Edward Schoenfeld: Visual photometry of variable stars. 2. Variable stars

We describe the results of visual photometry of 111 variable stars observed by Schoenfeld in the 19th century. The entire body of data contains brightness curves in tabulated form, as well as certain additional useful information: graphs of changes in brightness of variable stars and identification tables of comparison stars and stars suspected of variation in brightness.     

Infrared photometry for two RV Tau stars and V1027 Cyg

We present and discuss the results of our long-term JHKLM photometry for two RV Tau stars (R Sge and RV Tau) and the yellow supergiant V1027 Cyg, a candidate for protoplanetary nebulae. The amplitude of the infrared brightness variations in R Sge and RV Tau over fourteen years of observations was 0 _. ^m 9?1 ^m ; the infrared brightness variations in V1027 Cyg over eighteen years did not exceed 0 _. ^m 25. The infrared brightness and color of R Sge fluctuated about their gradually changing mean values; the infrared brightness variations agree with a period of 70.77 days. The periodic J brightness and J-H color variations in R Sge can be explained by temperature pulsations with ΔT ≤ 200 K and radial pulsations with [ΔR/R] ≤ 0.2. From 1995 to 2008, the mean J brightness of RV Tau increased, while its mean J-H color index decreased; the variations in the mean J brightness can be associated mainly with stellar temperature variations; a periodic component with P = 78.73 days is observed in the infrared brightness and color fluctuations. The variations in the mean J brightness and J-H color index of the supergiant V1027 Cyg over eighteen years of observations did not exceed a few hundredths of a magnitude; both temperature and radial pulsations may be present in the observed J brightness variations. The most probable period of the infrared brightness fluctuations in V1027 Cyg is 237 ± 2 days. The dust shell of R Sge may consist of two layers with grain temperatures of ～1000 and ～700 K; the optical depth at 1.25 µm is ～0.02 and ～0.24, respectively. The grain temperatures in the circumstellar dust shells of the supergiants RV Tau and V1027 Cyg are ～600 K (RV Tau) and ～700 K (V1027 Cyg). Their optical depths at 1.25 µm are ～0.24 (RV Tau) and ～0.008 (V1027 Cyg).     

BVR photometry of the three RS CVn binary stars: V711 Tau,UX Ari and IM Peg

Differential BVR photometric observations of the three RS CVn binary stars: V711 Tau, UX Ari and IM Peg obtained during the period November 26, 1994–February 24, 1995 using the 0.35 m reflector telescope equipped with photoelectric photometer are presented. Analysis of light curves shows significant changes in shape, amplitude as well as the phases of minimum light of all the three binaries. The amplitude of IM Peg, in particular, is found to have reached a larger value in the present epoch of observation than reported earlier.     

UBV photometry of bright stars in the spiral arm S5 of M31

A photometric study inUBV of about 1000 bright stars outside and inside associations in S5 spiral arm is presented briefly. Characteristics of the associations (such as absorption, age and brightest stars are compared with the same characteristics of the associations in S4 spiral arm of M31, as well as in M33) are discussed.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.     

Long-term V(RI)_c CCD photometry of pre-main-sequence stars in the association Cepheus OB3

Results from optical CCD photometric observations of 13 pre-main-sequence stars collected during the period from February 2007 to November 2020 are presented. These stars are located in the association Cepheus OB3, in the field of the young star V733 Cephei. Photometric observations, especially concerning the long-term variability of the stars, are missing in the literature. We present the first longterm V(RI)_c monitoring for them, that cover 13 years. Results from our study indicate that all of the investigated stars manifest strong photometric variability. The presented paper is a part of our program for the photometric study of pre-main-sequence stars located in active star-forming regions.     

CCD photometry of variable stars in the Magellanic Clouds — V. The eclipsing binaries HV 1620 and HV 2241

Using improved techniques, high-quality CCD uvbyVI _C photometry has been obtained for the 14th magnitude eclipsing binaries HV 1620 in the Small Magellanic Cloud (SMC) and HV 2241 in the Large Magellanic Cloud (LMC). IUE ultraviolet spectrophotometry was also obtained. These data have been analysed using the Wilson & Devinney synthetic light-curve code and Kurucz model atmospheres. Both systems are semi-detached and appear to have undergone mass exchange. In HV 1620 the mass ratio and the effective temperatures of the primary and secondary are q  =  M ₂/ M ₁ = 0.68 ± 0.03, T _eff,1 = 33 000 ± 4500 K and T _eff,2 = 24 000 ± 3500 K. The corresponding values for HV 2241 are 0.53 ± 0.01, 27 000 ± 3000 K and 20 200 ± 1500 K. Using the radial-velocity curves obtained by Niemela & Bassino with a 1-m telescope, we find that both systems are massive, as expected. Reddening considerations suggest both systems may lie towards the rear of their respective Clouds.     

A comment on ‘Far ultraviolet photometry of orion stars’ by G.R. Carruthers

It is shown that the ultraviolet flux-deficiency, recently discovered by Carruthers, in early-type supergiants compared to dwarfs of the same spectral type can be explained in terms of the effects of differences in surface-gravity and effective temperature between stars of these two luminosity classes. It thus appears that this deficiency does not represent a serious discrepancy between theory and observation.     

Multiperiodicities from the Hipparcos epoch photometry and possible pulsation in early A-type stars

A selection criterion based on the relative strength of the largest peaks in the amplitude spectra, and an information criterion are used in combination to search for multiperiodicities in Hipparcos epoch photometry. The method is applied to all stars which have been classified as variable in the Hipparcos catalogue: periodic, unsolved and microvariables. Results are assessed critically: although there are many problems arising from aliasing, there are also a number of interesting frequency combinations which deserve further investigation. One such result is the possible occurrence of multiple periods of the order of a day in a few early A-type stars. The Hipparcos catalogue also contains a number of these stars with single periodicities: such stars with no obvious variability classifications are listed, and information about their properties (e.g., radial velocity variations) discussed. These stars may constitute a new class of pulsators.     

Total ozone measurements derived from T.O.V.S. radiances

A new method of total ozone retrieval from i.r. satellite data(NOAA6) is presented. It uses ozone transmittance as a predictor of total ozone. Ozone transmittance at 9.6 μm(TR) is deduced from radiance at 9.6 μm(R9), surface temperature (TS) measured at 11 μm, and ozone mean temperature (TE) estimated from several channels (among them 9.6 μm) by the radiative transfer equation : R9 = B(TS) × TR + (1?TR) × B(TE) where B is the Planck function.A statistical analysis of the retrieved ozone field and a comparison with ground based measurements show that the S.E. is less than 5% for the considered data set.     

B,V photometry of the active RS CVn system II Peg

In this work,B andV photometry of the RS CVn-type binary II Peg is presented. The light curves obtained in 1983 and 1984 display two unequal maxima. The light curves of the system have different amplitudes. The amplitude seems to vary with three different periods. 10, 6, and 4 years of periods may be attributed to those variations.     

B,V surface photometry of the UV continuum galaxy NGC 838

Surface photometry of the UV continuum galaxy NGC 838 has been carried out in theB, V system using photographic plates obtained with the 74 Kottamia telescope, Egypt. Isophotes, luminosity profiles, integrated photographic magnitudes, effective diameters and other photometric parameters are derived.The photoelectrically calibrated total apparent magnitudes areB _T =13.57 with maximum diameters 1.57×1.34 (at threshold _m =27.7 mag.//) andV _T =12.91 with maximum diameters 1.54×1.32 (at threshold _m =27.7 mag./). The integrated colour index(B–V) _T =0.66 and the effective surface brightness _e (B=19.0 mag./) and _e (V=19.7 mag./. The major axis is at position angle =85°±1°.The nucleus of NGC 838 is quite blue (integrated colour(B–V)=0.41 forr ^*<0.1) compared to normal galaxies while the colour becomes redder from the nucleus outwards. The UV excess, H emission and radio continuum emission previously observed from this galaxy by other investigators may be attributed to a recent burst of star formation in the nucleus of the galaxy of duration slightly greater than 2×10⁷ yr.     

UBV photometry, UV spectroscopy and radio observations of the peculiar binary V Sagittae

We have performed high-speed UBV photometric observations on the peculiar binary V Sagittae. Using three new eclipse timings we update the orbital ephemeris and convert it to a dynamical time-scale (TDB). We also searched for quasi-periodic oscillations but did not detect them. Using the Wilson–Devinney algorithm we have modelled the light curve to find the stellar parameters of V Sge. We find that the system is a detached binary but that the primary star is very close to filling its Roche lobe, while the secondary star fills 90 per cent of its Roche lobe volume. We find temperatures of the primary and the secondary star to be T ₁=41 000 K and T ₂=22 000 K. We find i =72° and masses of 0.8 M_⊙ and 3.3 M_⊙ for the primary and secondary stars respectively. De-archived Hubble Space Telescope ( HST ) spectroscopy of V Sge shows evidence of mass loss via a wind or winds. In addition we report radio observations of V Sge during an optical high state at 2 cm, 3.6 cm and 6 cm wavelengths. The 3.6 cm emission is increased by a factor of more than six compared with an earlier detection in a previous optical high state.     

Photoelectric photometry of the stars HD 29647 and HDE 283809 in the Taurus dark cloud

Photoelectric Vilnius photometry of the B-type stars HD 29 647 and HDE 283 809 in the direction of the Taurus molecular cloud indicates their brightness and energy distribution to be constant within 1–2%. The interstellar extinction law is determined for the star HDE 283 809 from the photometry data in the Vilnius andUBVRJHKL systems, which yield the ratioR=A _V/E_B-V=3.5 and grain sizes exceeding the average by approximately 10%. The interstellar extinction law for the two stars is found to be the same in the infrared, however, it is very different in the near ultraviolet. The new spectra of HDE 283 809 confirm the earlier classification and indicate an absence of emission in the hydrogen lines. The interstellar band at 443 nm is observed but its intensity is a half of what is expected forE _B-V=1.61. The observed peculiarities of the energy distribution in the spectrum of HDE 283 809 apparently originate in interstellar or circumstellar dust, not in the star itself.Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation.     

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.     

A search for S stars in the IRC and AFGL Catalogues

There is a clear relation between the amplitude of the visual light curve, the period and the luminosity of the low amplitude Scuti stars.