Two-colour photoelectric investigation of AR Lacertae

The RS CVn-type eclipsing binary AR Lac has been observed in two colours,B andV, in 1978 and 1979. Several times of minima have been obtained during the observations and the new light elements have been calculated. The orbital period of the system was found to be decreasing with an amount of 14.6 s century^–1.The light curves of the system obtained inB andV show a significant wave-like distortion outside eclipses. The amplitudes of the wave-like distortion inB andV are about 0 _. ^m 09 and 0 _. ^m 10 in 1978, and, 0 _. ^m 12 and 0 _. ^m 13 in 1979, respectively. The minima of the wave-like distortion have shifted with an amount of 0 _. ^p 40 in one year, thus indicating the migration period of the wave-like distortion is about 2.5 yr.A noticeable variation of light during the totality of primary minimum has also been observed. This variation can be attributed to the distortion wave which has been moving towards decreasing phases.     

BV observations of the eclipsing binary WX Eridani

Photoelectric observations of WX Eridani inB andV filters have been discussed. The maximum magnitudes of the system areB=9 ^m .70 andV=9 ^m .46. TheB-V colours of the components are 0 ^m .16 and 0 ^m .80 for the primary and the secondary, respectively, while their spectral types are A5+K0. The period has been found to be constant and its revised value is 0^d.823 270 76.     

UBV photometry of ER Vulpeculae

UBV photometry of RS CVn-type eclipsing binary system ER Vulpeculae has been presented. The period comes out to be 0 _. ^d 698093. The average depths of primary and secondary minima are, respectively, 0 _. ^m 21 and 0 _. ^m 12. The colours at various phases have been given. A dip is seen around phase 0 _. ^p 73 as was seen in the observations of Arevaloet al. (1988). Large scatter is present in the observations as noticed earlier, and may be due to activity of the components.     

CF octantis,an RS CVn-type variable with a prominent activity cycle

Photoelectric photometry has been obtained for CF Octantis on 39 nights. The object is a member of the RS CVn class and has a highly active chromosphere. A 20.15 ±0.06 d period has been found from theB andV magnitudes, which is interpreted as the rotational modulation of the light from a non-uniformly spotted star. The amplitude of this spot wave is observed to vary slowly between ΔV about 0^m.l and 0^m.3, which may be evidence for an activity cycle of 9 ±3 years.     

An expanding high velocity hi cloud probably ejected from the galactic nucleus

An object located approximately atl=8°,b=–4° with a mean radial velocity of –212.3 km s^–1 has been observed in the 21 cm neutral hydrogen line. The mean weighted velocity dispersion is 11.2 km s^–1 and the total mass is estimated to be 190R ² (kpc) solar masses. We discuss possible interpretations of the origin and nature of this object. The most likely interpretation is that we observe an expanding object which has been ejected from the galactic nucleus.     

The predicted 1s 2-1s6p H− auto-ionization resonance observed as a diffuse interstellar line at 7581 Å

The 1s ²-1s6p H^– auto-ionization resonance has been observed as a diffuse interstellar line in several highly reddened O and B stars. The identification based on its wavelength has been confirmed by its equivalent width in HD 183143. The addition of the 1s ²-1snp diffuse-line series raises the total H^– oscillator strength of absorption to a value close to 2.     

Photoelectric observations of the flare star BD + 55° 1823

A light variation in Johnson'sV-band of flare star EV Lac has been registered by Pettersen (1980). The cycle length was 4 _. ^d 378 with amplitude about 0 _. ^m 07. A Fourier analysis programme has been applied on our measured data of the flare star BD+55°1823 in Johnson'sV andB bands. A period of 16^d and amplitude of 0 _. ^m 14 have been detected in theV-band.     

Excitation mechanism ofNi 5199 Å lines in the day Airglow

Production rates of N(² D) metastable atoms in the daytime atmosphere have been calculated for different possible processes, using positive ion composition and reaction rate data, available presently. Emission rates of the 5199 Å doublet of Ni are calculated by separately and jointly considering the deactivation of N(² D) atoms by electrons and molecular oxygen.From a comparison of the computed results with the observational data, an attempt has been made to identify the processes of importance to the production and deactivation of N(² D). For further confirmation of the proposed mechanism the variation of integrated intensity of this radiation with solar activity has been obtained. The calculated values may be compared with intensity data obtained in future at different levels of solar activity.     

Integrated luminosity distribution of Galactic open clusters

The integrated magnitudes of 221 Galactic open clusters have been used to derive the luminosity function. The completeness of the data has also been discussed. In the luminosity distribution the maximum frequency of clusters occurs nearI (M_v) = −3 _m ^. 5, and some plausible reasons for a sharp cut-off atI (M_v) = −2^m. 0 have been discussed. It is concluded that the paucity of the clusters fainter thanI (M _v) = −2 _m ^.0 is not purely due to selection effects. The surface density of the clusters for different magnitude intervals has. been obtained using the completeness radius estimated from the logN- logd plots. A relation betweenI (M^v) and surface density has been obtained which yields a steeper slope than that obtained by van den Bergh & Lafontaine (1984).     

Photoelectric study of AW UMa

UBV photoelectric photometry of the eclipsing binary system AW UMa has been presented. A slightly improved period of 0 _. ^d 4387304 has been given. The colour of the system has been discussed. Eccentricity is present in the system. Light and colour curves show that intrinsic light variations may be present in the system. The presence of mass transfer is a possibility.     

Five years of photometry ofσ geminorum

Five years of photoelectric photometry of this bright K1 III RS CVn binary has been obtained at thirteen different observatories. Except for one year, the light curve has shown two minima, separated by roughly a half cycle. At the epoch of discovery (1977.2) one minimum was shallower but as of 1980.2 the two became comparable in depth. During the 1979–80 season the light curve changed shape rapidly, the shallower minimum becoming as deep as the other within about 80 days or perhaps less. Times of both minima can be fit with a photometric period of 19 ^d .423, which is 0.9% shorter than the 19 ^d .603 orbital period. The overall brightness range during the five years has been 4 ^m .13<V<4 ^m .29.Guest Observer, Kitt Peak National Observatory, operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation.     

Spectral-luminosity classification,colour variations and suspected beta canis Majoris-type variability in IZ Persei

The colour indices and the spectrum-luminosity classification of the eclipsing binary system IZ Persei have been presented for the first time. The colour indices of the system appear reddened. Applying the interstellar reddening corrections, the spectral-luminosity classes of the primary and the secondary components of IZ Per come out to be B2.5III-V and B5III-V, respectively. The averageB-V andU-B colour excesses come out to be 0 ^m .4 and 0 ^m .2, respectively. The colour indices show continuous variation throughout the cycle, and indicate the presence of intrinsic variability. Tentative analysis suggests that the primary component of IZ Per is a Beta Canis Majoris-type variable. The possibility of a shell has also been discussed.     

Second order rotational effect on the oscillation frequencies of V1162 Ori

V1162 is a δ-Scuti type variable star for which a rotational velocity of V  sini=46±4 km s⁻¹ has been observed. The star has been modelled according to its observed parameters and oscillation frequencies. The results obtained by approximating rotation to the first order have been compared with the ones provided by new calculations that include rotation up to the second order. We found that second order rotation term should be included in frequency calculations for comparatively high rotation speeds.     

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.     

Investigation of the Mg XII 8.42 Å doublet in solar flare spectra

The intensity ratio of the components of the Mg xii 8.42 Å (1s ² S _1/2 – 2p ² P _{1/2, 3/2}) doublet in solar flare spectra has been investigated using observations recorded from the Intercosmos 7 satellite. The observed values of the ratio fall within the interval 0.38–0.66 and have been compared with recent theoretical predictions based on an optically thin collisional-radiative model. It has been found that for the flare plasma the low values of the ratio cannot be explained since they fall below the smallest theoretical value. The highest values on the other hand require that an unacceptably high electron density be postulated. It is suggested that both high and low values may be caused by the resonance line scattering of the Mg xii quanta in the flare volume, provided that the volume is elongated and not spherical.The intensity of the nearby satellite lines is also investigated. Good agreement between the theoretical and observed intensities is found.     

Gravitational collapse of cosmic gas clouds and formation of star clusters

In this paper the gravitational collapse of cosmic gas clouds and formation of star clusters has been considered. Hoyle's view of successive fragmentation has been taken as the basic mechanim in the present work. The initial masses of protostars have been estimated as the function of their distances from the centre of the cluster and the intensity of the magnetic field of the medium. It has been shown that the fragmentation process is greatly inhibited by the presence of a strong magnetic field. A model has been constructed showing how a protostar grows in mass by accretion from the surrounding medium, on the basis of the assumption that as the star moves at random in the cluster it picks up a fraction of the material through which it passes. It has been estimated that a protostar of initial mass of about 0.1M grows to one of 1.0M in a time period which ranges from a few multiples of 10⁵ to a few multiples of 10⁷ yr, depending on the parameters involved in the accretion process. The number of stars per unit mass range has also been estimated; it is found to be proportional tom ^–3.3,m being the mass of the star.     

Fluctuation theory of the mass flux from the stars: Amplifications

Two critical points in an earlier paper on this theory are further discussed. The first is related to the physical average of the stochastic force driving the mass flux. A more accurate estimate has been made of the mean mass loss, viz. 0.40L ^3/2(R/M)^9/4/G ^7/4, where the symbols have their common meaning. The second has to do with the upper limit to the mass loss and is replaced by the postulate of equipartition of thermal power and mechanical power in the photosphere. This equipartition seems to be reached in stars of spectral type earlier than G8. Only for these stars the above mass loss formula is valid.     

UBV photometry of DX Aquarii

U, B, V photometry of the eclipsing binary DX Aqr has been presented for the first time. The period of the system comes out to be nearly half the period given by Strohmeier (1966) and a value of O^d.472502 has been determined. The colour of the system has been discussed. The primary eclipse is a total occulation. The orbit seems to be eccentric. The system belongs to Algol type. DX Aqr may be a very complicated system. The present results are considerably different from those of earlier investigations.     

Helium emission in the middle chromosphere

Slitless spectrograms obtained during the eclipse of 10 June 1972 have been analyzed to determine the height distribution of the D₃ He line intensity.For undisturbed regions the maximum of D₃ line intensity is confirmed to exist at about 1700km above the limb. Besides the above mentioned maximum, in plages a considerable intensity may be observed at low heights (h < 1000 km).An analysis of these observations for h > 1000 km has been carried out within the low temperature mechanism of triplet helium emission taking into account the helium ionization by XUV radiation. The density dependence of the 2³ S level population at different XUV flux values has been calculated. Our observations give N _e 2 × 10¹⁰ cm^–3 in the chromosphere at h = 2000 km. The probable coincidence of the H and He emission small filaments in the middle chromosphere is discussed.     

Characteristic actionsħ (s) in the structure of the universe and the problem of the origin of galaxies

From the characteristic actions ^(s), we can derive various relations between the basic characteristic quantities of objects and the fundamental constants in known physical laws. The main physical processes which lead to the formation of objects should be included in some such reletions through the fundamental constants. The problem of the origin of galaxies has been considered on the basis of the theory of actions ^(s). It has been shown that in addition to gravitational effect, the dissipation process of the adiabatic density perturbations arising from the Thomson scattering in the early universe is a crucial process in forming galaxies; and if the Hubble constant has a valueH ₀ 50 km s^–1 Mpc^–1, the protogalaxies might be formed just before recombination.