15669528
Planet II: A Microlensing and Transit Search for Extrasolar Planets
Due to their extremely small luminosity compared to the stars they orbit, planets outside our own Solar System are extraordinarily difficult to detect directly in optical light. Careful photometric monitoring of distant stars, however, can reveal the presence of exoplanets via the microlensing or eclipsing effects they induce. The international PLANET collaboration is performing such monitoring using a cadre of semi-dedicated telescopes around the world. Their results constrain the number of gas giants orbiting 1–7 AU from the most typical stars in the Galaxy. Upgrades in the program are opening regions of “exoplanet discovery space” – toward smaller masses and larger orbital radii – that are inaccessible to the Doppler velocity technique. 1. Looking for Exoplanets through the Lens of Gravity The Doppler velocity technique, which measures the small to and fro motion induced in a parent star by an orbiting planet, has clearly demonstrated that several percent of solar-type stars have planets very unlike those in the Solar System (Marcy, Cochran & Mayor 2000). Known extrasolar planets are plotted with the nine Solar System planets in Figure 1. With the exception of the few bodies orbiting dead stellar cores known as pulsars, exoplanets discovered
2974286
First microlens mass measurement: Planet photometry of EROS BLG-2000-5
We analyze PLANET photometric observations of the caustic-crossing binary lens microlensing event, EROS BLG-2000-5, and find that modeling the observed light curve requires incorporation of the microlens parallax and the binary orbital motion. The projected Einstein radius (E = 3.61 ± 0.11 AU) is derived from the measurement of the microlens parallax, and we are also able to infer the angular Einstein radius (θE = 1.38 ± 0.12 mas) from the finite source effect on the light curve, combined with an estimate of the angular size of the source given by the source position in a color-magnitude diagram. The lens mass, M = 0.612 ± 0.057 M☉, is found by combining these two quantities. This is the first time that parallax effects are detected for a caustic-crossing event and also the first time that the lens mass degeneracy has been completely broken through photometric monitoring alone. The combination of E and θE also allows us to conclude that the lens lies in the near side of the disk, within 2.6 kpc of the Sun, while the radial velocity measurement indicates that the source is a Galactic bulge giant.
73625238
1318 new variable stars in a 0.25 square degree region of the Galactic plane
We conducted a deep photometric survey of a 0.5 ◦ × 0.5 ◦ area of the Galactic plane using the WFI instrument on the 2.2-m ESO telescope on La Silla, Chile. The dataset comprises a total of 267 R-band images, 204 from a 16 day observation run in 2005, supplemented by 63 images from a six week period in 2002. Our reduction employed the new numerical kernel difference image analysis method as implemented in the pysis3 code and resulted in more than 500 000 lightcurves of stars down to a magnitude limit of R ∼ 24.5. A search for variable stars resulted in the detection of 1318 variables of different types. 1011 of these are eclipsing or contact binary stars. A number of the contact binaries have low mass-ratios and several of the detached binaries appear to have low-mass components. Three candidate contact binaries have periods at the known cut off including two with periods lower than any previously published. Also identified are 3 possible pre-main sequence detached eclipsing binaries.
16941683
Microlensing Constraints on the Frequency of Jupiter-Mass Companions: Analysis of 5 Years of PLANET Photometry
We analyze 5 years of PLANET photometry of microlensing events toward the Galactic bulge to search for the short-duration deviations from single-lens light curves that are indicative of the presence of planetary companions to the primary microlenses. Using strict event-selection criteria, we construct a well-defined sample of 43 intensively monitored events. We search for planetary perturbations in these events over a densely sampled region of parameter space spanning two decades in mass ratio and projected separation, but find no viable planetary candidates. By combining the detection efficiencies of the events, we find that, at 95% confidence, less than 25% of our primary lenses have companions with mass ratio q = 10-2 and separations in the lensing zone, [0.6-1.6]θE, where θE is the Einstein ring radius. Using a model of the mass, velocity, and spatial distribution of bulge lenses, we infer that the majority of our lenses are likely M dwarfs in the Galactic bulge. We conclude that less than 33% of M dwarfs in the Galactic bulge have companions with mass mp = MJ between 1.5 and 4 AU, and less than 45% have companions with mp = 3MJ between 1 and 7 AU, the first significant limits on planetary companions to M dwarfs. We consider the effects of the finite size of the source stars and changing our detection criterion, but find that these do not alter our conclusions substantially.
119493694
H alpha equivalent width variations across the face of a microlensed K giant in the galactic bulge
We present Very Large Telescope FORS1 spectroscopy that temporally resolves the second caustic crossing of the Galactic bulge K giant source of microlensing event EROS 2000-BLG-5, the first time this has been accomplished for several phases of a caustic transit. The similar to1 Angstrom H alpha equivalent width of the source star increases slightly as the center of the star egresses the caustic and then plummets by 30% during the final limb crossing. These changes are not seen in contemporaneous spectra of control stars in the FORS1 slit but are qualitatively consistent with expectations from stellar atmosphere models as the caustic differentially magnifies different portions of the stellar face of the target. Observations such as these in a variety of stellar lines are equivalent to atmospheric tomography and are expected to provide a direct test of stellar models.
55031010
Difference image analysis: extension to a spatially varying photometric scale factor and other considerations
We present a general framework for matching the point-spread function (PSF), photometric scaling and sky background between two images, a subject which is commonly referred to as difference image analysis (DIA). We introduce the new concept of a spatially varying photometric scale factor which will be important for DIA applied to wide-field imaging data in order to adapt to transparency and airmass variations across the field-of-view. Furthermore, we demonstrate how to separately control the degree of spatial variation of each kernel basis function, the photometric scale factor and the differential sky background. We discuss the common choices for kernel basis functions within our framework, and we introduce the mixed-resolution delta basis functions to address the problem of the size of the least-squares problem to be solved when using delta basis functions. We validate and demonstrate our algorithm on simulated and real data. We also describe a number of useful optimizations that may be capitalized on during the construction of the least-squares matrix and which have not been reported previously. We pay special attention to presenting a clear notation for the DIA equations which are set out in a way that will hopefully encourage developers to tackle the implementation of DIA software.
119986660
Missing mass spectra in pp inelastic scattering at total energies of 23 GeV and 31 GeV
Abstract Results are reported of measurements of the momentum spectra of protons emitted at small angles in inelastic reactions at the CERN ISR. The data are for total energies s 1 2 of 23 GeV and 31 GeV. The structure of the peak at low values of the missing mass M (of the system recoiling against the observed proton) is studied. The missing mass distributions have the form ( M 2 ) − B ( t ) where t is the four-momentum transfer squared. B ( t ) drops from 0.98±0.06 at t =−0.15 GeV 2 to 0.20±0.15 at t =−1.65 GeV 2 . The results are compared with a simple triple-Regge formula.
56225334
Double Pomeron Exchange: the early years
I review the early experimental searches for double pomeron exchange, the first observations at the CERN Intersecting Storage Rings (ISR) and further studies at the SPS and Tevatron (fixed target). I only have space for a superficial coverage of some highlights, and will not cover later colliders with s>100 GeV.
116921384
Hard diffraction in CDF
The aim of these studies is to use hard (large Q{sup 2}) processes to investigate the partonic nature of the pomeron. We have measured events with large rapidity gaps between balancing high E{sub T} jets, events with two forward (same-side) jets and a large gap (diffractive di-jet production), diffractive W{sup {+-}} production and diffractive heavy flavor (J/{psi} and b-quark) production. Candidate events of the type double-pomeron {yields} di-jet are observed. I close with a look at the future (Run II).
115609427
VIIth Blois Workshop summary: experimental
The Blois Workshop has become a conference not just restricted to diffractive scattering, but including topics such as searches for SUSY and Higgs, measurements of the top mass and b-decays. I will mention these briefly but will mostly discuss new results (and needed future measurements) in hard diffraction at HERA and the Tevatron.
120083891
A Search for the Higgs boson using very forward tracking detectors with CDF
The authors propose to add high precision track detectors 55 m downstream on both (E and W) sides of CDF, to measure high Feynman-x protons and antiprotons in association with central states. A primary motivation is to search for the Higgs boson, and if it is seen to measure its mass precisely. The track detectors will be silicon strip telescopes backed up by high resolution time-of-flight counters. They will have four spectrometer arms, for both sides of the p and {bar p} beams. The addition of these small detectors effectively converts the Tevatron into a gluon-gluon collider with {radical}s from 0 to {approx} 200 GeV. This experiment also measures millions/year clean high- |t| elastic p{bar p} scattering events and produce millions of pure gluon jets. Besides a wealth of other unique QCD studies they will search for signs of exotic physics such as SUSY and Large Extra Dimensions. They ask the Director to ask the PAC to take note of this Letter of Intent at its April meeting, to consider a proposal at the June meeting and to make a decision at the November 2001 meeting. They request that the Directorage ask the Beams Division to evaluate the consequences andmore » cost of the proposed Tevatron modifications, and CDF to evaluate any effect on its baseline program and to review the technical aspects of the detectors, DAQ and trigger integration.« less