Related papers: Spectral Type and Radial Velocity Variations in Th…
Dwarf carbon (dC) stars, main sequence stars showing carbon molecular bands, were initially thought to be an oxymoron since only AGB stars dredge carbon into their atmospheres. Mass transfer from a former AGB companion that has since faded…
We obtained a series of more than two hundred R-band CCD images for the crowded central (115"x77") region of the metal-poor globular cluster M15 with an angular resolution of 0.5"-0.9" in most images. Optimal image subtraction was used to…
Rotational and radial velocities have been measured for 1589 evolved stars of spectral types F, G and K and luminosity classes IV, III, II and Ib, based on observations carried out with the CORAVEL spectrometers. The precision in radial…
M dwarfs are active stars that exhibit variability in chromospheric emission and photometry at short and long timescales, including long cycles that are related to dynamo processes. This activity also impacts the search for exoplanets…
We analyze the distribution of semiregular variables and Mira stars in the period-luminosity plane. Our sample consists of 6169 oxygen-rich long-period variables in the Large Magellanic Cloud included in the OGLE-III Catalog of Variable…
In this study, we present the results of the relationship between spectral type (ST) and the projected stellar rotational velocity ($vsini$), utilising a sample of approximately 50,000 single stars across a range of evolutionary stages. The…
In order to extend our previous studies of the unexplained phenomenon of cyclic amplitude variations in pulsating red giants, we have used the AAVSO time-series analysis package VSTAR to analyze long-term AAVSO visual observations of 50…
We investigate the variability properties of main sequence stars in the first month of Kepler data, using a new astrophysically robust systematics correction, and find that 60% of stars are more variable then the active Sun. We define low…
The OGLE database is revisited to investigate in more detail the properties of the Fourier parameters. Methodological improvements led us to identify a clear separation among High-Amplitude Delta Scuti (HADS), RRc and RRab stars. The…
Context: Future astrometric missions such as SIM PlanetQuest need very stable reference stars. K giants have large luminosities, which place them at large distances and thus the jitter of their photocenters by companions is relatively…
The Slowly Pulsating B-type (SPB) stars are the upper main-sequence stars on the HR diagram. Their oscillations are high-order, low-degree g-mode and can be used to probe the structure of the radiative zone where is near the outer boundary…
The group of Mira-type and semi-regular variables with similar periodicity (multiperiodicty) is analyzed. They have periods of 230-260 days and 140-150 days and show intervals of periodical (Mira-type) variability with relatively high…
The ninth part of the OGLE-III Catalog of Variable Stars (OIII-CVS) comprises RR Lyr stars in the Small Magellanic Cloud (SMC). Our sample consists of 2475 variable stars, of which 1933 pulsate in the fundamental mode (RRab), 175 are the…
From TESS photometry, 493 mid- to late-B stars with high frequencies (Maia variables) have been identified. The distribution of projected rotational velocities shows that the rotation rates of Maia variables are no different from those of…
$Context.$ Pulsating stars are windows to the physics of stars enabling us to see glimpses of their interior. Not all stars pulsate, however. On the main sequence, pulsating stars form an almost continuous sequence in brightness, except for…
We performed R-band time series observations of the young, metal rich open cluster NGC 2301 for 12 nights in Feb. 2004. B images were also obtained and color magnitude diagrams, having limits of R=19.5 and B=21.5, were produced. Only asmall…
We investigate the red supergiant (RSG) content of the SMC and LMC using multi-object spectroscopy on a sample of red stars previously identified by {\it BVR} CCD photometry. We obtained high accuracy ($<1$ km s$^{-1}$) radial velocities…
Here we present the discovery of three unusual long-term variables found in the Digital Access to a Sky Century at Harvard (DASCH) project, with ~1 magnitude variations in their lightcurves on ~10-100 yr timescales. They are all…
Using the Hamilton Echelle Spectrograph at Lick Observatory, we have obtained precise radial velocities (RVs) of a sample of 373 G- and K-giant stars over more than 12 years, leading to the discovery of several single and multiple planetary…
I concisely review the history, applications, and recent developments pertaining to radial velocity (RV) observations of classical pulsating stars. The focus lies on type-I (classical) Cepheids, although the historical overview and most…