scholarly journals HD 76920 b pinned down: A detailed analysis of the most eccentric planetary system around an evolved star

2021 ◽  
Vol 38 ◽  
Author(s):  
C. Bergmann ◽  
M. I. Jones ◽  
J. Zhao ◽  
A. J. Mustill ◽  
R. Brahm ◽  
...  
Keyword(s):  
Spectroscopic Analysis ◽  
Planetary System ◽  
Continuous Phase ◽  
Minimum Mass ◽  
Orbital Elements ◽  
Stellar Envelope ◽  
Orbital Decay ◽  
Fundamental Stellar Parameters ◽  
Transit Probability ◽  
Gaia Dr2

Abstract We present 63 new multi-site radial velocity (RV) measurements of the K1III giant HD 76920, which was recently reported to host the most eccentric planet known to orbit an evolved star. We focused our observational efforts on the time around the predicted periastron passage and achieved near-continuous phase coverage of the corresponding RV peak. By combining our RV measurements from four different instruments with previously published ones, we confirm the highly eccentric nature of the system and find an even higher eccentricity of $e=0.8782 \pm 0.0025$ , an orbital period of $415.891^{+0.043}_{-0.039}\,\textrm{d}$ , and a minimum mass of $3.13^{+0.41}_{-0.43}\,\textrm{M}_{\textrm{J}}$ for the planet. The uncertainties in the orbital elements are greatly reduced, especially for the period and eccentricity. We also performed a detailed spectroscopic analysis to derive atmospheric stellar parameters, and thus the fundamental stellar parameters ( $M_*, R_*, L_*$ ), taking into account the parallax from Gaia DR2, and independently determined the stellar mass and radius using asteroseismology. Intriguingly, at periastron, the planet comes to within 2.4 stellar radii of its host star’s surface. However, we find that the planet is not currently experiencing any significant orbital decay and will not be engulfed by the stellar envelope for at least another 50–80 Myr. Finally, while we calculate a relatively high transit probability of 16%, we did not detect a transit in the TESS photometry.

scholarly journals A Bayesian neural network predicts the dissolution of compact planetary systems

2021 ◽  
Vol 118 (40) ◽  
pp. e2026053118
Author(s):  
Miles Cranmer ◽  
Daniel Tamayo ◽  
Hanno Rein ◽  
Peter Battaglia ◽  
Samuel Hadden ◽  
...  
Keyword(s):  
Neural Network ◽  
Machine Learning ◽  
Time Series ◽  
Planetary System ◽  
Machine Learning Algorithms ◽  
Orbital Elements ◽  
Bayesian Neural Network ◽  
Inference Model ◽  
Link Type ◽  
Numerical Integrator

We introduce a Bayesian neural network model that can accurately predict not only if, but also when a compact planetary system with three or more planets will go unstable. Our model, trained directly from short N-body time series of raw orbital elements, is more than two orders of magnitude more accurate at predicting instability times than analytical estimators, while also reducing the bias of existing machine learning algorithms by nearly a factor of three. Despite being trained on compact resonant and near-resonant three-planet configurations, the model demonstrates robust generalization to both nonresonant and higher multiplicity configurations, in the latter case outperforming models fit to that specific set of integrations. The model computes instability estimates up to 105 times faster than a numerical integrator, and unlike previous efforts provides confidence intervals on its predictions. Our inference model is publicly available in the SPOCK (https://github.com/dtamayo/spock) package, with training code open sourced (https://github.com/MilesCranmer/bnn_chaos_model).

scholarly journals High reddening patches in Gaia DR2

2020 ◽  
Vol 634 ◽  
pp. A33
Author(s):  
Leire Beitia-Antero ◽  
Ana Inés Gómez de Castro ◽  
Raúl de la Fuente Marcos
Keyword(s):  
Star Formation ◽  
Milky Way ◽  
Spectroscopic Analysis ◽  
Galactic Halo ◽  
Spiral Galaxies ◽  
Monte Carlo Sampling ◽  
The Other ◽  
Host Galaxies ◽  
Galactic Model ◽  
Gaia Dr2

Context. Deep GALEX UV data show that the extreme outskirts of some spiral galaxies are teeming with star formation. Such young stellar populations evolving so far away from the bulk of their host galaxies challenge our overall understanding of how star formation proceeds at galactic scales. It is at present unclear whether our own Milky Way may also exhibit ongoing and recent star formation beyond the conventional edge of the disk (∼15 kpc). Aims. Using Gaia DR2 data, we aim to determine if such a population is present in the Galactic halo, beyond the nominal radius of the Milky Way disk. Methods. We studied the kinematics of Gaia DR2 sources with parallax values between 1/60 and 1/30 milliarcseconds towards two regions that show abnormally high values of extinction and reddening; the results are compared with predictions from GALAXIA Galactic model. We also plotted the color–magnitude (CM) diagrams with heliocentric distances computed inverting the parallaxes, and studied the effects of the large parallax errors by Monte Carlo sampling. Results. The kinematics point towards a Galactic origin for one of the regions, while the provenance of the stars in the other is not clear. A spectroscopic analysis of some of the sources in the first region confirms that they are located in the halo. The CM diagram of the sources suggests that some of them are young.

scholarly journals Contrast analysis between the trajectory of the planetary system and the periodicity of solar activity

2017 ◽  
Vol 35 (3) ◽  
pp. 659-669 ◽  
Author(s):  
Wei Sun ◽  
Jian Wang ◽  
JinRu Chen ◽  
Ying Wang ◽  
GuangMing Yu ◽  
...  
Keyword(s):  
Solar Activity ◽  
Solar System ◽  
Planetary System ◽  
Period Change ◽  
The Sun ◽  
Relative Movement ◽  
Orbital Elements ◽  
Periodic Movement ◽  
Contrast Analysis ◽  
The Relationship

Abstract. The relationship between the periodic movement of the planetary system and its influence on solar activity is currently a serious topic in research. The kinematic index of the planet juncture index has been developed to find the track and variation of the Sun around the centroid of the solar system and the periodicity of solar activity. In the present study, the kinematic index of the planetary system's heliocentric longitude, developed based on the orbital elements of planets in the solar system, and it is used to investigate the periodic movement of the planetary system. The kinematic index of the planetary system's heliocentric longitude and that of the planet juncture index are simulated and analyzed. The numerical simulation of the two kinematic indexes shows orderly orbits and disorderly orbits of 49.9 and 129.6 years, respectively. Two orderly orbits or two disorderly orbits show a period change rule of 179.5 years. The contrast analysis between the periodic movement of the planetary system and the periodicity of solar activity shows that the two phenomena exhibit a period change rule of 179.5 years. Moreover, orderly orbits correspond to high periods of solar activity and disorderly orbits correspond to low periods of solar activity. Therefore, the relative movement of the planetary system affects solar activity to some extent. The relationship provides a basis for discussing the movement of the planetary system and solar activity.

scholarly journals Orbital determination and dynamics of resonant extrasolar planetary systems

2007 ◽  
Vol 3 (S249) ◽  
pp. 427-440 ◽  
Author(s):  
C. Beaugé ◽  
S. Ferraz-Mello ◽  
T. A. Michtchenko ◽  
C. A. Giuppone
Keyword(s):  
Planetary System ◽  
Planetary Systems ◽  
Orbital Evolution ◽  
Dynamical Analysis ◽  
Dynamical Structure ◽  
Mean Motion Resonances ◽  
Orbital Decay ◽  
Complementary Part ◽  
Resonant Systems ◽  
Orbital Determination

AbstractIn this communication we review some properties and applications of mean-motion resonances in extrasolar planetary systems, with particular emphasis on the 2/1 commensurability. A first part is devoted to the dynamical structure of the 2/1 resonance, including (but not restricted to) the so-called apsidal corotations. In a second part we discuss the orbital evolution of resonant systems under the effects of non-conservative forces. Special attention is given to the use of apsidal corotations as markers of largescale orbital decay, possibly due to disk-planet interactions in primordial times. Finally, we analyze the interplay between dynamical analysis and orbital fitting. Using the HD82943 planetary system as an example, we discuss: (i) up to what point present orbital fits allow us to distinguish between different resonant configurations, and (ii) in what ways may the dynamical structure of resonances be used as a complementary part of the orbital fitting process.

scholarly journals Asteroid belt survival through stellar evolution: dependence on the stellar mass

2020 ◽  
Vol 494 (1) ◽  
pp. L17-L21 ◽  
Author(s):  
Rebecca G Martin ◽  
Mario Livio ◽  
Jeremy L Smallwood ◽  
Cheng Chen
Keyword(s):  
Stellar Evolution ◽  
White Dwarfs ◽  
Main Sequence ◽  
Planetary System ◽  
Asteroid Belt ◽  
High Radiation ◽  
The Past ◽  
Orbital Decay ◽  
Low Mass ◽  
Intense Radiation

ABSTRACT Polluted white dwarfs are generally accreting terrestrial-like material that may originate from a debris belt like the asteroid belt in the Solar system. The fraction of white dwarfs that are polluted drops off significantly for white dwarfs with masses $M_{\rm WD}\gtrsim 0.8\, \rm M_\odot$. This implies that asteroid belts and planetary systems around main-sequence (MS) stars with mass $M_{\rm MS}\gtrsim 3\, \rm M_\odot$ may not form because of the intense radiation from the star. This is in agreement with current debris disc and exoplanet observations. The fraction of white dwarfs that show pollution also drops off significantly for low-mass white dwarfs $(M_{\rm WD}\lesssim 0.55\, \rm M_\odot)$. However, the low-mass white dwarfs that do show pollution are not currently accreting but have accreted in the past. We suggest that asteroid belts around MS stars with masses $M_{\rm MS}\lesssim 2\, \rm M_\odot$ are not likely to survive the stellar evolution process. The destruction likely occurs during the AGB phase and could be the result of interactions of the asteroids with the stellar wind, the high radiation, or, for the lowest mass stars that have an unusually close-in asteroid belt, scattering during the tidal orbital decay of the inner planetary system.

scholarly journals Do the planets in the HD 34445 system really exist?

2019 ◽  
Vol 488 (3) ◽  
pp. 3818-3825
Author(s):  
Nikolaos Georgakarakos ◽  
Ian Dobbs-Dixon
Keyword(s):  
Time Scales ◽  
Parameter Space ◽  
Numerical Experiments ◽  
Planetary System ◽  
Dynamical Evolution ◽  
Orbital Elements ◽  
Large Area ◽  
Open Question ◽  
Orbital Solution ◽  
Different Time Scales

ABSTRACT In 2010 the first planet was discovered around star HD 34445. Recently, another five planets were announced orbiting the same star. It is a rather dense multiplanet system with some of its planets having separations of fractions of an au and minimum masses ranging from Neptune to sub-Jupiter ones. Given the number of planets and the various uncertainties in their masses and orbital elements, the HD 34445 planetary system is quite interesting as there is the potential for mean motion and secular resonances that could render the outcome of its dynamical evolution and fate an open question. In this paper we investigate the dynamical stability of the six-planet system in order to check the validity of the orbital solution acquired. This is achieved by a series of numerical experiments, where the dynamical evolution of the system is tested on different time-scales. We vary the orbital elements and masses of the system within the error ranges provided. We find that for a large area of the parameter space we can produce stable configurations and therefore conclude it is very likely that the HD 34445 planetary system is real. Some discussion about the potential habitability of the system is also done.

scholarly journals Transit timing variations in the WASP-4 planetary system

2019 ◽  
Vol 490 (3) ◽  
pp. 4230-4236 ◽  
Author(s):  
John Southworth ◽  
M Dominik ◽  
U G Jørgensen ◽  
M I Andersen ◽  
V Bozza ◽  
...  
Keyword(s):  
Planetary System ◽  
Planetary Systems ◽  
Time Effect ◽  
High Confidence ◽  
Stellar Activity ◽  
The Third ◽  
Orbital Decay ◽  
Systemic Velocity ◽  
Rule Out ◽  
Hot Jupiter

ABSTRACT Transits in the planetary system WASP-4 were recently found to occur 80 s earlier than expected in observations from the TESS satellite. We present 22 new times of mid-transit that confirm the existence of transit timing variations, and are well fitted by a quadratic ephemeris with period decay dP/dt = −9.2 ± 1.1 ms yr−1. We rule out instrumental issues, stellar activity, and the Applegate mechanism as possible causes. The light-time effect is also not favoured due to the non-detection of changes in the systemic velocity. Orbital decay and apsidal precession are plausible but unproven. WASP-4 b is only the third hot Jupiter known to show transit timing variations to high confidence. We discuss a variety of observations of this and other planetary systems that would be useful in improving our understanding of WASP-4 in particular and orbital decay in general.

scholarly journals The TOI-763 system: sub-Neptunes orbiting a Sun-like star

2020 ◽  
Vol 498 (3) ◽  
pp. 4503-4517
Author(s):  
M Fridlund ◽  
J Livingston ◽  
D Gandolfi ◽  
C M Persson ◽  
K W F Lam ◽  
...  
Keyword(s):  
Light Curve ◽  
Orbital Period ◽  
Planetary System ◽  
Space Mission ◽  
The Sun ◽  
Minimum Mass ◽  
Dwarf Star ◽  
Stellar Spectrum ◽  
Transit Signals

ABSTRACT We report the discovery of a planetary system orbiting TOI-763(aka CD-39 7945), a V = 10.2, high proper motion G-type dwarf star that was photometrically monitored by the TESS space mission in Sector 10. We obtain and model the stellar spectrum and find an object slightly smaller than the Sun, and somewhat older, but with a similar metallicity. Two planet candidates were found in the light curve to be transiting the star. Combining TESS transit photometry with HARPS high-precision radial velocity (RV) follow-up measurements confirm the planetary nature of these transit signals. We determine masses, radii, and bulk densities of these two planets. A third planet candidate was discovered serendipitously in the RV data. The inner transiting planet, TOI-763 b, has an orbital period of Pb  =  5.6 d, a mass of Mb  =  9.8 ± 0.8 M⊕, and a radius of Rb  =  2.37 ± 0.10 R⊕. The second transiting planet, TOI-763 c, has an orbital period of Pc  =  12.3 d, a mass of Mc  =  9.3 ± 1.0 M⊕, and a radius of Rc  =  2.87 ± 0.11 R⊕. We find the outermost planet candidate to orbit the star with a period of ∼48 d. If confirmed as a planet, it would have a minimum mass of Md  =  9.5 ± 1.6 M⊕. We investigated the TESS light curve in order to search for a mono transit by planet d without success. We discuss the importance and implications of this planetary system in terms of the geometrical arrangements of planets orbiting G-type stars.

scholarly journals A white dwarf bound to the transiting planetary system WASP-98

2020 ◽  
Vol 497 (4) ◽  
pp. 4416-4422
Author(s):  
John Southworth ◽  
Pier-Emmanuel Tremblay ◽  
Boris T Gänsicke ◽  
Daniel Evans ◽  
Teo Močnik
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Planetary System ◽  
Planetary Systems ◽  
Precise Determination ◽  
Spectral Lines ◽  
Low Metallicity ◽  
Gaia Dr2 ◽  
Rule Out

ABSTRACT WASP-98 is a planetary system containing a hot Jupiter transiting a late-G dwarf. A fainter star, 12 arcsec away, has previously been identified as a white dwarf, with a distance and proper motion consistent with a physical association with the planetary system. We present spectroscopy of the white dwarf, with the aim of determining its mass, radius, and temperature and hence the age of the system. However, the spectra show the featureless continuum and lack of spectral lines characteristic of the DC class of white dwarfs. We therefore fitted theoretical white dwarf spectra to the ugriz apparent magnitudes and Gaia DR2 parallax of this object in order to determine its physical properties and the age of the system. We find that the system is old, with a lower limit of 3.6 Gyr, but theoretical uncertainties preclude a precise determination of its age. Its kinematics are consistent with membership of the thick disc, but do not allow us to rule out the thin-disc alternative. The old age and low metallicity of the system suggest that it is subject to an age–metallicity relation, but analysis of the most metal-rich and metal-poor transiting planetary systems yields only insubstantial evidence of this. We conclude that the study of bound white dwarfs can yield independent ages to planetary systems, but such analysis may be better suited to DA and DB rather than DC white dwarfs.

scholarly journals A STUDY OF THE TIME VARIABILITY AND LINE PROFILE VARIATIONS OF κ DRA

2021 ◽  
Vol 57 (1) ◽  
pp. 91-105
Author(s):  
S. M. Saad ◽  
M. I. Nouh ◽  
A. Shokry ◽  
I. Zead
Keyword(s):  
Line Profile ◽  
Orbital Period ◽  
Circular Orbit ◽  
Spectroscopic Analysis ◽  
Emission Lines ◽  
Time Variability ◽  
Line Profiles ◽  
Orbital Elements ◽  
Balmer Lines ◽  
Be Star

We present a spectroscopic analysis of the bright Be star Κ Dra. Two independent sets of radial velocity (RV) measurements were obtained by direct measurement and using a line profile disentangling technique. By combining solutions from codes FOTEL and KOREL, we derived improved orbital elements. From the RVs of the Balmer lines and also from some strong metallic lines we found that all RV variations are phase-locked with the orbital period. V/R variations were obtained for Hα, Hβ, Hγ and some other photospheric lines. A moving absorption bump superposed over the emission line profiles was detected. The orbital solutions for Κ Dra were derived assuming a circular orbit with a period P = 61d.5549 and K = 6.81 km s−1. We failed to find absorption or emission lines for the unresolved secondary component.

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