The young stellar population of IC 1613. III. New O-type stars unveiled by GTC-OSIRIS

Abstract

Recent findings hint that the winds of massive stars with poorer metallicity than the SMC may be stronger than predicted by theory. Besides calling the paradigm of radiation driven winds into question, this result would impact the predicted evolutionary paths of massive stars, their calculated ionizing radiation and mechanical feedback and the role these objects play at different stages of the Universe. The field needs a systematic study of the winds of a large set of very metal poor massive stars, but the sampling of spectral types is particularly poor in the very early types. This paper's goal is to increase the list of known O-type stars in the dwarf irregular galaxy IC1613, whose metallicity is smaller than the SMC's by roughly a factor 2. Using the reddening-free Q-parameter, evolutionary masses and GALEX photometry, we built a list of very likely O-type stars. We obtained low-resolution R~1000 GTC-OSIRIS spectra for a fraction of them and performed spectral classification, the only way to unequivocally confirm candidate OB-stars. We have discovered 8 new O-type stars in IC1613, increasing the list of 7 known O-type stars in this galaxy by a factor of 2. The best quality spectra were analyzed with the model atmosphere code FASTWIND to derive stellar parameters. We present the first spectral type -- effective temperature scale for O-stars beyond the SMC. The derived effective temperature calibration for IC1613 is about 1000K hotter than the scale at the SMC. The analysis of an increased list of O-type stars will be crucial for the studies of the winds and feedback of massive stars at all ages of the Universe.

A&A accepted. 13 pages, including appendix. 15 figures total

References in corpus (13)

• Measured Metallicities at the Sites of Nearby Broad-Lined Type Ic Supernovae and Implications for the SN-GRB Connection
• The empirical metallicity dependence of the mass-loss rate of O- and early B-type stars
• The VLT-FLAMES survey of massive stars: Evolution of surface N abundances and effective temperature scales in the Galaxy and Magellanic Clouds
• The different progenitors of type Ib, Ic SNe, and of GRB
• VLT spectroscopy of blue supergiants in IC 1613
• The Physical Properties and Effective Temperature Scale of O-type Stars as a Function of Metallicity. III. More Results from the Magellanic Clouds
• The IACOB project: A grid-based automatic tool for the quantitative spectroscopic analysis of O-stars
• On the Mass-Loss Rates of Massive Stars in the Low-Metallicity Galaxies IC 1613, WLM and NGC 3109
• The Araucaria Project: VLT-spectroscopy of blue massive stars in NGC 55
• Discovery of a massive variable star with Z=Zo/36 in the galaxy DDO 68
• VLT/X-shooter observations of the low-metallicity blue compact dwarf galaxy PHL 293B including a luminous blue variable star
• A peculiar Of star in the Local Group galaxy IC 1613
• O-star mass-loss rates at low metallicity

Cited by in corpus (16)

• Winds of low-metallicity OB-type stars: HST-COS spectroscopy in IC1613
• The properties of ten O-type stars in the low-metallicity galaxies IC 1613, WLM and NGC 3109
• Massive Stars in the Galaxies of the Local Group
• The IACOB project: II. On the scatter of O-dwarf spectral type -- effective temperature calibrations
• First stellar spectroscopy in Leo P
• The Shortest-period Wolf-Rayet binary in the Small Magellanic Cloud: Part of a high-order multiple system
• OB stars at the lowest Local Group metallicity: GTC-OSIRIS observations of Sextans A
• A machine-learning photometric classifier for massive stars in nearby galaxies I. The method
• A new reference catalogue for the very metal-poor Universe: +150 OB stars in Sextans A
• Spectroscopic evolution of massive stars near the main sequence at low metallicity
• A Panchromatic Study of Massive Stars in the Extremely Metal-Poor Local Group Dwarf Galaxy Leo A
• Massive stars in the Sagittarius Dwarf Irregular Galaxy
• A near-UV reconnaissance of metal-poor massive stars
• The wind properties of O-type stars at sub-SMC metallicity
• A machine-learning photometric classifier for massive stars in nearby galaxies II. The catalog
• The Treasury of Extremely Metal-Poor O Stars