Supernova Remnant W49b and Its Environment

Abstract

We study Gamma-ray supernova remnant W49B and its environment using recent radio and infrared data. Spitzer IRS low resolution data of W49B shows shocked excitation lines of H 2 (0,0) S(0)-S(7) from the SNR-molecular cloud interaction. The H 2 gas is composed of two components with temperature of ∼260 K and ∼1060 K respectively. Various spectral lines from atomic and ionic particles are detected towards W49B. We suggest the ionic phase has an electron density of ∼500 cm −3 and a temperature of ∼10 4 K by the spectral line diagnoses. The mid-and farinfrared data from MSX, Spitzer and Herschel reveals a 151 ± 20 K hot dust component with a mass of 7.5 ± 6.6 × 10 −4 M ⊙ and a 45 ± 4 K warm dust component with a mass of 6.4 ± 3.2 M ⊙ . The hot dust is likely from materials swept up by the shock of W49B. The warm dust may possibly originate from the evaporation of clouds interacting with W49B. We build the HI absorption spectra of W49B and nearby four Hii regions (W49A, G42.90+0.58, G42.43-0.26 and G43.19-0.53), and study the relation between W49B and the surrounding molecular clouds by employing the 2.12 µm infrared and CO data. We therefore obtain a kinematic distance of ∼10 kpc for W49B and suggest that the remnant is likely associated with the CO cloud at about 40 km s −1 .

The Einstein@home Gamma-Ray Pulsar Survey. I. Search Methods, Sensitivity, and Discovery of New Young Gamma-Ray Pulsars

“…Placing W49B at the distance of 10 kpc obtained by Zhu et al (2014) suggests a gamma-ray luminosity of ∼ 2 × 10 36 erg s −1 . In order to provide a significant fraction of this emission, any gamma-ray pulsar would have to have a very large spin-down power, since the efficiency of converting spin-down power into gammaray luminosity tends to be lower for energetic pulsars (Abdo et al 2013).…”

The supernova remnant W49B as seen with H.E.S.S. and Fermi-LAT

“…For the three velocity ranges (1-15, 38-47 and 57-67 km/s at their kinematic distances of 11, 9.3 and 5 kpc respectively) examined by Zhu et al (2014) (see also Chen et al (2014)), and using the 13 CO "X-factor" of 4.92×10 20 (K km/s) −1 from Simon et al (2001), masses of 5 × 10 3 to 17 × 10 3 M with densities of 400 to 4 000 cm −3 were obtained. Allowing for a larger radius to the outer edge of the radio SNR features (0.05…”

“…One can note that Chen et al (2014) and Zhu et al (2014) have argued that the CO bubble in the 38-47 km/s range was blown out by the W49B progenitor star, suggesting a distance of about 10 kpc for the SNR. Additionally for this, and the 57-67 km/s ranges, the H 2 column densities (about 5 × 10 22 cm −2 ) inferred in this work are consistent with that derived from the X-ray spectral studies of Keohane et al (2007).…”

“…Moffett & Reynolds 1994) is assumed to come from the same shell region where a constant hydrogen density n H and magnetic field strength B are considered. Given the evidences that W49B interacts with the surrounding molecular clouds (e.g., Keohane et al 2007;Zhu et al 2014), we consider a scenario where the γ-ray emission comes from the shocked molecular clouds in the SNR shell. Note that the emitting region may originate from swept-up stellar wind and/or interstellar gas as discussed in Abdo et al (2010d).…”

“…Brogan & Troland (2001), using more recent VLA data, have shown that an association of W49B with the nearby star forming region W49A is also possible, extending the range of possible distances (8 ≤ D ≤ 12 kpc) for this source. More recently, Zhu et al (2014) obtained a distance of ∼10 kpc.…”