Kavli Affiliate: David A. Principe
| First 5 Authors: Gregory J. Herczeg, Yuguang Chen, Jean-Francois Donati, Andrea K. Dupree, Frederick M. Walter
| Summary:
Accretion plays a central role in the physics that governs the evolution and
dispersal of protoplanetary disks. The primary goal of this paper is to analyze
the stability over time of the mass accretion rate onto TW Hya, the nearest
accreting solar-mass young star. We measure veiling across the optical spectrum
in 1169 archival high-resolution spectra of TW Hya, obtained from 1998–2022.
The veiling is then converted to accretion rate using 26 flux-calibrated
spectra that cover the Balmer jump. The accretion rate measured from the excess
continuum has an average of $2.51times10^{-9}$~M$_odot$~yr$^{-1}$ and a
Gaussian distribution with a FWHM of 0.22 dex. This accretion rate may be
underestimated by a factor of up to 1.5 because of uncertainty in the
bolometric correction and another factor of 1.7 because of excluding the
fraction of accretion energy that escapes in lines, especially Ly$alpha$. The
accretion luminosities are well correlated with He line luminosities but poorly
correlated with H$alpha$ and H$beta$ luminosity. The accretion rate is always
flickering over hours but on longer timescales has been stable over 25 years.
This level of variability is consistent with previous measurements for most,
but not all, accreting young stars.
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