A5087734784- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Galaxies: Formation, Evolution, Phenomena
- Space Exploration and Technology
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Planetary Science and Exploration
- Advanced Frequency and Time Standards
- GNSS positioning and interference
- Inorganic Fluorides and Related Compounds
- Advanced Optical Sensing Technologies
- Spectroscopy and Laser Applications
- History and Developments in Astronomy
- Economic Growth and Productivity
- Atomic and Subatomic Physics Research
- Dark Matter and Cosmic Phenomena
- Advanced Thermodynamic Systems and Engines
- Radio Astronomy Observations and Technology
- High-pressure geophysics and materials
United States Naval Observatory
2017-2024
Gemini North Observatory
2023
NSF’s NOIRLab
2023
W.M. Keck Observatory
2009-2016
University of Hawaii System
2001-2010
California Institute of Technology
2007
Canada–France–Hawaii Telescope
2005
University of Hawaiʻi at Mānoa
2003
We present the first near-IR scattered light detection of transitional disk associated with Herbig Ae star MWC 758 using data obtained as part Strategic Exploration Exoplanets and Disks Subaru, 1.1 micron HST/NICMOS data. While sub-millimeter studies suggested there is a dust-depleted cavity r=0.35, we find close 0.1 (20-28 AU) from star, no visible at H, K', or Ks. two small-scaled spiral structures which asymmetrically shadow outer disk. model one spirals density wave theory, derive aspect...
We present the discovery of two giant planets orbiting stars in Praesepe (also known as Beehive Cluster). These are first hot Jupiters an open cluster and only to orbit Sun-like, main-sequence a cluster. The detected from Doppler shifted radial velocities; line bisector spans activity indices show no correlation with orbital phase, confirming variations caused by planetary companions. Pr0201b orbits V=10.52 late F dwarf period 4.4264 +/- 0.0070 days has minimum mass 0.540 0.039 Mjup, Pr0211b...
Moderate-dispersion (R ∼ 5400), optical spectroscopy of seven brown dwarf candidate members the Pleiades was obtained using Echellette Spectrograph and Imager on Keck II telescope. The proper motion photometrically selected sample lies single-star main sequence cluster effectively brackets established lithium depletion boundary. candidates range in spectral type from M6 to M7, implying effective temperatures between ∼2800 2650 K. All sources exhibit Hα emission, consistent with enhanced...
Abstract We present the positions, proper motions, and near-infrared photometry for 966 known objects with spectral types later than M that were observed as part of UKIRT Hemisphere Survey (UHS). augment astrometry from UHS information Gaia DR3, Pan-STARRS DR2, CatWISE 2020 to produce a database homogeneous this sample. The multi-epoch survey strategy allows us determine motions most sources, median motion uncertainty ∼3.6 mas yr −1 . Our measurements are generally in good agreement those...
An Hα emission survey of the young cluster NGC 2264 in Mon OB1 association resulted detection 490 stars a 25' × 40' field approximately centered between O7 V multiple star S and Cone Nebula. The was carried out with wide-field grism spectrograph (WFGS) on University Hawaii 2.2 m telescope Mauna Kea. X-ray observations made European Photon Imaging Camera board Space Agency's XMM-Newton satellite observatory will be discussed subsequent paper. Optical (BVRCIC) photometry obtained for selected...
We present results from a mid-infrared imaging survey of the ∼5 Myr old cluster NGC 2362 carried out with Infrared Array Camera (IRAC) on board Spitzer Space Telescope. The archival data were merged extant Hα emission data, optical and near-infrared photometry, moderate-resolution spectroscopy to identify remnant disk-bearing population estimate fraction stars that still retain primordial circumstellar disks. principal sample 232 suspected members masses ranging ∼10 0.3 M⊙ (B2-M5 spectral...
High-resolution optical and moderate-resolution near-infrared spectra were obtained for 40 near solar mass (∼2.0–0.5 M☉) members of the 2–3 Myr old cluster IC 348 in order to examine established accretion diagnostics coupling between inner disk gas hot, micron-sized dust grains inferred from thermal mid-infrared excesses. The stellar sample was drawn census Luhman 2003 with membership being confirmed by radial velocity analysis presence strong Li i λ6708 absorption. Of stars included this...
We present preliminary trigonometric parallaxes of 184 late-T and Y dwarfs using observations from Spitzer (143), USNO (18), NTT (14), UKIRT (9). To complete the 20-pc census $\ge$T6 dwarfs, we combine these measurements with previously published for an additional 44 objects spectrophotometric distance estimates another 7. For 235 objects, estimate temperatures, sift into five 150K-wide $T_{\rm eff}$ bins covering range 300-1050K, determine completeness limit each, compute space densities....
We present the discovery of CWISE J050626.96$+$073842.4 (CWISE J0506$+$0738), an L/T transition dwarf with extremely red near-infrared colors discovered through Backyard Worlds: Planet 9 citizen science project. Photometry from UKIRT and CatWISE give a $(J-K)_{\rm MKO}$ color 2.97$\pm$0.03 mag $J_{\rm MKO}-$W2 4.93$\pm$0.02 mag, making J0506$+$0738 reddest known free-floating in both colors. confirm nature using Keck/NIRES spectroscopy establish that it is low-gravity late-type dwarf. The...
Abstract Accretion plays a central role in the physics that governs evolution and dispersal of protoplanetary disks. The primary goal this paper is to analyze stability over time mass accretion rate onto TW Hya, nearest accreting solar-mass young star. We measure veiling across optical spectrum 1169 archival high-resolution spectra obtained from 1998–2022. then converted using 26 flux-calibrated cover Balmer jump. measured excess continuum has an average 2.51 × 10 −9 M ⊙ yr −1 Gaussian...
We present the results of a high-resolution imaging survey for brown dwarf (BD) binaries in two open clusters. The observations were carried out with WFPC2 onboard HST. Our sample consists 8 BD candidates alpha Per cluster and 25 Pleiades. have resolved 4 Pleiades separations range 0".094--0".058, corresponding to projected between 11.7~AU 7.2~AU. No found among targets. Three proper motions consistent membership cluster, one them we report detection Halpha emission LiI absorption obtained...
We present projected rotational velocities for 20 early-type (B8-A9) and 74 late-type (F2-M8) members of the ~5 Myr old Upper Scorpius OB Association derived from high dispersion optical spectra obtained with High Resolution Echelle Spectrometer (HIRES) on Keck I Magellan Inamori Kyocera (MIKE) Clay telescope. The spectroscopic sample is composed stars brown dwarfs infrared signatures circumstellar disks, both primordial debris, non-excess sources comparable spectral type. merge velocities,...
We present mid-infrared spectra between 5.2 and 38 μm for 26 disk-bearing members of the ∼5 Myr old Upper Scorpius OB association obtained with Infrared Spectrograph (IRS) onboard Spitzer Space Telescope. find clear evidence changes in spectral characteristics dust emission early-type (B+A) late-type (K+M) infrared excess stars. The exhibit featureless continuum excesses that become apparent redward ∼8 μm. In contrast, 10 20 silicate features or polycyclic aromatic hydrocarbon are all but...
An Hα emission survey of the young cluster NGC 2362 resulted in detection 130 stars an 11' × field approximately centered on fourth magnitude O9 Ib multiple star τ CMa. The was carried out using wide-field grism spectrograph University Hawaii 2.2 m telescope and Gemini Multi-Object Spectrograph (GMOS) North. Deep optical VRCIC (to V ∼ 23.0) near-infrared (NIR) photometry (JHK) to K 16 were obtained for several fields within cluster. Spectra covering 6000–8000 Å region at a resolution R 3000...
We present results from an X-ray imaging survey of the young cluster NGC 2264, carried out with European Photon Imaging Cameras (EPIC) on board XMM-Newton spacecraft. The data are merged extant optical and near-infrared photometry, spectral classifications, Hα emission strengths, rotation periods to examine interrelationships between coronal chromospheric activity, rotation, stellar mass, internal structure for a statistically significant sample pre-main-sequence stars. A total 300 distinct...
We present Keck/NIRC2 Ks-band high-contrast coronagraphic imaging of the luminous debris disk around nearby, young A star HD 32297 resolved at a projected separation r = 03–25 (≈35–280 AU). The is highly warped to north and exhibits complex, "wavy" surface brightness (SB) profile interior ≈ 110 AU, where peaks/plateaus in profiles are shifted between NE SW lobes. side 50%–100% brighter 35–80 location its peak roughly coincides with disk's millimeter (mm) emission peak. Spectral energy...
The B0 V star BD +46°3474 lies near the front surface of a dense molecular cloud and illuminates emission/reflection nebula IC 5146. HAeBe variable +46°3471 is embedded in same cloud, about 10' (3.5 pc) away. CCD photometry BVRI (to = 22) JHK K 16.5) has been obtained for young clusters surrounding each these two bright stars. Some 100 emission-Hα stars brighter than R 20.5 have found area, most them (Among are that spectra resembling high-excitation Herbig-Haro [HH] object plus stellar...
The central region of the dark cloud L1482 is illuminated by LkHα 101, a heavily reddened (AV ≈ 10 mag) high-luminosity (≥8 × 103 L⊙) star having an unusual emission-line spectrum plus featureless continuum. About 35 much fainter (mostly between R = 16 and >21) Hα emitters have been found in cloud. Their color-magnitude distribution suggests median age about 0.5 Myr, with considerable dispersion. There are also at least five bright B-type stars cloud, presumably same age; none show...
Abstract We present a microlensing analysis of updated light curves in three filters, the g -band, r and H for gravitationally lensed quasars Q0957+561 SBS0909+532. Both systems display prominent features which we analyze using our Bayesian Monte Carlo technique to constrain quasar continuum emission region sizes each band. report as half-light radii scaled 60° inclination angle. For measure <?CDATA $\mathrm{log}({r}_{1/2}/\mathrm{cm})={16.54}_{-0.33}^{+0.33}$?> , ${16.66}_{-0.62}^{+0.37}$?>...
We present Keck II adaptive optics near infrared imaging and spectroscopic observations of the central regions powerful radio galaxy Cygnus A. The 0.05" resolution images clearly show an unresolved nucleus between two spectacular ionization/scattering cones. report discovery a relatively bright (K'~19) secondary point source 0.4" or 400 pc in projection southwest nucleus. object is also visible archival Hubble Space Telescope optical images, although it easily confused with underlying...
L988 is a large (∼05 × 07) dark cloud complex at about 600 pc that contains several bright pre-main-sequence objects (such as V1331 Cyg and LkHα 321), but this paper deals in detail only with small region on its eastern edge, near the HAeBe star 324. That distant companion 324SE lie apex of V-shaped area apparently excavated from edge L988, are brightest members cluster containing 50 Hα-emission stars. A median age 0.6 Myr (with dispersion) inferred color-magnitude diagram, constructed VRI...
NGC 2264 is a young Galactic cluster and the dominant component of Mon OB1 association lying approximately 760 pc distant within local spiral arm. The hierarchically structured, with subclusters suspected members spread across several parsecs. Associated an extensive molecular cloud complex spanning more than two degrees on sky. Star formation ongoing region as evidenced by presence numerous embedded clusters protostars, outflows, Herbig-Haro objects. stellar population dominated O7 V...
An H2 emission filament is found in close proximity to the unique object KH 15D using adaptive optics system of Subaru Telescope. The morphology filament, presence spectroscopic outflow signatures observed by Hamilton et al., and detection extended from Deming, Charbonneau, & Harrington suggest that this arises shocked an outflow. extends about 15'' north 15D.
Abstract We analyze variability in 15-season optical lightcurves from the doubly imaged lensed quasar SDSS J165043.44+425149.3 (SDSS1650), comprising five seasons of monitoring data Maidanak Observatory (277 nights total, including two previously presented Vuissoz et al.), overlapping Mercator telescope (269 nights), and 12 US Naval Observatory, Flagstaff Station at lower cadence (80 nights). update 2007 time-delay measurement for SDSS1650 with these new data, finding a time delay <?CDATA...