Photometric, Polarization, and Spectrographic Observations of O and B Stars.

Hiltner, W. A.

doi:10.1086/190029

Cited by 341 publications

(197 citation statements)

References 1 publication

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“…One of the targets is HD 46223, the hottest member of NGC 2244. Situated at about 1.4-1.7 kpc (Hensberge et al 2000), this star was previously A&A 533, A4 (2011) quoted in the literature as having a spectral type O5 V (Hiltner 1956;Bisiacchi et al 1982), O5 ((f)) (Conti & Leep 1974), O4 ((f)) (Massey et al 1995) and O4 V((f + )) (Mahy et al 2009). The nine-year spectroscopic campaign by Mahy et al to investigate multiplicity did not reveal any significant variation of the radial velocity related to the presence of a companion.…”

Section: Introductionmentioning

confidence: 72%

Variability in the CoRoT photometry of three hot O-type stars

Blomme

Mahy

Catala

et al. 2011

A&A

108

121

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Context. The detection of pulsational frequencies in stellar photometry is required as input for asteroseismological modelling. The second short run (SRa02) of the CoRoT mission has provided photometric data of unprecedented quality and time-coverage for a number of O-type stars. Aims. We analyse the CoRoT data corresponding to three hot O-type stars, describing the properties of their light curves and search for pulsational frequencies, which we then compare to theoretical model predictions. Methods. We determine the amplitude spectrum of the data, using the Lomb-Scargle and a multifrequency HMM-like technique. Frequencies are extracted by prewhitening, and their significance is evaluated under the assumption that the light curve is dominated by red noise. We search for harmonics, linear combinations, and regular spacings among these frequencies. We use simulations with the same time sampling as the data as a powerful tool to judge the significance of our results. From the theoretical point of view, we use the MAD non-adiabatic pulsation code to determine the expected frequencies of excited modes. Results. A substantial number of frequencies is listed, but none can be convincingly identified as being connected to pulsations. The amplitude spectrum is dominated by red noise. Theoretical modelling shows that all three O-type stars can have excited modes, but the relation between the theoretical frequencies and the observed spectrum is not obvious. Conclusions. The dominant red noise component in the hot O-type stars studied here clearly points to a different origin than the pulsations seen in cooler O stars. The physical cause of this red noise is unclear, but we speculate on the possibility of sub-surface convection, granulation, or stellar wind inhomogeneities being responsible.

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Section: Introductionmentioning

confidence: 72%

Variability in the CoRoT photometry of three hot O-type stars

Blomme

Mahy

Catala

et al. 2011

A&A

108

121

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“…The only previous measurement of polarization for the object, obtained by Hiltner (1956) 30 years ago, shows po-…”

Section: Hilt 641 (Hd 64315)mentioning

confidence: 99%

Polarimetry of southern peculiar early–type stars

Yudin

Evans

1998

Astron. Astrophys. Suppl. Ser.

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Abstract. We present and discuss optical polarimetry of a large group (60 objects) of peculiar early-type stars (Herbig Ae/Be stars and candidate members, B[e] stars, extreme emission line objects etc.). Most were taken from "A new catalogue of members and candidate members of Herbig Ae/Be stellar group" The et al. (1994). For 40 out of the 60 objects polarization was measured for the first time. On the basis of the data we draw conclusions about the circumstellar shell configuration and orientation for several objects. Polarimetric variability on different timescales (minutes . . . hours . . . days) was investigated, as well as comparison with earlier measurements to investigate variability over longer time-scales. No circular polarization was detected to a 5σ level in most of the investigated stars. Polarimetric data obtained here as well as data available from the literature were analyzed from the point of investigating the evolutionary status of the objects. The relationship between the polarimetric and photometric data was also investigated.

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“…There have been several estimates of the distance to Cygnus OB7: Hiltner (1956) and Schmidt (1958) derived a distance of 740 pc. A similar value was suggested by de Zeeuw et al (1999) using data from the Hipparcos Catalogue (although Appendices are available in electronic form at http://www.aanda.org their results were inconclusive due to the fact that there is a giant molecular cloud complex (e.g.…”

Section: Introductionmentioning

confidence: 99%

A wide-field near-infrared H₂2.122μm line survey of the Braid Nebula star formation region in Cygnus OB7

Khanzadyan

Davis

Aspin

et al. 2012

A&A

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Context. Outflows and jets are the first signposts of ongoing star formation processes in any molecular cloud, yet their study in optical bands provides limited results due to the large extinction present. Near-infrared unbiased wide-field observations in the H 2 1−0 S(1) line at 2.122 µm alleviates the problem, enabling us to detect more outflows and trace them closer to their driving sources. Aims. As part of a large-scale multi-waveband study of ongoing star formation in the Braid Nebula star formation region, we focus on a one square degree region that includes Lynds Dark Nebula 1003 and 1004. Our goal is to find all of the near-infrared outflows, uncover their driving sources and estimate their evolutionary phase. Methods. We use near-infrared wide-field observations obtained with WFCAM on UKIRT, in conjunction with previously-published optical and archival MM data, to search for outflows and identify their driving sources; we subsequently use colour−colour analysis to determine the evolutionary phase of each source. Results. Within a one square degree field we have identified 37 complex MHOs, most of which are new. After combining our findings with other wide-field, multi-waveband observations of the same region we were able to discern 28 outflows and at least 18 protostars. Our analysis suggests that these protostars are younger and/or more energetic than those of the Taurus-Auriga region. The outflow data enable us to suggest connection between outflow ejection and repetitive FU Ori outburst events. We also find that star formation progresses from W to E across the investigated region.

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Photometric, Polarization, and Spectrographic Observations of O and B Stars.

Cited by 341 publications

References 1 publication

Variability in the CoRoT photometry of three hot O-type stars

Variability in the CoRoT photometry of three hot O-type stars

Polarimetry of southern peculiar early–type stars

A wide-field near-infrared H₂2.122μm line survey of the Braid Nebula star formation region in Cygnus OB7

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Photometric, Polarization, and Spectrographic Observations of O and B Stars.

Cited by 341 publications

References 1 publication

Variability in the CoRoT photometry of three hot O-type stars

Variability in the CoRoT photometry of three hot O-type stars

Polarimetry of southern peculiar early–type stars

A wide-field near-infrared H22.122μm line survey of the Braid Nebula star formation region in Cygnus OB7

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A wide-field near-infrared H₂2.122μm line survey of the Braid Nebula star formation region in Cygnus OB7