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The study of elemental abundances in cool stars via atomic lines in the optical region is made difficult by stellar molecular absorption. At infrared wavelengths this problem is diminished, but ground-based observations suffer from absorption by the earth's atmosphere. Fortunately, there are spectral windows through which we can observe. We have explored several such windows in the spectral region

Stars ascending the red giant branch develop an inversion in mean molecular weight (mu) owing to the burning of He-3 in the region immediately above their hydrogen-burning shells. This inversion may drive thermohaline mixing and thereby be responsible for the extra mixing which is observationally indicated on the red giant branch. In this paper, we investigate the physical influences that determin

We present the results of a weakly modeled burst search for gravitational waves from mergers of nonspinning intermediate mass black holes in the total mass range 100-450 M-circle dot and with the component mass ratios between 1: and 4:1. The search was conducted on data collected by the LIGO and Virgo detectors between November of 2005 and October of 2007. No plausible signals were observed by the

We study the chemical abundances of the strontium filament found in the ejecta of eta Carinae. In particular, we derive the abundances of iron-peak elements from the spectra of their singly ionized ions present in the optical/infrared (IR) spectra. In this paper we analyse the spectrum of Mn II using a new non-local thermodynamic equilibrium (non-LTE) model for this system. In constructing this mo

Aims. We seek to provide 2MASS and OGLE identifications and coordinates for all stars in the finding chart published by Arp (1965, ApJ, 141, 43). This chart covers the low extinction area around NGC 6522, also known as Baade's window, at coordinates (l, b) = (1.02, -3.92). Methods. A cross correlation, using numerical techniques, was performed between a scan of the original finding chart from Arp

To improve the mechanical characteristics of actively controlled continuous faceplate deformable mirrors in adaptive optics, a strategy for reducing crosstalk between adjacent actuators and for suppressing low-order eigenmodes is proposed. The strategy can be seen as extending Saint-Venant's principle beyond the static case, for small local families of actuators. An analytic model is presented, fr

We discuss resonance-enhanced two-photon ionization (RETPI) and presentschemes of successive RETPI of the elements C, N, and O in nebulae.RETPI is activated by intrinsic radiation stored in the form of trappedspectral lines of HI, HeI, and HeII in the optically thick nebula. Therate of this two-step photoionization is comparable with or exceeds thelow recombination rate of the photoions formed in

Analyses of their internal stellar kinematics imply that the dwarf spheroidal (dSph) companion galaxies to the Milky Way are among the most dark matter-dominated systems known. Should there be significant dark matter in the form of faint stars in these systems, the stellar luminosity function must be very different from that of a similar metallicity globular cluster, for which there is no evidence

Gaia is ESA’s space astrometry mission with a foreseen launch date in early 2012. Its main objective is to perform a stellar census of the 1000 Million brightest objects in our galaxy (completeness to V=20 mag) from which an astrometric catalog of micro-arcsec level accuracy will be constructed. A key element in this endeavor is the Astrometric Global Iterative Solution (AGIS). A core part of AGIS

Context. The Si III] 1892 angstrom intercombination line shows an anomalously high intensity in spectra of the radiation-rich Weigelt blobs in the vicinity of Eta Carinae. The line disappears during the 100 days long spectral events occurring every 5.5 years. Aims. The aim is to investigate whether resonance-enhanced two-photon ionization (RETPI) is a plausible excitation mechanism for the Si III]

High-order laser guide star performance for the Euro50 telescope is analyzed. Focus anisoplanatism residual errors using multiple LGSs are obtained by numerical simulations. Results calculated for annual mean conditions at the La Palma site show that, considering only focus anisoplanatism, it will be possible to obtain a Strehl ratio of 0.72 similar to 0.82 at 2.2 mum using 13 LGSs. A Strehl ratio

The globular cluster M15 was observed on three occasions with the High Resolution Camera on- board Chandra in 2001 in order to investigate the X- ray source population in the cluster centre. After subtraction of the two bright central sources, four faint sources were identified within 50 arcsec of the core. One of these sources is probably the planetary nebula K648, making this the first positive

We report a new determination of [O/Fe, the relative logarithmicabundance of O/Fe with respect to the Sun, for the very metal-poor starBD+23 3130 ([Fe/H=-2.6). The value was derived from the forbidden line[O I at 630 nm and from six weak Fe II lines, with a S/N ratiosubstantially larger than those obtained before, thanks to theefficiency of the VLT-UVES instrument at Paranal. We obtain[O/Fe=0.71+/

We report a strong prepulse dependence of the emission of X-rays from plasmas created by 150 fs Ti:sapphire laser pulses on solids. The laser pulses were focused onto plane samples of aluminium and vanadium with a main pulse power density of about 2.5 x 10(16) W cm(-2). By splitting off a portion of the main pulse we were able to generate a prepulse whose delay and intensity were variable relative

We performed a detailed study of the ratio of low-alpha to high-alpha stars in the Galactic halo as observed by the Gaia-ESO Survey. Using a sample of 381 metal-poor stars from the second internal data release, we found that the value of this ratio did not show evidence of systematic trends as a function of metallicity, surface gravity, Galactic latitude, Galactic longitude, height above the Galac

In this paper, we report on the formation of magnetically levitating accretion disks around supermassive black holes (SMBHs). The structure of these disks is calculated by numerically modeling tidal disruption of magnetized interstellar gas clouds. We find that the resulting disks are entirely supported by the pressure of the magnetic fields against the component of gravitational force directed pe

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The intensity-calibrated spectra of W II have been recorded in the spectral interval 23 000-51 300 cm(-1) (1950-4350 angstrom), using the FT500 UV Fourier Transform Spectrometer at Lund Observatory. Combining the intensity data in this work with lifetimes previously measured using the time-resolved laser-induced-fluorescence (TR-LIF) technique resulted in transition probabilities and log gf values