Mass Transfer Bursts Research Articles

Detection of the supercycle in V4140 Sagittarii: First eclipsing ER Ursae Majoris-like object

Abstract We observed the deeply eclipsing SU UMa-type dwarf nova V4140 Sgr and established the very short supercycle of 69.7(3) d. There were several short outbursts between superoutbursts. These values, together with the short orbital period (0.06143 d), were similar to, but not as extreme as, those of ER UMa-type dwarf novae. The object is thus the first, long sought, eclipsing ER UMa-like object. This ER UMa-like nature can naturally explain the high (apparent) quiescent viscosity and unusual temperature profile in quiescence, which were claimed observational features against the thermal–tidal instability model. The apparently unusual outburst behavior can be reasonably explained by a combination of this ER UMa-like nature and the high orbital inclination, and there is no need to introduce mass transfer bursts from its donor star.

Infrared photometry of the dwarf nova V2051 Ophiuchi – I. The mass-donor star and the distance★

We report the analysis of time-series of infrared $JHK_s$ photometry of the dwarf nova V2051 Oph in quiescence. We modelled the ellipsoidal variations caused by the distorted mass-donor star to infer its $JHK_s$ fluxes. From its infrared colors we estimate a spectral type of $M(8.0\pm 1.5)$ and an equivalent blackbody temperature of $T_\mathrm{BB}=(2700\pm270)\,K$. We used the Barnes & Evans relation to infer a photometric parallax distance of $d_\mathrm{BE}=(102\pm16)$ pc to the binary. At this short distance, the corresponding accretion disc temperatures in outburst are too low to be explained by the disc-instability model for dwarf nova outbursts, underscoring a previous suggestion that the outbursts of this binary are powered by mass-transfer bursts.

SOAR observations of the high-viscosity accretion disc of the dwarf nova V4140 Sagitarii in quiescence and in outburst

We report the analysis of 22 B-band light curves of the dwarf nova V4140 Sgr obtained with SOI/SOAR during two nights along the decline of a superoutburst in 2006 Sep 12-24 and in quiescence over 50 days following the superoutburst. Three-dimensional eclipse mapping of the outburst light curves indicates that the accretion disc is elliptical (eccentricity e=0.13) and that superhump maximum occurs when the mass donor star is aligned with the bulge of the elliptical disc. The accretion disc is geometrically thin both in outburst and in quiescence; it fills the primary Roche lobe in outburst and shrinks to about half this size in quiescence. The stability of the eclipse shape, width and depth along quiescence and the derived disc surface brightness distribution indicate that the quiescent accretion disc is in a high-viscosity, steady-state. Flickering mapping of the quiescent data reveal that the low-frequency flickering arises from an azimuthally-extended stream-disc impact region at disc rim and from the innermost disc region, whereas the high-frequency flickering originates in the accretion disc. Assuming the disc-related flickering to be caused by fluctuations in the energy dissipation rate induced by magneto-hydrodynamic turbulence (Gertseema & Achterberg 1992), we find that the quiescent disc viscosity parameter is large (alpha ~ 0.2-0.4) at all radii. The high-viscosity quiescent disc and the inferred low disc temperatures in superoutburst are inconsistent with expectations of the disc-instability model, and lead to the conclusion that the outbursts of V4140 Sgr are powered by mass transfer bursts from its donor star.

Exploring the long-term variability and evolutionary stage of the interacting binary DQ Velorum

To progress in the comprehension of the double periodic variable (DPV) phenomenon, we analyse a series of optical spectra of the DPV system DQ Velorum during much of its long-term cycle. In addition, we investigate the evolutionary history of DQ Vel using theoretical evolutionary models to obtain the best representation for the current observed stellar and orbital parameters of the binary. We investigate the evolution of DQ Vel through theoretical evolutionary models to estimate the age and the mass transfer rate which are compared with those of its twin V393 Scorpii. Donor subtracted spectra covering around 60% of the long-term cycle, allow us to investigate time-modulated spectral variations of the gainer star plus the disc. We compare the observed stellar parameters of the system with a grid of theoretical evolutionary tracks computed under a conservative and a non-conservative evolution regime. We have found that the EW of Balmer and helium lines in the donor subtracted spectra are modulated with the long-term cycle. We observe a strenghtening in the EWs in all analysed spectral features at the minimum of the long-term cycle which might be related to an extra line emission during the maximum of the long-term variability. Difference spectra obtained at the secondary eclipse support this scenario. We have found that a non-conservative evolutionary model is a better representation for the current observed properties of the system. The best evolutionary model suggests that DQ Vel has an age of 7.40 x 10^{7} yr and is currently in a low mass transfer rate (-9.8x10^{-9} Msun/yr) stage, after a mass transfer burst episode. Comparing the evolutionary stages of DQ Vel and V393 Sco we observed that the former is an older system with a lower mass transfer rate. This might explain the differences observed in the physical parameters of their accretion discs.

MASS TRANSFER VARIATIONS IN UX MONOCEROTIS: EIGHT YEARS OF AUTOMATED PHOTOMETRIC MONITORING

We analyze eight years (1999-2007) of automated photometric observations of the active Algol binary UX Monocerotis to search for mass transfer bursts similar to those seen in U Cephei. The largest photometric anomaly is the mean gainer luminosity difference between the stream-impact hemisphere and the opposite hemisphere. We find an updated Wilson-Devinney solution for earlier six-color observations. The UX Mon donor star fills its Roche lobe and the gainer nearly fills its rotational lobe. Instead of isolated bursts of the U Cep type, we found nearly continuous brightness fluctuations likely produced by variable mass transfer. We discuss implications for mass transfer.

Multicolour Photometry and Spectroscopy of the Slow Nova V475 Sct (Nova Scuti 2003)

The UBVRI photometry and 460–900 nm spectroscopy of a classical nova V475 Sct obtained after its outburst in August 2003 is discussed. The nova was classified as a Fe II slow nova with the t2,V = 48 d, t3,V = 53 d. The absolute magnitudes of the nova at maximum MVmax = −7.16±0.15, MBmax = −6.96±0.39, the color excess E(B−V) = 0.69±0.05 and the distance to the nova d = 4.8±0.9 kpc was determined. Observed 13.4-day periodicity of flares can be explained either by pulsation of the nova envelope or by the mass transfer bursts from the red to the white dwarf probably caused by a periastron passage of the third body. The rapid fade of the brightness, which started 57 days after the maximum, is related to a dust formation in the ejecta of the nova. The early optical spectra display the forest of low ionization emission lines, primarily Fe II and Balmer H, accompanied by two P Cygni absorptions, arising in the inner and outer envelope of the expanding nova shell ejected at brightness maximum and accelerated by continuous stellar wind. The spectrum taken in the nebular stage of the nova, which started in March 2004, shows very strong emission [O III] 495.9 nm and 500.7 nm lines, responsible for discrepancy of the B and V magnitudes determined from observations taken by different instruments. The nebular emission line profiles suggest a nonspherical ejection of the shell.

Interpretation of the 1998 outburst of the unique X-ray transient CI Camelopardalis (XTE J0421+560)

We present an analysis of the 1998 outburst of the peculiar X-ray binary and X-ray transient CI Cam (XTE J0421+560). We discuss the observations in the framework of several possible models and argue that this outburst can be explained by the thermal instability of the accretion disc, analogous to the outbursts of soft X-ray transients. Applying the model by King & Ritter and Shahbaz, Charles & King on the X-ray light curve, we obtain a realistic mass of the disc at the peak of outburst to be M h (0) ≈ 1.5 x 10 23 g (the distance d = 5 kpc) or 3.8 × 10 22 g (d = 2.5 kpc). The disc radius at this moment is then R h (0) ≈ 2.5 x 1010 cm (d = 5 kpc) or 1.6 x 10 10 cm (d = 2.5 kpc), provided that the factor / (the ratio of the mass of the hot disc at that moment with respect to its maximum possible mass) is close to unity. Even if we take a quite low f = 0.05, we still obtain R h (0) by only 2.7 times larger. The reddening in the outburst maximum and brighter peak absolute magnitude of CI Cam with respect to those of soft X-ray transients in outbursts can be explained if the disc in CI Cam heats up an extended envelope and/or a strong jet is formed. We thus bring firm arguments for Robinson, Ivans & Welsh's hypothesis. On the other hand, we bring the arguments against the mass transfer burst from the donor and the periastron passage of the compact object.

V475 Sct (Nova Scuti 2003) – Binary or Triple System?

UBV RI photometry and 4600–9000 A spectroscopy of nova V475 Sct taken in the first 3 month after discovery is presented. The object can be classified as a Fe II type slow nova with t2,V = 48 days, t3,V = 53 days. The absolute magnitude of the nova at maximum, its colour excess and distance were determined. The observed 13.4 day periodicity of flares can be explained by the mass transfer bursts from the red to the white dwarf, probably caused by the periastron passage of a third body. Two sets of absorptions are seen in the P Cyg-type Hα line profile. They arise in the expanding shell of the nova.

Mass-transfer bursts and the superhumps in cataclysmic variables

It is suggested that the superhumps in SU UMa stars are generated by a bright region on the red component that rotates asynchronously with the binary period. The bright region would be produced by mass-transfer instability by the red component. A simple experimental illustration of dynamical instability is presented, together with estimates of cooling times after instability.

Multifrequency Study of the Very Slow Nova V723 Cas

Multifrequency behaviour of the very slow nova V723 Cas is reviewed. The long-term photometry of the object revealed the orbital period 0.693265 days of the binary, quasi-periodic oscillations in the envelope of the outbursted white dwarf and 182 days periodicity of activity due to the mass transfer bursts from the red to the white dwarf probably caused by a periastron passage of the third body. The photometry at the maximum of brightness was used to calculate the velocity v = 210 {r km s}^{-1} of ejection of an expanding supergiant photosphere -- main inner envelope of the nova. The emission line profiles in nebular stage show multiple peaks formed in an expanding equatorial ring and polar blobs of this envelope. The HeI line profile and radio observations suggest the existence of the outer envelope, shaped and accelerated by the spherical and polar winds, detected as absorption components of the HI and HeI P Cygni type line profiles. Radio observations allowed to determine ejected mass 2.5 x 10 -4 M o and confirmed the clumpy structure of the ejecta.

The Accretion Disk Model for the First Hundred Days of the Outburst Evolution in the Black Hole X-Ray Novae

We present time-dependent, irradiated, accretion disk models for the black hole X-ray novae in the first hundred days of the dwarf nova-like outbursts, including the rise, precursor, maximum and the secondary re-flare. This work is based on the disk instability model (Kim, Mineshige & Wheeler 1996, Kim, Wheeler & Mineshige 1996). The model is reasonably consistent with the observed optical light curves. The irradiators are the central hot region around the black hole, and the corona or chromosphere above the accretion disk. In addition, we include the time-dependent shadowing effect and consequent blocking of the outer portions of the disk from the central irradiator. We find the stagnation phenomenon whereby the disk stays in the intermediate temperature stage between the hot and cool state. This can explain the recently discovered optical precursor rise prior to the maximum light in Nova Sco 1994 (Bailyn et al. 1995: see Fig. 1). We suggest the secondary re-flare after the maximum is due to the coupled effects of the irradiation and stagnation. In the model, the stagnation phenomenon during the rise results from the partial ionization and molecular opacity. In addition, we find irradiation-induced stagnation during the decay phase, which is consistent with the observed secondary re-flare in X-ray novae (see Fig. 1). In the overall evolution of model outbursts in the first hundred days, the outer disk is blocked from the irradiation and, in turn, the companion star may not be strongly irradiated. This suggests that there is no appreciable increase of mass transfer rate during the decay prior to the secondary re-flare, unlike the behaviour in the mass transfer burst models.

New Observational Frontiers of ER UMa (= PG 0943+521) Type Dwarf Novae

The ER UMa-type, including ER UMa, V1159 Ori and RZ LMi, is a subgroup of SU UMa-type dwarf novae. Outbursts of these stars are characterized by: (i) the extremely short recurrence time of the superoutburst (~ 40 d in ER UMa and V1159 Ori, ~ 20 d in RZ LMi), (ii) short outbursts with short recurrence times (~ 4 d) between the bright states, and (iii) extremely long duty cycles (~ 0.5). Assuming that the mass transfer rate from the secondary is ten times higher than that of ordinary SU UMa stars, which was invoked by Kato & Kunjaya (1995), and a weak tidal torque in the case of RZ LMi, Osaki (1996) showed that the light curves of these stars can be reproduced by the disk instability model, which does not require mass transfer bursts. These indicate that ER UMa, V1159 Ori and RZ LMi are not on the natural extension of SU UMa-type dwarf novae.

Secondary maxima of black hole X-ray transients: A clue to understanding X-ray irradiation

The secondary maxima are commonly observed in transient black hole candidates at 50-70 days after the main peaks. To investigate its physical origin, we build simple time-dependent disk models based on the disk instability model. We find that a mass transfer burst gives a rather slow rise, whereas an abrupt heating of the disk results in a rapid decay, both of which are inconsistent with the observations. To account for the observations, we require both an abrupt heating of the disk and a substantial mass supply. The abrupt heating could be caused by a sudden onset of the X-ray illumination when a Compton cloud, which so far blocked X-rays to the outer parts, becomes transparent or evaporates, while the mass supply may be due to either an enhanced mass outflow from the companion star or a transient recession of the cooling front in the disk. The minioutbursts observed in GRO J0422+32 after its main outburst could be triggered by a thermal instability, if the disk suffers X-ray illumination or an enhanced tidal dissipation.

A three-dimensional smoothed particle hydrodynamics simulation of the active phase of SS Cyg-type discs and its implications for the mass transfer burst model

We perform a smoothed particle hydrodynamics (SPH) three-dimensional simulation of the outburst phase of the accretion disc of a typical SS Cyg-like dwarf nova in the framework of the mass transfer burst model (MTBM), where we assume that the active phase is triggered by a sudden increase in the accretion rate due to some instability in the secondary's atmosphere. The evolution of the accretion disc is followed for a single orbital period, starting from the initial quiescent disc configuration obtained by us in a previous paper. This is a suitable integration time for determining the geometrical and physical properties of the disc in the impulsive phase and is comparable with observed outburst time-scales

Accretion Disk Evolution

AbstractThree aspects of mass transfer instability models of dwarf novae are examined. The hydrodynamic development of instabilities in the secondary are examined within Roche geometry and shown to extend at least a few degrees away from the line of centres. The form of the outburst light curves observed in SS Cygni are shown to be a natural consequence of mass transfer bursts with a duration either less than, or greater than, the disk viscous timescale. Finally the two-dimensional structure of the disc in the plane of the orbit is studied. As with α-disks the viscous evolution time following a burst of mass transfer determines the size of viscosity within the disk. Significant deviations from axial symmetry are found to be present.

Cataclysmic variable stars

The properties of cataclysmic variable outbursts are reviewed, and interpreted in terms of dynamical instabilities by the red component, and subsequent evolution of the white dwarf accretion disc subject to a mass transfer burst in the transfer stream.

Cataclysmic Variable Stars

AbstractThe properties of cataclysmic variable outbursts are reviewed, and interpreted in terms of dynamical instabilities by the red component, and subsequent evolution of the white dwarf accretion disc subject to a mass transfer burst in the transfer stream.

Alpha Beta Discs

Following earlier work of Lynden-Bell & Pringle (1974) and Lightman (1974a, 1974b), Bath & Pringle (1981) have presented a simple method for studying the time-dependent evolution of viscous accretion discs. These models are axisymmetrlc, with the vertical structure reduced to integrated averages of local physical conditions. Published work examines models of dwarf nova eruptions driven by mass transfer bursts (Bath & Pringle 1981 – Paper I), eruptions produced by global viscous changes within the disc (Bath & Pringle 1982a Paper II), and the time-dependent properties of giant discs in symbiotic binaries (Bath & Pringle 1982b – Paper III).