Inner disc rearrangement revealed by dramatic brightness variations in the young star PV Cep

TL;DR

This study of PV Cep reveals that dramatic brightness variations are caused by inner disc restructuring driven by fluctuating accretion rates and dust condensation, providing insights into star-disc interactions during early stellar evolution.

Contribution

It presents a multi-wavelength, multi-epoch analysis linking accretion variability and inner disc changes in a young star, highlighting the physical mechanisms behind observed brightness variations.

Findings

PV Cep experienced a 4 mag fading in the I_C-band.

Brightness decline was caused by variable accretion and increased circumstellar extinction.

Inner disc restructuring was triggered by changes in accretion rate and dust condensation.

Abstract

Young Sun-like stars at the beginning of the pre-main sequence (PMS) evolution are surrounded by accretion discs and remnant protostellar envelopes. Photometric and spectroscopic variations of these stars are driven by interactions of the star with the disc. Time scales and wavelength dependence of the variability carry information on the physical mechanisms behind these interactions. We conducted multi-epoch, multi-wavelength study of PV Cep, a strongly variable, accreting PMS star. By combining our own observations from 2004-2010 with archival and literature data, we show that PV Cep started a spectacular fading in 2005, reaching an I_C-band amplitude of 4 mag. Analysis of variation of the optical and infrared fluxes, colour indices, and emission line fluxes suggests that the photometric decline in 2005-2009 resulted from an interplay between variable accretion and circumstellar extinction: since the central luminosity of the system is dominated by accretion, a modest drop in the accretion rate could induce the drastic restructuring of the inner disc. Dust condensation in the inner disc region might have resulted in the enhancement of the circumstellar extinction.