Bibcode
Drake, J. J.; Corradi, R. M. L.; Sabin, L.; Greimel, R.; Barlow, M. J.; Farnhill, H. J.; Sale, S. E.; Wright, N. J.; Steeghs, D.; Fabregat, J.; Drew, J. E.; Raddi, R.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 430, Issue 3, p.2169-2187
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4
2013
Citations
15
Refereed citations
13
Description
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) ˜ 1) classical Be
stars within and beyond the Perseus and Outer Arms. 370 candidate
emission-line stars (13 ≲ r ≲ 16) selected from the Isaac
Newton Telescope Photometric Hα Survey of the Northern Galactic
plane 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 (Δλ ≈
2-4 Å) at blue wavelengths to narrow down their spectral types. We
determine these to a precision estimated to be ±1 subtype and
then we measure reddenings via spectral energy distribution fitting with
reference to appropriate model atmospheres. Corrections for contribution
to colour excess from circumstellar discs are made using an established
scaling to Hα 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
˜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.
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