Ultraviolet Spectra of CV Accretion Disks with Non-Steady T(r) Laws

An extensive grid of synthetic mid- and far-ultraviolet spectra for accretion disks in cataclysmic variables has been presented by Wade and Hubeny (1998). In those models, the disk was assumed to be in steady-state, that is T_eff(r) is specified completely by the mass M_WD and radius R_WD of the accreting white dwarf star and the mass transfer rate M_dot which is constant throughout the disk. In these models, T_eff(r) is proportional to r^{-3/4} except as modified by a cutoff term near the white dwarf. Actual disks may vary from the steady-state prescription for T_eff(r), however, e.g. owing to outburst cycles in dwarf novae M_dot not constant with radius) or irradiation (in which case T_eff in the outer disk is raised above T_steady). To show how the spectra of such disks might differ from the steady case, we present a study of the ultraviolet (UV) spectra of models in which power-law temperature profiles T_eff(r) is proportional to r^{-gamma} with gamma < 3/4 are specified. Otherwise, the construction of the models is the same as in the Wade & Hubeny grid, to allow comparison. We discuss both the UV spectral energy distributions and the appearance of the UV line spectra. We also briefly discuss the eclipse light curves of the non-standard models. Comparison of these models with UV observations of novalike variables suggests that better agreement may be possible with such modified T_eff(r) profiles.Comment: 13 pages, 6 figures (one reduced quality), ApJ in pres

Modeling the Jet Kinematics of the Black Hole Microquasar XTE J1550-564: A Constraint on Spin-Orbit Alignment

Measurements of black hole spin made using the continuum-fitting method rely on the assumption that the inclination of the black hole's spin axis to our line of sight is the same as the orbital inclination angle of the host binary system. The X=ray and radio jet data available for the microquasar XTE J1550-564 offer a rare opportunity to test this assumption. Following the work of others, we have modeled these data and thereby determined the inclination angle of the jet axis, which is presumed to be aligned with the black hole's spin axis. We find a jet inclination angle of approximately 71 degrees and place an upper limit on the difference between the spin and orbital inclinations of < 12 degrees (90% confidence). Our measurement tests for misalignment along the line of sight while providing no constraint perpendicular to this plane. Our constraint on the misalignment angle supports the prediction that the spinning black hole in XTE J1550-564 has aligned itself with the orbital plane and provides support for the measurement of its spin via the continuum-fitting method. Our conclusions are based on a simple and reasonable model of a pair of symmetric jets propagating into a low density cavity whose western wall is approximately 20% closer to XTE J1550-564 than its eastern wall.Comment: ApJ, in press. 26 manuscript pages including 6 figure

Bow shocks in water fountain jets

We briefly introduce the VLBI maser astrometric analysis of IRAS 18043-2116 and IRAS 18113-2503, two remarkable and unusual water fountains with spectacular bipolar bow shocks in their high-speed collimated jet-driven outflows. The 22 GHz H2O maser structures and velocities clearly show that the jets are formed in very short-lived, episodic outbursts, which may indicate episodic accretion in an underlying binary system.Comment: To appear in the proceedings of the IAU Symposium 336: Astrophysical Masers: Unlocking the Mysteries of the Universe (4-8 September 2017, Cagliari, Italy) - IAU Proceedings Series, eds. A. Tarchi, M. J. Reid, and P. Castangi

The Low-Spin Black Hole in LMC X-3

Building upon a new dynamical model for the X-ray binary LMC X-3, we measure the spin of its black hole primary via the continuum-fitting method. We consider over one thousand thermal-state RXTE X-ray spectra of LMC X-3. Using a large subset of these spectra, we constrain the spin parameter of the black hole to be spin = 0.21(+0.18,-0.22), 90% confidence. Our estimate of the uncertainty in spin takes into account a wide range of systematic errors. We discuss evidence for a correlation between a black hole's spin and the complexity of its X-ray spectrum.Comment: Submitted to ApJL, 5 pages emulateapj, 2 figures and 1 tabl