Chromospherically active stars. V - HD 91816=LR Hya: A double-lined BY Draconis type binary

Fekel, Francis C.; Gillies, Kim; Africano, J. L.; Quigley, R.

doi:10.1086/114893

Cited by 4 publications

(5 citation statements)

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“…This calls attention to the extent to which selection effects can influence results. Increasing f (q)s, with peaks near high q's were suggested by Lucy & Ricco (1979), among others, for close SBs; however, most studies with similar results (Garmany et al 1980;Abt & Levy 1985;Levato et al 1987;Fekel et al 1988) are based on samples composed A&A 525, A26 (2011) of close systems, where contact or mass exchange lead to loss of information on the original mass of the components. Bimodal distributions have been suggested by Trimble (1974), and as well by Abt & Levy (1976); finally, both q n and bimodal distributions were the results of model-fittings by Dabrowski & Beardsley (1977) and Trimble & Ostriker (1978).…”

Section: Introductionmentioning

confidence: 81%

The mass ratio and initial mass functions in spectroscopic binaries

Ducati

Penteado

Turcati

2010

A&A

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Context. Spectroscopic binaries are important in studies of binary star-formation, since original information linked to the forming stars, such as the mass ratio, can be kept in the system and observationally retrieved. Aims. We aim to derive the more probable mass ratio distributions, to test a possible Initial Mass Functions acting on the formation of spectroscopic binaries, and to derive the value of q 0 , the minimal mass ratio for which both binary components are simultaneously in the main sequence. Methods. The sample has 249 systems, selected from the Ninth Catalogue of Spectroscopic Binaries, with selection criteria that include only those systems with periods longer than four days and magnitudes brighter than m V = 7.0, and main-sequence primaries, to avoid mass exchange. Monte Carlo simulations of observational parameters were performed. We performed simulations by comparing an observational quantity, Y obs , equal to f (m)/m 1 , where f (m) is the mass function, to theoretical Y th , which is a function of the system inclination (assumed to be random), and of the mass ratio q = m 2 /m 1 . We considered a minimal mass ratio q 0 , which is the limiting condition, to ensure that both components are simultaneously on main sequence, avoiding evolutionary effects leading to mass exchange and loss of information on the original masses. Calculations were done using several q 0 values. The form of the distribution of mass ratios was studied by simulations of Y, involving several functions, with slopes which are increasing, decreasing, constant, or bimodal. Other simulations were done by the generation of stars following several initial mass function laws. We combined pairs of stars generated from different IMFs, assuming that binaries arise from the pairing of stars simultaneously formed. In this case, several values of q 0 were also used in the input equations. Results. Our results indicate that decreasing q distributions match better with observations and also that a unique IMF gives better fits to observations than a composite IMF, with a slope around 1.4, rather than the widely used 2.35 slope. Values of q 0 tend to be lower than what is suggested by previous studies, which point to q 0 around 0.2; all simulations suggest that q 0 values as low as 0.08 produce the best fits to observations.

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Section: Introductionmentioning

confidence: 81%

The mass ratio and initial mass functions in spectroscopic binaries

Ducati

Penteado

Turcati

2010

A&A

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“…In LR79, data for 9 binaries among the 17 BY Dra variables known at that time was cited as providing strong support for H s . Subsequently, at the suggestion of an anonymous referee, Fekel et al (1988) re-examined the evidence for a peak at q ≃ 1 on the basis of an enlarged sample of 20 BY Dra binaries. It turns out that the additional binaries fill in the interval (0.80,0.95), resulting in a roughly uniform distribution from 0.80 to 1.0, and so Fekel et al (1988) correctly report that there is no longer evidence for a sharp peak at q ≃ 1.…”

Section: By Draconis Binariesmentioning

confidence: 99%

“…Subsequently, at the suggestion of an anonymous referee, Fekel et al (1988) re-examined the evidence for a peak at q ≃ 1 on the basis of an enlarged sample of 20 BY Dra binaries. It turns out that the additional binaries fill in the interval (0.80,0.95), resulting in a roughly uniform distribution from 0.80 to 1.0, and so Fekel et al (1988) correctly report that there is no longer evidence for a sharp peak at q ≃ 1. Nevertheless, in view of the small sample size, it does not follow that H s must be rejected for the BY Dra binaries.…”

Section: By Draconis Binariesmentioning

confidence: 99%

Spectroscopic binaries with components of similar mass

Lucy

2006

A&A

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The assertion that there is an intrinsic excess of binaries with mass ratios q 1 -the twin hypothesis -is investigated. A strong version of this hypothesis (H s ), due to Lucy & Ricco (1979, AJ, 84, 401) and Tokovinin (2000, A&A, 360, 997), refers to a narrow peak in the distribution function ψ(q) for q > ∼ 0.95. A weak version (H w ), due to Halbwachs et al. (2003, A&A, 397, 159), refers to a broad peak for q > ∼ 0.8. Current data on SB2's is analysed and H s is found to be statistically significant for a sample restricted to orbits of high precision. But claims that H s is significant for binaries with special characteristics are not confirmed since the sample sizes are well below the minimum required for a reliable test. With regard to H w , additional observational evidence is not presented, but evidence to the contrary in the form of Hogeveen's (1992, Ap&SS, 196, 299) model of biased sampling with ψ ∝ q −2 is criticized. Specifically, his success in thus fitting catalogued data depends on implausible assumptions about the research methodologies of binary-star spectroscopists.

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“…The orbital parameters were determined by Fekel et al (1988) who suggested a K0V spectral type for both components. The photometric period of 3.1448 days, given in CABS, was reported by Bopp et al (1984), but following observation campaigns could not confirm that value.…”

Section: Lr Hya (Hd 91816)mentioning

confidence: 99%

Multiwavelength optical observations of chromospherically active binary systems

Montes

Fernández-Figueroa

Castro

et al. 2000

Astron. Astrophys. Suppl. Ser.

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Abstract. This is the third paper of a series aimed at studying the chromosphere of active binary systems using the information provided for several optical spectroscopic features. High resolution echelle spectra including all the optical chromospheric activity indicators from the Ca ii H & K to Ca ii IRT lines are analysed here for 16 systems. The chromospheric contribution in these lines has been determined using the spectral subtraction technique. Very broad wings have been found in the subtracted Hα profile of the very active star HU Vir. These profiles are well matched using a two-component Gaussian fit (narrow and broad) and the broad component can be interpreted as arising from microflaring. Red-shifted absorption features in the Hα line have been detected in several systems and excess emission in the blue wing of FG UMa was also detected. These features indicate that several dynamical processes, or a combination of them, may be involved. Using the E Hα /E Hβ ratio as a diagnostic we have detected prominence-like extended material viewed off the limb in many stars of the sample, and prominences viewed against the disk at some orbital phases in the dwarfs OU Gem and BF Lyn. The He i D 3 line has been detected as an absorption feature in mainly all the giants of the sample. Total filling-in of the He i D 3 , probably due to microflaring activity, is observed in HU Vir. Self-absorption with red asymmetry is detected in the Ca ii H & K lines of the giants 12 Cam, FG UMa and BM CVn. All the stars analysed show clear filled-in Ca ii IRT lines or even notable emission reversal. The small values of the E 8542 /E 8498 ratio we have found indicate Ca ii IRT emission arises from plage-like regions. Orbital phase modulation of the chromospheric emission has been detected in some systems, in the case of HU Vir evidence of an active longitude area has been found.

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Chromospherically active stars. V - HD 91816=LR Hya: A double-lined BY Draconis type binary

Cited by 4 publications

References 0 publications

The mass ratio and initial mass functions in spectroscopic binaries

The mass ratio and initial mass functions in spectroscopic binaries

Spectroscopic binaries with components of similar mass

Multiwavelength optical observations of chromospherically active binary systems

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