Testing Mass Loss in Large Magellanic Cloud Cepheids using Infrared and Optical Observations

TL;DR

This study investigates how mass loss in Large Magellanic Cloud Cepheids influences their infrared Period-Luminosity relations, revealing effects on the relation's slope, zero point, and potential metallicity dependence.

Contribution

It combines infrared and optical data to model mass-loss rates and demonstrates how mass loss impacts the structure and scatter of infrared PL relations in LMC Cepheids.

Findings

Mass-loss rates range from 10^{-12} to 10^{-7} M_sun/yr.

Mass loss affects the slope and zero point of IR PL relations.

Infrared excess due to mass loss is more significant at lower periods.

Abstract

It has been claimed that Period-Luminosity relations derived from infrared observations of Large Magellanic Cloud (LMC) Cepheids are less dependent on the metallicity of the Cepheids. In this work, infrared observations of LMC Cepheids from the SAGE survey are combined with OGLE II optical observation to model and predict mass-loss rates. The mass-loss rates are fit to the data and are predicted to range from about 10^{-12} to 10^{-7}M_\odot/yr; however, the rates depend on the assumed value of the dust-to-gas ratio. By comparing the relations derived from observations to the relations derived from predicted infrared stellar luminosities from the mass-loss model, it is shown mass loss affects the structure and scatter of the infrared Period-Luminosity relation. Mass loss produces shallower slopes of the infrared relations and a lower zero point. There is also evidence for non-linearity in the predicted Period-Luminosity relations, and it is argued that mass loss produces larger infrared excess at lower periods, which affects the slope and zero point, making the PL relations more linear in the wavelength range of 3.6 to 5.8 micron. Because the dust-to-gas ratio is metallicity dependent and mass loss may have a metallicity dependence, infrared Period-Luminosity relations have additional uncertainty due to metallicity.