Orbital Ephemeris Research Articles

Mass outflow from the X-ray binary X2127 + 119 in M15

The bright X-ray binary X2127 + 119 in the core of the globular cluster M15 has long been thought to be in an unusual evolutionary state, in which the binary is embedded in a common envelope. Support for this idea comes from the absorption lines of X2127 + 119, which are blueshifted at all orbital phases, indicating the existence of outflows from the system. A common-envelope scenario implies that the absorption lines should exhibit maximum blueshift near mid-eclipse (binary phase 0.0). We have re-analysed Isaac Newton Telescope spectra of X2127 + 119 obtained in 1986, 1987 and 1988 using the latest orbital ephemeris (substantially different from that used in the original analysis), and find that the orbital phase at which the absorption lines show a maximum blueshift is not 0.0, but rather 0.25-0.3. These results indicate that a common-envelope scenario for X2127 + 119 may not work. In addition, from spectrograms of the He II λ4686 line, we report the first tentative detection of the companion star of X2127 + 119.

PX Andromedae: Superhumps and variable eclipse depth

Results of a photometric study of the SW Sex novalike PX And are presented. The periodogram analysis of the observations obtained in October 2000 reveals the presence of three signals with periods of 0: 142, 4: d 8a nd 0: d 207. The first two periods are recognized as negative superhumps and the corresponding retrograde precession period of the accretion disk. The origin of the third periodic signal remains unknown. The observations in September-October 2001 point only to the presence of negative superhumps and possibly to the precession period. The origin of the negative superhumps is discussed and two possible mechanisms are suggested. All light curves show strong flickering activity and power spectra with a typical red noise shape. PX And shows eclipses with highly variable shape and depth. The analysis suggests that the eclipse depth is modulated with the precession period and two possible explanations of this phenomenon are discussed. An improved orbital ephemeris is also determined: Tmin(HJD)= 49238:83662(14)+ 0: d 146352739(11)E.

A New Orbital Ephemeris and Reinterpretation of Spectroscopic Data for the Supersoft X-Ray Binary RX J0513.9−6951

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 and low optical states and its long-term light curve. Evidence for an 83.3 day periodicity in the photometry is presented.

A multiwavelength timing analysis of the eclipsing polar DP Leo

We present an analysis of the X-ray light curves of the magnetic cataclysmic variable DP Leo using recently per- formed XMM Newton EPIC and archival published and unpublished ROSAT PSPC observations. We combine the timings of the X-ray eclipses with timings derived from archival HST-observations and new optical observations with the photon counting OPTIMA camera. We determine the eclipse length at X-ray wavelengths to be 235 5 s, slightly longer than at ultra-violet wavelengths, where it lasts 225 s. A new orbital ephemeris is derived which connects the more than 120 000 binary cycles covered since 1979. It has a highly significant quadratic term, implying an orbital period change of ˙ P = 4:4 10 12 ss 1 , two orders of magnitude larger than being compatible with braking by gravitational radiation only. Over the last twenty years, the optical and X-ray bright phases display a continuous shift with respect to the eclipse center by2:1 yr 1 .O ver the last 8.5 years the shift of the X-ray bright phase is2:5 yr 1 . We interpret this as evidence of an asynchronously rotating white dwarf although synchronization oscillations cannot be ruled out completely. If the observed phase shift continues, a funda- mental rearrangement of the accretion geometry must occur on a time-scale of some ten years. Applying model atmosphere spectra to optical/UV eclipse light curves, we determine the temperature and mass of the white dwarf, the temperature and size of the optical/UV emitting spot and the distance to DP Leo to be Twd = 13 500 K, Mwd ' 0:6 M, Tspot = 32 000 K, Aspot ' 0:1 Awd ,a ndD= 400 pc, respectively. The implied inclination and mass ratio are i= 79:5 and Q= Mwd=M2 = 6:7. DP Leo is marginally detected at eclipse phase in X-rays. The upper limit eclipse flux is consistent with an origin on the late-type secondary, LX' 2:5 10 29 ergs s 1 (0.20 7.55 keV), at a distance of 400 pc.

The Mass Donor of Scorpius X‐1 Revealed

We present the first detection of the mass donor star in the prototype X-ray binary Scorpius X-1. Phase resolved spectroscopy revealed narrow emission lines components from the irradiated secondary star. Radial velocity fits to the Bowen blend emission are used to establish an absolute orbital ephemeris and derive an accurate value for the systemic velocity; gamma= -113.8 +/- 0.6 km/s. Emission from the irradiated front side of the secondary leads to solid limits to the radial velocity of the mass donor of 87 < K_2 < 148 km/s. In conjunction with an upper limit to the velocity of the primary K_1 < 53 km/s, we derive a firm limit on the mass ratio of Sco X-1 of q < 0.61. % A likely set of system parameters satisfying the various constraints as well as the recent inclination estimate by Fomalont et al. (2001) is K_1=40 km/s, K_2=133 km/s, q=0.30 corresponding to component masses of M_1=1.4M_sun, M_2=0.42 M_sun for an orbital inclination of 38 degrees.

Simultaneous Photometry and Spectroscopy of the Supersoft X-Ray Source RX J0019.8+2156 (QR Andromedae)

Simultaneous optical photometry and spectroscopy of QR Andromedae (RX J0019.8+2156) obtained in 1995 are reported. The V light curve shows a range of ∼0.5 mag through the 15.85 hr orbital period, with shorter term (∼1.8 hr) variations superposed. There is no clear indication of any color change through the orbit. The spectra show strong emission lines, principally due to He II, which vary in both velocity and strength throughout the orbit. Violet-displaced H absorption lines are present during about half the orbital cycle. Emission lines of O VI (λ3811, λ3834) are clearly present. Two higher dispersion spectra also reveal emission lines of O V, C III, C IV, N III, N V, [Fe X], and [Fe XIV]. A few moderate-strength emission lines remain unidentified. Analysis of the radial velocity variations and light curve show the donor star to be a very low mass object (0.3–0.5 M⊙), assuming the compact star's mass lies below ∼1.5 M⊙. A search for spectral variations associated with the short-term photometric flickering reveals no obvious correlations, but our spectra have rather low resolution and signal-to-noise ratio. Supplemental photometry taken in 2000 July allows us to derive an improved orbital ephemeris for the system.

BeppoSAX observation of the eclipsing dipping X-ray binary X 1658-298

Results of a 2000 August 12{13 BeppoSAX observation of the 7.1 hr eclipsing, dipping, bursting, transient, low-mass X-ray binary (LMXRB) X 1658-298 are presented. The spectrum outside of eclipses, dips and bursts can be modeled by the combination of a soft disk-blackbody and a harder Comptonized component with a small amount (1:3 10 21 atom cm 2 ) of low-energy absorption. In contrast, an RXTE observation 18 months earlier during the same outburst, measured an absorption of 5:0 10 22 atom cm 2 . Such a change is consistent with a thinning of the accretion disk as the outburst progresses. Structured residuals from the best-t spectral model are present which are tentatively identied with Ne-K/Fe-L and Fe-K shell emission. The spectral changes during dips are complex and may be modeled by a strong (3 10 23 atom cm 2 ) increase in absorption of the Comptonized component only, together with reductions in normalizations of both spectral components. This behavior is in contrast to the \complex continuum model for X-ray dip sources, where the softer blackbody component rapidly suers strong absorption. It is however, similar to that found during recent XMM-Newton observations of the eclipsing, dipping, LMXRB EXO 0748-676. An updated orbital ephemeris is provided which does not require a quadratic term, in contrast to that of Wachter et al. (2000).

The soft X-ray eclipses of HU Aqr

We present the results of extended monitoring observations in soft X-rays of the bright eclipsing polar (AM Herculis star) HU Aqr. It was observed between 1990 and 1998 by ROSAT for a total of 230 ksec using the PSPC and the HRI detectors and by EUVE with the Deep Survey Imager and the Spectrometer for a total of 580 ksec. The overall X-ray brightness of HU Aqr varied due to changes of the mass accretion rate by a factor of 40 over that period of time. At all occasions the X-ray light curve was characterized by a marked on-o behavior due to the self-eclipse of the accreting pole. The X-ray light curve showed eclipses by the companion star, the accretion stream and by an accretion curtain raised between the two stars in the binary. Narrow dips prior to the stellar eclipse are caused by the transit of the outer accretion stream. These dips display marked phase shifts, thus indicating a large movement of the threading region, where the stream couples to the magnetic eld. These shifts are shown to be related to changes of the mass accretion rate. Correspondingly, the spot longitude varied between 34 and 50. The X-ray light curves display clear evidence for the presence of an accretion curtain, which is raised all along the ballistic accretion stream down to the region where the bulk of matter couples onto magnetic eld lines. A lower limit to the mass accretion rate in the curtain is 6 10 12 M/yr, which is of order 10% of the total mass accretion rate. A linear t to all available eclipse egress times yields an updated orbital ephemeris of the system: BJED(T0) = 2449217:345872(35) +E 0:086820416195(47) with T0 the time of eclipse of the white dwarf centre of mass (BJED: barycentric Julian ephemeris time). The inclusion of a quadratic term gives a better t to the data but is not regarded as indication of a period change or asynchronous rotation but by a migration of the accretion spot over the surface of the white dwarf. For one particular data set obtained in a high accretion state, detailed light curve modeling was possible. The egress from eclipse lasted 1.3 s, which constrained the azimuthal extent of the accretion spot to less than 4 or 450 km. The spot extended vertically by0.015 Rwd. A comparison of the width of the stream dip and the extent of the accretion spot shows, that only the inner 60{80% of the stream are dense enough to re the soft X-ray engine. During the eclipse, HU Aqr was detected at a flux level of 6 10 14 erg cm 1 s 1 . The implied X-ray luminosity is LX =2 :2 10 29 erg s 1 , comparable with X-ray emission

Doppler Tomography of the Emission-Line Flickering in Cataclysmic Variables

Time-resolved, optical spectrophotometric observations of the Hα emission line in the cataclysmic variable V442 Oph are presented, and a long-term orbital ephemeris is derived. A method designed to quantify and locate the line-flickering activity in accretion disks is proposed on the basis of Doppler tomography techniques, and the line profile variability is explored. We found that the stochastic emission-line fluctuations in this system are the result of flaring activity at specific locations in the accretion disk. Such activity seems to be inhibited or damped for intrinsic gas velocities below 250 km s-1.

The Ephemeris and Dipping Spectral Behavior of 4U 1624−49

We present striking results from Rossi X-Ray Timing Explorer (RXTE) observations of the 21 hr low-mass X-ray binary 4U 1624-49, showing five complex dips in unprecedented detail. For the first time, dipping is detected up to 15 keV. Prominent flares are also observed in the light curves, limited to energies above ~8 keV. Spectra selected by intensity during dip episodes can be well fitted with a two-component model consisting of a pointlike blackbody from the neutron star and progressive covering of an extended Comptonized region, presumably an accretion disk corona (ADC), corrected for photons scattered into and out of the X-ray beam by a interstellar dust halo. We find that the outer regions of the absorber are highly ionized and that electron scattering is totally responsible for the X-ray attenuation during shallow dipping. The timescales of dip ingress and egress indicate that the envelope of material absorbing the ADC has smaller angular size than the ADC itself and that the ADC is likely limited to a height-to-radius ratio of 10% rather than being spherical in extent. In addition, we have analyzed ~4.5 yr of RXTE All-Sky Monitor (ASM) coverage to derive the first accurate orbital ephemeris for 4U 1624-49, with phase zero (the time of dip centers) well described by the relation 2,450,088.63918(69) + N×0. 869907(12) (JD).

Observation of ultra low hard X-ray flux from Cyg X-1 —A possible partial occulation of the X-ray source

The black hole candidate Cyg X-1 was observed in ultra low state on march 30, 1997 using Large Area Scintillation counter Experiment (LASE) in the hard X-ray energy region of 20–180 keV. During the 30 minute exposure a combined signal of 68 sigma was obtained, however, the measured flux at 50 keV was lower by a factor of 2 than the minimum flux reported so far. Using the recent orbital ephemeris of the source, our snap-shot observations were made at ϕ5.6 = 0.915, which corresponds to the binary minimum revealed by the ASM light curves. The daily average data from the BATSE detectors give the source intensity level to be higher by a factor of 5. Very low flux values measured in the present experiment suggest that the hard X-ray source may have been partially occulted by the primary companion during its transit near the X-ray minimum.

A TiO study of the black hole binary GRO J0422+32 in a very low state

We present 53 simultaneous photometric (I band) and spectroscopic (6900–9500 A) observations of GRO J0422+32, taken during 1997 December. From these we determine that J0422+32 was in its lowest state yet observed, at I=20.44±0.08. Using relative spectrophotometry, we show that it is possible to correct very accurately for telluric absorption. Following this, we use the TiO bands at 7055 and 7589 A for a radial velocity study and thereby obtain a semi-amplitude of 378±16 km s −1 , which yields f(M)=1.191±0.021 M ⊙ and consistent with previous observations. We further demonstrate that this little-explored method is very powerful for such systems. We also determine a new orbital ephemeris of HJD=245 0274.4156±0.0009+0.212 1600±0.000 0002E.We see some evidence for an ellipsoidal modulation, from which we determine the orbital inclination of J0422+32 to be less than 45°. We therefore calculate a minimum mass for the primary of 2.22 M ⊙ , consistent with a black hole, but not necessarily the supermassive one proposed recently (1997) by Beekman et al. We obtain an M4–5 spectral type for the secondary star, and determine that the secondary contributes 38±2 per cent of the flux that we observe from J0422+32 over the range 6950–8400 A. From this we calculate the distance to the system to be 1.39±0.15 kpc.

UBV photometry, UV spectroscopy and radio observations of the peculiar binary V Sagittae

We have performed high-speed UBV photometric observations on the peculiar binary V Sagittae. Using three new eclipse timings we update the orbital ephemeris and convert it to a dynamical time-scale (TDB). We also searched for quasi-periodic oscillations but did not detect them. Using the Wilson–Devinney algorithm we have modelled the light curve to find the stellar parameters of V Sge. We find that the system is a detached binary but that the primary star is very close to filling its Roche lobe, while the secondary star fills 90 per cent of its Roche lobe volume. We find temperatures of the primary and the secondary star to be T1=41 000 K and T2=22 000 K. We find i=72° and masses of 0.8 M⊙ and 3.3 M⊙ for the primary and secondary stars respectively. De-archived Hubble Space Telescope (HST) spectroscopy of V Sge shows evidence of mass loss via a wind or winds. In addition we report radio observations of V Sge during an optical high state at 2 cm, 3.6 cm and 6 cm wavelengths. The 3.6 cm emission is increased by a factor of more than six compared with an earlier detection in a previous optical high state.

Accretion in the High‐Field Magnetic Cataclysmic Variable AR Ursae Majoris

AR UMa is the highest field example known of the magnetic cataclysmic variables, with a polar field Bp = 230 MG. We report here the results of a long program of photometry, spectroscopy, and spectropolarimetry of the object that was undertaken with the aim of gaining a better understanding of the role that the white dwarf field plays in shaping the properties of the magnetic systems. Only three accretion episodes, reaching mV ≤ 15 and covering a total of 9 months, were detected during the 4 yr of available photometry. Fortunately, the onset of one episode coincided with a week-long observing run, resulting in spectrophotometry and linear and circular spectropolarimetry that document the event. The long intervals of quiescence have enabled a determination of the orbital ephemeris that is now sufficiently precise to phase observations 20 yr old. The high-state observations lead to a number of conclusions regarding the system geometry. The white dwarf magnetic axis is inclined rather little to the spin axis, but the dipole is twisted in azimuth such that it lies nearly perpendicular to the stellar line of centers. Tomographic analysis of a wide variety of atomic species indicates that the white dwarf likely accretes in twin funnels that split off a ballistic gas stream reaching 30%-50% of the distance between the stars. A narrow high-velocity (KNHV ≈ 700 km s-1) emission-line component offset in phase from the main features suggests the existence of an additional gas stream, but the interpretation of this is not yet resolved. The system is viewed from a moderate inclination, which places the disfavored (retrograde) magnetic pole on the observed hemisphere at all times. We have investigated the possible effect that the white dwarf magnetosphere might have in restricting mass flow through L1, and therefore in giving rise to the unique, protracted low-accretion states of this object. However, the mechanisms considered are too weak and/or would give rise to consequences that are at odds with low-state observations. At the same time, the high magnetic field in AR UMa has yielded a new, powerful observational tool: phase-resolved Zeeman spectroscopy of the emission lines produced in the accretion stream(s). Future high-quality observations and sophisticated modeling of these features hold promise for three-dimensional reconstructions of the gas flow in high-field magnetic variables.

An eclipse of the X-ray flux from the dwarf nova OY Carinae in quiescence

We present a phase-resolved ROSAT HRI X-ray light curve of the dwarf nova OY Car in quiescence. The X-ray flux is eclipsed at the same time as the optical eclipse of the primary, and the region of X -ray emission is comparable in size to the white dwarf. We use subsequent optical observations to update the orbital ephemeris of the system.

1982-1988 Photometry of the Totally Eclipsing Chromospherically Active Binary V792 Herculis=HD 155638

view Abstract Citations (6) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS 1982-1988 Photometry of the Totally Eclipsing Chromospherically Active Binary V792 Herculis=HD 155638 Kaye, A. B. ; Hall, D. S. ; Patterson, L. R. ; Nations, H. D. ; Heckert, P. A. ; Summers, D. L. Abstract We present 1985-1988 UBV and VRI photometry obtained at three different observatories and analyze it along with previously published 1982-1984 UBV photometry. New times of midprimary eclipse along with previously published times yield the improved orbital ephemeris T(pri.min.)=JD 2446674.185 (±0.007) +27d53707(±0d.00026)n. Periodogram analysis of previously published radial velocities, for both the K giant and the F subgiant, yields orbital ephemeris constants consistent with the one above, but of lesser precision. Fitting the seven years of photometry with a cos(2θ) curve, after removing the eclipse points, yields 0m.021±0m.006 for the full amplitude of the ellipticity effect in V. Residuals from that cos(2θ) fit give light curves which reveal continuing starspot variability, which had been seen in the 1982-1984 photometry. These residuals, in ten data groups, are analyzed with a two-spot light-curve fitting procedure. Six long-lived spots are identified, the largest producing a light loss of 0m.166 in V. Lifetimes were >2.85, 0.81, 1.88, 1.84, >0.58, and >0.45 yr. Rotation periods for these six spots have a mean of 27d.36±0d.06, thus confirming synchronous rotation, and a range which indicates a differential rotation coefficient of k=0.031. With respect to the value of 0.65 below which strong dynamo action is expected in a convective star, the Rossby number for the K giant, believed to be the spotted star, is 0.17, well below the threshold and so large starspots are expected. Publication: The Astronomical Journal Pub Date: March 1996 DOI: 10.1086/117877 Bibcode: 1996AJ....111.1322K Keywords: STARS: INDIVIDUAL: HD 155638; BINARIES: ECLIPSING full text sources ADS | data products SIMBAD (1)

IUE SPECTROSCOPY OF THE NOVA-LIKE VARIABLE BZ CAM: CHARACTERISTICS OF ITS PECULIAR WIND OUTFLOW

ABSTRACT We have analyzed 15 IUE low resolution SWP spectra of the peculiar hot nova-like object BZ Camelopardalis (= 0623+71), which is associated with a bow shock nebula. We determined approximate relative orbital phases of a series of spectra obtained continuously over a 28 hour time baseline by using the newly determined orbital period (P=0.1535 days) and ephemeris by Thorstensen et al. (1993). We find evidence of deepest absorption of the resonance doublet wind features C IV, Si IV, and N V near relative phase 0.2. In general, when the P Cygni resonance line absorption vanishes (strengthens), the Si IV emission strengthens (vanishes). We report dramatic temporal line profile variability of the C IV P Cygni feature and other strong wind absorptions at N V (1240), Si IV (1400), He II (1640) and N IV (1718), around the orbit, on timescales < 1 hour. The average terminal (blue edge) velocities (over 15 spectra) of the C IV and Si IV P Cygni features are -5300 and -5100 km s-1, respectively, while for higher temperature ion species (N V and He II), it is only -3900 and -3158 km s-1, respectively. Implications of the wind characteristics for the nature of its outflow, the origin of the bow-shaped nebula and the evolutionary status of BZ Cam are briefly discussed.

Geometric correction and radiometric normalisation of NOAA AVHRR data for fisheries applications

Abstract Sea surface temperature (SST) has been found useful for locating potential fishing grounds (PFGs). Thermal data of the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR) was acquired using a microcomputer (PC/AT 486) based Direct Reception and Processing Terminal (DRPT) developed in-house to map surface thermal fronts. Geometric correction using orbital ephemeris and ground control points (GCPs) resulted in locational accuracy of 1·73 km by 2·1 km. Besides, the corrections for artificially lowering SST in case of passes with large satellite zenith angles (LSZA) through a radiance normalization based on the mean vectors and dispersion matrices to make it comparable with small satellite zenith angle (SSZA) pass is presented in this letter.

A spectroscopic and photometric study of 12 BM Camelopardalis

Radial velocities from 1916.95 to 1991.95 and photometry from l979.25, both published and new in this paper, are presented and analyzed. A new solution of the radial velocity curve reveals a new period of 80.90 days and an eccentricity of e = 0.05 +/- 0.02, both very different from the 80.17 days and 0.35 found by Abt et al. (1969). An alternative solution with e = 0 is given because we cannot decide firmly whether or not the small eccentricity is real. We find V sin i = 11.3 +/- 0.3 km/s from Maidanak and 10 unequal depth. 0.048 mins and 0.026 mins. The orbital ephemeris for conjunction (K gisnt behind) is JD(hel.) 2,448,111.1 (+/- 0.4 days ) + 80.898 days (+/- 0.004 days ) E, consistent with both the radial velocities and the photometry. With the ellipticity effect removed, the light curve shows residual variability which we fit with a two-spot model. During the 13 years covered by photometry there were nine different starspots, the largest one producing a light loss of 0.19 mins. Rotation periods for the nine spots ranged from 78.6 +/- 0.5 days to 83.7 +/- 0.4 days from which we concluded that the K giant does rotate synchronously but with a differential rotation coefficient of k = 0.06 +/- 0.01. Lifetimes for the nine spots ranged from 1.1 to greater than 4.2 yr and were consistent with the empirical spot lifetime laws of Hall & Henry (1994). Use of the mass function, the orbital period, the V sin i, the two different ellipticity effect amplitudes, and various logical constraints led to ranges of possible masses, radii and inclinations. The most believable solution was around i = 90 deg, R(sub 1) = 24 solar radii, M(sub 1) = 1.1 solar mass, and M(sub 2) = 0.6 solar mass. THe Rossby number for the K giant is 0.48, small enough compared to the critical value of 0.65 to explain why, though rotating 'slowly', it does have large spots.

Starspots found on the ellipsoidal variable V350 lacertae = HR 8575

It has been a puzzle why this chromospherically active, strong-dynamo K2 IV-III star is not known to have the large starspots characteristic of other such stars. Published individual radial velocities, which had never been analyzed, are used to derive an orbital solution. Combined with the one older existing orbital solution, this yields an improved orbital ephemeris: time of conjunction (K star behind) = JD 2445255.47 +/- 0.11 days and period = 17.75346 +/- 0.00016 days. All available photoelectric photometry, from 1970.9 to 1992.5, is collected A cos 2 theta fit of the ellipticity effect yields JD 2445255.60 +/- 0.06 days for a time of conjunction, 17.7523 +/- 0.0005 days for the period, and 0.084 mins for the peak-to-peak amplitude in V. With the ellipticity effect removed, the light curve does show measurable starspot variability in 15 of 16 data groups, the starspot wave amplitudes ranging between 0.03 mins and 0.08 mins. Ten starspots are identified and their rotation periods determined, the mean being 17.70 +/- 0.03 days (confirming synchronous rotation) and the range being Delta P/P = 0.017 +/- 0.006 (indicating differential rotation). There is a slow variation in mean brightness, almost 0.1 min in range and at least 2 decades in length.