Search

We have analyzed OGLE-III photometry for stars in the SMC cluster NGC 299. Two eclipsing binaries and one intrinsic variable (most likely a Be star) are identified. Unlike other young SMC clusters, no low-amplitude pulsating variables are present., Comment: Draft Version April 15th, 2013 accepted for publication in IBVS on April 19, 2013. 8 pages, 1 table, 4 figures

We have analyzed OGLE-III photometry for stars in the SMC cluster NGC 299. Two eclipsing binaries and one intrinsic variable (most likely a Be star) are identified. Unlike other young SMC clusters, no low-amplitude pulsating variables are present., Comment: Draft Version April 15th, 2013 accepted for publication in IBVS on April 19, 2013. 8 pages, 1 table, 4 figures

We have studied five seasons of OGLE-III data for eight SMC Be/X-ray pulsars for which no other survey data were available. We have determined orbital periods for four of these binary systems, one of which also shows nonradial pulsations. Optical identification of SMC X-2 is reconsidered, but no periods were found for either of the two possible candidates.

We have studied the photometric variability of ten SMC Be/X-ray pulsars using MACHO and OGLE-II data. For some of these systems we have found periodic behavior, including orbital outbursts and/or nonradial pulsations (NRP) of the Be star. For others we were unable to identify any clear photometric periodicity, although their longterm light curves show significant structure. We present periodograms, phase dispersion minimization (PDM) variances, and folded light curves for the systems which exhibit periodic photometric variability., Comment: 20 pages and 7 figures

We have studied five seasons of OGLE-III data for eight SMC Be/X-ray pulsars for which no other survey data were available. We have determined orbital periods for four of these binary systems, one of which also shows nonradial pulsations. Optical identification of SMC X-2 is reconsidered, but no periods were found for either of the two possible candidates.

We have studied the photometric variability of ten SMC Be/X-ray pulsars using MACHO and OGLE-II data. For some of these systems we have found periodic behavior, including orbital outbursts and/or nonradial pulsations (NRP) of the Be star. For others we were unable to identify any clear photometric periodicity, although their longterm light curves show significant structure. We present periodograms, phase dispersion minimization (PDM) variances, and folded light curves for the systems which exhibit periodic photometric variability., Comment: 20 pages and 7 figures

X-ray data reveal that the supersoft X-ray binary CAL 83 exhibits 38.4 minute pulsations at some epochs. These X-ray variations are similar to those found in some novae and are likely to be caused by nonradial pulsations the white dwarf. This is the first detection of pulsations in a classical supersoft X-ray binary., Comment: revised text; 11 pages and 3 figures; accepted for publication in the Astronomical Journal

Analysis of the longterm photometric variability of 7 Be/X-ray-pulsar systems in the Small Magellanic Cloud has been carried out. We find a variety of types of variability are present, including: longterm irregular changes, periodic orbital outbursts due to interaction between the stars (weeks to months), low-amplitude quasi-periodic variations of the equatorial disk (days), and nonradial pulsations of the Be primary star (hours). This is the first time nonradial pulsations have been identified in Be/X-ray binaries, although they were previously known in some single Be stars., Comment: 27 pages, 15 figures

FUSE observations were obtained in July 2003 during 1.2 cycles of the 0.76-day binary orbit of RX J0513.9-6951. Radial velocity measurements of the broad O VI emission profile show a semiamplitude of K~26 km/sec, which is much smaller than the value of 117 km/sec measured from 2001 FUSE data. Narrow O VI emissions show no measurable velocity variation. The mean velocity of the broad O VI emission is red-shifted by ~500 km/sec with respect to both the systemic and narrow emission-line velocities. Spectral difference plots show phase-related changes in the broad emission profile. Other phase-related changes such as line and continuum variations are also smaller than in the 2001 spectra. We describe a moving broad absorption feature near 1020A as possible O VI outflow associated with a precessing jet. We discuss the implications for the stellar masses if the 2003 broad O VI velocities outline the compact star's orbital motion., Comment: 16 pages, including 7 figures. To appear in AJ

X-ray data reveal that the supersoft X-ray binary CAL 83 exhibits 38.4 minute pulsations at some epochs. These X-ray variations are similar to those found in some novae and are likely to be caused by nonradial pulsations the white dwarf. This is the first detection of pulsations in a classical supersoft X-ray binary., Comment: revised text; 11 pages and 3 figures; accepted for publication in the Astronomical Journal

Analysis of the longterm photometric variability of 7 Be/X-ray-pulsar systems in the Small Magellanic Cloud has been carried out. We find a variety of types of variability are present, including: longterm irregular changes, periodic orbital outbursts due to interaction between the stars (weeks to months), low-amplitude quasi-periodic variations of the equatorial disk (days), and nonradial pulsations of the Be primary star (hours). This is the first time nonradial pulsations have been identified in Be/X-ray binaries, although they were previously known in some single Be stars., Comment: 27 pages, 15 figures

FUSE observations were obtained in July 2003 during 1.2 cycles of the 0.76-day binary orbit of RX J0513.9-6951. Radial velocity measurements of the broad O VI emission profile show a semiamplitude of K~26 km/sec, which is much smaller than the value of 117 km/sec measured from 2001 FUSE data. Narrow O VI emissions show no measurable velocity variation. The mean velocity of the broad O VI emission is red-shifted by ~500 km/sec with respect to both the systemic and narrow emission-line velocities. Spectral difference plots show phase-related changes in the broad emission profile. Other phase-related changes such as line and continuum variations are also smaller than in the 2001 spectra. We describe a moving broad absorption feature near 1020A as possible O VI outflow associated with a precessing jet. We discuss the implications for the stellar masses if the 2003 broad O VI velocities outline the compact star's orbital motion., Comment: 16 pages, including 7 figures. To appear in AJ

A new ephemeris has been determined for the supersoft X-ray binary CAL 83 using MACHO photometry. With an improved orbital period of 1.047568 days, it is now possible to phase together photometric and spectroscopic data obtained over the past two decades with new far ultraviolet spectra taken with FUSE. We discuss the properties of the orbital and longterm optical light curves as well as the colors of CAL 83. In the far ultraviolet the only well-detected stellar feature is emission from the O VI resonance doublet. The radial velocity of this emission appears to differ from that of HeII in the optical region, although we only have partial phase coverage for the O VI line. The FUSE continuum variations are similar to the optical light curve in phase and amplitude., Comment: 21 pages and 7 figures

The optical light curve of the Be/neutron star binary AX J0049.4-7323 has been investigated using data from the MACHO and OGLE-II projects. This X-ray source, whose neutron star has a very slow rotation rate (P_pulse=755.5 sec), shows optical outbursts every 394 days. The regularity of these outbursts suggests that their recurrence time is the orbital period of the system. During the outbursts the system brightens and becomes slightly redder. A possible interpretation is that a portion of the equatorial disk is excited as the neutron star passes through it during periastron passage. In the intervals between outbursts the light curve shows 11-day quasi-periodic varability which may be associated with the rotation of the Be star's extended disk., Comment: 10 pages and 5 figures

Far-ultraviolet spectra of LMC X-3 were taken covering photometric phases 0.47 to 0.74 in the 1.7-day orbital period of the black-hole binary (phase zero being superior conjunction of the X-ray source). The continuum is faint and flat, but appears to vary significantly during the observations. Concurrent RXTE/ASM observations show the system was in its most luminous X-ray state during the FUSE observations. The FUV spectrum contains strong terrestrial airglow emission lines, while the only stellar lines clearly present are emissions from the O VI resonance doublet. Their flux does not change significantly during the FUSE observations. These lines are modelled as two asymmetrical profiles, including the local ISM absorptions due to C II and possibly O VI. Velocity variations of O VI emission are consistent with the orbital velocity of the black hole and provide a new constraint on its mass., Comment: 12 pages including 1 table, 4 diagrams To appear in AJ

The optical light curve of the Be/neutron star binary AX J0049.4-7323 has been investigated using data from the MACHO and OGLE-II projects. This X-ray source, whose neutron star has a very slow rotation rate (P_pulse=755.5 sec), shows optical outbursts every 394 days. The regularity of these outbursts suggests that their recurrence time is the orbital period of the system. During the outbursts the system brightens and becomes slightly redder. A possible interpretation is that a portion of the equatorial disk is excited as the neutron star passes through it during periastron passage. In the intervals between outbursts the light curve shows 11-day quasi-periodic varability which may be associated with the rotation of the Be star's extended disk., Comment: 10 pages and 5 figures

A new ephemeris has been determined for the supersoft X-ray binary CAL 83 using MACHO photometry. With an improved orbital period of 1.047568 days, it is now possible to phase together photometric and spectroscopic data obtained over the past two decades with new far ultraviolet spectra taken with FUSE. We discuss the properties of the orbital and longterm optical light curves as well as the colors of CAL 83. In the far ultraviolet the only well-detected stellar feature is emission from the O VI resonance doublet. The radial velocity of this emission appears to differ from that of HeII in the optical region, although we only have partial phase coverage for the O VI line. The FUSE continuum variations are similar to the optical light curve in phase and amplitude., Comment: 21 pages and 7 figures

Far-ultraviolet spectra of LMC X-3 were taken covering photometric phases 0.47 to 0.74 in the 1.7-day orbital period of the black-hole binary (phase zero being superior conjunction of the X-ray source). The continuum is faint and flat, but appears to vary significantly during the observations. Concurrent RXTE/ASM observations show the system was in its most luminous X-ray state during the FUSE observations. The FUV spectrum contains strong terrestrial airglow emission lines, while the only stellar lines clearly present are emissions from the O VI resonance doublet. Their flux does not change significantly during the FUSE observations. These lines are modelled as two asymmetrical profiles, including the local ISM absorptions due to C II and possibly O VI. Velocity variations of O VI emission are consistent with the orbital velocity of the black hole and provide a new constraint on its mass., Comment: 12 pages including 1 table, 4 diagrams To appear in AJ

We have obtained spectroscopy with the Far Ultraviolet Spectroscopic Explorer (FUSE) of the supersoft X-ray binary RX J0513.9-6951 over a complete binary orbital cycle. The spectra show a hot continuum with extremely broad O VI emission and weak Lyman absorptions. He II emission is weak and narrow, while N III and C III emissions are undetected, although lines from these ions are prominent at optical wavelengths. The broad O VI emission and Lyman absorption show radial velocity curves that are approximately antiphased and have semiamplitudes of ~117 +- 40 and 54 +- 10 km/s, respectively. Narrow emissions from He II and O VI show small velocity variations with phasing different from the broad O VI, but consistent with the optical line peaks. We also measure considerable changes in the FUV continuum and O VI emission line flux. We discuss the possible causes of the measured variations and a tentative binary interpretation., Comment: 21 pages, including 2 tables, 6 figures. To appear in AJ

We have analyzed nearly eight years of MACHO optical photometry of the supersoft X-ray binary RX J0513.9-6951 and derived a revised orbital period and ephemeris. Previously published velocities are reinterpreted using the new ephemeris. We show that the spectroscopic characteristics of the system depend strongly on whether the system is in a high or low optical state. We also discuss the properties of the source's high/low optical states and its long-term light curve. Evidence for a 83.3-day periodicity in the photometry is presented., Comment: 16 pages, including 1 table, 5 figures. To appear in AJ

Spectra of the magnetic white dwarf binary AM Her were obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) during three consecutive spacecraft orbits. These observations were split into 19 spectra of about 5 min duration (0.025P binary phase) partially covering the binary orbit. We report the phase-related changes in the far ultraviolet continuum light curve and the emission lines, noting particularly the behavior of O VI. We discuss the fluxes and velocities of the narrow and broad O VI emissions. We find the FUV light curve has maximum amplitude at ~1000A, although at shorter wavelengths the continuum may be strongly affected by overlapping Lyman lines. Weak, narrow Lyman absorption lines are present. Their velocities don't appear to vary over the observed orbital phases, and their mean value is consistent with the systemic velocity., Comment: 19 pages including 2 tables, 5 diagrams. To appear in AJ

We have analyzed nearly eight years of MACHO optical photometry of the supersoft X-ray binary RX J0513.9-6951 and derived a revised orbital period and ephemeris. Previously published velocities are reinterpreted using the new ephemeris. We show that the spectroscopic characteristics of the system depend strongly on whether the system is in a high or low optical state. We also discuss the properties of the source's high/low optical states and its long-term light curve. Evidence for a 83.3-day periodicity in the photometry is presented., Comment: 16 pages, including 1 table, 5 figures. To appear in AJ

We have obtained spectroscopy with the Far Ultraviolet Spectroscopic Explorer (FUSE) of the supersoft X-ray binary RX J0513.9-6951 over a complete binary orbital cycle. The spectra show a hot continuum with extremely broad O VI emission and weak Lyman absorptions. He II emission is weak and narrow, while N III and C III emissions are undetected, although lines from these ions are prominent at optical wavelengths. The broad O VI emission and Lyman absorption show radial velocity curves that are approximately antiphased and have semiamplitudes of ~117 +- 40 and 54 +- 10 km/s, respectively. Narrow emissions from He II and O VI show small velocity variations with phasing different from the broad O VI, but consistent with the optical line peaks. We also measure considerable changes in the FUV continuum and O VI emission line flux. We discuss the possible causes of the measured variations and a tentative binary interpretation., Comment: 21 pages, including 2 tables, 6 figures. To appear in AJ

Spectra of the magnetic white dwarf binary AM Her were obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) during three consecutive spacecraft orbits. These observations were split into 19 spectra of about 5 min duration (0.025P binary phase) partially covering the binary orbit. We report the phase-related changes in the far ultraviolet continuum light curve and the emission lines, noting particularly the behavior of O VI. We discuss the fluxes and velocities of the narrow and broad O VI emissions. We find the FUV light curve has maximum amplitude at ~1000A, although at shorter wavelengths the continuum may be strongly affected by overlapping Lyman lines. Weak, narrow Lyman absorption lines are present. Their velocities don't appear to vary over the observed orbital phases, and their mean value is consistent with the systemic velocity., Comment: 19 pages including 2 tables, 5 diagrams. To appear in AJ

FUSE spectra were obtained of the supersoft X-ray binary RX J0019.8+2156 (QR And) during 16 consecutive spacecraft orbits, covering the binary orbit (P=15.85 hr) with about 0.2 phase overlap. The spectrum is dominated by strong H2 absorption (column density ~10**20 g/cm**2), which appears at a radial velocity different from other interstellar absorption lines and may be partially circumbinary. This absorption makes study of spectral features from the binary system difficult. The only well-detected emission lines are He II, 1085A, and O VI, 1032A, (the other line of the O VI doublet, 1037A, is largely obscured by strong H2 absorption). The O VI shows a P Cygni profile that varies in velocity and strength with binary phase. We compare this with similar changes seen in Balmer line profiles. We extract the FUV light curve and compare it with the optical light curve. There is an eclipse in both wavelength regions, but the FUV minimum lasts much longer, well beyond the visible light egress. The FUV results are discussed in connection with the binary model and mass flows within the system., Comment: 18 pages including 1 table, plus 5 figures; to appear in AJ

FUSE spectra were obtained of the supersoft X-ray binary RX J0019.8+2156 (QR And) during 16 consecutive spacecraft orbits, covering the binary orbit (P=15.85 hr) with about 0.2 phase overlap. The spectrum is dominated by strong H2 absorption (column density ~10**20 g/cm**2), which appears at a radial velocity different from other interstellar absorption lines and may be partially circumbinary. This absorption makes study of spectral features from the binary system difficult. The only well-detected emission lines are He II, 1085A, and O VI, 1032A, (the other line of the O VI doublet, 1037A, is largely obscured by strong H2 absorption). The O VI shows a P Cygni profile that varies in velocity and strength with binary phase. We compare this with similar changes seen in Balmer line profiles. We extract the FUV light curve and compare it with the optical light curve. There is an eclipse in both wavelength regions, but the FUV minimum lasts much longer, well beyond the visible light egress. The FUV results are discussed in connection with the binary model and mass flows within the system., Comment: 18 pages including 1 table, plus 5 figures; to appear in AJ

We present and discuss 25 spectra obtained in November 1996, covering all phases of the CAL 87 binary system. These spectra are superior both in signal-to-noise and wavelength coverage to previously published data so that additional spectral features can be measured. Photometry obtained on the same nights is used to confirm the ephemeris and to compare with light curves from previous years. Analysis of the color variation through the orbital cycle has been carried out using archival MACHO data. When a barely resolved red field star is accounted for, there is no (V-R)-color variation, even through eclipse. There have been substantial changes in the depth of minimum light since 1988; it has decreased more than 0.5 mag in the last several years. The spectral features and radial velocities are also found to vary not only through the 0.44-day orbit but also over timescales of a year or more. Possible interpretations of these long-term changes are discussed. The 1996 spectra contain phase-modulated Balmer absorption lines not previously seen, apparently arising in gas flowing from the region of the compact star. The changes in emission-line strengths with orbital phase indicate there are azimuthal variations in the accretion disk structures. Radial velocities of several lines give different amplitudes and phasing, making determination of the stellar masses difficult. All solutions for the stellar masses indicate that the companion star is considerably less massive than the degenerate star. The Balmer absorption-line velocities correspond to masses of ~1.4Msun for the degenerate star and ~0.4Msun for the mass donor. However, the strong He II emission lines indicate a much more massive accreting star, with Mx>4Msun., Comment: 18 pages including tables, plus10 figures. To appear in ApJ

A comparison is made between the properties of CAL 83, CAL 87, RX J0513.9-6951, 1E 0035.4-7230 (SMC 13), RX J0019.8+2156, and RX J0925.7-4758, all supersoft X-ray binaries. Spectra with the same resolution and wavelength coverage of these systems are compared and contrasted. Some new photometry is also presented. The equivalent widths of the principal emission lines of H and He II differ by more than an order of magnitude among these sources, although those of the highest ionization lines (e.g. O VI) are very similar. In individual systems, the velocity curves derived from various ions often differ in phasing and amplitude, but those whose phasing is consistent with the light curves (implying the lines are formed near the compact star) give masses of $\sim 1.2M_{\odot}$ and $\sim 0.5M_{\odot}$ for the degenerate and mass-losing stars, respectively. This finding is in conflict with currently prevailing theoretical models for supersoft binaries. The three highest luminosity sources show evidence of "jet" outflows, with velocities of $\sim 1-4 \times10^3 km/s$. In CAL 83 the shape of the He II 4686\AA profile continues to show evidence that these jets may precess with a period of $\sim 69$ days., Comment: 27 pages including 5 tables, plus 6 figures. To appear in ApJ

This paper concludes a series of three papers presenting ROSAT High-Resolution Imager (HRI) observations of unidentified Einstein and serendipitous ROSAT X-ray sources in the direction of the Magellanic Clouds. Accurate positions and fluxes have been measured for these sources. Optical photometry and spectroscopy were obtained to search for identifications in order to determine the physical nature of these sources. The present paper includes new data for 24 objects; identifications are given or confirmed for 30 sources. For six sources optical finding charts showing the X-ray positions are provided. The results from this program are summarized, showing the populations of luminous X-ray sources in the Magellanic Clouds are quite different from those in the Galaxy., Comment: 28 pages, 2 figures; to appear in Astronomical Journal

The luminous X-ray binary and black-hole candidate LMC X-1 has been observed with the Rossi X-ray Timing Explorer (RXTE) to search for quasi-periodic oscillations (QPO), previously reported in its high state. The source was observed monthly in a series of nine observations. Analysis of the temporal variations shows no evidence for QPO or other periodic changes, but correlations between the high-energy light curve and hardness of the spectrum are described. Spectral fits with two-component models demonstrate that the hardness variations come from changes in the intensity of the high-energy power-law tail., Comment: 10 pages plus figures; to appear in Astronomical Journal

The luminous X-ray binary and black-hole candidate LMC X-1 has been observed with the Rossi X-ray Timing Explorer (RXTE) to search for quasi-periodic oscillations (QPO), previously reported in its high state. The source was observed monthly in a series of nine observations. Analysis of the temporal variations shows no evidence for QPO or other periodic changes, but correlations between the high-energy light curve and hardness of the spectrum are described. Spectral fits with two-component models demonstrate that the hardness variations come from changes in the intensity of the high-energy power-law tail., Comment: 10 pages plus figures; to appear in Astronomical Journal

This paper concludes a series of three papers presenting ROSAT High-Resolution Imager (HRI) observations of unidentified Einstein and serendipitous ROSAT X-ray sources in the direction of the Magellanic Clouds. Accurate positions and fluxes have been measured for these sources. Optical photometry and spectroscopy were obtained to search for identifications in order to determine the physical nature of these sources. The present paper includes new data for 24 objects; identifications are given or confirmed for 30 sources. For six sources optical finding charts showing the X-ray positions are provided. The results from this program are summarized, showing the populations of luminous X-ray sources in the Magellanic Clouds are quite different from those in the Galaxy., Comment: 28 pages, 2 figures; to appear in Astronomical Journal

We present and discuss 25 spectra obtained in November 1996, covering all phases of the CAL 87 binary system. These spectra are superior both in signal-to-noise and wavelength coverage to previously published data so that additional spectral features can be measured. Photometry obtained on the same nights is used to confirm the ephemeris and to compare with light curves from previous years. Analysis of the color variation through the orbital cycle has been carried out using archival MACHO data. When a barely resolved red field star is accounted for, there is no (V-R)-color variation, even through eclipse. There have been substantial changes in the depth of minimum light since 1988; it has decreased more than 0.5 mag in the last several years. The spectral features and radial velocities are also found to vary not only through the 0.44-day orbit but also over timescales of a year or more. Possible interpretations of these long-term changes are discussed. The 1996 spectra contain phase-modulated Balmer absorption lines not previously seen, apparently arising in gas flowing from the region of the compact star. The changes in emission-line strengths with orbital phase indicate there are azimuthal variations in the accretion disk structures. Radial velocities of several lines give different amplitudes and phasing, making determination of the stellar masses difficult. All solutions for the stellar masses indicate that the companion star is considerably less massive than the degenerate star. The Balmer absorption-line velocities correspond to masses of ~1.4Msun for the degenerate star and ~0.4Msun for the mass donor. However, the strong He II emission lines indicate a much more massive accreting star, with Mx>4Msun., Comment: 18 pages including tables, plus10 figures. To appear in ApJ

A comparison is made between the properties of CAL 83, CAL 87, RX J0513.9-6951, 1E 0035.4-7230 (SMC 13), RX J0019.8+2156, and RX J0925.7-4758, all supersoft X-ray binaries. Spectra with the same resolution and wavelength coverage of these systems are compared and contrasted. Some new photometry is also presented. The equivalent widths of the principal emission lines of H and He II differ by more than an order of magnitude among these sources, although those of the highest ionization lines (e.g. O VI) are very similar. In individual systems, the velocity curves derived from various ions often differ in phasing and amplitude, but those whose phasing is consistent with the light curves (implying the lines are formed near the compact star) give masses of $\sim 1.2M_{\odot}$ and $\sim 0.5M_{\odot}$ for the degenerate and mass-losing stars, respectively. This finding is in conflict with currently prevailing theoretical models for supersoft binaries. The three highest luminosity sources show evidence of "jet" outflows, with velocities of $\sim 1-4 \times10^3 km/s$. In CAL 83 the shape of the He II 4686\AA profile continues to show evidence that these jets may precess with a period of $\sim 69$ days., Comment: 27 pages including 5 tables, plus 6 figures. To appear in ApJ

Data are given for 16 extragalactic objects (predominantly AGN) behind the Magellanic Clouds and for 146 quasar candidates behind the nearby galaxies NGC 45, 185, 253, 2366, 2403 and 6822, IC 1613, M31 and M33. The Magellanic Cloud objects were identified by their X-ray emission, and precise optical and X-ray positions and optical photometry and spectra are presented for all of these. The quasar candidates surrounding the other nearby galaxies were identified through a CFHT slitless spectral survey. Although redshifts for only eight of these candidates have been obtained, previous observations indicate that the majority are likely to be quasars. A subsample of 49 of the brighter objects could confidently be used, in addition to the Magellanic Cloud sources, as probes of the gas in nearby galaxies for rotation curve studies, for studies of their halos, for comparison with higher redshift QSO absorption lines, or as references for proper motion studies., Comment: 10 pages of text and 3 plain Tex tables. Figures and full text are available at http://www.hia.nrc.ca/DAO/SCIENCE/science.html . To be published in AJ, Dec, 1997

Details of simultaneous photometric and spectroscopic observations of the optical counterpart of the `supersoft' X-ray source 1E 0035.4-7230 (SMC 13) are presented. Although the spectrum is dominated by emission lines of He II, the Balmer series of hydrogen is also present in emission with a strong decrement, and Balmer lines are seen as broad absorptions. Several high ionization emission features are also present including O VI (3811, 3834, and 5290A). Radial velocities and photometry confirm that the binary period is ~0.1719d, and an improved value of the period is derived from four years of photometry and analysis of ROSAT-HRI X-ray data. The orbital light variation is primarily due to an eclipse of the extensive accretion disk. X-ray and optical minima occur together. The UBV light curves are similar to each other, and no clear phase-related color variations are found. He II emission-line velocities show a semi-amplitude of K ~100 km/s, and maximum velocity occurs when the light curve indicates the compact star would be moving away from the observer, suggesting this emitting region may trace the orbital motion of the compact star. The range of possible masses implied for the X-ray source lies between 0.5 and 1.5 solar masses if the mass donor is a main sequence star filling its Roche lobe. The light curve suggests values at the high end of this range. The broad H absorption lines appear to have a much larger velocity amplitude and lower systemic velocity, making it difficult to understand their origin. We discuss possible models for the system., Comment: uuencoded compressed file with 15 pages + 1 table and 6 postscript figures. Accepted by Ap J. Also available at http://www.hia.nrc.ca/eprints.html

Data are given for 16 extragalactic objects (predominantly AGN) behind the Magellanic Clouds and for 146 quasar candidates behind the nearby galaxies NGC 45, 185, 253, 2366, 2403 and 6822, IC 1613, M31 and M33. The Magellanic Cloud objects were identified by their X-ray emission, and precise optical and X-ray positions and optical photometry and spectra are presented for all of these. The quasar candidates surrounding the other nearby galaxies were identified through a CFHT slitless spectral survey. Although redshifts for only eight of these candidates have been obtained, previous observations indicate that the majority are likely to be quasars. A subsample of 49 of the brighter objects could confidently be used, in addition to the Magellanic Cloud sources, as probes of the gas in nearby galaxies for rotation curve studies, for studies of their halos, for comparison with higher redshift QSO absorption lines, or as references for proper motion studies., Comment: 10 pages of text and 3 plain Tex tables. Figures and full text are available at http://www.hia.nrc.ca/DAO/SCIENCE/science.html . To be published in AJ, Dec, 1997

Details of simultaneous photometric and spectroscopic observations of the optical counterpart of the `supersoft' X-ray source 1E 0035.4-7230 (SMC 13) are presented. Although the spectrum is dominated by emission lines of He II, the Balmer series of hydrogen is also present in emission with a strong decrement, and Balmer lines are seen as broad absorptions. Several high ionization emission features are also present including O VI (3811, 3834, and 5290A). Radial velocities and photometry confirm that the binary period is ~0.1719d, and an improved value of the period is derived from four years of photometry and analysis of ROSAT-HRI X-ray data. The orbital light variation is primarily due to an eclipse of the extensive accretion disk. X-ray and optical minima occur together. The UBV light curves are similar to each other, and no clear phase-related color variations are found. He II emission-line velocities show a semi-amplitude of K ~100 km/s, and maximum velocity occurs when the light curve indicates the compact star would be moving away from the observer, suggesting this emitting region may trace the orbital motion of the compact star. The range of possible masses implied for the X-ray source lies between 0.5 and 1.5 solar masses if the mass donor is a main sequence star filling its Roche lobe. The light curve suggests values at the high end of this range. The broad H absorption lines appear to have a much larger velocity amplitude and lower systemic velocity, making it difficult to understand their origin. We discuss possible models for the system., Comment: uuencoded compressed file with 15 pages + 1 table and 6 postscript figures. Accepted by Ap J. Also available at http://www.hia.nrc.ca/eprints.html

Photometric observations of the supersoft X-ray source 1E 0035.4-7230 obtained during two years reveal that the very blue optical counterpart (V (maximum)=20.2, B-V=-0.15, U-B=-1.06) undergoes nearly sinusoidal variations with a period of 0.1719256 days and an amplitude of Delta V~0.3 mag. ROSAT observations show the X-rays vary with approximately the same period. However, either the X-ray minimum precedes the optical minimum by about a quarter cycle or there is a small period difference between the two wavelength regions. We consider that this X-ray source is a close binary, with the optical light coming primarily from an accretion disk surrounding the compact star. Optical spectra show weak, variable He II (4686 Angstrom) emission which probably originates in this disk. Possible interpretations of the light curve are discussed, including X-ray heating of the secondary star. The very broad minimum in the X-ray light curve suggests the X-rays may be scattered in a large accretion disk corona (ADC) which is partially occulted, probably by an azimuthally irregular bulge on the disk rim. If this system lies at the distance of the Small Magellanic Cloud, it radiates near the Eddington luminosity., Comment: 10 pages, 1 table and 3 (of 4) figures as uuencoded compressed Postscript. Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.html

A detailed analysis of simultaneous photometric and spectroscopic observations of the optical counterpart of the LMC "supersoft" X-ray source RX J0513.9-6951 (identified with HV 5682) is presented. The spectrum is dominated by He II emission lines and H + He II blends; no He I is observed but several higher ionization emission features, especially O VI (3811, 3834, and 5290A) are prominent. Radial velocity measurements suggest a binary period of 0.76 days. If the small velocity amplitude, K~11 km/s, is interpreted as orbital motion, this implies that the binary system contains a somewhat evolved star plus a relatively massive compact object, viewed nearly pole-on. No orbital photometric variations were found, although irregular brightness changes of ~0.3 mag occurred. Unusual emission lines are observed which cannot be identified except as high velocity (4000 km/s) bipolar outflows or jets. These outflows are seen in H and He II at the same positive and negative velocities. They were relatively stable for periods of ~5 days, but their velocities appear to have been ~250 km/s smaller in 1992 than in 1993 or 1994., Comment: uuencoded compressed postscript, 19 pages including 4 tables. Figures available from authors. Also available at http://www.dao.nrc/DAO/SCIENCE/ . Accepted for publication in ApJ

Photometric observations of the supersoft X-ray source 1E 0035.4-7230 obtained during two years reveal that the very blue optical counterpart (V (maximum)=20.2, B-V=-0.15, U-B=-1.06) undergoes nearly sinusoidal variations with a period of 0.1719256 days and an amplitude of Delta V~0.3 mag. ROSAT observations show the X-rays vary with approximately the same period. However, either the X-ray minimum precedes the optical minimum by about a quarter cycle or there is a small period difference between the two wavelength regions. We consider that this X-ray source is a close binary, with the optical light coming primarily from an accretion disk surrounding the compact star. Optical spectra show weak, variable He II (4686 Angstrom) emission which probably originates in this disk. Possible interpretations of the light curve are discussed, including X-ray heating of the secondary star. The very broad minimum in the X-ray light curve suggests the X-rays may be scattered in a large accretion disk corona (ADC) which is partially occulted, probably by an azimuthally irregular bulge on the disk rim. If this system lies at the distance of the Small Magellanic Cloud, it radiates near the Eddington luminosity., Comment: 10 pages, 1 table and 3 (of 4) figures as uuencoded compressed Postscript. Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.html

A detailed analysis of simultaneous photometric and spectroscopic observations of the optical counterpart of the LMC "supersoft" X-ray source RX J0513.9-6951 (identified with HV 5682) is presented. The spectrum is dominated by He II emission lines and H + He II blends; no He I is observed but several higher ionization emission features, especially O VI (3811, 3834, and 5290A) are prominent. Radial velocity measurements suggest a binary period of 0.76 days. If the small velocity amplitude, K~11 km/s, is interpreted as orbital motion, this implies that the binary system contains a somewhat evolved star plus a relatively massive compact object, viewed nearly pole-on. No orbital photometric variations were found, although irregular brightness changes of ~0.3 mag occurred. Unusual emission lines are observed which cannot be identified except as high velocity (4000 km/s) bipolar outflows or jets. These outflows are seen in H and He II at the same positive and negative velocities. They were relatively stable for periods of ~5 days, but their velocities appear to have been ~250 km/s smaller in 1992 than in 1993 or 1994., Comment: uuencoded compressed postscript, 19 pages including 4 tables. Figures available from authors. Also available at http://www.dao.nrc/DAO/SCIENCE/ . Accepted for publication in ApJ