A5009359010- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Space Exploration and Technology
- Gamma-ray bursts and supernovae
- Molecular Spectroscopy and Structure
- Ionosphere and magnetosphere dynamics
- Atmospheric Ozone and Climate
- Astrophysics and Cosmic Phenomena
- Geomagnetism and Paleomagnetism Studies
- Nuclear physics research studies
- Adaptive optics and wavefront sensing
- Geophysics and Gravity Measurements
- Planetary Science and Exploration
- Inorganic Fluorides and Related Compounds
- Atomic and Molecular Physics
- CCD and CMOS Imaging Sensors
- History and Developments in Astronomy
- Radio Astronomy Observations and Technology
- Spectroscopy and Laser Applications
- Dust and Plasma Wave Phenomena
Rice University
2015-2024
University of Houston
2023
The University of Texas at Austin
1996-2019
University of Hawaii System
2001-2012
Association of Universities For Research In Astronomy
2012
U.S. National Science Foundation
2012
Kitt Peak National Observatory
2012
Canada–France–Hawaii Telescope
2001-2007
University of California, Berkeley
1996-2003
University of California, Santa Barbara
2003
We report new magnetic field measurements for 14 classical T Tauri stars (CTTSs). combine these data with one previous determination in order to compare our observed strengths the predicted by magnetospheric accretion models. use literature on stellar mass, radius, rotation period, and disk rate predict strength that should be present each of according show measured values do not correlate simple theory. also X-ray luminosity test a recent relationship expressing as function surface flux...
We use soft X-ray and magnetic field observations of the Sun (quiet Sun, bright points, active regions, integrated solar disk) stars (dwarf pre-main-sequence) to study relationship between total unsigned flux, Φ, spectral radiance, LX. find that Φ LX exhibit a very nearly linear over 12 orders magnitude, albeit with significant levels scatter. This suggests universal flux power dissipated through coronal heating. If can be assumed linear, it is consistent an average volumetric heating rate ~...
We examine several theories that describe how stellar magnetic fields on classical T Tauri stars (CTTSs) interact with their surrounding accretion disks. demonstrate these require field strengths ranging from a few hundred to thousand gauss, depending which model is used and more importantly the properties of individual systems. For example, CTTS BP Tau predicted have relatively strong (1.4-4.1 kG), should be detectable. present infrared (IR) optical echelle spectra reference similar...
We present photometry of 13 transits XO-3b, a massive transiting planet on an eccentric orbit. Previous data led to two inconsistent estimates the planetary radius. Our strongly favor smaller radius, with increased precision: R_p = 1.217 +/- 0.073 R_Jup. A conflict remains between mean stellar density determined from light curve, and surface gravity shapes spectral lines. argue curve should take precedence, revise system parameters accordingly. The radius is about 1 sigma larger than...
We have detected Zeeman splitting of the Fe I line (geff = 2.5) at 8468.40 Å in very active M4.5 Ve stars Gliese 729 and 873 (EV Lac). High-resolution (R 120,000), low-noise (~0.5%) spectra show clear Zeeman-shifted σ components from which we infer field strengths 2-4 kG, independent uncertainties model atmospheres. Similar observations a sequence (M0 V-M5 V) low-activity M dwarfs demonstrate that wing are not due to ubiquitous TiO lines vicinity. This strongly suggests discrepancies shape...
We observed the classical T Tauri star TW Hya with Space Telescope Imaging Spectrograph on board Hubble (HST) using E140M grating, from 1150 to 1700 Å, E230M 2200 2900 and Far Ultraviolet Spectroscopic Explorer 900 1180 Å. Emission in 146 Lyman-band H2 lines, representing 19 progressions, dominates spectral region 1250 1650 The total emission line flux is 1.94 × 10-12 ergs cm-2 s-1, which corresponds 1.90 10-4 L☉ at Hya's distance of 56 pc. A broad stellar Lyα photoexcites excited...
We measure the temperature of warm gas at planet-forming radii in disk around classical T Tauri star (CTTS) TW Hya by modeling H2 fluorescence observed Hubble Space Telescope Imaging Spectrograph and Far Ultraviolet Spectroscopic Explorer spectra. Strong Lyα emission irradiates a surface within 2 AU central pumps certain excited levels H2. simulate one-dimensional plane-parallel atmosphere to estimate fluxes for 140 lines reconstruct profile incident upon The excitation can be determined...
We report on a V = 11.2 early K dwarf, XO-2 (GSC 03413-00005), that hosts Rp 0.98±0.010.03 RJ, Mp 0.57 ± 0.06 MJ transiting extrasolar planet, XO-2b, with an orbital period of 2.615857 0.000005 days. has high metallicity, [Fe/H ] 0.45 0.02, proper motion, μtot 157 mas yr−1, and common motion stellar companion 31'' separation. The two stars are nearly identical twins, very similar spectra apparent magnitudes. Due to the these dwarf have mass radius close solar, M⋆ 0.98 0.02 M☉ R⋆...
We report the discovery of a massive (Mpsini = 13.02 +/- 0.64 Mjup; total mass 13.25 Mjup), large (1.95 0.16 Rjup) planet in transiting, eccentric orbit (e 0.260 0.017) around 10th magnitude F5V star constellation Camelopardalis. designate XO-3b, and XO-3, also known as GSC 03727-01064. The orbital period XO-3b is 3.1915426 0.00014 days. XO-3 lacks trigonometric distance; we estimate its distance to be 260 23 pc. radius 2.13 0.21 Rsun, 1.41 0.08 Msun, vsini 18.54 0.17 km/s, metallicity...
The Large Synoptic Survey Telescope is designed to provide an unprecedented optical imaging dataset that will support investigations of our Solar System, Galaxy and Universe, across half the sky over ten years repeated observation. However, exactly how LSST observations be taken (the observing strategy or "cadence") not yet finalized. In this dynamically-evolving community white paper, we explore detailed performance anticipated science expected depend on small changes strategy. Using...
Abstract Mature super-Earths and sub-Neptunes are predicted to be ≃ Jovian radius when younger than 10 Myr. Thus, we expect find 5–15 R ⊕ planets around young stars even if their older counterparts harbor none. We report the discovery validation of TOI 1227b, a 0.85 ± 0.05 J (9.5 ) planet transiting very-low-mass star (0.170 0.015 M ⊙ every 27.4 days. 1227's kinematics strong lithium absorption confirm that it is member previously discovered subgroup in Lower Centaurus Crux OB association,...
We report results from a multiwavelength observing campaign conducted during 2000 March on the flare star AD Leo. Simultaneous data were obtained several ground- and space-based observatories, including observations of eight sizable flares. discuss correlation line continuum emission in optical ultraviolet wavelength regimes, as well energy budget, we find that properties are remarkably similar even for flares very different evolutionary morphology. This suggests common heating mechanism...
We report the discovery that classical T Tauri star DQ Tan is a double-lined spectroscopic binary. The orbital period 15.804 days, with large eccentricity e=0.556. mass ratio 0.97±0.15. have monitored Tau photometrically over two observing seasons and observed recurring episodes during which stars get brighter (≍0.5 mag in V) bluer (≍-0.2 V-I). When combined photometry literature (time span ≍5000 days), Scargle periodogram analysis reveals highly significant periodicity of 15.80 essentially...
view Abstract Citations (142) References (74) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Simultaneous Extreme-Ultraviolet Explorer and Optical Observations of AD Leonis: Evidence for Large Coronal Loops the Neupert Effect in Stellar Flares Hawley, Suzanne L. ; Fisher, George H. Simon, Theodore Cully, Scott Deustua, Susana E. Jablonski, Marek Johns-Krull, Christopher M. Pettersen, Bjorn R. Smith, Verne Spiesman, William J. Valenti, Jeffrey We report on...
High-resolution (R ≈ 60,000) circular spectropolarimetry of the classical T Tauri star BP is presented. No net polarization detected in photospheric absorption lines, placing strong limits (3 σ) on mean longitudinal magnetic field (±200 G) that present over surface star. On other hand, measured He I λ5876 emission line Tau, indicating a 2460±120 G formation region. This implies accretion occurs preferentially along large-scale loops occupy small fraction stellar surface. These observations...
We present the results of a campaign to observe flares on M dwarf flare star EV Lacertae over course two days in 2001 September, utilizing combination radio continuum, optical photometric and spectroscopic, ultraviolet X-ray spectroscopic observations, characterize multi-wavelength nature from this active, single late-type star. find every wavelength region which we observed. In context, start intense is coincident with an impulsive U-band flare, within one minute, yet there no signature...
A planet transits an 11th magnitude, G1V star in the constellation Corona Borealis. We designate XO-1b, and star, XO-1, also known as GSC 02041-01657. XO-1 lacks a trigonometric distance; we estimate it to be 200+-20 pc. Of ten stars currently host extrasolar transiting planets, is most similar Sun its physical characteristics: radius 1.0+-0.08 R_Sun, mass 1.0+-0.03 M_Sun, V sini < 3 km/s, metallicity [Fe/H] 0.015+-0.04. The orbital period of XO-1b 3.941534+-0.000027 days, one longer ones...
We present results from an ongoing multiwavelength radial velocity (RV) survey of the Taurus-Auriga star forming region as part our effort to identify pre--main sequence giant planet hosts. These 1-3 Myr old T Tauri stars significant challenges traditional RV surveys. The presence strong magnetic fields gives rise large, cool spots. spots introduce jitter which can mimic modulation a planet-mass companion. To distinguish between spot-induced and planet-induced modulation, we conduct...
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...
ABSTRACT The ∼2 Myr old classical T Tauri star CI Tau shows periodic variability in its radial velocity (RV) variations measured at infrared (IR) and optical wavelengths. We find that these observations are consistent with a massive planet ∼9 day period orbit. These results based on 71 IR RV measurements of this system obtained over five years, 26 nine years. was also observed photometrically the 34 nights ∼one month 2012. data alone inadequate to identify an orbital period, likely result...
Context. The origin of the fossil magnetic fields detected in 5 to 10% intermediate-mass main sequence stars is still highly debated. Aims. We want bring observational constraints a large population pre-main (PMS) order test theory that convective-dynamo generated during PMS phases stellar evolution can occasionally relax into on sequence. Methods. Using distance estimations, photometric measurements, and spectropolarimetric data from HARPSpol ESPaDOnS 38 stars, we determined fundamental...
In high dispersion spectra of rotating bodies such as stars and planets, the rotation contributes significantly to, sometimes dominates, line broadening. We present a simple method for rotationally broadening large wavelength ranges high-dispersion spectra. The is rapid scales linearly with length spectrum array. For ranges, much faster than popular convolution-based provide code implementation this in publicly accessible repository.
We use our ultraviolet (UV) atlas of pre-main-sequence stars constructed from all useful, short-wavelength, low-resolution spectra in the International Ultraviolet Explorer (IUE) satellite Final Archive to analyze short-wavelength UV properties 49 T Tauri (TTSs). compare line and continuum fluxes these TTSs with each other previously published parameters systems, including rotation rate, infrared excess, mass accretion rate. The classical (CTTSs) appears originate a ~10,000 K optically thick...