Spectroscopic and photometric observations of Nova Aquilae 1982

Nova Aquilae 1982 was observed spectroscopically and photometrically in January, February, and April 1982. The results of these observations including those obtained a few days after the discovery, are presented.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Spectroscopic and photometric observations of the eclipsing star UV Leo

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.     

B,V, and DDO photometric observations of red variable stars

Light curves of the red variables L₂ Puppis, R Carinae, and S Carinae in the region of the spectrum covered by theB, V, and DDO photometry are presented. The behavior of the DDO color indices and their meaning for this type of star are discussed. S Carinae shows a different behavior from the other two stars that seems to be due to a population effect.     

Spectroscopic and photometric studies of the magnetic cataclysmic variable EU UMa (=RE1149+28)

We present the optical observations of the AM Herculis system EU UMa (=RE1149+28) carried out in February 1993 with a TV scanner and a photometer (NEPh) at the secondary focus of the 6-m Special Astrophysical Observatory telescope. Spectroscopy with a time resolution of 300 s and a spectral resolution of 2 Å in the wavelength range ≈3950–4950 Å is used to analyze the variability of emission-line profiles, equivalent widths, central intensities R_c, and radial velocities with orbital phase. We determined the orbital period of the system from line radial-velocity measurements, 90.0±0.2 min. The emission-line profiles are highly variable. The Hβ and He II 4686 Å lines exhibit P Cyg profiles at selected phases. The spectral-line parameters were found to vary significantly on time scales from 5 to 15 min. The possible causes of the detected spectroscopic variability are discussed.     

Spectroscopic and photometric study of the contact binary BO CVn

We present the results of the study of the contact binary system BO CVn. We have obtained physical parameters of the components based on combined analysis of new, multi-color light curves and spectroscopic mass ratio. This is the first time the latter has been determined for this object. We derived the contact configuration for the system with a very high filling factor of about 88%. We were able to reproduce the observed light curve, namely the flat bottom of the secondary minimum, only if a third light has been added into the list of free parameters. The resulting third light contribution is significant, about 20–24%, while the absolute parameters of components are: M₁ = 1.16, M₂ = 0.39, R₁ = 1.62 and R₂ = 1.00 (in solar units).The O-C diagram shows an upward parabola which, under the conservative mass transfer assumption, would correspond to a mass transfer rate of dM/dt = 6.3 × 10^?8M_⊙/yr, matter being transferred from the less massive component to the more massive one. No cyclic, short-period variations have been found in the O-C diagram (but longer-term variations remain a possibility).     

Polarimetric and photometric observations of long-period variables

Observations of 35 long-period variables have been done mainly at the Byurakan Astrophysical Observatory during the last years. A polarimetric monitoring of 34 stars has been carried out with simultaneous photometric measurements for some of them. Photometric data in the UBVR bands have been obtained for the star Y Ori, which is the faintest one. The results show that the degree of light polarization is correlated with the period and brightness of these stars. This indicates that the degree of light polarization is connected with the mass loss as well. Finally the photoelectric observations of the stars Y Ori, T Cep, R Gem, and R Boo show a short-term increase of their brightness in the decreasing branch of their light curves. The measured (U-B) or (B-V) colors of detected rapid variations are bluer than the colors of the star measured before these events. It is supposed that the change of polarization with time, the relatively blue colors of miras near their minimum brightness, and the colors of detected rapid variations may be explained by the influence of a invisible blue companion, as in the case of the star R Aqr. Published in Astrofizika, Vol. 42, No. 3, pp. 341–350, July–September, 1999.     

Spectroscopic far ultraviolet observations of transition zone instabilities and their possible role in a pre-flare energy build-up

(1) Highly flare-productive new emerging active regions are characterized by numerous small low-lying loops which frequently show a chaotic pattern. (2) Flare activity in such a region subsides as the chaotic loop structures relax and expand into a bipolar configuration. (3) The transition zone in such an active region is highly unstable as shown by broadened and shifted non-thermal line profiles of medium ionized elements like Si iii, Si iv, C iv, etc. (4) These transition zone instabilities which occur as isolated events in active regions of low flare productivity are often observed prior to flares. (5) Transition zone instabilities can be traced to the footpoints of active loops, and seem to be accompanied by heating of the loop. (6) The loops vary in size and show differing degrees of activity, with the brightest and most compact ones seemingly being in a pre-flare state which results in the catastrophic energy release along the loop during a flare.     

Polarimetric and photometric observations of the star m cephei

The results of photometric and polarimetric observations of the star Μ Cep at Byurakan Observatory are presented. Some interesting correlations between the parameters of the star’s brightness variation and the degree of polarization of the light are obtained. It is suggested that the recorded rapid changes in the degree of polarization may result from Μ Cep being a double star. Translated from Astrofizika, Vol. 43, No. 2, pp. 219-228, April–June, 2000.     

Spectral and photometric observations of the star Y Ori

Data are presented from a spectral and photometric study of the long-period variable star Y Ori, which we have classified as a type M7IIIe near its brightness minimum. In the blue part of the spectrum, features from a star of an earlier spectral class are superimposed on the spectrum of a cool giant, so that a variable excess emission is observed at wavelengths of 4000–4200 Å. As opposed to the monotonically decreasing intensity of the Balmer lines (EWHα > EWHβ > EWHγ > EWHδ) in normal stars belonging to the earlier spectral classes, a reverse relationship, with EWHγ < EWHδ is detected in Y Ori. Translated from Astrofizika, Vol. 51, No. 4, pp. 567–575 (November 2008).     

Multi-color photometric observations of facular contrasts

We have studied the modulational stability of a finite-amplitude fast sausage magnetosonic surface wave traveling along a thin magnetic slab in the solar photosphere (chromosphere). The equation governing the evolution of the fast-wave envelope modulated by a slow wave driven by the ponderomotive force proves to be the cubic nonlinear Schrödinger equation which in photospheric conditions admits only dark envelope soliton solutions. The possibility of the existence of such solitary waves in the solar atmosphere is discussed.     

The photometric observations of ER vulpeculae: photometric analysis with the W-D code

The photometric observations of ER Vul were obtained in UBV light in 1994, at Birouni Observatory, University of Shiraz, Iran. The three light curves, which are almost complete, have been analyzed separately by means of Wilson and Devinney method (1971). The light curves include proximity effects, wave-like distortions, mutual eclipses, and short term light fluctuations. The appropriate value of the mass ratio of this system was found after extensive searches. ER Vul has a detached configuration where the two components are very nearly fill their Roche lobe. ER Vul has the characteristic of a RS CVn type system. The absolute dimensions for the primary and secondary of this system were calculated from its spectral types and by combining the photometric solution with inferred component radial velocities (Northcott and Bakos, 1967).     

Eclipse observations in the rocket ultraviolet

An Aerobee 150 was launched into the umbra from Wallops Island at 18:36:15 UT 7 March, 1970, carrying two intensity calibrated EUV Wadsworth grating spectrographs. The experiment was a collaborative venture between groups from A.R.U. Culham, H.C.O., Imperial College and York University, Toronto. This was the first attempt to record stigmatic spectra of the chromosphere and corona in the EUV, analogous to the visible eclipse Flash Spectrum.A wealth of new observational data has demonstrated the importance of a new instrumental and experimental technique for recording the ultraviolet flash spectrum. Lyman- limb spectroheliograms reveal complex activity extending high into the corona in contrast to the modest level of activity observed in H. Preliminary intensity reduction shows that Lyman- dominates as the principle radiation loss for these features.     

Spectrometric and photometric study of the eclipsing variable AM Leo

The results of quasi-simultaneous spectroscopic and photometric observations of a W UMatype eclipsing variable star AM Leo are presented. The observations were carried out with a 1.2-m telescope equipped with a high-resolution echelle spectrometer, and a telescope-reflector (D = 0.45m) of the Kourovka Astronomical Observatory of Ural Federal University. New values of semi-amplitudes of the radial velocity curves of the components, K₁ = 109.6kms^?1 and K₂ = 252.4kms^?1 and the systemic radial velocity V₀ =-9.3 kms^?1 are obtained, comparable to the data published in the literature. The semi-amplitude of the radial velocity curve of a more massive component K₁ and the mass ratio of the components q = 0.412 appeared to be slightly smaller than the values obtained by other authors. An assumption wasmade that a possible reason of this is the presence of hot and/or cold spots on the surface of the components, shifting the effective center of brightness of the visible disk of the component with respect to its center of mass position. It was shown that the AM Leo light curve variations on the time scales of one and more days, registered within the photometric part of the study may be described by the choice of appropriate model of the spot structure.     

Spectroscopic and photometric characteristics of stars in the field of the cluster vdB 130

The observational data for 24 stars toward the young cluster vdB 130 are analyzed. The spectroscopic and photometric BV RIJHK observations have been carried out with the following telescopes: 6-m at the Special Astrophysical Observatory of the Russian Academy of Sciences, 60-cm at the Southern Station of the Moscow State University, and 2.5-m at the Caucasus Observatory of the Sternberg Astronomical Institute of theMoscow State University. Nine stars previously selected as cluster members have been found to belong to different subtypes of type B. A minimum color excess toward the cluster, E(B ? V) = 0.9 mag, has been revealed for the vdB 130 stars lying outside the molecular cloud. Maximum color excesses, E(B ? V) = 1.3?1.4 mag, have been found in the spectra of cluster stars 1r and 5r observed in dust blobs. Inside the cluster R _v is shown to differ from the standard one. The overwhelming majority of the remaining investigated stars belong to late types and have minor color excesses (≤0.3) typical of close distances.     

Positional and photometric CCD observations of the comet Shoemaker-Levy 9

Positional and photometric CCD observations of the comet Shoemaker-Levy 9 fragments were carried out at the Abastumani Astrophysical Observatory. Up to 15 named fragments were detected and their equatorial coordinates and magnitudes are reported. CCD frames were processed using DAOPHOT II. The internal precision of reference star positions down to 18^m is 0.″7 and the mean error of photometry does not exceed ±0.3 mag.