A5007845160- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Solar and Space Plasma Dynamics
- Astronomy and Astrophysical Research
- Particle physics theoretical and experimental studies
- Molecular Spectroscopy and Structure
- High-Energy Particle Collisions Research
- Quantum Chromodynamics and Particle Interactions
- Atmospheric Ozone and Climate
- Neutrino Physics Research
- Geophysics and Gravity Measurements
- Dark Matter and Cosmic Phenomena
- Particle accelerators and beam dynamics
- Astronomical Observations and Instrumentation
- Astrophysics and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Galaxies: Formation, Evolution, Phenomena
- Spacecraft and Cryogenic Technologies
- Astrophysical Phenomena and Observations
- Calibration and Measurement Techniques
- Muon and positron interactions and applications
- Nuclear reactor physics and engineering
- Particle Detector Development and Performance
- Meteorological Phenomena and Simulations
University of Arizona
2014-2017
Central China Normal University
2012-2013
Joint Institute for Laboratory Astrophysics
2010-2011
Institut de Recherche sur les Lois Fondamentales de l'Univers
2011
Heidelberg University
2011
University of Colorado Boulder
2010-2011
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2011
Rice University
2005-2009
Using the new Cosmic Origins Spectrograph (COS) on {\it Hubble Space Telescope (HST)}, we obtained moderate-resolution, high signal/noise ultraviolet spectra of HD 209458 and its exoplanet 209458b during transit, both orbital quadratures, secondary eclipse. We compare transit with at non-transit phases to identify spectral features due exoplanet's expanding atmosphere. find that mean flux decreased by $7.8\pm 1.3$% for C II 1334.5323\AA\ 1335.6854\AA\ lines $8.2\pm 1.4$% Si III 1206.500\AA\...
Beating bands in substellar atmospheres Brown dwarfs are objects with masses that between those of large planets and small stars. They share many features gas giant planets, particularly conditions their atmospheres. Apai et al. analyzed how the infrared brightness three brown changes over time. Several perplexing can be explained if clouds rotating within generate beat patterns. Such seen optical images Jupiter but best match Neptune. The results shed light on atmospheric physics around Sun...
We present $Spitzer$/IRAC Ch1 and Ch2 monitoring of six brown dwarfs during 8 different epochs over the course 20 months. For four dwarfs, we also obtained simulataneous $HST$/WFC3 G141 Grism spectra two derived light curves in five narrow-band filters. Probing pressure levels atmospheres, multi-wavelength our targets all exhibit variations, shape evolves timescale a rotation period, ranging from 1.4 h to 13 h. compare shapes estimate phase shifts between observed at wavelengths by comparing...
The formation timescale and final architecture of exoplanetary systems are closely related to the properties molecular disks from which they form. Observations spatial distribution lifetime gas at planet-forming radii (r < 10 AU) important for understanding evolution systems. Towards this end, we present largest spectrally resolved survey H2 emission around low-mass pre-main sequence stars compiled date. We use a combination new archival far-ultraviolet spectra COS STIS instruments on Hubble...
Young stars surrounded by disks with very low mass accretion rates are likely in the final stages of inner disk evolution and therefore particularly interesting to study. We present ultraviolet (UV) observations ~5-9 Myr old RECX-1 RECX-11, obtained Cosmic Origins Spectrograph (COS) Space Telescope Imaging (STIS) on Hubble (HST), as well optical near infrared spectroscopic observations. The two have similar levels UV emission, although evidence indicates that RECX-11 is accreting not. line...
Condensate clouds fundamentally impact the atmospheric structure and spectra of exoplanets brown dwarfs but connections between surface gravity, cloud structure, dust in upper atmosphere, red colors some remain poorly understood. Rotational modulations enable study different same thereby providing a method to isolate effects clouds. Here we present discovery high peak-to-peak amplitude (8%) rotational low-gravity, extremely (J-Ks=2.55) L6 dwarf WISEP J004701.06+680352.1 (W0047). Using Hubble...
We present a far-ultraviolet (FUV) spectral atlas consisting of spectra 91 pre-main-sequence stars. Most stars in this sample were observed with the Space Telescope Imaging Spectrograph and Advanced Camera for Surveys on Hubble (HST). A few archival from International Ultraviolet Explorer Goddard High Resolution HST are included completeness. find strong correlations among O i λ1304 triplet, Si iv λλ1394/1403 doublet, C λ1549 He ii λ1640 line luminosities. For classical T Tauri (CTTSs), we...
We present recent observations from the Hubble Space Telescope-Cosmic Origins Spectrograph aimed at characterizing auroral emission extrasolar planet HD 209458b. obtained medium-resolution (R ∼ 20,000) far-ultraviolet (1150–1700 Å) spectra both Phase 0.25 and 0.75 quadrature positions as well a stellar baseline measurement secondary eclipse. This analysis includes catalog of lines star-subtracted spectrum planet. an model for planetary H2 emission, compare this to spectrum. No unambiguously...
Far-ultraviolet (FUV) radiation plays an important role in determining chemical abundances protoplanetary disks. HI Lyman alpha is suspected to be the dominant component of FUV emission from Classical T Tauri Stars (CTTSs), but difficult measure directly due circumstellar and interstellar absorption. To better characterize intrinsic radiation, we present spectra 14 CTTSs taken with Hubble Space Telescope COS STIS instruments. H2 fluorescence, commonly seen CTTSs, excited by photons,...
ABSTRACT For Classical T Tauri Stars (CTTSs), the resonance doublets of N v , Si iv and C as well He ii 1640 Å line, trace hot gas flows act diagnostics accretion process. In this paper we assemble a large high-resolution, high-sensitivity data set these lines in CTTSs Weak (WTTSs). The sample comprises 35 stars: 1 Herbig Ae star, 28 CTTSs, 6 WTTSs. We find that all have similar shapes. decompose into broad narrow Gaussian components (BC NC). most common (50%) line morphology is low-velocity...
ABSTRACT We exploit the high sensitivity and moderate spectral resolution of Hubble Space Telescope Cosmic Origins Spectrograph to detect far-ultraviolet (UV) features carbon monoxide (CO) present in inner regions protoplanetary disks for first time. spectra classical T Tauri stars HN Tau, RECX-11, V4046 Sgr, representative a range CO radiative processes. Tau shows bands absorption against accretion continuum. The most likely arises warm disk gas. measure column density rotational excitation...
We present deep spectroscopic observations of the classical T Tauri stars DF Tau and V4046 Sgr in order to better characterize two important sources far-ultraviolet continuum emission protoplanetary disks. These new Hubble Space Telescope-Cosmic Origins Spectrograph reveal a combination line from collisionally excited H2 accretion shocks. is dominant 1400-1650 A band spectrum Sgr, while an contributes strongly across Tau. compare models electron-impact induced constrain physical properties...
We present time-resolved near-infrared spectroscopy of two L5 dwarfs, 2MASS J18212815+1414010 and J15074759−1627386, observed with the Wide Field Camera 3 instrument on Hubble Space Telescope (HST). study wavelength dependence rotation-modulated flux variations between 1.1 μm 1.7 μm. find that water absorption bands dwarfs at 1.15 1.4 vary similar amplitudes as adjacent continuum. This differs from results previous HST observations L/T transition in which displays about half amplitude other...
We present an analysis of high-resolution ($R \sim 50,000$) infrared K-band echelle spectra 14 T Tauri stars in the Orion Nebula Cluster. model Zeeman broadening three magnetically sensitive \ion{Ti}{1} lines near $2.2\ \mu$m and consistently detect kilogauss-level magnetic fields stellar photospheres. The data are consistent each case with entire surface being covered fields, suggesting that pressure likely dominates over gas photospheres these stars. These very strong might themselves be...
We present infrared (IR) and optical echelle spectra of the Classical T Tauri star TW Hydrae. Using data, we perform detailed spectrum synthesis to fit atomic molecular absorption lines determine key stellar parameters: Teff = 4126 \pm 24 K, log g 4.84 0.16, [M/H] -0.10 0.12, vsini 5.8 0.6 km/s. The IR is used look for Zeeman broadening photospheric lines. four sensitive Ti I near 2.2 microns find average value magnetic field over entire surface 2.61 0.23 kG. In addition, several nearby...
We present high-resolution (R ≈ 60,000) circular spectropolarimetry of the classical T Tauri star TW Hydrae. analyze 12 photospheric absorption lines and measure net longitudinal magnetic field for six consecutive nights. While no polarization is detected first five nights, a significant Bz = 149 ± 33 G found on sixth night. To rule out spurious instrumental polarization, we apply same analysis technique to several nonmagnetic telluric lines, detecting polarization. further demonstrate...
We present an analysis of infrared (IR) echelle spectra five stars in the TW Hydrae Association (TWA). model Zeeman broadening four magnetic-sensitive \ion{Ti}{1} lines near $2.2 μ$m and measure value photospheric magnetic field averaged over surface each star. To ensure that other mechanisms are properly taken into account, we also inspect several magnetically insensitive CO $2.3 find no excess above produced by stellar rotation instrumental broadening, providing confidence interpretation...
The direct study of molecular gas in inner protoplanetary disks is complicated by uncertainties the spatial distribution gas, time-variability source, and comparison observations across a wide range wavelengths. Some these challenges can be mitigated with far-ultraviolet spectroscopy. Using new obtained HST-Cosmic Origins Spectrograph, we measure column densities rovibrational temperatures for CO H2 observed on line-of-sight through AA Tauri circumstellar disk. A-X absorption bands are...
We report the first detection of molecular hydrogen (H$_{2}$) absorption in Lyman-$\alpha$ emission line profiles two classical T Tauri stars (CTTSs), DF Tau and V4046 Sgr, observed by \emph{HST}/COS. This is energy source for many Lyman-band H$_{2}$ fluorescent lines commonly seen far-ultraviolet spectra CTTSs. find that absorbed pumping transitions from a portion significantly differ amount resulting emission. By assuming additional H I profile along our light sight, we can correct...