Query : 2011A&A...536L...1O

2011A&A...536L...1O - Astronomy and Astrophysics, volume 536, L1-1 (2011/12-1)

First firm spectral classification of an early-B pre-main-sequence star: B275 in M 17.


Abstract (from CDS):

The optical to near-infrared (300-2500nm) spectrum of the candidate massive young stellar object (YSO) B275, embedded in the star-forming region M 17, has been observed with X-shooter on the ESO Very Large Telescope. The spectrum includes both photospheric absorption lines and emission features (H and CaII triplet emission lines, 1st and 2nd overtone CO bandhead emission), as well as an infrared excess indicating the presence of a (flaring) circumstellar disk. The strongest emission lines are double-peaked with a peak separation ranging between 70 and 105km/s, and they provide information on the physical structure of the disk. The underlying photospheric spectrum is classified as B6-B7, which is significantly cooler than a previous estimate based on modeling of the spectral energy distribution. This discrepancy is solved by allowing for a larger stellar radius (i.e. a bloated star) and thus positioning the star above the main sequence. This constitutes the first firm spectral classification of an early-B pre-main-sequence (PMS) star. We discuss the position of B275 in the Hertzsprung-Russell diagram in terms of PMS evolution. Although the position is consistent with PMS tracks of heavily accreting protostars ({dot}(M)acc>10–5M/yr), the fact that the photosphere of the object is detectable suggests that the current mass-accretion rate is not very high.

Abstract Copyright:

Journal keyword(s): stars: formation - stars: pre-main-sequence - stars: massive - stars: variables: T Tauri, Herbig Ae/Be

Simbad objects: 5

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Number of rows : 5
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 CD-38 10980 WD* 16 23 33.8380498896 -39 13 46.161043572 9.916 10.885 11.029 10.936 10.841 DA2 476 0
2 GAL 015.03-00.67 Mas 18 20 22.3 -16 11 18           ~ 12 0
3 Cl* NGC 6618 B 275 * 18 20 25.17 -16 10 26.7     15.6     B2V 22 0
4 NGC 6618 OpC 18 20 47 -16 10.3           ~ 1589 0
5 HD 180699 Be* 19 18 10.9438132344 -18 51 49.695329124   6.95 6.97     B7IIIe 21 0

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