T. S. Axelrod
A5018967758- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Gamma-ray bursts and supernovae
- Adaptive optics and wavefront sensing
- Astrophysics and Star Formation Studies
- Astrophysical Phenomena and Observations
- Calibration and Measurement Techniques
- Distributed and Parallel Computing Systems
- Planetary Science and Exploration
- History and Developments in Astronomy
- Galaxies: Formation, Evolution, Phenomena
- Pulsars and Gravitational Waves Research
- Nuclear Physics and Applications
- Astrophysics and Cosmic Phenomena
- Scientific Research and Discoveries
- Dark Matter and Cosmic Phenomena
- Sensor Technology and Measurement Systems
- CCD and CMOS Imaging Sensors
- Optical Systems and Laser Technology
- Infrared Target Detection Methodologies
- Impact of Light on Environment and Health
- Atmospheric Ozone and Climate
- Isotope Analysis in Ecology
University of Arizona
2009-2023
Lawrence Livermore National Laboratory
1986-2017
Large Synoptic Survey Telescope Corporation
2015-2016
Optica
2014
Campbell Collaboration
1995-2009
Center for Astrophysics Harvard & Smithsonian
2004-2006
Institute of Astronomy and Astrophysics, Academia Sinica
2004
University of California, Berkeley
2004
Australian National University
1995-2003
Mount Stromlo Observatory
1995-2003
(Abridged) We describe here the most ambitious survey currently planned in optical, Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST have unique capability faint time domain. The design is driven four main themes: probing dark energy matter, taking an inventory Solar System, exploring transient optical sky, mapping Milky Way. wide-field ground-based system sited at Cerro Pach\'{o}n northern Chile. telescope 8.4 m...
A survey that can cover the sky in optical bands over wide fields to faint magnitudes with a fast cadence will enable many of exciting science opportunities next decade. The Large Synoptic Survey Telescope (LSST) have an effective aperture 6.7 meters and imaging camera field view 9.6 deg^2, be devoted ten-year 20,000 deg^2 south +15 deg. Each pointing imaged 2000 times fifteen second exposures six broad from 0.35 1.1 microns, total point-source depth r~27.5. LSST Science Book describes basic...
We report on our search for microlensing towards the Large Magellanic Cloud (LMC). Analysis of 5.7 years photometry 11.9 million stars in LMC reveals 13 - 17 events. This is significantly more than $\sim$ 2 to 4 events expected from lensing by known stellar populations. The timescales ($\that$) range 34 230 days. estimate optical depth with $2 < \that 400$ days be 1.2 ^{+0.4}_ {-0.3} \ten{-7}$, an additional 20% 30% systematic error. spatial distribution mildly inconsistent LMC/LMC disk...
The MACHO Project is a search for dark matter in the form of massive compact halo objects (MACHOs). Photometric monitoring millions stars Large Magellanic Cloud (LMC), Small (SMC), and Galactic bulge used to gravitational microlensing events caused by these otherwise invisible objects. Analysis first 2.1 yr photometry 8.5 million LMC reveals eight candidate events. This substantially more than number expected (~1.1) from lensing known stellar populations. timescales (t) range 34 145 days. We...
We present a measurement of the systemic proper motion Large Magellanic Cloud (LMC) from astrometry with High Resolution Camera (HRC) Advanced for Surveys (ACS) on Hubble Space Telescope (HST). observed LMC fields centered 21 background QSOs that were discovered their optical variability in MACHO database. The are distributed homogeneously behind central few degrees LMC. With 2 epochs HRC data and ~2 year baseline we determine to better than 5% accuracy: mu_W = -2.03 +/- 0.08 mas/yr; mu_N...
We present multicolor optical and two-frequency radio observations of the bright BeppoSAX event GRB 990510. Neither well-sampled decay nor are consistent with simple spherical afterglow models. The achromatic steepening in band early afterglow, which both occur at t ~ 1 day, evidence for hydrodynamical evolution source can be most easily interpreted by models gamma-ray burst ejecta collimated a jet. Employing jet model to explain observations, we derive opening angle θ0 = 0.08(n/1 cm-3)1/8,...
The Large Synoptic Survey Telescope (LSST) is a large-aperture, wide-field, ground-based survey system that will image the sky in six optical bands from 320 to 1050 nm, uniformly covering approximately $18,000$deg$^2$ of over 800 times. LSST currently under construction on Cerro Pachón Chile, and expected enter operations 2022. Once operational, explore wide range astrophysical questions, discovering "killer" asteroids examining nature Dark Energy. generate average 15 TB data per night,...
The unprecedented volume and rate of transient events that will be discovered by the Large Synoptic Survey Telescope (LSST) demands astronomical community update its followup paradigm. Alert-brokers -- automated software system to sift through, characterize, annotate prioritize for critical tools managing alert streams in LSST era. Arizona-NOAO Temporal Analysis Response Events System (ANTARES) is one such broker. In this work, we develop a machine learning pipeline characterize classify...
We report on a search for long duration microlensing events towards the Large Magellanic Cloud. find none, and therefore put limits contribution of high mass objects to Galactic dark matter. At 95% confidence level we exclude in range 0.3 solar masses 30.0 from contributing more than 4 times 10^11 halo. Combined with earlier results, this means that under 30 cannot make up entire matter halo if is typical size. For halo, 10 contribute less 40%
view Abstract Citations (206) References (56) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The MACHO Project First-Year Large Magellanic Cloud Results: Microlensing Rate and the Nature of Galactic Dark Halo Alcock, C. ; Allsman, R. A. Axelrod, T. S. Bennett, D. P. Cook, K. H. Freeman, Griest, Guern, J. Lehner, M. Marshall, L. Park, -S. Perlmutter, Peterson, B. Pratt, Quinn, Rodgers, W. Stubbs, Sutherland, Since July 1992, project has been carrying out...
Using observations from an extensive monitoring campaign with the Hubble Space Telescope, we present detection of intermediate-time flux excess that is redder in color relative to afterglow GRB 011121, currently distinguished as gamma-ray burst lowest known redshift. The red "bump," which exhibits a spectral rollover at ~7200 Å, well described by redshifted Type Ic supernova occurred approximately same time event. inferred luminosity about half bright SN 1998bw. These results serve...
We present analysis of MACHO Alert 95-30, a dramatic gravitational microlensing event toward the Galactic bulge whose peak magnification departs significantly from standard point-source model. 95-30 was observed in real time by Global Microlensing Network (GMAN), which obtained densely sampled photometric and spectroscopic data throughout event. interpret light-curve "fine structure" as indicating transit lens across extended face source star. This signifies resolution star several...
We have monitored 8.6 million stars in the Large Magellanic Cloud for 1.1 years and found 3 events consistent with gravitational microlensing. place strong constraints on Galactic halo content form of compact lensing objects mass range $10^{-4} \msun$ to $10^{-1} \msun$. Three is fewer than expected a standard spherical this range, but appears exceed number from known populations. Fitting naive model our data yields MACHO fraction $f = 0.20^{+0.33}_{-0.14}$, which implies total (inside 50...
Using 7 years of MACHO survey data, we present a new determination the optical depth to microlensing towards Galactic bulge. We select sample 62 events (60 unique) on clump giant sources and perform detailed efficiency analysis. use only because these are bright bulge stars not as strongly affected by blending other events. subsample 42 concentrated in just 4.5 square degrees, find tau = 2.17^{+0.47}_{-0.38} x 10^{-6} at (l,b) (1.50, -2.68), somewhat smaller than found most previous studies,...
The LSST Data Management System is built on an open source software framework that has middleware and application layers. layer provides capabilities to construct, configure, and manage pipelines on clusters of processing nodes, the data consume produce. It not in any way specific to astronomical applications. complementary application building blocks for constructing pipelines process data, both image catalog forms. does directly depend upon middleware, can readily be used with other...
The MACHO Project is a microlensing survey that monitors the brightnesses of ∼60 million stars in Large Magellanic Cloud (LMC), Small Cloud, and Galactic bulge. Our database presently contains about 80 billion photometric measurements, significant fraction all astronomical photometry. We describe calibration two‐color photometry transformation to standard Kron‐Cousins V R system. Calibrated may be properly compared with other observations on system, enhancing astrophysical value these data....
We present an analysis of the longest timescale microlensing events discovered by MACHO Collaboration during a 7 year survey Galactic bulge. find 6 that exhibit very strong parallax signals due, in part, to accurate photometric data from GMAN and MPS collaborations. The fit parameters are used likelihood analysis, which is able estimate distance masses lens objects based upon standard model velocity distribution. This indicates most likely 5 lenses > 1 Msun, suggests substantial fraction...
GRB 000926 has one of the best-studied afterglows to date, with multiple X-ray observations, as well extensive multifrequency optical and radio coverage. Broadband afterglow spanning from frequencies, provide a probe density structure circumburst medium, ejecta energetics, geometry, physical parameters relativistic blast wave resulting explosion. We present an analysis Chandra X-Ray Observatory observations this event, along Hubble Space Telescope monitoring data. combine these data...
More than 1300 variables classified provisionally as first-overtone RR Lyrae pulsators in the MACHO variable-star database of Large Magellanic Cloud (LMC) have been subjected to standard frequency analysis. Based on remnant power prewhitened spectra, we found 70% total population be monoperiodic. The remaining 30% (411 stars) are one nine types according their spectra. Several pulsational behavior clearly identified here for first time. Together with earlier discovered double-mode...
We fit the data for binary lens microlensing event MACHO 98-SMC-1 from five different collaborations and find two distinct solutions characterized by separation d mass ratio q: (d,q) = (0.54,0.50) (3.65,0.36), where is in units of Einstein radius. However, relative proper motion very similar solutions, 1.30 km s-1 kpc-1 1.48 kpc-1, thus confirming that Small Magellanic Cloud. The close can be either rotating or approximately static but wide must at to its maximum allowed rate consistent with...