140 research outputs found
A comprehensive examination of the Eps Eri system -- Verification of a 4 micron narrow-band high-contrast imaging approach for planet searches
Due to its proximity, youth, and solar-like characteristics with a spectral
type of K2V, Eps Eri is one of the most extensively studied systems in an
extrasolar planet context. Based on radial velocity, astrometry, and studies of
the structure of its circumstellar debris disk, at least two planetary
companion candidates to Eps Eri have been inferred in the literature (Eps Eri
b, Eps Eri c). Some of these methods also hint at additional companions
residing in the system. Here we present a new adaptive optics assisted
high-contrast imaging approach that takes advantage of the favourable planet
spectral energy distribution at 4 microns, using narrow-band angular
differential imaging to provide an improved contrast at small and intermediate
separations from the star. We use this method to search for planets at orbits
intermediate between Eps Eri b (3.4 AU) and Eps Eri c (40 AU). The method is
described in detail, and important issues related to the detectability of
planets such as the age of Eps Eri and constraints from indirect measurements
are discussed. The non-detection of companion candidates provides stringent
upper limits for the masses of additional planets. Using a combination of the
existing dynamic and imaging data, we exclude the presence of any planetary
companion more massive than 3 Mjup anywhere in the Eps Eri system.
Specifically, with regards to the possible residual linear radial velocity
trend, we find that it is unlikely to correspond to a real physical companion
if the system is as young as 200 Myr, whereas if it is as old as 800 Myr, there
is an allowed semi-major axis range between about 8.5 and 25 AU.Comment: 11 pages, 8 figures, A&A accepte
Mid-infrared astronomy with the E-ELT: Performance of METIS
We present results of performance modelling for METIS, the Mid-infrared
European Extremely Large Telescope (E-ELT) Imager and Spectrograph. Designed by
a consortium of NOVA (Netherlands), UK Astronomy Technology Centre (UK), MPIA
Heidelberg (Germany), CEA Saclay (France) and KU Leuven (Belgium), METIS will
cover the atmospheric windows in L, M and N-band and will offer imaging,
medium-resolution slit spectroscopy (R~1000-3000) and high-resolution integral
field spectroscopy (R~100,000). Our model uses a detailed set of input
parameters for site characteristics and atmospheric profiles, optical design,
thermal background and the most up-to-date IR detector specifications. We show
that METIS will bring an orders-of-magnitude level improvement in sensitivity
and resolution over current ground-based IR facilities, bringing mid-IR
sensitivities to the micro-Jansky regime. As the only proposed E-ELT instrument
to cover this entire spectral region, and the only mid-IR high-resolution
integral field unit planned on the ground or in space, METIS will open up a
huge discovery space in IR astronomy in the next decade.Comment: 13 pages, submitted to SPIE Proceedings vol. 7735, Ground-based and
Airborne Instrumentation for Astronomy III (2010). Simulation code available
at http://tinyurl.com/metis-sen
The Arches Cluster - Evidence for a Truncated Mass Function?
We have analyzed high-resolution, adaptive optics (AO) HK observations of the
Arches cluster obtained with NAOS/CONICA. With a spatial resolution of 84 mas,
the cluster center is uniquely resolved. From these data the present-day mass
function (MF) of Arches is derived down to about 4 Msun. The integrated MF as
well as the core and 2nd annulus MFs are consistent with a turn-over at 6-7
Msun. This turn-over indicates severe depletion of intermediate and low-mass
stars in the Arches cluster, possibly caused by its evolution in the Galactic
Center environment. The Arches MF represents the first resolved observation of
a starburst cluster exhibiting a low-mass truncated MF. This finding has severe
implications for stellar population synthesis modelling of extragalactic
starbursts, the derivation of integrated properties such as the total mass of
star clusters in dense environments, the survival of low-mass remnants from
starburst populations, and chemical enrichment during starburst phases.Comment: aastex preprint, 14 pages, 4 figures, accepted by ApJ Letter
GSOC SoE-Editor 2.0 - A Generic Sequence of Events Tool
At the German Space Operations Center (GSOC) two applications had been developed for scheduling operations of Launch and Early Orbit Phases (LEOP), Commissioning Phases or special operations campaigns (e.g. software upload, special orbit maneuvers, etc.): one for low earth orbit (LEO) and one for medium (MEO) and geostationary earth orbit (GEO). The experiences of these tools were now merged with the scheduling capabilities of GSOC's generic mission planning application Pinta (Program for interactive timeline analysis), its scheduling library Plato (Planning tool) and the GSOC web based timeline display TimOnWeb
An apodizing phase plate coronagraph for VLT/NACO
We describe a coronagraphic optic for use with CONICA at the VLT that
provides suppression of diffraction from 1.8 to 7 lambda/D at 4.05 microns, an
optimal wavelength for direct imaging of cool extrasolar planets. The optic is
designed to provide 10 magnitudes of contrast at 0.2 arcseconds, over a
D-shaped region in the image plane, without the need for any focal plane
occulting mask.Comment: 9 pages, 5 figures, to appear in Proc. SPIE Vol. 773
Status and new operation modes of the versatile VLT/NACO
This paper aims at giving an update on the most versatile adaptive optics fed
instrument to date, the well known and successful NACO . Although NACO is only
scheduled for about two more years at the Very Large Telescope (VLT), it keeps
on evolving with additional operation modes bringing original astronomical
results. The high contrast imaging community uses it creatively as a test-bench
for SPHERE and other second generation planet imagers. A new visible wavefront
sensor (WFS) optimized for Laser Guide Star (LGS) operations has been installed
and tested, the cube mode is more and more requested for frame selection on
bright sources, a seeing enhancer mode (no tip/tilt correction) is now offered
to provide full sky coverage and welcome all kind of extragalactic
applications, etc. The Instrument Operations Team (IOT) and Paranal engineers
are currently working hard at maintaining the instrument overall performances
but also at improving them and offering new capabilities, providing the
community with a well tuned and original instrument for the remaining time it
is being used. The present contribution delivers a non-exhaustive overview of
the new modes and experiments that have been carried out in the past months.Comment: 10 pages, 7 figures, SPIE 2010 Astronomical Instrumentation
Proceedin
Autorinnen und Autoren
Am 13. Mai 2011 jährte sich die Einweihung des heutigen Hauptgebäudes der Universität Hamburg an der Edmund-Siemers-Allee zum 100. Mal. Am selben Tag wurde das 1999 begonnene Programm zur Benennung seiner sieben Hörsäle nach herausragenden, in der NS-Zeit vertriebenen Wissenschaftlerinnen und Wissenschaftlern abgeschlossen. (Die bei dieser Gelegenheit gehaltenen Reden werden in den Hamburger Universitätsreden Neue Folge 18, 100 Jahre Hauptgebäude der Universität Hamburg, dokumentiert.)
Aus doppeltem Anlass also erscheint dieses Buch, das neben einer Einführung in die facettenreiche Geschichte des Gebäudes erstmals Porträts der sieben Namensgeber der Hörsäle versammelt: biographische und werkanalytische Annäherungen an den Philosophen Ernst Cassirer, den Kunsthistoriker Erwin Panofsky, die Germanistin Agathe Lasch, den Mathematiker Emil Artin, die Juristin Magdalene Schoch, den Völkerrechtler und Friedensforscher Albrecht Mendelssohn Bartholdy sowie den Sozialökonomen Eduard Heimann.
Gemeinsam mit den 2010 vor dem Kuppelbau verlegten „Stolpersteinen“ bilden die Hörsaalbenennungen ein Ensemble, durch welches das Hauptgebäude die Universität Hamburg auch als zentraler Gedächtnisort in besonderer Weise repräsentiert.
Der Film „BLICK RICHTEN“ vom Medienkompetenzzentrum der Universität Hamburg ist als DVD dem Buch beigelegt.
Sie können den Film durch Aktivieren des Links „video.html“ unter „Frei verfügbarer Volltext“ abspielen oder diesen direkt auf der Webseite Lecture2Go (http://lecture2go.uni-hamburg.de/veranstaltungen/-/v/12112) betrachten
Suppressing Speckle Noise for Simultaneous Differential Extrasolar Planet Imaging (SDI) at the VLT and MMT
We discuss the instrumental and data reduction techniques used to suppress
speckle noise with the Simultaneous Differential Imager (SDI) implemented at
the VLT and the MMT. SDI uses a double Wollaston prism and a quad filter to
take 4 identical images simultaneously at 3 wavelengths surrounding the 1.62 um
methane bandhead found in the spectrum of cool brown dwarfs and gas giants. By
performing a difference of images in these filters, speckle noise from the
primary can be significantly attenuated, resulting in photon noise limited data
past 0.5''. Non-trivial data reduction tools are necessary to pipeline the
simultaneous differential imaging. Here we discuss a custom algorithm
implemented in IDL to perform this reduction. The script performs basic data
reduction tasks but also precisely aligns images taken in each of the filters
using a custom shift and subtract routine. In our survey of nearby young stars
at the VLT and MMT (see Biller et al., this conference), we achieved H band
contrasts >25000 (5 sigma Delta F1(1.575 um) > 10.0 mag, Delta H > 11.5 mag for
a T6 spectral type object) at a separation of 0.5" from the primary star. We
believe that our SDI images are among the highest contrast astronomical images
ever made from ground or space for methane rich companions.Comment: 5 pages, 3 figures, 1 table. Presented at IAU Colloquium 200, Direct
Imaging of Exoplanets: Science and Technique
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