A5007235075- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Pulsars and Gravitational Waves Research
- Adaptive optics and wavefront sensing
- History and Developments in Astronomy
- Astrophysics and Cosmic Phenomena
- Particle Accelerators and Free-Electron Lasers
- Laser-Plasma Interactions and Diagnostics
- High-pressure geophysics and materials
- Solar and Space Plasma Dynamics
- Planetary Science and Exploration
- Radio Astronomy Observations and Technology
- Photocathodes and Microchannel Plates
- Geophysics and Gravity Measurements
- Calibration and Measurement Techniques
- Quantum Chromodynamics and Particle Interactions
- Historical Astronomy and Related Studies
- CCD and CMOS Imaging Sensors
- Cosmology and Gravitation Theories
American Museum of Natural History
2016-2025
University of Cambridge
2017-2022
European Southern Observatory
2018
University of Valparaíso
2018
University of Canterbury
2018
Centro de Estudios de Física del Cosmos de Aragón
2018
University of Hawaii System
2011-2014
U.S. National Science Foundation
2003-2012
Kitt Peak National Observatory
2012
Association of Universities For Research In Astronomy
1997-2012
The Palomar Transient Factory (PTF) is a fully-automated, wide-field survey aimed at systematic exploration of the optical transient sky. performed using new 8.1 square degree camera installed on 48-inch Samuel Oschin telescope Observatory; colors and light curves for detected transients are obtained with automated 60-inch telescope. PTF uses eighty percent 1.2-m fifty 1.5-m time. With an exposure 60-s reaches depth approximately 21.3 in g' 20.6 R (5 sigma, median seeing). Four major...
The Palomar Transient Factory (PTF) is a wide-field experiment designed to investigate the optical transient and variable sky on time scales from minutes years. PTF uses CFH12k mosaic camera, with field of view 7.9 deg2 plate scale 1'' pixel-1, mounted Observatory 48 inch Samuel Oschin Telescope. operation strategy devised probe existing gaps in phase space search for theoretically predicted, but not yet detected, phenomena, such as fallback supernovae, macronovae,. Ia orphan afterglows...
A simple method to predict the densities of a range ionic liquids from their surface tensions, and vice versa, using surface-tension-weighted molar volume, parachor, is reported. The parachors containing 1-alkyl-3-methylimidazolium cations were determined experimentally, but also calculated directly structural compositions existing parachor contribution data for neutral compounds. experimentally remarkably similar, latter subsequently employed tensions investigated liquids. Using similar...
The LSPM-north catalog is a comprehensive list of 61,977 stars north the J2000 celestial equator that have proper motions larger than 0.15 seconds arc per year (local-background-stars frame). has been generated primarily as result our systematic search for high motion in Digitized Sky Surveys using SUPERBLINK software. At brighter magnitudes, incorporates and data from Tycho-2 Catalogue also, to lesser extent, All-sky Compiled 2.5 million stars. LSPM expands considerably over old Luyten...
The Guide Star Catalog (GSC) has been constructed as support for the Hubble Space Telescope (HST) and contains about 19 million stars objects in sixth to fifteenth magnitude range. GSC is primarily based on an all-sky single-epoch collection Schmidt plates. program discussed detail, including HST program, astronomical objectives of error analysis. An overview image data underlying production software given. processing techniques are described, microdensitometers, photometric systems,...
This paper is a sequel to an earlier devoted multiple, multicycle nova evolution models (Prialnik & Kovetz, Paper I), which showed that the different characteristics of outbursts can be reproduced by varying values three basic and independent parameters: white dwarf mass, MWD, temperature its isothermal core, TWD, mass transfer rate, . Here we show parameter space constrained several analytical considerations find limiting surfaces. Consequently, extend grid presented in I limits, adding...
We report parallax measurements for 70 ultracool dwarfs (UCDs). Using both literature values and our sample, we new polynomial relations between spectral type M$_{JHK}$. Including resolved L/T transition binaries in the relations, find no reason to differentiate a "bright" (unresolved binary) "faint" (single source) sample across boundary. Isolating early T dwarfs, that brightening of T0-T4 sources is prominent M$_{J}$ where there [1.2 - 1.4] magnitude difference. A similar yet dampened [0.3...
The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in new era multi-messenger astronomy. In this paper, we present event GW170817 and its SSS17a/DLT17ck (IAU label AT2017gfo) 14 Australian telescopes partner observatories as part Australian-based Australian-led research programs. We report early- late-time multi-wavelength observations, including optical imaging spectroscopy,...
A survey of a sample 672 stars from the Yale Bright Star Catalog (Hoffleit, 1982) has been carried out using speckle interferometry on 3.6-cm Canada-France-Hawaii Telescope in order to establish binary star frequency within sample. This effort was motivated by need for more observationally determined basis predicting failure Hubble Space (HST) fine-guidance sensors achieve guide-star lock due duplicity. 426 dwarfs and 246 evolved yielded measurements 52 newly discovered binaries 60...
Speckle interferometric observations are reported for 1123 stars selected from the Yale Bright Star Catalogue (BSC) in a continuing effort to detect new binaries among bright stars. Thirty-two previously unresolved have been detected, including companions Xi UMa and 15 S Mon. Measures of 107 resolved systems, many which resulted earlier speckle observations, also presented. No evidence duplicity within specific (m, Delta-m, rho) window detectability was found 984 Many systems discovered...
Xi Ursae Majoris (HR 4374/5) consists of a visual binary having period nearly 60 yr, the primary component which is 669 day astrometric and spectroscopic subsystem, secondary 4 binary. We report here improved elements for long-period system (AB) short-period (Aa). also first direct detection fifth to multiple (Bc) from speckle observations obtained in 1988 at Canada-France-Hawaii Telescope.
The Catalog and Atlas of Cataclysmic Variables (Edition 1: Downes & Shara; Edition 2: Downes, Webbink, Shara) has been a valuable source information for the cataclysmic variable community. However, goal having central location all objects is slowly being lost as each new edition generated. There can also be long time delay between becoming available on an object its publication in catalog. To eliminate these concerns, well to make catalog more accessible, we have created Web site which will...
We present the white dwarf sequence of globular cluster M4, based on a 123 orbit Hubble Space Telescope exposure, with limiting magnitude V ~ 30 and I 28. The luminosity function rises sharply for > 25.5, consistent behavior expected burst population. dwarfs M4 extend to approximately 2.5 mag fainter than peak local Galactic disk function. This demonstrates clear significant age difference between halo M4. Using same standard models fit each yields ages 7.3 ± 1.5 Gyr 12.7 0.7 (2 σ...
view Abstract Citations (266) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Do Novae Hibernate during Most of the Millennia between Eruptions? Links Dwarf and Classical Novae, Implications for Space Densities Evolution Cataclysmic Binaries Shara, Michael M. ; Livio, Mario Moffat, Anthony F. J. Orio, Marina The space densities classical novae deduced from surveys in solar neighborhood are about two orders magnitude lower than those nova...
We present the results of a speckle interferometric survey for close visual companions, mainly among 29 apparently brightest Wolf-Rayet (W-R) stars. Only one target, WR 48 = θ Mus, was resolved as astrometric binary (with separation 46 ± 9 mas). This system is probably triple comprising short-period W-R plus distant O supergiant companion. Although our detection fraction low, it not an unexpected result given selection effects that militate against easy binaries. New, higher resolution...
We report proper motion measurements for 427 late-type M, L and T dwarfs, 332 of which have been measured the first time. Combining these new motions with previously published yields a sample 841 M7-T8 dwarfs. combined parallax or calculated spectrophotometric distances computed tangential velocities entire sample. find that kinematics full volume-limited 20 pc samples are consistent those expected Galactic thin disk, no significant differences between L, Applying an age-velocity relation we...
The current classification system of M stars on the main sequence distinguishes three metallicity classes (dwarfs: dM; subdwarfs: sdM; and extreme esdM). spectroscopic definition these is based relative strength prominent CaH TiO molecular absorption bands near 7000 Å, as quantified by indices (CaH2, CaH3, TiO5). boundaries between were initially defined from a relatively small sample only 79 metal-poor (subdwarfs subdwarfs). We re-examine this in light our ongoing survey with proper motion...
In the old, populous, and metal-rich open cluster NGC 6791 we have used deep HST/ACS images to track white dwarf cooling sequence down m_F606W~28.5. The luminosity function shows a well defined peak at m_F606W~27.4, bending blue in color--magnitude diagram. If this corresponds end of comparison with theoretical isochrones provides age estimate ~2.4 Gyr, sharp contrast 8--9 Gyr inferred from main-sequence turn-off. is fainter magnitudes, m_F606W~27.4 even more enigmatic. We discuss possible...
We present the results of a deep Hubble Space Telescope (HST) exposure nearby globular cluster NGC 6397, focussing attention on cluster's white dwarf cooling sequence. This sequence is shown to extend over 5 mag in depth, with an apparent cutoff at magnitude F814W ~ 27.6. demonstrate, using both artificial star tests and detectability background galaxies fainter magnitudes, that real represents truncation luminosity function this cluster. perform detailed comparison between models observed...
We present the spectroscopic evolution of AT 2017gfo, optical counterpart first binary neutron star (BNS) merger detected by LIGO and Virgo, GW170817. While models have long predicted that a BNS could produce kilonova (KN), we not been able to definitively test these until now. From one day four days after merger, took five spectra 2017gfo before it faded away, which was possible because at distance only 39.5 Mpc in galaxy NGC 4993. The evolve from blue ($\sim6400$K) red ($\sim3500$K) over...
On August 24 (UT) the Palomar Transient Factory (PTF) discovered PTF11kly (SN 2011fe), youngest and most nearby type Ia supernova Ia) in decades. We followed this event up radio (centimeter millimeter bands) X-ray bands, starting about a day after estimated explosion time. present our analysis of observations, yielding tightest constraints yet placed on pre-explosion mass-loss rate from progenitor system supernova. find robust limit dM/dt<10^-8 (w/100 km/s) [M_solar/yr] sensitive...
Can a white dwarf, accreting hydrogen-rich matter from non-degenerate companion star, ever exceed the Chandrasekhar mass and explode as type Ia supernova? We explore range of accretion rates that allow dwarf (WD) to secularly grow in mass, derive limits on rate initial will it reach $1.4M_\odot$ --- mass. follow evolution through long series hydrogen flashes, during which thick helium shell accumulates. This determines effective for long-term, self-consistent evolutionary runs with flashes....
Abstract Stellar evolution theory predicts multiple pathways to the explosive deaths of stars as supernovae. Locating and characterizing progenitors well-studied supernovae is important constrain justify design future surveys improve on progenitor detections. Here we report serendipitous preexplosion imaging, by Hubble Space Telescope, SN 2023ixf, one nearest extragalactic ever discovered, in galaxy M101. The extremely red color absolute magnitude <mml:math...
We report on nine wide common proper motion systems containing late-type M, L, or T companions. confirm six previously reported companions, and identify three new systems. The ages of these are determined using diagnostics for both stellar primaries low--mass secondaries masses the inferred evolutionary models. Of our discoveries, M3+T6.5 pair G 204-39 SDSS J1758+4633 has an age constrained to 0.5-1.5 Gyr making secondary a potentially useful brown dwarf benchmark. G5+L4 200-28 J1416+5006...