Chromospherically Active Stars in the Galactic Bulge

Abstract

We present the results from the discovery and study of ~3000 chromospherically active giant and subgiant stars toward the Galactic bulge. We find that these stars are predominantly RS CVn binaries with rotation periods between 10 and 100 days. We discover that the average rotational period of these stars decreases with their distance from the Galactic plane. We find that the primary stars in the RS CVn systems are predominantly first-ascent giants. Our research also suggests that, if these stars have spot cycles like the sun, then the cycle period must be longer than 10 years on average. We confirm that the amplitude of the spot-induced modulations observed in the light curves of these objects is generally larger at minimum light than at maximum. Furthermore, we confirm that the amplitudes of the modulations due to stellar spots generally increases as the observed change in average brightness increases. We find no evidence for a relationship between a CA star's brightness and its rotational period. However, the average period does increase with colour for stars with periods >~30 days.

Accepted AJ. 18 pages, 17 figures (at low resolution to meet astro-ph file size requirements)

References in corpus (6)

• Microlensing Optical Depth towards the Galactic Bulge Using Clump Giants from the MACHO Survey
• Variability-Selected Quasars in MACHO Project Magellanic Cloud Fields
• Microlensing optical depth toward the Galactic Bulge using bright sources from OGLE-II
• The Large-Scale Extinction Map of the Galactic Bulge from the MACHO Project Photometry
• Variability-selected QSO candidates in OGLE-II Galactic Bulge fields
• A Search for Stellar Obscuration Events due to Dark Clouds

Cited by in corpus (12)

• The Catalina Surveys Periodic Variable Star Catalog
• Quantifying Quasar Variability As Part of a General Approach To Classifying Continuously Varying Sources
• Gaia Data Release 3: All-sky classification of 12.4 million variable sources into 25 classes
• Ultra-short Period Binaries from the Catalina Surveys
• Gaia Data Release 3: Cross-match of Gaia sources with variable objects from the literature
• A multi-wavelength view of the neutron star binary 1FGL J1417.7--4402: A progenitor to canonical millisecond pulsars
• $12660$ spotted stars toward the OGLE Galactic bulge fields
• PSR J1306--40: An X-ray Luminous Redback with an Evolved Companion
• A classification algorithm for time-domain novelties in preparation for LSST alerts: Application to variable stars and transients detected with DECam in the Galactic Bulge
• A catalogue of oxygen-rich pulsating giants in the galactic halo and the Sagittarius stream
• Investigating stellar variability in the open cluster region NGC 381
• Activity cycles in RS CVn type stars