Testing the Potential for Radio Variability in Disks around T Tauri Stars with Observations and Chemical Modeling.

A multiwavelength observing campaign of the T Tauri star (TTS) GM Aur was undertaken in 2019 December. This campaign obtained Swift X-ray and NUV fluxes, HST NUV spectra, LCOGT and TESS photometry, CHIRON Hα spectra, Atacama Large Millimeter/submillimeter Array (ALMA) ¹³CO and C¹⁸O line fluxes, and Very Large Array (VLA) 3 cm continuum fluxes taken contemporaneously over one month. The X-ray to optical observations were presented previously. Here we present the ALMA and VLA data and make comparisons to GM Aur's accretion and X-ray properties. We report no variability in the observed millimeter CO emission. Using disk chemistry models, we show that the magnitude of the changes seen in the FUV luminosity of GM Aur could lead to a variation of up to ∼6% in CO line emission and changes in the X-ray luminosity could lead to larger changes of ∼25%. However, the FUV and X-ray luminosity increases must last at least 100 years in order to induce changes, which seems implausible in the TTS stage; also, these changes would be too small to be detectable by ALMA. We report no variability in the 3 cm emission observed by the VLA, showing that changes of less than a factor of ∼3 in the accretion rates of TTSs do not lead to detectable changes in the mass-loss rate traced by the jet at centimeter wavelengths. We conclude that changes typically seen in the FUV and X-ray luminosities of TTSs do not lead to observable changes in millimeter CO line emission or jet centimeter continuum emission. [ABSTRACT FROM AUTHOR]