scholarly journals Low-eccentricity migration of ultra-short-period planets in multiplanet systems

2019 ◽  
Vol 488 (3) ◽  
pp. 3568-3587 ◽  
Author(s):  
Bonan Pu ◽  
Dong Lai
Keyword(s):  
Initial Period ◽  
Large Population ◽  
Fine Tuning ◽  
Population Synthesis ◽  
Tidal Dissipation ◽  
Orbital Decay ◽  
Short Period ◽  
Migration Mechanism ◽  
Mutual Inclination ◽  
Low Mass

ABSTRACT Recent studies suggest that ultra-short-period planets (USPs), Earth-sized planets with sub-day periods, constitute a statistically distinct sub-sample of Kepler planets: USPs have smaller radii (1–1.4R⊕) and larger mutual inclinations with neighbouring planets than nominal Kepler planets, and their period distribution is steeper than longer period planets. We study a ‘low-eccentricity’ migration scenario for the formation of USPs, in which a low-mass planet with initial period of a few days maintains a small but finite eccentricity due to secular forcings from exterior companion planets, and experiences orbital decay due to tidal dissipation. USP formation in this scenario requires that the initial multiplanet system have modest eccentricities (≳0.1) or angular momentum deficit. During the orbital decay of the innermost planet, the system can encounter several apsidal and nodal precession resonances that significantly enhance eccentricity excitation and increase the mutual inclination between the inner planets. We develop an approximate method based on eccentricity and inclination eigenmodes to efficiently evolve a large number of multiplanet systems over Gyr time-scales in the presence of rapid (as short as ∼100 yr) secular planet–planet interactions and other short-range forces. Through a population synthesis calculation, we demonstrate that the ‘low-e migration’ mechanism can naturally produce USPs from the large population of Kepler multis under a variety of conditions, with little fine-tuning of parameters. This mechanism favours smaller inner planets with more massive and eccentric companion planets, and the resulting USPs have properties that are consistent with observations.

scholarly journals An Evolutionary Scenario for Short Period (≤10 Days) Millisecond Binary Pulsars

1996 ◽  
Vol 158 ◽  
pp. 473-474
Author(s):  
E. Ergma ◽  
M. J. Sarna ◽  
J. Antipova
Keyword(s):  
Main Sequence ◽  
Initial Period ◽  
Compact Object ◽  
Roche Lobe ◽  
Binary Pulsars ◽  
Evolutionary Scenario ◽  
Conservative Evolution ◽  
Short Period ◽  
Low Mass ◽  
X Ray Binaries

We present numerical calculations that simulate the evolution of a low mass (1M⊙) star transfering mass to a compact object (Muslimov & Sarna 1993; Ergma & Sarna 1996). Mass transfer starts when the secondary turns off the main sequence (having a small helium core). We have calculated 14 evolutionary sequences with the assumption of non-conservative or conservative evolution. We can conclude that near the bifurcation point the evolution is very sensitive to: (i) the assumption of conservative or non-conservative evolution, (ii) the structure of the mass losing star. Small changes in the initial period when the secondary fills its Roche lobe will lead to large changes in the final period and final mass of the remnant. Presently there are 40 known low-mass binary pulsars (LMBP). The evolutionary scenario for the wider systems (10 < Porb(d) < 1000) is connected with that of wide low-mass X-ray binaries (LMXB) in which the donor star will fill its Roche lobe after helium core formation.

scholarly journals The Spitzer search for the transits of HARPS low-mass planets

2010 ◽  
Vol 6 (S276) ◽  
pp. 167-170
Author(s):  
Michaël Gillon ◽  
Brice-Olivier Demory ◽  
Drake Deming ◽  
Sara Seager ◽  
Christophe Lovis ◽  
...  
Keyword(s):  
Large Population ◽  
High Signal ◽  
Signal To Noise ◽  
Close Orbit ◽  
Short Period ◽  
First Results ◽  
Nearby Stars ◽  
Low Mass ◽  
Set Up

AbstractRadial velocity, microlensing and transit surveys have revealed the existence of a large population of low-mass planets in our Galaxy, the so-called ‘Super-Earths’ and ‘Neptunes’. The understanding of these objects would greatly benefit from the detection of a few of them transiting bright nearby stars, making possible their thorough characterization with high signal-to-noise follow-up measurements. Our HARPS Doppler survey has now detected dozens of low-mass planets in close orbit around bright nearby stars, and it is highly probable that a few of them do transit their host star. In this context, we have set up an ambitious Spitzer program devoted to the search for the transits of the short period low-mass planets detected by HARPS. We present here this program and some of its first results.

scholarly journals Planetary Nebulae in M31: Abundances, and comparison with bright Planetary Nebulae in the LMC

1997 ◽  
Vol 180 ◽  
pp. 475-476
Author(s):  
M. G. Richer ◽  
G. Stasińska ◽  
M. L. McCall
Keyword(s):  
Planetary Nebula ◽  
Luminosity Function ◽  
Large Population ◽  
Wavelength Region ◽  
Planetary Nebulae ◽  
Surprising Result ◽  
Population Synthesis ◽  
Abundance Distribution ◽  
Wide Range ◽  
The Mean

We have obtained spectra of 28 planetary nebulae in the bulge of M31 using the MOS spectrograph at the Canada-France-Hawaii Telescope. Typically, we observed the [O II] λ3727 to He I λ5876 wavelength region at a resolution of approximately 1.6 å/pixel. For 19 of the 21 planetary nebulae whose [OIII]λ5007 luminosities are within 1 mag of the peak of the planetary nebula luminosity function, our oxygen abundances are based upon a measured [OIII]λ4363 intensity, so they are based upon a measured electron temperature. The oxygen abundances cover a wide range, 7.85 dex < 12 + log(O/H) < 9.09 dex, but the mean abundance is surprisingly low, 12 + log(O/H)–8.64 ± 0.32 dex, i.e., roughly half the solar value (Anders & Grevesse 1989). The distribution of oxygen abundances is shown in Figure 1, where the ordinate indicates the number of planetary nebulae with abundances within ±0.1 dex of any point on the x-axis. The dashed line indicates the mean abundance, and the dotted lines indicate the ±1 σ points. The shape of this abundance distribution seems to indicate that the bulge of M31 does not contain a large population of bright, oxygen-rich planetary nebulae. This is a surprising result, for various population synthesis studies (e.g., Bica et al. 1990) have found a mean stellar metallicity approximately 0.2 dex above solar. This 0.5 dex discrepancy leads one to question whether the mean stellar metallicity is as high as the population synthesis results indicate or if such metal-rich stars produce bright planetary nebulae at all. This could be a clue concerning the mechanism responsible for the variation in the number of bright planetary nebulae observed per unit luminosity in different galaxies (e.g., Hui et al. 1993).

scholarly journals V392 Orionis: Observations and Evolutionary State of a Low-Mass System

1998 ◽  
Vol 11 (1) ◽  
pp. 371-371
Author(s):  
S. Narusawa ◽  
A. Yamasaki ◽  
Y. Nakamura
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Circumstellar Matter ◽  
Small Mass ◽  
Primary Component ◽  
Close Binary ◽  
Mass System ◽  
Future Evolution ◽  
Short Period ◽  
Low Mass

Although the evolution of binary systems has been qualitatively interpreted with the evolutionary scenario, the quantitative interpretation of any observed system is still unsatisfactory due to the difficulty of the quantitative treatment of mass and angular momentum transfer/loss. To reach a true understanding of the evolution of binary systems, we have to accumulate more observational evidence. So far, we have observed several binaries that are short-period and noncontact, and found the existence of extremely small-mass systems. In the present paper, we study another short-period (P=0.659d), noncontact, eclipsing binary system, V392 Ori. We have made photometric and spectroscopic observations of V392 Ori. The light curves are found to vary, suggesting the existence of circumstellar matter around the system. Combining the photometric and spectroscopic results, we obtain parameters describing the system; we find the mass of the primary component is only 0.6Mʘ- undermassive for its spectral and luminosity class A5V, suggesting that a considerable amount of its original mass has been lost from the system during the course of evolution. The low-mass problem is very important for investigation of the evolution of close binary systems: largemass loss within and/or after the main-sequence will have a significant influence on the future evolution of binary systems.

scholarly journals Tidal dissipation in rotating low-mass stars and implications for the orbital evolution of close-in planets

2017 ◽  
Vol 604 ◽  
pp. A112 ◽  
Author(s):  
F. Gallet ◽  
E. Bolmont ◽  
S. Mathis ◽  
C. Charbonnel ◽  
L. Amard
Keyword(s):  
Orbital Evolution ◽  
Low Mass Stars ◽  
Tidal Dissipation ◽  
Low Mass

scholarly journals The low-mass pre-main sequence population of Scorpius OB1

2018 ◽  
Vol 615 ◽  
pp. A148 ◽  
Author(s):  
Francesco Damiani
Keyword(s):  
Total Mass ◽  
Main Sequence ◽  
Near Infrared ◽  
Large Population ◽  
X Ray ◽  
Uv Excess ◽  
Low Mass ◽  
Ob Associations ◽  
The Rich ◽  
A New Technique

Context. The low-mass members of OB associations, expected to be a major component of their total population, are in most cases poorly studied because of the difficulty of selecting these faint stars in crowded sky regions. Our knowledge of many OB associations relies on only a relatively small number of massive members. Aims. We study here the Sco OB1 association, with the aim of a better characterization of its properties, such as global size and shape, member clusters and their morphology, age and formation history, and total mass. Methods. We use deep optical and near-infrared (NIR) photometry from the VPHAS+ and VVV surveys, over a wide area (2.6° × 2.6°), complemented by Spitzer infrared (IR) data, and Chandra and XMM-Newton X-ray data. A new technique is developed to find clusters of pre-main sequence M-type stars using suitable color-color diagrams, complementing existing selection techniques using narrow-band Hα photometry or NIR and ultraviolet (UV) excesses, and X-ray data. Results. We find a large population of approximately 4000 candidate low-mass Sco OB1 members whose spatial properties correlate well with those of Hα-emission, NIR-excess, UV-excess, and X-ray detected members, and unresolved X-ray emission. The low-mass population is spread among several interconnected subgroups: they coincide with the HII regions G345.45+1.50 and IC4628, and the rich clusters NGC 6231 and Trumpler 24, with an additional subcluster intermediate between these two. The total mass of Sco OB1 is estimated to be ~ 8500 M⊙. Indication of a sequence of star-formation events is found, from South (NGC 6231) to North (G345.45+1.50). We suggest that the diluted appearance of Trumpler 24 indicates that the cluster is now dissolving into the field, and that tidal stripping by NGC 6231 nearby contributes to the process.

scholarly journals The diverse origin of exoplanets' eccentricities & inclinations

2010 ◽  
Vol 6 (S276) ◽  
pp. 221-224
Author(s):  
Eric B. Ford
Keyword(s):  
Rotation Axis ◽  
Orbital Evolution ◽  
Giant Planets ◽  
Direct Imaging ◽  
Wide Binary ◽  
Hot Jupiters ◽  
Short Period ◽  
New Type ◽  
Low Mass ◽  
Diverse Origin

AbstractRadial velocity surveys have discovered over 400 exoplanets. While measuring eccentricities of low-mass planets remains a challenge, giant exoplanets display a broad range of orbital eccentricities. Recently, spectroscopic measurements during transit have demonstrated that the short-period giant planets (“hot-Jupiters”) also display a broad range of orbital inclinations (relative to the rotation axis of the host star). Both properties pose a challenge for simple disk migration models and suggest that late-stage orbital evolution can play an important role in determining the final architecture of planetary systems. One possible formation mechanism for the inclined hot-Jupiters is some form of eccentricity excitation (e.g., planet scattering, secular perturbations due to a distant planet or wide binary) followed tidal circularization. The planet scattering hypothesis also makes predictions for the population of planets at large separations. Recent discoveries of planets on wide orbits via direct imaging and highly anticipated results from upcoming direct imaging campaigns are poised to provide a new type of constraint on planet formation. This proceedings describes recent progress in understanding the formation of giant exoplanets.

scholarly journals The Census of Exoplanets in Visual Binaries: Population Trends from a Volume-Limited Gaia DR2 and Literature Search

2021 ◽  
Vol 8 ◽  
Author(s):  
Clémence Fontanive ◽  
Daniella Bardalez Gagliuffi
Keyword(s):  
Planetary Systems ◽  
Multiple Star ◽  
Multiple Systems ◽  
Binary Separation ◽  
Extensive Search ◽  
Short Period ◽  
Massive Component ◽  
Low Mass ◽  
Cool Gas ◽  
Gaia Dr2

We present results from an extensive search in the literature and Gaia DR2 for visual co-moving binary companions to stars hosting exoplanets and brown dwarfs within 200 pc. We found 218 planet hosts out of the 938 in our sample to be part of multiple-star systems, with 10 newly discovered binaries and 2 new tertiary stellar components. This represents an overall raw multiplicity rate of 23.2 ± 1.6 % for hosts to exoplanets across all spectral types, with multi-planet systems found to have a lower stellar duplicity frequency at the 2.2-σ level. We found that more massive hosts are more often in binary configurations, and that planet-bearing stars in multiple systems are predominantly observed to be the most massive component of stellar binaries. Investigations of the multiplicity of planetary systems as a function of planet mass and separation revealed that giant planets with masses above 0.1 MJup are more frequently seen in stellar binaries than small sub-Jovian planets with a 3.6-σ difference, a trend enhanced for the most massive (&gt;7 MJup) short-period (&lt;0.5 AU) planets and brown dwarf companions. Binarity was however found to have no significant effect on the demographics of low- mass planets (&lt;0.1 MJup) or warm and cool gas giants (&gt;0.5 AU). While stellar companion mass appears to have no impact on planet properties, binary separation seems to be an important factor in the resulting structure of planetary systems. Stellar companions on separations &lt;1000 AU can play a role in the formation or evolution of massive, close-in planets, while planets in wider binaries show similar properties to planets orbiting single stars. Finally, our analyses indicate that numerous stellar companions on separations smaller than 1–3 arcsec likely remain undiscovered to this date. Continuous efforts to complete our knowledge of stellar multiplicity on separations of tens to hundreds of AU are essential to confirm the reported trends and further our understanding of the roles played by multiplicity on exoplanets.

scholarly journals Characterization of rocky exoplanets from their infrared phase curve

2010 ◽  
Vol 6 (S276) ◽  
pp. 485-486
Author(s):  
Anne-Sophie Maurin ◽  
Franck Selsis ◽  
Franck Hersant ◽  
Marco Delbò
Keyword(s):  
Thermal Emission ◽  
Infrared Emission ◽  
Phase Curve ◽  
Low Mass Stars ◽  
Rotation Surface ◽  
Key Population ◽  
Short Period ◽  
Low Mass ◽  
Observation Geometry

AbstractDuring the last few years, observations have yielded an abundant population of short-period planets under 15 Earth masses. Among those, hot terrestrial exoplanets represent a key population to study the survival of dense atmospheres close to their parent star. Thermal emission from exoplanets orbiting low-mass stars will be observable with the next generation of infrared telescopes, in particular the JWST. In order to constrain planetary and atmospheric properties, we have developed models to simulate the variation of the infrared emission along the path of the orbit (IR phase curve) for both airless planets and planets with dense atmospheres. Here, we focus on airless planets and present preliminary results on the influence of orbital elements, planet rotation, surface properties and observation geometry. Then, using simulated noisy phase curves, we test the retrieval of planets' properties and identify the degeneracies.

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