identified by the BEER algorithm, which detected the BEaming (sometimes called
Doppler boosting) effect together with the Ellipsoidal and Reflection/emission
modulations (BEER), at an orbital period of 1.54 days, suggesting a planetary
companion orbiting the 13.3 mag F star. Further investigation revealed that
this star appeared in the Kepler eclipsing binary catalog with estimated
primary and secondary eclipse depths of 5e-3 and 1e-4 respectively.
Spectroscopic radial-velocity follow-up observations with TRES and SOPHIE
confirmed Kepler-76b as a transiting 2.0+/-0.26 Mjup hot Jupiter. The mass of a
transiting planet can be estimated from either the beaming or the ellipsoidal
amplitude. The ellipsoidal-based mass estimate of Kepler-76b is consistent with
the spectroscopically measured mass while the beaming-based estimate is
significantly inflated. We explain this apparent discrepancy as evidence for
the superrotation phenomenon, which involves eastward displacement of the
hottest atmospheric spot of a tidally-locked planet by an equatorial
super-rotating jet stream. This phenomenon was previously observed only for HD
189733b in the infrared. We show that a phase shift of 10.3+/-2.0 degrees of
the planet reflection/emission modulation, due to superrotation, explains the
apparently inflated beaming modulation, resolving the ellipsoidal/beaming
amplitude discrepancy. Kepler-76b is one of very few confirmed planets in the
Kepler light curves that show BEER modulations and the first to show
superrotation evidence in the Kepler band. Its discovery illustrates for the
first time the ability of the BEER algorithm to detect short-period planets and
brown dwarfs.Comment: 28 pages, 6 tables and 7 figures. Planet name changed to Kepler-76b.
Accepted for publication in the Astrophysical Journa
Triage of the Gaia astrometric orbits. I. A sample of binaries with probable compact companions
In preparation for the release of the astrometric orbits of Gaia, Shahaf et
al. (2019) proposed a triage technique to identify astrometric binaries with
compact companions based on their astrometric semi-major axis, parallax, and
primary mass. The technique requires the knowledge of the appropriate
mass-luminosity relation to rule out single or close-binary main-sequence
companions. The recent publication of the Gaia DR3 astrometric orbits used a
schematic version of this approach, identifying 735 astrometric binaries that
might have compact companions. In this communication, we return to the triage
of the DR3 astrometric binaries with more careful analysis, estimating the
probability for its astrometric secondary to be a compact object or a
main-sequence close binary. We compile a sample of 177 systems with
highly-probable non-luminous massive companions, which is smaller but cleaner
than the sample reported in Gaia DR3. The new sample includes 8 candidates to
be black-hole systems with compact-object masses larger than 2.4 . The
orbital-eccentricitysecondary-mass diagram of the other 169 systems suggests
a tentative separation between the white-dwarf and the neutron-star binaries.
Most white-dwarf binaries are characterized by small eccentricities of about
0.1 and masses of 0.6 , while the neutron star binaries display
typical eccentricities of 0.4 and masses of 1.3 .Comment: Submitted to MNRAS; 12 pages, 13 figure