Warner and Swasey Observatory

Nassau, J. J.

doi:10.1086/107786

Cited by 10 publications

(12 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The star has been classified as a F5 supergiant by Nassau et al (1965). More recently Hrivnak et al (1989) published a medium resolution optical spectrum and determined the spectral type to be F0-5I, consistent with the previous spectral classification.…”

Section: Stellar Parameterssupporting

confidence: 68%

The circumstellar envelope of the C-rich post-AGB star HD 56126

Hony

Tielens

Waters

et al. 2003

A&A

View full text Add to dashboard Cite

Abstract. We present a detailed study of the circumstellar envelope of the post-asymptotic giant branch "21 µm object" HD 56126. We build a detailed dust radiative transfer model of the circumstellar envelope in order to derive the dust composition and mass, and the mass-loss history of the star. To model the emission of the dust we use amorphous carbon, hydrogenated amorphous carbon, magnesium sulfide and titanium carbide. We present a detailed parametrisation of the optical properties of hydrogenated amorphous carbon as a function of H/C content. The mid-infrared imaging and spectroscopy is best reproduced by a single dust shell from 1.2 to 2.6 radius around the central star. This shell originates from a short period during which the mass-loss rate exceeded 10 −4 M /yr. We find that the strength of the "21" µm feature poses a problem for the TiC identification. The low abundance of Ti requires very high absorption cross-sections in the ultraviolet and visible wavelength range to explain the strength of the feature. Other nano-crystalline metal carbides should be considered as well. We find that hydrogenated amorphous carbon in radiative equilibrium with the local radiation field does not reach a high enough temperature to explain the strength of the 3.3-3.4 and 6-9 µm hydrocarbon features relative to the 11-17 µm hydrocarbon features. We propose that the carriers of these hydrocarbon features are not in radiative equilibrium but are transiently heated to high temperature. We find that 2 per cent of the dust mass is required to explain the strength of the "30" µm feature, which fits well within the measured atmospheric abundance of Mg and S. This further strengthens the MgS identification of the "30" µm feature.Key words. stars: individual: HD 56126 -stars: AGB and post-AGB -stars: carbon -circumstellar matterstars: mass-loss -infrared: stars IntroductionPost-asymptotic giant branch stars (post-AGBs) are objects in which the strong AGB mass-loss has ceased while the remaining star is not (yet) hot enough to ionise the surrounding material. These objects are characterised by a double-peaked spectral energy distribution (SED). In the ultraviolet (UV) and visible range the central star is visible. In the mid-infrared (IR) range the light is dominated by emission from the dusty circumstellar envelope (CSE). Post-AGB stars are the prime objects to study stellar evolution near the very end of the AGB because they are the most recent evolutionary descendants of the AGB stars. Mass loss near the tip of the AGB is not well understood. There are indications that the mass-loss rates near the end of the AGB exceed the values predicted by Send offprint requests to: S. Hony, e-mail: shony@rssd.esa.int Based on observations taken at the European Southern Observatory, La Silla, Chile and observation obtained with ISO, an ESA project with instruments funded by ESA Member states (especially the PI countries: France, Germany, The Netherlands and the UK) with the participation of ISAS and NASA. the existing dust driven wind models...

show abstract

Section: Stellar Parameterssupporting

confidence: 68%

The circumstellar envelope of the C-rich post-AGB star HD 56126

Hony

Tielens

Waters

et al. 2003

A&A

View full text Add to dashboard Cite

show abstract

“…The star in question was probably first mentioned and named in 1965 during the completion of the Luminous Stars in the Northern Milky Way catalogue (Nassau et al 1965;Hardorp et al 1965). The star was designated as LS VI -04 19, which reads: Luminous Stars, volume six, declination zone -04, star number 19.…”

Section: What We Know About the Star Als 9243mentioning

confidence: 99%

A surprise in the updated list of stellar perturbers of long-period comet motion

Wysoczańska

Dybczyński

Polińska

2020

A&A

View full text Add to dashboard Cite

Context. The second Gaia data release (Gaia DR2) provided us with the precise five-parameter astrometry for 1.3 billion of sources. As stars passing close to the Solar System are thought to influence the dynamical history of long-period comets, we update and extend the list of stars that could potentially perturb the motion of these comets. Aims. We announce a publicly available database containing an up-to-date list of stars and stellar systems potentially perturbing the motion of long-period comets. We add new objects and revise previously published lists. Special emphasis is placed on stellar systems. A discussion of mass estimation is included. Methods. Using the astrometry, preferably from Gaia DR2, augmented with data from other sources, we calculate nominal spatial positions and velocities for each star. To filter studied objects on the basis of their nominal minimum heliocentric distances we numerically integrate the motion of stars under the Galactic potential and their mutual interactions. Results. We announce the updated list of stellar perturbers of cometary motion, including the masses of perturbers along with the publicly available database interface. These data are ready to be used with the observed long-period comets orbits to study an individual influence of a whole sample of perturbers, or specific stars, on a dynamical past or future of a specific comet. New potential perturbers were added; there are 138 more than in the previously published sources. Conclusions. We demonstrate that a new set of prospective perturbers is an important tool in studies of cometary dynamics. The use of our data changes the results of the past and future cometary motion analysis. We point out a puzzling object in our list, star ALS 9243. The Gaia DR2 astrometry suggests a very close encounter of this star with the Sun; however, its astrophysical parameters result in a completely different current distance of ALS 9243 and its high mass.

show abstract

“…NaSt1, aka WR 122, is an evolved massive star that has defied characterization. It was discovered by Nassau & Stephenson (1963), who proposed a WR classification based on the strong emission-line spectrum. It was later reclassified as a late nitrogen-type WR (WN type) based on nitrogen emission-line ratios in the optical spectrum (Massey & Conti 1983), then later proposed to be a B [e], O[e], or Ofpe/WN9 star based on its optical-IR spectral properties (van der Hucht 1997).…”

Section: Introductionmentioning

confidence: 99%

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

Mauerhan

Smith

Dyk

et al. 2015

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

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. This object was characterized by Crowther & Smith (1999) 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 narrowband imaging using the Hubble Space Telescope and Wide-field Camera 3. The images reveal that the nebula has a disk-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.

show abstract

Warner and Swasey Observatory

Cited by 10 publications

References 0 publications

The circumstellar envelope of the C-rich post-AGB star HD 56126

The circumstellar envelope of the C-rich post-AGB star HD 56126

A surprise in the updated list of stellar perturbers of long-period comet motion

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

Contact Info

Product

Resources

About