38 research outputs found
Automated code for the selection of targets to be observed with the SAINT-EX telescope
In this contribution, we present the main characteristics and describe the functioning of the code developed in python language to automatically build the list of objects that are nightly observed in queue mode with the 1-m SAINT-EX telescope.Fil: Petrucci, Romina Paola. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gómez Maqueo Chew, Yilen. Instituto de Astronomia; México. Universidad Nacional Autónoma de México; Méxic
Automated code for the selection of targets to be observed with the SAINT-EX telescope
In this contribution, we present the main characteristics and describe the functioning of the code developed in python language to automatically build the list of objects that are nightly observed in queue mode with the 1-m SAINT-EX telescope.Fil: Petrucci, Romina Paola. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Departamento de Astrofísica Estelar; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gómez Maqueo Chew, Yilen. Instituto de Astronomia; México. Universidad Nacional Autónoma de México; Méxic
Apsidal Motion of the Massive, Benchmark Eclipsing Binary V578 Mon
V578 Mon is a system of two early B-type stars in the Rosette Nebula
star-forming region (NGC 2244), and is one of only nine eclipsing binaries with
component masses greater than 10 M\odot whose physical parameters have been
determined with an accuracy of better than 3%. It is therefore a benchmark
system for evolutionary and stellar structure models of newly formed massive
stars. Combining our multi-band light curves spanning 40 yr with previous light
curve data from the literature, we fit a model light curve that for the first
time includes the effects of apsidal motion of the system. We measure an
apsidal period of 33.48+0.10-0.06 yr. As a consequence of incorporating the
apsidal motion into the modeling of the system's orbital parameters, we
determine an updated eccentricity of e = 0.07755+0.00022-0.00027, which differs
significantly from the value previously reported in the literature. Evidently,
the inclusion of apsidal motion in the light curve modeling significantly
affects the eccentricity determination. Incorporating these key parameters into
a comprehensive model of the system's physical parameters-including internal
structure constraints- will bring V578 Mon to the next level of benchmark
precision and utility.Comment: 17 pages, 7 figures, to appear in the Astronomical Journa
Near-Infrared Light Curves of the Brown Dwarf Eclipsing Binary 2MASS J05352184-0546085: Can Spots Explain the Temperature Reversal?
We present the JHKs light curves for the double-lined eclipsing binary 2MASS
J05352184-0546085, in which both components are brown dwarfs. We analyze these
light curves with the published Ic-band light curve and radial velocities to
provide refined measurements of the system's physical parameters. The component
masses and radii are here determined with an accuracy of ~6.5% and ~1.5%,
respectively. We confirm the previous surprising finding that the primary brown
dwarf has a cooler effective temperature than its companion. Next, we perform a
detailed study of the variations in the out-of-eclipse phases of the light
curves to ascertain the properties of any inhomogeneities on the surfaces of
the brown dwarfs. Our analysis reveals two low-amplitude periodic signals, one
attributable to the rotation of the primary (with a period of 3.293+/-0.001 d)
and the other to that of the secondary (14.05+/-0.05 d). Finally, we explore
the effects on the derived physical parameters of the system when spots are
included in the modeling. The observed low-amplitude rotational modulations are
well fit by cool spots covering a small fraction of their surfaces. To mimic
the observed ~200 K suppression of the primary's temperature, our model
requires that the primary possess a very large spot coverage fraction of ~65%.
Altogether, a spot configuration in which the primary is heavily spotted while
the secondary is lightly spotted can explain the apparent temperature reversal
and can bring the temperatures of the brown dwarfs into agreement with the
predictions of theoretical models.Comment: Accepted for publication in The Astrophysical Journal; 13 pages, 8
figures, 6 tables. Updated parameter uncertaintie
Luminosity Discrepancy in the Equal-Mass, Pre--Main Sequence Eclipsing Binary Par 1802: Non-Coevality or Tidal Heating?
Parenago 1802, a member of the ~1 Myr Orion Nebula Cluster, is a
double-lined, detached eclipsing binary in a 4.674 d orbit, with equal-mass
components (M_2/M_1 = 0.985 \pm 0.029). Here we present extensive VIcJHKs light
curves spanning ~15 yr, as well as a Keck/HIRES optical spectrum. The light
curves evince a third light source that is variable with a period of 0.73 d,
and is also manifested in the high-resolution spectrum, strongly indicating the
presence of a third star in the system, probably a rapidly rotating classical T
Tauri star. We incorporate this third light into our radial velocity and light
curve modeling of the eclipsing pair, measuring accurate masses (M_1 = 0.391
\pm 0.032, M_2 = 0.385 \pm 0.032 M\odot), radii (R_1 = 1.73 \pm 0.02, R_2 =
1.62 \pm 0.02 R\odot), and temperature ratio (T_1/T_2 = 1.0924 \pm 0.0017).
Thus the radii of the eclipsing stars differ by 6.9 \pm 0.8%, the temperatures
differ by 9.2 \pm 0.2%, and consequently the luminosities differ by 62 \pm 3%,
despite having masses equal to within 3%. This could be indicative of an age
difference of ~3x10^5 yr between the two eclipsing stars, perhaps a vestige of
the binary formation history. We find that the eclipsing pair is in an orbit
that has not yet fully circularized, e = 0.0166 \pm 0.003. In addition, we
measure the rotation rate of the eclipsing stars to be 4.629 \pm 0.006 d; they
rotate slightly faster than their 4.674 d orbit. The non-zero eccentricity and
super-synchronous rotation suggest that the eclipsing pair should be tidally
interacting, so we calculate the tidal history of the system according to
different tidal evolution theories. We find that tidal heating effects can
explain the observed luminosity difference of the eclipsing pair, providing an
alternative to the previously suggested age difference.Comment: 49 pages, 16 figures, 11 tables. Accepted for publication to Ap
Close companions around young stars
Multiplicity is a fundamental property that is set early during stellar
lifetimes, and it is a stringent probe of the physics of star formation. The
distribution of close companions around young stars is still poorly constrained
by observations. We present an analysis of stellar multiplicity derived from
APOGEE-2 spectra obtained in targeted observations of nearby star-forming
regions. This is the largest homogeneously observed sample of high-resolution
spectra of young stars. We developed an autonomous method to identify double
lined spectroscopic binaries (SB2s). Out of 5007 sources spanning the mass
range of 0.05--1.5 \msun, we find 399 binaries, including both RV
variables and SB2s. The mass ratio distribution of SB2s is consistent with a
uniform for . The period
distribution is consistent with what has been observed in close binaries (
AU) in the evolved populations. Three systems are found to have 0.1,
with a companion located within the brown dwarf desert. There are not any
strong trends in the multiplicity fraction (MF) as a function of cluster age
from 1 to 100 Myr. There is a weak dependence on stellar density, with
companions being most numerous at stars/pc, and
decreasing in more diffuse regions. Finally, disk-bearing sources are deficient
in SB2s (but not RV variables) by a factor of 2; this deficit is
recovered by the systems without disks. This may indicate a quick dispersal of
disk material in short-period equal mass systems that is less effective in
binaries with lower .Comment: 25 pages, 20 figures. Accepted to A
The EBLM project : III. A Saturn-size low-mass star at the hydrogen-burning limit
This work was partially supported by a grant from the Simons Foundation (PI Queloz, grant number 327127).We report the discovery of an eclipsing binary system with mass-ratio q ∼ 0.07. After identifying a periodic photometric signal received by WASP, we obtained CORALIE spectroscopic radial velocities and follow-up light curves with the Euler and TRAPPIST telescopes. From a joint fit of these data we determine that EBLM J0555-57 consists of a sun-like primary star that is eclipsed by a low-mass companion, on a weakly eccentric 7.8-day orbit. Using a mass estimate for the primary star derived from stellar models, we determine a companion mass of 85 ± 4 MJup (0.081 M⊙) and a radius of 0.84+ 0.14 -0.04RJup (0.084 R⊙) that is comparable to that of Saturn. EBLM J0555-57Ab has a surface gravity log g2 =5.50+ 0.03 -0.13 and is one of the densest non-stellar-remnant objects currently known. These measurements are consistent with models of low-mass stars.PostprintPeer reviewe
The EBLM Project : IV. Spectroscopic orbits of over 100 eclipsing M dwarfs masquerading as transiting hot-Jupiters
We present 2271 radial velocity measurements taken on 118 single-line binary stars, taken over eight years with the CORALIE spectrograph. The binaries consist of F/G/K primaries and M dwarf secondaries. They were initially discovered photometricallyby the WASP planet survey, as their shallow eclipses mimic a hot Jupiter transit. The observations we present permit a precise characterisation of the binary orbital elements and mass function. With modelling of the primary star, this mass function is converted to a mass of the secondary star. In the future, this spectroscopic work will be combined with precise photometric eclipses to draw anempirical mass/radius relation for the bottom of the mass sequence. This has applications in both stellar astrophysics and the growing number of exoplanet surveys around M dwarfs. In particular, we have discovered 34 systems with a secondary mass below 0.2M⊙ and so we will ultimately double the number of known very low-mass stars with well-characterised masses and radii.The quality of our data combined with the amplitude of the Doppler variations mean that we are able to detect eccentricities as small as 0.001 and orbital periods to sub-second precision. Our sample can revisit some earlier work on the tidal evolution of close binaries, extending it to low mass ratios. We find some exceptional binary systems that are eccentric at orbital periods below three days, while our longest circular orbit has a period of 10.4 days. Amongst our systems, we note one remarkable architecture in J1146-42 that boasts three stars within one astronomical unit. By collating the EBLM binaries with published WASP planets and brown dwarfs, we derive a mass spectrum with twice the resolutionof previous work. We compare the WASP/EBLM sample of tightly bound orbits with work in the literature on more distant companionsup to 10 AU. We note that the brown dwarf desert appears wider, as it carves into the planetary domain for our short-period orbits.This would mean that a significantly reduced abundance of planets begins at ∼3MJup, well before the deuterium-burning limit. This may shed light on the formation and migration history of massive gas giants.PostprintPeer reviewe