The list of the stars from the Two-micron sky survey: A preliminary catalog by G. N. Neugebauer et al (IRC), the identification of which is not correct

Two tables are published. The first presents the numbers of stars according to the Catalog IRC for which all or part of the identification with the Catalogs BS-HR, GC or DM is incorrect. The second table presents the numbers of stars in the IRC catalog, for which the identifications with variable stars printed with them are erroneous, whereas other identifications are usually correct

The new identifications of the variable stars with the stars from the ""Two-Micron Sky Survey: A Preliminary Catalog'' by G. Neugebauer etal. (IRC)

A list of 151 variable stars is presented. The identification of 148 of them is beyond any doubt. The identification of 3 stars is quite probable, but requires further checking

Some Systematics of Galactic Globular Clusters

The global properties of all known Galactic globular clusters are examined. The relationship between the luminosities and the metallicities of Galactic globular clusters is found to be complex. Among luminous clusters there is a correlation in the sense that the oldest clusters are slightly more metal deficient than are younger clusters. However, no such clear-cut relationship is found among the faintest globular clusters. The central concentration index C of globular clusters is seen to be independent of metallicity. The dependence of the half-light radii of globular clusters on their Galactocentric distances can be approximated by the relation $R_h \alpha R^{2/3}_{gc}$. Clusters with collapsed cores are mostly situated close to the Galactic nucleus. For $R_{gc} < 10$ kpc the luminosities and the radii of clusters appear to be uncorrelated. The Galaxy differs from the LMC and the SMC in that it appears to lack highly flattened luminous clusters. Galactic globular clusters with ages $\geq$ 13.0 Gyr are all of Oosterhoff type II, whereas almost all of those with ages $<$ 13.0 Gyr have been assigned to Oosterhoff type I. Globular clusters with ages $<$11.5 Gyr are all located in the outer Galactic halo, have below-average luminosities and above-average radii. On the other hand the very old globular cluster NGC 6522 is situated close to the Galactic nucleus.Comment: PASP, in pres

First photometric study of the eclipsing binary PS Persei

The CCD photometric observations of the eclipsing binary PS Persei (PS Per) were obtained on two consecutive days in 2009. The 2003 version Wilson-Devinney code was used to analyze the first complete light curves in $V$ and $R$ bands. It is found that PS Per is a short-period Algol-type binary with the less massive component accurately filling its inner critical Roche lobe. The mass ratio of $q=0.518$ and the orbital inclination of $i=89.^{\circ}86$ are obtained. On the other hand, based on all available times of primary light minimum including two new ones, the orbital period has been improved.Comment: 7 pages, 4 figure

Multicolour CCD photometry of the variable stars in globular cluster M3

We present time series data on the variable stars of the galactic globular cluster Messier 3 (M3). We give BVI light curves for 226 RR Lyrae, 2 SX Phe and 1 W Vir type variables, along with estimated fundamental photometric parameters such as intensity and magnitude-averaged brightness and pulsation periods. In some cases the periods we have found significantly differ from the previously published ones. This is the first published light curve and period determination for variable V266. The I-band light curve has not been observed previously for numerous (76) variables. Three new RR Lyrae variables have been discovered. Groups of RR Lyrae variables that belong to different evolutionary stages and have been separated previously on the basis of V data were found here for all colours and colour indices by cluster analysis. The I-band period -- luminosity relation is also discussed. From the 66 modulated (Blazhko type) RR Lyrae stars we investigated, six are newly identified and two of them are first overtone pulsators. In the case of 13 RR Lyrae, the period of Blazhko cycle has been estimated for the first time. V252 is identified as a new RRd variable. Amplitude ratio of RRd stars have been investigated to search possible mode content changes. In contrast to previous publications no changes have been found. Problems with the sampling of the time series of typical cluster variability surveys is demonstrated.Comment: 24 pages, 15 figures, 8 tables. Accepted by MNRAS on 18. August 200

The viscosity parameter alpha and the properties of accretion disc outbursts in close binaries

The physical mechanisms driving angular momentum transport in accretion discs are still unknown. Although it is generally accepted that, in hot discs, the turbulence triggered by the magneto-rotational instability is at the origin of the accretion process in Keplerian discs, it has been found that the values of the stress-to-pressure ratio (the alpha "viscosity" parameter) deduced from observations of outbursting discs are an order of magnitude higher than those obtained in numerical simulations. We test the conclusion about the observation-deduced value of alpha using a new set of data and comparing the results with model outbursts. We analyse a set of observations of dwarf-nova and AM CVn star outbursts and from the measured decay times determine the hot-disc viscosity parameter alpha_h. We determine if and how this method is model dependent. From the dwarf-nova disc instability model we determine an amplitude vs recurrence-time relation and compare it to the empirical Kukarkin-Parenago relation between the same, but observed, quantities. We found that all methods we tried, including the one based on the amplitude vs recurrence-time relation, imply alpha_h ~ 0.1 - 0.2 and exclude values an order of magnitude lower. The serious discrepancy between the observed and the MRI-calculated values of the accretion disc viscosity parameter alpha is therefore real since there can be no doubt about the validity of the values deduced from observations of disc outbursts.Comment: Astronomy and Astrophysics, in press. (In Fig. 3b the upper sequence of numbers and symbols is an artefact of the compilation on astro-ph) and should be ignored.

Genetic-Algorithm-based Light Curve Optimization Applied to Observations of the W UMa star BH Cas

I have developed a procedure utilizing a Genetic-Algorithm-based optimization scheme to fit the observed light curves of an eclipsing binary star with a model produced by the Wilson-Devinney code. The principal advantages of this approach are the global search capability and the objectivity of the final result. Although this method can be more efficient than some other comparably global search techniques, the computational requirements of the code are still considerable. I have applied this fitting procedure to my observations of the W UMa type eclipsing binary BH Cassiopeiae. An analysis of V-band CCD data obtained in 1994/95 from Steward Observatory and U- and B-band photoelectric data obtained in 1996 from McDonald Observatory provided three complete light curves to constrain the fit. In addition, radial velocity curves obtained in 1997 from McDonald Observatory provided a direct measurement of the system mass ratio to restrict the search. The results of the GA-based fit are in excellent agreement with the final orbital solution obtained with the standard differential corrections procedure in the Wilson-Devinney code.Comment: 9 pages, 2 figures, 2 tables, uses emulateapj.st

The Behavior of Novae Light Curves Before Eruption

In 1975, E. R. Robinson conducted the hallmark study of the behavior of classical nova light curves before eruption, and this work has now become part of the standard knowledge of novae. He made three points; that 5 out of 11 novae showed pre-eruption rises in the years before eruption, that one nova (V446 Her) showed drastic changes in the variability across eruptions, and that all but one of the novae (excepting BT Mon) have the same quiescent magnitudes before and after the outburst. This work has not been tested since it came out. We have now tested these results by going back to the original archival photographic plates and measuring large numbers of pre-eruption magnitudes for many novae using comparison stars on a modern magnitude scale. We find in particular that four out of five claimed pre-eruption rises are due to simple mistakes in the old literature, that V446 Her has the same amplitude of variations across its 1960 eruption, and that BT Mon has essentially unchanged brightness across its 1939 eruption. Out of 22 nova eruptions, we find two confirmed cases of significant pre-eruption rises (for V533 Her and V1500 Cyg), while T CrB has a deep pre-eruption dip. These events are a challenge to theorists. We find no significant cases of changes in variability across 27 nova eruptions beyond what is expected due to the usual fluctuations seen in novae away from eruptions. For 30 classical novae plus 19 eruptions from 6 recurrent novae, we find that the average change in magnitude from before the eruption to long after the eruption is 0.0 mag. However, we do find five novae (V723 Cas, V1500 Cyg, V1974 Cyg, V4633 Sgr, and RW UMi) that have significantly large changes, in that the post-eruption quiescent brightness level is over ten times brighter than the pre-eruption level.Comment: 91 pages (preprint), AJ accepte

Highly Variable Objects in the Palomar-QUEST Survey: A Blazar Search using Optical Variability

We identify 3,113 highly variable objects in 7,200 square degrees of the Palomar-QUEST Survey, which each varied by more than 0.4 magnitudes simultaneously in two broadband optical filters on timescales from hours to roughly 3.5 years. The primary goal of the selection is to find blazars by their well-known violent optical variability. Because most known blazars have been found in radio and/or X-ray wavelengths, a sample discovered through optical variability may have very different selection effects, elucidating the range of behavior possible in these systems. A set of blazars selected in this unusual manner will improve our understanding of the physics behind this extremely variable and diverse class of AGN. The object positions, variability statistics, and color information are available using the Palomar-QUEST CasJobs server. The time domain is just beginning to be explored over large sky areas; we do not know exactly what a violently variable sample will hold. About 20% of the sample has been classified in the literature; over 70% of those objects are known or likely AGN. The remainder largely consists of a variety of variable stars, including a number of RR Lyrae and cataclysmic variables.Comment: 22 pages (preprint format), 2 figures. Accepted for publication in ApJ. References update