Identifying and characterising the population of hot sub-luminous stars with multi-colour MeerLICHT data

Abstract

Colour-magnitude diagrams reveal a population of blue (hot) sub-luminous objects with respect to the main sequence. These hot sub-luminous stars are the result of evolutionary processes that require stars to expel their obscuring, hydrogen-rich envelopes to reveal the hot helium core. As such, these objects offer a direct window into the hearts of stars that are otherwise inaccessible to direct observation. We showcase MeerLICHT's capabilities of detecting faint hot subdwarfs and identifying the dominant frequency in the photometric variability of these compact hot stars, in comparison to their $Gaia$ DR3 data. We hunt for oscillations, which will be an essential ingredient for accurately probing stellar interiors in future asteroseismology. Comparative MeerLICHT and $Gaia$ colour-magnitude diagrams are presented as a way to select hot subdwarfs from our sample. A dedicated frequency determination technique is developed and applied to the selected candidates to determine their dominant variability using time-series data from MeerLICHT and $Gaia$ DR3. We explore the power of both datasets in determining the dominant frequency. Using the $g-i$ colour, MeerLICHT offers a colour-magnitude diagram that is comparable in quality to that of $Gaia$ DR3. The MeerLICHT colour-colour diagrams allow for the study of different stellar populations. The frequency analysis of MeerLICHT and $Gaia$ DR3 data demonstrates the superiority of our MeerLICHT multi-colour photometry in estimating the dominant frequency compared to the sparse $Gaia$ DR3 data. MeerLICHT's multi-band photometry leads to the discovery of high-frequency faint subdwarfs. Our MeerLICHT results are a proof-of-concept of the capacity of the BlackGEM instrument currently in the commissioning stage at ESO's La Silla Observatory in Chile.

Accepted from A&A journal. Publication is still in process

References in corpus (33)

• The Gaia mission
• The Transiting Exoplanet Survey Satellite
• Gaia Early Data Release 3: Parallax bias versus magnitude, colour, and position
• A binary model for the UV-upturn of elliptical galaxies (MNRAS version)
• Gaia Data Release 3. Summary of the variability processing and analysis
• Estimating distances from parallaxes. III. Distances of two million stars in the Gaia DR1 catalogue
• A classifier for spurious astrometric solutions in Gaia EDR3
• The Detection and Characterization of Be+sdO Binaries from HST/STIS FUV Spectroscopy
• Population of hot subdwarf stars studied with Gaia III. Catalogue of known hot subdwarf stars: Data Release 2
• The population of hot subdwarf stars studied with Gaia -- IV. Catalogues of hot subluminous stars based on Gaia EDR3
• The orbits of subdwarf-B + main-sequence binaries: III. The period - eccentricity distribution
• delta Ceti is not monoperiodic: seismic modeling of a beta Cephei star from MOST spacebased photometry
• Gaia Data Release 3: Pulsations in main sequence OBAF-type stars
• Asteroseismology revealing trapped modes in KIC 10553698A
• Observed binary populations reflect the Galactic history. Explaining the orbital period-mass ratio relation in wide hot subdwarf binaries
• Velocity monitoring of gamma-Cas stars reveals their binarity status
• Year 1 of the ZTF high-cadence Galactic Plane Survey: Strategy, goals, and early results on new single-mode hot subdwarf B-star pulsators
• An evolutionary study of the pulsating subdwarf B eclipsing binary PG1336-018 (NY Vir)
• Detection of nonlinear resonances among gravity modes of slowly pulsating B stars: results from five iterative prewhitening strategies
• Radial velocity variability and evolution of hot subdwarf stars
• Interferometric detections of sdO companions orbiting three classical Be stars
• Stars stripped in binaries -- the living gravitational wave sources
• The OmegaWhite survey for short-period variable stars - V. Discovery of an ultracompact hot subdwarf binary with a compact companion in a 44 minute orbit
• The ZTF Source Classification Project: II. Periodicity and variability processing metrics
• A Hybrid Algorithm for Period Analysis from Multi-band Data with Sparse and Irregular Sampling for Arbitrary Light Curve Shapes
• Asteroseismic analysis of variable hot subdwarf stars observed with TESS I. The mean g-mode period spacings in hot subdwarf B stars
• Birth of a Be star: an APOGEE search for Be stars forming through binary mass transfer
• The effects of near-core convective shells on the gravity modes of the subdwarf B pulsator KIC 10553698A
• New Variable Hot Subdwarf Stars Identified from Anomalous Gaia Flux Errors, Observed by TESS, and Classified via Fourier Diagnostics
• A search for variable subdwarf B stars in TESS Full Frame Images II. Variable objects in the northern ecliptic hemisphere
• Color and Variability Characteristics of Point Sources in the Faint Sky Variability Survey
• Short timescale variability in the Faint Sky Variability Survey
• Pulsating subdwarf B stars observed with K2 during Campaign 7 and an examination of seismic group-properties

Cited by in corpus (3)

• The BlackGEM telescope array I: Overview
• Unsupervised learning for variability detection with Gaia DR3 photometry. The main sequence-white dwarf valley
• FINKER: Frequency Identification through Nonparametric KErnel Regression in astronomical time series