Anton Norup Sørensen

The two-colour EMCCD instrument for the Danish 1.54 m telescope and SONG

We report on the implemented design of a two-colour instrument based on electron-multiplying CCD (EMCCD) detectors. This instrument is currently installed at the Danish 1.54 m telescope at ESO’s La Silla Observatory in Chile, and will be available at the SONG (Stellar Observations Network Group) 1m telescope node at Tenerife and at other SONG nodes as well. We present the software system for controlling the two-colour instrument and calibrating the high frame-rate imaging data delivered by the EMCCD cameras. An analysis of the performance of the Two-Colour Instrument at the Danish telescope shows an improvement in spatial resolution of up to a factor of two when doing shift-and-add compared with conventional imaging, and the possibility of doing high-precision photometry of EMCCD data in crowded fields. The Danish telescope, which was commissioned in 1979, is limited by a triangular coma at spatial resolutions below , and better results will thus be achieved at the near diffraction-limited optical system on the SONG telescopes, where spatial resolutions close to have been achieved. Regular EMCCD operations have been running at the Danish telescope for several years and produced a number of scientific discoveries, including microlensing detected exoplanets, detecting previously unknown variable stars in dense globular clusters, and discovering two rings around the small asteroid-like object (10199) Chariklo.

Detection of a Faint Optical Jet in 3C 120

We report the detection of an optical jet in the nearby Seyfert 1 radio galaxy 3C 120. The optical jet coincides with the well-known radio jet and emits continuum radiation (B, V, I) with a radio-to-optical spectral index of 0.65. There are no clear optical counterparts to the radio knots, although the optical condensation A of the galaxy, which includes the bright 4 radio knot, is found to be 12% polarized with the electric field vectors perpendicular to the jet. These findings indicate that 3C 120 contains the sixth known extragalactic optical synchrotron jet, quite similar in its properties to the jet of PKS 0521-36. The outer part of the jet is the faintest known optical jet and was discovered as the result of a dedicated effort to detect it. It is therefore possible that more optical jets can be discovered in systematic searches by combining deep imaging in the optical or near-infrared with careful galaxy subtraction methods.

Detection of the lensing galaxy for the double QSO HE 1104-1805

Abstract High angular resolution ground-based direct imaging (V, R, Ic) of the double QSO HE 1104–1805 has been obtained with the NOT and NTT telescopes. Analysis of these data led to the first detection of the lensing galaxy. Direct imaging of HE 1104–1805 has subsequently been carried out with the Planetary Camera (WFPC2) through the F555W (nearly Johnson V) and F814W (nearly Kron-Cousins Ic) filters onboard HST. These images confirm the presence of the deflector between the two lensed quasar components (A & B). Direct imaging of this system in the near infrared (IR) at 2.2 μm (K′), with IRAC-2b at the Cassegrain focus of the ESO/MPI 2.2 m telescope, indicates that the additional component is indeed a very red extended object with magnitude K ≈ 16.5. We present deconvolutions of the HST and IR images using the 2-channel PLUCY method. From the HST observations, we also report very accurate relative positions and brightnesses of the QSO components. By comparison between the ground-based and the HST observations, from February–March 1994 to November 1995, we possibly detect the fading of component A by ∼0.3 magnitudes in the optical and a corresponding fading of B by about half this value. The observed monotonic decrease of the magnitude difference between B and A as a function of wavelength is consistent with a partial amplification of the A component by microlensing. Evolutionary models for galaxies show that, in order to produce the observed colour indices V − Ic > 2 and 4 11 h 50 M ⊙ L ⊙ ) for the galaxy is large but does not imply an excess of dark matter with respect to other well known lensing galaxies.

Observations of the radial velocity of the Sun as measured with the novel SONG spectrograph: results from a 1-week campaign

Deployment of the prototype node of the SONG project took place in April 2012 at Observatorio del Teide (Canary Islands). Its key instrument (echelle spectrograph) was installed and operational a few weeks later while its 1 m feeding telescope suffered a considerable delay to meet the required specifications. Using a fibre-feed, solar light could be fed to the spectrograph and we carried out a 1-week observing campaign in June 2012 to evaluate its performance for measuring precision radial velocities. In this work we present the first results of this campaign by comparing the sensitivity of the SONG spectrograph with other helioseismology reference instruments (Mark-I and GOLF) when simultaneous data are considered.

Stellar Observations Network Group: The prototype is nearly ready

The prototype telescope and instruments for the Stellar Observations Network Group (SONG) are nearing completion at the Observatorio del Teide on Tenerife. In this contribution we describe the current status (autumn 2013) of the telescope and its instrumentation. Preliminary performance characteristics are presented for the high-resolution spectrograph based on daytime observations of the Sun and a 4 hour test series obtained for the sub-giant β Aquilae.

SWIR at The Nordic Optical Telescope : NOTCam

We describe the Nordic Optical Telescopes facility short- wavelength IR instrument, NOTCam. The instrument will be capable of wide-field and high-resolution imaging, long-slit and multi-object grism spectroscopy, coronography, and imaging-and spectro-polarimetry. First light will be in mid- 2000. Current progress is summarized and some problems we have encountered and overcome are discussed.

Using KAF-4201 CCDs for astronomy

The work horse detector for cameras built at Copenhagen University Observatory has for several years been a Loral 2K×2K, 15 micron pixel CCD. The requirement for better spatial sampling in certain projects has forced us to look for alternatives to this detector. Therefore, we have built two cameras using the frontside illuminated Kodak KAF-4201 CCD, with 2K×2K, 9 micron pixels. While this CCD fulfils our sampling requirements, trade-offs are made in other areas. In this presentation, the potential of the KAF-4201 as an astronomical imager is evaluated.

An Interferometric Method for Measurement of the Detector MTF

We present an interferometric method by which the MTF of an array detector is measured directly. The method is not relying on high quality optics and precise alignment/focusing and it is therefore straightforward to set up.

The mass and age of the first SONG target: the red giant 46 LMi

Context. The Stellar Observation Network Group (SONG) is an initiative to build a worldwide network of 1m telescopes with high-precision radial-velocity spectrographs. Here we analyse the first radial-velocity time series of a red-giant star measured by the SONG ntelescope at Tenerife. The asteroseismic results demonstrate a major increase in the achievable precision of the parameters for red-giant nstars obtainable from ground-based observations. Reliable tests of the validity of these results are needed, however, before the accuracy nof the parameters can be trusted. n n Aims. We analyse the first SONG time series for the star 46 LMi, which has a precise parallax and an angular diameter measured from interferometry, and therefore a good determination of the stellar radius. We use asteroseismic scaling relations to obtain an accurate mass, and modelling to determine the age. n n Methods. A 55-day time series of high-resolution, high S/N spectra were obtained with the first SONG telescope. We derive the asteroseismic parameters by analysing the power spectrum. To give a best guess on the large separation of modes in the power spectrum, we have applied a new method which uses the scaling of Kepler red-giant stars to 46 LMi. n n Results. Several methods have been applied: classical estimates, seismic methods using the observed time series, and model calculations to derive the fundamental parameters of 46 LMi. Parameters determined using the different methods are consistent within the uncertainties. We find the following values for the mass M (scaling), radius R (classical), age (modelling), and surface gravity (combining mass and radius): M = 1.09 ± 0.04 M⊙, R = 7.95 ± 0.11 R⊙ age t = 8.2 ± 1.9 Gy, and log g = 2.674 ± 0.013. n n Conclusions. The exciting possibilities for ground-based asteroseismology of solar-like oscillations with a fully robotic network have been illustrated with the results obtained from just a single site of the SONG network. The window function is still a severe problem which will be solved when there are more nodes in the network.

How to test NISP instrument for EUCLID mission in laboratory

The ESA mission Euclid is designed to explore the dark side of the Universe. The NISP (Near Infrared Spectro- Photometer) is one of its two instruments operating in the near-IR spectral region (0.9-2μm), that will be fully integrated and tested at Laboratory d’Astrophysique de Marseille (LAM) under vacuum and thermal conditions. The test campaign will regroup functional tests, performance tests, calibration procedure validation and observations scenario test. One of the main objectives of the test campaign will be the measurement of the focus position of NISP with respect to the EUCLID object plane. To achieve these tests campaign, a global Ground Support Equipment (GSE) called the Verification Ground System (VGS) has to be developed. It will be a complex set of GSE integrated in ERIOS chamber made of: a telescope simulator to simulate the EUCLID telescope and to inject light into NISP, a thermal environment to be used for NISP thermal balance and verification, a sets of mechanical interfaces to align all the parts into ERIOS chamber, the NISP Electrical GSE (EGSE) to control the instrument during the test and a metrology system to measure the positions of the components during the test. We will present the preliminary design and concepts of the VGS and we will show the main difficulties we have to deal with: design of thermal environment at 80K with 4mK stability, the development of a metrology system in vacuum, knowledge of the focus position within 150μm in cold, etc. The main objectives of the NISP test will be explained and how the VGS responds to the test requirement.