A5082969169- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomy and Astrophysical Research
- Adaptive optics and wavefront sensing
- Gamma-ray bursts and supernovae
- Calibration and Measurement Techniques
- Astrophysical Phenomena and Observations
- Optical Systems and Laser Technology
- Molecular Spectroscopy and Structure
- Astronomical Observations and Instrumentation
- Spacecraft Design and Technology
- Planetary Science and Exploration
- Advanced optical system design
- Geomagnetism and Paleomagnetism Studies
- Atmospheric Ozone and Climate
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Optical Polarization and Ellipsometry
- Spectroscopy and Laser Applications
- Infrared Target Detection Methodologies
- Optical Wireless Communication Technologies
- Semiconductor Lasers and Optical Devices
- Hydrocarbon exploration and reservoir analysis
- Fluid Dynamics and Turbulent Flows
University of Hawaii–West Oahu
2016-2024
University of Hawaii System
2001-2024
University of Hawaii at Hilo
2013-2024
University of Hawaiʻi at Mānoa
2010-2024
Monterey Institute for Research in Astronomy
2002-2022
Canada–France–Hawaii Telescope
2018
Ames Research Center
2007-2010
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 results of a near-IR spectroscopic survey 110 Class I protostars observed from 0.80 μm to 2.43 at resolution R = 1200. This is unique in its selection targets whole sky, sample size, wavelength coverage, depth, and selection. find that objects exhibit wide range lines continuum features. Eighty-five percent features indicative mass accretion, we found veiling excess, CO emission, Br γ emission are closely related. modeled spectra estimate excess (rk) extinction each target....
We have conducted a homogenous near-IR spectroscopic survey of 33 objects with varying degrees similarity to FU~Orionis. Common features that are characteristic the three classical FUors FU Ori, V1057 Cyg, and V1515 Cyg are: strong CO absorption, weak metal water bands, low gravity, blue shifted He I few (if any) emission lines. Based on these criteria, we classify as either bona fide (eruption observed), FUor-like not or peculiar some characteristics, present spectral atlas 14 bona-fide...
We have carried out a major survey for visual binaries toward the Orion Nebula Cluster, using images obtained with Advanced Camera Surveys on Hubble Space Telescope through an Hα filter. From 1051 stars more than 60'' from θ1 Ori C, we selected 781 that fulfill criteria membership in Cluster. Among these, find 78 multiple systems (75 and 3 triples), of which 55 are new discoveries, range 0.1'' to 1.5''. perform statistical study 72 triples separations limited 0.15'' 1.5'', within need no...
We present the observational results of a near-infrared survey large sample Class I protostars designed to determine binary separation distribution from ∼100 AU ∼5000 AU. have selected targets new 267 nearby candidate objects. This is well understood, consists mostly young stellar objects (YSOs) within 1 kpc, has whole sky, and not biased by previous studies star formation. observed 189 YSOs north δ = −40° at H, K, L' bands, with median angular resolution 033 L'. our detection limit for...
iSHELL is 1.10-5.3 μm high spectral resolution spectrograph being built for the NASA Infrared Telescope Facility on Maunakea, Hawaii. Dispersion accomplished with a silicon immersion grating in order to keep instrument small enough be mounted at Cassegrain focus of telescope. The white pupil produces resolving powers up R=75,000. Cross-dispersing gratings tilt-able mechanism allow observers select different wavelength ranges and, combination slit wheel and Dekker mechanism, lengths ranging...
Abstract iSHELL is a 1.06–5.3 μ m high spectral resolution spectrograph built for the 3.2 NASA Infrared Telescope Facility (IRTF) on Maunakea, Hawaii. Dispersion accomplished with silicon immersion grating in order to keep instrument small enough be mounted at Cassegrain focus of telescope. The white pupil produces resolving powers up about R ≡ λ / δλ = 80,000 (0.″375 slit). Cross-dispersing gratings tiltable mechanism allow observers select different wavelength ranges and, combination slit...
We present the Class I protostellar binary separation distribution based on data tabulated in a companion paper. verify excess of stars over solar-type main-sequence range from 500 AU to 4500 AU. Although our sources are nearby star-forming regions distributed across entire sky (including Orion), none objects high stellar density environment. A log–normal function, used by previous authors fit and T Tauri distributions, poorly fits data, we determine that log–uniform function is better fit....
Magnetic fields and mass accretion processes create dark bright spots on the surface of young stars. These manifest as thermal inhomogeneities, which alter global temperature measured To understand effects implications these starspots, we conducted a large iSHELL high-resolution infrared spectroscopic survey T Tauri stars in Taurus-Auriga Ophiuchus star-forming regions. From K band spectra, stellar temperatures magnetic field strengths using radiative transfer code. We compared our...
We present a K-band atlas of 106 reflection nebulae, 41 which are new discoveries. observed these nebulae with the University Hawaii 2.2 m telescope in course an imaging survey 197 objects that were selected as nearby young Class I sources. images and flux-calibrated surface brightness contour plots each nebula presented. found near-IR luminosities physical sizes increase bolometric luminosity illuminating Only 22 about 10% candidate sources, have indications shocked H2 emission. The great...
We explore the origin of a population distant companions (∼1000–5000 AU) to Class I protostellar sources recently found by Connelley and coworkers, who noted that companion fraction diminished as evolved. Here, we present N-body simulations unstable triple systems embedded in dense cloud cores. Many are ejected into unbound orbits quickly escape, but others with insufficient momentum climb out potential well core associated binary. These loosely bound reach distances many thousands AU before...
We study the evolution of FU Ori object V960 Mon since its outburst, using available multi-wavelength photometric time series over 8 years, complemented by several epochs moderate-dispersion spectrophotometry. find that source fading can be well-described a decrease in temperature inner disk, which results from combination decreasing accretion rate and increasing disk radius. model system with atmosphere produces observed variations multi-band photometry (this paper) high resolution spectral...
Abstract We report on the source Gaia 19ajj, identifying it as a young star associated with little-studied star-forming region seen along complex line of sight through Gum Nebula. The optical lightcurve recently recorded by exhibits slow and unsteady 5.5 mag rise over about 3 yr, while mid-infrared from NEOWISE same time period shows 1.2 having similar structure. Available color information is inconsistent pure extinction reduction cause for photometric brightening. Optical spectroscopic...
Outbursts on young stars are usually interpreted as accretion bursts caused by instabilities in the disk or star-disk connection. However, some protostellar outbursts may not fit into this framework. In paper, we analyze optical and near-infrared spectra photometry to characterize 2015 outburst of probable star ASASSN-15qi. The $\sim 3.5$ mag brightening $V$ band was sudden, with an unresolved rise time less than one day. decayed exponentially 1 for 6 days then gradually back pre-outburst...
We report photometry and spectroscopy of the outburst young stellar object ESO-Halpha 99. The was first noticed in Gaia alert Gaia18dvc later by ATLAS. have established light curve with archival ATLAS ``Orange'' filter photometry, data, new V-band J, H, K_s from IRIS UKIRT. brightness has fluctuated several times near maximum. TESS satellite observed 99 high cadence during one these minor minima found fluctuations on timescales days hours. Imaging UKIRT shows outline an outflow cavity, we...
We present high-resolution $^{12}$CO and $^{13}$CO 2-1 ALMA observations, as well optical near-infrared spectroscopy, of the highly-inclined protoplanetary disk around SSTC2D J163131.2-242627. The spectral type we derive for source is consistent with a $\rm 1.2 \, M_{\odot}$ star inferred from observations. Despite its massive circumstellar disk, find little to no evidence ongoing accretion on star. CO maps reveal that unusually compact along vertical direction, appearance in scattered light...
ABSTRACT V1741 Sgr (= SPICY 71482/Gaia22dtk) is a Classical T Tauri star on the outskirts of Lagoon Nebula. After at least decade stability, in mid-2022, optical source brightened by ∼3 mag over 2 months, remained bright until early 2023, then dimmed erratically next 4 months. This event was monitored with and infrared spectroscopy photometry. Spectra from peak (October 2022) indicate an EX Lup-type (EXor) accretion outburst, strong emission H i, He Ca ii lines CO bands. At this stage,...
TNO and partners at University of Hawai'i (UH), the NASA InfraRed Telescope Facility (IRTF), Center for Adaptive Optics (CfAO) UCSC have been working on realization a 244 mm Secondary Mirror (ASM) IRTF called IRTF-ASM-1. After successful performance testing several laboratory prototypes, this project provided first on-sky demonstration TNO's ASM technology M2 location with an optically powered mirror shell. <br/> <br clear="all"/> The is designed to retrofit current passive M2. consists...
Persson recently found that a faint star had appeared in cloud Cepheus. A CCD image shows R ∼ 17.3 nebulous star, now known as V733 Cep, located the L1216 = Cep F at apex of cavity cloud. Infrared photometry indicates modest infrared excess. Optical spectroscopy well-defined Li I λ6707 line, and blueshifted absorption troughs Hα Na D lines extending to least 200 km s-1, indicative massive fast wind. An 1-4 μm spectrum presence strong water vapor features, is almost identical similar IR FU...
Abstract We report photometry and spectroscopy of the outburst young stellar object Gaia19bey. have established light curve with archival Gaia “ G ,” ATLAS “Orange,” Zwicky Transient Facility r -band, Pan-STARRS rizy ”-filter photometry, showing an ~4 yr duration, longer than typical EX Lupi objects but shorter FU Orionis objects. Its pre-outburst spectral energy distribution shows a flat far-infrared spectrum, confirming early evolutionary state Gaia19bey its similarity to other deeply...
In order to test the hypothesis that Class I protostellar binary stars are a product of ejections during dynamical decay nonhierarchical multiple systems, we combined results new adaptive optics (AO) observations protostars with our previously published AO data investigate whether widely separated companion (r > 200 AU) more likely also have close < AU). total, observed 47 embedded young stellar objects (YSOs) either Subaru natural guide star system or Keck laser system. We found targets...
We present the results of a program that monitored near-IR spectroscopic variability sample 19 embedded protostars. Spectra were taken on time intervals from 2 days to 3 yr, over wavelength range 0.85 μm 2.45 μm, for 4–9 epochs observations per target. found spectra all targets are variable and every emission feature observed is also (although not targets). With one exception, there no drastic changes in continua spectra, nor did any line completely disappear, appear was previously apparent....
Context: L-type ultra-cool dwarfs and brown have cloudy atmospheres that could host weather-like phenomena. The detection of photometric or spectral variability would provide insight into unresolved atmospheric heterogeneities, such as holes in a global cloud deck. Aims: It has been proposed growth heterogeneities the deck may account for L- to T-type transition dwarf photospheres evolve from clear conditions. Such mechanism is compatible with variability. We searched spectra five L6 T6...