Study of instabilities and outbursts in luminous blue variables AF And $\&$ R 127

TL;DR

This study investigates the instabilities in luminous blue variables AF And and R 127 through linear stability analysis, revealing multiple unstable modes that may explain their irregular variability and eruptions.

Contribution

It provides the first detailed linear stability analysis of LBVs during quiescent and outburst phases, identifying unstable modes linked to observed variability.

Findings

Multiple unstable modes found in LBV models.

Mode interactions are frequent in the models.

Instabilities increase at temperatures below 15000 K.

Abstract

Luminous blue variables (LBVs) are evolved massive stars close to the Eddington limit, with a distinct spectroscopic and photometric variability having unsteady mass-loss rates. These stars show a considerable change in their surface temperature from quiescent to outbursts phase. The cause of irregular variability and unsteady mass-loss rate is not properly understood. Here we present the result of linear stability analysis in two LBVs AF And and R 127 during their quiescent and outburst phase. We note that several modes are unstable in the models of the considered LBVs. Mode interaction is frequent in the modal diagrams for the models of both LBVs. For AF And, number of instabilities increase in models having temperature below 15000 K. The found instabilities may be linked with the observed irregular variabilities and surface eruptions. Observational facilities of Belgo-Indian Network for Astronomy and Astrophysics (BINA) will be very beneficial to study the spectroscopic and photometric behavior of the considered LBVs.