First VLT/X-shooter spectroscopy of early-type stars outside the Local Group

Details First VLT/X-shooter spectroscopy of early-type stars outside the Local Group First VLT/X-shooter spectroscopy of early-type stars outside the Local Group

2012-01-24

arxiv.org/abs/1201.5145v1

Astronomy and Astrophysics

Astrophysics

Solar and Stellar Astrophysics

12 pages, 10 figures, accepted for publication in Monthly Notices of the Royal Astronomical Society; the definitive version wi

Scientific paper

As part of the VLT/X-shooter science verification, we obtained the first optical medium-resolution spectrum of a previously identified bright O-type object in NGC55, an LMC-like galaxy at a distance of \sim2.0 Mpc. Based on the stellar and nebular spectrum, we investigate the nature and evolutionary status of the central object(s) and its influence on the surrounding interstellar medium. We conclude that the source, NGC55_C1_31, is a composite object, likely a stellar cluster, which contains one or several hot (T_eff \simeq 50000 K) WN stars with a high mass-loss rate (\sim3 \times 10^{-5} M_\odot yr^{-1}) and a helium-rich composition (N_He/N_H = 0.8). The visual flux is dominated by OB-type (super)giant stars with T_eff \sim< 35000 K, solar helium abundance (N_He/N_H = 0.1), and mass-loss rate \sim2 \times 10^{-6} M_\odot yr^{-1}. The surrounding H II region has an electron density n_e < 10^2 cm^{-3} and an electron temperature T(OIII) \simeq 11500 \pm 600 K. The oxygen abundance of this region is [O/H] = 8.18 \pm 0.03 which corresponds to Z = 0.31 \pm 0.04 Z_\odot. We observed no significant gradients in T(OIII), n_e or [O/H] on a scale of 73 pc extending in four directions from the ionising source. The properties of the HII region can be reproduced by a CLOUDY model which uses the central cluster as ionising source, thus providing a self-consistent interpretation of the data. We also report on the serendipitous discovery of HeII nebular emission associated with the nearby source NGC55_C2_35, a feature usually associated with strong X-ray sources.

Affiliated with

Also associated with

No associations

Rating

First VLT/X-shooter spectroscopy of early-type stars outside the Local Group does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with First VLT/X-shooter spectroscopy of early-type stars outside the Local Group, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and First VLT/X-shooter spectroscopy of early-type stars outside the Local Group will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-682713