A
bstract
We describe a proposal to add a set of very forward detectors to the CMS experiment for the high-luminosity era of the Large Hadron Collider to search for beyond the standard model ...long-lived particles, such as dark photons, heavy neutral leptons, axion-like particles, and dark Higgs bosons. The proposed subsystem is called
FACET
for
F
orward-
A
perture
C
MS
E
x
T
ension, and will be sensitive to any particles that can penetrate at least 50 m of magnetized iron and decay in an 18 m long, 1 m diameter vacuum pipe. The decay products will be measured in detectors using identical technology to the planned CMS Phase-2 upgrade.
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.
We present microlensing events in the 2015 Korea Microlensing Telescope Network (KMTNet) data and our procedure for identifying these events. In particular, candidates were detected with a novel ..."completed-event" microlensing event-finder algorithm. The algorithm works by making linear fits to a grid of point-lens microlensing models. This approach is rendered computationally efficient by restricting u0 to just two values (0 and 1), which we show is quite adequate. The implementation presented here is specifically tailored to the commission-year character of the 2015 data, but the algorithm is quite general and has already been applied to a completely different (non-KMTNet) data set. We outline expected improvements for 2016 and future KMTNet data. The light curves of the 660 "clear microlensing" and 182 "possible microlensing" events that were found in 2015 are presented along with our policy for their public release.
Abstract
We report on the first results from a large-scale observing campaign aiming to use astrometric microlensing to detect and place limits on the mass of single objects, including stellar ...remnants. We used the
Hubble Space Telescope
to monitor stars near the Galactic Center for three years, and we measured the brightness and positions of ∼2 million stars at each observing epoch. In addition to this, we monitored the same pointings using the VIMOS imager on the Very Large Telescope. The stars we monitored include several bright microlensing events observed from the ground by the OGLE collaboration. In this paper, we present the analysis of our photometric and astrometric measurements for six of these events, and derive mass constraints for the lens in each of them. Although these constraints are limited by the photometric precision of ground-based data, and our ability to determine the lens distance, we were able to constrain the size of the Einstein ring radius thanks to our precise astrometric measurements—the first routine measurements of this type from a large-scale observing program. This demonstrates the power of astrometric microlensing as a tool to constrain the masses of stars, stellar remnants, and, in the future, extrasolar planets, using precise ground- and space-based observations.
We analyze the single microlensing event OGLE-2015-BLG-1482 simultaneously observed from two ground-based surveys and from Spitzer. The Spitzer data exhibit finite-source effects that are due to the ...passage of the lens close to or directly over the surface of the source star as seen from Spitzer. Such finite-source effects generally yield measurements of the angular Einstein radius, which when combined with the microlens parallax derived from a comparison between the ground-based and the Spitzer light curves yields the lens mass and lens-source relative parallax. From this analysis, we find that the lens of OGLE-2015-BLG-1482 is a very low-mass star with a mass or a brown dwarf with a mass , which are located at and , respectively, where is the distance between the lens and the source, and thus it is the first isolated low-mass microlens that has been decisively located in the Galactic bulge. The degeneracy between the two solutions is severe ( ). The fundamental reason for the degeneracy is that the finite-source effect is seen only in a single data point from Spitzer, and this single data point gives rise to two solutions for , the angular size of the source in units of the angular Einstein ring radius. Because the degeneracy can be resolved only by relatively high-cadence observations around the peak, while the Spitzer cadence is typically , we expect that events for which the finite-source effect is seen only in the Spitzer data may frequently exhibit this degeneracy. For OGLE-2015-BLG-1482, the relative proper motion of the lens and source for the low-mass star is , while for the brown dwarf it is . Hence, the degeneracy can be resolved within from direct-lens imaging by using next-generation instruments with high spatial resolution.
The numerical kernel approach to difference imaging has been implemented and applied to gravitational microlensing events observed by the PLANET collaboration. The effect of an error in the ...source-star coordinates is explored and a new algorithm is presented for determining the precise coordinates of the microlens in blended events, essential for accurate photometry of difference images. It is shown how the photometric reference flux need not be measured directly from the reference image but can be obtained from measurements of the difference images combined with the knowledge of the statistical flux uncertainties. The improved performance of the new algorithm, relative to isis2, is demonstrated.
Abstract
We report the joint WASP/KELT discovery of WASP-167b/KELT-13b, a transiting hot Jupiter with a 2.02-d orbit around a V = 10.5, F1V star with Fe/H = 0.1 ± 0.1. The 1.5 R
Jup planet was ...confirmed by Doppler tomography of the stellar line profiles during transit. We place a limit of <8 M
Jup on its mass. The planet is in a retrograde orbit with a sky-projected spin–orbit angle of λ = −165° ± 5°. This is in agreement with the known tendency for orbits around hotter stars to be more likely to be misaligned. WASP-167/KELT-13 is one of the few systems where the stellar rotation period is less than the planetary orbital period. We find evidence of non-radial stellar pulsations in the host star, making it a δ-Scuti or γ-Dor variable. The similarity to WASP-33, a previously known hot-Jupiter host with pulsations, adds to the suggestion that close-in planets might be able to excite stellar pulsations.
The KMTNet/K2-C9 (Kepler) Data Release Kim, H.-W.; Hwang, K.-H.; Kim, D.-J. ...
The Astronomical journal,
05/2018, Letnik:
155, Številka:
5
Journal Article
Recenzirano
Odprti dostop
We present Korea Microlensing Telescope Network (KMTNet) light curves for microlensing-event candidates in the Kepler K2 C9 field having peaks within three effective timescales of the Kepler ...observations. These include 181 "clear microlensing" and 84 "possible microlensing" events found by the KMTNet event finder, plus 56 other events found by OGLE and/or MOA that were not found by KMTNet. All data for the first two classes are immediately available for public use without restriction.
Using gravitational microlensing, we detected a cold terrestrial planet
orbiting one member of a binary star system. The planet has low mass
(twice Earth's) and lies projected at ∼0.8 astronomical ...units (AU) from
its host star, about the distance between Earth and the Sun. However,
the planet's temperature is much lower, <60 Kelvin, because the host
star is only 0.10 to 0.15 solar masses and therefore more than 400 times
less luminous than the Sun. The host itself orbits a slightly more
massive companion with projected separation of 10 to 15 AU. This
detection is consistent with such systems being very common.
Straightforward modification of current microlensing search strategies
could increase sensitivity to planets in binary systems. With more
detections, such binary-star planetary systems could constrain models of
planet formation and evolution.
Studies in many areas of particle and astroparticle physics require a good knowledge of hadron spectra produced at small angles to the primary particle direction, e.g. in the TeV energy range at the ...LHC. The present work is dedicated to development of a particle identification technique based on the transition radiation produced by highly relativistic particles. Dedicated experimental studies were carried out and simulation models were developed to reproduce experimental data obtained with different prototypes. On the basis of these studies, the possibility of making detectors able to provide hadron composition measurement with high accuracy and identify particles with high efficiency in the forward experiments at the LHC was demonstrated. Two concepts of large scale TRDs are proposed: the straw TRD and the GaAs/straw TRD. They allow the reconstruction of hadron spectra with accuracy about or below 1% and to identify particles with high efficiency in individual events. As an example, suppression of the combinatorial background was demonstrated for the D0→K−π+ and D̄0→K+π− decays.
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