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Sokal, Kimberly R.,Deen, Casey P.,Mace, Gregory N.,Lee, Jae-Joon,Oh, Heeyoung,Kim, Hwihyun,Kidder, Benjamin T.,Jaffe, Daniel T. American Astronomical Society 2018 The Astrophysical journal Vol.853 No.2
<P>At 60 pc, TW Hydra (TW Hya) is the closest example of a star with a gas-rich protoplanetary disk, though TW Hya may be relatively old (3-15 Myr). As such, TW Hya is especially appealing for testing our understanding of the interplay between stellar and disk evolution. We present a high-resolution near-infrared spectrum of TW Hya obtained with the Immersion GRating INfrared Spectrometer (IGRINS) to re-evaluate the stellar parameters of TW Hya. We compare these data to synthetic spectra of magnetic stars produced by MoogStokes, and use sensitive spectral line profiles to probe the effective temperature, surface gravity, and magnetic field. A model with T-eff = 3800 K, log g = 4.2, and B = 3.0 kG best fits the near-infrared spectrum of TW Hya. These results correspond to a spectral type of M0.5 and an age of 8 Myr, which is well past the median life of gaseous disks.</P>
The Spectrum of SS 433 in the<i>H</i>and<i>K</i>Bands
Robinson, Edward L.,Froning, Cynthia S.,Jaffe, Daniel T.,Kaplan, Kyle F.,Kim, Hwihyun,Mace, Gregory N.,Sokal, Kimberly R.,Lee, Jae-Joon American Astronomical Society 2017 The Astrophysical journal Vol.841 No.2
<P>SS 433 is an X-ray binary and the source of sub-relativistic, precessing, baryonic jets. We present high-resolution spectrograms of SS. 433 in the infrared H and K bands. The spectrum is dominated by hydrogen and helium emission lines. The precession phase of the emission lines from the jet continues to be described by a constant period, P-jet = 162.375 days. The limit on any secularly changing period is |P| less than or similar to 10(-5). The He I lambda 2.0587 mu m line has complex and variable P-Cygni absorption features produced by an inhomogeneous wind with a maximum outflow velocity near 900 km s(-1). The He II emission lines in the spectrum also arise in this wind. The higher members of the hydrogen Brackett lines show a double-peaked profile with symmetric wings extending more than +/- 1500 km s(-1) from the line center. The lines display radial velocity variations in phase with the radial velocity variation expected of the compact star, and they show a distortion during disk eclipse that we interpret as a rotational distortion. We fit the line profiles with a model in which the emission comes from the surface of a symmetric, Keplerian accretion disk around the compact object. The outer edge of the disk has velocities that vary from 110 to 190 km s(-1). These comparatively low velocities place an important constraint on the mass of the compact star: its mass must be less than 2.2 M-circle dot and is probably less than 1.6 M-circle dot</P>