Constraining variable accretion in deeply embedded protostars with interferometric observations




Francis, Logan

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Variability of pre-main-sequence stars observed at optical wavelengths has been attributed to fluctuations in the mass accretion rate from the circumstellar disk onto the forming star. Detailed models of accretion disks suggest that young deeply em- bedded protostars should also exhibit variations in their accretion rates, and that these changes can be tracked indirectly by monitoring the response of the dust enve- lope at mid-IR to millimeter wavelengths. Interferometers such as ALMA offer the resolution and sensitivity to observe small fluctuations in brightness at the scale of the disk where episodic accretion may be driven. In this thesis, novel methods for comparing interferometric observations are presented and applied to CARMA and ALMA 1.3mm observations of deeply embedded protostars in Serpens taken 9 years apart. No brightness variation is found above the limits of the analysis of a factor of ~>50%, due to the limited sensitivity of the CARMA observations and small number of sources common to both epochs. It is further shown that follow up ALMA observa- tions with a similar sample size and sensitivity may be able to uncover variability at the level of a few percent, and the implications of this for future work are discussed.



star formation, interferometry, variable stars, protostars, accretion