scholarly journals Detection and characterisation of 54 massive companions with the SOPHIE spectrograph

2019 ◽  
Vol 631 ◽  
pp. A125 ◽  
Author(s):  
F. Kiefer ◽  
G. Hébrard ◽  
J. Sahlmann ◽  
S. G. Sousa ◽  
T. Forveille ◽  
...  
Keyword(s):  
Excess Noise ◽  
M Dwarfs ◽  
Primary Star ◽  
Detection Frequency ◽  
Substellar Objects ◽  
Low Mass ◽  
Orbital Periods ◽  
The Masses ◽  
M Dwarf ◽  
Astrometric Data

Context. Brown dwarfs (BD) are substellar objects intermediate between planets and stars with masses of ~13–80 MJ. While isolated BDs are most likely produced by gravitational collapse in molecular clouds down to masses of a few MJ, a non-negligible fraction of low-mass companions might be formed through the planet-formation channel in protoplanetary discs. The upper mass limit of objects formed within discs is still observationally unknown, the main reason being the strong dearth of BD companions at orbital periods shorter than 10 yr, also known as the BD desert. Aims. To address this question, we aim at determining the best statistics of companions within the 10–100 MJ mass regime and located closer than ~10 au to the primary star, while minimising observation and selection bias. Methods. We made extensive use of the radial velocity (RV) surveys of northern hemisphere FGK stars within 60 pc of the Sun, performed with the SOPHIE spectrograph at the Observatoire de Haute-Provence. We derived the Keplerian solutions of the RV variations of 54 sources. Public astrometric data of the HIPPARCOS and Gaia missions allowed us to constrain the masses of the companions for most sources. We introduce GASTON, a new method to derive inclination combining RVs and Keplerian and astrometric excess noise from Gaia DR1. Results. We report the discovery of 12 new BD candidates. For five of them, additional astrometric data led to a revision of their mass in the M-dwarf regime. Among the seven remaining objects, four are confirmed BD companions, and three others are likely also in this mass regime. Moreover, we report the detection of 42 M-dwarfs within the range of 90 MJ–0.52 M⊙. The resulting M sin i-P distribution of BD candidates shows a clear drop in the detection rate below 80-day orbital period. Above that limit, the BD desert appears rather wet, with a uniform distribution of the M sin i. We derive a minimum BD-detection frequency around Solar-like stars of 2.0 ± 0.5%.

scholarly journals The EBLM project

2019 ◽  
Vol 626 ◽  
pp. A119 ◽  
Author(s):  
S. Gill ◽  
P. F. L. Maxted ◽  
J. A. Evans ◽  
D. F. Evans ◽  
J. Southworth ◽  
...  
Keyword(s):  
Binary Systems ◽  
Evolutionary Models ◽  
Mixing Length ◽  
M Dwarfs ◽  
Primary Star ◽  
Best Fitting ◽  
Low Mass ◽  
Limb Darkening ◽  
M Dwarf ◽  
Orbital Solution

Some M-dwarfs around F-/G-type stars have been measured to be hotter and larger than predicted by stellar evolution models. Inconsistencies between observations and models need to be addressed with more mass, radius, and luminosity measurements of low-mass stars to test and refine evolutionary models. Our aim is to measure the masses, radii and ages of the stars in five low-mass eclipsing binary systems discovered by the WASP survey. We used WASP photometry to establish eclipse-time ephemerides and to obtain initial estimates for the transit depth and width. Radial velocity measurements were simultaneously fitted with follow-up photometry to find the best-fitting orbital solution. This solution was combined with measurements of atmospheric parameters to interpolate evolutionary models and estimate the mass of the primary star, and the mass and radius of the M-dwarf companion. We assess how the best fitting orbital solution changes if an alternative limb-darkening law is used and quantify the systematic effects of unresolved companions. We also gauge how the best-fitting evolutionary model changes if different values are used for the mixing length parameter and helium enhancement. We report the mass and radius of five M-dwarfs and find little evidence of inflation with respect to evolutionary models. The primary stars in two systems are near the “blue hook” stage of their post sequence evolution, resulting in two possible solutions for mass and age. We find that choices in helium enhancement and mixing-length parameter can introduce an additional 3−5% uncertainty in measured M-dwarf mass. Unresolved companions can introduce an additional 3−8% uncertainty in the radius of an M-dwarf, while the choice of limb-darkening law can introduce up to an additional 2% uncertainty. The choices in orbital fitting and evolutionary models can introduce significant uncertainties in measurements of physical properties of such systems.

scholarly journals The Mass-Luminosity Relation From Binaries

1998 ◽  
Vol 11 (1) ◽  
pp. 419-420
Author(s):  
David W. Latham
Keyword(s):  
Eclipsing Binaries ◽  
M Dwarfs ◽  
Direct Measurements ◽  
Nearby Stars ◽  
The Masses ◽  
Stellar Masses ◽  
M Dwarf ◽  
Magnitude Difference ◽  
Astrometric Binaries ◽  
Better Than

What is known about the masses of main-sequence stars from the analysis of binary orbits? Double-lined eclipsing binaries are the main source of very precise stellar masses and radii (e.g. Andersen 1997), contributing more than 100 determinations with better than 2% precision over the range 0.6 to 20 Mʘ. For lower-mass stars we are forced to turn to nearby systems with astrometric orbits (e.g. Henry et al. 1993). Not only is the number of good mass determinations from such systems smaller, but also the precision is generally poorer. We are approaching an era when interferometers should have a major impact by supplying good astrometric orbits for dozens of double-lined systems. Already we are beginning to see the sorts of results to expect from this (e.g. Torres et al. 1997). Figure 1. Mass vs. absolute V magnitude for eclipsing binaries (circles) and nearby astrometric binaries (squares) Figure 1 is an updated version of a diagram presented by Henry et al. (1993, their Figure 2). It shows the general run of mass determinations from about 10 Mʘ down to the substellar limit near 0.075 Mʘ. Ninety of the points in Figure 1 are for eclipsing binary masses from Andersen’s review (1991) and are plotted as open circles. The results for eclipsing binaries published since 1991 are plotted as 30 filled circles, adopting the same limit of 2% for the mass precision. In most cases the uncertainties are similar to the size of the symbols. Especially noteworthy is the pair of new points for CM Draconis (Metcalfe et al. 1996) with masses near 0.25 Mʘ. Together with the points for YY Geminorum near 0.6 Mʘ, these are the only M dwarfs that have precise mass determinations. For the most part we are forced to rely on nearby stars with astrometric orbits, to fill in the M dwarf region of the diagram. We have used filled squares in Figure 1 for 29 such systems from Henry et al. (1993), updated using 14 new parallaxes from Hipparcos and 4 from the new Yale Parallax Catalog (1995). Gliese 508 is not included, because it is now known to be a triple, while Gliese 67AB, 570BC, and 623AB are not included because there are not yet any direct measurements of the V magnitude difference for these systems.

Tìm kiếm đĩa tàn dư xung quanh các sao lùn kiểu phổ M-trễ nằm trong vùng lân cận Mặt Trời

2019 ◽  
Vol 15 (9) ◽  
pp. 43
Author(s):  
Nguyễn Thành Đạt ◽  
Phan Bảo Ngọc
Keyword(s):  
Spectral Energy ◽  
Archival Data ◽  
Debris Disks ◽  
M Dwarfs ◽  
Energy Distributions ◽  
Infrared Excess ◽  
Low Mass ◽  
M Dwarf ◽  
Infrared Survey ◽  
Infrared Data

In this paper, we present our search for debris disks in a sample of nearby late-M dwarfs based on infrared data of the Wide Infrared Survey Explorer. Using archival data, we constructed spectral energy distributions of these targets to detect their infrared excess. We detected infrared excess only in one target. This late-M dwarf is an excellent benchmark for further study of disks around very low-mass objects.

scholarly journals The Compositional Diversity of Low-Mass Exoplanets

2019 ◽  
Vol 47 (1) ◽  
pp. 141-171 ◽  
Author(s):  
Daniel Jontof-Hutter
Keyword(s):  
Bulk Composition ◽  
Diverse Range ◽  
Kepler Mission ◽  
Low Mass ◽  
Orbital Periods ◽  
Gaseous Atmospheres ◽  
The Masses ◽  
Compositional Diversity ◽  
Rocky Planets ◽  
Observational Techniques

Low-mass planets have an extraordinarily diverse range of bulk compositions, from primarily rocky worlds to those with deep gaseous atmospheres. As techniques for measuring the masses of exoplanets advance the field toward the regime of rocky planets, from ultrashort orbital periods to Venus-like distances, we identify the bounds on planet compositions, where sizes and incident fluxes inform bulk planet properties. In some cases, the precision of measurement of planet masses and sizes is approaching the theoretical uncertainties in planet models. An emerging picture explains aspects of the diversity of low-mass planets, although some problems remain: Do extreme low-density, low-mass planets challenge models of atmospheric mass loss? Are planet sizes strictly separated by bulk composition? Why do some stellar characterizations differ between observational techniques? With the Transiting Exoplanet Survey Satellite ( TESS) mission, low-mass exoplanets around the nearest stars will soon be discovered and characterized with unprecedented precision, permitting more detailed planetary modeling and atmospheric characterization of low-mass exoplanets than ever before. ▪ Following the Kepler mission, studies of exoplanetary compositions have entered the terrestrial regime. ▪ Low-mass planets have an extraordinary range of compositions, from Earth-like mixtures of rock and metal to mostly tenuous gas. ▪ The TESS mission will discover low-mass planets that can be studied in more detail than ever before.

scholarly journals HST-FGS Astrometry of the Low Mass Binary L722-22

1999 ◽  
Vol 172 ◽  
pp. 405-407
Author(s):  
L.G. Taff ◽  
John L. Hershey
Keyword(s):  
Main Sequence ◽  
Hubble Space Telescope ◽  
Brown Dwarf ◽  
One Dimensional ◽  
Photographic Images ◽  
System A ◽  
Data Points ◽  
Low Mass ◽  
The Masses ◽  
M Dwarf

The M dwarf L722-22 (= LHS 1047) was discovered to be a binary system by Ianna 20 years ago. The analysis of the ground- based data indicated a mass 0.06M⊙ for the secondary. This is below the nominal stellar mass limit of 0.08M⊙. The importance of potential “brown-dwarf” candidates, and the fact that the masses of both components place them near the end of the main sequence, made this system a prime object for further, intensive, study.This close (separation 0."3), faint (V = 11.m5, 14.m4) binary was near the limit for ground-based work. The residuals of an individual night’s photographic data were typically at the 50% level. Also, the photographic images are completely blended. The few one-dimensional speckle data points yielded a merged, asymmetric image profile. Finally, this system is too faint for HIPPARCOS. Our proposal for Hubble Space Telescope Fine Guidance Sensor (FGS) observing was approved in 1992.

scholarly journals Magnetic activity in the HARPS M dwarf sample

2017 ◽  
Vol 600 ◽  
pp. A13 ◽  
Author(s):  
N. Astudillo-Defru ◽  
X. Delfosse ◽  
X. Bonfils ◽  
T. Forveille ◽  
C. Lovis ◽  
...  
Keyword(s):  
Monitoring Program ◽  
Rotation Period ◽  
Magnetic Activity ◽  
Spectral Lines ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
The Galaxy ◽  
Low Mass ◽  
M Dwarf ◽  
The Relationship

Context. Atmospheric magnetic fields in stars with convective envelopes heat stellar chromospheres, and thus increase the observed flux in the Ca ii H and K doublet. Starting with the historical Mount Wilson monitoring program, these two spectral lines have been widely used to trace stellar magnetic activity, and as a proxy for rotation period (Prot) and consequently for stellar age. Monitoring stellar activity has also become essential in filtering out false-positives due to magnetic activity in extra-solar planet surveys. The Ca ii emission is traditionally quantified through the R'HK-index, which compares the chromospheric flux in the doublet to the overall bolometric flux of the star. Much work has been done to characterize this index for FGK-dwarfs, but M dwarfs – the most numerous stars of the Galaxy – were left out of these analyses and no calibration of their Ca ii H and K emission to an R'HK exists to date. Aims. We set out to characterize the magnetic activity of the low- and very-low-mass stars by providing a calibration of the R'HK-index that extends to the realm of M dwarfs, and by evaluating the relationship between R'HK and the rotation period. Methods. We calibrated the bolometric and photospheric factors for M dwarfs to properly transform the S-index (which compares the flux in the Ca ii H and K lines to a close spectral continuum) into the R'HK. We monitored magnetic activity through the Ca ii H and K emission lines in the HARPS M dwarf sample. Results. The R'HK index, like the fractional X-ray luminosity LX/Lbol, shows a saturated correlation with rotation, with saturation setting in around a ten days rotation period. Above that period, slower rotators show weaker Ca ii activity, as expected. Under that period, the R'HK index saturates to approximately 10-4. Stellar mass modulates the Ca ii activity, with R'HK showing a constant basal activity above 0.6 M⊙ and then decreasing with mass between 0.6 M⊙ and the fully-convective limit of 0.35 M⊙. Short-term variability of the activity correlates with its mean level and stars with higher R'HK indexes show larger R'HK variability, as previously observed for earlier spectral types.

scholarly journals The TESS light curve of the eccentric eclipsing binary 1SWASP J011351.29+314909.7 – no evidence for a very hot M-dwarf companion

2020 ◽  
Vol 498 (1) ◽  
pp. L15-L19
Author(s):  
Matthew I Swayne ◽  
Pierre F L Maxted ◽  
Vedad Kunovac Hodžić ◽  
Amaury H M J Triaud
Keyword(s):  
Light Curve ◽  
Effective Temperature ◽  
Binary Star ◽  
Mass Star ◽  
Primary Star ◽  
Eclipsing Binary ◽  
Low Mass ◽  
Stellar Models ◽  
Eclipsing Binary Star ◽  
M Dwarf

ABSTRACT A 2014 study of the eclipsing binary star 1SWASPJ011351.29+314909.7 (J0113+31) reported an unexpectedly high effective temperature for the M-dwarf companion to the 0.95-M⊙ primary star. The effective temperature inferred from the secondary eclipse depth was ∼600 K higher than the value predicted from stellar models. Such an anomalous result questions our understanding of low-mass stars and might indicate a significant uncertainty when inferring properties of exoplanets orbiting them. We seek to measure the effective temperature of the M-dwarf companion using the light curve of J0113+31 recently observed by the Transiting Exoplanet Survey Satellite (TESS). We use the pycheops modelling software to fit a combined transit and eclipse model to the TESS light curve. To calculate the secondary effective temperature, we compare the best-fitting eclipse depth to the predicted eclipse depths from theoretical stellar models. We determined the effective temperature of the M dwarf to be Teff,2 = 3208 ± 43 K, assuming log g2 = 5, [Fe/H] = −0.4, and no alpha-element enhancement. Varying these assumptions changes Teff,2 by less than 100 K. These results do not support a large anomaly between observed and theoretical low-mass star temperatures.

scholarly journals The White Dwarf Binary Pathways Survey – IV. Three close white dwarf binaries with G-type secondary stars

2020 ◽  
Vol 501 (2) ◽  
pp. 1677-1689
Author(s):  
M S Hernandez ◽  
M R Schreiber ◽  
S G Parsons ◽  
B T Gänsicke ◽  
F Lagos ◽  
...  
Keyword(s):  
Spectral Type ◽  
White Dwarf ◽  
Binary Stars ◽  
Cataclysmic Variable ◽  
Common Envelope ◽  
History Of ◽  
Low Mass ◽  
Orbital Periods ◽  
M Dwarf

ABSTRACT Constraints from surveys of post-common envelope binaries (PCEBs) consisting of a white dwarf plus an M-dwarf companion have led to significant progress in our understanding of the formation of close white dwarf binary stars with low-mass companions. The white dwarf binary pathways project aims at extending these previous surveys to larger secondary masses, i.e. secondary stars of spectral-type AFGK. Here, we present the discovery and observational characterization of three PCEBs with G-type secondary stars and orbital periods between 1.2 and 2.5 d. Using our own tools as well as MESA, we estimate the evolutionary history of the binary stars and predict their future. We find a large range of possible evolutionary histories for all three systems and identify no indications for differences in common envelope evolution compared to PCEBs with lower mass secondary stars. Despite their similarities in orbital period and secondary spectral type, we estimate that the future of the three systems is very different: TYC 4962-1205-1 is a progenitor of a cataclysmic variable system with an evolved donor star, TYC 4700-815-1 will run into dynamically unstable mass transfer that will cause the two stars to merge, and TYC 1380-957-1 may appear as supersoft source before becoming a rather typical cataclysmic variable star.

scholarly journals Determining the mass of the planetary candidate HD 114762 b using Gaia

2019 ◽  
Vol 632 ◽  
pp. L9 ◽  
Author(s):  
Flavien Kiefer
Keyword(s):  
Spectral Analysis ◽  
Preceding Paper ◽  
Brown Dwarfs ◽  
Excess Noise ◽  
The Sun ◽  
Minimum Mass ◽  
Brown Dwarf ◽  
Data Release ◽  
Low Mass ◽  
M Dwarf

The first planetary candidate discovered by Latham et al. (1989, Nature, 339, 38) with radial velocities around a solar-like star other than the Sun, HD 114762 b, was detected with a minimum mass of 11 MJ. The small v sin i ∼ 0 km s−1 that is otherwise measured by spectral analysis indicated that this companion of a late-F subgiant star better corresponds to a massive brown dwarf (BD) or even a low-mass M-dwarf seen nearly face-on. To our knowledge, the nature of HD 114762 b is still undetermined. The astrometric noise measured for this system in the first data release, DR1, of the Gaia mission allows us to derive new constraints on the astrometric motion of HD 114762 and on the mass of its companion. We use the method GASTON, introduced in a preceding paper, which can simulate Gaia data and determine the distribution of inclinations that are compatible with the astrometric excess noise. With an inclination of 6.26.2+1.9−1.3 degree, the mass of the companion is constrained to Mb = 108+31−26 MJ. HD 114762 b thus indeed belongs to the M-dwarf domain, down to brown dwarfs, with Mb >  13.5 MJ at the 3σ level, and is not a planet.

scholarly journals 2MASS J15460752−6258042: a mid-M dwarf hosting a prolonged accretion disc

2020 ◽  
Vol 494 (1) ◽  
pp. 62-68 ◽  
Author(s):  
Jinhee Lee ◽  
Inseok Song ◽  
Simon Murphy
Keyword(s):  
Accretion Rate ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Velocity Measurements ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Infrared Excess ◽  
Low Mass ◽  
M Dwarf ◽  
Gaia Dr2

ABSTRACT We report the discovery of the oldest (∼55 Myr) mid-M type star known to host ongoing accretion. 2MASS J15460752–6258042 (2M1546, spectral type M5, 59.2 pc) shows spectroscopic signs of accretion such as strong H α, He i, and [O i] emission lines, from which we estimate an accretion rate of ∼10−10 M⊙ yr−1. Considering the clearly detected infrared excess in all WISE bands, the shape of its spectral energy distribution (SED) and its age, we believe that the star is surrounded by a transitional disc, clearly with some gas still present at inner radii. The position and kinematics of the star from Gaia DR2 and our own radial-velocity measurements suggest membership in the nearby ∼55 Myr-old Argus moving group. At only 59 pc from Earth, 2M1546 is one of the nearest accreting mid-M dwarfs, making it an ideal target for studying the upper limit on the lifetimes of gas-rich discs around low-mass stars.

Sign in / Sign up

Export Citation Format

Share Document