SWIFT/UVOT PHOTOMETRY OF THE PLANETARY NEBULA WeBo 1: UNMASKING A FAINT HOT COMPANION STAR

Journal Article · Wed Aug 15 04:00:00 EDT 2012 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/144/2/65· OSTI ID:22034372

Siegel, Michael H; Hoversten, Erik; Stark, Michele ^[1]; Bond, Howard E ^[2]

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1. Pennsylvania State University, Department of Astronomy, 525 Davey Laboratory, University Park, PA 16802 (United States)
2. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

We present an analysis of over 150 ks of data on the planetary nebula WeBo 1 (PN G135.6+01.0) obtained with the Swift Ultraviolet Optical Telescope (UVOT). The central object of this nebula has previously been described as a late-type K giant barium star with a possible hot companion, most likely a young pre-white dwarf. UVOT photometry shows that while the optical photometry is consistent with a large cool object, the near-ultraviolet (NUV) photometry shows far more UV flux than could be produced by any late-type object. Using model stellar atmospheres and a comparison to UVOT photometry for the pre-white dwarf PG 1159-035, we find that the companion has a temperature of at least 40,000 K and a radius of, at most, 0.056 R{sub Sun }. While the temperature and radius are consistent with a hot compact stellar remnant, they are lower and larger, respectively, than expected for a typical young pre-white dwarf. This likely indicates a deficiency in the assumed UV extinction curve. We find that higher temperatures more consistent with expectations for a pre-white dwarf can be derived if the foreground dust has a strong 'blue bump' at 2175 A and a lower R{sub V}. Our results demonstrate the ability of Swift to both uncover and characterize hot hidden companion stars and to constrain the UV extinction properties of foreground dust based solely on UVOT photometry.

• OSTI ID: 22034372
• Journal Information: Astronomical Journal (New York, N.Y. Online), Journal Name: Astronomical Journal (New York, N.Y. Online) Journal Issue: 2 Vol. 144; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTRONOMY
ASTROPHYSICS
BARIUM
COMPARATIVE EVALUATIONS
COSMIC DUST
DIAGRAMS
GIANT STARS
PHOTOMETRY
PLANETARY NEBULAE
STELLAR ATMOSPHERES
TELESCOPES
ULTRAVIOLET RADIATION
WHITE DWARF STARS