Andrew Skemer
A5006054012- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Adaptive optics and wavefront sensing
- Astronomical Observations and Instrumentation
- Calibration and Measurement Techniques
- Atmospheric Ozone and Climate
- Spectroscopy and Laser Applications
- Gamma-ray bursts and supernovae
- Spacecraft and Cryogenic Technologies
- Optical Systems and Laser Technology
- Molecular Spectroscopy and Structure
- Spacecraft Design and Technology
- Astrophysical Phenomena and Observations
- Planetary Science and Exploration
- High-pressure geophysics and materials
- Advanced optical system design
- Scientific Research and Discoveries
- Geophysics and Gravity Measurements
- Space Exploration and Technology
- History and Developments in Astronomy
- Solid State Laser Technologies
- Atomic and Subatomic Physics Research
- Advanced Fiber Laser Technologies
University of California, Santa Cruz
2016-2025
University of California, Irvine
2022
University of California System
2022
University of Arizona
2009-2019
University of Liège
2018
Herzberg Institute of Astrophysics
2018
University of Victoria
2018
Max Planck Society
2015
Max Planck Institute for Radio Astronomy
2015
We report results of a direct imaging survey for giant planets around 80 members the Beta Pic, TW Hya, Tucana-Horologium, AB Dor, and Hercules-Lyra moving groups, observed as part Gemini NICI Planet-Finding Campaign. For this sample, we obtained median contrasts \Delta H=13.9 mag at 1" in combined CH4 narrowband ADI+SDI mode H=15.1 2" H-band ADI mode. found numerous (>70) candidate companions our images. Some these candidates were rejected common-proper motion using archival data; reobserved...
We present 197 planet candidates discovered using data from the first year of NASA K2 mission (Campaigns 0-4), along with results an intensive program photometric analyses, stellar spectroscopy, high-resolution imaging, and statistical validation. distill these into sets 104 validated planets (57 in multi-planet systems), 30 false positives, 63 remaining candidates. Our systems span a range properties, median values R_P = 2.3 R_E, P=8.6 d, Tef 5300 K, Kp=12.7 mag. Stellar spectroscopy...
We present the Vortex Image Processing (VIP) library, a python package dedicated to astronomical high-contrast imaging. Our relies on extensive stack of scientific libraries and aims provide flexible framework for data image processing. In this paper, we describe capabilities VIP related processing sequences acquired using angular differential imaging (ADI) observing technique. implements functionalities building pipelines, encompass- ing pre- post-processing algorithms, potential sources...
We present the highest fidelity spectrum to date of a planetary-mass object. VHS 1256 b is $<$20 M$_\mathrm{Jup}$ widely separated ($\sim$8\arcsec, = 150 au), young, companion that shares photometric colors and spectroscopic features with directly imaged exoplanets HR 8799 c, d, e. As an L-to-T transition object, exists along region color-magnitude diagram where substellar atmospheres from cloudy clear. observed 1256~b \textit{JWST}'s NIRSpec IFU MIRI MRS modes for coverage 1 $\mu$m 20 at...
We present JWST Early Release Science (ERS) coronagraphic observations of the super-Jupiter exoplanet, HIP 65426 b, with Near-Infrared Camera (NIRCam) from 2-5 $\mu$m, and Mid-Infrared Instrument (MIRI) 11-16 $\mu$m. At a separation $\sim$0.82" (86$^{+116}_{-31}$ au), b is clearly detected in all seven our observational filters, representing first images an exoplanet to be obtained by JWST, ever direct detection beyond 5 These demonstrate that exceeding its nominal predicted performance up...
Abstract M dwarfs are common host stars to exoplanets but often lack atmospheric abundance measurements. Late-M also good analogs the youngest substellar companions, which share similar T eff ∼ 2300–2800 K. We present analyses for M7.5 companion HIP 55507 B and its K6V primary star with Keck/KPIC high-resolution ( R 35,000) K -band spectroscopy. First, by including KPIC relative radial velocities between secondary in orbit fit, we improve dynamical mass precision 60% find <?CDATA...
As the only directly imaged multiple planet system, HR 8799 provides a unique opportunity to study physical properties of several planets in parallel. In this paper, we image all four at H-band and 3.3 microns with new LBT adaptive optics PISCES, LBTI/LMIRCam. Our images offer an unprecedented view allowing us obtain H 3.3$ micron photometry innermost (for first time) put strong upper-limits on presence hypothetical fifth companion. We find that are unexpectedly bright compared equilibrium...
We report the discovery of a tight substellar companion to young solar analog PZ Tel, member Beta Pictoris moving group observed with high contrast adaptive optics imaging as part Gemini NICI Planet-Finding Campaign. The was detected at projected separation 16.4 +/- 1.0 AU (0.33 0.01") in April 2009. Second-epoch observations May 2010 demonstrate that is physically associated and shows significant orbital motion. Monte Carlo modeling constrains orbit Tel B eccentricities > 0.6. near-IR...
Young giant exoplanets are a unique laboratory for understanding cool, low-gravity atmospheres. A quintessential example is the massive extrasolar planet $β$ Pic b, which 9 AU from and embedded in debris disk of young nearby A6V star Pictoris. We observed system with first light Magellan Adaptive Optics (MagAO) system. In Paper I we presented CCD detection this MagAO+VisAO. Here present four MagAO+Clio images b at 3.1 $μ$m, 3.3 $L^\prime$, $M^\prime$, including observation fundamental CH$_4$...
We have carried out high contrast imaging of 70 young, nearby B and A stars to search for brown dwarf planetary companions as part the Gemini NICI Planet-Finding Campaign. Our survey represents largest, deepest planets around high-mass (~1.5-2.5 M_sun) conducted date includes planet hosts beta Pic Fomalhaut. obtained follow-up astrometry all candidate within 400 AU projected separation in uncrowded fields identified new low-mass HD 1160 HIP 79797. found that previously known young companion...
We have completed a high-contrast direct imaging survey for giant planets around 57 debris disk stars as part of the Gemini NICI Planet-Finding Campaign. achieved median H-band contrasts 12.4 mag at 0.5" and 14.1 1" separation. Follow-up observations 66 candidates with projected separation < 500 AU show that all them are background objects. To establish statistical constraints on underlying planet population based our data, we developed new Bayesian formalism incorporates (1) non-detections,...
Abstract The Hunt for Observable Signatures of Terrestrial Systems survey searches dust near the habitable zones (HZs) around nearby, bright main-sequence stars. We use nulling interferometry in N band to suppress stellar light and probe low levels HZ 30 stars observed so far. Our overall detection rate is 18%, including four new detections, among which are first three Sun-like two without any previously known circumstellar dust. inferred occurrence rates comparable early-type stars, but...
We present the first ground-based CCD ($\lambda < 1\mu$m) image of an extrasolar planet. Using MagAO's VisAO camera we detected giant planet (EGP) $\beta$ Pictoris b in $Y$-short ($Y_S$, 0.985 $\mu$m), at a separation $0.470 \pm 0.010''$ and contrast $(1.63 0.49) \times 10^{-5}$. This detection has signal-to-noise ratio 4.1, with empirically estimated upper-limit on false alarm probability 1.0%. also new photometry from NICI instrument Gemini-South telescope, $CH_{4S,1\%}$ ($1.58$ $\mu m$),...
Abstract The Large Binocular Telescope Interferometer (LBTI) enables nulling interferometric observations across the N band (8 to 13 μ m) suppress a star’s bright light and probe for faint circumstellar emission. We present statistically analyze results from LBTI/Hunt Observable Signatures of Terrestrial Systems survey exozodiacal dust. By comparing our measurements model predictions based on solar zodiacal dust in band, we estimate 1 σ median sensitivity 23 zodis times system surface...
Using the Keck Planet Imager and Characterizer (KPIC), we obtained high-resolution (R$\sim$35,000) $K$-band spectra of four planets orbiting HR 8799. We clearly detected \water{} CO in atmospheres 8799 c, d, e, tentatively a combination b. These are most challenging directly imaged exoplanets that have been observed at high spectral resolution to date when considering both their angular separations flux ratios. developed forward modeling framework allows us jointly fit diffracted starlight...
The Keck Planet Imager and Characterizer (KPIC) is a purpose-built instrument to demonstrate technological instrumental concepts initially developed for the exoplanet direct imaging field. Located downstream of current II adaptive optic (AO) system, KPIC contains fiber injection unit (FIU) capable combining high-contrast capability AOs system with high dispersion spectroscopy resolution infrared spectrograph (NIRSPEC). Deployed at in September 2018, this has already been used acquire...
Direct imaging studies have mainly used low-resolution spectroscopy ($R\sim20-100$) to study the atmospheres of giant exoplanets and brown dwarf companions, but presence clouds has often led degeneracies in retrieved atmospheric abundances (e.g. C/O, metallicity). This precludes clear insights into formation mechanisms these companions. The Keck Planet Imager Characterizer (KPIC) uses adaptive optics single-mode fibers transport light NIRSPEC ($R\sim35,000$ $K$ band), aims address challenges...
The direct characterization of exoplanetary systems with high contrast imaging is among the highest priorities for broader exoplanet community. As large space missions will be necessary detecting and characterizing exo-Earth twins, developing techniques technology exoplanets a driving focus For first time, JWST directly observe extrasolar planets at mid-infrared wavelengths beyond 5$\mu$m, deliver detailed spectroscopy revealing much more precise chemical abundances atmospheric conditions,...
Abstract The detection of satellites around extrasolar planets, so called exomoons, remains a largely unexplored territory. In this work, we study the potential detecting these elusive objects from radial velocity monitoring self-luminous, directly imaged planets. This technique is now possible thanks to development dedicated instruments combining power high-resolution spectroscopy and high-contrast imaging. First, demonstrate sensitivity with mass ratio 1%–4% at separations similar Galilean...
Abstract AF Lep A+b is a remarkable planetary system hosting gas-giant planet that has the lowest dynamical mass among directly imaged exoplanets. We present an in-depth analysis of atmospheric composition star and to probe planet’s formation pathway. Based on new high-resolution spectroscopy A, we measure uniform set stellar parameters elemental abundances (e.g., [Fe/H] = −0.27 ± 0.31 dex). The ( <?CDATA ${2.8}_{-0.5}^{+0.6}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"...
Abstract Using Keck Planet Imager and Characterizer high-resolution ( R ∼ 35,000) spectroscopy from 2.29 to 2.49 μ m, we present uniform atmospheric retrievals for eight young substellar companions with masses of ∼10–30 M Jup , orbital separations spanning ∼50–360 au, T eff between ∼1500 2600 K. We find that all have solar C/O ratios metallicities within the 1 σ –2 level, measurements clustered around composition. Stars in same stellar associations as our systems near-solar abundances, so...
Abstract We present high-resolution K -band emission spectra of the quintessential hot Jupiter HD 189733 b from Keck Planet Imager and Characterizer. Using a Bayesian retrieval framework, we fit dayside pressure–temperature profile, orbital kinematics, mass-mixing ratios H 2 O, CO, CH 4 , NH 3 HCN, S, 13 CO/ 12 CO ratio. measure mass fractions <?CDATA ${\mathrm{logH}}_{2}{\rm{O}}=-{2.0}_{-0.4}^{+0.4}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub>...
Abstract The unprecedented medium-resolution ( R λ ∼ 1500–3500) near- and mid-infrared (1–18 μ m) spectrum provided by JWST for the young (140 ± 20 Myr) low-mass (12–20 M Jup ) L–T transition (L7) companion VHS 1256 b gives access to a catalog of molecular absorptions. In this study, we present comprehensive analysis data set utilizing forward-modeling approach applying our Bayesian framework, ForMoSA . We explore five distinct atmospheric models assess their performance in estimating key...