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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>
Inner Warm Disk of ESO H<i>α</i>279a Revealed by NA i and CO Overtone Emission Lines
Lyo, A-Ran,Kim, Jongsoo,Lee, Jae-Joon,Kim, Kyoung-Hee,Kang, Jihyun,Byun, Do-Young,Mace, Gregory,Sokal, Kimberly R.,Park, Chan,Chun, Moo-Young,Oh, Heeyoung,Yu, Young Sam,Oh, Jae Sok,Jeong, Ueejeong,Kim American Astronomical Society 2017 The Astrophysical Journal Vol.844 No.1
<P>We present an analysis of near-infrared, high-resolution spectroscopy toward the flat-spectrum young stellar object (YSO) ESO H alpha 279a (similar to 1.5M(circle dot)) in the Serpens star-forming region at a distance of 429 pc. Using the Immersion GRating INfrared Spectrometer (IGRINS; R approximate to 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, H-2, 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 and 1.00 au, while the CO overtone emission lines are from the outer part of the disk, in the range between 0.22 and 3.00 au. The model 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 2-10 x 10-7 Me yr(-1). from the measured Br gamma emission luminosity of 1.78(+/- 0.31) x 10(31) erg s(-1).</P>
Kaplan, Kyle F.,Dinerstein, Harriet L.,Oh, Heeyoung,Mace, Gregory N.,Kim, Hwihyun,Sokal, Kimberly R.,Pavel, Michael D.,Lee, Sungho,Pak, Soojong,Park, Chan,Oh, Jae Sok,Jaffe, Daniel T. American Astronomical Society 2017 The Astrophysical journal Vol.838 No.2
<P>We present a deep near-infrared spectrum of the Orion Bar Photodissociation Region (PDR) taken with the Immersion Grating INfrared Spectrometer (IGRINS) on the 2.7 m telescope at the McDonald Observatory. IGRINS has high spectral resolution (R similar to 45,000) and instantaneous broad wavelength coverage (1.45-2.45 mu m), enabling us to detect 87 emission lines from rovibrationally excited molecular hydrogen (H-2) that arise from transitions out of 69 upper rovibration levels of the electronic ground state. These levels cover a large range of rotational and vibrational quantum numbers and excitation energies, making them excellent probes of the excitation mechanisms of H2 and physical conditions within the PDR. The Orion Bar PDR is thought to consist of cooler high density clumps or filaments (T = 50-250 K, n(H) = 10(5)-10(7) cm(-3)) embedded in a warmer lower density medium (T = 250-1000 K, n(H) = 10(4)-10(5) cm(-3)). We fit a grid of constant temperature and density Cloudy models, which recreate the observed H2 level populations well, to constrain the temperature to a range of 600-650. K and the density to n(H) = 2.5 x 10(3) -10(4) cm(-3). The best-fit model gives T = 625 K and n(H) = 5 x 10(3) cm(-3). This well-constrained warm temperature is consistent with kinetic temperatures found by other studies for the Orion Bar's lower density medium. However, the range of densities well fit by the model grid is marginally lower than those reported by other studies. We could be observing lower density gas than the surrounding medium, or perhaps a density-sensitive parameter in our models is not properly estimated.</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>