Coordinated X-ray, ultraviolet and optical observations of AM Herculis, U Geminorum, and SS Cygni

Journal Article · Sun Feb 01 04:00:00 EST 1981 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/158656· OSTI ID:6335639

Fabbiano, G; Hartmann, L; Raymond, J; Steiner, J; Branduardi-Raymont, G; Matilsky, T

Simultaneous and quasi-simultaneous observations of AM Her, U Gem, and SS Cyg with the Einstein and International Ultraviolet Explorer (IUE) satellites are reported, with optical monitoring provided by the American Association of Variable Star Observers (AAVSO). AM Her appeared to be in a high state at the time of the observations, while SS Cyg and U GEm were in the optical low state. SS Cyg was also observed photometrically at the same time as the UV and X-ray observations. We detect hard (>1 keV) X-rays from U Gem at minimum, but at much lower intensity than in AM Her and SS Cyg. The optical/UV/X-ray spectra of AM Her and SS Cyg are remarkably similar both in the cotinuum and in the UV emission lines. Although U Gem exhibits absorption lines on a continuous UV spectrum, it is similar to the other two systems in exhibiting a UV blackbody component with kT>10 eV. The fluxes in these components are in excess of both the hard X-ray and optical fluxes. This is inconsistent with standard accretion disk and accretion column models. We suggest that nuclear burning at the surface of the white dwarf might be responsible for the excess UV flux. This assumes that the same basic mechanisms operate in these cataclysmic variables, but different detailed spectral distributions result from different balances between magnetic field intensity and accretion rates.

• Research Organization: Harvard/Smithsonian Center for Astrophysics
• OSTI ID: 6335639
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 243:3; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BINARY STARS
BLACKBODY RADIATION
COSMIC RAY SOURCES
COSMIC X-RAY SOURCES
DWARF STARS
ELECTROMAGNETIC RADIATION
EMISSION
ERUPTIVE VARIABLE STARS
HARD X RADIATION
IONIZING RADIATIONS
LUMINOSITY
MAGNETIC FIELDS
NOVAE
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
SPECTRA
STAR ACCRETION
STAR EVOLUTION
STARS
ULTRAVIOLET RADIATION
ULTRAVIOLET SPECTRA
VARIABLE STARS
VISIBLE SPECTRA
WHITE DWARF STARS
X RADIATION
X-RAY SPECTRA