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Measuring the Physical Parameters of TW Hydra
  • +3
  • Casey Deen,
  • Kimberly Sokal,
  • Jacob McLane,
  • btkidder,
  • gmace,
  • dtj
Casey Deen
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Kimberly Sokal
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Jacob McLane
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University of Texas at Austin
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Magnetic fields are ubiquitous features of theories of low mass star formation. Strong fields are important ingredients of the internal structures of young stellar objects, and are required to regulate angular momentum and transport material in circumstellar disks. Indeed, for the few young objects for which measurement of the magnetic field has been possible, fields of 1-4 kiloGauss are common. However, for observing campaigns of large numbers of young stellar objects which magnetic field measurements are not feasible (i.e. low resolution spectra or photometric observations), the effects of the magnetic fields on the derived stellar properties are neglected. If strong magnetic fields affect the observable properties of the young stellar objects in these studies, they can introduce significant biases to the study of young stellar objects. One ominous hint of the dragons lurking in the darkness of our ignorance is the case of TW Hydra, an infamous problem child in the star and planet formation literature. Using optical data, TW Hydra appears to be a K7 YSO with a surprisingly long-lived ( 10 Myr) circumstellar disk, in which a proto-planet may or may not be forming. However, other authors have obtained different seemingly convincing ages/masses using infrared data on the same object. Help is on the horizon, however. A new generation of high resolution infrared spectrographs combined with a spectral synthesis code capable of generating the emergent spectra of magnetic stars promises to help resolve contradictions and reduce uncertainties. IGRINS is one of these new infrared spectrographs, and MoogStokes is one of these spectral synthesis codes. With a resolving power of 40,000, IGRINS covers all of the H and K bands in a single exposure, and contains no moving parts. MoogStokes is a modification of the MOOG spectral synthesis code which permits calculations of emergent spectra of a star with a magnetic atmosphere. In this paper, we use MoogStokes to analyze IGRINS spectra of TW Hydra and attempt to resolve the seeming paradox of the appearance of its optical and infrared spectra..