118885035
INFRARED PHOTOMETRY OF NGC 6791
We present deep JHK photometry of the old and metal-rich open cluster NGC 6791. The photometry reaches below the main-sequence turnoff to K ≈ 16.5 mag. We combine our photometry with that from Stetson et al. to provide color-magnitude diagrams showing K versus J - K, K versus V - K, and V versus V - K. We study the slope of the red giant branch in the infrared but find that it is not a useful metallicity indicator for the cluster, nor any metal-rich cluster that lacks a well-populated red giant branch, because it is not linear, as has often been assumed, in K versus J - K. The mean color of the red horizontal-branch/red clump stars provide an estimate of the cluster reddening, E(B - V) = 0.14 ± 0.04 mag for [Fe/H] = +0.4 ± 0.1. The mean magnitudes of these stars also provide a good distance estimate, (m - M)0 = 13.07 ± 0.04. Finally, we find that the isochrones of Yi et al. provide optimal fits in V versus B - V and V - K and K versus J - K and V - K for such values if [Fe/H] lies between +0.3 and +0.5 (with a slight preference for +0.5) and ages between 9 Gyr ([Fe/H] = +0.3) and 7.5 Gyr ([Fe/H] = +0.5).
35634571
Expression of Interest and RD Proposal for the Study of Nucleon Decay and Neutrino Physics Using a Large Underground Water Cherenkov Detector: UNO
16572388
Photometric Properties of the Near-Contact Binary GW Geminorum
New multiband CCD photometry is presented for the eclipsing binary GW Gem; the RI light curves are the first ever compiled. Four new minimum timings have been determined. Our analysis of eclipse timings observed during the past 79 years indicates a continuous period increase at a fractional rate of +(1.2 ± 0.1) × 10-10, in excellent agreement with the value +1.1 × 10-10 calculated from the Wilson-Devinney binary code. The new light curves display an inverse O'Connell effect increasing toward longer wavelengths. Hot- and cool-spot models are developed to describe these variations but we prefer a cool spot on the secondary star. Our light-curve synthesis reveals that GW Gem is in a semidetached, but near-contact, configuration. It appears to consist of a near-main-sequence primary star with a spectral type of about A7 and an evolved early K-type secondary star that completely fills its inner Roche lobe. Mass transfer from the secondary to the primary component is responsible for the observed secular period change.
119173891
The pulsating sdB+M eclipsing system NY Virginis and its circumbinary planets
We searched for circumbinary planets orbiting NY Vir in historical eclipse times including our long-term CCD data. Sixty-eight times of minimum light with accuracies better than 10 s were used for the ephemeris computations. The best fit to those timings indicated that the orbital period of NY Vir has varied due to a combination of two sinusoids with periods of P3=8.2 yr and P4=27.0 yr and semi-amplitudes of K3=6.9 s and K4=27.3 s, respectively. The periodic variations most likely arise from a pair of light-time effects due to the presence of third and fourth bodies that are gravitationally bound to the eclipsing pair. We have derived the orbital parameters and the minimum masses, M3 sini3 = 2.8 MJup and M4 sini4 = 4.5 MJup, of both objects. A dynamical analysis suggests that the outer companion is less likely to orbit the binary on a circular orbit. Instead we show that future timing data might push its eccentricity to moderate values for which the system exhibits long-term stability. The results demonstrate that NY Vir is probably a star-planet system, which consists of a very close binary star and two giant planets. The period ratio P3/P4 suggests that a long-term gravitational interaction between them would result in capture into a nearly 3:10 mean motion resonance. When the presence of the circumbinary planets is verified and understood more comprehensively, the formation and evolution of this planetary system should be advanced greatly.
2150926
A Chemical Abundance Study of three RHB and two RGB stars in NGC6637 (M69)
We present a detailed chemical abundance study of three red horizontal branch and two red giant branch stars in the metal-rich globular cluster NGC 6637 (M69). The value of [Fe/H] derived from LTE calculations is $-$0.77 $\pm$ 0.02 dex. We also discuss the anticorrelation between oxygen and sodium abundances in the program stars and compare the [Si/Ti] ratio of NGC 6637 with those of other globular clusters.
119111522
Variations in the Na—O anticorrelation in globular clusters: evidence for a deep mixing episode in red giant branch stars
The Na–O anticorrelation seen in almost all globular clusters ever studied using high-resolution spectroscopy is now generally explained by the primordial pollution from the first generation of the intermediate-mass asymptotic giant branch stars to the protostellar clouds of the second generation of stars. However, the primordial pollution scenario may not tell the whole story for the observed Na–O anticorrelations in globular clusters. Using the recent data by Carretta and his collaborators, the different shapes of the Na–O anticorrelations for red giant branch stars brighter than and fainter than the red giant branch bump can be clearly seen. If the elemental abundance measurements by Carretta and his collaborators are not greatly in error, this variation in the Na–O anticorrelation against luminosity indicates an internal deep mixing episode during the ascent of the low-mass red giant branch in globular clusters. Our result implies that the multiple stellar population division scheme solely based on [O/Fe] and [Na/Fe] ratios of a globular cluster, which is becoming popular, is not reliable for stars brighter than the red giant branch bump. Our result also suggests that sodium supplied by the deep mixing may alleviate the sodium underproduction problem within the primordial asymptotic giant branch pollution scenario.
119253557
Listening to Noise
We show how sign problems in simulations of many-body systems can manifest themselves in the form of heavy-tailed correlator distributions, similar to what is seen in electron propagation through disordered media. We propose an alternative statistical approach for extracting ground state energies in such systems, illustrating the method with a toy model and with lattice data for unitary fermions and for baryons in QCD.
118408274
Hard probes in heavy ion collisions at the LHC: heavy flavour physics
We present the results from the heavy quarks and quarkonia working group. This report gives benchmark heavy quark and quarkonium cross sections for $pp$ and $pA$ collisions at the LHC against which the $AA$ rates can be compared in the study of the quark-gluon plasma. We also provide an assessment of the theoretical uncertainties in these benchmarks. We then discuss some of the cold matter effects on quarkonia production, including nuclear absorption, scattering by produced hadrons, and energy loss in the medium. Hot matter effects that could reduce the observed quarkonium rates such as color screening and thermal activation are then discussed. Possible quarkonium enhancement through coalescence of uncorrelated heavy quarks and antiquarks is also described. Finally, we discuss the capabilities of the LHC detectors to measure heavy quarks and quarkonia as well as the Monte Carlo generators used in the data analysis.
15179947
CP violating B decays with R -parity violation
We study CP violating B decays in the minimal supersymmetric standard model with R-parity violation. We estimate how much R-parity violation modifies the SM predictions for CP asymmetries in B decays within the present bounds. The effects of R-parity- and lepton-number-violating couplings on the ratio of the decay amplitude due to R-parity violation to that of the SM can differ by one or two orders of magnitudes depending on the models of the left-handed quark mixing. It is possible to disentangle the R-parity violating effects from those of the SM and R-parity- conserving supersymmetric models within the present bounds comparing different CP violating decay amplitudes. We also study the effects of R-parity- and baryon-number-violating couplings and find that the effects could be large.
118674685
Zero cosmological constant and nonzero dark energy from the holographic principle
The first law of thermodynamics and the holographic principle applied to an arbitrary large cosmic causal horizon are shown to naturally demand a zero cosmological constant and a non-zero dynamical dark energy in the form of the holographic dark energy. A semiclassical analysis shows that the holographic dark energy has a parameter d = 1 and an equation of state comparable to current observational data if the entropy of the horizon saturates the Bekenstein-Hawking bound. This result indicates that quantum field theory should be modified on a large scale to explain the dark energy. The relations among the dark energy, the quantum vacuum energy and the entropic gravity are also discussed.
17111859
Black Hole as an Information Eraser
We discuss the identity of black hole entropy and show that the first law of black hole thermodynamics, in the case of a Schwarzschild black hole, can be derived from Landauer's principle by assuming that the black hole is one of the most efficient information erasers. The term "most efficient" implies that maximal information will be erased for a given amount of work. We calculate the discrete mass spectra and the entropy of a Schwarzschild black hole assuming that the black hole processes information in unit of bits. The black hole entropy acquires a subleading contribution proportional to the logarithm of its mass-squared in addition to the usual mass-squared term without an artificial cutoff. We also argue that the minimum of the black hole mass is $\sqrt{\log 2/(8\pi)}M_{\rm P}$.