Short-lived and Long-lived Outbursts in B and Be Stars from Hipparcos Photometry and Modelling

Hubert, A. M.; Floquet, M.; Zorec, J.

doi:10.1017/s0252921100056128

Cited by 20 publications

(18 citation statements)

References 5 publications

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“…The authors called these objects Type-1 stars. In the Galaxy there are also known Be stars showing outbursts: λ Eri, μ Cen, and those reported by Hubert & Floquet (1998) and Hubert, Floquet & Zorec (2000).…”

Section: Introductionsupporting

confidence: 57%

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Search for Southern Galactic Be Star Candidates

Sabogal

García-Varela

Mennickent

2014

Publications of the Astronomical Society of the Pacific

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ABSTRACT. We present the result of a search for southern Galactic Be star candidates within the group of miscellaneous variables of the ASAS-2 catalog of variable stars, using statistical, morphological, photometric, and color criteria. This search lead us to obtain a catalog of 213 new Be star candidates. The I-band light curves of these candidates show outbursts (Type-1 stars) only in 9% of the sample, and stochastic variations (Type-4 stars) in 91% of the sample. We do not find stars showing clear high and low states (Type-2 stars) or showing outbursts and high and low states simultaneously (Type-1/Type-2 stars). Our sample of southern Galactic Be star candidates provide valuable new bright targets for high resolution spectroscopic studies with small/medium size telescopes.

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Section: Introductionsupporting

confidence: 57%

“…While hundreds of outbursting (Type-1) Be stars have been found in the Magellanic Clouds (MCs), less than one hundred of them have been reported in the Galaxy (Hubert et al 1997;Hubert, Floquet, & Zorec 2000). Type-2 stars have been only reported in the MCs.…”

Section: Introductionmentioning

confidence: 99%

Search for Southern Galactic Be Star Candidates

Sabogal

García-Varela

Mennickent

2014

Publications of the Astronomical Society of the Pacific

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“…We should thus pay attention only on these amounts and conclude that the events labeled with log n = 0.0 and +0.2 are rather extreme and rarely observed. In this respect, we note that in the compilation made by Moujtahid et al (1998), which actually corresponds to spotted measurements concerning otherwise long-term Be-star "bumper" activity (Cook et al 1995;Hubert & Floquet 1998;Hubert et al 2000;Keller et al 2002;Mennickent et al 2002;de Wit et al 2006), the magnitude changes are of the order of 0.1 ∆V 0.2 mag and rarely as high as ∆V 0.5 mag.…”

Section: Discussionsupporting

confidence: 62%

Physical parameters of IPHAS-selected classical Be stars

Gkouvelis

Fabregat

Zorec

et al. 2016

A&A

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We present a semi-automatic procedure to obtain fundamental physical parameters and distances of classical Be (CBe) stars, based on the Barbier-Chalonge-Divan (BCD) spectrophotometric system. Our aim is to apply this procedure to a large sample of CBe stars detected by the IPHAS photometric survey, to determine their fundamental physical parameters and to explore their suitability as galactic structure tracers. In this paper we describe the methodology used and the validation of the procedure by comparing our results with those obtained from different independent astrophysical techniques for subsamples of stars in common with other studies. We also present a test case study of the galactic structure in the direction of the Perseus Galactic Arm, in order to compare our results with others recently obtained with different techniques and the same sample of stars. We did not find any significant clustering of stars at the expected positions of the Perseus and Outer Galactic Arms, in agreement with previous studies in the same area that we used for verification.

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“…Adding to this the steep drop of the IMF for masses M 15 M , the observed frequency of Be stars displays two maxima and becomes significant only in a limited range of stellar masses, i.e., 3 M/M 30. Nothing precludes, however, that continuous and variable winds implying mass-loss rateṡ M ∼ 10 −11 −10 −9 M /yr (Snow 1981) and episodic mass ejections up toṀ ∼ 10 −7 M /yr that are typical in Be stars (Brown & Wood 1992;Hanuscihk et al 1993;Floquet et al 2000;Hubert et al 2000;Keller et al 2002;Mennickent et al 2002;de Wit et al 2006;Meilland et al 2006) be present in more-and lessmassive rapidly rotating stars than in those of B spectral type considered in the present paper. The conclusions drawn in this work may also concern stars in these two mass extremes.…”

Section: Introductionmentioning

confidence: 73%

Critical study of the distribution of rotational velocities of Be stars

Zorec

Frémat

Souza

et al. 2016

A&A

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Context. Among intermediate-mass and massive stars, Be stars are the fastest rotators in the main sequence (MS) and, as such, these stars are a cornerstone to validate models of structure and evolution of rotating stars. Several phenomena, however, induce under-or overestimations either of their apparent Vsin i, or true velocity V. Aims. In the present contribution we aim at obtaining distributions of true rotational velocities corrected for systematic effects induced by the rapid rotation itself, macroturbulent velocities, and binarity. Methods. We study a set of 233 Be stars by assuming they have inclination angles distributed at random. We critically discuss the methods of Cranmer and Lucy-Richardson, which enable us to transform a distribution of projected velocities into another distribution of true rotational velocities, where the gravitational darkening effect on the Vsin i parameter is considered in different ways. We conclude that iterative algorithm by Lucy-Richardson responds at best to the purposes of the present work, but it requires a thorough determination of the stellar fundamental parameters. Results. We conclude that once the mode of ratios of the true velocities of Be stars attains the value V/V c 0.77 in the main-sequence (MS) evolutionary phase, it remains unchanged up to the end of the MS lifespan. The statistical corrections found on the distribution of ratios V/V c for overestimations of Vsin i, due to macroturbulent motions and binarity, produce a shift of this distribution toward lower values of V/V c when Be stars in all MS evolutionary stages are considered together. The mode of the final distribution obtained is at V/V c 0.65. This distribution has a nearly symmetric distribution and shows that the Be phenomenon is characterized by a wide range of true velocity ratios 0.3 V/V c 0.95. It thus suggests that the probability that Be stars are critical rotators is extremely low. Conclusions. The corrections attempted in the present work represent an initial step to infer indications about the nature of the Be-star surface rotation that will be studied in the second paper of this series.

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Short-lived and Long-lived Outbursts in B and Be Stars from Hipparcos Photometry and Modelling

Cited by 20 publications

References 5 publications

Search for Southern Galactic Be Star Candidates

Search for Southern Galactic Be Star Candidates

Physical parameters of IPHAS-selected classical Be stars

Critical study of the distribution of rotational velocities of Be stars

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