Exoplanets and Stellar Physics

Abstract:

As a prerequisite for cosmological studies using adaptive optics techniques, we have begun to identify and characterize faint sources in the vicinity of bright stars at high Galactic latitudes. The initial phase of this work has been a program of Ks imaging conducted with SOFI at the ESO NTT. From observations of 42 southern fields evenly divided between the spring and autumn skies, we have identified 391 additional stars and 1589 galaxies lying at separations Δθ ≤ 60″ from candidate guide stars in the magnitude range 9.0 ≤ R ≤ 12.4. When analyzed as a "discrete deep field" with 131 arcmin2 area, our dataset gives galaxy number counts that agree with those derived previously over the range 16 ≤ Ks < 20.5. This consistency indicates that in the aggregate, our fields should be suitable for future statistical studies. We provide our source catalogue as a resource for users of large telescopes in the southern hemisphere.

Abstract:

The high-resolution optical spectra of the two X-ray active binaries RS CVn stars HD 113816 (IS Vir) and HD 119285 (V851 Cen) are analysed and their Na, Mg, Al, Si, Ca, Sc, Ti, Co and Ni contents determined, in the framework of a larger program of chemical analysis of RS CVn stellar atmosphere. The analysis of IS Vir and V851 Cen is performed with three different LTE methods. In the first one, abundances are derived for a large set of transitions (among which 28 Fe I lines, spanning a broad interval in excitation potential and equivalent width, and 6 Fe II transitions) using measured equivalent widths and Kurucz LTE model atmospheres as input for the MOOG software package. The input atmospheric parameters and abundances are iteratively modified until (i) the Fe I abundances exhibit no trend with excitation potential or equivalent width, (ii) Fe I and Fe II average abundances are the same and (iii) Fe and Alpha elements average abundances are consistent with the input values. The second method follows a similar approach, but uses a restricted line list (without the Fe I "low excitation potential" transitions) and relies on the B - V and V - I colour indices to determine the temperature. The third method uses the same restricted line list as the second method and relies on fitting the 6162 Å Ca I line wing profiles to derive the surface gravity. The reliability of these methods is investigated in the context of single line RS CVn stars. It is shown that the V - I photometric index gives, on a broader sample of stars, significantly cooler estimates of the effective temperature than the B - v index. All approaches give results in good agreement with each other, except the V - 1 based method. The analysis of IS Vir and V851 Cen results in both cases in their primaries being giant stars of near-solar metallicity. Their parameters as derived with the first method are respectively Teff = 4720 K, log g = 2.65, [Fe/H] = +0.04 and Teff = 4700 K, log g = 3.0 and [Fe/H] = -0.13. In the case of V851 Cen the derived iron content is significantly higher than a previous determination in the literature. Both stars exhibit relative overabundances of several elements (e.g. Ca) with respect to the solar mix.

Abstract:

We present a system for the exchange and handling of cold field masks in LUCIFER, the near infrared camera and spectrograph for the LBT. Inside the LUCIFER cryostat, 10 field-stop and long-slit masks, and 23 multi-slit masks are stored in a stationary and an exchangeable cabinet respectively. With LUCIFER at operating temperature, the exchangeable cabinet with its multi-slit masks can be transferred from the LUCIFER cryostat to an auxiliary cryostat, and a second cabinet harboring the newly made, pre-cooled masks can be transferred back to LUCIFER from. a second auxiliary cryostat. Inside LUCIFER, a robot transports the individual masks from their storage position in the cabinet to the focal plane, and inserts them in a mask mount where they are centered on two pins. The position accuracy of the masks in the focal plane is anticipated to be better than +/-10 mum. A mechanism which locks the masks in their cabinets and releases only the one connected to the transport robot permits mask exchange in arbitrary orientation of the cryostat.

Abstract:

The various deep ISOCAM surveys revealed a new class of infrared luminous galaxies which are characterized by a high rate of evolution and are found at redshifts of zsimilar to1. Based on our near-infrared low-resolution spectroscopy we find that these ISOCAM galaxies are dust-enshrouded star-forming galaxies. Here we report on the first spatially resolved H. velocity profiles of ISOCAM galaxies in the Hubble Deep Field South. We find that some of these systems are in fact extremely massive galaxies. The galaxies show an offset of 1.6+/-0.3 magnitude in the rest frame B-band when compared to the local Tully-Fisher relation.