A5005752563- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Atmospheric Ozone and Climate
- Adaptive optics and wavefront sensing
- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Molecular Spectroscopy and Structure
- Scientific Research and Discoveries
- High-pressure geophysics and materials
- Advanced Frequency and Time Standards
- History and Developments in Astronomy
- Photocathodes and Microchannel Plates
- Cosmology and Gravitation Theories
- Ionosphere and magnetosphere dynamics
- Planetary Science and Exploration
- Isotope Analysis in Ecology
- Black Holes and Theoretical Physics
- Cardiovascular Function and Risk Factors
- Calibration and Measurement Techniques
Laboratory for Atmospheric and Space Physics
2019-2024
University of Colorado Boulder
2019-2024
Arizona State University
2017-2019
Max Planck Institute for Astronomy
2019
Max Planck Society
2019
Wesleyan University
2014-2018
Wake Forest University
2018
Rice University
2012-2016
Bow shocks are ubiquitous astrophysical phenomena resulting from the supersonic passage of an object through a gas. Recently, pre-transit absorption in UV metal transitions hot Jupiter (HJ) exoplanets HD 189733b and WASP12-b have been interpreted as being caused by material compressed planetary bow shock. Here we present robust detection time-resolved pre-transit, well in-transit signature around HJ exoplanet using high spectral resolution observations several hydrogen Balmer lines. The line...
Abstract HD 189733 b is one of the most well studied exoplanets due to its large transit depth and host star brightness. The focus on this object has produced a number high-cadence observations using high-resolution optical spectrographs. Here we present an analysis seven full H α transits HARPS 3.6 meter La Silla telescope HIRES Keck I, taken over course nine years from 2006 2015. transmission signals are analyzed as function stellar activity level, measured normalized core flux Ca ii K...
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...
As followup to our recent detection of a pre-transit signal around HD 189733 b, we obtained full phase coverage single planetary transit. The is again detected in the Balmer lines but with variable strength and timing, suggesting that bow shock geometry reported previous work does not describe from latest We also demonstrate use Ca II H K residual core flux as proxy for stellar activity level throughout A moderate trend found between absorption 2013 data flux. This suggests some hydrogen can...
Nine metal-polluted white dwarfs are observed with medium-resolution optical spectroscopy,where photospheric abundances determined and interpreted through comparison against solar system objects. An improved method of making such comparisons is presented that overcomes potential weaknesses prior analyses, the numerous sources error considered to highlight limitations on interpretation. The stars inferred be accreting rocky, volatile-poor asteroidal materials origins in differentiated bodies,...
Atmospheric escape is a fundamental process that affects the structure, composition, and evolution of many planets. The signatures are detectable on close-in, gaseous exoplanets orbiting bright stars, owing to high levels extreme-ultraviolet irradiation from their parent stars. Colorado Ultraviolet Transit Experiment (CUTE) CubeSat mission designed take advantage near-ultraviolet stellar brightness distribution conduct survey extended atmospheres nearby close-in CUTE payload magnifying NUV...
This paper reports circular spectropolarimetry and X-ray observations of several polluted white dwarfs including WD 1145+017, with the aim to constrain behavior disk material instantaneous accretion rates in these evolved planetary systems. Two stars previously observed Zeeman splitting, 0322-019 2105-820, are detected above 5 sigma <Bz> > 1 kG, while 1929+011, 2326+049 yield (null) detections below this minimum level confidence. For latter three stars, high-resolution spectra atmospheric...
We examine He i λ10830 profile morphologies for a sample of 56 Herbig Ae/Be stars (HAEBES). find significant differences between HAEBES and classical T-Tauri (CTTS) in the statistics both blueshifted absorption (i.e., mass outflows) redshifted features infall or accretion). Our results suggest that, general, Be (HBe) do not accrete material from their inner disks same manner as CTTS, which are believed to via magnetospheric accretion, whereas Ae (HAe) generally show evidence accretion. no...
Changes in levels of stellar activity can mimic absorption signatures transmission spectra from circumplanetary material. The frequency and magnitude these changes is thus important to understand order attribute any particular signal the environment. We present short-cadence, high-resolution out-of-transit H$\alpha$ for hot Jupiter host HD 189733 establish intrinsic variations line core. find that core strength similar those observed immediately pre- post-transit two independent data sets...
Abstract We present a spectrally and temporally resolved detection of the optical Mg i triplet at 7.8 σ in extended atmosphere ultra-hot Jupiter KELT-9 b, adding to list detected metal species hottest gas giant currently known. Constraints are placed on density radial extent excited hydrogen envelope using simultaneous observations H α β under assumption spherically symmetric atmosphere. find that planetary rotational broadening <?CDATA ${v}_{\mathrm{rot}}={8.2}_{-0.7}^{+0.6}$?> km s −1 is...
High energy X-ray and ultraviolet (UV) radiation from young stars impacts planetary atmospheric chemistry mass loss. The active $\sim 22$ Myr M dwarf AU Mic hosts two exoplanets orbiting interior to its debris disk. Therefore, this system provides a unique opportunity quantify the effects of stellar XUV irradiation on atmospheres as function both age orbital separation. In paper we present over 5 hours Far-UV (FUV) observations taken with Cosmic Origins Spectrograph (COS; 1070-1360 Angstrom)...
Abstract We present time-series spectra revealing changes in the circumstellar line profiles for white dwarf WD 1145 + 017. Over course of 2.2 years, show complete velocity reversals absorption, moving from strongly redshifted 2015 April to blueshifted 2017 June. The depth absorption also varies, increasing by a factor two over same period. dramatic are consistent with eccentric gas rings undergoing general relativistic precession. As argument periapsis relative sight, transiting shifts...
We report on the discovery of three transiting super-Earths around K2-155 (EPIC 210897587), a relatively bright early M dwarf ($V=12.81$ mag) observed during Campaign 13 NASA K2 mission. To characterize system and validate planet candidates, we conducted speckle imaging high-dispersion optical spectroscopy, including radial velocity measurements. Based light curve spectroscopic characterization host star, sizes orbital periods are $1.55_{-0.17}^{+0.20}\,R_\oplus$ $6.34365\pm 0.00028$ days...
The infrared dust emission from the white dwarf GD 56 is found to rise and fall by 20 per cent peak-to-peak over 11.2 yr, consistent with ongoing production depletion. It hypothesized that produced via collisions associated an evolving disc, temporarily increasing emitting surface of warm debris, subsequently destroyed or assimilated within a few years. variations are debris does not change temperature, indicating depleted fixed range orbital radii. Gas in may rapidly re-condense onto...
Abstract Variability in the far-ultraviolet (FUV) emission produced by stellar activity affects photochemistry and heating orbiting planetary atmospheres. We present a comprehensive analysis of FUV variability GJ 436, field-age M2.5V star ( P rot ≈ 44 days) that is orbited warm Neptune-sized planet M 25 ⊕ , R 4.1 orb 2.6 days). Observations at three epochs from 2012 to 2018 span nearly full cycle, sample two rotations orbital periods planet, reveal multitude brief flares. From 2018, star’s...
We examine a broad range of mass flow diagnostics in large sample Herbig Ae/Be stars (HAEBES) using high resolution optical spectra. The Hβ and He i 5876 Å lines show the highest incidence P Cygni (30%) inverse (14%) morphologies, respectively. Fe ii 4924 line also shows profiles (11%). find support for many conclusions reached study based on analysis λ10830 HAEBES. Namely, HAEBES exhibit smaller fractions both blueshifted absorption (i.e., outflow) redshifted infall or accretion) than their...
Observations of extended atmospheres around hot planets have generated exciting results concerning the dynamics escaping planetary material. The configuration gas can result in asymmetric transit features, producing both pre- and post-transit absorption specific atomic transitions. Measuring velocity strength provide constraints on mass loss mechanism and, potentially, clues to interactions between planet host star. Here we present a search for H$\alpha$ circumplanetary environments KELT-3 b...
Abstract With the recent discovery of transiting planetary material around WD 1145+017, a critical target has been identified that links evolution systems with debris disks and their accretion onto star. We present series observations, five epochs over year, taken Keck VLT, which for first time show variability circumstellar absorption in gas disk surrounding 1145+017 on timescales minutes to months. Circumstellar is measured more than 250 lines 14 ions among 10 different elements associated...
Chromospherically sensitive atomic lines display different spectra in stellar active regions, spots, and the photosphere, raising possibility that exoplanet transmission are contaminated by contrast between various portions of disk. To explore this effect, we performed transit simulations G K-type stars for spectral Ca II K at 3933 \AA, Na I 5890 H 6563 \AA\ (H$\alpha$), He 10830 \AA. We find strong facular emission large coverage fractions can contribute a non-negligible amount to spectra,...
We report on the discovery of three transiting planets around GJ~9827. The have radii 1.75$_{-0.12}^{+0.11 }$, 1.36$_{- 0.09 }^{+ 0.09}$, and 2.10$_{- 0.15 }$~R$_{\oplus}$, periods 1.20896, 3.6480, 6.2014 days, respectively. detection was made in Campaign 12 observations as part our K2 survey nearby stars. GJ~9827 is a $V = 10.39$~mag K6V star at distance 30.3 parsecs nearest to be found hosting by Kepler K2. radial velocity follow-up, high resolution imaging, multiple objects near...
Abstract We have obtained >10 hr of medium-resolution ( R ∼ 15,000) spectroscopic exposures on the transiting exoplanet host star WASP-12, including ∼2 while its planet, WASP-12b, is in transit, with Hobby-Eberly Telescope. The out-of-transit and in-transit spectra are coadded into master spectra, from which we create a transmission spectrum. Strong, statistically significant absorption features seen spectrum at H α Na i (the D doublet). There suggestion pre- post-transit both when...
Context. Observationally constraining the atmospheric temperature-pressure (TP) profile of exoplanets is an important step forward for improving planetary atmosphere models, further enabling one to place detection spectral features and measurement atomic molecular abundances through transmission emission spectroscopy on solid ground. Aims. The aim constrain TP ultra-hot Jupiter KELT-9b by fitting synthetic spectra observed H$\alpha$ H$\beta$ lines identify why self-consistent models are...
Abstract M dwarf stars are excellent candidates around which to search for exoplanets, including temperate, Earth-sized planets. To evaluate the photochemistry of planetary atmosphere, it is essential characterize UV spectral energy distribution planet’s host star. This wavelength regime important because molecules in atmosphere such as oxygen and ozone have highly wavelength-dependent absorption cross sections that peak (900–3200 Å). We seek provide a broadly applicable method estimating...
Abstract We present a new Keck/NIRSPEC observation of metastable helium absorption from the upper atmosphere HD 189733b, hot Jupiter orbiting nearby moderately active star. measure an average transit depth 0.420% ± 0.013% integrated over [−20, 20] km s −1 velocity range. Comparing this measurement to eight previously published observations with different instruments, we find that our is 32% (9 σ ) lower than three CARMENES transits, but only 16% (4.4 five GIANO transits. perform 1D...