Core Excited Fano-Resonances in Exotic Nuclei

Fano-resonances are investigated as a new continuum excitation mode in exotic nuclei. By theoretical model calculations we show that the coupling of a single particle elastic channel to closed core-excited channels leads to sharp resonances in the low-energy continuum. A signature for such bound states embedded in the continuum (BSEC) are characteristic interference effects leading to asymmetric line shapes. Following the quasiparticle-core coupling model we consider the coupling of 1-QP (one-quasiparticle) and 3-QP components and find a number of long-living resonance structures close to the particle threshold. Results for 15C are compared with experimental data, showing that the experimentally observed spectral distribution and the interference pattern are in qualitative agreement with a BSEC interpretation.Comment: 11 pages, 1 figur

Molecular gas associated with IRAS 10361-5830

We analyze the distribution of the molecular gas and the dust in the molecular clump linked to IRAS 10361-5830, located in the environs of the bubble-shaped HII region Gum 31 in the Carina region, with the aim of determining the main parameters of the associated material and investigating the evolutionary state of the young stellar objects identified there. Using the APEX telescope, we mapped the molecular emission in the J=3-2 transition of three CO isotopologues, 12CO, 13CO and C18O, over a 1.5' x 1.5' region around the IRAS position. We also observed the high density tracers CS and HCO+ toward the source. The cold dust distribution was analyzed using submillimeter continuum data at 870 \mu\ obtained with the APEX telescope. Complementary IR and radio data at different wavelengths were used to complete the study of the ISM. The molecular gas distribution reveals a cavity and a shell-like structure of ~ 0.32 pc in radius centered at the position of the IRAS source, with some young stellar objects (YSOs) projected onto the cavity. The total molecular mass in the shell and the mean H$_2$ volume density are ~ 40 solar masses and ~(1-2) x 10$^3$ cm$^{-3}$, respectively. The cold dust counterpart of the molecular shell has been detected in the far-IR at 870 \mu\ and in Herschel data at 350 \mu. Weak extended emission at 24 \mu\ from warm dust is projected onto the cavity, as well as weak radio continuum emission. A comparison of the distribution of cold and warm dust, and molecular and ionized gas allows us to conclude that a compact HII region has developed in the molecular clump, indicating that this is an area of recent massive star formation. Probable exciting sources capable of creating the compact HII region are investigated. The 2MASS source 10380461-5846233 (MSX G286.3773-00.2563) seems to be responsible for the formation of the HII region.Comment: Accepted in A&A. 11 pages, 10 Postscript figure

Molecular gas in the northern nucleus of Mrk273: Physical and chemical properties of the disk and its outflow

Aiming to characterise the properties of the molecular gas in the ultraluminous infrared galaxy Mrk273 and its outflow, we used the NOEMA interferometer to image the dense gas molecular tracers HCN, HCO+, HNC, HOC+ and HC3N at 86GHz and 256GHz with angular resolutions of 4.9x4.5 arcsec (3.7x3.4 kpc) and 0.61x0.55 arcsec (460x420 pc). We also modelled the flux of several H2O lines observed with Herschel using a radiative transfer code that includes excitation by collisions as well as by far-infrared photons. The disk of the Mrk273 north nucleus has two components with decoupled kinematics. The gas in the outer parts (1.5 kpc) rotates with a south-east to north-west direction, while in the inner disk (300 pc) follows a north-east to south-west rotation. The central 300 pc, which hosts a compact starburst region, is filled with dense and warm gas, contains a dynamical mass of (4-5)x10^9M_sun, a luminosity of L'_HCN=(3-4)x10^8 K km/s pc^2, and a dust temperature of 55 K. At the very centre, a compact core with R~50 pc has a luminosity of L_IR=4x10^11L_sun (30% of the total infrared luminosity), and a dust temperature of 95 K. The core is expanding at low velocities ~50-100 km/s, probably affected by the outflowing gas. We detect the blue-shifted component of the outflow, while the red-shifted counterpart remains undetected in our data. Its cold and dense phase reaches fast velocities up to ~1000 km/s, while the warm outflowing gas has more moderate maximum velocities of ~600 km/s. The outflow is detected as far as 460 pc from the centre in the northern direction, and has a mass of dense gas <8x10^8M_sun. The difference between the position angles of the inner disk (~70 degree) and the outflow (~10 degree) indicates that the outflow is likely powered by the AGN, and not by the starburst. Regarding the chemistry, we measure an extremely low HCO+/HOC+ ratio of 10+-5 in the inner disk of Mrk273.Comment: Accepted for publication in A&A. 21 pages, 17 figures, 7 tables, and a lot of interesting tex

Sub-au imaging of water vapour clouds around four Asymptotic Giant Branch stars

We present MERLIN maps of the 22-GHz H2O masers around four low-mass late-type stars (IK Tau U Ori, RT Vir and U Her), made with an angular resolution of ~ 15 milliarcsec and a velocity resolution of 0.1 km s-1. The H2O masers are found in thick expanding shells with inner radii ~ 6 to 16 au and outer radii four times larger. The expansion velocity increases radially through the H2O maser regions, with logarithmic velocity gradients of 0.5--0.9. IK Tau and RT Vir have well-filled H2O maser shells with a spatial offset between the near and far sides of the shell, which suggests that the masers are distributed in oblate spheroids inclined to the line of sight. U Ori and U Her have elongated poorly-filled shells with indications that the masers at the inner edge have been compressed by shocks; these stars also show OH maser flares. MERLIN resolves individual maser clouds, which have diameters of 2 -- 4 au and filling factors of only ~ 0.01 with respect to the whole H2O maser shells. The CSE velocity structure gives additional evidence the maser clouds are density bounded. Masing clouds can be identified over a similar timescale to their sound crossing time (~2 yr) but not longer. The sizes and observed lifetimes of these clouds are an order of magnitude smaller than those around red supergiants, similar to the ratio of low-mass:high-mass stellar masses and sizes. This suggests that cloud size is determined by stellar properties, not local physical phenomena in the wind.Comment: 21 pages, including 14 figures and 8 tables. Accepted for publication in MNRA

Parameters of the crystalline undulator and its radiation for particular experimental conditions

We report the results of theoretical and numerical analysis of the crystalline undulators planned to be used in the experiments which are the part of the ongoing PECU project [1]. The goal of such an analysis was to define the parameters (different from those pre-set by the experimental setup) of the undulators which ensure the highest yield of photons of specified energies. The calculations were performed for 0.6 and 10 GeV positrons channeling through periodically bent Si and Si$_{1-x}$Ge$_x$ crystals.Comment: 13 pages, 8 figures, submitted to SPI