2008/03/05 by Yaël Nazé, Y. Naze, N. R. Walborn +5
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1088/0004-6256/135/5/1946
published as AJ, 135, 1946-1957 (2008) · accepted by AJ; 15p, 15fig available in jpg
arxiv created 2008/03/05 · openalex publication_date 2008/04/11 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
Three Galactic O-type stars belong to the rare class of Of?p objects: HD 108, HD 191612, and HD 148937. The first two stars show a wealth of phenomena, including strong X-ray emission, light variability, and dramatic periodic spectral variability. We present here the first detailed optical and X-ray study of the third Galactic Of?p star, HD 148937. Spectroscopic monitoring has revealed low-level variability in the Balmer and He ii λ4686 lines, but constancy at He i and C iii λ4650. The Hα line exhibits profile variations at a possible periodicity of ∼7 days. Model atmosphere fits yield T eff = 41000 ± 2000 K, log( g ) = 4.0 ± 0.1, M ☉ yr −1 , and an overabundance of nitrogen by a factor of 4. At X-ray wavelengths, HD 148937 resembles HD 108 and HD 191612 in having a thermal spectrum dominated by a relatively cool component ( kT = 0.2 keV), broad lines (⩾1700 km s −1 ), and an order-of-magnitude overluminosity compared to normal O stars (log[ L unabs X / L BOL ] ∼ −6).