Abstract
Abstract We present wide-field multiwavelength observations of γ Cassiopeiae (or γ Cas for short) in order to study its feedback toward the interstellar environment. A large expanding cavity is discovered toward γ Cas in the neutral hydrogen (H i) images at a systemic velocity of about −10 km s−1. The measured dimension of the cavity is roughly 2.°0 × 1.°4 (or 6.0 pc × 4.2 pc at a distance of 168 pc), while the expansion velocity is ∼5.0 ± 0.5 km s−1. The CO observations reveal systematic velocity gradients in IC 63 (∼20 km s−1 pc−1) and IC 59 (∼30 km s−1 pc−1), two cometary globules illuminated by γ Cas, proving fast acceleration of the globules under stellar radiation pressure. The gas kinematics indicate that the cavity is opened by strong stellar wind, which has high potential to lead to the peculiar X-ray emission observed in γ Cas. Our result favors a new scenario that emphasizes the roles of stellar wind and binarity in the X-ray emission of the γ Cas stars.
Highlights
Γ Cas is the prototype of Be stars (Secchi 1866; Rivinius et al 2013) and is one of the most studied stars in the sky
The CO observations reveal systematic velocity gradients in IC 63 (∼ 20 km s−1 pc−1) and IC 59 (∼ 30 km s−1 pc−1), two cometary globules illuminated by γ Cas, proving fast acceleration of the globules under stellar radiation pressure
We present wide-field multi-wavelength images toward γ Cas, based on the observational data obtained from the neutral hydrogen (HI) 4π survey (HI4PI; see HI4PI Collaboration 2016) and the CO Galactic plane survey conducted with the Purple Mountain Observatory (PMO) 13.7 m millimeter-wavelength telescope
Summary
Γ Cas is the prototype of Be stars (Secchi 1866; Rivinius et al 2013) and is one of the most studied stars in the sky (see, e.g., Poeckert & Marlborough 1978; Henrichs et al 1983; Stee et al 1995; Smith & Robinson 1999) It is a bright B0.5 IVe star located at a distance of 168 ± 4 pc from the Sun (van Leeuwen 2007). Previous observations toward the interstellar environment of γ Cas focused on IC 63 and IC 59, two cometary globules brightened by γ Cas (e.g., Blouin et al 1997; Karr et al 2005), which are located to the northeast (IC 63) and north (IC 59) of γ Cas, respectively Both IC63 and IC59 are associated with S185 (see Sharpless 1959), which is a bright H II region with a shell to the northeast of γ Cas (see, e.g., Sun et al 2007). Complementary images from the full-sky Hα map (Finkbeiner 2003) and the all-sky survey by the Wide-field Infrared Survey Explorer (WISE; Wright et al 2010) are used for comparisons with the HI and CO line data
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
