Multiwavelength observations of NaSt1 (WR 122)

Equatorial mass loss and X-rays from an interacting Wolf-Rayet binary

Jon Mauerhan, Nathan Smith, Schuyler D. Van Dyk, Katie M. Morzinski, Laird M Close, Philip M Hinz, Jared R. Males, Timothy J. Rodigas

Research output: Contribution to journalArticle

6 Citations (Scopus)

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 [NII] 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<sup>-1</sup>) 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 MagellanAOhas resolved a compact ellipsoid of K<inf>s</inf>-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.

Original languageEnglish (US)
Pages (from-to)2551-2563
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume450
Issue number3
DOIs
StatePublished - 2015

Fingerprint

wolves
nebulae
x rays
Wolf-Rayet stars
ellipsoids
velocity structure
point source
mass transfer
automobile
near infrared
outflow
observatory
spectroscopy
geometry
loss
adaptive optics
Hubble Space Telescope
gas
lobes
radial velocity

Keywords

  • Stars: emission-line, Be
  • Stars: individual: NaSt1
  • Stars: mass loss
  • Stars: peculiar
  • Stars: Wolf-Rayet

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Multiwavelength observations of NaSt1 (WR 122) : Equatorial mass loss and X-rays from an interacting Wolf-Rayet binary. / Mauerhan, Jon; Smith, Nathan; Van Dyk, Schuyler D.; Morzinski, Katie M.; Close, Laird M; Hinz, Philip M; Males, Jared R.; Rodigas, Timothy J.

In: Monthly Notices of the Royal Astronomical Society, Vol. 450, No. 3, 2015, p. 2551-2563.

Research output: Contribution to journalArticle

Mauerhan, Jon ; Smith, Nathan ; Van Dyk, Schuyler D. ; Morzinski, Katie M. ; Close, Laird M ; Hinz, Philip M ; Males, Jared R. ; Rodigas, Timothy J. / Multiwavelength observations of NaSt1 (WR 122) : Equatorial mass loss and X-rays from an interacting Wolf-Rayet binary. In: Monthly Notices of the Royal Astronomical Society. 2015 ; Vol. 450, No. 3. pp. 2551-2563.
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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 [NII] 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 MagellanAOhas resolved a compact ellipsoid of Ks-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.",
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AU - Morzinski, Katie M.

AU - Close, Laird M

AU - Hinz, Philip M

AU - Males, Jared R.

AU - Rodigas, Timothy J.

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AB - 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 [NII] 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 MagellanAOhas resolved a compact ellipsoid of Ks-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.

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KW - Stars: mass loss

KW - Stars: peculiar

KW - Stars: Wolf-Rayet

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