Observational Selection in Binary-Star Eccentricities

Harrington, R. S.; Miranian, Mihran

doi:10.1086/130139

Cited by 9 publications

(11 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Previous observations of spectroscopic (Duquennoy & Mayor 1991) and visual (Harrington & Miranian 1977) solar-type binaries have indicated a thermal eccentricity distribution. However, these studies recovered the thermal eccentricity distribution only after applying large and uncertain correction factors for incompleteness.…”

Section: Eb Trendsmentioning

confidence: 92%

Early-Type Eclipsing Binaries With Intermediate Orbital Periods

Moe

Stefano

2015

ApJ

View full text Add to dashboard Cite

We analyze 221 eclipsing binaries (EBs) in the Large Magellanic Cloud with B-type main-sequence (MS) primaries (M 1 ≈ 4 -14 M ⊙ ) and orbital periods P = 20 -50 days that were photometrically monitored by the Optical Gravitational Lensing Experiment. We utilize our three-stage automated pipeline to (1) classify all 221 EBs, (2) fit physical models to the light curves of 130 detached well-defined EBs from which unique parameters can be determined, and (3) recover the intrinsic binary statistics by correcting for selection effects. We uncover two statistically significant trends with age. First, younger EBs tend to reside in dustier environments with larger photometric extinctions, an empirical relation that can be implemented when modeling stellar populations. Second, younger EBs generally have large eccentricities. This demonstrates that massive binaries at moderate orbital periods are born with a Maxwellian "thermal" orbital velocity distribution, which indicates they formed via dynamical interactions. In addition, the age-eccentricity anticorrelation provides a direct constraint for tidal evolution in highly eccentric binaries containing hot MS stars with radiative envelopes. The intrinsic fraction of B-type MS stars with stellar companions q = M 2 /M 1 > 0.2 and orbital periods P = 20 -50 days is (7 ± 2)%. We find early-type binaries at P = 20 -50 days are weighted significantly toward small mass ratios q ≈ 0.2 -0.3, which is different than the results from previous observations of closer binaries with P < 20 days. This indicates that early-type binaries at slightly wider orbital separations have experienced substantially less competitive accretion and coevolution during their formation in the circumbinary disk.

show abstract

Section: Eb Trendsmentioning

confidence: 92%

Early-Type Eclipsing Binaries With Intermediate Orbital Periods

Moe

Stefano

2015

ApJ

View full text Add to dashboard Cite

show abstract

“…Harrington & Miranian (1977) demonstrate that it is relatively more difficult to measure the orbital elements of VBs that have large eccentricities e0.7. A subsample of VBs that have reliable orbital solutions is therefore biased toward smaller eccentricities.…”

Section: Definitionsmentioning

confidence: 98%

“…As discussed in Section 2, catalogs of VBs with reliable orbital solutions are biased against systems with large eccentricities (Harrington & Miranian 1977;Tokovinin & Kiyaeva 2016). We can nonetheless use VB orbit catalogs to measure a lower limit to the power-law slope η of the eccentricity distribution.…”

Section: Eccentricity Distributionmentioning

confidence: 99%

“…At 3<log P<4 and 4<log P<5, however, three and two detected companions, respectively, do not have measured eccentricities. VBs that do not have reliable orbital solutions generally have large eccentricities e0.7 (Harrington & Miranian 1977;Tokovinin & Kiyaeva 2016). We assume that the five VBs with intermediate periods 3<log P<5 but without orbital solutions are evenly distributed across e≈0.70-0.95 (green systems in Figure 32).…”

Section: Eccentricity Distributionmentioning

confidence: 99%

See 1 more Smart Citation

Mind Your Ps and Qs: The Interrelation between Period (P) and Mass-ratio (Q) Distributions of Binary Stars

Moe

Stefano

2017

ApJS

1,093

1,200

View full text Add to dashboard Cite

We compile observations of early-type binaries identified via spectroscopy, eclipses, long-baseline interferometry, adaptive optics, common proper motion, etc. Each observational technique is sensitive to companions across a narrow parameter space of orbital periods P and mass ratios q=M comp /M 1 . After combining the samples from the various surveys and correcting for their respective selection effects, we find that the properties of companions to O-type and B-type main-sequence (MS) stars differ among three regimes. First, at short orbital periods P20days (separations a0.4 au), the binaries have small eccentricities e0.4, favor modest mass ratios á ñ » q 0.5, and exhibit a small excess of twins q>0.95. Second, the companion frequency peaks at intermediate periods log P (days)≈3.5 (a ≈ 10 au), where the binaries have mass ratios weighted toward small values q≈0.2-0.3 and follow a Maxwellian "thermal" eccentricity distribution. Finally, companions with long orbital periods log P (days)≈5.5-7.5 (a ≈ 200-5000 au) are outer tertiary components in hierarchical triples and have a mass ratio distribution across q≈0.1-1.0 that is nearly consistent with random pairings drawn from the initial mass function. We discuss these companion distributions and properties in the context of binary-star formation and evolution. We also reanalyze the binary statistics of solar-type MS primaries, taking into account that 30% ±10% of single-lined spectroscopic binaries likely contain white dwarf companions instead of low-mass stellar secondaries. The mean frequency of stellar companions with q>0.1 and log P (days)<8.0 per primary increases from 0.50±0.04 for solar-type MS primaries to 2.1±0.3 for O-type MS primaries. We fit joint probability density functions ¹ ( ) ( ) ( ) ( ) ( ) f M q P e f M f q f P f e , , , 1 1 to the corrected distributions, which can be incorporated into binary population synthesis studies.

show abstract

“…Such an orbit would be difficult to observe at just the right times needed for a good fit and would also appear to be less appealing for continued monitoring. Harrington & Miranian (1977) investigated this bias by generating 10 3 random orbits and classifying the expected quality of the orbit fit by eye, relying on their extensive experience working with such astrometric data. Such an ad hoc method is necessary because in the marginal cases of visual binary orbit fitting the process of χ 2 minimization is highly nonlinear and strongly dependent on the initial guess.…”

Section: Selecting a Minimally Biased Samplementioning

confidence: 99%

On the Distribution of Orbital Eccentricities for Very Low-Mass Binaries

Dupuy

Liu

2011

ApJ

View full text Add to dashboard Cite

We have compiled a sample of 16 orbits for very low-mass stellar (< 0.1 M ⊙ ) and brown dwarf binaries, including updated orbits for HD 130948BC and LP 415-20AB. This sample enables the first comprehensive study of the eccentricity distribution for such objects. We find that very low-mass binaries span a broad range of eccentricities from near-circular to highly eccentric (e ≈ 0.8), with a median eccentricity of 0.34. We have examined potential observational biases in this sample, and for visual binaries we show through Monte Carlo simulations that if we choose appropriate selection criteria then all eccentricities are equally represented ( 5% difference between input and output eccentricity distributions). The orbits of this sample of very low-mass binaries show some significant differences from their solar-type counterparts. They lack a correlation between orbital period and eccentricity and display a much higher fraction of nearcircular orbits (e < 0.1) than solar-type stars, which together may suggest a different formation mechanism or dynamical history for these two populations. Very low-mass binaries also do not follow the e 2 distribution of Ambartsumian (1937), which would be expected if their orbits were distributed in phase space according to a function of energy alone (e.g., the Boltzmann distribution). We find that current numerical simulations of very low-mass star formation do not completely reproduce the observed properties of our binary sample. The cluster formation model of Bate (2009a) agrees very well with the overall e distribution, but the lack of any high-e (> 0.6) binaries at orbital periods comparable to our sample suggests that tidal damping due to gas disks may play too large of a role in the simulations. In contrast, the circumstellar disk fragmentation model of Stamatellos & Whitworth (2009) predicts only high-e binaries and thus is highly inconsistent with our sample. These discrepancies could be explained if multiple formation processes are responsible for producing the field population.

show abstract

Observational Selection in Binary-Star Eccentricities

Abstract: Observational selection effects on the distribution of eccentricities in binary-star orbits are examined by monitoring the selection of orbits from a randomly generated sample. Selection effects fully explain the difference between predicted and observed eccentricity distributions.

Cited by 9 publications

References 0 publications

Early-Type Eclipsing Binaries With Intermediate Orbital Periods

Early-Type Eclipsing Binaries With Intermediate Orbital Periods

Mind Your Ps and Qs: The Interrelation between Period (P) and Mass-ratio (Q) Distributions of Binary Stars

On the Distribution of Orbital Eccentricities for Very Low-Mass Binaries

Contact Info

Product

Resources

About