The Unusual Galactic Center Radio Source N3

TL;DR

This study presents multi-wavelength radio observations of the unusual compact source N3 near the Galactic Center, revealing its non-thermal nature, variability, and possible interaction with a nearby molecular cloud, but its exact nature remains uncertain.

Contribution

The paper provides detailed radio and molecular observations of N3, ruling out common source hypotheses and suggesting a potential micro-blazar nature, which is a novel insight into this enigmatic source.

Findings

N3 is a compact, bright, non-thermal radio source with variability over time.

A nearby molecular cloud shows signs of interaction with N3.

N3 is unlikely to be an HII region, supernova, star, AGN, or micro-quasar, but may be a micro-blazar.

Abstract

Here we report on new, multi-wavelength radio observations of the unusual point source "N3" that appears to be located in the vicinity of the Galactic Center. VLA observations between 2 and 50 GHz reveal that N3 is a compact and bright source (56 mJy at 10 GHz) with a non-thermal spectrum superimposed upon the non-thermal radio filaments (NTFs) of the Radio Arc. Our highest frequency observations place a strict upper limit of 65 x 28 mas on the size of N3. We compare our observations to those of Yusef-Zadeh & Morris (1987) and Lang et al. (1997) and conclude that N3 is variable over long time scales. Additionally, we present the detection of a compact molecular cloud located adjacent to N3 in projection. CH3CN, CH3OH, CS, HC3N, HNCO, SiO, SO, and NH3 are detected in the cloud and most transitions have FWHM line widths of ~20 km/s. The rotational temperature determined from the metastable NH3 transitions ranges from 79 K to 183 K depending on the transitions used. We present evidence that this molecular cloud is interacting with N3. After exploring the relationship between the NTFs, molecular cloud, and N3, we conclude that N3 likely lies within the Galactic Center. We are able to rule out the HII region, young supernova, active star, AGN, and micro-quasar hypotheses for N3. While a micro-blazar may provide a viable explanation for N3, additional observations are needed to determine the physical counterpart of this mysterious source.