UY Camelopardalis Possibly Has an Unseen Companion

arXiv (Cornell University), 2013

Nine new short period variable stars have been discovered in the direction of the open cluster Cr464 in Camelopardalis. The field was observed using Tzec Maun Observatory's telescope AP-180. Two new variable stars were classified as pulsating stars (RRab and RRc types). The other seven stars are binary systems. One of them is of ELL-type, four binaries were recognized as EW-type, and two systems are rather short period EA-type binaries. All new variables were registered in the VSX catalogue.

Apogee ALTA U47+ CCD camera. 1024 x 1024 pixels. Method of data reduction: Reduction of the CCD frames and differential photometry were performed with the standard tasks of IRAF 1 package Method of minimum determination: The minima times of eclipsing binaries were calculated using Kwee & van Woerden's (1956) method. Mid-transit times were calculated by making use of a model-fitting algorithm available via the Exoplanet Transit Database (Poddaný et al. 2010) 2. † Based on the observations performed at Ankara University Kreiken Observatory 1 IRAF is distributed by the National Optical Astronomical Observatories, operated by the Association of the Universities for Research in Astronomy, inc., under cooperative agreement with the National Science Foundation 2 http://var2.astro.cz/ETD/

Astronomische Nachrichten, 2016

New standardized V-band light curves (LCs) for the eclipsing binary SV Cam have been modeled using the PHOEBE program (v. 0.31a). Absolute parameters of the stellar components were then determined, enabling them to be positioned on the mass-radius diagram. Analysis of eclipse minima timing data (O − C diagrams) indicated two cyclic periods of 48.0 and 23.3 yr. These cyclic variations of the orbital period are interpreted in terms of motion of a third body around the system and magnetic activity cycle modulating the orbital period of SV Cam via the Applegate (1992) mechanism. The use of the Applegate model for SV Cam has been checked by examining the long term brightness variation and calculating some important parameters of this system. The results of these calculations favor the modulation of the orbital period by the Applegate mechanism.

Astronomy and Astrophysics, 2006

Context. BL Cam is an extreme field multiperiodic short-period low-metallicity high-amplitude SX Phe-type variable where its probably complex pulsational content is subject of controversies. Aims. A comprehensive study has been carried out to investigate the nature and pulsational properties of this object. Methods. The analysis is based on new photometric data collected during the last few years at different sites, as well as on all available previously published data. Frequency analyses have been performed on a number of reliable data sets to analyse the pulsational content. In addition, the classical O−C method was used to study the behaviour of the main period. Results. Our frequency analysis confirms some aspects on the multiperiodicity of BL Cam, previously found by other authors, showing a number of secondary modes close to the main frequency f 0 = 25.5769 cd −1 . The secondary modes present eventual amplitude variations. However, the main frequency exhibits no significant changes in its amplitude and seems to correspond to the fundamental mode of radial pulsation. Abrupt changes sometimes observed in the light curves could be due to spurious activity on or close to the star's photosphere. We confirm the existence of a secondary frequency at 31.6 or 32.6 cd −1 , with variable amplitude, and with the possibility of both frequencies being intrinsic to the star. More than one hundred of new times of light maxima have been determined in the present work. These together with those available in the literature allow us a more discriminating analysis of the O-C diagram. This shows that the observed variations of the main period can be described by two terms: (i) a secular increase of the main period at a rate of dP/Pdt = 117(±3) × 10 −9 yr −1 ; and (ii) a perturbation from a companion star in a rather eccentric orbit with a period of 10.5(±0.2) yr causing a light time semi-amplitude of 148(±12) s.

arXiv (Cornell University), 2022

We report photometric observations of the hidden symbiotic star SU Lyn in the optical bands. In five nights we detect a weak flickering in U band with amplitude of about 0.05 magnitudes. No intranight variations are found in B, V, g' and r' bands. This is one more indication that the secondary component is a white dwarf accreting at a low accretion rate. We also searched for intranight variability of a dozen related objects-RR Boo, RT Boo, AM Cyg, AG Peg, BF Cyg, NQ Gem, StHa190, V627 Cas, XX Oph, FS Cet and Y Gemhowever no variability above the observational errors is detected.

2010

In November 2009, another national conference on variable stars, stellar astrophysics in general and on extrasolar planets was organised by Variable Star and Exoplanet section of Czech Astronomical Society. The conference was held in beautiful and one of the oldest observatory in Czech republic - Stefanik Observatory in Prague. Our conferences on variable star research provide unique opportunities for meetings between professional and amateur astronomers and have become a crucial platform for exchanging information and sharing knowledge. These events help to keep the local astronomical community alive and active. This years conference was held on a weekend from November 27 to November 29. All almost 40 participants were able to witness the richness of our field and the joy that research on variable stars brings to our lifes.

We present more than 80 new variable stars discovered during the first observing season of the APACHE survey. APACHE is a project aimed at detecting extrasolar planets transiting nearby, bright M dwarfs by using an array of small-aperture telescopes. Despite the fact that the survey is targeted to a well-defined sample of cool stars, we also reduce and analyze data for all the detected field stars. Since July 2012 dozens of different stellar fields have been monitored, leading to the detection of several variables for which we propose a classification and estimate a period, when a periodicity is evident in the data. Thanks to the SuperWASP public archive, we have also retrieved and analyzed photometric data collected by the SWASP survey, which helped us to refine the classification and the period estimation of many variables found in the APACHE database. Some of the variables present peculiarities and thus are discussed separately.

2010

We present the discovery of nonradial pulsations in a hot subdwarf B star based on 30.5 days of nearly continuous time-series photometry using the Kepler spacecraft. KIC 010139564 is found to be a short-period pulsator of the V361 Hya (EC 14026) class with more than 10 independent pulsation modes whose periods range from 130 to 190 seconds. It also shows one periodicity at a period of 3165 seconds. If this periodicity is a high order g-mode, then this star may be the hottest member of the hybrid DW Lyn stars. In addition to the resolved pulsation frequencies, additional periodic variations in the light curve suggest that a significant number of additional pulsation frequencies may be present. The long duration of the run, the extremely high duty cycle, and the well-behaved noise properties allow us to explore the stability of the periodic variations, and to place strong constraints on how many of them are independent stellar oscillation modes. We find that most of the identified periodicities are indeed stable in phase and amplitude, suggesting a rotation period of 2-3 weeks for this star, but further observations are needed to confirm this suspicion.

Monthly Notices of the Royal Astronomical Society, 2001

Time-series photometry of the Hipparcos variable stars HD 199434 and 21190 is reported. Both stars are pulsators of the d Scuti type. Reclassifications of the MK types of the stars, based on new spectrograms, are given. HD 21190 is found to be F2III SrEuSi:, making it the most evolved Ap star known. Its Strömgren photometric indices support the peculiar spectral type. It is also one of the most evolved d Scuti stars known. Its combined Ap -d Scuti nature makes it an important test of models of pulsation in peculiar stars recently developed by Turcotte et al., although it is more extreme than any model they examined. Physical parameters of both stars are estimated from Strömgren and Hb photometry, and Hipparcos absolute magnitudes. We attempt mode identifications based on amplitude ratios and phase differences from our photometry. The dominant pulsation of HD 21190 may be an overtone radial mode. The model fits for HD 199434 are even less satisfactory, but favour an ' ¼ 2 mode. Given the good quality and wavelength coverage of our data, the poor results from the application of the photometric theory of mode identification may call into question the use of that technique.

The Astronomical Journal, 2003

Utilizing Hipparcos parallaxes, original radial velocities and recent literature values, new Ca ii H and K emission measurements, literature-based abundance estimates, and updated photometry (including recent resolved measurements of close doubles), we revisit the Ursa Major moving group membership status of some 220 stars to produce a final clean list of nearly 60 assured members, based on kinematic and photometric criteria. Scatter in the velocity dispersions and H-R diagram is correlated with trial activity-based membership assignments, indicating the usefulness of criteria based on photometric and chromospheric emission to examine membership. Closer inspection, however, shows that activity is considerably more robust at excluding membership, failing to do so only for 15% of objects, perhaps considerably less. Our UMa members demonstrate nonzero vertex deviation in the Bottlinger diagram, behavior seen in older and recent studies of nearby young disk stars and perhaps related to Galactic spiral structure. Comparison of isochrones and our final UMa group members indicates an age of 500 AE 100 Myr, some 200 Myr older than the canonically quoted UMa age. Our UMa kinematic=photometric members' mean chromospheric emission levels, rotational velocities, and scatter therein are indistinguishable from values in the Hyades and smaller than those evinced by members of the younger Pleiades and M34 clusters, suggesting these characteristics decline rapidly with age over 200-500 Myr. None of our UMa members demonstrate inordinately low absolute values of chromospheric emission, but several may show residual fluxes a factor of !2 below a Hyades-defined lower envelope. If one defines a Maunder-like minimum in a relative sense, then the UMa results may suggest that solar-type stars spend 10% of their entire main-sequence lives in periods of precipitously low activity, which is consistent with estimates from older field stars. As related asides, we note six evolved stars (among our UMa nonmembers) with distinctive kinematics that lie along a 2 Gyr isochrone and appear to be late-type counterparts to disk F stars defining intermediate-age star streams in previous studies, identify a small number of potentially very young but isolated field stars, note that active stars (whether UMa members or not) in our sample lie very close to the solar composition zero-age main sequence, unlike Hipparcos-based positions in the H-R diagram of Pleiades dwarfs, and argue that some extant transformations of activity indices are not adequate for cool dwarfs, for which Ca ii infrared triplet emission seems to be a better proxy than H-based values for Ca ii H and K indices.