Metallicities for 13 nearby open clusters from high-resolution spectroscopy of dwarf and giant stars. Stellar metallicity, stellar mass, and giant planets

We present a study of accurate stellar parameters and iron abundances for 39 giants and 16 dwarfs in the 13 open clusters IC2714, IC4651, IC4756, NGC2360, NGC2423, NGC2447 (M93), NGC2539, NGC2682 (M67), NGC3114, NGC3680, NGC4349, NGC5822, NGC6633. The analysis was done using a set of high-resolution and high-S/N spectra obtained with the UVES spectrograph (VLT). These clusters are currently being searched for planets using precise radial velocities. For all the clusters, the derived average metallicities are close to solar. Interestingly, the values derived seem to depend on the line-list used. This dependence and its implications for the study of chemical abundances in giants stars are discussed. We show that a careful choice of the lines may be crucial for the derivation of metallicities for giant stars on the same metallicity scale as those derived for dwarfs. Finally, we discuss the implications of the derived abundances for the metallicity- and mass-giant planet correlation. We conclude that a good knowledge of the two parameters is necessary to correctly disentangle their influence on the formation of giant planets.Comment: accepted for publication in A&

Hidden symmetry of the three-dimensional Einstein-Maxwell equations

It is shown how to generate three-dimensional Einstein-Maxwell fields from known ones in the presence of a hypersurface-orthogonal non-null Killing vector field. The continuous symmetry group is isomorphic to the Heisenberg group including the Harrison-type transformation. The symmetry of the Einstein-Maxwell-dilaton system is also studied and it is shown that there is the $SL(2,{\bf R})$ transformation between the Maxwell and the dilaton fields. This $SL(2,{\bf R})$ transformation is identified with the Geroch transformation of the four-dimensional vacuum Einstein equation in terms of the Ka{\l}uza-Klein mechanism.Comment: 5 page

Angular profile of emission of non-zero spin fields from a higher-dimensional black hole

Recent works have included the effect of rotation on simulations of black hole events at the LHC, showing that the angular momentum of the black hole cannot be ignored and it makes a non-trivial contribution for most of the lifetime of the black hole. A key consequence of the rotation of the black hole is that the Hawking radiation is no longer isotropic, making it more difficult to infer space–time parameters from measurements of the emitted particles. In this Letter we study the angular distribution of the Hawking emission of non-zero spin particles with specific helicity on the brane. We argue that the shape of the distribution could be used as a measure of the angular momentum of the black hole

Competition and/or Coexistence of Antiferromagnetism and Superconductivity in CeRhIn5_5 and CeCoIn5_5

The Ce compounds CeCoIn$_5$ and CeRhIn$_5$ are ideal model systems to study the competition of antiferromagnetism (AF) and superconductivity (SC). Here we discuss the pressure--temperature and magnetic field phase diagrams of both compounds. In CeRhIn$_5$ the interesting observation is that in zero magnetic field a coexistence AF+SC phase exist inside the AF phase below the critical pressure $p_{\rm c}^\star \approx 2$ GPa. Above $p_{\rm c}^\star$ AF is suppressed in zero field but can be re-induced by applying a magnetic field. The collapse of AF under pressure coincides with the abrupt change of the Fermi surface. In CeCoIn$_5$ a new phase appears at low temperatures and high magnetic field (LTHF) which vanishes at the upper critical field $H_{\rm c2}$. In both compounds the paramagnetic pair breaking effect dominates at low temperature. We discuss the evolution of the upper critical field under high pressure of both compounds and propose a simple picture of the glue of reentrant magnetism to the upper critical field in order to explain the interplay of antiferromagnetic order and superconductivity.Comment: 6 pages, 7 figures, Manuscript for Proceedings of the International Conference on Quantum Criticality and Novel Phases (QCNP09, Dresden); to appear in pss(b

A Spitzer IRS Study of Debris Disks Around Planet-Host Stars

Since giant planets scatter planetesimals within a few tidal radii of their orbits, the locations of existing planetesimal belts indicate regions where giant planet formation failed in bygone protostellar disks. Infrared observations of circumstellar dust produced by colliding planetesimals are therefore powerful probes of the formation histories of known planets. Here we present new Spitzer IRS spectrophotometry of 111 Solar-type stars, including 105 planet hosts. Our observations reveal 11 debris disks, including two previously undetected debris disks orbiting HD 108874 and HD 130322. Combining our 32 micron spectrophotometry with previously published MIPS photometry, we find that the majority of debris disks around planet hosts have temperatures in the range 60 < T < 100 K. Assuming a dust temperature T = 70 K, which is representative of the nine debris disks detected by both IRS and MIPS, we find that debris rings surrounding Sunlike stars orbit between 15 and 240 AU, depending on the mean particle size. Our observations imply that the planets detected by radial-velocity searches formed within 240 AU of their parent stars. If any of the debris disks studied here have mostly large, blackbody emitting grains, their companion giant planets must have formed in a narrow region between the ice line and 15 AU.Comment: Accepted for publication in the Astronomical Journal. 14 pages, including five figures and two table

Metabolic Syndrome Derived from Principal Component Analysis and Incident Cardiovascular Events: The Multi Ethnic Study of Atherosclerosis (MESA) and Health, Aging, and Body Composition (Health ABC).

Background. The NCEP metabolic syndrome (MetS) is a combination of dichotomized interrelated risk factors from predominantly Caucasian populations. We propose a continuous MetS score based on principal component analysis (PCA) of the same risk factors in a multiethnic cohort and compare prediction of incident CVD events with NCEP MetS definition. Additionally, we replicated these analyses in the Health, Aging, and Body composition (Health ABC) study cohort. Methods and Results. We performed PCA of the MetS elements (waist circumference, HDL, TG, fasting blood glucose, SBP, and DBP) in 2610 Caucasian Americans, 801 Chinese Americans, 1875 African Americans, and 1494 Hispanic Americans in the multiethnic study of atherosclerosis (MESA) cohort. We selected the first principal component as a continuous MetS score (MetS-PC). Cox proportional hazards models were used to examine the association between MetS-PC and 5.5 years of CVD events (n = 377) adjusting for age, gender, race, smoking and LDL-C, overall and by ethnicity. To facilitate comparison of MetS-PC with the binary NCEP definition, a MetS-PC cut point was chosen to yield the same 37% prevalence of MetS as the NCEP definition (37%) in the MESA cohort. Hazard ratio (HR) for CVD events were estimated using the NCEP and Mets-PC-derived binary definitions. In Cox proportional models, the HR (95% CI) for CVD events for 1-SD (standard deviation) of MetS-PC was 1.71 (1.54-1.90) (P &lt; 0.0001) overall after adjusting for potential confounders, and for each ethnicity, HRs were: Caucasian, 1.64 (1.39-1.94), Chinese, 1.39 (1.06-1.83), African, 1.67 (1.37-2.02), and Hispanic, 2.10 (1.66-2.65). Finally, when binary definitions were compared, HR for CVD events was 2.34 (1.91-2.87) for MetS-PC versus 1.79 (1.46-2.20) for NCEP MetS. In the Health ABC cohort, in a fully adjusted model, MetS-PC per 1-SD (Health ABC) remained associated with CVD events (HR = 1.21, 95%CI 1.12-1.32) overall, and for each ethnicity, Caucasian (HR = 1.24, 95%CI 1.12-1.39) and African Americans (HR = 1.16, 95%CI 1.01-1.32). Finally, when using a binary definition of MetS-PC (cut point 0.505) designed to match the NCEP definition in terms of prevalence in the Health ABC cohort (35%), the fully adjusted HR for CVD events was 1.39, 95%CI 1.17-1.64 compared with 1.46, 95%CI 1.23-1.72 using the NCEP definition. Conclusion. MetS-PC is a continuous measure of metabolic syndrome and was a better predictor of CVD events overall and in individual ethnicities. Additionally, a binary MetS-PC definition was better than the NCEP MetS definition in predicting incident CVD events in the MESA cohort, but this superiority was not evident in the Health ABC cohort

Greybody factor for a scalar field coupling to Einstein's tensor

We study the greybody factor and Hawking radiation for a scalar field coupling to Einstein's tensor in the background of Reissner-Nordstr\"om black hole in the low-energy approximation. We find that the presence of the coupling terms modifies the standard results in the greybody factor and Hawking radiation. Our results show that both the absorption probability and Hawking radiation increase with the coupling constant. Moreover, we also find that for the stronger coupling, the charge of black hole enhances the absorption probability and Hawking radiation of the scalar field, which is different from those of ones without coupling to Einstein's tensor in the black hole spacetime.Comment: 14 pages, 6 figures, Accepted by PL

Remnant gas in evolved circumstellar disks: Herschel PACS observations of 10-100 Myr old disk systems

We present Herschel PACS spectroscopy of the [OI] 63 micron gas-line for three circumstellar disk systems showing signs of significant disk evolution and/or planet formation: HR 8799, HD 377 and RX J1852.3-3700. [OI] is undetected toward HR 8799 and HD 377 with 3 sigma upper limits of 6.8 x 10^-18 W m^-2 and 9.9 x 10^-18 W m^-2 respectively. We find an [OI] detection for RX J1852.3-3700 at 12.3 +- 1.8 x 10^-18 W m^-2. We use thermo-chemical disk models to model the gas emission, using constraints on the [OI] 63 micron, and ancillary data to derive gas mass upper limits and constrain gas-to-dust ratios. For HD 377 and HR 8799, we find 3 sigma upper limits on the gas mass of 0.1-20 Mearth. For RX J1852.3-3700, we find two distinct disk scenarios that could explain the detection of [OI] 63 micron and CO(2-1) upper limits reported from the literature: (i) a large disk with gas co-located with the dust (16-500 AU), resulting in a large tenuous disk with ~16 Mearth of gas, or (ii) an optically thick gas disk, truncated at ~70 AU, with a gas mass of 150 Mearth. We discuss the implications of these results for the formation and evolution of planets in these three systems.Comment: Accepted for publication in ApJ, 8 pages ApJ style (incl. references), 2 figures, 4 table

Viscous Brane Cosmology with a Brane-Bulk Energy Interchange Term

We assume a flat brane located at y=0, surrounded by an AdS space, and consider the 5D Einstein equations when the energy flux component of the energy-momentum tensor is related to the Hubble parameter through a constant Q. We calculate the metric tensor, as well as the Hubble parameter on the brane, when Q is small. As a special case, if the brane is tensionless, the influence from Q on the Hubble parameter is absent. We also consider the emission of gravitons from the brane, by means of the Boltzmann equation. Comparing the energy conservation equation derived herefrom with the energy conservation equation for a viscous fluid on the brane, we find that the entropy change for the fluid in the emission process has to be negative. This peculiar effect is related to the fluid on the brane being a non-closed thermodynamic system. The negative entropy property for non-closed systems is encountered in other areas in physics also, in particular, in connection with the Casimir effect at finite temperature.Comment: 12 pages, latex, no figure

A Substellar Companion to the Intermediate-Mass Giant 11 Com

We report the detection of a substellar companion orbiting the intermediate-mass giant star 11 Com (G8 III). Precise Doppler measurements of the star from Xinglong station and Okayama Astrophysical Observatory (OAO) revealed Keplerian velocity variations with an orbital period of 326.03 +/- 0.32 days, a semiamplitude of 302.8 +/- 2.6 m/s, and an eccentricity of 0.231 +/- 0.005. Adopting a stellar mass of 2.7 +/- 0.3 M_solar, the minimum mass of the companion is 19.4 +/- 1.5 M_Jup, well above the deuterium burning limit, and the semimajor axis is 1.29 +/- 0.05 AU. This is the first result from the joint planet search program between China and Japan aiming at revealing statistics of substellar companions around intermediate-mass giants. 11 Com b emerged from 300 targets of the planet search program at OAO. The current detection rate of a brown dwarf candidate seems to be comparable to that around solar-type stars within orbital separations of $\sim$3 AU.Comment: 19 pages, 4 figures, accepted by Ap