A5009594222- Astrophysical Phenomena and Observations
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Astronomical Observations and Instrumentation
- High-pressure geophysics and materials
- Fluid Dynamics Simulations and Interactions
- Solar and Space Plasma Dynamics
- Particle accelerators and beam dynamics
- Superconducting Materials and Applications
- Granular flow and fluidized beds
- Particle Accelerators and Free-Electron Lasers
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Astrophysics and Cosmic Phenomena
- Innovations in Educational Methods
- Planetary Science and Exploration
- Isotope Analysis in Ecology
- Distributed and Parallel Computing Systems
- Leaf Properties and Growth Measurement
- Fluid Dynamics and Heat Transfer
- Teaching and Learning Programming
University of Central Florida
2008-2018
Union astronomique internationale
2015
Centro de Astrobiología
2010
Florida Institute of Technology
2000-2001
University of Alabama in Huntsville
1998
ABSTRACT In this brief communication we provide the rationale for and outcome of International Astronomical Union (IAU) resolution vote at XXIXth General Assembly in Honolulu, Hawaii, 2015, on recommended nominal conversion constants selected solar planetary properties. The problem addressed by is a lack established between values SI units: missing standard has caused proliferation (e.g., radius, irradiance, luminosity, effective temperature, mass parameter) literature, with cited typically...
Astronomers commonly quote the properties of celestial objects in units parameters for Sun, Jupiter, or Earth. The resolution presented here was proposed by IAU Inter-Division Working Group on Nominal Units Stellar and Planetary Astronomy passed XXIXth General Assembly Honolulu. 2015 Resolution B3 adopts a set nominal solar, terrestrial, jovian conversion constants stellar (exo)planetary astronomy which are defined to be exact SI values. While based current best estimates (CBEs; have...
The volatile abundances in comet 17P/Holmes were measured on three dates (UT 2007 October 27.6 and 31.3 November 2.3) using high-dispersion (λ/Δ λ ∼ 2.5 × 104) infrared spectroscopy with NIRSPEC at the W. M. Keck Observatory CSHELL NASA Infrared Telescope Facility. Compared to other comets, relative gas production rates coma show an enhancement of C2H6, HCN, C2H2 respect H2O, by factors ~2-3. CH3OH was also detected abundance H2O that is similar or perhaps slightly enhanced compared values...
We present observations of 36 late-M dwarfs obtained with the KeckII/NIRSPEC in J-band at a resolution \sim20,000. have measured projected rotational velocities, absolute radial and pseudo-equivalent widths atomic lines. 12 our targets did not previous measurements literature. For other 24 targets, we confirm previously reported measurements. find that 13 stars from sample vsini below measurement threshold (12 km/s) whereas four are fast rotators (vsini > 30 km/s). As rotation causes...
The XXIXth IAU General Assembly in Honolulu adopted 2015 Resolution B2 on recommended zero points for the absolute and apparent bolometric magnitude scales. resolution was proposed by Inter-Division A-G Working Group Nominal Units Stellar Planetary Astronomy after consulting with a broad spectrum of researchers from astronomical community. resolves long-standing absence an internationally-adopted point defines scale such that radiation source $M_{\rm Bol}$ = 0 has luminosity L$_{\circ}$...
Accretion disks around black hole, neutron star, and white dwarf systems are thought to sometimes tilt, retrogradely precess, produce hump-shaped modulations in light curves that have a period shorter than the orbital period. Although artificially rotating numerically simulated accretion out of plane line nodes generates these short-period superhumps retrograde precession disk, no numerical code date has been shown disk tilt naturally. In this work, we report first naturally tilted...
In recent years, a handful of systems have been observed to show "negative" (nodal) superhumps, with periods slightly shorter than the orbital period. It has suggested that these modes are consequence slow retrograde precession line nodes in disk tilted respect plane. Our simulations confirm and refine this model: they suggest roughly axisymmetric, retrogradely precessing, is driven at period less half as tidal field orbiting secondary encounters, turn, two halves above below midplane. Each...
We present radial velocities of the M8V-type, very low-mass star vB 10 obtained at four different epochs between 2001 and 2008. use high-resolution (<i>R<i/> ~ 20 000) near-infrared (<i>J<i/>-band) spectra taken with nirspec instrument on Keck II telescope. Our data suggest that shows velocity variability an amplitude ~1 km s<sup>-1<sup/>, a result is consistent recent finding massive planet companion around star. More measurements better sampling orbital phase are required to precisely...
Using smoothed particle hydrodynamics, we numerically simulate steady-state accretion discs for cataclysmic variable dwarf novae systems that have a secondary-to-primary mass ratio 0.35 ≤q≤ 0.55. After these come to quasi-equilibrium, rotate each disc out of the orbital plane by δ= (1, 2, 3, 4, 5 or 20)° induce negative superhumps. For tilted 5°, generate light curves and associated Fourier transforms an atlas on superhumps retrograde precession. Our simulation results suggest need be more...
Many different system types retrogradely precess, and retrograde precession could be from a tidal torque by the secondary on misaligned accretion disk. However, source that causes maintains disk tilt is unknown. In this work, we show disks can due to force called lift. Lift results differing gas stream supersonic speeds over under an Because lift acts at disk's center of pressure, applied around rotation axis passing through mass. The responds pitching line nodes. If flow ebbs, then also...
Net tidal torque by the secondary on a misaligned accretion disk, like net Moon and Sun equatorial bulge of spinning tilted Earth, is suggested others to be source retrograde precession in non-magnetic, accreting cataclysmic variable (CV) dwarf novae (DN) systems that show negative superhumps their light curves. We investigate this idea work. generate generic theoretical expression for disks are with orbital plane. Our matches which describes Earths' equinoxes. By making appropriate...
Warps are suspected in disks around massive compact objects. However, the proposed warping source -- non-axisymmetric radiation pressure does not apply to white dwarfs. In this letter we report first Smoothed Particle Hydrodynamic simulations of accretion SU UMa-type systems that naturally tilt, warp, and simultaneously precess prograde retrograde directions using dwarf V344 Lyrae Kepler field as our model. After ~79 days Lyrae, disk angular momentum L_d becomes misaligned orbital L_o. As...
Context. Radial velocity (RV) measurements from near-infrared spectra have become a potentially powerful tool to search for planets around cool stars and sub-stellar objects. As part of large survey characterize M-dwarfs using NIRSPEC at Keck II, we obtained eight late (spectral types M5.0-M8.0) during two or more observing epochs per target. These were taken with intermediate spectral resolving powers (R \sim 20,000) in the J-band. Aims. We relative radial variability these test capability...
We compare analytical expressions of precession rates from apsidal (positive) superhumps in close binary systems with numerical disc simulation results and observed values. In the expressions, we include both dynamical effects on caused by pressure forces that have been theorized to provide a retrograde effect (i.e. slowing) prograde precession. establish new limits density wave pitch angle normalized sound speed 60≥Ωorb d tan i/c>2.214. Using average values for i c, find good correlation...
Using the low-resolution mode of Space Telescope Imaging Spectrograph (STIS) aboard \emph{Hubble Telescope} (HST), we have obtained spatially resolved spectra 20 ultracool dwarfs. 18 them belong to 9 known very low-mass binary systems with angular separations in range 0.37-0.098 arcseconds. We derived spectral types dM7.5 dL6 from PC3 index, and by comparing our STIS ground-based similar resolution Mart{\'\i}n et al. (1999). searched for H$_\alpha$ emission each object but it was clearly...
In a recent work by the first author, we show that accretion discs in binary systems could retrogradely precess same physics causes Earth to [i.e. tidal torques Moon and Sun (or secondary star) on tilted, spinning, non-spherical e.g. primary star surrounded an disc)]. addition, state of matter geometrical shape celestial object significantly affect precessional value. For example, cataclysmic variable (CV) dwarf novae (DN) non-magnetic system shows negative superhumps its light curve can be...
Using a one-dimensional time-dependent numerical hydrodynamic model, we examine the response of solar atmosphere to heating by beam energetic protons with characteristic energy near 1 MeV. At these energies, coronal portion flaring loop must be treated as "warm" target, while chromospheric behaves "cold" target. This results in more uniform portions than is case electrons, leading smaller pressure gradients and lower plasma upflow velocities. Such velocities would appear at first consistent...
Distributed virtual environment simulators such as OpenSimulator and SecondLife have become popular over the last decade. However, these pose a greater challenge with increased load due to High-Fidelity of simulations, higher number objects agents, levels interactions. In this paper we propose framework for distributed simulator research on high performance computing (HPC) clusters. Our proposed would be very useful world researchers HPC clusters are more freely available compared setting up...
In a recent publication, we introduce the lift force as common source to accretion disk tilt that is likely relevant systems. Lift generated by slightly different supersonic gas stream speeds flowing over and under at bright spot. this conference proceeding, focus on whether average white dwarf has enough mass prevent in non-magnetic Cataclysmic Variables (CVs) with disks. Assuming of 0.6M$_{\odot}$ 10$^{-11}$M$_{\odot}$, vary secondary establish theoretical minimum transfer rates needed...