On the protostellar mass-luminosity relation

TL;DR

This paper investigates the relationship between mass and luminosity in protostars, suggesting most have accretion luminosities close to their photospheric radiation, with some indicating significant ongoing mass accretion.

Contribution

It provides an initial analysis of the protostellar mass-luminosity relation using current dynamical mass estimates and empirical models, highlighting potential bimodal accretion behaviors.

Findings

Most protostars align with the empirical birthline.

Many have accretion luminosities comparable to photospheric radiation.

Some protostars show luminosities indicating ongoing significant mass accretion.

Abstract

We present a preliminary view of the protostellar mass-luminosity relation using current samples of protostars with dynamical mass estimates. To provide a lower limit to the expected luminosities, we adopt an empirical estimate for the intrinsic (without accretion) protostellar luminosity and radius as a function of mass. We find that many of the protostars with current dynamical mass estimates track the empirical mass-luminosity "birthline" reasonably closely, suggesting that their accretion luminosities may be at most comparable to their photospheric radiation. In turn, this implies that mass accretion rates for many objects are well below that required to build up the final stellar mass in typical estimated protostellar lifetimes. A small subset of the protostars have luminosities well above the predicted photospheric values, consistent with evolutionarily-important mass addition. These results hint at a possible bimodal distribution of accretion, but a firm conclusion is not possible given the small size of and likely biases in the current sample.