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1.
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   

2.
High-resolution spectroscopic observations around the Hα line and BVRI photometry of the eclipsing short-period RS CVn star UV Leo are presented. The simultaneous light-curve solution and radial velocity-curve solution led to the following values of the global parameters of the binary: temperatures   T 1= 6000 ± 100 K  and   T 2= 5970 ± 20 K  ; masses   M 1= 0.976 ± 0.067 M⊙  and   M 2= 0.931 ± 0.052 M⊙  ; separation   a = 3.716 ± 0.048 R⊙  ; orbital inclination     ; radii   R 1= 1.115 ± 0.052 R⊙  and   R 2= 1.078 ± 0.051 R⊙  ; equatorial velocities   V 1= 98.8 ± 2.3 km s−1  and   V 2= 89.6 ± 2.7 km s−1  . These results lead to the conclusion that the two components of UV Leo are slightly oversized for their masses and lie within the main-sequence band on the mass–radius diagram, close to the isochrone 9 × 1010 yr.  相似文献   

3.
The time sequence of 105 spectra covering one full orbital period of AA Dor has been analysed. Direct determination of   V  sin  i   for the sdOB component from 97 spectra outside of the eclipse for the lines Mg  ii 4481 Å and Si  iv 4089 Å clearly indicated a substantially smaller value than estimated before. Detailed modelling of line-profile variations for eight spectra during the eclipse for the Mg  ii 4481 Å line, combined with the out-of-eclipse fits, gave   V  sin  i = 31.8 ± 1.8 km s−1  . The previous determinations of   V  sin  i   , based on the He  ii 4686 Å line, appear to be invalid because of the large natural broadening of the line. With the assumption of the solid-body, synchronous rotation of the sdOB primary, the measured values of the semi-amplitude K 1 and   V  sin  i   lead to the mass ratio   q = 0.213 ± 0.013  which in turn gives K 2 and thus the masses and radii of both components. The sdOB component appears to be less massive than assumed before,   M 1= 0.25 ± 0.05 M⊙  , but the secondary has its mass–radius parameters close to theoretically predicted for a brown dwarf,   M 2= 0.054 ± 0.010 M⊙  and   R 2= 0.089 ± 0.005 R⊙  . Our results do not agree with the recent determination of Vŭcković et al. based on a K 2 estimate from line-profile asymmetries.  相似文献   

4.
We have discovered that the spectrum of the well-known dwarf nova EM Cyg is contaminated by light from a K25V star (in addition to the K-type mass donor star). The K25V star contributes approximately 16 per cent of the light from the system and if not taken into account has a considerable effect upon radial velocity measurements of the mass donor star. We obtain a new radial velocity amplitude for the mass donor star of K 2=202±3 km s1, compared with the value of K 2=135±3 km s1 obtained in Stover, Robinson & Nather's classic study of EM Cyg. The revised value of the amplitude, combined with a measurement of rotational broadening of the mass donor, v  sin  i =140±6 km s1, leads to a new mass ratio of q M 2 M 1=0.88±0.05. This solves a long-standing problem with EM Cyg, because Stover et al.'s measurements indicated a mass ratio q >1, a value that should have led to dynamically unstable mass transfer for the secondary mass deduced by Stover et al. The revised value of the mass ratio, combined with the orbital inclination i =67±2°, leads to masses of 0.99±0.12 M and 1.12±0.08 M for the mass donor and white dwarf respectively. The mass donor is evolved, because it has a later spectral type (K3) than its mass would imply.
We discuss whether the K star could be physically associated with EM Cyg or not, and present the results of the spectroscopic study.  相似文献   

5.
Intermediate-resolution (0.5–1 Å) optical spectroscopy of the cataclysmic variable (CV) SY Cnc reveals the spectrum of the donor star. Our data enable us to resolve the orbital motion of the donor and provide a new orbital solution, binary mass ratio and spectral classification. We find that the donor star has spectral-type G8 ± 2 V and orbits the white dwarf with   P = 0.382 3753 ± 0.000 0003  d,   K 2= 88.0 ± 2.9  km s−1 and   V sin  i = 75.5 ± 6.5  km s−1. Our values are significantly different from previous works and lead to   q = M 2/ M 1= 1.18 ± 0.14  . This is one of the highest mass ratios known in a CV and is very robust, because it is based on resolving the rotational broadening over a large number of metallic absorption lines. The donor could be a slightly evolved main sequence or descendant from a massive star which underwent an episode of thermal time-scale mass transfer.  相似文献   

6.
We use accurate absolute proper motions and Two-Micron All-Sky Survey   Ks   -band apparent magnitudes for 364 Galactic RR Lyrae variables to determine the kinematical parameters of the Galactic RR Lyrae population and constrain the zero-point of the   Ks   -band period–luminosity relation for these stars via statistical parallax. We find the mean velocities of the halo- and thick-disc RR Lyrae populations in the solar neighbourhood to be  [ U 0(Halo), V 0(Halo), W 0(Halo)]= (−12 ± 10, −217 ± 9, −6 ± 6) km s−1  and  [ U 0(Disc), V 0(Disc), W 0(Disc)]= (−15 ± 7, −44 ± 7, −25 ± 5) km s−1  , respectively, and the corresponding components of the velocity-dispersion ellipsoids,  [σ VR (Halo), σ V θ(Halo), σ W (Halo)]= (167 ± 9, 86 ± 6, 78 ± 5) km s−1  and  [σ VR (Disc), σ V θ(Disc), σ W (Disc)]= (55 ± 7, 44 ± 6, 30 ± 4) km s−1  , respectively. The fraction of thick-disc stars is estimated at  0.25 ± 0.03  . The corrected infrared period–luminosity relation is     , implying a Large Magellanic Cloud (LMC) distance modulus of  18.27 ± 0.08  and a solar Galactocentric distance of  7.58 ± 0.40 kpc  . Our results suggest no or slightly prograde rotation for the population of halo RR Lyraes in the Milky Way.  相似文献   

7.
Simultaneous spectroscopic and photometric observations of the Z Cam type dwarf nova SY Cancri were used to obtain absolute flux calibrations. A comparison of the photometric calibration with a wide-slit spectrophotometric calibration showed that either method is equally satisfactory. A radial velocity study of the secondary star, made using the far-red Na  i doublet, yielded a semi-amplitude of   K 2= 127 ± 23 km s−1  . Taking the published value of  86 ± 9 km s−1  for K 1 gives a mass ratio of   q = M 2/ M 1= 0.68 ± 0.14  ; this is very different from the value of  1.13 ± 0.35  quoted in the literature. Using the new lower mass ratio, and constraining the mass of the white dwarf to be within reasonable limits, then leads to a mass for the secondary star that is substantially less than would be expected for its orbital period if it satisfied a main-sequence mass–radius relationship. We find a spectral type of M0 that is consistent with that expected for a main-sequence star of the low mass we have found. However, in order to fill its Roche lobe, the secondary must be significantly larger than a main-sequence star of that mass and spectral type. The secondary is definitely not a normal main-sequence star.  相似文献   

8.
We present spectrophotometry of the eclipsing old nova BT Mon (Nova Mon 1939). By detecting weak absorption features from the secondary star, we find its radial velocity semi-amplitude to be K R = 205 ± 5 km s−1 and its rotational velocity to be v  sin  i  = 138 ± 5 km s−1. We also measure the radial velocity semi-amplitude of the primary star to be K R = 170 ± 10 km s−1. From these parameters we obtain a mass of 1.04 ± 0.06 M⊙ for the white dwarf primary star and a mass of 0.87 ⊙ 0.06 M⊙ for the G8 V secondary star. The inclination of the system is found to be 82°.2 ± 32°.2 and we estimate that the system lies at a distance of 1700 ± 300 pc. The high mass of the white dwarf and our finding that BT Mon was probably a fast nova together constitute a new piece of evidence in favour of the thermonuclear runaway model of classical nova outbursts. The emission lines are single-peaked throughout the orbital cycle, showing absorption around phase 0.5, high-velocity S-wave components and large phase offsets in their radial velocity curves. In each of these respects, BT Mon is similar to the SW Sex stars. We also find quasi-periodic flaring in the trailed spectra, which makes BT Mon a candidate intermediate polar.  相似文献   

9.
We present high- and medium-resolution spectroscopic observations of the cataclysmic variable BF Eridani (BF Eri) during its low and bright states. The orbital period of this system was found to be 0.270881(3) d. The secondary star is clearly visible in the spectra through the absorption lines of the neutral metals Mg  i , Fe  i and Ca  i . Its spectral type was found to be K3±0.5. A radial velocity study of the secondary yielded a semi-amplitude of   K 2= 182.5 ± 0.9 km s−1  . The radial velocity semi-amplitude of the white dwarf was found to be   K 1= 74 ± 3 km s−1  from the motion of the wings of the Hα and Hβ emission lines. From these parameters, we have obtained that the secondary in BF Eri is an evolved star with a mass of  0.50–0.59 M⊙  , whose size is about 30 per cent larger than a zero-age main-sequence single star of the same mass. We also show that BF Eri contains a massive white dwarf  ( M 1≥ 1.2 M⊙)  , which allows us to consider the system as a Type Ia supernova progenitor. BF Eri also shows a high γ-velocity  (γ=−94 km s−1)  and substantial proper motion. With our estimation of the distance to the system  ( d ≈ 700 ± 200 pc)  , this corresponds to a space velocity of ∼350 km s−1 with respect to the dynamical local standard of rest. The cumulative effect of repeated nova eruptions with asymmetric envelope ejection might explain the high space velocity of the system. We analyse the outburst behaviour of BF Eri and question the current classification of the system as a dwarf nova. We propose that BF Eri might be an old nova exhibiting 'stunted' outbursts.  相似文献   

10.
We report the discovery of a 7.3 M J exoplanet WASP-14b, one of the most massive transiting exoplanets observed to date. The planet orbits the 10th-magnitude F5V star USNO-B1 11118−0262485 with a period of 2.243 752 d and orbital eccentricity   e = 0.09  . A simultaneous fit of the transit light curve and radial velocity measurements yields a planetary mass of 7.3 ± 0.5 M J and a radius of 1.28 ± 0.08 R J. This leads to a mean density of about 4.6 g cm−3 making it the densest transiting exoplanets yet found at an orbital period less than 3 d. We estimate this system to be at a distance of  160 ± 20  pc. Spectral analysis of the host star reveals a temperature of  6475 ± 100 K, log  g = 4.07  cm s−2 and   v sin  i = 4.9 ± 1.0  km s−1, and also a high lithium abundance,  log  N (Li) = 2.84 ± 0.05  . The stellar density, effective temperature and rotation rate suggest an age for the system of about 0.5–1.0 Gyr.  相似文献   

11.
We present phase resolved optical spectroscopy and X-ray timing of the neutron star X-ray binary EXO 0748−676 after the source returned to quiescence in the autumn of 2008. The X-ray light curve displays eclipses consistent in orbital period, orbital phase and duration with the predictions and measurements before the return to quiescence. Hα and He  i emission lines are present in the optical spectra and show the signature of the orbit of the binary companion, placing a lower limit on the radial velocity semi-amplitude of   K 2 > 405 km s−1  . Both the flux in the continuum and the emission lines show orbital modulations, indicating that we observe the hemisphere of the binary companion that is being irradiated by the neutron star. Effects due to this irradiation preclude a direct measurement of the radial velocity semi-amplitude of the binary companion; in fact, no stellar absorption lines are seen in the spectrum. Nevertheless, our observations place a stringent lower limit on the neutron star mass of   M 1 > 1.27 M⊙  . For the canonical neutron star mass of   M 1= 1.4 M⊙  , the mass ratio is constrained to  0.075 < q < 0.105  .  相似文献   

12.
We present a Roche tomography reconstruction of the secondary star in the cataclysmic variable AE Aqr. The tomogram reveals several surface inhomogeneities that are due to the presence of large, cool star-spots. In addition to a number of lower latitude spots, the maps also show the presence of a large, high-latitude spot similar to that seen in Doppler images of rapidly rotating isolated stars, and a relative paucity of spots at a latitude of 40°. In total, we estimate that some 18 per cent of the Northern hemisphere of AE Aqr is spotted.
We have also applied the entropy landscape technique to determine accurate parameters for the binary system. We obtain optimal masses   M 1= 0.74 M⊙, M 2= 0.50 M⊙  , a systemic velocity  γ=−63 km s−1  and an orbital inclination   i = 66°  .
Given that this is the first study to successfully image star-spots on the secondary star in a cataclysmic variable, we discuss the role that further studies of this kind may play in our understanding of these binaries.  相似文献   

13.
We report the results of a high-time-resolution radial velocity study of the subdwarf B star and possible Type Ia supernova progenitor KPD 1930+2752. There were no significant peaks in the power spectrum of the velocity curve above our detection limit, about 4 km s−1, at the frequencies where peaks arising from pulsation were present in the photometric data of previous researchers. We report an orbital velocity amplitude,  348.5±1 km s-1  , in agreement with that reported by previous investigators. We find an orbital period of   P =0.095 093 08±0.000 000 15 d  based on our data and the ephemeris of Maxted et al.  相似文献   

14.
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   

15.
Using new and archival radio data, we have measured the proper motion of the black hole X-ray binary V404 Cyg to be  9.2 ± 0.3 mas yr−1  . Combined with the systemic radial velocity from the literature, we derive the full three-dimensional heliocentric space velocity of the system, which we use to calculate a peculiar velocity in the range 47–102 km s−1, with a best-fitting value of 64 km s−1. We consider possible explanations for the observed peculiar velocity and find that the black hole cannot have formed via direct collapse. A natal supernova is required, in which either significant mass  (∼11 M⊙)  was lost, giving rise to a symmetric Blaauw kick of up to ∼65 km s−1, or, more probably, asymmetries in the supernova led to an additional kick out of the orbital plane of the binary system. In the case of a purely symmetric kick, the black hole must have been formed with a mass  ∼9 M⊙  , since when it has accreted  0.5–1.5 M⊙  from its companion.  相似文献   

16.
We use updated data on distances and velocities of galaxies in the proximity of the Local Group (LG) in order to establish properties of the local Hubble flow. For 30 neighbouring galaxies with distances  0.7 < D LG < 3.0  Mpc, the local flow is characterized by the Hubble parameter   H loc= (78 ± 2) km s−1 Mpc−1  , the mean-square peculiar velocity  σv= 25 km s−1  , corrected for errors of radial velocity measurements  (∼4 km s−1)  and distance measurements  (∼10 km s−1)  , as well as the radius of the zero-velocity surface   R 0= (0.96 ± 0.03)  Mpc. The minimum value for σv is achieved when the barycentre of the LG is located at the distance   Dc = (0.55 ± 0.05) D M31  towards Andromeda galaxy (M31) corresponding to the Milky Way (MW)-to-M31 mass ratio   M MW/ M M31≃ 4/5  . In the reference frame of the 30 galaxies at 0.7–3.0 Mpc, the LG barycentre has a small peculiar velocity  ∼(24 ± 4) km s−1  towards the Sculptor constellation. The derived value of R 0 corresponds to the total mass   M T(LG) = (1.9 ± 0.2) 1012 M⊙  with  Ωm= 0.24  and a topologically flat universe, a value in good agreement with the sum of virial mass estimates for the MW and M31.  相似文献   

17.
We present and analyse the kinematics and orbits for a sample of 488 open clusters (OCs) in the Galaxy. The velocity ellipsoid for our present sample is derived as  (σ U , σ V , σ W ) = (28.7, 15.8, 11.0) km s−1  which represents a young thin-disc population. We also confirm that the velocity dispersions increase with the age of a cluster subsample. The orbits of OCs are calculated with three Galactic gravitational potential models. The errors of orbital parameters are also calculated considering the intrinsic variation of the orbital parameters and the effects of observational uncertainties. The observational uncertainties dominate the errors of derived orbital parameters. The vertical motions of clusters calculated using different Galactic disc models are rather different. The observed radial metallicity gradient of clusters is derived with a slope of   b =−0.070 ± 0.011   dex kpc−1. The radial metallicity gradient of clusters based on their apogalactic distances is also derived with a slope of   b =−0.082 ± 0.014   dex kpc−1. The distribution of derived orbital eccentricities for OCs is very similar to that derived for the field population of dwarfs and giants in the thin disc.  相似文献   

18.
In this paper we report on optical spectroscopic observations of the low-mass X-ray binary 2S 0921–630 obtained with the Very Large Telescope. We found sinusoidal radial velocity variations of the companion star with a semi-amplitude of  99.1 ± 3.1 km s−1  modulated on a period of 9.006 ± 0.007 d, consistent with the orbital period found previously for this source, and a systemic velocity of  44.4 ± 2.4 km s−1  . Owing to X-ray irradiation, the centre of light measured by the absorption lines from the companion star is probably shifted with respect to the centre of mass. We try to correct for this using the so-called K -correction. Conservatively applying the maximum correction possible and using the previously measured rotational velocity of the companion star, we find a lower limit to the mass of the compact object in 2S 0921–630 of   MX sin3 i > 1.90 ± 0.25 M⊙  (1σ errors). The inclination in this system is well constrained since partial eclipses have been observed in X-ray and optical bands. For inclinations in the range  60° < i < 90°  we find  1.90 ± 0.25 < MX < 2.9 ± 0.4 M⊙  . However, using this maximum K -correction we find that the ratio between the mass of the companion star and that of the compact object, q , is 1.32 ± 0.37, implying super-Eddington mass-transfer rates; however, evidence for that has not been found in 2S 0921–630. We conclude that the compact object in 2S 0921–630 is either a (massive) neutron star or a low-mass black hole.  相似文献   

19.
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   

20.
We show how the continuity equation can be used to determine pattern speeds in the Milky Way Galaxy (MWG). This method, first discussed by Tremaine & Weinberg in the context of external galaxies, requires projected positions, ( l , b ), and line-of-sight velocities for a spatially complete sample of relaxed tracers. If the local standard of rest (LSR) has a zero velocity in the radial direction ( u LSR), then the quantity that is measured is  Δ V ≡Ωp R 0- V LSR  , where Ωp is the pattern speed of the non-axisymmetric feature, R 0 is the distance of the Sun from the Galactic centre and V LSR is the tangential motion of the LSR, including the circular velocity. We use simple models to assess the reliability of the method for measuring a single, constant pattern speed of either a bar or spiral in the inner MWG. We then apply the method to the OH/IR stars in the ATCA/VLA OH 1612-MHz survey of Sevenster et al., finding  Δ V =252±41 km s-1,  if   u LSR=0  . Assuming further that   R 0=8 kpc  and   V LSR=220 km s-1,  this gives  Ωp=59±5 km s-1 kpc-1  with a possible systematic error of perhaps 10 km s−1 kpc−1. The non-axisymmetric feature for which we measure this pattern speed must be in the disc of the MWG.  相似文献   

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