The space frequency and origin of the runaway O and B stars

Stone, R. C.

doi:10.1086/115880

Cited by 137 publications

(154 citation statements)

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“…About 10%-30% of O/early B stars are "runaway stars" that have large peculiar velocities v≈50-200kms −1 and are found in isolation removed from young clusters/associations (Gies 1987;Stone 1991;Hoogerwerf et al 2001). Hoogerwerf et al (2001) discuss the two preferred formation channels of runaway OB stars.…”

Section: Binary-star Evolutionmentioning

confidence: 99%

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

Moe

Stefano

2017

ApJS

1,149

1,200

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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.

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Section: Binary-star Evolutionmentioning

confidence: 99%

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

Moe

Stefano

2017

ApJS

1,149

1,200

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“…According to Garmany (1994), the frequency depends on spectral type, the fraction of early type field stars varying from ∼40% for stars hotter than B2 to 25% for O stars only. The majority of field objects are runaway stars identified from their high velocities (Blaauw 1961;Stone 1991) while the rest cannot be related to any group and might therefore be true field stars born outside clusters. Some of the runaway stars can convincingly be associated with the birth of radio pulsars (Hoogerwerf et al 2001) and were thus ejected from their parent associations in the supernova explosion in a massive binary.…”

Section: The Possible Age and Birth Place Of Rx J13086+2127mentioning

confidence: 99%

Proper motions of thermally emitting isolated neutron stars measured with Chandra

Motch¹,

Pires

Haberl

et al. 2009

A&A

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The remarkable astrometric capabilities of the Chandra Observatory offer the possibility to measure proper motions of X-ray sources with an unprecedented accuracy in this wavelength range. We recently completed a proper motion survey of three of the seven thermally emitting radio-quiet isolated neutron stars (INSs) discovered in the ROSAT all-sky survey. These INSs (RX J0420.0−5022, RX J0806.4−4123 and RX J1308.6+2127) either lack an optical counterpart or have one so faint that ground based or space born optical observations push the current possibilities of the instrumentation to the limit. Pairs of ACIS observations were acquired 3 to 5 years apart to measure the displacement of the sources on the X-ray sky using as a reference the background of extragalactic or remote Galactic X-ray sources. We derive 2σ upper limits of 123 mas yr −1 and 86 mas yr −1 on the proper motion of RX J0420.0−5022 and RX J0806.4−4123, respectively. RX J1308.6+2127 exhibits a very significant displacement (∼9σ) yielding μ = 220 ± 25 mas yr −1 , the second fastest measured among all ROSAT-discovered INSs. The source is probably moving away rapidly from the Galactic plane at a speed which precludes any significant accretion of matter from the interstellar medium. Its transverse velocity of ∼740 (d/700 pc) km s −1 might be the largest of all ROSAT INSs and its corresponding spatial velocity lies among the fastest recorded for neutron stars. RX J1308.6+2127 is thus a middle-aged (age ∼1 My) high velocity cooling neutron star. We investigate its possible origin in nearby OB associations or from a field OB star. In most cases, the flight time from birth place appears significantly shorter than the characteristic age derived from spin down rate. Overall, the distribution in transverse velocity of the ROSAT INSs is not statistically different from that of normal radio pulsars.

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“…This value strongly argues against a runaway status for this star. Indeed, according to the criteria of Stone (1991), the peculiar velocity threshold for a star to be a runaway is about 40 km s −1 . It has been suggested by Gies & Bolton (1986) that the runaway status was erroneously attributed to stars such as HD 192281 because of their huge wind velocity that yield a large negative RV for those spectral lines that are at least partly formed in the wind.…”

Section: Hd 192281mentioning

confidence: 99%

Line profile variability in the spectra of Oef stars

Becker¹,

Rauw²

2004

A&A

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Abstract. We present the very first analysis of the spectroscopic variability of the three rapidly rotating Oef stars HD 192281 (O5(ef)), HD 14442 (O5.5ef) and HD 14434 (O6.5(ef)). Radial velocities of the He  λ 4541 line reveal no evidence of binarity on time scales of a few days, or from one year to the next, for any of the targets. The He  λ 4686 double-peaked emission and, to some extent, the Hβ absorption line display significant profile variability in the spectra of all three stars. Data gathered during different observing runs spread over six years reveal a rather stable time scale for HD 192281 and HD 14442, whereas the variability pattern changes significantly from one year to the other. The case of HD 14434 is less clear as no obvious time scale emerges from our analysis. In a tentative way to interpret this variability, stellar rotation remains a possible clock for HD 192281 and HD 14442. However, currently available models addressing stellar rotation fail to explain some crucial aspects of the observed variability behaviour, which appear to be even more complex in the case of HD 14434.

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The space frequency and origin of the runaway O and B stars

Cited by 137 publications

References 0 publications

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

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

Proper motions of thermally emitting isolated neutron stars measured with Chandra

Line profile variability in the spectra of Oef stars

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