Direct detection of the secondary spectrum of the interacting eclipsing binary TX UMa

Eclipsing binary TX UMa was observed with the D.A.O. high-dispersion spectrographs in 1969–1970, with emphasis on the detailed coverage of the primary minimum. One spectrum was taken exclusively within totality, thus exhibiting an uncontaminated spectrum of the secondary component. This leads to spectral reclassification of the secondary (F6 IV). The narrowing of the line profile of the H-line in totality is interpreted in terms of synchronous rotation of the secondary (v sini80 km s^–1) while the primary rotates faster (v sini130 km s^–1) than synchronously (v sini50 km s^–1). Although the secondary does not fill in its Roche lobe fully, the system exhibits pronounced indications of rather strong physical interaction. This is now supported also by the profound changes of the line profiles of the H-line with phase.     

The application of a Bessel transform to the determination of stellar rotational velocities

A method for analysing line profiles by means of a transform using Bessel functions is described. This yields the stellar rotational velocityv sini, to an accuracy of about ±1 km s^–1 for rotational velocities greater than about 5 km s^–1, provided that rotation is the major source of line broadening. The theory of the method is a special case of a general theory of linear transforms in data analysis, which is outlined in an appendix.     

Radial velocity measurements of the spectra of Zeta Aurigae outside eclipses

Radial velocities of both components of Zeta Aurigae have been measured on 39 grating spectra obtained in the interval February 1970-November 1981.The evaluation of the orbital elements of the primary component confirmed, the elements observed so far. The velocity variation of the secondary component has been determined according to the method described by Popper (1961) yieldingK _B=30.57±5.97 (m.e.) km s^–1. The masses of the components were found to beM _K sin³ i=6.4±1.7 andM _B sin³ i=4.5±0.9 solar masses. With the elements obtained a radial velocity curve of the B-star has been calculated. Comparison of the radial velocities derived from the hydrogen lines of the B-star with the calculated radial velocity curve shows systematic deviations which indicate that these lines originate partly in an expanding circumstellar envelope of the system. The main constituent of the envelope must be neutral hydrogen of high density. Variations of the radial velocities indicate density variations due to condensations inside this envelope.     

V792 Her=HD 155638: A totally eclipsing RS CVn binary

Photometry of HD 155638=V792 Her has been analyzed to determine the elements of this totally eclipsing RS CVn binary. The light variation outside eclipse was found to have a period of 27^d.07±0^d.07, which is slightly different from the 27^d.5384±0^d.0045 orbital period. Analysis of the eclipses was achieved by a modification of the Russell-Merrill technique. With the aid of radial velocity measures, absolute elements were obtained for the hot and cool stars, respectively;R _h=2.58R ,R _c=12.28R ,M _h=1.40M ,M _c=1.46M ,i=80^o.61 and velocity semi-amplitudesK _c=48.36 km s^–1±0.79 km s^–1, andK _h=50.50 km s^–1±0.33 km s^–1. The apparent magnitudes areV _h=9 ^m .73 andV _c=8 ^m .48. The distance to HD 155638 was estimated to be 310 parsecs.     

Stellar atmospheric velocity fields: The Beta Cephei variables γ Peg and β Cep

The shape parameters of a number of selected ultraviolet lines in BUSS-spectra of the Beta Cephei stars Peg and Cep have been analyzed to determine the principal parameters of the atmospheric velocity field. We find for both stars a fairly high value (5 km s^–1) for the microturbulent line-of-sight velocity component, which confirms an earlier result based on lower resolution UV spectra. Macroturbulent and rotational velocities are virtually zero in the atmosphere of Peg; for Cep we findv _rotsini=40 km s^–1.On leave from Akita University, Akita, Japan.     

‘Prominences’ of RY Tauri

High-resolution spectroscopic monitoring of the Nai D lines in the T Tau-type star RY Tau results in the discovery of relatively cool gas clouds ascending and descending inside the stellar wind on a time-scale of few days and co-rotating with the star. Radial velocity of the clouds varies from –100 to +100 km s^–1, which is twice as large as thev sini of the star.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

Brightness distribution of diffuse soft X-rays

The brightness distribution of diffuse soft X-rays in the pulse height range 0.15–0.3 keV (L-band) and 0.5–0.8 keV (M-band) are obtained over a quarter of the sky centered at the galactic anticenter with 1.5 m polypropylene window proportional counters on board a sounding rocket. In theL-band three enhanced regions are noticed on the map. They coincide with the northern and southern Hi holes and the inner part of the galactic radio Loop II.In the northern Hi hole theN _H dependence of theL-band flux and the hardness ratioM/L can be fitted with a local hot plasma model with the absorption by a low velocity neutral hydrogen gas (|V|<25 km s^–1) along the line of sight. The X-ray feature of Loop II is similar to that of Loop I. In the lowN _H region (<3×10²⁰ H atoms cm^–2) theM/L value is lower than 0.3, whereas it varies in the range 0.1–0.4 at low latitudes (|b|<30⁰). This fact seems to be interpreted in terms of a model that a number of hot plasma clouds contribute to X-ray emission.     

Radial velocity measurements of the chromospherically-active stars (II)

From two sets of the spectroscopic observations covering a ten year period we have obtained 59 radial velocities of the chromospherically-active star HD 28591 = V492 Per. It is a G9III single-lined spectroscopic binary with a period of 21.2910 days and a circular orbit. Thev sini of 24.6 km s^–1, results in a minimum radius 10.3R . We estimate a distance of 165 ± 40 pc and an orbital inclination of 65 ± 25 degrees. The secondary is probably a mid to late-type K dwarf. The star is brighter than the limiting magnitude of theBright Star Catalogue. The mean photometric and the orbital periods are identical within their uncertainties. Since the star fills a significant fraction of its Roche lobe, about 62%, the photometric light curve may be the result of starspots and a modest ellipticity effect.Visiting astronomer, Kitt Peak National Observatory, NOAO, operated by AURA, Inc., under contract with the NSF     

Correlation and variability of the HeI 4471 and MgII 4481 absorption lines in Be stars: A possible diagnostic tool for nonradial pulsations

In a total of 181 photographic spectrograms, obtained at the Manuel Foster Observatory of the Catholic University in Santiago (Chile), the equivalent widths of the absorption lines HeI 4471 and MgII 4481 have been determined for 10 selected southern Be stars and 4 normal B-type stars. The mean equivalent widths of each star are compared to published mean values from largers samples of B stars. On the average, Be stars coincide with normal B-type stars in their equivalent width. However, a striking difference between rapidly and slowly rotating stars in their line ratios (HeI/MgII) was found, which is probably an artifact due to a systematic misclassification of spectral types of rapidly rotating B stars (v sini>200 km s^–1). Six of the ten Be stars show evidence for variability in HeI and/or MgII with time-scales shorter than a few days and amplitudes up to a factor 2 in equivalent width. Line variability occurs in the entire range of projected rotation velocity (70 km s^–1<v sini<350 km s^–1), but seems to be restricted to spectral types B2-B4. In addition, variations at longer time-scales (years) were observed in two cases. Three of the variable stars (HR 4074, HR 4537, and Ara) present correlated variations in both lines, one ( Cen) anti-correlated variability. We interpret our results in terms of nonradial pulsations and stress the importance to study the HeI/MgII lines and their variability in a larger sample of Be, Bn, and normal B stars, including archival material in order to follow-up line variability for several decades in the past.     

Der offene sternhaufen NGC 6067

The open star cluster NGC 6067 was investigated by the strip method on charts of photographs with different exposure times taken with the 1-m Schmidt telescope of the European Southern Observatory. Because of the large distance (1820 pc) of the cluster its luminosity function is known up to date only betweenM _v =–4.5 andM _v =+1.5. In this paper it is continued toM _v =4.4 and further extrapolated by means of 2 variants. The cluster contains 419 respectively 476 stars with total masses of 1453 resp. 1483. On account of its radius of 5.9 pc the cluster is a rather extended object, which can be described by the generalized density law of Schuster withn=4.42 and the central star density 8.9 stars pc^–3. The mean velocity of the stars amounts to 1.03 km s^–1, the massbrightness relation is 0.031 in solar units.

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Mitteilungen Serie A.     

Luminosity and colour distribution in the interacting system NGC 7770-71

Detailed surface photometry for the SB(s)a galaxy NGC 7771 has been carried out in the blue spectral band. Isophotes, luminosity profiles, and photometric parameters are obtained from photographs collected with the 74 inch telescope of Kottamia Observatory, Egypt. The total apparent magnitudem _T =13.08 with maximum dimensions 3.6±0.5×2.7±0.5 (at threshold µ _m = 27.38 mag s^–2). The absolute magnitude isM _T =–21.70 if the distance is =90.2 Mpc. The major axis is in position angle =69°.5±1° and the mean axis ratio of the outer regionsq=b/a=0.45 corresponds to an inclinationi=66°. The equivalent effective radiusr _e ^* =0.29 and the effective surface brightness µ _e = 22.30 mag s^–2.The equivalent luminosity distribution has been decomposed into two main components, anr ^1/4 spheroid and an exponential disk. The total apparent magnitudes of the spheroidal and disk components are 14.36 and 13.48, which correspond to contributions of 31 and 69% to the total blue luminosity, respectively.     

The evidence for clumpy accretion in the Herbig Ae star HR 5999

Analysis of IUE high- and low-dispersion spectra of the young Herbig Ae star HR 5999 (HD 144668) covering 1978–1992 has revealed dramatic changes in the Mg II h and k (2795.5, 2802.7 Å) emission profiles, changes in the column density and distribution in radial velocity of accreting gas, and flux in the Ly, OI and CIV emission lines, which are correlated with the UV excess luminosity. We also observe variability in the spectral type inferred from the UV spectral energy distribution, ranging from A5 IV-III in high state to A7 III in the low state. The trend of earlier inferred spectral type with decreasing wavelength and with increasing UV continuum flux has previously been noted as a signature of accretion disks in lower mass pre-main sequence stars (PMS) and in systems undergoing FU Orionis-type outbursts. Our data represent the first detection of similar phenomena in an intermediate mass (M 2M ) PMS star. Recent IUE spectra show gas accreting toward the star with velocities as high as +300 km s^–1, much as is seen toward Pic, and suggest that we also view this system through the debris disk. The absence of UV lines with the rotational broadening expected given the optical data (A7 IV,v sini = 180 ± 20 km s^–1) for this system also suggests that most of the UV light originates in the disk, even in the low continuum state. The dramatic variability in the column density of accreting gas, consistent with clumpy accretion, such as has been observed toward Pic, is a hallmark of accretion onto young stars, and is not restricted to the clearing phase, since detectable amounts of accretion are present for stars with 0.5 <t _age < 2.8 Myr. The implications for models of Pic and similar systems are briefly discussed.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A.     

The nature of RW Sextantis

Photometry and first results of extensive CCD-spectroscopy of the UX UMa system RW Sex are presented. The period is found to be P=0.24486 days and the semi-amplitude of the radial velocity is K₁=101 km s^–1. The mass of a Roche-lobe filling secondary is M₂=(0.54±0.09) M₀ and, for M₁M₂, the mass ratio is M₁/M₂=1.5±0.5. The accretion rate is about (2–3) 10¹⁷ g/s. The model for RW Sex by Greenstein and Oke is discussed and rejected.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

High-dispersion spectroscopy of the symbiotic star AX Per: A binary model with rapid mass accretion

Results of high-dispersion spectroscopy (10 Å mm^–1) of the symbiotic star AX Per carried out in the years from 1979 to 1987 are reported. The emission line [FeVII] 6086 consists of a narrow and a broad component; the radial velocity of the narrow one varies according to the photometric period 681.6 days. This variation (K=30.6±1.5 km s^–1) seems to be due to the orbital motion of the hot star. The radial velocity of absorption lines varies with an inverse phase dependence and a much smaller amplitude (K=5.6±2 km s^–1), which may reflect the orbital motion of the red giant. The variation of the radial velocity of the emission lines of FeII, ect. (K=6.7±1.5 km s^–1) might be due to the rotation of the red giant. The profile of H emission line suddenly changed around the phase of the photometric minimum, which could be explained as a result of an eclipse of the emitting region by the red giant. On the other hand, some problems remain open in the behaviour of the radial velocities of H and HeI 5876.The observed results support a binary model of AX Per consisting of a rather massive (3M ) M-type giant and a Main-Sequence star (0.6M ). AX Per seems to be in an early stage of the Case C mass transfer, and the estimated very high mass accretion rate (10^–4 M yr^–1) is consistent with the theoretical models. The narrow component of the emission line of [FeVII] 6086 might be emitted in radiatively driven polar jets on the hot star of which luminosity is close to the Eddington limit.A new identification as ZrII at 6106.47 Å is proposed for the emission line at 6106 Å.     

Damping constant and turbulence in the solar atmosphere

In the region of the formation of weak and medium-strong lines, the microturbulence increases with height (V _ver=0.7–0.9 km s^-1, V _hor= 1.1–1.5 km s^-1), the macroturbulence decreases (V _ver=1.6–1.4 km s^-1, V _hor= 2.4–1.5 km s^-1), and the total velocity field (vertical component) is depth-independent (1.7 km s^-1). The empirical damping constants for Fe, Ti, Cr, Ni lines are equal 1.3₆, 1.7₆, 1.6₆, 1.6₆, respectively. The correlation length (the Kubo-Anderson process has been used) in the solar photosphere is 520–550 km.     

The height variation of granular and oscillatory velocities

Previous observations of spatially-resolved vertical velocity variations in ten lines of Fe i spanning the height range 0 h 1000 km are re-analyzed using velocity weighting functions. The amplitudes and scale heights of granular and oscillatory velocities are determined, as well as those of the remaining unresolved velocities. I find that the optimal representation of the amplitude of the outward-decreasing granular velocities is an exponentially decreasing function of height, with a scale height of 150 km and a velocity at zero height of 1.27 km s^–1. The optimal representation of the same quantities for oscillatory velocities is an exponential increase with height, with a scale height of 1100 km and a velocity at zero height of 0.35 km s^–1. The remaining unresolved velocities decrease with height, with a scale height of 380 km and a velocity at zero height of 2.3 km s^–1.     

Solar surface velocity fields determined from small magnetic features

We describe a method for the analysis of magnetic data taken daily at the Vacuum Telescope at Kitt Peak. In this technique, accurate position differences of very small magnetic features on the solar surface outside active regions are determined from one day to the next by a cross-correlation analysis. In order to minimize systematic errors, a number of corrections are applied to the data for effects originating in the instrument and in the Earth's atmosphere. The resulting maps of solar latitude vs central meridian distance are cross-correlated from one day to the next to determine daily motions in longitude and latitude. Some examples of rotation and meridional motion results are presented. For the months of May 1988 and October–November 1987, we find rotation coefficients A = 2.894 ± 0.011, B = - 0.428 ± 0.070, and C = -0.370 ± 0.077 in rad s^–1 from the expansion = A + B sin² + C sin⁴, where is the latitude. The differential rotation curve for this interval is essentially flat within 20 deg of the equator in these intervals. For the same intervals we find a poleward meridional motion a = 16.0 ± 2.8 m sec ^-1 from the relation v = a sin, where v is the line-of-sight velocity.Operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.     

The internal motion of quiescent prominences

A study has been made of fine structure wavelength shift in the K line spectra from quiescent prominences. A persistent small scale motion is found in the prominence main body. In places where we see the characteristic thread like fine structure in the accompanying H filtergrams the average line-of-sight velocity amplitude is about 1 km s^–1. A higher velocity ( 4 km s^–1) is associated with a slightly coarser, mottled prominence fine structure. In the low lying regions, connecting the prominence body and the chromosphere, we do not detect any fine structure line shift (v 1/2 km s^–1).     

A quantitative analysis of the prototype [WCL] star CPD-56° 8032

We present a detailed, quantitative study of the standard [WC10] Wolf-Rayet central star CPD-56^o 8032 based on new high resolution AAT UCLES observations and the Hillier (1990) WR standard model. Our analysis of CPD-56^o 8032 gives the wind properties (T _*=34500K, lg (L/L )=3.8, lg (M/M a^–1)=–5.4,v =225 km s^–1) and chemistry (C/He=0.5, O/He=0.1, by number), the latter suggesting an intimate relationship with the Ovi PN central stars and the PG 1159-035 objects. A comparison between the wind properties of CPD-56^o 8032 and Sk-66^o 40 (WN 10) indicates that low excitation, low wind velocity WR winds are common to both low mass PN central stars (WC sequence) and high mass post-LBV's (WN sequence).     

Collapse of the presolar nebula

The hydrodynamical axially symmetric collapse of a 3M -cloud with an initial density of 10^–20 g cm^–3 has been investigated. In order to first arrive at an equilibrium configuration a temperature of 15 K has been assumed. During about 9 free-fall times the cloud has artificially been cooled down to the (Jeans-) critical temperature of 8 K. Thus, the dynamical collapse studied in this paper starts from an equilibrium configuration following a slow quasi-hydrostatic contraction. Two sequences corresponding to a different choice of the initial angular velocity _i = 10^–14 s^–1 (Case A) and _i = 10^–15 s^–1 (Case B) have been computed. In both cases a fast spinning, optically thick disk-like core of low mass and temperature forms for which fission into two or even more pieces is very likely to occur.Paper presented at the Conference on Protostars and Planets, held at the Planetary Science Institute, University of Arizona, Tucson, Arizona, between January 3 and 7, 1978.