Stagnant Shells in the Vicinity of the Dusty Wolf─Rayet─OB Binary WR 112

DOI: 
10.3847/2041-8213/835/2/L31
Publication date: 
01/02/2017
Main author: 
Lau, R. M.
IAA authors: 
Schödel, R.
Authors: 
Lau, R. M.;Hankins, M. J.;Schödel, R.;Sanchez-Bermudez, J.;Moffat, A. F. J.;Ressler, M. E.
Journal: 
The Astrophysical Journal
Refereed: 
Yes
Publication type: 
Article
Volume: 
835
Pages: 
L31
Abstract: 

We present high spatial resolution mid-infrared images of the nebula around the late-type carbon-rich Wolf─Rayet (WC)─OB binary system WR 112 taken by the recently upgraded VLT spectrometer and imager for the mid-infrared (VISIR) with the PAH1, Ne ii_2, and Q3 filters. The observations reveal a morphology resembling a series of arc-like filaments and broken shells. Dust temperatures and masses are derived for each of the identified filamentary structures, which exhibit temperatures ranging from {179}<SUB>-6</SUB><SUP>+8</SUP> K at the exterior W2 filament to {355}<SUB>-25</SUB><SUP>+37</SUP> K in the central 3″. The total dust mass summed over the features is 2.6 ± 0.4 × 10<SUP>−5</SUP> M<SUB>☉</SUB>. A multi-epoch analysis of mid-IR photometry of WR 112 over the past ∼20 years reveals no significant variability in the observed dust temperature and mass. The morphology of the mid-IR dust emission from WR 112 also exhibits no significant expansion from imaging data taken in 2001, 2007, and 2016, which disputes the current interpretation of the nebula as a high expansion velocity (∼1200 km s<SUP>−1</SUP>) “pinwheel”-shaped outflow driven by the central WC─OB colliding-wind binary. An upper limit of ≲120 km s<SUP>−1</SUP> is derived for the expansion velocity assuming a distance of 4.15 kpc. The upper limit on the average total mass-loss rate from the central 3″ of WR 112 is estimated to be ≲8 × 10<SUP>−6</SUP> M<SUB>☉</SUB> year<SUP>−1</SUP>. We leave its true nature as an open question, but propose that the WR 112 nebula may have formed in the outflow during a previous red or yellow supergiant phase of the central Wolf─Rayet star.

Database: 
ADS
SCOPUS
URL: 
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85011973240&doi=10.3847%2f2041-8213%2f835%2f2%2fL31&partnerID=40&md5=b5b36e0933ced0bccbbdaef9cd34a4e3
ADS Bibcode: 
2017ApJ...835L..31L
Keywords: 
infrared: stars;stars: individual: WR 112;stars: winds;outflows;stars: Wolf─Rayet;Astrophysics - Solar and Stellar Astrophysics;Astrophysics - Astrophysics of Galaxies