Discovery of Bright Galactic R Coronae Borealis and DY Persei Variables: Rare Gems Mined from ACVS

Abstract

We present the results of a machine-learning (ML) based search for new R Coronae Borealis (RCB) stars and DY Persei-like stars (DYPers) in the Galaxy using cataloged light curves from the All-Sky Automated Survey (ASAS) Catalog of Variable Stars (ACVS). RCB stars - a rare class of hydrogen-deficient carbon-rich supergiants - are of great interest owing to the insights they can provide on the late stages of stellar evolution. DYPers are possibly the low-temperature, low-luminosity analogs to the RCB phenomenon, though additional examples are needed to fully establish this connection. While RCB stars and DYPers are traditionally identified by epochs of extreme dimming that occur without regularity, the ML search framework more fully captures the richness and diversity of their photometric behavior. We demonstrate that our ML method can use newly discovered RCB stars to identify additional candidates within the same data set. Our search yields 15 candidates that we consider likely RCB stars/DYPers: new spectroscopic observations confirm that four of these candidates are RCB stars and four are DYPers. Our discovery of four new DYPers increases the number of known Galactic DYPers from two to six; noteworthy is that one of the new DYPers has a measured parallax and is m ~ 7 mag, making it the brightest known DYPer to date. Future observations of these new DYPers should prove instrumental in establishing the RCB connection. We consider these results, derived from a machine-learned probabilistic classification catalog, as an important proof-of-concept for the efficient discovery of rare sources with time-domain surveys.

arXiv comment18 pages, 2 new figures, accepted for publication in ApJ

References in corpus (31)

• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The USNO-B Catalog
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• The VizieR database of Astronomical Catalogues
• The Infrared Astronomical Mission AKARI
• Spectral Irradiance Calibration in the Infrared. XIV: the Absolute Calibration of 2MASS
• Population synthesis for double white dwarfs I.Close detached systems
• Berkeley Supernova Ia Program I: Observations, Data Reduction, and Spectroscopic Sample of 582 Low-Redshift Type Ia Supernovae
• On Machine-Learned Classification of Variable Stars with Sparse and Noisy Time-Series Data
• Detailed Analysis of Early to Late-Time Spectra of Supernova 1993J
• Automated supervised classification of variable stars I. Methodology
• Random forest automated supervised classification of Hipparcos periodic variable stars
• Optimal Time-Series Selection of Quasars
• Very Large Excesses of 18O in Hydrogen-Deficient Carbon and R Coronae Borealis Stars: Evidence for White Dwarf Mergers
• The MACHO Project LMC Variable Star Inventory: X. The R Coronae Borealis Stars
• V605 Aql: The Older Twin of Sakurai's Object
• Active Learning to Overcome Sample Selection Bias: Application to Photometric Variable Star Classification
• New Magellanic Cloud R Coronae Borealis and DY Per type stars from the EROS-2 database: the connection between RCBs, DYPers and ordinary carbon stars
• Fluorine in R Coronae Borealis Stars
• Variable Faint Optical Sources Discovered by Comparing POSS and SDSS Catalogs
• The Circumstellar Environment of R Coronae Borealis: White Dwarf Merger or Final Helium Shell Flash?
• Tracking down R Coronae Borealis stars from their mid-infrared WISE colours
• R Coronae Borealis stars in the Galactic Bulge discovered by EROS-2
• Tycho 2 stars with infrared excess in the MSX Point Source Catalogue
• Discovery of Five New R Coronae Borealis Stars in the MACHO Galactic Bulge Database
• EROS 2 photometry of probable R Coronae Borealis stars in the Small Magellanic Cloud
• The All Sky Automated Survey. A Catalog of almost 3900 variable stars
• New R Coronae Borealis stars discovered in OGLE-III Galactic Bulge fields from their mid- and near- infrared properties
• Circumstellar HI and CO around the carbon stars V1942 Sgr and V CrB
• V532 Oph is a New R Coronae Borealis Star
• NSV 11154 Is a New R Coronae Borealis Star

Cited by in corpus (14)

• Construction of a Calibrated Probabilistic Classification Catalog: Application to 50k Variable Sources in the All-Sky Automated Survey
• Gamma-Ray Active Galactic Nucleus Type through Machine-Learning Algorithms
• The ongoing pursuit of R Coronae Borealis stars: ASAS-3 survey strikes again
• Color Me Intrigued: the Discovery of iPTF 16fnm, a Supernova 2002cx-like Object
• An HI Imaging Survey of Asymptotic Giant Branch Stars
• A Spectral Classification System for Hydrogen-deficient Carbon Stars
• Luminous AGB variables in the dwarf Irregular Galaxy, NGC 3109
• Long-term Stellar Variability in the Galactic Centre Region
• Are DY\,Persei stars cooler cousins of R Coronae Borealis stars?
• Abundance analyses of the new R Coronae Borealis stars: ASAS-RCB-8 and ASAS-RCB-10
• R Coronae Borealis Stars in M31 from the Palomar Transient Factory
• Mid-Infrared Variations of R Coronae Borealis Stars
• The variable V381 Lac and its possible connection with the R CrB phenomenon
• High-resolution optical spectroscopy of the R Coronae Borealis star V532 Ophiuchi at maximum light