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1.
We present the K -band infrared spectrum of the intermediate polar XY Ari. The spectrum confirms the cataclysmic binary nature of XY Ari, showing emission lines of He  i ( λ 2.0587 μm) and the Brackett and Paschen series of H  i . The broad nature of these lines suggests an origin in an accretion disc. The spectrum is strongly reddened by absorption within the molecular cloud Lynds 1457 and shows prominent absorption features from the secondary star, from which we determine a spectral type for the secondary of M0V. The secondary contributes     per cent of the K -band light. We derive a visual extinction to XY Ari of     and a distance of     , placing XY Ari behind the molecular cloud.  相似文献   

2.
We present spectroscopy of the eclipsing recurrent nova U Sco. The radial velocity semi-amplitude of the primary star was found to be     from the motion of the wings of the He  ii λ 4686-Å emission line. By detecting weak absorption features from the secondary star, we find its radial velocity semi-amplitude to be     . From these parameters, we obtain a mass of     for the white dwarf primary star and a mass of     for the secondary star. The radius of the secondary is calculated to be     , confirming that it is evolved. The inclination of the system is calculated to be     , consistent with the deep eclipse seen in the light-curves. The helium emission lines are double-peaked, with the blueshifted regions of the disc being eclipsed prior to the redshifted regions, clearly indicating the presence of an accretion disc. The high mass of the white dwarf is consistent with the thermonuclear runaway model of recurrent nova outbursts, and confirms that U Sco is the best Type Ia supernova progenitor currently known. We predict that U Sco is likely to explode within ∼700 000 yr.  相似文献   

3.
We present spectroscopy of the dwarf nova IP Pegasi taken during two consecutive nights, 5 and 6 d after the start of an outburst. Even this late in the outburst, Doppler maps show marked spiral structure in the accretion disc, at least as strongly as seen earlier in other outbursts of IP Peg. The spiral shocks are present on both nights with no diminution in strength from one night to the next. The light curves of the lines show an offset to earlier phases, with the mid-eclipse of the emission lines displaced to phases between −0.015±0.001 and −0.045±0.009. This cannot be explained by the presence of the accretion shocks. As well as the fixed spiral pattern, the disc shows strong flaring in the Balmer and He  ii   λ 4686-Å lines. Irradiation-induced emission is seen from the companion star in the Balmer, He  i , He  ii , Mg  ii , C  ii , and other lines. The emission is located near the poles of the companion star, suggesting that the accretion disc shields the companion star substantially and thus has an effective H R of order 0.2 at extreme-ultraviolet (EUV) wavelengths. The Balmer emission is distinctly broader than the other lines, consistent with non-Doppler broadening.  相似文献   

4.
Up to now, only a very small number of dwarf novae have been studied during their outburst state (∼30 per cent in the Northern hemisphere). In this paper we present the first comprehensive atlas of outburst spectra of dwarf novae. We study possible correlations between the emission and absorption lines seen in the spectra and some fundamental parameters of the binaries. We find that out of the 48 spectra presented, 12 systems apart from IP Peg show strong He  ii in emission: SS Aur, HL CMa, TU Crt, EM Cyg, SS Cyg, EX Dra, U Gem, HX Peg, GK Per, KT Per, V893 Sco, IY UMa, and seven others less prominently: FO And, V542 Cyg, B  i Ori, TY Psc, VZ Pyx, ER UMa and SS UMi. We conclude that these systems are good targets for finding spiral structure in their accretion discs during outburst if the models of Smak and Ogilvie are correct. This is confirmed by the fact that hints of spiral asymmetries have already been found in the discs of SS Cyg, EX Dra and U Gem.  相似文献   

5.
The eclipsing nova-like cataclysmic variable star V348 Pup exhibits a persistent luminosity modulation with a period 6 per cent longer than its 2.44-h orbital period ( P orb). This has been interpreted as a 'positive superhump' resulting from a slowly precessing non-axisymmetric accretion disc gravitationally interacting with the secondary. We find a clear modulation of mid-eclipse times on the superhump period, which agrees well with the predictions of a simple precessing eccentric disc model. Our modelling shows that the disc light centre is on the far side of the disc from the donor star when the superhump reaches maximum light. This phasing suggests a link between superhumps in V348 Pup and late superhumps in SU UMa systems. Modelling of the full light curve and maximum entropy eclipse mapping both show that the disc emission is concentrated closer to the white dwarf at superhump maximum than at superhump minimum. We detect additional signals consistent with the beat periods between the implied disc precession period and both and  相似文献   

6.
AC Cnc is a nova-like, eclipsing binary of period 7h13m. I chose it for observation because its eclipses are rather symmetrical. A photometric solution gives inclination i = 74.5° ± 0.8°, mass of white dwarf M1 = 0.74 ± 0.07 M, mass of the late-type companion, M2 = 0.97 ± 0.8 M. Temperature of the accretion disk varies approximately as inverse half-power of the radial distance, the temperature at the edge of the disk is 7600 K. Rate of mass transfer from the late-type star to the white dwarf is 7(−9) M/yr. The distance of AC Cnc is 500 ± 100 pc.  相似文献   

7.
We present results obtained from near-infrared JHK spectroscopic observations of novae V2491 Cygni and V597 Puppis in the early declining phases of their 2007 and 2008 outbursts, respectively. In both objects, the spectra displayed emission lines of H  i , O  i , He  i and N  i . In V597 Pup, the He  i lines were found to strengthen rapidly with time. Based on the observed spectral characteristics, both objects are classified as He/N novae. We have investigated the possibility of V2491 Cyg being a recurrent nova as has been suggested. By studying the temporal evolution of the linewidths in V2491 Cyg, it appears unlikely that the binary companion is a giant star with heavy wind as in recurrent novae of the RS Oph type. Significant deviations from that of recombination case B conditions are observed in the strengths of the H  i lines. This indicates that the H  i lines, in both novae, are optically thick during the span of our observations. The slope of the continuum spectra in both cases was found to have a  λ−(3−3.5)  dependence which deviates from a Rayleigh–Jeans spectral distribution. Both novae were detected in the post-outburst supersoft X-ray phase; V2491 Cyg being very bright in X-rays has been the target of several observations. We discuss and correlate our infrared observations with the observed X-ray properties of these novae.  相似文献   

8.
A time-resolved spectroscopic study of V603 Aql (Nova Aquilae 1918) is presented. An orbital period of P orb=01385±00002, consistent with previous results, and a radial velocity semi-amplitude of K =20±3 km s1 are obtained from the radial velocity variations of the H emission line. Similar K values are also found in H , H , and He  i emission lines. Using the measured FWHM of the H line and assuming that the derived semi-amplitude is that of the white dwarf, we deduce a most likely mass ratio of q =0.24±0.05 and stellar masses of M 2=0.29±0.04 M and M 1=1.2±0.2 M for the secondary and primary (the white dwarf) star, respectively. The dynamical solution also indicates a very low orbital inclination, i =13°±2°. We find that the continuum and line variations are modulated with both the positive and the negative superhump periods, indicating that they arise from similar regions of the accretion disc. Moreover, we find, for the first time from spectroscopy, evidence of negative superhumps in addition to the positive superhumps. Positive superhumps are explained within the disc instability model as caused by an eccentric disc surrounding the white dwarf, which is precessing (apsidal advance) because of tidal instabilities, causing the observed positive superhumps. A nodal precession in the accretion disc is currently believed to be the cause of the observed negative superhumps. The low value of q is consistent with the expected value for systems that show superhumps, in accordance with the eccentric disc model. We find no evidence of periodicity associated with the spin period.  相似文献   

9.
We present our second paper describing multiwaveband time-resolved spectroscopy of WZ Sge. We analyse the evolution of both optical and IR emission lines throughout the orbital period and find evidence, in the Balmer lines, for an optically thin accretion disc and an optically thick hotspot. Optical and IR emission lines are used to compute radial velocity curves. Fits to our radial velocity measurements give an internally inconsistent set of values for K 1, γ and the phase of red-to-blue crossing. We present a probable explanation for these discrepancies, and provide evidence for similar behaviour in other short orbital period dwarf novae. Selected optical and IR spectra are measured to determine the accretion disc radii. Values for the disc radii are found to be strongly dependent on the assumed WD mass and binary orbital inclination. However, the separation of the peaks in the optical emission line (i.e., an indication of the outer disc radius) has been found to be constant during all phases of the supercycle period over the last 40 years.  相似文献   

10.
We present the complete set of 34 ASCA observations of non-magnetic cataclysmic variables. Timing analysis reveals large X-ray flux variations in dwarf novae in outburst (Z Cam, SS Cyg and SU UMa) and orbital modulation in high inclination systems (including OY Car, HT Cas, U Gem, T Leo). We also found episodes of unusually low accretion rate during quiescence (VW Hyi and SS Cyg). Spectral analysis reveals broad temperature distributions in individual systems, with emission weighted to lower temperatures in dwarf novae in outburst. Absorption in excess of interstellar values is required in dwarf novae in outburst, but not in quiescence. We also find evidence for subsolar abundances and X-ray reflection in the brightest systems.
LS Peg, V426 Oph and EI UMa have X-ray spectra that are distinct from the rest of the sample and all three exhibit candidate X-ray periodicities. We argue that they should be reclassified as intermediate polars.
In the case of V345 Pav we found that the X-ray source had been previously misidentified.  相似文献   

11.
We present time-resolved optical spectroscopy of the deeply eclipsing nova-like binary V347 Pup, which provides evidence for a rotational velocity field in the low-excitation lines, as expected from accretion disc emission. The low-excitation line profiles are a composite of the disc and the irradiated inner-face of the donor star. This picture is remarkably simple compared to the other members of the eclipsing nova-like family. Unsatisfactory radial velocity solutions for the accreting object provided by standard methods encourage us to apply a technique developed to measure stellar motion from tomographic reconstructions of the time-dependent line profiles. We find some evidence for a spiral pattern over the disc and for disc-overflow accretion. If the emission distribution proves to be a long-term feature, V347 Pup will provide an opportunity to study disc kinematics with greater confidence than allowed by the other eclipsing nova-like objects.  相似文献   

12.
We consider the effects of accretion stream overflow on the viscous dynamics of accretion discs in dwarf novae. If the stream from the secondary star is geometrically thick enough, some fraction of its material can flow over and under the disc. The mass and specific angular momentum of the stream are then deposited not only at the point of collision with the outer disc, but also at those radii in the inner disc with geometric heights that are large enough to intercept the residual stream, or near the radius where the disc has the same specific angular momentum as the stream. The overflowing stream can alter the behaviour of heating fronts and cooling fronts in the disc. If the mass fraction of the overflowing stream is of order tens of per cent, the deposition of mass in the inner parts of the disc is sufficient to change the character of the eruption light curves significantly.  相似文献   

13.
We present time-resolved spectroscopy and photometry of the double-lined eclipsing cataclysmic variable V347 Pup (=LB 1800). There is evidence of irradiation on the inner hemisphere of the secondary star, which we correct for using a model to give a secondary-star radial velocity of   K R= 198 ± 5 km s−1  . The rotational velocity of the secondary star in V347 Pup is found to be   v sin  i = 131 ± 5 km s−1  and the system inclination is   i = 840 ± 23  . From these parameters we obtain masses of   M 1= 0.63 ± 0.04 M⊙  for the white dwarf primary and   M 2= 0.52 ± 0.06 M⊙  for the M0.5V secondary star, giving a mass ratio of   q = 0.83 ± 0.05  . On the basis of the component masses, and the spectral type and radius of the secondary star in V347 Pup, we find tentative evidence for an evolved companion. V347 Pup shows many of the characteristics of the SW Sex stars, exhibiting single-peaked emission lines, high-velocity S-wave components and phase-offsets in the radial velocity curve. We find spiral arms in the accretion disc of V347 Pup and measure the disc radius to be close to the maximum allowed in a pressureless disc.  相似文献   

14.
We present time-resolved, J ‐band (1.025–1.340 μm) infrared spectra of the short-period dwarf novae (DNe) WZ Sge and VY Aqr, and single spectra of the short-period DN EF Peg and the nova-like variable PX And. There is some evidence in the spectra of VY Aqr and EF Peg that we have detected the secondary star, both in the continuum slope and also through the possible presence of spectral features. The spectra of WZ Sge and PX And, on the other hand, show no evidence for the secondary star, with upper limits for its contribution to the J ‐band light of 10 and 20 per cent respectively. The spectral type of the secondary in WZ Sge is constrained to be later than M7.5V. Using skew mapping, we have been able to derive a value for the radial velocity semi-amplitude of the secondary star in VY Aqr of K R =320±70 km s−1, which in conjunction with K W from Thorstensen & Taylor gives a mass ratio of q =0.15±0.04.  相似文献   

15.
We present Doppler and modulation tomography of the X-ray nova XTE J1118+480 with data obtained during quiescence using the 10-m Keck II telescope. The hotspot where the gas stream hits the accretion disc is seen in Hα, Hβ, He  i λ5876 and Ca  ii λ8662, thus verifying the presence of continued mass transfer within the system. The disc is clearly seen in Hα and Ca  ii λ8662. We image the mass-donor star in narrow absorption lines of Na  i  λλ5890, 5896, 8183, 8195  and Ca  ii λ8662, implying an origin from the secondary itself rather than the interstellar medium. We also detect deviations in the centroid of the double peak of Hα akin to those found by Zurita et al. suggesting disc eccentricity.  相似文献   

16.
We present a small sample of time-resolved optical spectroscopy of the dwarf nova HL CMa during an outburst state. By combining radial velocity measurements with published data we show that the previously quoted value is not the only candidate for the orbital period of this system. We reduce the significance of daily aliasing but cannot distinguish between two periods at 0.2146±0.0004 and 0.2212±0.0005 d. We show that the low-excitation emission lines are composites from an accretion disc and the companion star, and that high-excitation emission originates in the disc or outflowing material associated with the accreting white dwarf.  相似文献   

17.
Two nights of phase-resolved medium-resolution Very Large Telescope spectroscopy of the extra-galactic low-mass X-ray binary LMC X−2 have revealed a 0.32 ± 0.02 d spectroscopic period in the radial velocity curve of the He  ii λ4686 emission line that we interpret as the orbital period. However, similar to previous findings, this radial velocity curve shows a longer term variation that is most likely due to the presence of a precessing accretion disc in LMC X−2. This is strengthened by He  ii λ4686 Doppler maps that show a bright spot that is moving from night to night. Furthermore, we detect narrow emission lines in the Bowen region of LMC X−2, with a velocity of   K em= 351 ± 28 km s−1  , that we tentatively interpret as coming from the irradiated side of the donor star. Since K em must be smaller than K 2, this leads to the first upper limit on the mass function of LMC X−2 of   f ( M 1) ≥ 0.86  M⊙  (95 per cent confidence), and the first constraints on its system parameters.  相似文献   

18.
We present time-resolved optical spectroscopy and photometry of the nova-like cataclysmic variable V348 Puppis. The system displays the same spectroscopic behaviour as SW Sex stars, so we classify V348 Pup as a new member of the class. V348 Pup is the second SW Sex system (the first is V795 Herculis) which lies in the period gap. The spectra exhibit enhanced He  ii λ 4686 emission, reminiscent of magnetic cataclysmic variables. The study of this emission line gives a primary velocity semi-amplitude of     . We have also derived the system parameters, obtaining:     ,         ,     and     . The spectroscopic behaviour of V348 Pup is very similar to that of V795 Her, with the exception that V348 Pup shows deep eclipses. We have computed the '0.5-absorption' spectrum of both systems, obtaining spectra that resemble the absorption spectrum of a B0 V star. We propose that absorption in SW Sex systems can be produced by a vertically extended atmosphere which forms where the gas stream re-impacts the system, either at the accretion disc or at the magnetosphere of the white dwarf (assuming a magnetic scenario).  相似文献   

19.
We carried out spectroscopic observations of the candidate black hole binary GX 339−4 during its low–hard and high–soft X-ray states. We have found that the spectrum is dominated by emission lines of neutral elements with asymmetric, round-topped profiles in the low–hard state. In the high–soft state, however, the emission lines from both neutral and ionized elements have unambiguously resolved double-peaked profiles. The detection of double-peaked emission lines in the high–soft state, with a larger peak separation for higher ionization lines, indicates the presence of an irradiatively heated accretion disc. The round-topped lines in the low–hard state are probably caused by a dense matter outflow from an inflated non-Keplerian accretion disc. Our data do not show velocity modulations of the line centres caused by the orbital motion of the compact object, neither do the line basewidths show substantial variations in each observational epoch. There are no detectable absorption lines from the companion star. All these features are consistent with those of a system with a low-mass companion star and low orbital inclination.  相似文献   

20.
We present phase resolved optical spectroscopy and Doppler tomography of V1341 Cygni, the optical counterpart to the neutron star low-mass X-ray binary (LMXB) Cygnus X-2 (Cyg X-2). We derive a radial velocity (RV) curve for the secondary star, finding a projected RV semi-amplitude of   K 2= 79 ± 3 km s−1  , leading to a mass function of  0.51 ± 0.06 M⊙, ∼30  per cent lower than the previous estimate. We tentatively attribute the lower value of K 2 (compared to that obtained by other authors) to variations in the X-ray irradiation of the secondary star at different epochs of observations. The limited phase coverage and/or longer timebase of previous observations may also contribute to the difference in K 2. Our value for the mass function implies a primary mass of  1.5 ± 0.3 M⊙  , somewhat lower than previous dynamical estimates, but consistent with the value found by analysis of type-I X-ray bursts from this system. Our Doppler tomography of the broad He  ii λ4686 line reveals that most of the emission from this line is produced on the irradiated face of the donor star, with little emission from the accretion disc. In contrast, the Doppler tomogram of the N  iii λ4640.64 Bowen blend line shows bright emission from near the gas stream/accretion disc impact region, with fainter emission from the gas stream and secondary star. This is the first LMXB for which the Bowen blend is dominated by emission from the gas stream/accretion disc impact region, without comparable emission from the secondary star. This has implications for the interpretation of Bowen blend Doppler tomograms of other LMXBs for which the ephemeris may not be accurately known.  相似文献   

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