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Multiwavelength observations of NaSt1 (WR 122): equatorial mass loss and X-rays from an interacting Wolf–Rayet binary

Mauerhan, Jon and Smith, Nathan and Van Dyk, Schuyler D. and Morzinski, Katie M. and Close, Laird M. and Hinz, Philip M. and Males, Jared R. and Rodigas, Timothy J. (2015) Multiwavelength observations of NaSt1 (WR 122): equatorial mass loss and X-rays from an interacting Wolf–Rayet binary. Monthly Notices of the Royal Astronomical Society, 450 (3). pp. 2551-2563. ISSN 0035-8711. https://resolver.caltech.edu/CaltechAUTHORS:20150709-092638418

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Abstract

NaSt1 (aka Wolf–Rayet 122) is a peculiar emission-line star embedded in an extended nebula of [N ii] emission with a compact dusty core. The object was previously characterized as a Wolf–Rayet (WR) star cloaked in an opaque nebula of CNO-processed material, perhaps analogous to η Car and its Homunculus nebula, albeit with a hotter central source. To discern the morphology of the [N ii] nebula we performed narrow-band imaging using the Hubble Space Telescope and Wide-field Camera 3. The images reveal that the nebula has a disc-like geometry tilted ≈12° from edge-on, composed of a bright central ellipsoid surrounded by a larger clumpy ring. Ground-based spectroscopy reveals radial velocity structure (±10 km s^−1) near the outer portions of the nebula's major axis, which is likely to be the imprint of outflowing gas. Near-infrared adaptive-optics imaging with Magellan AO has resolved a compact ellipsoid of K s-band emission aligned with the larger [N ii] nebula, which we suspect is the result of scattered He i line emission (λ2.06 μm). Observations with the Chandra X-ray Observatory have revealed an X-ray point source at the core of the nebula that is heavily absorbed at energies <1 keV and has properties consistent with WR stars and colliding-wind binaries. We suggest that NaSt1 is a WR binary embedded in an equatorial outflow that formed as the result of non-conservative mass transfer. NaSt1 thus appears to be a rare and important example of a stripped-envelope WR forming through binary interaction, caught in the brief Roche lobe overflow phase.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1093/mnras/stv257DOIArticle
http://arxiv.org/abs/1502.01794arXivDiscussion Paper
ORCID:
AuthorORCID
Van Dyk, Schuyler D.0000-0001-9038-9950
Close, Laird M.0000-0002-2167-8246
Hinz, Philip M.0000-0002-1954-4564
Additional Information:© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 February 5; received 2015 February 4; in original form 2015 January 6. First published online May 20, 2015. We thank the anonymous referee for an insightful review of this manuscript. The scientific results reported in this article are based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programme HST-GO-13034. Support for programme HST-GO-13034 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. The scientific results reported in this article are based on observations made by the Chandra X-ray Observatory. Support for this work was provided by the National Aeronautics and Space Administration through Chandra Award Number GO4-15003X issued by the Chandra X-ray Observatory Centre, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060. This research has made use of data obtained from the Chandra Data Archive and the Chandra Source Catalogue, and software provided by the Chandra X-ray Centre (CXC) in the application packages CIAO, CHIPS, and SHERPA. NS received partial support from NSF grant AST-1312221. Some observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. This work was performed in part under contract with the California Institute of Technology (Caltech) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. The results presented here were also based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 075.B-0547(C). This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration.
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
NASANAS 5-26555
NASAHST-GO-13034
NASAGO4-15003X
NASANAS8-03060
NSFAST-1312221
NASA Sagan FellowshipUNSPECIFIED
NASA/JPL/CaltechUNSPECIFIED
Subject Keywords:stars: emission-line; Be; stars: individual: NaSt1; stars: mass loss; stars: peculiar; stars: Wolf-Rayet
Issue or Number:3
Record Number:CaltechAUTHORS:20150709-092638418
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150709-092638418
Official Citation:Mauerhan, J., Smith, N., Van Dyk, S. D., Morzinski, K. M., Close, L. M., Hinz, P. M., . . . Rodigas, T. J. (2015). Multiwavelength observations of NaSt1 (WR 122): equatorial mass loss and X-rays from an interacting Wolf–Rayet binary. Monthly Notices of the Royal Astronomical Society, 450(3), 2551-2563. doi: 10.1093/mnras/stv257
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58819
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:09 Jul 2015 21:19
Last Modified:07 Apr 2020 19:01

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