# On the nature of the compact sources in IRAS 16293-2422 seen in at centimeter to sub-millimeter wavelengths

## TL;DR

This study uses multi-wavelength observations to analyze the nature of compact sources in IRAS 16293-2422, revealing dust-dominated emission, episodic protostellar activity, and early evolutionary stages.

## Contribution

It provides new multi-epoch, multi-wavelength data that clarify the emission mechanisms and evolutionary status of sources A2 and B in IRAS 16293-2422.

## Key findings

- Source A2 is a protostar with episodic mass ejections.
- Source B's emission is dominated by dust across all observed wavelengths.
- Source B shows increasing size with frequency, indicating optical thickness effects.

## Abstract

We present multi-epoch continuum observations of the Class 0 protostellar system IRAS 16293-2422 taken with the Very Large Array (VLA) at multiple wavelengths between 7 mm and 15 cm (41 GHz down to 2 GHz), as well as single-epoch Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations covering the range from 0.4 to 1.3 mm (700 GHz down to 230 GHz). The new VLA observations confirm that source A2 is a protostar driving episodic mass ejections, and reveal the complex relative motion between A2 and A1. The spectrum of component B can be described by a single power law ($S_\nu \propto \nu^{2.28}$) over the entire range from 3 to 700 GHz (10 cm down to 0.4 mm), suggesting that the emission is entirely dominated by dust even at $\lambda$ = 10 cm. Finally, the size of source B appears to increase with frequency up to 41 GHz, remaining roughly constant (at $0''.39$ $\equiv$ 55 AU) at higher frequencies. We interpret this as evidence that source B is a dusty structure of finite size that becomes increasingly optically thick at higher frequencies until, in the millimeter regime, the source becomes entirely optically thick. The lack of excess free-free emission at long wavelengths, combined with the absence of high-velocity molecular emission indicates that source B does not drive a powerful outflow, and might indicate that source B is at a particularly early stage of its evolution.