Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

Atomic oxygen TALIF measurements in an atmospheric-pressure microwave plasma jet with in situ xenon calibration

Two-photon absorption laser-induced fluorescence (TALIF) is used to measure the absolute density of atomic oxygen (O) in a coaxial microwave jet in ambient air at atmospheric pressure, operated with a mixture of He and a few per cent of air. The TALIF signal is calibrated using a gas mixture containing Xe. A novel method to perform calibration in situ, at atmospheric pressure, is introduced. The branching ratios of several Xe mixtures are reported, to enable us to perform the Xe calibration without the need for a vacuum vessel. The O densities are measured spatially resolved, and as a function of admixed air to the He, and microwave power. The electron density and temperatures are measured using Thomson scattering, and the N-2 and O-2 densities are measured using Raman scattering. O densities are found to have a maximum of (4-6) x 10(22) m(-3), which indicate that O-2 is close to fully dissociated in the plasma. This is confirmed by the Raman scattering measurements. O is found to recombine mainly into species other than O-2 in the afterglow, which is suggested to consist of O-3 and oxidized components of NO

The effect of collisional quenching of the O 3p 3 P J state on the determination of the spatial distribution of the atomic oxygen density in an APPJ operating in ambient air by TALIF

The spatial profile of the absolute atomic oxygen density is obtained by two-photon absorption laser-induced fluorescence (TALIF) in an Ar+2% air cold atmospheric pressure plasma jet (APPJ) operating in ambient air. The varying air concentration in the jet effluent which contributes to the collisional quenching of the O 3p 3PJ state, pumped by the laser, strongly influences the recorded TALIF signal under the present experimental conditions. The spatially resolved air densities obtained from Raman scattering measurements have been reported in our previous work (van Gessel et al 2013 Appl. Phys. Lett. 103 064103). These densities allow us to calculate the spatially dependent collisional quenching rate for the O 3p 3PJ state and reconstruct the spatial O density profile from the recorded TALIF signal. Significant differences between the TALIF intensity profile and the actual O density profile for the investigated experimental conditions are found

The effect of collisional quenching of the O 3p 3 P J state on the determination of the spatial distribution of the atomic oxygen density in an APPJ operating in ambient air by TALIF

The spatial profile of the absolute atomic oxygen density is obtained by two-photon absorption laser-induced fluorescence (TALIF) in an Ar+2% air cold atmospheric pressure plasma jet (APPJ) operating in ambient air. The varying air concentration in the jet effluent which contributes to the collisional quenching of the O 3p 3PJ state, pumped by the laser, strongly influences the recorded TALIF signal under the present experimental conditions. The spatially resolved air densities obtained from Raman scattering measurements have been reported in our previous work (van Gessel et al 2013 Appl. Phys. Lett. 103 064103). These densities allow us to calculate the spatially dependent collisional quenching rate for the O 3p 3PJ state and reconstruct the spatial O density profile from the recorded TALIF signal. Significant differences between the TALIF intensity profile and the actual O density profile for the investigated experimental conditions are found

The spreading of inkjet-printed droplets with varying polymer molar mass on a dry solid substratery Solid Substrate

An experimental study on the spreading of inkjet printed droplets of a polystyrene/toluene solution with varied molar masses on solid dry surfaces is presented. The polymer's number- averaged molar mass was varied between 1.5 and 545 kDa, which also caused a variation in the viscosity from 0.6 to 1.7 mPa· s. The results were compared with theoretical models for dro plet spreading and were found to fit with an error between 2 and 20% with the predictions. Further more, the in-flight evaporation of the free-falling droplet was investigated for polystyrene/toluene solutions that have a constant vapor pressure by printing from a systematically increased height. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA

The spreading of inkjet-printed droplets with varying polymer molar mass on a dry solid substratery Solid Substrate

An experimental study on the spreading of inkjet printed droplets of a polystyrene/toluene solution with varied molar masses on solid dry surfaces is presented. The polymer's number- averaged molar mass was varied between 1.5 and 545 kDa, which also caused a variation in the viscosity from 0.6 to 1.7 mPa· s. The results were compared with theoretical models for dro plet spreading and were found to fit with an error between 2 and 20% with the predictions. Further more, the in-flight evaporation of the free-falling droplet was investigated for polystyrene/toluene solutions that have a constant vapor pressure by printing from a systematically increased height. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA