# A search for water maser emission from brown dwarfs and low-luminosity young stellar objects

## TL;DR

This study conducted a sensitive survey for water maser emission in low-luminosity young stellar objects, finding limited detections and suggesting that established correlations between maser luminosity and bolometric luminosity may not apply at very low luminosities.

## Contribution

It provides new observational data on water maser emission in objects with L_bol < 1 L_sun, challenging existing correlations and exploring the presence of masers in brown dwarfs and low-luminosity YSOs.

## Key findings

- Detected water maser emission in a nearby YSO, not in the target brown dwarf.
- Upper limits on maser emission are lower than expected from known correlations.
- The correlation between maser and bolometric luminosity may not hold at low luminosities.

## Abstract

We present a survey for water maser emission toward a sample of 44 low-luminosity young objects, comprising (proto-)brown dwarfs, first hydrostatic cores (FHCs), and other young stellar objects (YSOs) with bolometric luminosities lower than 0.4 L$_\odot$. Water maser emission is a good tracer of energetic processes, such as mass-loss and/or accretion, and is a useful tool to study this processes with very high angular resolution. This type of emission has been confirmed in objects with L$_{\rm bol}\ge 1$ L$_\odot$. Objects with lower luminosities also undergo mass-loss and accretion, and thus, are prospective sites of maser emission. Our sensitive single-dish observations provided a single detection when pointing toward the FHC L1448 IRS 2E. However, follow-up interferometric observations showed water maser emission associated with the nearby YSO L1448 IRS 2 { (a Class 0 protostar of L$_{\rm bol}\simeq 3.6-5.3$ L$_\odot$)}, and did not find any emission toward L1448 IRS 2E. The upper limits for water maser emission determined by our observations are one order of magnitude lower than expected from the correlation between water maser luminosities and bolometric luminosities found for YSOs. This suggests that this correlation does not hold at the lower end of the (sub)stellar mass spectrum. Possible reasons are that the slope of this correlation is steeper at L$_{\rm bol}\le 1$ L$_\odot$, or that there is an absolute luminosity threshold below which water maser emission cannot be produced. Alternatively, if the correlation still stands at low luminosity, the detection rates of masers would be significantly lower than the values obtained in higher-luminosity Class 0 protostars.