Spectroscopic binaries with components of similar mass

Lucy, L. B.

doi:10.1051/0004-6361:20065746

Cited by 69 publications

(79 citation statements)

References 16 publications

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“…Systems with low q provide much more stringent tests than binaries with nearly equal masses, and the parameters derived from the fitting of isochrones (if successful) are more accurate. The value of q obtained for ASAS-21 is lower than for most of the known double-lined binaries (Lucy 2006) and one of the lowest among late-type eclipsing systems. There is an additional difficulty in finding low-q binaries, which is the low brightness ratio of the binary components.…”

Section: Discussionmentioning

confidence: 59%

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Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue

Hełminiak

Konacki

Złoczewski

et al. 2011

A&A

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Aims. We present the results of our spectroscopic and photometric analysis of two newly discovered low-mass detached eclipsing binaries found in the All-Sky Automated Survey (ASAS) catalogue: ASAS J093814-0104.4 and ASAS J212954-5620.1. Methods. Using the Grating Instrument for Radiation Analysis with a Fibre-Fed Echelle (GIRAFFE) on the 1.9-m Radcliffe telescope at the South African Astronomical Observatory (SAAO) and the University College London Echelle Spectrograph (UCLES) on the 3.9-m Anglo-Australian Telescope, we obtained high-resolution spectra of both objects and derived their radial velocities (RVs) at various orbital phases. The RVs of both objects were measured with the two-dimensional cross-correlation technique (TODCOR) using synthetic template spectra as references. We also obtained V and I band photometry using the 1.0-m Elizabeth telescope at SAAO and the 0.4-m Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes (PROMPT) located at the Cerro Tololo Inter-American Observatory (CTIO). The orbital and physical parameters of the systems were derived with PHOEBE and JKTEBOP codes. We compared our results with several sets of widely-used isochrones. Results. Our multi-epoch photometric observations demonstrate that both objects show significant out-of-eclipse modulations, which vary in time. We believe that this effect is caused by stellar spots, which evolve on time scales of tens of days. For this reason, we constructed our models on the basis of photometric observations spanning short time scales (less than a month). Our modeling indicates that (1) ASAS J093814-0104.04 is a main sequence active system with nearly-twin components with masses of M 1 = 0.771 ± 0.033 M , M 2 = 0.768 ± 0.021 M and radii of R 1 = 0.772 ± 0.012 R and R 2 = 0.769 ± 0.013 R . (2) ASAS J212954-5620.1 is a main sequence active binary with component masses of M 1 = 0.833 ± 0.017 M , M 2 = 0.703 ± 0.013 M and radii of R 1 = 0.845 ± 0.012 R and R 2 = 0.718 ± 0.017 R . Conclusions. Both systems seem to confirm the well-known characteristic of active low-mass stars, for which the observed radii are larger and the temperatures lower than predicted by evolutionary models. Other parameters agree within errors with the models of main sequence stars. The time-varying spot configuration may imply a variable level of activity, which may manifest itself in small changes of the measured radii.

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Section: Discussionmentioning

confidence: 59%

“…According to Lucy (2006), there is a statistically significant narrow peak in the q distribution function for q > ∼ 0.95 (the strong twin hypothesis). Halbwachs et al (2003) also refer to a broad peak for q > ∼ 0.85, however this is still not confirmed.…”

Section: Spectroscopic Orbitsmentioning

confidence: 99%

Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue

Hełminiak

Konacki

Złoczewski

et al. 2011

A&A

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“…If HD 15137 has a "twin" companion with mass ratio q = M 2 /M 1 ∼ 0.95 (Pinsonneault & Stanek 2006;Lucy 2006), the system must have an improbably low i ∼ 6 • . The late O-type or early B-type companion would have spectral lines heavily blended with the primary star, making it difficult to detect from V r variations but possibly identifiable using Doppler tomography.…”

Section: Discussionmentioning

confidence: 99%

Multiwavelength Observations of the Runaway Binary Hd 15137

McSwain

Becker

Roberts

et al. 2010

The Astronomical Journal

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HD 15137 is an intriguing runaway O-type binary system that offers a rare opportunity to explore the mechanism by which it was ejected from the open cluster of its birth. Here, we present recent blue optical spectra of HD 15137 and derive a new orbital solution for the spectroscopic binary and physical parameters of the O star primary. We also present the first XMM-Newton observations of the system. Fits of the EPIC spectra indicate soft, thermal X-ray emission consistent with an isolated O star. Upper limits on the undetected hard X-ray emission place limits on the emission from a proposed compact companion in the system, and we rule out a quiescent neutron star (NS) in the propeller regime or a weakly accreting NS. An unevolved secondary companion is also not detected in our optical spectra of the binary, and it is difficult to conclude that a gravitational interaction could have ejected this runaway binary with a low mass optical star. HD 15137 may contain an elusive NS in the ejector regime or a quiescent black hole with conditions unfavorable for accretion at the time of our observations.

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“…This bias can be dramatic if the initial-mass-ratio distribution is flat, i.e. dN ∝ dq, or even worse if it favours the formation of binaries with equal masses (often referred to as the "twin peak", see e.g., Söderhjelm 2007;Lucy 2006;Simon & Obbie 2009). In this case, the intrinsic population of pre-CVs would be dominated by systems with relatively massive secondary stars.…”

Section: Mass Growth In Cvs?mentioning

confidence: 99%

Post common envelope binaries from SDSS

Zorotovic

Schreiber

Gänsicke

2011

A&A

300

336

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Context. We have known for a long time that many of the measured white dwarf (WD) masses in cataclysmic variables (CVs) significantly exceed the mean mass of single WDs. This was thought to be related to observational biases, but recent high-precision measurements of WD masses in a great number of CVs are challenging this interpretation. A crucial question in this context is whether the high WD masses seen among CVs are already imprinted in the mass distribution of their progenitors, i.e. among detached postcommon-envelope binaries (PCEBs) that consist of a WD and a main-sequence star. Aims. We review the measured WD masses of CVs, determine the WD-mass distribution of an extensive sample of PCEBs that are representative for the progenitors of the current CV population (pre-CVs) and compare both distributions. Methods. We calculate the CV formation time of the PCEBs in our sample by determining the post common-envelope (CE) and the main-sequence evolution of the binary systems and define a pre-CV to be a PCEB that evolves into a semi-detached configuration with stable mass transfer within less than the age of the Galaxy. Possible observational biases affecting the WD-mass distribution for the pre-CV and the CV samples are discussed. Results. The mean WD mass among CVs is M wd = 0.83 ± 0.23 M , much larger than that found for pre-CVs, M wd = 0.67 ± 0.21 M . Selection effects cannot explain the high WD masses observed in CVs. We also note that compared to the predictions of binary-population models, the observed fraction of He-core WDs is small both among CVs (≤10%) and pre-CVs (≤17 ± 8%). Conclusions. We suggest two possible explanations for the high WD masses among CVs, both of which imply substantial revisions to the standard model of CV evolution: either most CVs have formed above the orbital-period gap (which requires a high WD mass to initiate stable mass transfer or a previous phase of thermal-timescale mass transfer), or the mass of the WDs in CVs grows through accretion (which strongly disagrees with the predictions of classical nova models). Both options may imply that CVs contribute to the single-degenerate progenitors of type Ia supernovae. The number of He-core WDs in CVs (≤10%) is roughly consistent with the number of He-core WDs in pre-CVs (≤17 ± 8%). This indicates a low value of the CE efficiency.

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Spectroscopic binaries with components of similar mass

Cited by 69 publications

References 16 publications

Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue

Orbital and physical parameters of eclipsing binaries from the All-Sky Automated Survey catalogue

Multiwavelength Observations of the Runaway Binary Hd 15137

Post common envelope binaries from SDSS

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