The ACS LCID Project. VIII. The short-period Cepheids of Leo A

Abstract

We present the results of a new search for variable stars in the Local Group dwarf galaxy Leo A, based on deep photometry from the Advanced Camera for Surveys onboard the Hubble Space Telescope. We detected 166 bona fide variables in our field, of which about 60 percent are new discoveries, and 33 candidate variables. Of the confirmed variables, we found 156 Cepheids, but only 10 RR Lyrae stars despite nearly 100 percent completeness at the magnitude of the horizontal branch. The RR Lyrae stars include 7 fundamental and 3 first-overtone pulsators, with mean periods of 0.636 and 0.366 day, respectively. From their position on the period-luminosity (PL) diagram and light-curve morphology, we classify 91, 58, and 4 Cepheids as fundamental, first-overtone, and second-overtone mode Classical Cepheids (CC), respectively, and two as population II Cepheids. However, due to the low metallicity of Leo A, about 90 percent of the detected Cepheids have periods shorter than 1.5 days. Comparison with theoretical models indicate that some of the fainter stars classified as CC could be Anomalous Cepheids. We estimate the distance to Leo A using the tip of the RGB (TRGB) and various methods based on the photometric and pulsational properties of the Cepheids and RR Lyrae stars. The distances obtained with the TRGB and RR Lyrae stars agree well with each other while that from the Cepheid PL relations is somewhat larger, which may indicate a mild metallicity effect on the luminosity of the short-period Cepheids. Due to its very low metallicity, Leo A thus serves as a valuable calibrator of the metallicity dependencies of the variable star luminosities.

arXiv comment16 pages, 13 figures. MNRAS, in press

References in corpus (39)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• A large stellar evolution database for population synthesis studies. I. Scaled solar models and isochrones
• The Photometric Performance and Calibration of the HST Advanced Camera For Surveys
• Updated Electron-Conduction Opacities: The Impact on Low-Mass Stellar Models
• Tip of the Red Giant Branch Distances. II. Zero-Point Calibration
• Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
• The HST Key Project on the Extragalactic Distance Scale XIII. The Metallicity Dependence of the Cepheid Distance Scale
• The influence of chemical composition on the properties of Cepheid stars. II-The iron content
• The Effect of Metallicity on Cepheid-Based Distances
• A multi-color and Fourier study of RR Lyrae variables in the globular cluster NGC 5272 (M3)
• Leo A: A Late-Blooming Survivor of the Epoch of Reionization in the Local Group
• The ACS LCID project. III. The star formation history of the Cetus dSph galaxy: a post-reionization fossil
• Insights into the Cepheid distance scale
• Metal abundances of RR Lyrae stars in the bar of the Large Magellanic Cloud
• A new analysis of the Red Giant Branch "Tip" distance scale and the value of the Hubble constant
• WFPC2 Observations of Leo A: A Predominantly Young Galaxy within the Local Group
• Variable Stars in Leo A: RR Lyraes, Short-period Cepheids, and Implications on Stellar Content
• Calibrating the Cepheid Period-Luminosity relation from the infrared surface brightness technique II. The effect of metallicity, and the distance to the LMC
• Deep HST Imaging of IC 1613. I. Variable Stars and Distance
• Oxygen and Nitrogen in Leo A and GR 8
• The ACS LCID Project. I. Short-Period Variables in the Isolated Dwarf Spheroidal Galaxies Cetus & Tucana
• The Variable Stars and Blue Horizontal Branch of the Metal-Rich Globular Cluster NGC 6441
• On the extended structure of the Phoenix dwarf galaxy
• Cepheids in external galaxies. I. The maser-host galaxy NGC 4258 and the metallicity dependence of P-L and P-W relations
• New period-luminosity and period-color relations of classical Cepheids: III. Cepheids in SMC
• Period-Luminosity Relations Derived from the OGLE-III Fundamental Mode Cepheids
• Full-Fledged Dwarf Irregular Galaxy Leo A
• Deep HST Imaging of Sextans A. II. Cepheids and Distance
• The Evolutionary Status of M3 RR Lyrae Variables: Breakdown of the Canonical Framework?
• RR Lyrae variables in Galactic globular clusters: IV. Synthetic HB and RR Lyrae predictions
• The ACS LCID Project. II. Faint Variable Stars in the Isolated Dwarf Irregular Galaxy IC1613
• The variable star population in Phoenix: coexistence of Anomalous and short-period Classical Cepheids, and detection of RR Lyrae variables
• New period-luminosity and period-color relations of classical Cepheids. IV. The low-metallicity galaxies IC 1613, WLM, Pegasus, Sextans A and B, and Leo A in comparison to SMC
• Synthetic properties of bright metal-poor variables. I. "Anomalous" Cepheids
• The Oldest Stars of the Extremely Metal-Poor Local Group Dwarf Irregular Galaxy Leo A
• Temperature Differences in the Cepheid Instability Strip Require Differences in the Period-Luminosity Relation in Slope and Zero Point
• Variable Stars in the Cetus dSph Galaxy: Population Gradients and Connections with the Star Formation History
• On the second overtone stability among SMC Cepheids
• On the central helium-burning variable stars of the LeoI dwarf spheroidal galaxy

Cited by in corpus (25)

• The dynamics of isolated Local Group galaxies
• The ACS LCID Project: On the origin of dwarf galaxy types: a manifestation of the halo assembly bias?
• The ACS LCID project. X. The Star Formation History of IC 1613: Revisiting the Over-Cooling Problem
• The Carnegie-Chicago Hubble Program. II. The Distance to IC 1613: The Tip of the Red Giant Branch and RR Lyrae Period-Luminosity Relations
• Variable stars in Local Group Galaxies - II. Sculptor dSph
• Search for RR Lyrae stars in DES ultra-faint systems: Grus I, Kim 2, Phoenix II, and Grus II
• Weak Galactic Halo--Fornax dSph Connection from RR Lyrae Stars
• The ISLAnds Project III: Variable Stars in Six Andromeda Dwarf Spheroidal Galaxies
• Toward an internally consistent astronomical distance scale
• The ISLANDS project I: Andromeda XVI, An Extremely Low Mass Galaxy not Quenched by Reionization
• RR Lyrae-based Distances for 39 Nearby Dwarf Galaxies Calibrated to Gaia eDR3
• Solo dwarfs II: The stellar structure of isolated Local Group dwarf galaxies
• Integrated-light analyses vs. colour-magnitude diagrams - II. Leo A, an extremely young dwarf in the Local Group
• Near-Infrared Stellar Populations in the metal-poor, Dwarf irregular Galaxies Sextans A and Leo A
• Variable stars in Local Group Galaxies -- V. The fast and early evolution of the low-mass Eridanus II dSph galaxy
• Metallicity of Galactic RR Lyrae from Optical and Infrared Light Curves: II. Period-Fourier-Metallicity Relations for First Overtone RR Lyrae
• Carbon stars as standard candles -- III. Un-binned maximum likelihood fitting and comparison with TRGB estimations
• Homogeneous Photometry VI: Variable Stars in the Leo I Dwarf Spheroidal Galaxy
• Chemistry in the dIrr galaxy Leo A
• Variability search in M 31 using Principal Component Analysis and the Hubble Source Catalog
• The frozen outskirts: a cold Hubble flow and the mass of the Local Group
• The Hubble Catalog of Variables
• Star clusters in the dwarf irregular galaxy Leo A
• Star clusters and young populations in the dwarf irregular galaxy Leo A
• The ionization structure and chemical history in isolated H ii regions of dwarf galaxies with VIMOS/IFU II. The Leo A galaxy