RE 0044+09: A new K dwarf rapid rotator with a white dwarf companion?

Kellett, Barry J.; Bromage, Gordon E.; Brown, Alexander; Jeffries, Robin D.; James, David J.; Kilkenny, David; Robb, Russell M.; Wonnacott, David; Lloyd, Christopher; Clayton, C.

Abstract

We report the discovery of a new K dwarf rapid rotator with a potential white dwarf companion. The white dwarf accounts for over 90% of the observed extreme ultraviolet flux detected from this system. Analysis of ROSAT Wide Field Camera (WFC) and IUE data both suggest a white dwarf temperature of approximately 28,700 K. Optical photometry and the IUE long wavelength prime (LWP) spectrum (with the white dwarf contribution removed) imply that the late-type star has a spectral type of K1-3 V, and a distance of 55 +/- 5 pc. Using this distance, the observed IUE SWP flux, and the best-fit temperature results in a white dwarf radius of 0.0088 solar radius. The estimated white dwarf mass is then approximately 0.91 solar mass; somewhat over-massive compared to field white dwarfs. Optical photometry of the K star reveals a 'spot' modulation period of approximately 10 hr (now observed over 3 yr). However, radial velocity observations have revealed no significant variations. Spectroscopic observations place a low limit on the lithium abundance, but do show rapid rotation with a v sin i of 90 +/- 10 km/s. The K star was detected as a radio source at 3.6 cm (on two occasions) and 6 cm by the Very Large Array (VLA). The most likely evolutionary scenario is that the K star and hot white dwarf from either a wide binary or common proper motion pair with an age of 0.1-0.1 Gyr-consistent with the evolutionary timescale of the white dwarf and the rapid rotation of the K star. However, from the proper motion of the K star, this system does not seem to be associated with any of the known young stellar groups.

Citation

Kellett, B. J., Bromage, G. E., Brown, A., Jeffries, R. D., James, D. J., Kilkenny, D., …Clayton, C. (1995). RE 0044+09: A new K dwarf rapid rotator with a white dwarf companion?. Astrophysical Journal, 438, https://doi.org/10.1086/175080

• Journal Article Type: Article
• Publication Date: 1995-01
• Deposit Date: Feb 14, 2024
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 438
• DOI: https://doi.org/10.1086/175080
• Keywords: Companion Stars; Dwarf Stars; K Stars; Stellar Evolution; Stellar Rotation; White Dwarf Stars; Astronomical Photometry; Extreme Ultraviolet Radiation; Flux Density; Iue; Rosat Mission; Astrophysics; RADIO CONTINUUM: STARS; STARS: ACTIVITY; STARS: LATE-TYP
• Publisher URL: https://ui.adsabs.harvard.edu/abs/1995ApJ...438..364K/abstract