Fundamental Parameters for Central Stars of 103 Infrared Bowshock Nebulae

TL;DR

This study characterizes the central stars of 103 infrared bowshock nebulae, providing detailed stellar parameters and insights into their rotation, binarity, and runaway status, which are crucial for understanding stellar evolution and mass-loss processes.

Contribution

It offers the first comprehensive analysis of stellar parameters for bowshock stars, including spectra, rotation, binarity, and runaway fractions, aiding in mass-loss rate determinations for OB stars.

Findings

Most bowshock stars are OB type with specific temperature and gravity ranges.

60% of the stars are binaries, consistent with other OB star populations.

23% are runaways, with a high binary fraction among them, suggesting dynamical ejection as a primary origin.

Abstract

Stellar bowshock nebulae are arcuate shock fronts formed by the interaction of radiation-driven stellar winds and the relative motion of the ambient interstellar material. Stellar bowshock nebulae provide a promising means to measure wind-driven mass loss, independent of other established methods. In this work, we characterize the stellar sources at the center of bowshock nebulae drawn from all-sky catalogs of 24 $\mu$m-selected nebulae. We obtain new, low-resolution blue optical spectra for \numstars~stars and measure stellar parameters temperature \teff, surface gravity \logg, and projected rotational broadening \vsini. We perform additional photometric analysis to measure stellar radius \rstar, luminosity \lstar, and visual-band extinction $A_V$. All but one of our targets are O and early B stars, with temperatures ranging from $T$=16.5--46.8~k\kelvin, gravities $\log g=$2.57--4.60, and \vsini~from $<$100--400~\kms. With the exception of rapid rotator $\zeta$ Oph, bowshock stars do not rotate at or near critical velocities. At least 60 of 103 (60\%) OB bowshock stars are binaries, consistent with the multiplicity fraction of other OB samples. The sample shows a runaway fraction of 23\%, with \numrunaway~stars having $v_{\text{2D}}\geq25$~\kms. Of the 19 runaways, at least 15 ($\geq$79\%) are binaries, favoring dynamical ejection over the binary supernova channel for producing runaways. We provide a comprehensive census of stellar parameters for bowshock stars, useful as a foundation for determining the mass-loss rates for OB-type stars -- one of the single most critical factors in stellar evolution governing the production of neutron stars and black holes.