6 research outputs found

    High Precision Radial Velocity Measurements in the Infrared: A First Assessment of the RV Stability of CRIRES

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    High precision radial velocity (RV) measurements in the near infrared are on high demand, especially in the context of exoplanet search campaigns shifting their interest to late type stars in order to detect planets with ever lower mass or targeting embedded pre-main-sequence objects. ESO is offering a new spectrograph at the VLT -- CRIRES -- designed for high resolution near-infrared spectroscopy with a comparably broad wavelength coverage and the possibility to use gas-cells to provide a stable RV zero-point. We investigate here the intrinsic short-term RV stability of CRIRES, both with gas-cell calibration data and on-sky measurements using the absorption lines of the Earth's atmosphere imprinted in the source spectrum as a local RV rest frame. Moreover, we also investigate for the first time the intrinsic stability of telluric lines at 4100 nm for features originating in the lower troposphere. Our analysis of nearly 5 hours of consecutive observations of MS Vel, a M2II bright giant centred at two SiO first overtone band-heads at 4100 nm, demonstrates that the intrinsic short-term stability of CRIRES is very high, showing only a slow and fully compensateable drift of up to 60 m/s after 4.5 hours. The radial velocity of the telluric lines is constant down to a level of approx. +/- 10 m/s (or 7/1000 of one pixel). Utilising the same telluriclines as a rest frame for our radial velocity measurements of the science target, we obtain a constant RV with a precision of approx. +/- 20 m/s for MS Vel as expected for a M-giant.Comment: 12 pages, 6 figures, accepted by A&

    METIS - the Mid-infrared E-ELT Imager and Spectrograph

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    METIS, the Mid-infrared ELT Imager and Spectrograph (formerly called MIDIR), is a proposed instrument for the European Extremely Large Telescope (E-ELT), currently undergoing a phase-A study. The study is carried out within the framework of the ESO-sponsored E-ELT instrumentation studies. METIS will be designed to cover the E-ELT science needs at wavelengths longward of 3um, where the thermal background requires different operating schemes. In this paper we discuss the main science drivers from which the instrument baseline has been derived. Specific emphasis has been given to observations that require very high spatial and spectral resolution, which can only be achieved with a ground-based ELT. We also discuss the challenging aspects of background suppression techniques, adaptive optics in the mid-IR, and telescope site considerations. The METIS instrument baseline includes imaging and spectroscopy at the atmospheric L, M, and N bands with a possible extension to Q band imaging. Both coronagraphy and polarimetry are also being considered. However, we note that the concept is still not yet fully consolidated. The METIS studies are being performed by an international consortium with institutes from the Netherlands, Germany, France, United Kingdom, and Belgium.Comment: 15 pages, to be published in Proc SPIE 7014: Ground-based & Airborne Instrumentation for Astronomy I

    The Evolution of Disk Winds from a Combined Study of Optical and Infrared Forbidden Lines

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    We analyze high-resolution (Δv≤10 km s-1) optical and infrared spectra covering the [O I] λ6300 and [Ne II] 12.81 μm lines from a sample of 31 disks in different evolutionary stages. Following work at optical wavelengths, we use Gaussian profiles to fit the [Ne II] lines and classify them into high-velocity component (HVC) or lowvelocity component (LVC) if the line centroid is more or less blueshifted than 30 km s-1 with respect to the stellar radial velocity, respectively. Unlike for the [O I], where an HVC is often accompanied by an LVC, all 17 sources with an [Ne II] detection have either an HVC or an LVC. [Ne II] HVCs are preferentially detected toward high accretors (Ṁacc > 10-8 Me⊙ yr-1), while LVCs are found in sources with low Ṁacc, low [O I] luminosity, and large infrared spectral index (n13-31). Interestingly, the [Ne II] and [O I] LVC luminosities display an opposite behavior with n13-31: as the inner dust disk depletes (higher n13-31), the [Ne II] luminosity increases while the [O I] weakens. The [Ne II] and [O I] HVC profiles are generally similar, with centroids and FWHMs showing the expected behavior from shocked gas in microjets. In contrast, the [Ne II] LVC profiles are typically more blueshifted and narrower than the [O I] profiles. The FWHM and centroid versus disk inclination suggest that the [Ne II] LVC predominantly traces unbound gas from a slow, wide-angle wind that has not lost completely the Keplerian signature from its launching region. We sketch an evolutionary scenario that could explain the combined [O I] and [Ne II] results and includes screening of hard (∼1 keV) X-rays in inner, mostly molecular, MHD winds