An empirical H-gamma luminosity calibration for class V-III stars

Millward, C. G.; Walker, G. A. H.

doi:10.1086/190995

Cited by 29 publications

(15 citation statements)

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“…The effective temperature ( T eff ) and absolute magnitude ( M V ) of each star were assigned using tabulated scales from the compilation of Straizys & Kuriliene (1981). A good agreement was found between the adopted M V values and the absolute magnitudes derived using the empirical H γ – M V calibration from Millward & Walker (1985). We constructed the SED of the target stars (Fig.…”

Section: Resultsmentioning

confidence: 99%

Pre-main-sequence stars in the star-forming complex Sh 2-284

Cusano¹,

Ripepi²,

Alcalá³

et al. 2010

Monthly Notices of the Royal Astronomical Society

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Located at the Galactic anticentre, Sh 2-284 is an H ii region that harbours several young open clusters. Dolidze 25, a rare metal-poor (Z similar to 0.004) young cluster, is one of these. Given its association with Sh 2-284, it is reasonable to assume a low metallicity for the whole H ii region. Sh 2-284 is expected to host a significant population of pre-main-sequence (PMS) stars of both low and intermediate mass (Herbig Ae stars). We aim to characterize these stars by means of a spectroscopic and photometric survey conducted with VIMOS@VLT and complemented with additional optical and infrared observations. In this survey we selected and characterized 23 PMS objects. We derived the effective temperature, the spectral energy distribution and luminosity of these objects, and, using theoretical PMS evolutionary tracks with the appropriate metallicity, we estimated the mass and the age of the studied objects. We also estimated a distance of 4 kpc for Sh 2-284, using the spectroscopic parallax of three OB stars. From the age determination we concluded that triggered star formation is occurring in this region. Our results show that a significant fraction of the young stellar objects (YSOs) may have preserved their disc/envelopes, in contrast with what is found in other recent studies of low-metallicity star-forming regions in the Galaxy. Finally, among the 23 bona fide PMS stars, we identified eight stars that are good candidates to be pulsators of the delta Scuti type

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Section: Resultsmentioning

confidence: 99%

Pre-main-sequence stars in the star-forming complex Sh 2-284

Cusano¹,

Ripepi²,

Alcalá³

et al. 2010

Monthly Notices of the Royal Astronomical Society

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“…Since the details of their parameter search strategy are unfortunately not described in Peterson et al (2006), we focus here on Aufdenberg et al's (2006) study. In our opinion, a critical assumption they made is that the apparent bolometric luminosity of Vega (57 L ) is nothing but superficial (due to a view-angle-dependent effect in a gravity-darkened poleon rapid rotator), while its true luminosity should be 37.7 L (which they considered typical for a slowly rotating A0 V star according to Millward & Walker 1985). With this presupposition, Vega must rotate very fast in order to make the temperature (or the brightness) near the pole high enough to produce such a large apparent excess in the luminosity.…”

Section: Comparison With Previous Studiesmentioning

confidence: 99%

“…Frankly speaking, their approach for seeking solutions seems rather questionable, because their fundamental assumption that Vega should have a true luminosity of 37.7 L is not convincing. That is, the M V data they quote from Millward & Walker (1985) is an averaged value for A0 V stars in general, which are actually an assembly of stars with a rather large diversity of stellar parameters (mass, age, metallicity, etc. ), because of inevitable uncertainties involved in the spectral classification.…”

Section: Comparison With Previous Studiesmentioning

confidence: 99%

Rotational Feature of Vega Revealed from Spectral Line Profiles

Takeda

Kawanomoto

Ohishi

2008

ApJ

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In order to establish Vega's absolute rotational velocity, v e , as distinct from the inclination angle, i, we conducted a detailed profile study on a large number ($200) of weak lines based on very high signal-to-noise ratio spectrum data, making use of the fact that the lines' characteristic shapes may contain information about rotation-induced gravity darkening. To this end, we developed computer programs to simulate the surface of a rapid rotator with latitudedependent atmospheric parameters, from which the spectral energy distribution (SED) and the detailed line profile can be computed. Having restricted the freedom of the parameters according to the requirements of the SED, we concluded by comparing the observed and theoretical profiles that v e ' 175 km s À1 (with i ' 7 ) is the best solution. It was also found that the abundances derived from lines showing peculiar flat-bottom shapes (e.g., Fe i lines) tend to be overestimated by up to $0.2 dex when the conventional method of analysis using classical model atmospheres is applied, although this effect is less significant for lines showing normal profiles (e.g., high-excitation Fe ii lines).

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“…We have included data for OB stars in the larger environs of the Cepheid, with the UBV data for these stars taken from Klare & Neckel ( 1977) and Schild, Garrison & Hiltner ( 1983). Absolute magnitudes M v for these stars were derived as in Turner ( 1986 ) by using Klare & Neckel's Hß indices with the W( H7 ) calibration of Millward & Walker (1985), and by adjusting the final values for rotational effects assuming V sin i values for each star typical of the average for the star's spectral type (Fukuda 1982) or, if the star was designated spectroscopically as n or nn, assuming that Vsin i > 250 km s -1 . This technique has been applied to B stars in NGC 129 by Turner, Forbes, & Pedreros ( 1992) with reasonable success.…”

Section: Sjv Velorummentioning

confidence: 99%

A search for OB associates near southern long-period Cepheids. IV - XY Carinae, GT Carinae, WZ Sagittarii, and SW Velorum

Turner¹,

Bergh²,

Younger³

et al. 1993

ApJS

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We report UBVphotometry for fields surrounding four long-period Cepheids in the Southern Milky Way. No potential early-type companions are detected around XY Car, which appears to be relatively isolated. However, an anonymous group of nine B-type and two possible FG supergiant stars are detected as possible companions to GT Car, despite its location at a seemingly improbably large distance of 10 kpc. WZ Sgr is found to lie in a sparse, previously undetected cluster, 1.8 kpc distant, containing upward of 76 potential early-type member stars. Preliminary spectroscopic observations strengthen the case for cluster membership in this instance. SW Vel appears to belong to an older subgroup of the 2.5 kpc distant Vel OB5 association described by Turner (1979), with 28 B star candidates in its immediate vicinity. Derived space reddenings and luminosities for WZ Sgr and SW Vel are consistent with their group membership, and the parameters of their associated stars, as well as those for the potential companions of GT Car, indicate that they are of comparable age to their associated Cepheid. Information is provided for follow-up studies of these stellar groups. Subject headings: Cepheids-open clusters and associations: general

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An empirical H-gamma luminosity calibration for class V-III stars

Cited by 29 publications

References 0 publications

Pre-main-sequence stars in the star-forming complex Sh 2-284

Pre-main-sequence stars in the star-forming complex Sh 2-284

Rotational Feature of Vega Revealed from Spectral Line Profiles

A search for OB associates near southern long-period Cepheids. IV - XY Carinae, GT Carinae, WZ Sagittarii, and SW Velorum

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