An analysis of an extensive collection of photometric and spectroscopic observations of the little studied bright Be star V360 Lac lead to the following main conclusions: (1) V360 Lac is a binary system consisting of a B3e primary and a F9IV secondary which probably fills the Roche lobe and losses mass towards the primary. Radial-velocity curves of both components were obtained. (2) The light variations arise from superposition of variations on at least three time scales: phase-locked orbital brightness and colour changes with two minima; sinusoidal variation with a 322.24^d^ period and low-amplitude rapid changes with a possible period of 1.6738^d^. (3) A tentative solution of the B and V light curves which assumes the semi-detached configuration and presence of a disk around the primary, combined with the orbital solution, leads to preliminary basic physical elements of the system which are consistent with the radiative properties of the binary components.
A complete period variation analysis and new light curves of V839 Oph together with new ephemeris data are presented. The period variation was found to be dP/dt=3.1x10^-7d/yr. The period increament indicates that the conservative mass transfer rate from the less massive component to the more massive one is 6.5x10^-7M_sun_/yr. We fitted parabolic and we discuss the possible detection of sinusoidal curves to the (O-C) diagram and sinusoidal oscillations with period of about 20yr and semi-amplitude of 0.0065 day. A simultaneous solution of the B and V light curves was computed using the Wilson-Devinney synthetic light-curve code. The light curve solution indicates that the A-type W UMa-type system is in contact with a filling factor of ~39%.
UBV photometry of 186 stars with 17h < R.A. < 19h listed in Stephenson and Sanduleak's "Luminous Stars in the Southern Milky Way" catalog (Stephenson C.B. & Sanduleak N. 1971, Publ. Warner and Swasey Obs. 1, No. 1) is reported.
Using the Hubble Space Telescope (HST) and the Large Binocular Telescope, we followed the evolution of the Type Ia supernova (SN Ia) 2011fe for an unprecedented 1840 days past B-band maximum light and over a factor of 7 million in flux. At 1840 days, the 4000-17000{AA} quasi-bolometric luminosity is just (420+/-20)L_{sun}_. By measuring the late-time quasi-bolometric light curve, we present the first confident detection of ^57^Co decay in a SN Ia light curve and estimate a mass ratio of log(^57^Co/^56^Co)=-1.59_-0.07_^+0.06^. We do not have a clean detection of ^55^Fe, but find a limit of ^55^Fe/^57^Co<0.22 with 99% confidence. These abundance ratios provide unique constraints on the progenitor system because the central density of the exploding white dwarf(s) dictates these nucleosynthetic yields. The observed ratios strongly prefer the lower central densities of double-degenerate models (^55^Fe/^57^Co=0.27) over the higher central densities of near-Chandrasekhar-mass single-degenerate models (^55^Fe/^57^Co=0.68). However, additional theoretical studies predicting isotopic yields from a broader range of progenitor systems are motivated by these unique observations. We will continue to observe SN 2011fe for another ~600 days with HST and possibly beyond.
Photoelectric (UBVR) observations in 1998-2001 and medium-resolution spectroscopy obtained in the SAO in the same period for the B[e]/X-ray transient CI Cam display cyclic variations with a period of 1100 days.
We present results from a continuing campaign to secure deep multi-colour CCD sequences for photoelectric calibration in UK Schmidt fields with galactic latitudes |b|>50{deg}. In this paper, we present UBVR photometry in 12 fields and BR photometry in a further 14 fields observed within UK Schmidt survey fields centered at {delta}=-30{deg}. Our observations were carried out with the 0.9m Telecope at the Cerro-Tololo Inter-American Observatory.
We present photometry and a preliminary interpretation of a UBVR survey of the Large and Small Magellanic Clouds, which covers 14.5 deg^2^ and 7.2deg^2^, respectively. This study is aimed at obtaining well-calibrated data on the brighter, massive stars, complementing recent, deeper CCD surveys. Our catalog contains 179,655 LMC and 84,995 SMC stars brighter than V~18.0, and is photometrically complete to U~B~V~15.7 and R~15.2, although stars in crowded regions are selectively missed. We compare our photometry to that of others, and describe the need for gravity-dependent corrections to our CCD U-band photometry. We provide a preliminary cross-reference between our catalog stars and the stars with existing spectroscopy.
We present precision CCD light curves, a period study, photometrically derived standard magnitudes, and a five-color simultaneous Wilson code solution of the totally eclipsing, yet shallow amplitude (Av~0.4mag) eclipsing, binary V1853 Orionis. It is determined to be an extreme mass ratio, q=0.20, W-type W UMa overcontact binary. From our standard star observations, we find that the variable is a late-type F spectral-type dwarf, with a secondary component of about 0.24 solar masses (stellar type M5V). Its long eclipse duration (41 minutes) as compared to its period, 0.383-days, attests to the small relative size of the secondary. Furthermore, it has reached a Roche lobe fill-out of ~50% of its outer critical lobe as it approaches its final stages of binary star evolution, that of a fast spinning single star. Finally, a summary of about 25 extreme mass ratio solar-type binaries is given.
We present homogeneous, standardized UBV(RI)C photometry for over 700 nearby stars selected on the basis of Hipparcos parallaxes. Additionally, we list JHK photometry for about half of these stars, as well as L photometry for 86 of the brightest. A number of stars with peculiar colours or anomalous locations in various colour-magnitude diagrams are discussed.
We present UBVRcIc magnitudes of 49 comparison stars in the fields of the Seyfert galaxies Mrk 335, Mrk 79, Mrk 279, Mrk 506, 3C 382, 3C 390.3, NGC 6814, Mrk 304, Ark 564, and NGC 7469 in order to facilitate the photometric monitoring of these objects; 36 of the stars have not been calibrated before. The comparison stars are situated in 5x5arcmin fields centred on the Seyfert galaxies, their V band flux ranges from 11.7 to 18.2mag with a median value of 16.3mag, and their B-V colour index ranges from 0.4 to 1.6mag with a median value of 0.8mag. The median errors of the calibrated UBVRCIC magnitudes are 0.08, 0.04, 0.03, 0.04, and 0.06mag, respectively. Comparison stars were calibrated for the first time in three of the fields (Mrk 506, 3C 382, and Mrk 304). The comparison sequences in the other fields were improved in various aspects. Extra stars were calibrated in four fields (Mrk 335, Mrk 79, NGC 6814, and NGC 7469) most of these stars are fainter and are situated closer to the Seyfert galaxies compared to the existing comparison stars. The passband coverage of the sequences in five fields (Mrk 335, Mrk 79, Mrk 279, NGC 6814, and Ark 564) was complemented with the U band.
