A5054455759- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Adaptive optics and wavefront sensing
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- History and Developments in Astronomy
- Pulsars and Gravitational Waves Research
- Galaxies: Formation, Evolution, Phenomena
- Astro and Planetary Science
- Scientific Research and Discoveries
- Astrophysical Phenomena and Observations
- Cosmology and Gravitation Theories
- Impact of Light on Environment and Health
- Astrophysics and Cosmic Phenomena
- Photocathodes and Microchannel Plates
- Relativity and Gravitational Theory
- Planetary Science and Exploration
- Distributed and Parallel Computing Systems
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Space Science and Extraterrestrial Life
- Additive Manufacturing Materials and Processes
- Seismic Waves and Analysis
University of Utah
2023-2024
Campbell Collaboration
1995-2009
Kavli Institute for Particle Astrophysics and Cosmology
1995-2007
Massachusetts Institute of Technology
1998-2006
Max Planck Society
2004
Max Planck Innovation
2004
University of Washington
1989-2003
European Southern Observatory
2001
Seattle University
2001
University of California, Berkeley
1993-2000
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...
The EROS and MACHO collaborations have each published upper limits on the amount of planetary mass dark matter in Galactic Halo obtained from gravitational microlensing searches. In this paper two are combined to give a much stronger constraint abundance low MACHOs.
We present the first detection of parallax effects in a gravitational microlensing event. Parallax event observed only from Earth appears as distortion (otherwise symmetrical) light curve arising motion around Sun. This can be detected if duration is not much less than year and projected velocity lens larger orbital about The presented here has (or Einstein diameter crossing time) = 220 days clearly shows resulting Earth's motion. find that 75 ± 5 km s-1 at an angle 28° 4° direction...
We report the detection of 45 candidate microlensing events in fields toward Galactic bulge. These come from analysis 24 containing 12.6 million stars observed for 190 days 1993. Many these are extremely high signal-to-noise ratio and remarkable examples gravitational microlensing. The distribution peak magnifications is shown to be consistent with interpretation events. Using a subsample 1.3 "clump giant" whose distance efficiency well known, we find 13 estimate optical depth bulge as...
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...
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...
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...
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...
We present the light curves of 21 gravitational microlensing events from first six years MACHO Project survey that are likely examples lensing by binary systems. These were manually selected a total sample ~350 candidate either detected Alert System or discovered through retrospective analyses database. At least 14 these exhibit strong (caustic) features, and four well fit with large mass ratio (brown dwarf planetary) systems, although fits not necessarily unique. The event rate is roughly...
We have frequency-analyzed 6391 variables classified earlier as fundamental-mode RR Lyrae (RR0) stars in the MACHO database on Large Magellanic Cloud (LMC). The overwhelming majority (i.e., 96%) of these been proved to be indeed RR0 stars, whereas remaining ones fallen into one following categories: single- and double-mode Cepheids, binaries, first-overtone nonclassified variables. Special attention has paid properties amplitude- phase-modulated (the Blazhko stars). found altogether 731...
The Macho Project Year One Database contains photometric observations of twenty-two 40 arcmin fields in the bar region LMC which are analyzed to select stars with properties field RR Lyrae stars. resulting set ~7900 stars, range brightness 18.7 < V 19.7, is phased and distribution periods determined. There an excess near 0.28^d^ show skewed light curves predicted [Stellingwerf et al. ApJ, 313, L75 (1987)] be characteristic second-harmonic pulsations From a sample 500 examined detail, we have...
We report the discovery of 45 beat Cepheids in Large Magellanic Cloud (LMC) using MACHO Project photometry database. The variables which are pulsating simultaneously two radial modes shown to break cleanly into period-ratio groups, providing first unambiguous evidence that second overtone is indeed excited real Cepheids. Thirty stars beating fundamental and mode (F/1H, with a period ratio neighborhood 0.72), fifteen (1H/2H, near 0.80). F/1H ratios systematically higher than known Galactic...
We present 47 spectroscopically confirmed quasars discovered behind the Magellanic Clouds identified via photometric variability in MACHO database. Thirty-eight lie Large Cloud and nine Small Cloud, more than tripling number of previously known this region. The cover redshift interval 0.2 < z 2.8 have apparent mean magnitudes 16.6 ≤ 20.1. discuss details quasar candidate selection based on time database results spectroscopic follow-up observations. Our detection efficiency was 20%; primary...
We report the discovery of RV Tauri stars in Large Magellanic Cloud (LMC). In light- and color-curve behavior, appear to be a direct extension type II Cepheids longer periods. A single period-luminosity-color relationship is seen describe both LMC. derive relation V0 = 17.89(±0.20)-2.95(±0.12) log P + 5.49(±0.35)⟨(V - R)0⟩, which valid for period range 0.9 < 1.75. Assuming distance modulus LMC 18.5, terms absolute luminosities becomes MV -0.61(±0.20)-2.95(±0.12) R)0⟩.
view Abstract Citations (85) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The MACHO Project LMC Variable Star Inventory.V.Classification and Orbits of 611 Eclipsing Binary Stars Alcock, C. ; Allsman, R. A. Alves, D. Axelrod, T. S. Becker, Bennett, P. Cook, K. H. Freeman, Griest, Lacy, Lehner, M. J. Marshall, L. Minniti, Peterson, B. Pratt, Quinn, Rodgers, W. Stubbs, Sutherland, Welch, We report the characteristics eclipsing binary stars in...
We present a 9 million star color-magnitude diagram (9M CMD) of the LMC bar. The 9M CMD reveals complex superposition different age and metallicity stellar populations, with important evolutionary phases occurring over 3 orders magnitude in number density. First, we count non-variable supergiants, associated Cepheids, measure effective temperatures defining instability strip. Lifetime predictions evolution theory are tested, implications for origin low-luminosity Cepheids. highly-evolved AGB...