Adventures of the Orion Radio All-Stars: intense radio outbursts, X-ray megaflares, and a novel VLBI search for ensuing coronal mass ejections
The sensitivity upgrades of both the NRAO Very Large Array (VLA) and the Very Long Baseline Array (VLBA) have begun to provide us with a much improved perspective on stellar centimeter radio emission, particularly concerning young stellar objects (YSOs), in ideal preparation for ngVLA and SKA science. For the first time we now have systematic access to the cm-radio time domain on short timescales and the possibility to disentangle thermal and nonthermal emission. I will mainly present an update on the Orion Radio All-Stars, an ongoing project targeting the star-forming Orion Nebula Cluster (ONC) with the VLA, VLBA, and ALMA, including a radio perspective of the Orion explosion and John's related work. I will first present the increasingly well-characterized ONC radio sample, including first constraints on YSO radio flares and their relation with X-ray flares, as well as on the resulting high-energy irradiation of their surroundings. I will then focus on a VLBA non-thermal variability survey of all identified VLA targets in Orion in the largest such survey of YSO emission to date, enabled by software correlation - currently in a coordinated joint VLBA-Chandra large program to look for radio emission from coronal mass ejections following X-ray megaflares. Other than providing a nonthermal census, I will additionally discuss the use of the VLBA for precision stellar astrometry in the Gaia era. I will conclude with a complementary look at variable YSO millimeter continuum emission in the ONC, targeting synchrotron flares in this new window on high-energy processes in YSOs, using ALMA.
