Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

Abstract

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]

56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Science

References in corpus (143)

• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• Cosmological Constraints from the SDSS Luminous Red Galaxies
• Cats and Dogs, Hair and A Hero: A Quintet of New Milky Way Companions
• Stellar Chemical Signatures And Hierarchical Galaxy Formation
• A Triple Main Sequence in the Globular Cluster NGC 2808
• Updated Electron-Conduction Opacities: The Impact on Low-Mass Stellar Models
• A Faint New Milky Way Satellite in Bootes
• A helium spread among the main sequence stars in NGC 2808
• The ACS Survey of Galactic Globular Clusters. III. The Double Subgiant Branch of NGC 1851
• The properties of Galactic globular cluster sub-systems
• A Comparison of Elemental Abundance Ratios in Globular Clusters, Field Stars, and Dwarf Spheroidal Galaxies
• The RR Lyrae Period-Luminosity Relation. I. Theoretical Calibration
• On the self-enrichment scenario of galactic globular clusters: Constraints on the IMF
• Galactic Globular Cluster Relative Ages. II
• The exotic chemical composition of the Sagittarius dwarf Spheroidal galaxy
• Origin of the abundance patterns in Galactic globular clusters: constraints on dynamical and chemical properties of globular clusters
• Comparing the properties of local globular cluster systems: implications for the formation of the Galactic halo
• A multi-color and Fourier study of RR Lyrae variables in the globular cluster NGC 5272 (M3)
• Super Helium-Rich Population and the Origin of Extreme Horizontal-Branch Stars in Globular Clusters
• Spectroscopic ages and metallicities of stellar populations: validation of full spectrum fitting
• The Detailed Star Formation History in the Spheroid, Outer Disk, and Tidal Stream of the Andromeda Galaxy
• The double Subgiant Branch of NGC 1851: the role of the CNO abundance
• An abundance analysis of bright giants in the globular cluster NGC 1851
• The QUEST RR Lyrae Survey II: The Halo Overdensities in the First Catalog
• The fraction of second generation stars in Globular Clusters from the analysis of the Horizontal Branch
• The origin of the double main sequence in Omega Centauri: Helium enrichment due to gas fueling from its ancient host galaxy ?
• Accretion relicts in the solar neighbourhood: debris from omegaCen's parent galaxy
• The Chemical Enrichment History of the Large Magellanic Cloud
• NGC 6441: another indication for a very high helium content in Globular Cluster stars
• The Luminosities and Distance Scales of Type II Cepheid and RR Lyrae variables
• A Robust Method for the Analysis of Integrated Spectra from Globular Clusters using Lick Indices
• Chemical Abundances and Kinematics in Globular Clusters and Local Group Dwarf Galaxies and Their Implications for Formation Theories of the Galactic Halo
• Globular clusters and the formation of the outer Galactic halo
• The Peculiar Horizontal Branch Morphology of the Galactic Globular Clusters NGC 6388 and NGC 6441: new insights from UV observations
• Multivariate Analysis of Globular Cluster's Horizontal Branch Morphology: searching for the second parameter
• A model for the Globular Cluster extreme anomalies
• The RR Lyrae Period - K Luminosity relation for Globular Clusters: an observational approach
• A large stellar evolution database for population synthesis studies. IV. Integrated properties and spectra
• Detection of the Main Sequence Turn-off of a Newly Discovered Milky Way Halo Structure in the Triangulum-Andromeda Region
• HS0702+6043: A star showing both short-period p-mode and long-period g-mode oscillations
• Variable stars in the newly discovered Milky Way satellite in Bootes
• Kinematic Decoupling of Globular Clusters with Extended Horizontal-Branch
• Evidence for Distinct Components of the Galactic Stellar Halo from 838 RR Lyrae Stars Discovered in the LONEOS-I Survey
• On the Origin of the High Helium Sequence in $\omega$ Centauri
• The First Empirical Mass Loss Law for Population II Giants
• The period-luminosity relation for type II Cepheids in globular clusters
• ACS photometry of extended, luminous globular clusters in the outskirts of M31
• Origin of Abundance Inhomogeneity in Globular Clusters
• Na-O Anticorrelation and Horizontal Branches. V. The Na-O anticorrelation in NGC 6441 from Giraffe spectra
• 3D Numerical Experimentation on the Core Helium Flash of low-mass Red Giants
• First full evolutionary computation of the He-flash induced mixing in Population II stars
• HST/WFPC2 Color-Magnitude Diagrams for Globular Clusters in M31
• Revealing Substructure in the Galactic Halo - The SEKBO RR Lyrae Survey
• Structural Parameters of the Hot Pulsating B Subdwarf PG 1219+534 from Asteroseismology
• Whiting 1: the youngest globular cluster associated with the Sgr dSph
• Long period variables in 47 Tuc: direct evidence for lost mass
• A critical test of empirical mass loss formulae applied to individual giants and supergiants
• A pulsational distance to Omega Centauri based on Near-Infrared Period-Luminosity relations of RR Lyrae stars
• A possible solution for the lack of EHB binaries in globular clusters
• Family ties: abundances in Terzan 7, a Sgr dSph globular cluster
• Variable Stars in the Newly Discovered Milky Way Dwarf Spheroidal Satellite Canes Venatici I
• RR Lyrae Stars in the Bootes dSph
• MOST photometry of the RRd Lyrae variable AQ Leo: Two radial modes, 32 combination frequencies, and beyond
• Evidence for an Overluminosity of the Variable Star RR Lyr, and a Revised Distance to the LMC
• RR Lyrae variables in Galactic globular clusters: IV. Synthetic HB and RR Lyrae predictions
• On the newly discovered Canes Venatici II dSph galaxy
• The Century Survey Galactic Halo Project III: A Complete 4300 deg^2 Survey of Blue Horizontal Branch Stars in the Metal-Weak Thick Disk and Inner Halo
• Dust, pulsation, chromospheres and their role in driving mass loss from red giants in Galactic globular clusters
• Age Constraints for an M31 Globular Cluster from Main Sequence Photometry
• A Spitzer Space Telescope Atlas of omega Centauri: The Stellar Population, Mass Loss, and the Intracluster Medium
• The infrared JHK light curves of RR Lyr
• Helium self--enrichment and the second parameter problem in M3 and M13
• The lack of close binaries among hot horizontal branch stars in NGC6752
• Internal rotation of subdwarf B stars: limiting cases and asteroseismological consequences
• Multicolour photometry of Balloon 090100001: linking the two classes of pulsating hot subdwarfs
• GALEX Ultraviolet Photometry of Globular Clusters in M31: Three Year Results and a Catalog
• The Period-Luminosity Relation of RR Lyrae Stars in the SDSS Photometric System
• Fe-bump instability: the excitation of pulsations in subdwarf B and other low-mass stars
• The Dwarf Spheroidal Companions to M31: Variable Stars in Andromeda I and Andromeda III
• Is mass loss along the red giant branch of globular clusters sharply peaked? The case of M3
• On the Origin of Bimodal Horizontal-Branches in Massive Globular Clusters: The Case of NGC 6388 and NGC 6441
• The link between chemical anomalies along the red giant branch and the horizontal branch extension in globular clusters
• Outer Versus Inner Halo Globular Clusters: NGC 7492 Abundances
• On constructing horizontal branch models
• The Hottest Horizontal-Branch Stars in omega Centauri - Late Hot Flasher vs. Helium Enrichment
• On the Predicted and Observed Color Boundaries of the RR Lyrae Instability Strip as a Function of Metallicity
• Surface Brightness and Stellar Populations at the Outer Edge of the Large Magellanic Cloud: No Stellar Halo Yet
• The Horizontal Branch of NGC 1851: Constraints on the Cluster Subpopulations
• On the remote Galactic globular cluster NGC 2419
• On the Horizontal Branch of the Galactic Globular NGC2808
• Synthetic properties of bright metal-poor variables. II. BL Her stars
• The shortest modulation period Blazhko RR Lyrae star: SS Cnc
• Metal abundances of RR Lyrae stars in the metal rich globular cluster NGC 6441
• Image-Subtraction Photometry of Variable Stars in the Globular Clusters NGC 6388 and NGC 6441
• Abundance anomalies in hot horizontal branch stars of the galactic globular cluster NGC 1904
• A Low Solar Oxygen Abundance from the First Overtone OH Lines
• A comprehensive study of Cepheid variables in the Andromeda galaxy. Period distribution, blending and distance determination
• The Case of the Off-Center, Levitating Bar in the Large Magellanic Cloud
• The star formation history of damped Lyman alpha absorbers
• Variable stars in the Fornax dSph Galaxy. I. The Globular Cluster Fornax 4
• Far-Ultraviolet Observations of the Globular Cluster NGC 2808 Revisited: Blue Stragglers, White Dwarfs and Cataclysmic Variables
• A Spectroscopic Survey for Omega Centauri Members at and beyond the Cluster Tidal Radius
• Is a binary fraction-age relation responsible for the lack of EHB binaries in globular clusters?
• The Look-back Time Evolution of Far-UV Flux from Elliptical Galaxies: The Fornax Cluster and Abell 2670
• The Dog on the Ship: The "Canis Major Dwarf Galaxy" as an Outlying Part of the Argo Star System
• Unveiling the core of the Globular Cluster M15 in the Ultraviolet
• The Galex Ultraviolet Variability (GUVV) Catalog
• Homogeneous Photometry V: The Globular Cluster NGC 4147
• The Wendelstein Calar Alto Pixellensing Project (WeCAPP): The M31 Variable Star Catalogue
• Stellar Evolution and Variability in the Pre-ZAHB Phase
• Discovery of > 200 RR Lyrae Variables in M62: An Oosterhoff I Globular Cluster with a Predominantly Blue HB
• Deep HST Photometry of NGC 6388: Age and Horizontal Branch Luminosity
• Observations and asteroseismic analysis of the rapidly pulsating hot B subdwarf PG 0911+456
• Kinematics of RHB stars to trace the structure of the galaxy
• Chemical Abundance Study of One Red Giant Star in NGC 5694 : A Globular Cluster with Dwarf Spheroidals' Chemical Signature?
• Long period variables in the globular cluster 47 Tuc: radial velocity variations
• The Century Survey Galactic Halo Project II: Global Properties and the Luminosity Function of Field Blue Horizontal Branch Stars
• Distant Field BHB Stars III: Identification of a probable outer halo stream at Galactocentric distance r = 70 kpc
• A Semi-Empirical Study of the Mass Distribution of Horizontal Branch Stars in M3 (NGC 5272)
• Hot subdwarfs in the Galactic Bulge
• GALEX Ultraviolet Photometry of Globular Clusters in M31
• Large-Amplitude Ultraviolet Variations in the RR Lyrae Star ROTSE-I J143753.84+345924.8
• UVES observations of the Canis Major overdensity
• Spatial and Velocity clumping in an SDSS blue horizontal branch star catalogue
• Hot Flashers and He Dwarfs in Galactic Globulars
• Kinematics of Nearby Subdwarf Stars
• Stellar populations in the Canis Major over-density
• Highly He-Rich Matter Dredged Up by Extra Mixing through Stellar Encounters in Globular Clusters
• Testing the AGB Scenario as the Origin of the Extreme-Helium Population in omega Centauri
• Observational consequences of the hypothesized helium rich stellar population in Omega Centauri
• Searching for merger debris in the Galactic halo: Chemodynamical evidence based on local blue HB stars
• Ultra-Low Amplitude Cepheids in the Large Magellanic Cloud
• First stars as a possible origin for the helium-rich population in omega Centauri
• Various Modes of Helium Mixing in Globular Cluster Giants and Their Possible Effects on the Horizontal Branch Morphology
• Kinematics of the Galactic Halo from Horizontal Branch stars in the Hamburg/ESO Survey
• Surface pollution of main-sequence stars through encounters with AGB ejecta in omega Centauri
• Overluminous Blue Horizontal Branch Stars Formed by Low Mass Companions
• Far-Ultraviolet Observations of RR Lyrae Stars in the Core of NGC 1851
• Colour-colour diagrams and extragalactic globular cluster ages. Systematic uncertainties using the (V-K)-(V-I) diagram
• Helium preenrichment in the star-forming regions
• Tidal Interactions of Red Giants with Environment Stars in Globular Clusters
• Observations of the Hot Horizontal-Branch Stars in the Metal-Rich Bulge Globular Cluster NGC 6388 - Indications of Helium Enrichment and a Lesson in Crowded Field Spectroscopy
• Variable Star Candidates in an ACS Field of M31

Cited by in corpus (248)

• The propagation of uncertainties in stellar population synthesis modeling III: model calibration, comparison, and evaluation
• Asteroseismology of Solar-Type and Red-Giant Stars
• The Ages of 55 Globular Clusters as Determined Using an Improved delta V_TO^HB Method Along with Color-Magnitude Diagram Constraints, and Their Implications for Broader Issues
• The Catalina Surveys Periodic Variable Star Catalog
• The ACS Survey of Galactic Globular Clusters. IX. Horizontal Branch Morphology and the Second Parameter Phenomenon
• Hot subluminous stars
• Asteroseismology of old open clusters with Kepler: direct estimate of the integrated RGB mass loss in NGC6791 and NGC6819
• Testing a Predictive Theoretical Model for the Mass Loss Rates of Cool Stars
• The Zwicky Transient Facility Catalog of Periodic Variable Stars
• What is a globular cluster? An observational perspective
• Neutrino and axion bounds from the globular cluster M5 (NGC 5904)
• Probing the Outer Galactic halo with RR Lyrae from the Catalina Surveys
• Light Curve Templates and Galactic Distribution of RR Lyrae Stars from Sloan Digital Sky Survey Stripe 82
• Machine-Learned Identification of RR Lyrae Stars from Sparse, Multi-band Data: the PS1 Sample
• Helium enhanced stars and multiple populations along the horizontal branch of NGC2808: direct spectroscopic measurements
• Measuring the vertical age structure of the Galactic disc using asteroseismology and SAGA
• Leo P: An Unquenched Very Low-Mass Galaxy
• Piercing the Milky Way: an all-sky view of the Orphan Stream
• Exploring the Variable Sky with LINEAR. II. Halo Structure and Substructure Traced by RR Lyrae Stars to 30 kpc
• Discovery of $\sim$ 9,000 new RR Lyrae in the Southern Catalina Surveys
• Evidence for a Milky Way Tidal Stream Reaching Beyond 100 kpc
• Wide-field Infrared Survey Explorer (WISE) Catalog of Periodic Variable Stars
• Global and non-global parameters of horizontal branch morphology of globular clusters
• Chemo-kinematics of the $Gaia$ RR Lyrae: the halo and the disc
• Tidal Signatures in the Faintest Milky Way Satellites: The Detailed Properties of Leo V, Pisces II and Canes Venatici II
• The MUCHFUSS project - Searching for hot subdwarf binaries with massive unseen companions: Survey, target selection and atmospheric parameters
• FORS2/VLT survey of Milky Way globular clusters II. Fe and Mg abundances of 51 Milky Way globular clusters on a homogeneous scale
• Weak Galactic halo--dwarf spheroidal connection from RR Lyrae stars
• Old-Aged Stellar Population Distance Indicators
• The ACS LCID Project. I. Short-Period Variables in the Isolated Dwarf Spheroidal Galaxies Cetus & Tucana
• The EPOCH Project: I. Periodic variable stars in the EROS-2 LMC database
• An Exoplanet's Response to Anisotropic Stellar Mass-Loss During Birth and Death
• Evidence for a sharp structure variation inside a red-giant star
• The Horizontal Branch in the UV Colour Magnitude Diagrams. II. The case of M3, M13 and M79
• Fourier analysis of non-Blazhko ab-type RR Lyrae stars observed with the Kepler space telescope
• A Package for the Automated Classification of Periodic Variable Stars
• Particle-physics constraints from the globular cluster M5: Neutrino Dipole Moments
• Fourteen candidate RR Lyrae star streams in the inner Galaxy
• Gaia Data Release 1 - The Cepheid & RR Lyrae star pipeline and its application to the south ecliptic pole region
• The first all-sky view of the Milky Way stellar halo with Gaia+2MASS RR Lyrae
• Effects of Helium Enrichment in Globular Clusters I.Theoretical Plane with PGPUC stellar evolution code
• Low-resolution spectroscopy of main sequence stars belonging to 12 Galactic globular clusters. I. CH and CN band strength variations
• Milky Way demographics with the VVV survey. IV. PSF photometry from almost one billion stars in the Galactic bulge and adjacent southern disk
• The RR Lyrae variables and Horizontal Branch of NGC6656 (M22)
• Helium and Multiple Populations in the Massive Globular Cluster NGC6266 (M62)
• La Silla QUEST RR Lyrae Star Survey: Region I
• The Leo IV dwarf spheroidal galaxy: color-magnitude diagram and pulsating stars
• The complex case of V445 Lyr observed with Kepler: Two Blazhko modulations, a non-radial mode, possible triple mode RR Lyrae pulsation, and more
• Variable stars in Local Group Galaxies - II. Sculptor dSph
• Stellar Population Variations in the Milky Way's Stellar Halo
• Self-consistent predictions for LIER-like emission lines from post-AGB stars
• BayeSED: A General Approach to Fitting the Spectral Energy Distribution of Galaxies
• Stellar Archaeology in the Galactic halo with Ultra-Faint Dwarfs: VII. Hercules
• Variable stars in the VVV globular clusters. I. 2MASS-GC02 and Terzan10
• FSR 1716: A new Milky Way Globular Cluster confirmed using VVV RR Lyrae stars
• On the use of field RR Lyrae as Galactic probes: I. The Oosterhoff dichotomy based on fundamental variables
• Variable stars in the ultra-faint dwarf spheroidal galaxy Ursa Major I
• Exploring the variable stars in the globular cluster NGC5024 (M53): New RR Lyrae and SX Phoenicis stars
• The Globular Cluster NGC 5286. II. Variable Stars
• New RR Lyrae variables in binary systems
• Connecting planets around horizontal branch stars with known exoplanets
• A New Census of the variable star population in the Globular Cluster NGC 2419
• Search for RR Lyrae stars in DES ultra-faint systems: Grus I, Kim 2, Phoenix II, and Grus II
• Constraints on the Distance Moduli, Helium and Metal Abundances, and Ages of Globular Clusters from their RR Lyrae and Non-Variable Horizontal-Branch Stars. I. M3, M15, and M92
• UV Properties of Galactic Globular Clusters with GALEX II. Integrated colors
• Chemical evolution of classical and ultra-faint dwarf spheroidal galaxies
• Discovery of distant RR Lyrae stars in the Milky Way using DECam
• Discovery of RR Lyrae Stars in the Nuclear Bulge of the Milky Way
• Evidence for Galactic disc RR~Lyrae stars in the Solar neighbourhood
• UV Properties of Galactic Globular Clusters with GALEX I. The Color-Magnitude Diagrams
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. VII. Implications from the Nearly Universal Nature of Horizontal Branch Discontinuities
• Unmixing the Galactic Halo with RR Lyrae tagging
• The ACS LCID Project. VIII. The short-period Cepheids of Leo A
• The globular cluster system of the Milky Way: accretion in a cosmological context
• Strong RR Lyrae excess in the Hercules-Aquila Cloud
• High-precision distance measurements with classical pulsating stars
• Kinematics of the Palomar 5 stellar stream from RR Lyrae stars
• Variable stars in the field of the Hydra II ultra-faint dwarf galaxy
• A Search for RR Lyrae Stars in Segue 2 and Segue 3
• A comprehensive chemical abundance study of the outer halo globular cluster M 75
• Variable stars in the Globular Cluster NGC 2808
• Metallicity distribution functions of the old populations of the Magellanic Clouds from RR Lyrae stars
• Cyclic variations in O-C diagrams of field RR Lyrae stars as a result of LiTE
• RR Lyrae From Binary Evolution: Abundant, Young and Metal-Rich
• The ISLAnds Project III: Variable Stars in Six Andromeda Dwarf Spheroidal Galaxies
• An empirical mass-loss law for Population II giants from the Spitzer-IRAC survey of Galactic globular clusters
• What drives the ultra-violet colours of passive galaxies?
• Integrated Mass Loss of Evolved Stars in M4 using Asteroseismology
• Characterization of the VVV Survey RR Lyrae Population across the Southern Galactic Plane
• The Swift UVOT Stars Survey: I. Methods and Test Clusters
• Mapping the Tidal Disruption of the Hercules Dwarf: A Wide-Field DECam Imaging Search for RR Lyrae Stars
• The Na-O anticorrelation in horizontal branch stars. V. NGC 6723
• Horizontal-branch morphology and multiple stellar populations in the anomalous globular cluster M22
• Variable stars and stellar populations in Andromeda XXV: III. A central cluster or the galaxy nucleus?
• Time-Series Photometry of Globular Clusters: M62 (NGC 6266), the Most RR Lyrae-Rich Globular Cluster in the Galaxy?
• On the use of field RR Lyrae as Galactic probes: IV. New insights into and around the Oosterhoff dichotomy
• Multiple Populations in Globular Clusters and the Origin of the Oosterhoff Period Groups
• A lack of close binaries among hot horizontal branch stars in globular clusters. II. NGC\,2808
• Near-Infrared Variability Study of the Central 2.3 arcmin x 2.3 arcmin of the Galactic Centre II. Identification of RR Lyrae Stars in the Milky Way Nuclear Star Cluster
• HST/ACS Observations of RR Lyrae Stars in Six Ultra-deep Fields of M31
• Variable stars in the globular cluster NGC 7492. New discoveries and physical parameters determination
• A Re-Evaluation of the Evolved Stars in the Globular Cluster M13
• Charting Unexplored Dwarf Galaxy Territory With RR Lyrae
• A DECam View of the Diffuse Dwarf Galaxy Crater II: Variable Stars
• Spectroscopy of horizontal branch stars in Omega Centauri
• The ZTF Source Classification Project: II. Periodicity and variability processing metrics
• The Na-O anticorrelation in horizontal branch stars. IV. M22
• A detailed census of variable stars in the globular cluster NGC 6333 (M9) from CCD differential photometry
• Dwarf spheroidal satellites of M31: I. Variable stars and stellar populations in Andromeda XIX
• RR Lyrae stars and the horizontal branch of NGC 5904 (M5)
• Absolute Magnitudes and Colors of RR Lyrae stars in DECam Passbands from Photometry of the Globular Cluster M5
• An Updated Census of RR~Lyrae Stars in the Globular Cluster $\omega$~Centauri (NGC\,5139)
• Revisiting the variable star population in NGC~6229 and the structure of the Horizontal Branch
• Binary stars and the UVX in early type galaxies
• Peculiar double-periodic pulsation in RR Lyrae stars of the OGLE collection. I. Long-period stars with dominant radial fundamental mode
• An Overview of the Rotational Behavior of Metal--Poor Stars
• Serendipitous discovery of RR Lyrae stars in the Leo V ultra-faint galaxy
• Effects of tidally enhanced stellar wind on the horizontal branch morphology of globular clusters
• Empirical determination of the integrated red giant and horizontal branch stellar mass loss in omega Centauri
• Period Change Similarities among the RR Lyrae Variables in Oosterhoff I and Oosterhoff II Globular Systems
• MORGOTH: incorporating horizontal branch modelling into star formation history determinations
• A Census of Variability in Globular Cluster M68 (NGC 4590)
• Slowly cooling white dwarfs in M13 from stable hydrogen burning
• Fundamental properties of nearby stars and the consequences on DeltaY/DeltaZ
• Revisiting binary stars in population synthesis models
• Identification of RR Lyrae stars in multiband, sparsely-sampled data from the Dark Energy Survey using template fitting and Random Forest classification
• Constraints on the Distance Moduli, Helium and Metal Abundances, and Ages of Globular Clusters From Their RR Lyrae and Non-Variable Horizontal-Branch Stars. III. M55 and NGC 6362
• Variable Stars in the Fornax dSph Galaxy. III. The Globular Cluster Fornax 5
• The population of variable stars in M54 (NGC6715)
• On the Use of Field RR Lyrae as Galactic Probes. V. Optical and radial velocity curve templates
• Excess of Ca (and Sc) produced in globular cluster multiple populations: a first census in 77 Galactic globular clusters
• Variable stars in Local Group Galaxies -- V. The fast and early evolution of the low-mass Eridanus II dSph galaxy
• The Panchromatic Hubble Andromeda Treasury II. Tracing the Inner M31 Halo with Blue Horizontal Branch Stars
• Kinematics and Multi Band Period-Luminosity-Metallicity Relation of RR Lyrae Stars via Statistical Parallax
• Milky Way archaeology using RR Lyrae and type II Cepheids I. The Orphan stream in 7D using RR Lyrae stars
• A LAMOST BHB Catalog and Kinematics Therein I: Catalog and Halo Properties
• A New Formation Scenario for the Milky Way Cluster NGC2419
• Some Systematics of Galactic Globular Clusters
• Chemical abundances in the metal-intermediate GC NGC 6723
• Light Element Discontinuities Suggest an Early Termination of Star Formation in the Globular Cluster NGC 6402 (M14)
• Three-Dimensional Structure and Dust Extinction in the Small Magellanic Cloud
• Level of helium enhancement among M3's horizontal-branch stars
• Variable Stars in Large Magellanic Cloud Globular Clusters III: Reticulum
• Globular clusters in the far-ultraviolet: evidence for He-enriched second populations in extra-galactic globular clusters?
• Homogeneous Photometry VI: Variable Stars in the Leo I Dwarf Spheroidal Galaxy
• RR Lyrae Variable Stars in the Crater II Dwarf Galaxy
• Inclusion of Horizontal Branch stars in the derivation of star formation histories of dwarf galaxies: the Carina dSph
• The impact of an updated ${}^{14}N(p,\gamma {)}^{15}O$ reaction rate on advanced evolutionary stages of low-mass stellar models
• Star Cluster Ages in the Gaia Era
• The peculiar properties of horizontal branch stars in omega Centauri
• Variable Stars in Large Magellanic Cloud Globular Clusters I: NGC 1466
• Near-Infrared Variability Study of the Central 2.3 arcmin x 2.3 arcmin of the Galactic Centre I. Catalog of Variable Sources
• Near-infrared Census of RR Lyrae variables in the Messier 3 globular cluster and the Period--Luminosity Relations
• The Variable Star Population of the Globular Cluster B514 in the Andromeda Galaxy
• Red Horizontal Branch stars: an asteroseismic perspective
• The Horizontal Branch of NGC 1851: Constraints from its RR Lyrae Variables
• On the Use of Field RR Lyrae as Galactic Probes. VI. Mixed mode RR Lyrae variables in Fornax and in nearby dwarf galaxies
• Searching for Hot Subdwarf Stars in LAMOST DR1-II. Pure spectroscopic identification method for hot subdwarfs
• Characteristics of bright ab-type RR Lyrae stars from the ASAS and WASP surveys
• On the Oosterhoff dichotomy in the Galactic bulge: II. kinematical distribution
• Globular Clusters UVIT Legacy Survey (GlobULeS) I. FUV-optical Color-Magnitude Diagrams for Eight Globular Clusters
• The horizontal branch morphology of M31 globular clusters. Extreme second parameter effect in outer halo clusters
• A possible formation channel for blue hook stars in globular cluster - II. Effects of metallicity, mass ratio, tidal enhancement efficiency and helium abundance
• Evidence that Mass Loss on the Red Giant Branch Decreases with Metallicity
• The Orbit of the new Milky Way Globular Cluster FSR1716 = VVV-GC05
• A stellar population synthesis approach to the Oosterhoff dichotomy
• The ages of (the oldest) stars
• The RR Lyrae Delay-Time Distribution: A Novel Perspective on Models of Old Stellar Populations
• Connecting integrated RGB mass loss from asteroseismology and globular clusters
• Selected topics in the evolution of low-mass stars
• The RR Lyrae Variable Population in the Phoenix Dwarf Galaxy
• On the AGB stars of M 4: A robust disagreement between spectroscopic observations and theory
• SHOTGLAS II. MUSE spectroscopy of blue horizontal branch stars in the core of $\omega$ Centauri and NGC 6752
• The Globular Cluster NGC 6402 (M14). II. Variable Stars
• Identification of red high proper-motion objects in Tycho-2 and 2MASS catalogues using Virtual Observatory tools
• Near-infrared observations of RR Lyrae and Type II Cepheid variables in the metal-rich bulge globular cluster NGC 6441
• Spectroscopy of blue horizontal branch stars in NGC 6656 (M22)
• Investigation of the Globular Cluster NGC 2808 with the Ultra-Violet Imaging Telescope
• Chemical evolution of ultra-faint dwarf galaxies: testing the IGIMF
• A new photometric study of M14 (NGC 6402): An interpretation of the Horizontal Branch and beyond
• Stellar-Encounter Driven Red-Giant Star Mass-Loss in Globular Clusters
• Photometry of Variable Stars from THU-NAOC Transient Survey I: The First 2 Years
• The Globular Cluster NGC 6402 (M14). I. A New BV Color-Magnitude Diagram
• Search for stellar spots in field blue horizontal-branch stars
• Synthetic horizontal branch morphology for different metallicities and ages under tidally enhanced stellar wind
• Identifying RR Lyrae in the ZTF DR3 dataset
• Hubble Space Telescope imaging of the extremely metal-poor globular cluster EXT8 in Messier 31
• Period-Color and Amplitude-Color Relations at Maximum and Minimum Light for RR Lyrae Stars in the SDSS Stripe 82 Region
• A Photometric Study of the Outer Halo Globular Cluster NGC 5824
• The ultraviolet colour of globular clusters in M31: a core density effect?
• Structure and evolution of pulsating hot subdwarfs
• A Census of Above-Horizontal-Branch Stars in Galactic Globular Clusters
• RR Lyrae Stars in the Field of Sagittarius II
• Does the Oosterhoff Dichotomy Exist in The Andromeda Galaxy? I. The case of G11
• Many new variable stars discovered in the core of the globular cluster NGC 6715 (M54) with EMCCD observations
• A Magellanic origin for the Virgo substructure
• Hubble Space Telescope FUV observations of M31's globular clusters suggest a spatially homogeneous helium-enriched sub population
• Blazhko type fundamental-mode RR Lyrae stars in the globular cluster, M3
• Humps and bumps: The effects of shocks on the optical light curves of fundamental-mode RR Lyrae stars
• Periods and classifications of RR Lyrae stars in the globular cluster M15
• The Galactic Bulge exploration IV.: RR~Lyrae stars as traces of the Galactic bar -- 3D and 5D analysis, extinction variation
• RR Lyrae stars as probes of the outer Galactic halo: Chemical and kinematic analysis of a pilot sample
• Uncertainties and systematics in stellar evolution models of Red Giant Stars
• Variable Stars and Stellar Populations in Andromeda XXVII: IV. An off-centered, disrupted galaxy
• The temperature distribution of horizontal branch stars: methods and first results
• A Universal Transition in Atmospheric Diffusion for Hot Subdwarfs Near 18,000 K
• Multi-wavelength Photometric Study of RR Lyrae Variables in the Globular Cluster NGC 5272 (Messier 3)
• Variable stars in the globular cluster M28 (NGC 6626)
• Core collapse and horizontal-branch morphology in galactic globular clusters
• Probing the Galactic halo with RR Lyrae stars -- IV. On the Oosterhoff dichotomy of RR Lyrae stars
• Evolution of the Ultraviolet Upturn at $0.3<z<1$: exploring helium rich stellar populations
• Time-Series BVI Photometry for the Globular Cluster NGC 6981 (M72)
• Variable Stars in Large Magellanic Cloud Globular Clusters II: NGC 1786
• SMHASH: A new mid-infrared RR Lyrae distance determination for the Local Group dwarf spheroidal galaxy Sculptor
• Effect of Binary Fraction on Horizontal Branch Morphology under Tidally Enhanced Stellar Wind
• A new visit to the variable stars in M56 and its colour magnitude diagram structure
• The binary fraction of Blue Horizontal-Branch (BHB) Stars
• On the photometric metallicity of Oosterhoff-type I and II RRab stars
• Study of UV bright stellar populations in the globular cluster NGC 1261 using AstroSat
• Discovery of an extended Horizontal Branch in the Large Magellanic Cloud globular cluster NGC1835
• Where are the binaries? -- Searching for blue horizontal-branch stars in binary systems in the inner Galactic Halo
• The Power of Principled Bayesian Methods in the Study of Stellar Evolution
• Omega Centauri: weak MgH-band in red giants directly trace the helium content
• The Ultraviolet Upturn in field Luminous Red Galaxies at $0.3<z<0.7$
• Diffuse LINER-type emission from extended disc regions of barred galaxies
• Period changes in the RR Lyrae stars of NGC 6171 (M107)
• Learning novel representations of variable sources from multi-modal $\text{Gaia}$ data via autoencoders
• Study of UV bright sources in globular cluster NGC 4590 using Ultraviolet Imaging Telescope (UVIT) observations
• A fork in the Sagittarius trailing debris
• Exploring the nature and synchronicity of early cluster formation in the Large Magellanic Cloud: III. Horizontal Branch Morphology
• Variable stars in the VVV globular clusters. II. NGC6441, NGC6569, NGC6626 (M28), NGC6656 (M22), 2MASS-GC02, and Terzan10
• An Extreme Ultra-Compact X-ray Binary in a Globular Cluster: Multi-Wavelength Observations of RZ2109 Explored in a Triple System Framework
• Far Ultra-Violet Insights Into NGC 1399's Globular Cluster Population
• Reconsidering The Bailey Diagrams of ab-type RR Lyrae Stars, Metallicity-Mediated Evolution as the Direct Cause of the Oosterhoff Phenomenon
• Habitable Zones of Host Stars During the Post-MS Phase
• High-cadence stellar variability studies of RR Lyrae stars with DECam: New multi-band templates
• Extraction of Physical Parameters of RRab Variables using Neural Network based Interpolator
• The origin of B-type runaway stars based on kinematics
• RR Lyrae stars with variable mean magnitudes
• Connections between the cycle-to-cycle light curve and O-C variations of the Blazhko RR Lyrae stars
• Matching seismic masses for RR Lyrae-type and oscillating red horizontal-branch stars in M4
• WFPC2 UV survey of Galactic Globular Clusters. The Horizontal Branch temperature distribution
• Statistical analysis of Galactic globular cluster type properties
• Optical and near-infrared pulsation properties of RR Lyrae and Population II Cepheid variables in the Messier 15 globular cluster
• RR Lyrae stars in the newly discovered ultra-faint dwarf galaxy Centaurus I
• Yellow Post-Asymptotic-Giant-Branch Stars as Standard Candles. I. Calibration of the Luminosity Function in Galactic Globular Clusters
• A Multiband Photometric Study of RR Lyrae Stars in M53 (NGC 5024)
• Old stellar systems in UV: resolved and integrated properties