First results of an H-alpha based search of classical Be stars in the Perseus Arm and beyond

Abstract

We investigate a region of the Galactic plane, between 120 <= l <= 140 and -1 <= b <= +4, and uncover a population of moderately reddened (E(B-V) \sim 1) classical Be stars within and beyond the Perseus and Outer Arms. 370 candidate emission line stars (13 <= r <= 16) selected from the INT Photometric H-alpha Survey of the Northern Galactic plane (IPHAS) have been followed up spectroscopically. A subset of these, 67 stars with properties consistent with those of classical Be stars, have been observed at sufficient spectral resolution (Delta_lambda \sim 2 - 4 Angstrom) at blue wavelengths to narrow down their spectral types. We determine these to a precision estimated to be +/- 1 sub-type and then we measure reddenings via SED fitting with reference to appropriate model atmospheres. Corrections for contribution to colour excess from circumstellar discs are made using an established scaling to H-alpha emission equivalent width. Spectroscopic parallaxes are obtained after luminosity class has been constrained via estimates of distances to neighbouring A/F stars with similar reddenings. Overwhelmingly, the stars in the sample are confirmed as luminous classical Be stars at heliocentric distances ranging from 2 kpc up to \sim 12 kpc. However, the errors are presently too large to enable the cumulative distribution function with respect to distance to distinguish between models placing the stars exclusively in spiral arms, or in a smooth exponentially-declining distribution.

21 pages, 13 figures. Accepted for publication in MNRAS

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Cited by in corpus (14)

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• The Second Data Release of the INT Photometric H-Alpha Survey of the Northern Galactic Plane (IPHAS DR2)
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• Disk Detective: Discovery of New Circumstellar Disk Candidates through Citizen Science
• A deep catalogue of classical Be stars in the direction of the Perseus Arm: spectral types and interstellar reddenings
• Physical parameters of IPHAS-selected classical Be stars. (I. Determination procedure and evaluation of the results.)
• Identification of new Classical Ae stars in the Galaxy using LAMOST DR5
• Discovery of 2716 hot emission-line stars from LAMOST DR5
• Discovery of a new classical nova shell around a nova-like cataclysmic variable
• The Gaia/IPHAS and Gaia/KIS Value-Added Catalogues
• Population-based identification of Hα-excess sources in the Gaia DR2 and IPHAS catalogues
• Study of a Sample of Faint Be Stars in the Exofield of CoRoT. Part III. Global Spectroscopic Characterization and Astrophysical Parameters of the Central Stars
• tonalli: an asexual genetic code to characterise APOGEE-2 stellar spectra. I. Validation with synthetic and solar spectra
• MIRIS Paα Galactic Plane Survey. II. The Catalog of Paα Emission-line Sources