Luis Zapata — Page 2

arXiv2006

Radio Continuum Sources Associated with AB Aur

We present high angular resolution, high-sensitivity Very Large Array observations at 3.6 cm of the Herbig Ae star AB Aur. This star is of interest since its circumstellar disk exhibits characteristics that have been attributed to the presence of an undetected low mass companion or giant gas planet. Our image confirms the continuum emission known to exist in association with the star, and detects a faint protuberance that extends about $0\rlap.{''}3$ to its SE. Previous theoretical considerations and observational results are consistent with the presence of a companion to AB Aur with the separation and position angle derived from our radio data. We also determine the proper motion of AB Aur by comparing our new observations with data taken about 17 years ago and find values consistent with those found by Hipparcos.

astro-ph↗

arXiv2005

In Search of Circumstellar Disks Around Young Massive Stars

We present 7 mm, 1.3 cm and 3.6 cm continuum observations made with the Very Large Array toward a sample of ten luminous IRAS sources that are believed to be regions of massive star formation. We detect compact 7 mm emission in four of these objects: IRAS 18089-1732(1), IRAS 18182-1433, IRAS 18264-1152 and IRAS 18308-0841 and for the first time find that these IRAS sources are associated with double or triple radio sources separated by a few arcseconds. We discuss the characteristics of these sources based mostly on their spectral indices and find that their nature is diverse. Some features indicate that the 7 mm emission is dominated by dust from disks or envelopes. Toward other components the 7 mm emission appears to be dominated by free-free radiation, both from ionized outflows or from optically thick H II regions. Furthermore, there is evidence of synchrotron contamination in some of these sources. Finally, we found that the sources associated with ionized outflows, or thermal jets are correlated with CH$_3$OH masers. The precise determination of the nature of these objects requires additional multifrequency observations at high angular resolution. The 3.6 cm continuum observations also revealed seven UCHII regions in the vicinity of the sources IRAS 18089-1732(1) and two more in the source IRAS 18182-1433. We show that the small photoionized nebulae of these UCHII regions are produced by early B-type stars.

astro-ph↗