A5041464039- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astrophysical Phenomena and Observations
- Adaptive optics and wavefront sensing
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- History and Developments in Astronomy
- Pulsars and Gravitational Waves Research
- Planetary Science and Exploration
- Scientific Research and Discoveries
- Calibration and Measurement Techniques
- Astronomical and nuclear sciences
- Impact of Light on Environment and Health
- Geophysics and Gravity Measurements
- Superconducting Materials and Applications
- Cosmology and Gravitation Theories
- Geophysics and Sensor Technology
- Solar and Space Plasma Dynamics
- Photocathodes and Microchannel Plates
- Historical Astronomy and Related Studies
- Historical and Architectural Studies
Booz Allen Hamilton (United States)
2025
McMaster University
2012-2021
University College London
2006-2020
University of St Andrews
2020
Kinokuniya
2020
New York University Press
2020
University of Southampton
2018
Columbia University
2017
Universidade da Coruña
2016
Campbell Collaboration
1995-2009
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...
Abstract Despite constituting a widespread and significant environmental change, understanding of artificial nighttime skyglow is extremely limited. Until now, published monitoring studies have been local or regional in scope typically short duration. In this first major international compilation data we answer several key questions about properties. Skyglow observed to vary over four orders magnitude, range hundreds times larger than was the case before light. Nearly all study sites were...
Abstract Diffuse Galactic cirrus, or diffuse light (DGL), can be a prominent component in the background of deep wide-field imaging surveys. The DGL provides unique insights into physical and radiative properties dust grains our Milky Way, it also serves as contaminant on images, obscuring detection sources such low surface brightness galaxies. However, is challenging to disentangle from other components night sky. In this paper, we present technique for photometric characterization cirrus...
We describe sensitive techniques for identifying variable stars in multiepoch photometry lists made two or more bandpasses pairwise a single bandpass. Our search strategy employs the correlation brightness change between paired frames, which allows extraction of information on variability presence random photometric noise. A statistic assessing tape degree contamination by an unresolved source (depending circumstance) is also described, as well bootstrap scheme predicting confidence...
We present late-time optical and mid-infrared observations of the Type II supernova 2003gd in galaxy NGC 628. Mid-infrared excesses consistent with cooling dust ejecta are observed 499 to 678 days after outburst accompanied by increasing extinction growing asymmetries emission-line profiles. Radiative-transfer models show that up 0.02 solar masses has formed within ejecta, beginning as early 250 outburst. These formation can be efficient massive-star supernovae could have been major...
Characterizing the nature and spatial distribution of lensing objects that produce previously measured microlensing optical depth toward Large Magellanic Cloud (LMC) remains an open problem. We present appraisal ability SuperMACHO Project, a next-generation survey directed LMC, to discriminate between various proposed populations. consider two scenarios: by uniform foreground screen self-lensing LMC stars. have carried out extensive simulations, based upon data obtained during first year...
We provide AAVSO Photometric All-Sky Survey (APASS) photometry in the Landolt BV and Sloan g'r'i' bands for all 425,743 stars included fourth RAVE Data Release. The internal accuracy of APASS stars, expressed as error mean data obtained separately calibrated over a median four distinct observing epochs distributed between 2009 2013, is 0.013, 0.012, 0.014, 0.021 mag B, V, g', r', i' bands, respectively. equally high external has been verified on secondary photometric standard not involved...
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%
We present the microlensing optical depth toward Galactic bulge based on detection of 99 events found in our Difference Image Analysis (DIA) survey. This analysis encompasses 3 yr data, covering ~17 million stars ~4 deg2, to a source-star baseline magnitude limit V = 23. The DIA technique improves quality photometry crowded fields, and allows us detect more with faint source stars. find that this method increases number by 85% compared standard technique. light curves are presented, fit...
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 present a detailed study of the viewing angles and geometry inner LMC (ρ ≲ 4°) based on sample more than 2000 MACHO Cepheids with complete {VR}KC light curves single-phase Two Micron All Sky Survey (2MASS) JHKs observations. The is considerably larger any previously studied subset has an improved areal coverage. Single-epoch random-phase 2MASS photometry corrected using V to derive mean magnitudes. analyze resulting period-luminosity relations in VRJHKs recover statistical reddening...
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,...
We report the discovery of an extensive system scattered-light echo arclets associated with recent supernovae in local neighborhood Milky Way: Tycho (SN 1572) and Cassiopeia A. Existing work suggests that SN was a thermonuclear explosion while Cas A supernova core-collapse explosion. Precise classifications according to modern nomenclature require spectra outburst light. In case ancient SNe, this can only be done spectroscopy their light echo, where echoes from is first step. Adjacent...
We report the successful identification of type supernova responsible for remnant SNR 0509-675 in Large Magellanic Cloud (LMC) using Gemini spectra surrounding light echoes. The ability to classify outbursts associated with centuries-old remnants provides a new window into several aspects research and is likely be providing constraints on additional LMC supernovae as well their historical counterparts Milky Way Galaxy (MWG). combined spectrum echo from shows broad emission absorption lines...
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...
view Abstract Citations (148) References (76) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Carina Dwarf Spheroidal Galaxy: How Dark is it? Mateo, Mario ; Olszewski, Edward W. Pryor, Carlton Welch, Douglas L. Fischer, Philippe We have obtained precise (<σ> = 3.1 km s^-1^) radial velocities of 23 photometrically-selected normal giant stars located near the center dwarf spheroidal (dSph) galaxy. Of this sample, 17 are members based on their heliocentric...
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...