XMM-NEWTON OBSERVATIONS OF THE DWARF NOVA RU Peg IN QUIESCENCE: PROBE OF THE BOUNDARY LAYER
- Department of Physics, Middle East Technical University, Ankara (Turkey)
- Department of Astronomy and Astrophysics, Villanova University, Villanova, PA 19085 (United States)
- XMM-Newton Science Operations Centre, European Space Agency (ESA/ESAC), E-28691 Villanueva de la Canada, Madrid (Spain)
- Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249 (United States)
- United States Naval Observatory, Washington, DC 20392 (United States)
- Astronomy Department, University of Seattle, Seattle, WA 98195 (United States)
We present an analysis of X-ray and UV data obtained with the XMM-Newton Observatory of the long-period dwarf nova RU Peg. RU Peg contains a massive white dwarf (WD), possibly the hottest WD in a dwarf nova (DN), it has a low inclination, thus optimally exposing its X-ray emitting boundary layer (BL), and has an excellent trigonometric parallax distance. We modeled the X-ray data using XSPEC assuming a multi-temperature plasma emission model built from the MEKAL code (i.e., CEVMKL). We obtained a maximum temperature of 31.7 keV, based on the European Photon Imaging Camera MOS1, 2 and pn data, indicating that RU Peg has an X-ray spectrum harder than most DNe, except U Gem. This result is consistent with and indirectly confirms the large mass of the WD in RU Peg. The X-ray luminosity we computed corresponds to a BL luminosity for a mass accretion rate of 2 Multiplication-Sign 10{sup -11} M{sub sun} yr{sup -1} (assuming M{sub wd} = 1.3 M{sub sun}), in agreement with the expected quiescent accretion rate. The modeling of the O VIII emission line at 19 A as observed by the Reflection Grating Spectrometer implies a projected stellar rotational velocity v{sub rot}sin i = 695 km s{sup -1}, i.e., the line is emitted from material rotating at {approx}936-1245 km s{sup -1} (i {approx} 34 Degree-Sign -48 Degree-Sign) or about 1/6 of the Keplerian speed; this velocity is much larger than the rotation speed of the WD inferred from the Far Ultraviolet Spectroscopic Explorer spectrum. Cross-correletion analysis yielded an undelayed (time lag {approx} 0) component and a delayed component of 116 {+-} 17 s where the X-ray variations/fluctuations lagged the UV variations. This indicates that the UV fluctuations in the inner disk are propagated into the X-ray emitting region in about 116 s. The undelayed component may be related to irradiation effects.
- OSTI ID:
- 21612709
- Journal Information:
- Astrophysical Journal, Vol. 741, Issue 2; Other Information: DOI: 10.1088/0004-637X/741/2/84; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COSMOLOGY AND ASTRONOMY
ACCRETION DISKS
BOUNDARY LAYERS
CAMERAS
FAR ULTRAVIOLET RADIATION
INCLINATION
LUMINOSITY
NOVAE
PHOTON EMISSION
PHOTONS
PLASMA
SPECTROMETERS
WHITE DWARF STARS
X-RAY SPECTRA
BINARY STARS
BOSONS
DWARF STARS
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
EMISSION
ERUPTIVE VARIABLE STARS
LAYERS
MASSLESS PARTICLES
MEASURING INSTRUMENTS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SPECTRA
STARS
ULTRAVIOLET RADIATION
VARIABLE STARS