638 research outputs found
Double-Mode Radial Pulsations among RR Lyrae Stars
Double-mode RR Lyr type stars are important for studies of properties of
horizontal-branch stars. In particular, two periods coupled with spectral
properties give a mass estimate that is independent of evolutionary models.
Here, we present 59 new Galactic double-mode RR Lyr stars found in the LINEAR
survey data with the fundamental radial mode and the first overtone exited (RRd
stars). These stars may be useful for constraining the mass-metallicity
relation for field horizontal-branch stars. Also, new RRd stars found in the
LMC by EROS-II are verified. We present the updated Petersen diagram and the
distribution of the fundamental mode periods. Comments on selected variable
stars from LINEAR and LMC EROS-II surveys are also presented, including very
rare objects: the third known mode-switching RR Lyr and Cepheid pulsating
simultaneously in three radial modes.Comment: large tables included as ancillary file
ASAS Eclipsing Binaries with Observed High Period Change Rates
We present 31 bright eclipsing contact and semi-detached binaries that showed
high period change rates in a 5 year interval in observations by the All-Sky
Automated Survey (ASAS). The time-scales of these changes range from only 50 up
to 400 kyr. The orbital periods of 10 binaries are increasing and of 21 are
decreasing, and even a larger excess is seen in contact binaries, where the
numbers are 5 and 17, respectively. Period change has previously been noticed
for only two of these binaries; our observations confirmed a secular period
drift for SV Cen and period oscillations for VY Cet. The spectroscopic
quadruple system V1084 Sco shows both period change and brightness modulation.
All investigated binaries were selected from a sample of 1711 (1135 contact and
576 semi-detached) that fulfilled all criteria of data quality. We also
introduce a "branch" test to check if luminosity changes on part of the
binary's photosphere has led to a spurious or poorly characterized period
change detection.Comment: 12 pages, 13 figures, submitted to MNRA
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