We present the results of a photometric campaign of the dwarf nova V1040 Cen. The light curve shows two normal outbursts with recurrence time ~ 40 days and amplitude ~ 2.5 mag. Quiescence data show oscillations with periods in the range ~ 0.1 days (2
.4 h) to ~ 0.5 days (12 h) of unknown origin. We measured the orbital period of V1040 Cen to be P_orb=0.060458(80) days (1.451+-0.002 h). Based on the M_v-P_orb relation we found the distance of V1040 Cen to be 137+-31 pc. In this paper we also report the detection of eleven new variable stars in the field of the monitored dwarf nova.
We have used deep V-band and JHKs-band observations to investigate variability and stellar populations near the Galactic plane in Centaurus, and compared the observations with the Galactic model of Besancon. By applying image subtraction technique to
a series of over 580 V-band frames taken with the ESO VLT/VIMOS instrument during two contiguous nights in April 2005, we have detected 333 variables among 84,734 stars in the brightness range 12.7<V<26.0 mag. Infrared data collected in March 2010 with the new ESO VISTA telescope allowed us to construct deep combined optical-IR colour-magnitude and colour-colour diagrams. All detected variables but four transit candidates are reported for the first time. The majority of the variables are eclipsing/ellipsoidal binaries and delta Scuti-type pulsators. The occurrence rate of eclipsing/ellipsoidal variables reached ~0.28% of all stars. This is very close to the highest fraction of binary systems detected using ground-based data so far (0.30%), but still about four times less than the average occurrence rate recently obtained from the Kepler space mission after 44 days of operation. Comparison of the observed Ks vs. V-Ks diagram with a diagram based on the Besancon model shows significant effects of both distance and reddening in the investigated direction of the sky. We demonstrate that the best model indicates the presence of absorbing clouds at distances 11-13 kpc from the Sun in the minor Carina-Sagittarius Arm.
We have analyzed the data on 16,836 RR Lyrae (RR Lyr) variables observed toward the Galactic bulge during the third phase of the Optical Gravitational Lensing Experiment (OGLE-III), which took place in 2001-2009. Using these standard candles, we show
that the ratio of total to selective extinction toward the bulge is given by R_I=A_I/E(V-I)=1.080+/-0.007 and is independent of color. We demonstrate that the bulge RR Lyr stars form a metal-uniform population, slightly elongated in its inner part. The photometrically derived metallicity distribution is sharply peaked at [Fe/H]=-1.02+/-0.18, with a dispersion of 0.25 dex. In the inner regions (|l|<3, |b|<4) the RR Lyr tend to follow the barred distribution of the bulge red clump giants. The distance to the Milky Way center inferred from the bulge RR Lyr is R_0=8.54+/-0.42 kpc. We report a break in the mean density distribution at a distance of ~0.5 kpc from the center indicating its likely flattening. Using the OGLE-III data, we assess that (4-7)x10^4 type ab RR Lyr variables should be detected toward the bulge area of the on going near-IR VISTA Variables in the Via Lactea (VVV) survey, where the uncertainty partially results from the unknown RR Lyr spatial density distribution within 0.2 kpc from the Galactic center.
We used VLT/VIMOS images in the V band to obtain light curves of extrasolar planetary transits OGLE-TR-111 and OGLE-TR-113, and candidate planetary transits: OGLE-TR-82, OGLE-TR-86, OGLE-TR-91, OGLE-TR-106, OGLE-TR-109, OGLE-TR-110, OGLE-TR-159, OGLE
-TR-167, OGLE-TR-170, OGLE-TR-171. Using difference imaging photometry, we were able to achieve millimagnitude errors in the individual data points. We present the analysis of the data and the light curves, by measuring transit amplitudes and ephemerides, and by calculating geometrical parameters for some of the systems. We observed 9 OGLE objects at the predicted transit moments. Two other transits were shifted in time by a few hours. For another seven objects we expected to observe transits during the VIMOS run, but they were not detected. The stars OGLE-TR-111 and OGLE-TR-113 are probably the only OGLE objects in the observed sample to host planets, with the other objects being very likely eclipsing binaries or multiple systems. In this paper we also report on four new transiting candidates which we have found in the data.
We have surveyed a 6.5 x 6.5 field centered on the globular cluster M56 (NGC 6779) in search for variable stars. We have detected seven variables, among which two objects are new identifications. One of the new variables is an RR Lyrae star, the thir
d such star in M56. Comparison of the new observations and old photometric data for an RV Tauri variable V6 indicates a likely period change in the star. Its slow and negative rate of -0.005+/-0.003 d/yr would disagree with post-AGB evolution, however this could be a result of blue-loop evolution and/or random fluctuations of the period.
We present the results of a search for dwarf novae (DNe) in globular clusters (GCs). It is based on the largest available homogeneous sample of observations, in terms of the time span, number of observations and number of clusters. It includes 16 Gal
actic GCs and yielded two new certain DNe: M55-CV1 and M22-CV2. All previously known systems located in our fields were recovered, too. We surveyed M4, M5, M10, M12, M22, M30, M55, NGC 288, NGC 362, NGC 2808, NGC 3201, NGC 4372, NGC 6362, NGC 6752, omega Cen (NGC 5139) and 47 Tuc (NGC 104). The discovery of two DNe, namely M55-CV1 and M22-CV2, was already reported by Kaluzny et al. (2005) and Pietrukowicz et al. (2005), respectively. In the remaining 14 GCs we found no certain new DNe. Our result raises the total number of known DNe in the Galactic globular clusters to 12 DNe, distributed among 7 clusters. Our survey recovered all three already known erupting cataclysmic variables (CVs) located in our fields, namely M5-V101, M22-CV1, and V4 in the foreground of M30. To assess the efficiency of the survey, we analyzed images with inserted artificial stars mimicking outbursts of the prototype dwarf novae SS Cyg and U Gem. Depending on the conditions, we recovered between 16-100 percent of these artificial stars. The efficiency seems to be predominantly affected by duty cycle/time sampling and much less by distance/magnitude. Except for saturated tiny collapsed cores of M30, NGC 362 and NGC 6752 (and also the dense core of NGC 2808) crowding effects in the V band were avoided by our image subtraction technique augmented with auxiliary unsaturated B-band images. Our results clearly demonstrate that in GCs common types of DNe are very rare indeed. However, great care must be taken before these conclusions can be extended to the CV population in GCs.
