UX Ursae Majoris Research Articles

Accretion-disc precession in UX Ursae Majoris

We report the results of a long campaign of time-series photometry on the nova-like variable UX Ursae Majoris during 2015. It spanned 150 nights, with ~1800 hours of coverage on 121 separate nights. The star was in its normal `high state' near magnitude V=13, with slow waves in the light curve and eclipses every 4.72 hours. Remarkably, the star also showed a nearly sinusoidal signal with a full amplitude of 0.44 mag and a period of 3.680 +/- 0.007 d. We interpret this as the signature of a retrograde precession (wobble) of the accretion disc. The same period is manifest as a +/-33 s wobble in the timings of mid-eclipse, indicating that the disc's centre of light moves with this period. The star also showed strong `negative superhumps' at frequencies w_orb+N and 2w_orb+N, where w_orb and N are respectively the orbital and precession frequencies. It is possible that these powerful signals have been present, unsuspected, throughout the more than 60 years of previous photometric studies.

Dark spot, spiral waves and the SW Sextantis behaviour: it is all about UX Ursae Majoris

We present an analysis of time-resolved, medium resolution optical spectroscopic observations of UX UMa in the blue (3920-5250 A) and red (6100-7200 A) wavelength ranges, that were obtained in April 1999 and March 2008 respectively. The observed characteristics of our spectra indicate that UX UMa has been in different states during those observations. The blue spectra are very complex. They are dominated by strong and broad single-peaked emission lines of hydrogen. The high-excitation lines of HeII 4686 and the Bowen blend are quite strong as well. All the lines consist of a mixture of absorption and emission components. Using Doppler tomography we have identified four distinct components of the system: the accretion disc, the secondary star, the bright spot from the gas stream/disc impact region, and the unique compact area of absorption in the accretion disc seen as a dark spot in the lower-left quadrant of the tomograms. In the red wavelength range, both the hydrogen (H_alpha) and neutral helium (HeI 6678 and HeI 7065) lines were observed in emission and both exhibited double-peaked profiles. Doppler tomography of these lines reveals spiral structure in the accretion disc, but in contrast to the blue wavelength range, there is no evidence for either the dark spot or the gas stream/disc impact region emission, while the emission from the secondary star is weak. During the observations in 1999, UX UMa showed many of the defining properties of the SW Sex stars. However, all these features almost completely disappeared in 2008. We have also estimated the radial velocity semi-amplitudes K_1 and K_2 and evaluated the system parameters of UX UMa. These estimates are inconsistent with previous values derived by means of analysis of WD eclipse features in the light curve in the different wavelength ranges.

AnXMM-Newtonobservation of the nova-like variable UX UMa: spatially and spectrally resolved two-component X-ray emission

In the optical and ultraviolet regions of the electromagnetic spectrum, UX Ursae Majoris is a deeply eclipsing cataclysmic variable. However, no soft X-ray eclipse was detected in ROSAT observations. We have obtained a 38 ksec XMM–Newton observation to constrain further the origin of the X-rays. The combination of spectral and timing information allows us to identify two components in the X-ray emission of the system. The soft component, dominant below photon energies of 2 keV, can be fitted with a multitemperature plasma model and is uneclipsed. The hard component, dominant above 3 keV, can be fitted with a kT∼ 5 keV plasma model and appears to be deeply eclipsed. We suggest that the most likely source of the hard X-ray emission in UX UMa, and other systems in high mass transfer states, is the boundary layer.

HST spatially resolved spectra of the accretion disc and gas stream of the nova-like variable UX Ursae Majoris

Time-resolved eclipse spectroscopy of the nova-like variable UX UMa obtained with the Hubble Space Telescope/Faint Object Spectrograph (HST/FOS) on 1994 August and November is analysed with eclipse mapping techniques to produce spatially resolved spectra of its accretion disk and gas stream as a function of distance from the disk centre. The inner accretion disk is characterized by a blue continuum filled with absorption bands and lines, which cross over to emission with increasing disk radius, similar to that reported at optical wavelengths. The comparison of spatially resolved spectra at different azimuths reveals a significant asymmetry in the disk emission at ultraviolet (UV) wavelengths, with the disk side closest to the secondary star showing pronounced absorption by an 'iron curtain' and a Balmer jump in absorption. These results suggest the existence of an absorbing ring of cold gas whose density and/or vertical scale increase with disk radius. The spectrum of the infalling gas stream is noticeably different from the disc spectrum at the same radius suggesting that gas overflows through the impact point at the disk rim and continues along the stream trajectory, producing distinct emission down to 0.1 R(sub LI). The spectrum of the uneclipsed light shows prominent emission lines of Lyalpha, N v lambda1241, SiIV Lambda 1400, C IV Lambda 1550, HeII Lambda 1640, and MgII Lambda 2800, and a UV continuum rising towards longer wavelengths. The Balmer jump appears clearly in emission indicating that the uneclipsed light has an important contribution from optically thin gas. The lines and optically thin continuum emission are most probably emitted in a vertically extended disk chromosphere + wind. The radial temperature profiles of the continuum maps are well described by a steady-state disc model in the inner and intermediate disk regions (R greater than or equal to 0.3R(sub LI) ). There is evidence of an increase in the mass accretion rate from August to November (from V = 10 (exp -8.3 +/-0.1) to 10(exp -8.1 +/- 0.1 solar mass yr(exp -1)), in accordance with the observed increase in brightness. Since the UX UMA disc seems to be in a high mass accretion, high-viscosity regime in both epochs, this result suggests that the mass transfer rate of UX UMA varies substantially (approximately equal to 50 per cent) on time-scales of a few months. It is suggested that the reason for the discrepancies between the prediction of the standard disk model and observations is not an inadequate treatment of radiative transfer in the disc atmosphere, but rather the presence of addition important sources of light in the system besides the accretion disk (e.g., optically thin contiuum emission from the disk wind and possible absorption by circumstellar cool gas).

HST spatially resolved spectra of the accretion disc and gas stream of the nova-like variable UX Ursae Majoris

Time-resolved eclipse spectroscopy of the nova-like variable UX UMa obtained with the HST/FOS on 1994 August and November is analysed with eclipse mapping techniques to produce spatially resolved spectra of its accretion disc and gas stream as a function of distance from the disc centre. The inner accretion disc is characterized by a blue continuum filled with absorption bands and lines, which cross over to emission with increasing disc radius, similar to that reported by Rutten et al. at optical wavelengths. The comparison of spatially resolved spectra at different azimuths reveals a significant asymmetry in the disc emission at ultraviolet (UV) wavelengths, with the disc side closest to the secondary star showing pronounced absorption by an ‘iron curtain’ and a Balmer jump in absorption. These results suggest the existence of an absorbing ring of cold gas whose density and/or vertical scale increase with disc radius. The spectrum of the infalling gas stream is noticeably different from the disc spectrum at the same radius suggesting that gas overflows through the impact point at the disc rim and continues along the stream trajectory, producing distinct emission down to 0.1 RL1. The spectrum of the uneclipsed light shows prominent emission lines of Lyα, N vλ 1241, Si ivλ 1400, C ivλ 1550, He iiλ 1640, and Mg iiλ 2800, and a UV continuum rising towards longer wavelengths. The Balmer jump appears clearly in emission indicating that the uneclipsed light has an important contribution from optically thin gas. The lines and optically thin continuum emission are most probably emitted in a vertically extended disc chromosphere + wind. The radial temperature profiles of the continuum maps are well described by a steady-state disc model in the inner and intermediate disc regions (R ≤ 0.3 RL1). There is evidence of an increase in the mass accretion rate from August to November (from M. = 10−8.3 ± 0.1 to 10−8.1 ± 0.1 M⊙ yr−1), in accordance with the observed increase in brightness. Since the UX UMa disc seems to be in a high mass accretion, high-viscosity regime in both epochs, this result suggests that the mass transfer rate of UX UMa varies substantially (≃ 50 per cent) on time-scales of a few months. It is suggested that the reason for the discrepancies between the prediction of the standard disc model and observations is not an inadequate treatment of radiative transfer in the disc atmosphere, but rather the presence of additional important sources of light in the system besides the accretion disc (e.g. optically thin continuum emission from the disc wind and possible absorption by circumstellar cool gas).

Recovery of 29 Second Oscillations inHubble Space TelescopeEclipse Observations of the Cataclysmic Variable UX Ursae Majoris

Low-amplitude (approximately 0.5%) 29 s oscillations have been detected in Hubble Space Telescope Faint Object Spectrograph eclipse observations of the nova-like cataclysmic variable UX UMa. These are the same dwarf nova-type oscillations that were originally discovered in this system in 1972. The 29 s oscillations are seen in one pair of eclipse sequences obtained with the FOS/PRISM in 1994 November but not in a similar pair obtained with the FOS/GI60L grating in August of the same year. The oscillations in the PRISM data are sinusoidal to within the small observational errors and undergo an approximately - 360' phase shift during eclipses (i.e., one cycle is lost). The amplitudes are highest at pre-eclipse orbital phases and exhibit a rather gradual eclipse whose shape is roughly similar to, although perhaps slightly narrower than, LTX UMa's overall light curve in the PRISM bandpass (2000-8000 A). Spectra of the oscillations have been constructed from pre-, mid, and post-eclipse data segments of the November observations. The spectra obtained from the out-of-eclipse segments are extremely blue, and only lower limits can be placed on the temperature of the source that dominates the modulated flux at these orbital phases. Lower limits derived from blackbody (stellar atmosphere) model fits to these data are >or equal to 95,000 K (> or equal to 85,000 K); the corresponding upper limits on the projected area of this source are all less than 2% of the white dwarf (WD) surface area. By contrast, oscillation spectra derived from mid- eclipse data segments are much redder. Fits to these spectra yield temperature estimates in the range 20,000 K approximately greater T and T approximately less than 30,000 K for both blackbody and stellar atmosphere models and corresponding projected areas of a few percent of the WD surface area. These estimates are subject to revision if the modulated emission is optically thin. We suggest that the ultimate source of the oscillations is a hot, compact region near disk center, but that a significant fraction of the observed, modulated flux is due to reprocessing of the light emitted by this source in the accretion disk atmosphere. The compact source is occulted at orbital phases near mid-eclipse, leaving only part of the more extended reprocessing region(s) to produce the weak oscillations that persist even at conjunction. The highly sinusoidal oscillation pulse shape does not permit the identification of the compact comonent in this model with emission produced by a rotating disturbance in the inner disk or in a classical, equatorial boundary layer. Instead, this component could arise in a bright spot on the surface of the WD, possibly associated with a magnetic pole. However, a standard intermediate polar model can also be ruled out since UX UMa's oscillation period has been seen to change on timescales much shorter than the minimum timescale required to spin up the WD by accretion torques. A model invoking magnetically controlled accretion onto differentially rotating WD surface layers may be viable, but needs more theoretical work.

Eclipse Mapping of the Accretion Disk Wind in the Cataclysmic Variable UX Ursae Majoris

We present the results of an effort to model recent HST eclipse observations of the C IV 1550 A resonance line in the high-inclination nova-like cataclysmic variable UX UMa. Assuming this line to be predominantly wind-formed, we are able to roughly reproduce the shapes and strengths of the observed line profiles (both away from and during eclipse) within the framework of a simple kinematic model in which the outflow is described as a rotating, biconical accretion disk wind. Our preferred model also matches most of the detailed behavior of different parts of the C IV line profile (blue wing, line center, and red wing) as a function of orbital phase. The most important result of our modeling is that it strongly suggests the presence of a high column (NH ~ 1023 cm-2), relatively dense (ne 4 × 1012 cm-3), and only slowly outflowing (vpoloidal vescape) transition region between the disk photosphere and the fast-moving wind. We also find that the outflow from UX UMa is probably only moderately collimated (the outer opening angle of our preferred model is θmax 65°). Finally, the rotational disturbance seen in the data is fitted reasonably well by our model, in which the rotational component of motion in the wind is fixed by conserving the specific angular momentum of the outflowing material. The implications of these results for dynamical models of disk-driven winds are discussed.

Hubble Space Telescope and R-Band Eclipse Maps of the UX Ursae Majoris Accretion Disk

view Abstract Citations (66) References (56) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hubble Space Telescope and R-Band Eclipse Maps of the UX Ursae Majoris Accretion Disk Baptista, R. ; Horne, Keith ; Hilditch, R. W. ; Mason, K. O. ; Drew, J. E. Abstract Hubble Space Telescope time-resolved spectroscopic and ground-based R-band photometric data of UX UMa during eclipse are presented and discussed. The spectroscopy covers the C IV λ1550 and He II λ1640 spectral regions. The eclipses in the UV continuum are deep, nearly reaching the zero level at mid-eclipse phases. Sharp ingress and egress features reveal the occultation of the white dwarf at disk center but there is no evidence of the orbital hump or of the bright spot. The steep ultraviolet eclipse light curves are used to estimate the radius of the white dwarf and to constrain the binary parameters. We find M1 = M2 = 0.47 Msun and i = 71°.0±0°.6. The white dwarf contributes with ≃25% of the light at λ1600 Å. If the inner disk is optically thick it has a temperature of Twd ≳ 65,000 K. Velocity-resolved light curves in the C IV λ1550 line show evidence of rotational disturbance and a strong orbital modulation is seen in the line center light curve. Maximum-entropy eclipse mapping techniques are used to solve for a map of the disk brightness distribution and for fluxes of an additional uneclipsed component in 18 narrow UV bands and in the R band. The angular scale of the disk and the distance to UX UMa are estimated from a color-magnitude diagram by a method similar to cluster main-sequence fitting. We find D = 345±34 pc. The radial temperature profiles derived from the UV continuum maps range from 8000 K in the outer disk regions to 30,000 K in the inner disk and reasonably follow the T ∝ R-¾ law for steady mass accretion at a rate of M = 10-8.0±0.2 Msun yr-1. The comparison of R-band eclipse maps from observations 2 months apart indicates changes in the structure of the outer disk which are probably due to small changes (≲20%) in the mass transfer rate from the secondary star. The maps in the C IV and He II line profiles are affected by emission from the disk wind. The radial temperature profiles of both line center maps show a flat slope. It is suggested that at low velocities the eclipsed part of the line emission arises from an opaque and extended region with a rather uniform spatial intensity distribution as projected in the plane of the sky. When plotted as a sequence of spatially resolved spectra these lines appear in absorption at disk center and change to emission in the outer disk regions besides showing large uneclipsed components. This behavior is similar to that found by Rutten et al. for the Balmer lines and suggests that these optical lines may also have a wind component. We obtain a revised ephemeris for the times of minimum and an upper limit for secular period changes of |Pdot| < 1.3 × 10-12 s s-1. The mass transfer rate inferred from this limit is an order of magnitude smaller than the value derived from the eclipse mapping, suggesting that the high mass transfer rate of UX UMa is not the consequence of its secular period decrease. Publication: The Astrophysical Journal Pub Date: July 1995 DOI: 10.1086/175970 Bibcode: 1995ApJ...448..395B Keywords: STARS: BINARIES: ECLIPSING; STARS: INDIVIDUAL CONSTELLATION NAME: UX URSAE MAJORIS; STARS: NOVAE; CATACLYSMIC VARIABLES; ULTRAVIOLET: STARS full text sources ADS | data products SIMBAD (3) MAST (1) ESA (1)

Spectrally resolved eclipse maps of the accretion disk in UX Ursae Majoris

ACCRETION disks play an important role in many astrophysical environments, such as active galactic nuclei, protostellar systems, X-ray binaries and cataclysmic variables. The lack of spatially resolved information, however, has meant that theoretical models for accretion disks are in general poorly constrained by observations. Here we use the shape of the light curves from an eclipsing cataclysmic variable, UX Ursae Majoris, to reconstruct the spectral energy distribution (in the range 3,600–10,000 A) across the face of an accretion disk. The spectral resolution is sufficient to reveal both the radial dependence of absorption and emission line features within the disk, and the spectral details of the bright spot formed at the point where the accretion stream from the secondary star collides with the disk. Such detailed reconstructions of accretion-disk spectra should help to bridge the gap between observations and theoretical models.

THE ORBITAL PERIOD CHANGES OF UX URSAE MAJORIS

ABSTRACT It is found that the orbital changes of the eclipsing cataclysmic variable UX Ursae Majoris are aperiodic. This eliminates apsidal motion and the revolution of the eclipsing system around a third body as feasible explanations of the period variations. An origin in the magnetism of the secondary appears possible, but the details are not clear.

An upper limit to the mass of the white dwarf in UX Ursae Majoris

Observations spectroscopiques resolues dans le temps de la variable de type nova UX UMa. On trouve des variations de vitesse radiale des raies d'emission Hα, avec une semi-amplitude de 157±6 km/s. Les resultats impliquent que la masse de la naine blanche du systeme soit inferieure a 0,7 M○.

Ultraviolet spectrum variability of UX Ursae Majoris

IUE spectra show UX Ursae Majoris to be a spectacular ultraviolet line spectrum variable on time scales of months. Time-resolved spectra around the orbit show that the continuum is strongly eclipsed, whereas the line emission is not. Features in the light curve which are identified with a hot spot are not prominent in the far-UV. The UV line emission probably originates in a wind.

Infrared and optical light curves of UX Ursae Majoris and U Geminorum

Infrared and optical light curves of UX Ursae Majoris and U Geminorum

Accretion disks in cataclysmic variables. I - The eclipse-related phase shifts in DQ Herculis and UX Ursae Majoris

view Abstract Citations (46) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Accretion disks in cataclysmic variables. I. The eclipse-related phase shifts in DQ Herculis and UX Ursae Majoris. Petterson, J. A. Abstract The paper describes a model for a cataclysmic-variable binary system in which a large accretion disk reflects radiation from a progradely rotating source on or near the white dwarf surface, thus reproducing rapid oscillations in the optical radiation. The model reproduces the phase shift and amplitude variations of the DQ Herculis oscillations during eclipse very well. The same model, with a progradely rotating source, also reproduces the completely different eclipse-related phase shift behavior of UX Ursae Majoris, when it is viewed at a somewhat smaller inclination angle (about 75 deg). Publication: The Astrophysical Journal Pub Date: October 1980 DOI: 10.1086/158337 Bibcode: 1980ApJ...241..247P Keywords: Eclipsing Binary Stars; Phase Shift; Stellar Mass Accretion; Variable Stars; Light (Visible Radiation); Novae; White Dwarf Stars; Astrophysics; Accretion Disks:Cataclysmic Variables; Cataclysmic Variables:Eclipsing Binaries; Cataclysmic Variables:Oscillations; Nova DQ Herculis; Nova Herculis 1934 full text sources ADS | data products SIMBAD (2)

ANOMALOUS PERIOD CHANGE OF UX URSAE MAJORIS IN 1977.

ABSTRACT The times of 32 primary minima of the eclipsing binary and nova-like variable UX UMa were measured over 1976 and 1977 using higb-speed photometry. The corresponding (0- C)s for 1977 depart significantly from the periodic curve proposed by Mandel. Key worjs: nova4ike variables-eclipsing binaries

Errata

Period changes of UX Ursae Majoris by B. V. Kukarkin was published in Mon. Not. R. astr. Soc., 180, 5P–10P.

ON THE POSSIBILITY OF APSIDAL MOTION IN UX URSAE MAJORIS.

ABSTRACT In the spring of 1975 studies of the UX UMa were conducted with a 76-cm telescope and a two-channel high-speed photometric system. The data obtained in these studies are shown together with observations by Mandel (1965) and by Nather and Robinson (1974). It had been found in previous investigations of the eclipsing binary that variations in the time of eclipse minimum have a cyclic behavior with approximately a 29-year period. An evaluation of the currently available data indicates that apsidal motion may be the cause for the variation in eclipse minimum.

A New Eclipsing Binary of Very Short Period.

view Abstract Citations (18) References (5) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A New Eclipsing Binary of Very Short Period. Lynds, C. R. Abstract The star HD 208392 has been discovered to be an eclipsing binary with the very short orbital period of 20 hours. Except for the peculiar subdwarf system UX Ursae Majoris, this is the shortest period known for any well-observed binary system of spectral class B3 or earlier. The light-curve resembles that of a W Ursae Majoris star with equal primary and secondary minima. The total light-range is 0.1 mag., only half of which is a result of eclipses. There is considerable evidence that the system consists of two similar B2 stars in contact. HD 208392 is situated in the galactic cluster NGC 7160; however, its physical mcmbership in the cluster is somewhat questionable. Publication: The Astrophysical Journal Pub Date: September 1959 DOI: 10.1086/146749 Bibcode: 1959ApJ...130..603L full text sources ADS | data products SIMBAD (4)

The Extremely Rapid Light-Variations of Old Novae and Related Objects

It has been recognized in recent years that extremely rapid light-variations occur in certain stars. Flares lasting only a few minutes have been observed in a number of dMe stars[1]. Flaring has also been observed in the W Ursae Majoris star U Pegasi[2]. Rapid variations in light have been found in some T Tauri stars[3], in the U Geminorum variable AE Aquarii[4,5], and in the short-period eclipsing binary UX Ursae Majoris[6, 7, 8]. Observations during the past two years at the Mount Wilson Observatory have shown that extremely rapid and apparently continuous variations in light occur also in many of the old novae and in a number of related stars.

Photoelectric and Spectroscopic Observations of UX Ursae Majoris.

view Abstract Citations (44) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photoelectric and Spectroscopic Observations of UX Ursae Majoris. Walker, Merle F. ; Herbig, George H. Abstract Some eighteen hundred photoelectric observations of the eclipsing variable UX UMa were made (by Walker) in three colors with the 60- and 100-inch reflectors at Mount Wilson and are described in Section I. They show the asymmetry and stilistand on the rising branch of principal minimum that were discovered by Linnell. Eclipse is preceded by an increase in light of 0.10 mag. and is (at the present time) followed by a rise of about half that amount. The rapid, irregular fluctuations in the light of the system, also discovered by Linnell, were confirmed; their durations range from 1 to 20 minutes, while their amplitudes in the ultraviolet may be as large as 0.18 mag. They are less conspicuous at longer wave lengths. The depth of primary minimum is not always the same; furthermore, its depth increases, the shorter the wave length of observation. No secondary minimum has been observed. In Section II are described spectroscopic observations made (by Herbig) with a continuous-recording technique and a low- dispersion (430 A/mm at H ) spectrograph at the 36inch Crossley reflector of the Lick Observatory. The spectrum of the primary star is of type 0, with very wide and shallow absorption lines. Narrmv absorption is observed at the H lines in the ultraviolet (particularly H8-H1 1) during the later parts of some cycles. The radial velocity given by these narrow H lines is approximately constant, with a value of about +350 to $400 km/sec. Weak emission at HP and rather strong emission at He ii X 4685, neither of which is of constant intensity, vary in velocity throughout the cycle. The increases in brightness of UX UMa before and after primary minimum are due to an intensification of the continuous spectrum and are not accompanied by an enhancement of the emission lines. The variation of the spectrum of UX UMa through the eclipse cycle, like the details of the light-curve, is not ahvays the same. A tentative model that seems to explain some of the features of this remarkable system is discussed in Section III. Publication: The Astrophysical Journal Pub Date: September 1954 DOI: 10.1086/145914 Bibcode: 1954ApJ...120..278W full text sources ADS | data products SIMBAD (2)