Inner warm disk of ESO H$\alpha$ 279A revealed by NA I and CO overtone emission lines

TL;DR

This study uses high-resolution near-infrared spectroscopy to analyze the inner disk and accretion processes of the young stellar object ESO Hα 279A, revealing detailed disk structure and accretion rates.

Contribution

It provides the first detailed modeling of the inner disk regions of ESO Hα 279A using multiple emission lines, demonstrating the utility of Na I and CO overtone lines as tracers.

Findings

Na I emission traces the innermost disk region (0.04-1.00 AU).

CO overtone emission originates from the outer disk (0.22-3.00 AU).

Mass accretion rate estimated at 2-10x10^{-7} M_solar/yr.

Abstract

We present analysis of near-infrared, high-resolution spectroscopy towards the Flat-spectrum YSO (Young Stellar Object) ESO H$\alpha$ 279a (1.5 solar mass) in the Serpens star forming region, at the distance of 429 pc. Using the Immersion GRating INfrared Spectrometer (IGRINS, R=45,000), we detect emission lines originating from the accretion channel flow, jet, and inner disk. Specifically, we identify hydrogen Brackett series recombination, [Fe II], [Fe III], [Fe IV], Ca I, Na I, H2, H2O and CO overtone emission lines. By modeling five bands of CO overtone emission lines, and the symmetric double-peaked line profile for Na I emission lines, we find that ESO H$\alpha$ 279a has an actively accreting Keplerian disk. From our Keplerian disk model, we find that Na I emission lines originate between 0.04 AU and 1.00 AU, while CO overtone emission lines are from the outer part of disk, in the range between 0.22 AU and 3.00 AU. It reveals that the neutral atomic Na gas is a good tracer of the innermost region of the actively accreting disk. We derive a mass accretion rate of 2-10x10^{-7} M_solar/yr from the measured Br_gamma emission luminosity of 1.78(+-0.31)x10^{31} erg/s.