scholarly journals Exploring the Nu2 Lupi system with CHEOPS

2021 ◽  
Author(s):  
Laetitia Delrez ◽  
Keyword(s):  
Outer Planet ◽  
Detailed Characterization ◽  
Water Fraction ◽  
Naked Eye ◽  
Long Period ◽  
Low Mass ◽  
Formation And Evolution ◽  
Orbital Periods ◽  
Large Water

<p>***Results under embargo. Paper accepted for publication at Nature Astronomy, to be published in June.***</p> <p>Multi-transiting planetary systems around bright stars offer unique windows to comparative exoplanetology. Nu2 Lupi (HD 136352) is a naked-eye (V=5.8) Sun-like star that was discovered to host three low-mass planets with orbital periods of 11.6, 27.6, and 107.6 days via radial velocity monitoring with the HARPS spectrograph. The two inner planets (b and c) were recently found to transit by the TESS mission, prompting us to follow up the system with ESA's brand-new CHaracterizing ExOPlanets Satellite (CHEOPS). This led to the exciting discovery that the outer planet d is also transiting. With its bright Sun-like star, long period, and mild irradiation (∼5.7 times the irradiation of Earth), Nu2 Lupi d unlocks a completely new region in the parameter space of exoplanets amenable to detailed characterization. By combining all available space and ground-based data, we measured its radius and mass to be 2.56±0.09 R<sub>Earth</sub> and 8.82±0.94 M<sub>Earth</sub>, respectively, and refined the properties of all three planets: planet b likely has a rocky mostly dry composition, while planets c and d seem to have retained small hydrogen-helium envelopes and a possibly large water fraction. This diversity of planetary compositions makes the Nu2 Lupi system an excellent laboratory for testing formation and evolution models of low-mass planets.</p>

scholarly journals Stellar and substellar companions of nearby stars from Gaia DR2

2019 ◽  
Vol 623 ◽  
pp. A72 ◽  
Author(s):  
Pierre Kervella ◽  
Frédéric Arenou ◽  
François Mignard ◽  
Frédéric Thévenin
Keyword(s):  
Proper Motion ◽  
Motion Vector ◽  
Tangential Velocity ◽  
Long Period ◽  
Nearby Stars ◽  
Low Mass ◽  
Substellar Companions ◽  
Orbital Periods ◽  
The Masses

Context. The census of stellar and substellar companions of nearby stars is largely incomplete, in particular toward the low-mass brown dwarf and long-period exoplanets. It is, however, fundamentally important in the understanding of the stellar and planetary formation and evolution mechanisms. Nearby stars are particularly favorable targets for high precision astrometry. Aims. We aim to characterize the presence of physical companions of stellar and substellar mass in orbit around nearby stars. Methods. Orbiting secondary bodies influence the proper motion of their parent star through their gravitational reflex motion. Using the HIPPARCOS and Gaia’s second data release (GDR2) catalogs, we determined the long-term proper motion of the stars common to these two catalogs. We then searched for a proper motion anomaly (PMa) between the long-term proper motion vector and the GDR2 (or HIPPARCOS) measurements, indicative of the presence of a perturbing secondary object. We focussed our analysis on the 6741 nearby stars located within 50 pc, and we also present a catalog of the PMa for ≳99% of the HIPPARCOS catalog (≈117 000 stars). Results. 30% of the stars studied present a PMa greater than 3σ. The PMa allows us to detect orbiting companions, or set stringent limits on their presence. We present a few illustrations of the PMa analysis to interesting targets. We set upper limits of 0.1−0.3 MJ to potential planets orbiting Proxima between 1 and 10 au (Porb = 3 to 100 years). We confirm that Proxima is gravitationally bound to α Cen. We recover the masses of the known companions of ϵ Eri, ϵ Ind, Ross 614 and β Pic. We also detect the signature of a possible planet of a few Jovian masses orbiting τ Ceti. Conclusions. Based on only 22 months of data, the GDR2 has limitations. But its combination with the HIPPARCOS catalog results in very high accuracy PMa vectors, that already enable us to set valuable constraints on the binarity of nearby objects. The detection of tangential velocity anomalies at a median accuracy of σ(ΔvT) = 1.0 m s−1 per parsec of distance is already possible with the GDR2. This type of analysis opens the possibility to identify long period orbital companions otherwise inaccessible. For long orbital periods, Gaia’s complementarity to radial velocity and transit techniques (that are more sensitive to short orbital periods) already appears to be remarkably powerful.

scholarly journals Influence of the initial orbital period and accretion efficiency on the low-mass binary evolution

2021 ◽  
pp. 25-30
Author(s):  
J. Petrovic
Keyword(s):  
Mass Transfer ◽  
Orbital Period ◽  
White Dwarf ◽  
Binary Systems ◽  
Evolutionary Models ◽  
Stable Case ◽  
Long Period ◽  
Low Mass ◽  
Orbital Periods ◽  
Binary Evolution

This paper presents detailed evolutionary models of low-mass binary systems (1.25 + 1 M?) with initial orbital periods of 10, 50 and 100 days and accretion efficiency of 10%, 20%, 50%, and a conservative assumption. All models are calculated with the MESA (Modules for Experiments in Stellar Astrophysics) evolutionary code. We show that such binary systems can evolve via a stable Case B mass transfer into long period helium white dwarf systems.

scholarly journals A low-mass planet candidate orbiting Proxima Centauri at a distance of 1.5 AU

2020 ◽  
Vol 6 (3) ◽  
pp. eaax7467 ◽  
Author(s):  
Mario Damasso ◽  
Fabio Del Sordo ◽  
Guillem Anglada-Escudé ◽  
Paolo Giacobbe ◽  
Alessandro Sozzetti ◽  
...  
Keyword(s):  
Nearest Neighbor ◽  
Angular Separation ◽  
Activity Cycle ◽  
Terrestrial Planet ◽  
Radial Velocities ◽  
Low Mass ◽  
Large Maximum ◽  
Formation And Evolution ◽  
True Mass

Our nearest neighbor, Proxima Centauri, hosts a temperate terrestrial planet. We detected in radial velocities evidence of a possible second planet with minimum mass mc sin ic = 5.8 ± 1.9M⊕ and orbital period Pc=5.21−0.22+0.26 years. The analysis of photometric data and spectro-scopic activity diagnostics does not explain the signal in terms of a stellar activity cycle, but follow-up is required in the coming years for confirming its planetary origin. We show that the existence of the planet can be ascertained, and its true mass can be determined with high accuracy, by combining Gaia astrometry and radial velocities. Proxima c could become a prime target for follow-up and characterization with next-generation direct imaging instrumentation due to the large maximum angular separation of ~1 arc second from the parent star. The candidate planet represents a challenge for the models of super-Earth formation and evolution.

scholarly journals Properties of the Subgiants in Various Types of Eclipsing Binary Systems

1998 ◽  
Vol 11 (1) ◽  
pp. 384-384
Author(s):  
V.G. Karetnikov
Keyword(s):  
Binary Systems ◽  
Eclipsing Binary ◽  
Long Period ◽  
Short Period ◽  
Low Mass ◽  
Orbital Periods ◽  
Subgiant Stars

The radius and temperature excesses are found to be largest for the subgiant stars in DS systems and in low-mass and long-period SD systems, being the smallest for the subgiant stars in AR systems and in low-mass and short-period SD-systems. Subgiant stars in AR and in more massive SD systems exhibit even the temperature deficiency which is the largest for the primariesof the AR systems. Necessity is shown to divide the class of SD systems into several groups according to masses and orbital periods while studying their properties.

scholarly journals News From The Erebos Project

2017 ◽  
Vol 26 (1) ◽  
Author(s):  
Veronika Schaffenroth ◽  
Brad Barlow ◽  
Stephan Geier ◽  
Maja Vučković ◽  
Dave Kilkenny ◽  
...  
Keyword(s):  
Binary Systems ◽  
Brown Dwarfs ◽  
Eclipsing Binaries ◽  
Current Status ◽  
Red Giants ◽  
Large Program ◽  
Low Mass ◽  
Orbital Periods ◽  
Red Giant

AbstractPlanets and brown dwarfs in close orbits will interact with their host stars, as soon as the stars evolve to become red giants. However, the outcome of those interactions is still unclear. Recently, several brown dwarfs have been discovered orbiting hot subdwarf stars at very short orbital periods of 0.065 - 0.096 d. More than 8% of the close hot subdwarf binaries might have sub-stellar companions. This shows that such companions can significantly affect late stellar evolution and that sdB binaries are ideal objects to study this influence. Thirty-eight new eclipsing sdB binary systems with cool low-mass companions and periods from 0.05 to 0.5 d were discovered based on their light curves by the OGLE project. In the recently published catalog of eclipsing binaries in the Galactic bulge, we discovered 75 more systems. We want to use this unique and homogeneously selected sample to derive the mass distribution of the companions, constrain the fraction of sub-stellar companions and determine the minimum mass needed to strip off the red-giant envelope. We are especially interested in testing models that predict hot Jupiter planets as possible companions. Therefore, we started the EREBOS (Eclipsing Reflection Effect Binaries from the OGLE Survey) project, which aims at analyzing those new HW Vir systems based on a spectroscopic and photometric follow up. For this we were granted an ESO Large Program for ESO-VLT/FORS2. Here we give an update on the the current status of the project and present some preliminary results.

scholarly journals TOI-132 b: A short-period planet in the Neptune desert transiting a V = 11.3 G-type star★

2020 ◽  
Vol 493 (1) ◽  
pp. 973-985 ◽  
Author(s):  
Matías R Díaz ◽  
James S Jenkins ◽  
Davide Gandolfi ◽  
Eric D Lopez ◽  
Maritza G Soto ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Velocity Variation ◽  
Planetary Mass ◽  
Radial Velocity Variation ◽  
Short Period ◽  
Low Mass ◽  
Formation And Evolution ◽  
Level 1 ◽  
Atmospheric Mass

ABSTRACT The Neptune desert is a feature seen in the radius-period plane, whereby a notable dearth of short period, Neptune-like planets is found. Here, we report the Transiting Exoplanet Survey Satellite (TESS) discovery of a new short-period planet in the Neptune desert, orbiting the G-type dwarf TYC 8003-1117-1 (TOI-132). TESS photometry shows transit-like dips at the level of ∼1400 ppm occurring every ∼2.11 d. High-precision radial velocity follow-up with High Accuracy Radial Velocity Planet Searcher confirmed the planetary nature of the transit signal and provided a semi-amplitude radial velocity variation of 11.38 $^{+0.84}_{-0.85}$ m s−1, which, when combined with the stellar mass of 0.97 ± 0.06 M⊙, provides a planetary mass of 22.40$^{+1.90}_{-1.92}$ M⊕. Modelling the TESS light curve returns a planet radius of 3.42$^{+0.13}_{-0.14}$ R⊕, and therefore the planet bulk density is found to be 3.08$^{+0.44}_{-0.46}$ g cm−3. Planet structure models suggest that the bulk of the planet mass is in the form of a rocky core, with an atmospheric mass fraction of 4.3$^{+1.2}_{-2.3}$ per cent. TOI-132 b is a TESS Level 1 Science Requirement candidate, and therefore priority follow-up will allow the search for additional planets in the system, whilst helping to constrain low-mass planet formation and evolution models, particularly valuable for better understanding of the Neptune desert.

scholarly journals The Formation and Evolution of Symbiotic Stars

1988 ◽  
Vol 103 ◽  
pp. 311-321
Author(s):  
R.F. Webbink
Keyword(s):  
Mass Transfer ◽  
Binary Systems ◽  
Symbiotic Stars ◽  
Main Sequence Stars ◽  
Evolutionary Origins ◽  
Low Mass ◽  
Formation And Evolution ◽  
Orbital Periods ◽  
Modes Of Interaction ◽  
Approximate Expressions

AbstractThe evolutionary origins of symbiotic stars containing (i) disk-accreting main sequence stars, (ii) wind-fed, shell-burning white dwarfs, and (iii) disk-accreting neutron stars are described. Of particular interest are those white dwarf systems which have orbital periods too short to have escaped tidal mass transfer prior to becoming symbiotics. We show here that, under suitable circumstances, low-mass, long period binaries may undergo quasi-conservative mass transfer, rather than evolving through common envelope evolution to the cataclysmic variable state, thus accounting for the existence of these systems. Approximate expressions are given for the lifetimes, and relative efficiencies (mass accreted/mass of donor) for different modes of interaction among symbiotic binary systems.

scholarly journals Two temperate sub-Neptunes transiting the star EPIC 212737443

2019 ◽  
Vol 488 (1) ◽  
pp. 536-546
Author(s):  
Mahesh Herath ◽  
Tobias C Hinse ◽  
John H Livingston ◽  
Jesús Hernández ◽  
Daniel F Evans ◽  
...  
Keyword(s):  
High Resolution ◽  
Planetary System ◽  
Equilibrium Temperature ◽  
Outer Planet ◽  
High Resolution Imaging ◽  
Transiting Planets ◽  
Resolution Imaging ◽  
Orbital Periods ◽  
Imaging And Spectroscopy

ABSTRACT We report the validation of a new planetary system around the K3 star EPIC 212737443 using a combination of K2 photometry, follow-up high-resolution imaging and spectroscopy. The system consists of two sub-Neptune sized transiting planets with radii of 2.6R⊕ and 2.7R⊕, with orbital periods of 13.6 and 65.5 d, equilibrium temperatures of 536 and 316 K, respectively. In the context of validated K2 systems, the outer planet has the longest precisely measured orbital period, as well as the lowest equilibrium temperature for a planet orbiting a star of spectral type earlier than M. The two planets in this system have a mutual Hill radius of ΔRH  = 36, larger than most other known transiting multiplanet systems, suggesting the existence of another (possibly non-transiting) planet, or that the system is not maximally packed.

The Formation and Evolution of Low-Mass Close Binaries with Compact Components

1987 ◽  
Vol 93 ◽  
pp. 15-33
Author(s):  
A.V. Tutukov ◽  
L.R. Yungelson
Keyword(s):  
Neutron Star ◽  
Mass Exchange ◽  
Stellar Wind ◽  
Close Binary ◽  
Close Binaries ◽  
Evolutionary Status ◽  
Contact Phase ◽  
Low Mass ◽  
Formation And Evolution ◽  
Orbital Periods

AbstractWe discuss the formation and evolution of interacting low-mass close binaries with a He-ICO- or ONe-dwarf neutron star or a black hole as a compact component. Mass exchange leads to cataclysmic events in such systems. The rate of semidetached low-mass close binary formation is 5×10−3 yr−1 if the accreting component is a He degenerate dwarf, 5×10−3 yr−1 if it is a CO-dwarf and 3×10−8 yr−1 if it is a neutron star. Systems with compact accretors arise as the result of the common envelope phase of close binary evolution or due to collisions of single neutron stars or dwarfs with low-mass single stars in dense stellar clusters. Evolution of LMCB to the contact phase in semi-detached stages is determined mainly by the angular momentum losses by a magnetic stellar wind and radiation of gravitational waves. Numerical computations of evolution with momentum loss explain observed mass exchange rates in such systems, the absence of cataclysmic variables with orbital periods 2h−3h, the low number and the evolutionary status of systems with orbital periods shorter than 80m. In conclusion we list unsolved problems related to magnetic stellar wind, the distribution of young close binaries over main initial parameters, stability of mass exchange.

scholarly journals Exoplanet mass estimation for a sample of targets for the Ariel mission

2021 ◽  
Author(s):  
J. R. Barnes ◽  
C. A. Haswell
Keyword(s):  
Radial Velocity ◽  
Input Parameter ◽  
Noise Sources ◽  
Time Commitment ◽  
Low Mass ◽  
Time Required ◽  
Fixed Input ◽  
The Impact ◽  
Quadrature Sampling

AbstractAriel’s ambitious goal to survey a quarter of known exoplanets will transform our knowledge of planetary atmospheres. Masses measured directly with the radial velocity technique are essential for well determined planetary bulk properties. Radial velocity masses will provide important checks of masses derived from atmospheric fits or alternatively can be treated as a fixed input parameter to reduce possible degeneracies in atmospheric retrievals. We quantify the impact of stellar activity on planet mass recovery for the Ariel mission sample using Sun-like spot models scaled for active stars combined with other noise sources. Planets with necessarily well-determined ephemerides will be selected for characterisation with Ariel. With this prior requirement, we simulate the derived planet mass precision as a function of the number of observations for a prospective sample of Ariel targets. We find that quadrature sampling can significantly reduce the time commitment required for follow-up RVs, and is most effective when the planetary RV signature is larger than the RV noise. For a typical radial velocity instrument operating on a 4 m class telescope and achieving 1 m s−1 precision, between ~17% and ~ 37% of the time commitment is spent on the 7% of planets with mass Mp < 10 M⊕. In many low activity cases, the time required is limited by asteroseismic and photon noise. For low mass or faint systems, we can recover masses with the same precision up to ~3 times more quickly with an instrumental precision of ~10 cm s−1.

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