The Spectroscopy of Protostars with IGRINS – Characterizing Protostellar Accretion Using Br γ Emission
ORAL
Abstract
Through the University of Toledo’s NSF-REU program, this research aims to determine intrinsic stellar parameters and characterize accretion activity in protostars using Brackett-γ (Br γ) emission. High-resolution near-infrared spectra were obtained with the Immersion GRating INfrared Spectrograph (IGRINS), and data reduction was performed using the IGRINS Pipeline Package (PLP) v3.1.
Our analysis focuses on the K-band spectral range (2.08–2.35 μm), excluding low-SNR regions in the H-band and near the band edges. To derive fundamental stellar parameters including effective temperature (Teff), surface gravity (log g), rotational velocity (v sin i), radial velocity (vr), and K-band veiling (rk) we fit observed spectra with synthetic models from the BT-Settl (CIFIST) library of precomputed stellar atmospheres.
Spectral fitting is conducted using a Markov Chain Monte Carlo (MCMC) method via the emcee package, enabling us to explore the probability distributions of stellar parameters and quantify associated uncertainties. In parallel, we analyze the Br γ emission line at 2.166 μm to investigate protostellar accretion. The line profile and luminosity are used to infer accretion properties, using the observed correlation between Br γ and accretion luminosity (Alcalá et al. 2017). This approach enables simultaneous characterization of both stellar and accretion properties, crucial for understanding early stellar evolution and disk accretion.
Our analysis focuses on the K-band spectral range (2.08–2.35 μm), excluding low-SNR regions in the H-band and near the band edges. To derive fundamental stellar parameters including effective temperature (Teff), surface gravity (log g), rotational velocity (v sin i), radial velocity (vr), and K-band veiling (rk) we fit observed spectra with synthetic models from the BT-Settl (CIFIST) library of precomputed stellar atmospheres.
Spectral fitting is conducted using a Markov Chain Monte Carlo (MCMC) method via the emcee package, enabling us to explore the probability distributions of stellar parameters and quantify associated uncertainties. In parallel, we analyze the Br γ emission line at 2.166 μm to investigate protostellar accretion. The line profile and luminosity are used to infer accretion properties, using the observed correlation between Br γ and accretion luminosity (Alcalá et al. 2017). This approach enables simultaneous characterization of both stellar and accretion properties, crucial for understanding early stellar evolution and disk accretion.
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Presenters
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Zachary T Lao
Youngstown State University
Authors
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Zachary T Lao
Youngstown State University