Effects of Metallicity on the Rotational Velocities of Massive Stars

Penny, Laura R.; Sprague, Amanda J.; Seago, George; Gies, Douglas R.

doi:10.1086/425573

Cited by 37 publications

(45 citation statements)

References 29 publications

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“…However, recent direct observations of V sin i for O-type stars in the Magellanic Clouds (MCs) which have low metallicities reveal that distributions of rotational velocities for MC stars and Galactic stars are similar, and do not support these predictions (Penny et al 2004). As discussed, elemental abundances in the LMC also have no signature of stellar rotation different from Galactic stars.…”

Section: Stellar Rotationmentioning

confidence: 90%

Implications of elemental abundances in dwarf spheroidal galaxies

Tsujimoto¹

2006

A&A

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Unusual elemental abundance patterns observed for stars belonging to nearby dwarf spheroidal (dSph) galaxies are discussed. Analysis of the [α/H] vs. [Fe/H] diagrams where α represents Mg or an average of α-elements reveals that Fe from type Ia supernovae (SNe Ia) does not contribute to the stellar abundances in the dSph galaxies where the member stars exhibit low α/Fe ratios except for the most massive dSph galaxy, Sagitarrius. The more massive dwarf (irregular) galaxy, the Large Magellanic Cloud, also has an SNe Ia signature in the stellar abundances. These findings suggest that whether SNe Ia contribute to chemical evolution in dwarf galaxies is likely to depend on the mass scale of galaxies. Unusual Mg abundances in some dSph stars are also found to be the origin of the large scatter in the [Mg/Fe] ratios and are responsible for a seemingly decreasing [Mg/Fe] feature with increasing [Fe/H]. In addition, the lack of massive stars in the dSph galaxies does not satisfactorily account for the low-α signature. Considering the assembly of deficient elements (O, Mg, Si, Ca, Ti and Zn), all of which are synthesized in pre-SN massive stars and in SN explosions, the low-α signature appears to reflect the heavy-element yields of massive stars with less rotation compared to solar neighborhood stars.

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Section: Stellar Rotationmentioning

confidence: 90%

Implications of elemental abundances in dwarf spheroidal galaxies

Tsujimoto¹

2006

A&A

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“…(Morgan et al 1955), O9 Vn: (Feast et al 1957), O9 V:n (Walborn 1973), O8/9 V (Houk & Cowley 1975), O9 Vnp (Garrison et al 1977), and O9.5 III (Mathys 1988). The star is fast-rotating, the projected radial velocity amounting 280−300 km s −1 (Penny 1996;Howarth et al 1997;Penny et al 2004). The star is known to have strong nitrogen lines for its spectral type (Garrison et al 1977;Schild 1985;Howarth & Prinja 1989).…”

Section: O-type Starsmentioning

confidence: 99%

β Cephei stars in the ASAS-3 data

Pigulski¹,

Pojmański²

2007

A&A

126

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Context. The β Cephei stars have been studied for over a hundred years. Despite this, many interesting problems related to this class of variable stars remain unsolved. Fortunately, these stars seem to be well-suited to asteroseismology. Hence, the results of seismic analysis of β Cephei stars should help us to better understand pulsations and the main sequence evolution of massive stars, particularly the effect of rotation on mode excitation and internal structure. It is therefore extremely important to increase the sample of known β Cephei stars and select targets that are useful for asteroseismology. Aims. We analysed ASAS-3 photometry of bright early-type stars with the goal of finding new β Cephei stars. We were particularly interested in β Cephei stars that would be good for seismic analysis, i.e., stars that (i) have a large number of excited modes; (ii) show rotationally split modes; (iii) are components of eclipsing binary systems; (iv) have low-frequency modes, that is, are hybrid β Cephei/SPB stars. Methods. Our study was made with a homogeneous sample of over 4100 stars having MK spectral type B5 or earlier. For these stars, the ASAS-3 photometry was analysed by means of a Fourier periodogram. Results. We have discovered 103 β Cephei stars, nearly doubling the number of previously known stars of this type. Among these stars, four are components of eclipsing binaries, seven have modes equidistant or nearly equidistant in frequency. In addition, we found five β Cephei stars that show low-frequency periodic variations, very likely due to pulsations. We therefore regard them as candidate hybrid β Cephei/SPB pulsators. All these stars are potentially very useful for seismic modeling. Moreover, we found β Cephei-type pulsations in three late O-type stars and fast period changes in one, HD 168050.

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“…In contrast, stars with a magnetic field stronger than 400 G would become slowly rotating magnetic B stars. In the LMC and other environments of low metallicity, the magnetic field has less braking impact on the velocity as explained by Penny et al (2004) due to the lower abundances of metals. It may explain why Be stars in the LMC can initially rotate with higher velocities than in the MW, as shown in Fig.…”

Section: Star-formation Conditions and Magnetic Fieldmentioning

confidence: 99%

Effects of metallicity, star-formation conditions, and evolution in B and Be stars

Martayan¹,

Frémat

Hubert³

et al. 2006

A&A

104

117

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Aims. To statistically study the effects of the metallicity, star-formation conditions, and evolution on the behaviour of massive stars and, more particularly, of B and Be stars, we observed large samples of stars in the Magellanic Clouds for the first time. In this article we present the first part of this study. Methods. Spectroscopic observations of hot stars belonging to the young cluster LMC-NGC 2004 and its surrounding region were carried out with the VLT-GIRAFFE facilities in MEDUSA mode. We determined the fundamental parameters (T eff , log g, V sin i, and radial velocity) for all B and Be stars in the sample thanks to a code developed in our group. The effect of fast rotation (stellar flattening and gravitational darkening) are taken into account in this study. We also determined the age of observed clusters. We then compared the mean V sin i obtained for field and cluster B and Be stars in the Large Magellanic Cloud (LMC) with the ones in the Milky Way (MW). Results. We find, in particular, that Be stars rotate faster in the LMC than in the MW, in the field as well as in clusters. We discuss the relations between V sin i, metallicity, star-formation conditions, and stellar evolution by comparing the LMC with the MW. We conclude that Be stars began their main sequence life with an initial rotational velocity higher than the one for B stars. It is probable that only part of the B stars, those with a sufficient initial rotational velocity, can become Be stars. This result may explain the differences in the proportion of Be stars in clusters with similar ages.

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Effects of Metallicity on the Rotational Velocities of Massive Stars

Cited by 37 publications

References 29 publications

Implications of elemental abundances in dwarf spheroidal galaxies

Implications of elemental abundances in dwarf spheroidal galaxies

β Cephei stars in the ASAS-3 data

Effects of metallicity, star-formation conditions, and evolution in B and Be stars

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