Reed L. Riddle

The Spectral Components of SS 433

We present results from new optical and UV spectroscopy of the unusual binary system SS 433, and we discuss the relationship of the particular spectral components that we observe to the properties of the binary. These spectral components include

Wind Accretion and State Transitions in Cygnus X-1

We present the results of a spectroscopic monitoring program (from 1998 to 2002) of the Hα emission strength in HDE 226868, the optical counterpart of the black hole binary Cyg X-1. The feature provides an important probe of the mass-loss rate in the base of the stellar wind of the supergiant star. We derive an updated ephemeris for the orbit based on radial velocities measured from He I λ6678. We list net equivalent widths for the entire Hα emission/absorption complex, and we find that there are large variations in emission strength over both long (years) and short (hours to days) time spans. There are coherent orbital phase-related variations in the profiles when the spectra are grouped by Hα equivalent width. The profiles consist of (1) a P Cygni component associated with the wind of the supergiant, (2) emission components that attain high velocity at the conjunctions and that probably form in enhanced outflows both toward and away from the black hole, and (3) an emission component that moves in antiphase with the supergiants motion. We argue that the third component forms in accreted gas near the black hole and that the radial velocity curve of the emission is consistent with a mass ratio of MX/Mopt ≈ 0.36 ± 0.05. We find that there is a general anticorrelation between the Hα emission strength and X-ray flux (from the Rossi X-Ray Timing Explorer All Sky Monitor) in the sense that when the Hα emission is strong (Wλ < -0.5 A) the X-ray flux is weaker and the spectrum harder. On the other hand, there is no correlation between Hα emission strength and X-ray flux when Hα is weak. We argue that this relationship is not caused by wind X-ray absorption nor by the reduction in Hα emissivity by X-ray heating. Instead, we suggest that the Hα variations track changes in wind density and strength near the photosphere. The density of the wind determines the size of X-ray ionization zones surrounding the black hole, and these in turn control the acceleration of the wind in the direction of the black hole. During the low/hard X-ray state, the strong wind is fast and the accretion rate is relatively low, while during the high/soft state, the weaker, highly ionized wind attains only a moderate velocity and the accretion rate increases. We argue that the X-ray transitions from the normal low/hard to the rare high/soft state are triggered by episodes of decreased mass-loss rate in the supergiant donor star.

Joint Hα and X-Ray Observations of Massive X-Ray Binaries. II. The Be X-Ray Binary and Microquasar LS I +61 303

We present the results of an H? monitoring campaign on the BeXRB and microquasar system LS I +61 303. We use radial velocity measurements of He I lines in our spectra to reevaluate the orbital elements and to better establish the time of periastron. We list equivalent widths and other parameters for the H? emission line and discuss the orbital phase related variations observed. We call attention to a dramatic episode of emission weakening that occurred in less than 1 day that probably resulted from exposure to a transient source of ionizing radiation. We argue that the increase in H? and X-ray emission following periastron probably results from the creation of an extended density wave in the disk created by tidal forces. We also discuss estimates of the size of the disk from the H? equivalent width measurements, and we suggest that the disk radius from the average equivalent width corresponds to a resonant truncation radius of the disk while the maximum equivalent width corresponds to a radius limited by the separation of the stars at periastron. We note that a nearby faint companion is probably an unrelated foreground object.

Joint Hα and X-Ray Observations of Massive X-Ray Binaries. III. The Be X-Ray Binaries HDE 245770 = A0535+26 and X Persei

We present results from an Hα monitoring campaign of the Be X-ray binary systems HDE 245770 = A0535+26 and X Per. We use the Hα equivalent widths together with adopted values of the Be star effective temperature, disk inclination, and disk outer boundary to determine the half-maximum emission radius of the disk as a function of time. The observations of HDE 245770 document the rapid spectral variability that apparently accompanied the regeneration of a new circumstellar disk. This disk grew rapidly during the years 1998-2000, but then slowed in growth in subsequent years. The outer disk radius is probably truncated by resonances between the disk gas and neutron star orbital periods. Two recent X-ray outbursts appear to coincide with the largest disk half-maximum emission radius attained over the last decade. Our observations of X Per indicate that its circumstellar disk has recently grown to near-record proportions, and concurrently the system has dramatically increased in X-ray flux, presumably the result of enhanced mass accretion from the disk. We find that the Hα half-maximum emission radius of the disk surrounding X Per reached a size about 6 times larger than the stellar radius, a value, however, that is well below the minimum separation between the Be star and neutron star. We suggest that spiral arms excited by tidal interaction at periastron may help lift disk gas out to radii where accretion by the neutron star companion becomes more effective.

The Orbit of the Massive X-Ray Binary LS 5039

We present the first spectroscopic orbit for the massive X-ray binary LS 5039, which we find to be a short-period (P = 4.117 ± 0.011 days) and highly eccentric (e = 0.41 ± 0.05) system. The low-mass function for the orbit appears to be most consistent with a neutron star companion, although a black hole remains a possibility if the system has a low inclination. The spectrum of the O7 V optical star appears to be normal for its type (suggesting that there is little flux in the red from an accretion disk) except that the C IV λλ5801, 5812 lines are very weak, perhaps indicating the presence of CNO-processed gas in the O star. There is no evidence of Hα emission, so the system is probably not currently undergoing Roche lobe overflow. The projected rotational velocity, V sin i = 131 ± 6 km s-1, suggests that the optical star is rotating faster than synchronously with the orbit. The peculiar component of the systemic radial velocity is -17 ± 3 km s-1, so the system is not a runaway star (at least not in this dimension).

ι Orionis—Evidence for a Capture Origin Binary

The star ι Ori (HD 37043, HR 1899) is a 29.1338 day period, double-lined O-type spectroscopic binary with a highly eccentric orbit. The classification of the primary (O9 III) is well established. The secondary, roughly 2 mag fainter, is generally acknowledged as an early-type B star, but claims about its luminosity class have been made only from its estimated light contribution and not from its spectrum. We have collected visual data with the 1 m Multiple-Telescope Telescope (MTT; at the Center for High Angular Resolution at Georgia State University) in four wave bands well distributed in orbital phase, with the periastron passage particularly well covered. We present reconstructed component spectra from our tomographic reconstruction technique. According to three Morgan-Keenan (MK) luminosity criteria, we can unambiguously characterize the secondary as a B1 III-IV giant (MK type or B0.8 III-IV interpolated type). We also have constructed three line-strength indices from eighteen observed individual lines for the secondary and a grid of comparison stars. These results confirm the typing from the MK luminosity criteria. Furthermore, we argue, from the mass ratio (q = 0.5), evolutionary considerations, the orbital scale, and the unremarkable CNO element equivalent widths of the secondary, that this system is not coevolved nor has it undergone significant mass transfer. We postulate an origin for the system in a binary-binary collision and suspect that the runaway stars μ Col and AE Aur may have been the original partners for the current ι Ori secondary and primary, respectively.

Joint Hα and X-Ray Observations of Massive X-Ray Binaries. I. The B Supergiant System LS I +65 010 = 2S 0114+650

We report on a 3 yr spectroscopic monitoring program of the Hα emission in the massive X-ray binary LS I +65 010 = 2S 0114+650, which consists of a B supergiant and a slowly rotating X-ray pulsar. We present revised orbital elements that yield a period of P = 11.5983 ± 0.0006 days and confirm that the orbit has a nonzero eccentricity e = 0.18 ± 0.05. The Hα emission profile is formed in the base of the wind of the B supergiant primary, and we show how this spectral feature varies on timescales that are probably related to the rotational period of the B supergiant. We also examine the X-ray fluxes from the Rossi X-ray Timing Explorer All-Sky Monitor instrument, and we show that the X-ray orbital light curve has a maximum at periastron and a minimum at the inferior conjunction of the B supergiant. We also show that the wind emission strength and the high-energy X-ray flux appear to vary in tandem on timescales of approximately 1 yr.

Ultraviolet and Optical Line Profile Variations in the Spectrum of epsilon Persei

The rapid variable star, v Per (B0.5 IVIII), displays the largest amplitude pro—le —uctuations known among the growing number of massive, spectrum-variable stars. Here we present an analysis of a contin- uous 5 day run of IUE UV spectroscopy, and we show for the —rst time that the systematic, blue-to-red moving patterns observed in high-quality optical spectra are also present in the UV photospheric lines. We present cross-correlation functions of the individual spectra with that of a narrow-lined standard that produce a high signal-to-noise ratio representation of the blue-to-red moving bump patterns found in individual lines. We then use time series analysis methods to determine the periodic components of the pro—le variations (after reregistering the spectra to correct for binary motion). There are at least six periods present (ranging from 8.46 to 2.27 hr), and most of these signals are also found in optical line variations observed in 1986 (although the relative amplitudes have changed signi—cantly). Furthermore, analysis of a shorter time series of IUE spectra from 1984 shows that similar periods were present then. We also present Ha and He I j6678 pro—les obtained with the Georgia State University Multi-Telescope Telescope, which were made simultaneously with IUE, and we show that the pro—le variations are essen- tially identical in the UV and optical ranges. We rule out rotational modulation and circumstellar gas obscuration as possible causes, and we suggest instead that the variations are the result of photospheric nonradial pulsations of relatively low degree (l \ 3¨5). There were signi—cant changes (D10%) in the equivalent widths of the UV stellar wind lines during the IUE run, and we suggest that wind strength- ening events are related to episodes of large-amplitude, constructive interference between the NRP modes. Thus, intermode beating may play an important role in promoting wind loss from massive stars. Subject headings: binaries: spectroscopicstars: early-typestars: individual (v Persei) ¨ stars: oscillationsstars: winds, out—owsultraviolet: stars

Mass and Angular Momentum Transfer in the Massive Algol Binary RY Persei

We present an investigation of the Hα emission-line variations observed in the massive Algol binary RY Per. We give new radial velocity data for the secondary based on our optical spectra and for the primary based on high-dispersion UV spectra. We present revised orbital elements and an estimate of the primarys projected rotational velocity (which indicates that the primary is rotating 7 times faster than the synchronous rate). We use a Doppler tomography algorithm to reconstruct the individual primary and secondary spectra in the region of Hα, and we subtract the latter from each of our observations to obtain profiles of the primary and its disk alone. Our Hα observations of RY Per show that the mass-gaining primary is surrounded by a persistent but time-variable accretion disk. The profile that is observed outside eclipse has weak double-peaked emission flanking a deep central absorption, and we find that these properties can be reproduced by a disk model that includes the absorption of photospheric light by the band of the disk seen in projection against the face of the star. We developed a new method to reconstruct the disk surface density distribution from the ensemble of Hα profiles observed around the orbit, and this method accounts for the effects of disk occultation by the stellar components, the obscuration of the primary by the disk, and flux contributions from optically thick disk elements. The resulting surface density distribution is elongated along the axis joining the stars in the same way as seen in hydrodynamical simulations of gas flows that strike the mass gainer near the trailing edge of the star. This type of gas stream configuration is optimal for the transfer of angular momentum, and we show that rapid rotation is found in other Algol systems that have passed through a similar stage.

Tomographic Separation of Composite Spectra. V. The Triple Star System 55 Ursae Majoris

We present moderate-resolution spectra obtained with the Georgia State University Multi-Telescope Telescope of 55 UMa, a triple system consisting of a 2.55 day spectroscopic binary and a third star in a 1873 day orbit (detected by speckle interferometry). We observed the spectral lines of all three stars, and we present radial velocity curves for both the close and wide orbits. We also present new speckle interferometric measurements and a revised solution of the astrometric (wide) orbit. The spectrum of each star was reconstructed using Doppler tomography, and we measured ratios of Fe I and Fe II lines in both the reconstructions and model synthetic spectra to estimate the stellar effective temperatures. These temperatures correspond to spectral types of A1 V and A2 V for the close pair and A1 V for the distant third star. We show that the metallic lines of the close pair are systematically strong, and we suggest that both objects are moderate Am stars. All the components have masses close to 2 M☉, and continued spectroscopic and astrometric observations will yield precise masses and absolute magnitudes.