Michael C. Liu
A5100333916- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Adaptive optics and wavefront sensing
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Spectroscopy and Laser Applications
- Migration, Ethnicity, and Economy
- Photonic and Optical Devices
- Semiconductor Lasers and Optical Devices
- Atmospheric Ozone and Climate
- Planetary Science and Exploration
- Solar and Space Plasma Dynamics
- History and Developments in Astronomy
- Molecular Spectroscopy and Structure
- Geophysics and Gravity Measurements
- Astrophysics and Cosmic Phenomena
- Pulsars and Gravitational Waves Research
- Space Satellite Systems and Control
- Calibration and Measurement Techniques
- Optimal Power Flow Distribution
- CCD and CMOS Imaging Sensors
Los Angeles Unified School District
2018-2025
University of Hawaii System
2015-2024
University of Hawaiʻi at Mānoa
2015-2024
Intertek (United States)
2015-2024
University of California, Irvine
2023
Institute of Astronomy
2010-2023
Hodges University
2023
The University of Melbourne
2012-2022
University of California, Santa Cruz
2004-2022
University of California, Los Angeles
2014-2022
The Spitzer-COSMOS survey (S-COSMOS) is a Legacy program (Cycles 2+3) designed to carry out uniform deep of the full 2 sq deg COSMOS field in all seven Spitzer bands (3.6, 4.5, 5.6, 8.0, 24.0, 70.0, 160.0 u). This paper describes parameters, mapping strategy, data reduction procedures, achieved sensitivities date, and complete set for future reference. We show that observed infrared backgrounds S-COSMOS are within 10% predicted background levels. fluctuations at 24u have been measured do not...
We present photometric and spectroscopic observations of 23 high-redshift supernovae (SNe) spanning a range z = 0.34-1.03, nine which are unambiguously classified as Type Ia. These SNe were discovered during the IfA Deep Survey, began in 2001 September observed total 2.5 deg2 to depth approximately m ≈ 25-26 RIZ over 9-17 visits, typically every 1-3 weeks for nearly 5 months, with additional continuing until 2002 April. give brief description survey motivations, observational strategy,...
We present the first results from our high-precision infrared (IR) astrometry program at Canada-France-Hawaii Telescope. measure parallaxes for 83 ultracool dwarfs (spectral types M6--T9) in 49 systems, with a median uncertainty of 1.1 mas (2.3%) and as good 0.7 (0.8%). provide 48 objects 29 another 27 17 we significantly improve upon published results, (best) improvement 1.7x (5x). Three systems show astrometric perturbations indicative orbital motion; two are known binaries...
Over the duration of Kepler mission, KIC8462852 was observed to undergo irregularly shaped, aperiodic dips in flux up $\sim 20$\%. The dipping activity can last for between 5 and 80 days. We characterize object with high-resolution spectroscopy, spectral energy distribution fitting, radial velocity measurements, imaging, Fourier analyses light curve. determine that is a typical main-sequence F3 V star exhibits no significant IR excess, has very close interacting companions. In this paper, we...
We have used Pan-STARRS1 to discover an extremely red late-L dwarf, which has (J-K)_MKO = 2.84 and (J-K)_2MASS 2.78, making it the reddest known field dwarf second only 2MASS J1207-39b among substellar companions. Near-IR spectroscopy shows a spectral type of L7 reveals triangular H-band continuum weak alkali (K I Na I) lines, hallmarks low surface gravity. astrometry from Hawaii Infrared Parallax Program gives distance 24.6+/-1.4 pc indicates much fainter J-band absolute magnitude than L...
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 a near-infrared (0.9–2.4 μm) spectroscopic study of 73 field ultracool dwarfs having and/or kinematic evidence youth (≈10–300 Myr). Our sample is composed 48 low-resolution (R ≈ 100) spectra and 41 moderate-resolution ≳ 750–2000). First, we establish method for spectral typing M5–L7 at near-IR wavelengths that independent gravity. find both visual index-based classification in the provides consistent types with optical types, though small systematic offset case J K band. Second,...
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 full results of our decade-long astrometric monitoring programs targeting 31 ultracool binaries with component spectral types M7-T5. Joint analysis resolved imaging from Keck Observatory and Hubble Space Telescope unresolved astrometry CFHT/WIRCam yields parallactic distances for all systems, robust orbit determinations 23 photocenter orbits 19 systems. As a result, we measure 38 precise individual masses spanning 30-115 $M_{\rm Jup}$. determine model-independent substellar...
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...
A combination of high-resolution and wide-field imaging reveals two binary stars one triple star system among the sample first 11 with planets detected by radial velocity variations. High-resolution speckle or adaptive optics (AO) data probe subarcsecond scales down to diffraction limit Keck 10 m Lick 3 m, direct images AO are sensitive a wider field, extending 10'' 38'', depending on camera. One system—HD 114762—was not previously known be spatially resolved multiple system; additional...
To empirically calibrate the IR surface brightness fluctuation (SBF) distance scale and probe properties of unresolved stellar populations, we measured fluctuations in 65 galaxies using NICMOS on Hubble Space Telescope. The early-type this sample include elliptical S0 spiral bulges a variety environments. Absolute magnitudes F160W (1.6 μm) filter (F160W) were derived for each galaxy previously I-band SBF Cepheid variable star distances. SBFs can be used to measure distances with relative...
We present an analysis of ∼5 years Lick Observatory radial velocity measurements targeting a uniform sample 31 intermediate-mass (IM) subgiants (1.5 ≲ M*/M☉≲ 2.0) with the goal measuring occurrence rate Jovian planets around (evolved) A-type stars and comparing distributions their orbital physical characteristics to those Sun-like stars. provide updated solutions incorporating new for five known planet-hosting in our sample; uncertainties fitted parameters are assessed using Markov-Chain...
We present the discovery of a circumstellar dust disk surrounding AU Microscopii (AU Mic, GJ 803, HD 197481). This young M star at 10 parsec has same age and origin as β Pictoris, another nearby surrounded by disk. The Mic is detected between 50 astronomical units (AU) 210 radius, region where lifetimes exceed stellar age. Thus, nearest we directly observe solid material required for planet formation. Because 85% stars are M-type, provides new clues on how majority planetary systems might...
[Abridged] We present 2.12-2.23 um high contrast integral field spectroscopy of the extrasolar planet HR 8799 b. Our observations were obtained with OSIRIS on Keck II telescope and sample 2.2 CH4 feature, which is useful for spectral classification as a temperature diagnostic ultracool objects. The spectrum b relatively featureless, little or no methane absorption, does not exhibit strong seen in T dwarfs similar absolute magnitudes. Overall, we find that has type consistent L5-T2, although...
We present near-infrared (1.0-2.4 μm) spectra confirming the youth and cool temperatures of six brown dwarfs low-mass stars with circumstellar disks toward Chamaeleon II Ophiuchus star-forming regions. The spectrum one our objects indicates a spectral type ~L1, making it latest young identified to date. Comparing dwarfs, field giant stars, we define 1.49-1.56 μm H2O index capable determining ±1 subtype, independent gravity. have also defined an based on 1.14 sodium feature that is sensitive...
Small, cool planets represent the typical end-products of planetary formation. Studying architectures these systems, measuring planet masses and radii, observing planets' atmospheres during transit directly informs theories assembly, migration, evolution. Here we report discovery three small orbiting a bright (Ks = 8.6 mag) M0 dwarf using data collected as part K2, new ecliptic survey re-purposed Kepler spacecraft. Stellar spectroscopy K2 photometry indicate that system hosts transiting with...
Evidence is presented that 2MASS J03202839–0446358, a late-type dwarf with discrepant optical (M8:) and near-infrared (L1) spectral types, an as-yet unresolved stellar/brown binary M T components. This conclusion based on low-resolution, spectroscopy reveals subtle but distinctive absorption feature at 1.6 μ m . The feature, which also present in the combined light spectrum of M8.5 + T6 SCR 1845–6357, arises from combination FeH primary pseudocontinuum flux T5 ± 1 secondary, as ascertained...
We have completed a high-resolution (R=60,000) optical spectroscopic survey of 185 nearby M dwarfs identified using ROSAT data to select active, young objects with fractional X-ray luminosities comparable or greater than Pleiades members. Our targets are drawn from the NStars 20-pc census and Moving-M sample distances determined parallaxes spectrophotometric relations. Nearly half resulting not present in Gliese catalog no previously published spectral types. 30 binaries (SBs) sample, which...
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...
We present the discovery of a wide (67 AU) substellar companion to nearby (21 pc) young solar-metallicity M1 dwarf CD−35 2722, member ≈100 Myr AB Doradus association. Two epochs astrometry from NICI Planet-Finding Campaign confirm that 2722 B is physically associated with primary star. Near-IR spectra indicate spectral type L4±1 moderately low surface gravity, making it one coolest companions found date. The absorption lines and near-IR continuum shape agree especially well dusty field L4.5...
We report the discovery of 76 new T dwarfs from UKIDSS Large Area Survey (LAS). Near-infrared broad and narrow-band photometry spectroscopy are presented for objects, along with WISE warm-Spitzer photometry. Proper motions 128 a two epoch LAS proper motion catalogue. use these to identify benchmark systems: LHS 6176AB, T8+M4 pair HD118865AB, T5.5+F8 pair. Using age constraints primaries evolutionary models constrain radii we have estimated their physical properties bolometric luminosity....