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We present near-infrared (NIR) broadband (0.80-2.42 μm) spectroscopy of two low-mass X-ray binaries: V404 Cyg and Cen X-4. One important parameter required in the determination of the mass of the compact objects in these systems is the binary inclination. We can determine the inclination by modeling the ellipsoidal modulations of the Roche-lobe filling donor star, but the contamination of the donor star light from other components of the binary, particularly the accretion disk, must be taken into account. To this end, we determined the donor star contribution to the infrared flux by comparing the spectra of V404 Cyg and Cen X-4 to those of various field K-stars of known spectral type. For V404 Cyg, we determined that the donor star has a spectral type of K3 III. We determined the fractional donor contribution to the NIR flux in the H and K bands as 0.98 ± 0.05 and 0.97 ± 0.09, respectively. We remodeled the H-band light curve from Sanwal et al. after correcting for the donor star contribution to obtain a new value for the binary inclination. From this, we determined the mass of the black hole in V404 Cyg to be M BH = 9.0 +0.2 −0.6 M . We performed the same spectral analysis for Cen X-4 and found the spectral type of the donor star to be in the range K5-M1 V. The donor star contribution in Cen X-4 is 0.94 ± 0.14 in the H band while in the K band, the accretion disk can contribute up to 10% of the infrared flux. We remodeled the H-band light curve from Shahbaz et al., again correcting for the fractional contribution of the donor star to obtain the inclination. From this, we determined the mass of the neutron star as M NS = 1.5 +0.1 −0.4 M . However, the masses obtained for both systems should be viewed with some caution since contemporaneous light curve and spectral data are required to obtain definitive masses.

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We obtained high-dispersion spectroscopy of CI Cam, the optical counterpart of XTE J0421]560, 2 weeks after the peak of its short outburst in 1998 April. The optical counterpart is a supergiant B[e] star that is emitting a two-component wind, a cool, low-velocity wind and a hot, high-velocity wind. The cool wind, which is the source of narrow emission lines of neutral and ionized metals, has a velocity of 32 km s~1 and a temperature near 8000 K. It is dense, roughly spherical, Ðlls the space around the sgB[e] star, and, based on the size of an infrared-emitting dust shell around the system, extends to a radius between 13 and 50 AU. It carries away mass at a high rate, yr~1. The hot wind M 0 [ 10~6 M _ has a velocity in excess of 2500 km s~1 and a temperature of 1.7^0.3 ] 104 K. From an ultraviolet spectrogram of CI Cam obtained in 2000 March with Hubble Space T elescope, we derive a di †erential extinction E(B[V ) \ 0.85^0.05. We show that the distance to CI Cam is greater than 5 kpc. Based on this revised distance, the X-ray luminosity at the peak of the outburst was L (2È25 keV) [ 3.0 ] 1038 ergs s~1, making CI Cam one of the most luminous X-ray transients. The ratio of quiescent luminosity to peak luminosity in the 2È25 keV band isThein the dense circumstellar wind from the sgB[e] star and burrows through the wind, producing little X-ray emission except for rare transient outbursts. This picture, a compact star traveling in a wide orbit through the dense circumstellar envelope of a sgB[e] star, occasionally producing transient X-ray outbursts, makes CI Cam unique among the known X-ray binaries. There is strong circumstantial evidence that the compact object is a black hole, not a neutron star. We speculate that the X-ray outburst was short because the accretion disk around the compact star is fed from a stellar wind and is smaller than disks fed by Roche lobe overÑow.

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We have performed a spectral principal component analysis (SPCA) for an essentially complete sample of 22 low redshift QSOs with spectral data from Lyα to Hα. SPCA yields a set of independent principal component spectra, each of which represents a set of relationships among QSO continuum and line properties. We find three significant principal components, which account for ∼78% of the total intrinsic variance. The first component, carrying ∼41% of the intrinsic variance, represents Baldwin relationships -anti-correlations between equivalent width of broad emission lines and continuum luminosity. The narrow line core (FWHM ∼2000 km s −1 ) of the broad emission lines dominate this component. The second component, accounting for ∼23% of the intrinsic variance, represents the variations in UV continuum slope, which is probably the result of dust reddening, with possible contributions from starlight. The third principal component is directly related to the Boroson & Green "Eigenvector 1" (their first principal component), clearly showing the anti-correlation between strengths of optical Fe ii and [O iii] λ5007, and other relationships previously found in the Hβ -[O iii] region. This third component shows the expected strong correlation with soft X-ray spectral index. The widths of C iii] λ1909, Mg ii λ2798, and Balmer emission lines are also involved and clearly correlated, relating this component to black hole mass or Eddington accretion ratio. We find an inverse correlation between the strengths of the UV and optical Fe ii blends, as suggested by some photoionization models. We also find correlations of the strengths of several low-ionization UV lines with Fe ii(opt), and a strong positive correlation of C iv λ1549 with [O iii] strength. The wide wavelength coverage of our data enable us to see clearly the relationships between the UV and optical spectra of QSOs. The Baldwin effect and Boroson & Green's Eigenvector 1 relationship are clearly independent. We demonstrate how Baldwin relationships can be derived using our first principal component, virtually eliminating the scatter caused by the third principal component. This rekindles the hope that the Baldwin relationships can be used for cosmological study.