Using the 2m telescope of the Bulgarian National Astronomical Observatory at Rozhen, observations of 246 double or multiple stars were carried out during six nights in 2012. This is the seventh series of measurements of CCD frames of double and multiple stars obtained at Rozhen. Also in 2012, using the 0.6m telescope of the Serbian Astronomical Station on the mountain of Vidojevica, observations of 117 double or multiple stars were carried out during five nights. This is the second series of measurements of CCD frames of double and multiple stars obtained at this station. In this paper we present the results for the position angle and angular separation for 453 pairs and residuals for 105 pairs with published orbital elements or linear solutions. These observations have angular separations in the range from 1.50'' to 178.12'', with a median angular separation of 8.13''. We also present the recalculated linear solution for one pair and three linear solutions that have been calculated for the first time.
Results of CCD observations of 154 double or multiple stars, made with the 2 m telescope of the Bulgarian National Astronomical Observatory at Rozhen over five nights in 2015, are presented. This is the ninth series of measurements of CCD frames obtained at Rozhen. We also present results of CCD observations of 323 double or multiple stars made with the 0.6 m telescope of the Serbian Astronomical Station on the mountain of Vidojevica over 23 nights in 2015. This is the fourth series of measurements of CCD frames obtained at this station. This paper contains the results for the position angle and angular separation for 801 pairs and residuals for 127 pairs with published orbital elements or linear solutions. The angular separations are in the range from 1.52" to 201.56", with a median angular separation of 8.26". We also present eight pairs that are measured for the first time and linear elements for five pairs.
We present the results of an intensive multiwavelength campaign on nova LMC 2012. This nova evolved very rapidly in all observed wavelengths. The time to fall two magnitudes in the V band was only 2days. In X-rays the super soft phase began 13+/-5days after discovery and ended around day 50 after discovery. During the super soft phase, the Swift/XRT and Chandra spectra were consistent with the underlying white dwarf (WD) being very hot, ~1MK, and luminous, ~10^38^erg/s. The UV, optical, and near-IR photometry showed a periodic variation after the initial and rapid fading had ended. Timing analysis revealed a consistent 19.24+/-0.03hr period in all UV, optical, and near-IR bands with amplitudes of ~0.3mag which we associate with the orbital period of the central binary. No periods were detected in the corresponding X-ray data sets. A moderately high inclination system, i=60+/-10{deg}, was inferred from the early optical emission lines. The HST/STIS UV spectra were highly unusual with only the N v (1240{AA}) line present and superposed on a blue continuum. The lack of emission lines and the observed UV and optical continua from four epochs can be fit with a low mass ejection event, ~10^-6^M_{sun}_, from a hot and massive WD near the Chandrasekhar limit. The WD, in turn, significantly illuminated its subgiant companion which provided the bulk of the observed UV/optical continuum emission at the later dates. The inferred extreme WD characteristics and low mass ejection event favor nova LMC 2012 being a recurrent nova of the U Sco subclass.
Photometry of OGLE-2019-BLG-0304 with OGLE & KMTNet
Short Name:
J/AJ/162/203
Date:
01 Feb 2022 07:08:03
Publisher:
CDS
Description:
We analyze the microlensing event OGLE-2019-BLG-0304, whose light curve exhibits two distinctive features: a deviation in the peak region and a second bump appearing ~61days after the main peak. Although a binary-lens model can explain the overall features, it leaves subtle but noticeable residuals in the peak region. We find that the residuals can be explained by the presence of either a planetary companion located close to the primary of the binary lens (3L1S model) or an additional close companion to the source (2L2S model). Although the 3L1S model is favored over the 2L2S model, with {Delta}{chi}2~8, securely resolving the degeneracy between the two models is difficult with the currently available photometric data. According to the 3L1S interpretation, the lens is a planetary system, in which a planet with a mass 0.51_-0.23_^+0.51^M_J_ is in an S-type orbit around a binary composed of stars with masses 0.27_-0.12_^+0.27^M{odot} and 0.10_-0.04_^+0.10^M{odot}. According to the 2L2S interpretation, however, the source is composed of G- and K-type giant stars and the lens is composed of a low-mass M dwarf and a brown dwarf with masses 0.12_-0.05_^+0.12^M{odot} and 0.045_-.019_^+0.045^M{odot}, respectively. The event illustrates the need for thorough model testing in the interpretation of lensing events with complex features in light curves.
Photometry of orange-red CaI triplet in Late-Type Stars
Short Name:
II/25
Date:
21 Oct 2021
Publisher:
CDS
Description:
Calcium absorption lines were measured using narrow-band photometry on 296 high and low velocity G8-K5 stars of all luminosity classes. Because the blue-violet region of the stellar spectra is too crowded for narrow-band photometry, this investigation of abundance involved measurements of the orange-red CaI triplet 4(3)P-5(3)S, with wavelengths 6102.7, 6122.2 and 6162.2{AA}. "Calcium triplet ratio" is defined as "the measured light intensity ratios, comparison/central regions, calibrated in terms of a standard lamp as described in previous Cambridge papers". The catalog (table I of paper) includes HD number, (B-V) color index, Mg b ratio, H{alpha} ratio, Calcium triplet ratio, and a running number.
We report the discovery of 1RXS J173006.4+033813, a polar cataclysmic variable with a period of 120.21 minutes. The white dwarf primary has a magnetic field of B=42^+6^_-5_MG and the secondary is an M3 dwarf. The system shows highly symmetric double-peaked photometric modulation in the active state as well as in quiescence. These arise from a combination of cyclotron beaming and ellipsoidal modulation. The projected orbital velocity of the secondary is K_2_=390+/-4km/s. We place an upper limit of 830+/-65pc on the distance.
A subset of the RR Lyrae (RRL) candidates identified from the Southern Edgeworth-Kuiper Belt Object (SEKBO) survey data have been followed up photometrically (n=106) and spectroscopically (n=51). Period and light curve fitting reveals a 24+/-7% contamination of SEKBO survey data by non-RRLs. This paper focuses on the region of the Virgo Stellar Stream (VSS), particularly on its extension to the south of the declination limits of the Sloan Digital Sky Survey and of the Quasar Equatorial Survey Team (QUEST) RRL survey.
