Unveiling the First O-Type Bloated Star Candidate through ALMA and EVLA Observations

TL;DR

This study uses ALMA and EVLA observations to identify and analyze the environment of a candidate O-type bloated star, revealing a dense core, molecular outflows, a hot core, and a Keplerian disk, advancing understanding of massive star formation.

Contribution

First high-resolution multi-wavelength observations of a candidate O-type bloated star, uncovering its dense core, outflows, and disk structure, providing new insights into massive star evolution.

Findings

Detection of a dense core coincident with the optical source.

Identification of bipolar molecular outflows.

Evidence of a Keplerian disk around the star.

Abstract

We investigate the circumstellar environment of the O-type bloated star candidate IRAS 19520+2759 (I19520) using high-resolution observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and the Expanded Very Large Array (EVLA). Radio continuum emission traced by the EVLA (C, K, and Q bands) exhibits a spectral index of 0.5, consistent with a thermal jet. ALMA 1.3 mm continuum map reveals a compact source coincident with the optical counterpart of I19520, likely tracing the dense core hosting the central massive young stellar object. A prominent molecular outflow in the east-west direction, along with a possible secondary outflow oriented northeast-southwest, is identified in the $^{13}\mathrm{CO}$ emission. A hot molecular core and a Keplerian disk are detected in several $\mathrm{SO}_2$ transitions. Assuming an edge-on disk geometry, the dynamical mass of the central object is estimated to be in the range of $10$-$15~M_\odot$.