Episodic excursions of low-mass protostars on the Hertzsprung-Russell diagram

Abstract

Following our recent work devoted to the effect of accretion on the pre-main-sequence evolution of low-mass stars, we perform a detailed analysis of episodic excursions of low-mass protostars in the Hertzsprung-Russell (H-R) diagram triggered by strong mass accretion bursts typical of FU Orionis-type objects (FUors). These excursions reveal themselves as sharp increases in the stellar total luminosity and/or effective temperature of the protostar and can last from hundreds to a few thousands of years, depending on the burst strength and characteristics of the protostar. During the excursions, low-mass protostars occupy the same part of the H-R diagram as young intermediate-mass protostars in the quiescent phase of accretion. Moreover, the time spent by low-mass protostars in these regions is on average a factor of several longer than that spent by the intermediate-mass stars in quiescence. During the excursions, low-mass protostars pass close to the position of most known FUors in the H-R diagram, but owing to intrinsic ambiguity the model stellar evolutionary tracks are unreliable in determining the FUor properties. We find that the photospheric luminosity in the outburst state may dominate the accretion luminosity already after a few years after the onset of the outburst, meaning that the mass accretion rates of known FUors inferred from the bolometric luminosity may be systematically overestimated, especially in the fading phase.

15 pages, 12 figures

References in corpus (10)

• Variable protostellar accretion with episodic bursts
• The Hot Inner Disk of FU Ori
• On the existence of accretion-driven bursts in massive star formation
• Episodic accretion: the interplay of infall and disc instabilities
• Forming spectroscopic massive proto-binaries by disk fragmentation
• Formation of primordial supermassive stars by burst accretion
• Self-consistent evolution of accreting low-mass stars and brown dwarfs
• Long-wavelength excesses of FU Orionis objects: flared outer disks or infalling envelopes?
• Explaining the luminosity spread in young clusters: proto and pre-main sequence stellar evolution in a molecular cloud environment
• The effect of accretion on the pre-main-sequence evolution of low-mass stars and brown dwarfs

Cited by in corpus (5)

• Accretion bursts in magnetized gas-dust protoplanetary disks
• Evolution of dust in protoplanetary disks of eruptive stars
• Stellar models and isochrones from low-mass to massive stars including pre-main sequence phase with accretion
• Parameter study for the burst mode of accretion in massive star formation
• Pulsational instability of pre-main sequence models from accreting protostars. I. Constraining the input physics for accretion with spectroscopic parameters and stellar pulsations