scholarly journals Spectroscopic binaries RV Tauri and DF Cygni

2019 ◽  
Vol 628 ◽  
pp. A40 ◽  
Author(s):  
Rajeev Manick ◽  
Devika Kamath ◽  
Hans Van Winckel ◽  
Alain Jorissen ◽  
Sanjay Sekaran ◽  
...  
Keyword(s):  
Orbital Period ◽  
Asymptotic Giant Branch ◽  
Spectroscopic Binaries ◽  
Spectral Energy ◽  
Pulsation Frequency ◽  
Photometric Variability ◽  
Orbital Inclination ◽  
Orbital Periods ◽  
The Impact

Context. Some RV Tauri stars show a long-term photometric variability in their mean magnitudes. DF Cygni (DF Cyg), the only RV Tauri star in the original Kepler field, and the prototype RV Tauri (RV Tau) are two such stars. Aims. The focus of this paper is on two famous but still poorly understood RV Tauri stars: RV Tau and DF Cyg. We aim to confirm their suspected binary nature and derive their orbital elements to investigate the impact of their orbits on the evolution of these systems. This research is embedded in a wider endeavour to study binary evolution of low- and intermediate-mass stars. Methods. The high amplitude pulsations were cleaned from the radial-velocity data to better constrain the orbital motion, allowing us to obtain accurate orbital parameters. We also analysed the photometric time series of both stars using a Lomb-Scargle periodogram. We used Gaia Data Release 2 (DR2) parallaxes in combination with the spectral energy distributions (SEDs) to compute their luminosities. These luminosities were complemented with the ones we computed using a period-luminosity-colour (PLC) relation for RV Tauri stars. The ratio of the circumstellar infrared (IR) flux to the photospheric flux obtained from the SEDs was used to estimate the orbital inclination of each system. Results. DF Cyg and RV Tau are binaries with spectroscopic orbital periods of 784 ± 16 days and 1198 ± 17 days, respectively. These orbital periods are found to be similar to the long-term periodic variability in the photometry, indicating that binarity indeed explains the long-term photometric variability. The SEDs of these systems indicate the presence of a circumbinary disc. Our line of sight grazes the dusty disc, which causes the photometric flux from the star to extinct periodically with the orbital period. Our derived orbital inclinations enabled us to obtain accurate companion masses for DF Cyg and RV Tau, and these were found to be 0.6 ± 0.1 M⊙ and 0.7 ± 0.1 M⊙, respectively. The derived luminosities suggest that RV Tau is a post asymptotic giant branch (post-AGB) binary, while DF Cyg is likely a post red giant branch (post-RGB) binary. Analysis of the Kepler photometry of DF Cyg revealed a power spectrum with side lobes around the fundamental pulsation frequency. This modulation corresponds to the spectroscopic orbital period and hence to the long-term photometric period. Finally we report on the evidence of high velocity absorption features related to the Hα profile in both objects, indicating outflows launched from around the companion.

scholarly journals The eccentric behaviour of windy binary stars

2019 ◽  
Vol 629 ◽  
pp. A103 ◽  
Author(s):  
M. I. Saladino ◽  
O. R. Pols
Keyword(s):  
Mass Transfer ◽  
Binary Stars ◽  
Numerical Models ◽  
Orbital Evolution ◽  
Small Sample ◽  
Asymptotic Giant Branch ◽  
Tidal Effects ◽  
Orbital Parameters ◽  
Orbital Periods ◽  
The Impact

Carbon-enhanced metal-poor stars, CH stars, barium stars, and extrinsic S stars, among other classes of chemically peculiar stars, are thought to be the products of the interaction of low- and intermediate-mass binaries, which occurred when the most evolved star was in the asymptotic giant branch (AGB) phase. Binary evolution models predict that because of the large sizes of AGB stars, if the initial orbital periods of such systems are shorter than a few thousand days, their orbits should have circularised due to tidal effects. However, observations of the progeny of AGB binary stars show that many of these objects have substantial eccentricities, up to e ≈ 0.9. In this work we explore the impact of wind mass transfer on the orbital parameters of AGB binary stars by performing numerical simulations in which the AGB wind is modelled using a hydrodynamical code and the dynamics of the stars is evolved using an N-body code. We find that in most models the effect of wind mass transfer contributes to the circularisation of the orbit, but on longer timescales than tidal circularisation if e ≲ 0.4. For relatively low initial wind velocities and pseudo-synchronisation of the donor star, we find a structure resembling wind Roche-lobe overflow as the stars approach periastron. In this case, the interaction between the gas and the star is stronger than when the initial wind velocity is high and the orbit shrinks while the eccentricity decreases. In one of our models wind interaction is found to pump the eccentricity of the orbit on a similar timescale as tidal circularisation. However, since the orbit of this model is shrinking tidal effects will become stronger during the evolution of the system. Although our study is based on a small sample of models, it offers some insight into the orbital evolution of eccentric binary stars interacting via winds. A larger grid of numerical models for different binary parameters is needed to test if a regime exists where hydrodynamical eccentricity pumping can effectively counteract tidal circularisation, and if this can explain the puzzling eccentricities of the descendants of AGB binaries.

scholarly journals Life after eruption VIII: The orbital periods of novae

2020 ◽  
Author(s):  
I Fuentes-Morales ◽  
C Tappert ◽  
M Zorotovic ◽  
N Vogt ◽  
E C Puebla ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Binary Star ◽  
Cataclysmic Variables ◽  
Momentum Loss ◽  
Period Distribution ◽  
Angular Momentum Loss ◽  
Orbital Periods ◽  
The Impact ◽  
Crucial Ingredient

Abstract The impact of nova eruptions on the long-term evolution of Cataclysmic Variables (CVs) is one of the least understood and intensively discussed topics in the field. A crucial ingredient to improve with this would be to establish a large sample of post-novae with known properties, starting with the most easily accessible one, the orbital period. Here we report new orbital periods for six faint novae: X Cir (3.71 h), IL Nor (1.62 h), DY Pup (3.35 h), V363 Sgr (3.03 h), V2572 Sgr (3.75 h) and CQ Vel (2.7 h). We furthermore revise the periods for the old novae OY Ara, RS Car, V365 Car, V849 Oph, V728 Sco, WY Sge, XX Tau and RW UMi. Using these new data and critically reviewing the trustworthiness of reported orbital periods of old novae in the literature, we establish an updated period distribution. We employ a binary-star evolution code to calculate a theoretical period distribution using both an empirical and the classical prescription for consequential angular momentum loss. In comparison with the observational data we find that both models especially fail to reproduce the peak in the 3 – 4 h range, suggesting that the angular momentum loss for CVs above the period gap is not totally understood.

scholarly journals How to disentangle geometry and mass-loss rate from AGB-star spectral energy distributions

2020 ◽  
Vol 642 ◽  
pp. A142 ◽  
Author(s):  
J. Wiegert ◽  
M. A. T. Groenewegen ◽  
A. Jorissen ◽  
L. Decin ◽  
T. Danilovich
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Asymptotic Giant Branch ◽  
Spectral Energy ◽  
High Angular Resolution ◽  
Circumstellar Envelope ◽  
Spectral Energy Distributions ◽  
Energy Distributions ◽  
The Impact

Context. High-angular-resolution observations of asymptotic giant branch (AGB) stars often reveal non-spherical morphologies for the gas and dust envelopes. Aims. We aim to make a pilot study to quantify the impact of different geometries (spherically symmetric, spiral-shaped, and disc-shaped) of the dust component of AGB envelopes on spectral energy distributions (SEDs), mass estimates, and subsequent mass-loss rate (MLR) estimates. We also estimate the error made on the MLR if the SED is fitted by an inappropriate geometrical model. Methods. We use the three-dimensional Monte-Carlo-based radiative-transfer code RADMC-3D to simulate emission from dusty envelopes with different geometries (but fixed spatial extension). We compare these predictions with each other, and with the SED of the AGB star EP Aqr that we use as a benchmark since its envelope is disc-like and known to harbour spiral arms, as seen in CO. Results. The SEDs involving the most massive envelopes are those for which the different geometries have the largest impact, primarily on the silicate features at 10 and 18 μm. These different shapes originate from large differences in optical depths. Massive spirals and discs appear akin to black bodies. Optically thick edge-on spirals and discs (with dust masses of 10−4 and 10−5 M⊙) exhibit black-body SEDs that appear cooler than those from face-on structures and spheres of the same mass, while optically thick face-on distributions appear as warmer emission. We find that our more realistic models, combined spherical and spiral distributions, are 0.1 to 0.5 times less massive than spheres with similar SEDs. More extreme, less realistic scenarios give that spirals and discs are 0.01 to 0.05 times less massive than corresponding spheres. This means that adopting the wrong geometry for an AGB circumstellar envelope may result in a MLR that is incorrect by as much as one to two orders of magnitude when derived from SED fitting.

scholarly journals Binary Slowly Pulsating B Stars

2000 ◽  
Vol 176 ◽  
pp. 436-436 ◽  
Author(s):  
P. De Cat ◽  
C. Aerts
Keyword(s):  
Line Profile ◽  
Spectroscopic Binaries ◽  
High Signal ◽  
B Stars ◽  
Orbital Frequency ◽  
Long Term Follow Up ◽  
Order Of Magnitude ◽  
Orbital Periods ◽  
Photometric Measurements

AbstractThe satellite Hipparcos led to the discovery of 267 new variable B-type stars. Some 100 of them were classified as candidate slowly pulsating B stars (SPBs) by Waelkens et al. (1998). Twelve of the brightest southern candidate SPBs were selected together with 5 confirmed SPBs to start a long-term follow-up study (Aerts et al. 1999). From 1996 up to 1998, numerous high-resolution, high signal-to-noise spectra were taken with the CAT/CES combination at La Silla in order to study the line profile variations of the Si II-doublet centered at 4130 Å.We report our finding that at least 8 of 17 targets turn out to be spectroscopic binaries. We have found a large variety in the obtained orbits. HD 123515 and HD 140873 were known as single-lined spectroscopic binaries, but both turn out to be double-lined. All the others binaries are single-lined. For HD 140873 and HD 177863, we find orbits with large eccentricities of respectively e = 0.731 α 0.006 and e = 0.603 α 0.007. HD 69144, HD 92287 and HD 169978 are three binaries with circular orbits and very short orbital periods (a few days). Since their photometric measurements are dominated by (close to) sinusoidal variations with twice the orbital frequency, these stars are ellipsoidal variables. Their orbital periods are of the same order of magnitude as the expected periods of pulsation.After removing the orbit, we find the same first frequency in the residual radial velocities as in the gathered photometric measurements for 6 stars. For HD 69144 and HD 169978 we did not yet succeed in deriving an intrinsic period, although HD 69144 has prominent line profile variations. For HD 169978, we have serious doubts about the SPB nature.For a detailed description, we refer to De Cat et al. (1999).

scholarly journals Extrasolar planets and brown dwarfs around AF-type stars

2019 ◽  
Vol 621 ◽  
pp. A87 ◽  
Author(s):  
S. Borgniet ◽  
A.-M. Lagrange ◽  
N. Meunier ◽  
F. Galland ◽  
L. Arnold ◽  
...  
Keyword(s):  
Main Sequence ◽  
Extrasolar Planets ◽  
Giant Planet ◽  
High Amplitude ◽  
Stellar Mass ◽  
Occurrence Rate ◽  
Substellar Companions ◽  
Orbital Periods ◽  
The Impact

Context. The impact of stellar mass on the properties of giant planets is still not fully understood. Main-sequence (MS) stars more massive than the Sun remain relatively unexplored in radial velocity (RV) surveys, due to their characteristics which hinder classical RV measurements. Aims. Our aim is to characterize the close (up to ~2 au) giant planet (GP) and brown dwarf (BD) population around AF MS stars and compare this population to stars with different masses. Methods. We used the SOPHIE spectrograph located on the 1.93 m telescope at Observatoire de Haute-Provence to observe 125 northern, MS AF dwarfs. We used our dedicated SAFIR software to compute the RV and other spectroscopic observables. We characterized the detected substellar companions and computed the GP and BD occurrence rates combining the present SOPHIE survey and a similar HARPS survey. Results. We present new data on two known planetary systems around the F5-6V dwarfs HD 16232 and HD 113337. For the latter, we report an additional RV variation that might be induced by a second GP on a wider orbit. We also report the detection of 15 binaries or massive substellar companions with high-amplitude RV variations or long-term RV trends. Based on 225 targets observed with SOPHIE and/or HARPS, we constrain the BD frequency within 2–3 au around AF stars to be below 4% (1σ). For Jupiter-mass GPs within 2–3 au (periods ≤103 days), we find the occurrence rate to be 3.7−1+3% around AF stars with masses <1.5 M⊙, and to be ≤6% (1σ) around AF stars with masses >1.5 M⊙. For periods shorter than 10 days, we find the GP occurrence rate to be below 3 and 4.5% (1σ), respectively. Our results are compatible with the GP frequency reported around FGK dwarfs and are compatible with a possible increase in GP orbital periods with stellar mass as predicted by formation models.

scholarly journals Taming the binaries

2007 ◽  
Vol 3 (S248) ◽  
pp. 59-65 ◽  
Author(s):  
D. Pourbaix
Keyword(s):  
Orbital Period ◽  
Spectroscopic Binaries ◽  
Time Interval ◽  
Gold Mine ◽  
Single Star ◽  
Orbital Inclination ◽  
Orbital Parameters ◽  
Binary Model ◽  
Ideal Situation ◽  
Unique Source

AbstractAstrometric binaries are both a gold mine and a nightmare. They are a gold mine because they are sometimes the unique source of orbital inclination for spectroscopic binaries, thus making it possible for astrophysicists to get some clues about the mass of the often invisible secondary. However, this is an ideal situation in the sense that one benefits from the additional knowledge that it is a binary for which some orbital parameters are somehow secured (e.g. the orbital period). On the other hand, binaries are a nightmare, especially when their binary nature is not established yet. Indeed, in such cases, depending on the time interval covered by the observations compared to the orbital period, either the parallax or the proper motion can be severely biased if the successive positions of the binary are modelled assuming it is a single star. With large survey campaigns sometimes monitoring some stars for the first time ever, it is therefore crucial to design robust reduction pipelines in which such troublesome objects are quickly identified and either removed or processed accordingly. Finally, even if an object is known not to be a single star, the binary model might turn out not to be the most appropriate for describing the observations. These different situations will be covered.

scholarly journals TATOO: Tidal-chronology standalone tool to estimate the age of massive close-in planetary systems

2020 ◽  
Vol 641 ◽  
pp. A38
Author(s):  
F. Gallet
Keyword(s):  
Orbital Period ◽  
Planetary System ◽  
Interpolation Method ◽  
Planetary Systems ◽  
Central Star ◽  
Numerical Code ◽  
Mass Star ◽  
Stellar Rotation ◽  
Orbital Periods ◽  
The Impact

Context. The presence of a massive close-in planet with an orbital period of a few days or less around a low-mass star can possibly result in a strong variation in the properties of the central star. Indeed, star-planet tidal interactions generate exchanges of angular momentum that can result in tidal spin-up. This effect could then lead to gyrochronological ages biased towards younger ages. Aims. This article provides the community with TATOO, a standalone tool based on tidal-chronology, with which to estimate the age of a massive close-in planetary system using only its observed properties: mass of the planet and the star, stellar rotation, and planetary orbital periods. Methods. I used a star-planet tidal evolution numerical code to create a large multi-parametric grid of the evolution of synthetic star-planet systems. Furthermore, using the tidal-chronology technique, I employed a 3D interpolation method to provide a fairly precise age estimate of any given planetary system composed of one massive close-in planet. Results. About half of the planetary systems investigated in this work are subject to tidal spin-up bias. I pointed out that this bias linearly scales with the ratio between rotation and orbital period, making this quantity a useful proxy to rapidly investigate whether tidal-chronology needs to be used. Moreover, while being model dependent, TATOO can also be used even if no rotational departure is present. In that case, it gives results in agreement with the classical gyrochronological analysis. Conclusions. TATOO is a useful tool specifically designed for massive close-in planetary systems that can also be used as a classical gyrochronological tool. For now it is the only publicly available software to estimate the age of massive close-in planetary systems subject to tidal spin-up. In that sense, tidal-chronology can be seen as a first order correction of the impact of tidal interaction on gyrochronology.

scholarly journals Post-AGB Discs from Common-Envelope Evolution

Galaxies ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 97 ◽  
Author(s):  
Robert Izzard ◽  
Adam Jermyn
Keyword(s):  
Stellar Population ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Population Synthesis ◽  
Common Envelope ◽  
Disc Model ◽  
Type Interaction ◽  
Orbital Periods ◽  
The Impact ◽  
Disc Formation

Post-asymptotic giant branch (post-AGB) stars with discs are all binaries. Many of these binaries have orbital periods between 100 and 1000 days so cannot have avoided mass transfer between the AGB star and its companion, likely through a common-envelope type interaction. We report on preliminary results of our project to model circumbinary discs around post-AGB stars using our binary population synthesis code binary_c. We combine a simple analytic thin-disc model with binary stellar evolution to estimate the impact of the disc on the binary, and vice versa, fast enough that we can model stellar population and hence explore the rather uncertain parameter space involved with disc formation. We find that, provided the discs form with sufficient mass and angular momentum, and have an inner edge that is relatively close to the binary, they can both prolong the life of their parent post-AGB star and pump the eccentricity of orbits of their inner binaries.

scholarly journals Disc-binary interactions in depleted post-AGB binaries

2020 ◽  
Vol 642 ◽  
pp. A234
Author(s):  
Glenn-Michael Oomen ◽  
Onno Pols ◽  
Hans Van Winckel ◽  
Gijs Nelemans
Keyword(s):  
Asymptotic Giant Branch ◽  
Binary Interaction ◽  
Chemical Abundances ◽  
Tidal Interaction ◽  
Eccentric Orbits ◽  
Model Predictions ◽  
Orbital Periods ◽  
Red Giant ◽  
Binary Orbit ◽  
The Impact

Binary post-asymptotic giant branch (post-AGB) stars have orbital periods in the range of 100−2500 days in eccentric orbits. They are surrounded by circumbinary dusty discs. They are the immediate result of unconstrained binary interaction processes. Their observed orbital properties do not correspond to model predictions: Neither the periods nor the high eccentricities are expected. Indeed, many orbits are eccentric despite the strong tidal interaction when the primary had giant dimensions on the red giant branch and AGB. Our goal is to investigate if interactions between a binary and its circumbinary disc during the post-AGB phase can result in their eccentric orbits, while simultaneously explaining the chemical anomaly known as depletion. For this paper, we selected three binaries (EP Lyr, RU Cen, HD 46703) with well-constrained orbits, luminosities, and chemical abundances. We used the MESA code to evolve post-AGB models, while including the accretion of metal-poor gas. This allows us to constrain the evolution of the stars and study the impact of circumbinary discs on the orbital properties of the models. We investigate the effect of torques produced by gas inside the binary cavity and the effect of Lindblad resonances on the orbit, while also including the tidal interaction following the equilibrium tide model. We find that none of our models are able to explain the high orbital eccentricities of the binaries in our sample. The accretion torque does not significantly impact the binary orbit, while Lindblad resonances can pump the eccentricity up to only e ≈ 0.2. At higher eccentricities, the tidal interaction becomes too strong, so the high observed eccentricities cannot be reproduced. However, even if we assume tides to be ineffective, the eccentricities in our models do not exceed ≈0.25. Finally, the orbit of RU Cen is too wide to reproduce with disc-binary interactions by starting from a circular orbit. We conclude that either our knowledge of disc-binary interactions is still incomplete, or the binaries must have left their phase of strong interaction in an eccentric orbit.

scholarly journals The TESS-Keck Survey. VIII. Confirmation of a Transiting Giant Planet on an Eccentric 261 Day Orbit with the Automated Planet Finder Telescope*

2022 ◽  
Vol 163 (2) ◽  
pp. 61
Author(s):  
Paul A. Dalba ◽  
Stephen R. Kane ◽  
Diana Dragomir ◽  
Steven Villanueva ◽  
Karen A. Collins ◽  
...  
Keyword(s):  
Orbital Period ◽  
Giant Planet ◽  
Giant Planets ◽  
Orbital Eccentricity ◽  
Exciting Potential ◽  
Tentative Evidence ◽  
Orbital Periods ◽  
Low Irradiation ◽  
Transit Method

Abstract We report the discovery of TOI-2180 b, a 2.8 M J giant planet orbiting a slightly evolved G5 host star. This planet transited only once in Cycle 2 of the primary Transiting Exoplanet Survey Satellite (TESS) mission. Citizen scientists identified the 24 hr single-transit event shortly after the data were released, allowing a Doppler monitoring campaign with the Automated Planet Finder telescope at Lick Observatory to begin promptly. The radial velocity observations refined the orbital period of TOI-2180 b to be 260.8 ± 0.6 days, revealed an orbital eccentricity of 0.368 ± 0.007, and discovered long-term acceleration from a more distant massive companion. We conducted ground-based photometry from 14 sites spread around the globe in an attempt to detect another transit. Although we did not make a clear transit detection, the nondetections improved the precision of the orbital period. We predict that TESS will likely detect another transit of TOI-2180 b in Sector 48 of its extended mission. We use giant planet structure models to retrieve the bulk heavy-element content of TOI-2180 b. When considered alongside other giant planets with orbital periods over 100 days, we find tentative evidence that the correlation between planet mass and metal enrichment relative to stellar is dependent on orbital properties. Single-transit discoveries like TOI-2180 b highlight the exciting potential of the TESS mission to find planets with long orbital periods and low irradiation fluxes despite the selection biases associated with the transit method.

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