Mira variables in the Milky Way's nuclear stellar disc: discovery and classification

Abstract

The properties of the Milky Way's nuclear stellar disc give crucial information on the epoch of bar formation. Mira variables are promising bright candidates to study the nuclear stellar disc, and through their period-age relation dissect its star formation history. We report on a sample of $1782$ Mira variable candidates across the central $3\times 3{\mathrm{deg}}^2$ of the Galaxy using the multi-epoch infrared VISTA Variables in Via Lactea (VVV) survey. We describe the algorithms employed to select candidate variable stars and then model their light curves using periodogram and Gaussian process methods. By combining with WISE, 2MASS and other archival photometry, we model the multi-band light curves to refine the periods and inspect the amplitude variation between different photometric bands. The infrared brightness of the Mira variables means many are too bright and missed by VVV. However, our sample follows a well-defined selection function as expected from artificial star tests. The multi-band photometry is modelled using stellar models with circumstellar dust that characterise the mass loss rates. We demonstrate how $\gtrsim 90$ per cent of our sample is consistent with O-rich chemistry. Comparison to period-luminosity relations demonstrates that the bulk of the short period stars are situated at the Galactic Centre distance. Many of the longer period variables are very dusty, falling significantly under the O-rich Magellanic Cloud and solar neighbourhood period-luminosity relations and exhibit high mass-loss rates of $\sim 2.5\times 10^{-5}{M}_{\odot }{\mathrm{yr}}^{-1}$. The period distribution appears consistent with the nuclear stellar disc forming $\gtrsim 8\mathrm{Gyr}$ ago although it is not possible to disentangle the relative contributions of the nuclear stellar disc and the contaminating bulge.

Accepted for publication in MNRAS, 25 pages, 21 figures

References in corpus (41)

• The NumPy array: a structure for efficient numerical computation
• The Gaia mission
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• The Optical to Mid-Infrared Extinction Law Based on the APOGEE, Gaia DR2, Pan-STARRS1, SDSS, APASS, 2MASS and WISE Surveys
• The Visible and Infrared Survey Telescope for Astronomy (VISTA): Design, Technical Overview and Performance
• Improved GRAVITY astrometric accuracy from modeling of optical aberrations
• The wind speeds, dust content, and mass-loss rates of evolved AGB and RSG stars at varying metallicity
• VIRAC: The VVV Infrared Astrometric Catalogue
• The VISTA ZYJHKs Photometric System: Calibration from 2MASS
• A 24 Micron Point Source Catalog of the Galactic Plane from Spitzer/MIPSGAL
• The nuclear cluster of the Milky Way: Our primary testbed for the interaction of a dense star cluster with a massive black hole
• The pulsation modes, masses and evolution of luminous red giants
• Point Sources from a Spitzer IRAC Survey of the Galactic Center
• Luminosities and mass-loss rates of Local Group AGB stars and Red Supergiants
• The meaning of WISE colours - I. The Galaxy and its satellites
• New constraints on the structure of the nuclear stellar cluster of the Milky Way from star counts and MIR imaging
• Mapping the Galactic disk with the LAMOST and Gaia Red clump sample: I: precise distances, masses, ages and 3D velocities of $\sim$ 140000 red clump stars
• Age Demographics of the Milky Way Disk and Bulge
• A Fast Chi-squared Technique For Period Search of Irregularly Sampled Data
• Carbon-Rich Mira Variables: Kinematics and Absolute Magnitudes
• Transverse kinematics of the Galactic bar-bulge from VVV and Gaia
• Exploring the stellar age distribution of the Milky Way Bulge using APOGEE
• Large Magellanic Cloud Near-Infrared Synoptic Survey. V. Period-Luminosity Relations of Miras
• Discovery of RR Lyrae Stars in the Nuclear Bulge of the Milky Way
• The Clouds are breaking: tracing the Magellanic system with Gaia DR1 Mira variables
• An Infrared Census Of Dust In Nearby Galaxies With Spitzer (DUSTiNGS): V. The Period-luminosity Relation For Dusty Metal-Poor AGB Stars
• The LMC's Top 250: Classification of the Most Luminous Compact 8 micron Sources in the Large Magellanic Cloud
• Kinematics of classical Cepheids in the Nuclear Stellar Disk
• Analysis of physical processes in eruptive YSOs with near infrared spectra and multi-wavelength light curves
• The M33 Synoptic Stellar Survey. II. Mira Variables
• Absence of an X-shaped Structure in the Milky Way Bulge Using Mira Variable Stars
• Discovery of carbon-rich Miras in the Galactic bulge
• The period-age relation of long-period variables
• Period estimation for sparsely-sampled quasi-periodic light curves applied to Miras
• Large amplitude periodic outbursts and long period variables in the VVV VIRAC2-$\beta$ database
• New type II Cepheids from VVV data towards the Galactic center
• Carbon stars with increased oxygen and nitrogen abundances: hydrostatic dust-free model atmospheres
• The VVV survey: Long-period variable stars I. Photometric catalog of ten VVV/OGLE tiles
• Luminous AGB variables in the dwarf Irregular Galaxy, NGC 3109
• Characterizing AGB stars in Wide-field Infrared Survey Explorer (WISE) bands
• Difference of photometric properties between regular and non-regular Miras in the Magellanic Clouds

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• The VISTA Variables in the Vía Láctea eXtended (VVVX) ESO public survey: Completion of the observations and legacy
• The period--luminosity relation for Mira variables in the Milky Way using Gaia DR3: a further distance anchor for $H_0$
• Hunting for C-rich long-period variable stars in the Milky Way's bar-bulge using unsupervised classification of Gaia BP/RP spectra
• VIRAC2: NIR Astrometry and Time Series Photometry for 500M+ Stars from the VVV and VVVX Surveys
• The formation history of our Galaxy's nuclear stellar disc constrained from HST observations of the Quintuplet field
• Disc galaxies are still settling: The discovery of the smallest nuclear discs and their young stellar bars
• The Prime Focus Infrared Microlensing Experiment (PRIME): First Results
• Self-Excited Pulsations and the Instability Strip of Long-Period Variables: the Transition from Small-Amplitude Red Giants to Semi-Regular Variables
• Unveiling VVV/WISE Mira variables on the far side of the Galactic disk: Distances, kinematics and a new extinction law
• Metallicity-dependent kinematics and orbits in the Milky Way's nuclear stellar disc