We present a detailed study of the viewing angles and geometry of the inner LMC (rho ~ 4 super(j0)) based on a sample of more than 2000 MACHO Cepheids with complete {VR} sub(KC) light curves and ...single-phase Two Micron All Sky Survey (2MASS) JHK sub(s) observations. The sample is considerably larger than any previously studied subset of LMC Cepheids and has an improved areal coverage. Single-epoch random-phase 2MASS photometry is corrected using MACHO V light curves to derive mean JHK sub(s) magnitudes. We analyze the resulting period-luminosity relations in VRJHK sub(s) to recover statistical reddening and distance to each individual Cepheid, with respect to the mean distance modulus and reddening of the LMC. By fitting a plane solution to the derived individual distance moduli, the values of LMC viewing angles are obtained: position angle theta = 151 degree 0 plus or minus 2 degree 4, inclination i = 30 degree 7 plus or minus 1 degree 1. In the so-called ring analysis, we find a strong dependence of the derived viewing angles on the adopted center of the LMC, which we interpret as being due to deviations from planar geometry. Analysis of residuals from the plane fit indicates the presence of a symmetric warp in the LMC disk and the bar elevated above the disk plane. Nonplanar geometry of the inner LMC explains a broad range for values of i and theta in the literature and suggests caution when deriving viewing angles from inner LMC data.
Using 7 yr of MACHO survey data, we present a new determination of the optical depth to microlensing toward the Galactic bulge. We select the sample of 62 microlensing events (60 unique) on clump ...giant sources and perform a detailed efficiency analysis. We use only the clump giant sources because these are bright bulge stars and are not as strongly affected by blending as other events. Using a subsample of 42 clump events concentrated in an area of 4.5 deg super(2) with 739,000 clump giant stars, we find t = 2.17 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(4) sub(3) super(7) sub(8) x 10 super(-6) at (l,b) = (1.50, - 2.68), somewhat smaller than found in most previous MACHO studies but in excellent agreement with recent theoretical predictions. We also present the optical depth in each of the 19 fields in which we detected events and find limits on optical depth for fields with no events. The errors in optical depth in individual fields are dominated by Poisson noise. We measure optical depth gradients of (1.06 c 0.71) x 10 super(-6) deg super(-1) and (0.29 c 0.43) x 10 super(-6) deg super(-1) in the Galactic latitude b and longitude l directions, respectively. Finally, we discuss the possibility of anomalous duration distribution of events in the field 104 centered on (l,b) = (3.11, - 3.01), as well as investigate spatial clustering of events in all fields.
Using partial wave unitarity and the observed density of the Universe, it is shown that a stable elementary particle which was once in thermal equilibrium cannot have a mass greater than 340 TeV. An ...extended object which was once in thermal equlibrium cannot have a radius less than 7.5 x 10(exp -7) fm. A lower limit to the relic abundance of such particles is also found.
We present our analysis on new limits of the dark matter (DM) halo consisting of primordial black holes (PBHs) or massive compact halo objects. We present a search of the first two yr of publicly ...available Kepler mission data for potential signatures of gravitational microlensing caused by these objects as well as an extensive analysis of the astrophysical sources of background error. These include variable stars, flare events, and comets or asteroids that are moving through the Kepler field. We discuss the potential of detecting comets using the Kepler light curves, presenting measurements of two known comets and one unidentified object, most likely an asteroid or comet. After removing the background events with statistical cuts, we find no microlensing candidates. We therefore present our Monte Carlo efficiency calculation in order to constrain the PBH DM with masses in the range of 2 x 10 super(-9) M sub(middot in circle) to 10 super(-7) M sub(middot in circle). We find that PBHs in this mass range cannot make up the entirety of the DM, thus closing a full order of magnitude in the allowed mass range for PBH DM.
We present new limits on the allowed masses of a dark matter (DM) halo consisting of primordial black holes (PBH) (or any other massive compact halo object). We analyze two years of data from the ...Kepler satellite, searching for short-duration bumps caused by gravitational microlensing. After removing background events consisting of variable stars, flare events, and comets or asteroids moving through the Kepler field, we find no microlensing candidates. We measure the efficiency of our selection criteria by adding millions of simulated microlensing lensing events into the Kepler light curves. We find that PBH DM with masses in the range 2 × 10(-9) MSymbol: see text to 10(-7)MSymbol: see text cannot make up the entirety of the DM in the Milky Way. At the low-mass end, this decreases the allowed mass range by more than an order of magnititude.
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