R. Siebenmorgen
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View article: Luminosity Distance and Extinction by Submicrometer-sized Grains
Luminosity Distance and Extinction by Submicrometer-sized Grains Open
The distance to the stars is a fundamental parameter, which is determined via two primary methods—parallax and luminosity. While the parallax is a direct trigonometric method, the luminosity distance is usually influenced by interstellar e…
View article: Progress on FORS-Up: the first instrument using ELT technologies
Progress on FORS-Up: the first instrument using ELT technologies Open
ESO is in the process of upgrading one of the two FORS (FOcal Reducer/low dispersion Spectrograph) instruments - a multi-mode (imaging, polarimetry, long-slit, and multi-object spectroscopy) optical instrument mounted on the Cassegrain foc…
View article: The Distance to the Stars
The Distance to the Stars Open
The vastness of a clear night sky evokes for most people curiosity about the distance to the stars. There are two primary methods for estimating stellar distances – parallax and luminosity. In this study, we present a new analysis revealin…
View article: Luminosity distance and extinction by submicrometer-sized grains
Luminosity distance and extinction by submicrometer-sized grains Open
The distance to the stars is a fundamental parameter, which is determined via two primary methods - parallax and luminosity. While the parallax is a direct trigonometric method, the luminosity distance is usually influenced by interstellar…
View article: Dark dust
Dark dust Open
The nature of dust in the diffuse interstellar medium can be best investigated by means of reddening curves where only a single interstellar cloud lies between the observer and the background source. Published reddening curves often suffer…
View article: The beta Pictoris system: Setting constraints on the planet and the disk structures at mid-IR wavelengths with NEAR
The beta Pictoris system: Setting constraints on the planet and the disk structures at mid-IR wavelengths with NEAR Open
[abridged] We analyzed mid-infrared high-contrast coronagraphic images of the beta Pictoris system, taking advantage of the NEAR experiment using the VLT/VISIR instrument. The goal of our analysis is to investigate both the detection of th…
View article: The <i>β</i> Pictoris system: Setting constraints on the planet and the disk structures at mid-IR wavelengths with NEAR
The <i>β</i> Pictoris system: Setting constraints on the planet and the disk structures at mid-IR wavelengths with NEAR Open
Context. β Pictoris is a young nearby system hosting a well-resolved edge-on debris disk, along with at least two exoplanets. It offers key opportunities for carrying out detailed studies of the evolution of young planetary systems and the…
View article: Paradigmatic examples for testing models of optical light polarization by spheroidal dust
Paradigmatic examples for testing models of optical light polarization by spheroidal dust Open
We present a general framework on how the polarization of radiation due to scattering, dichroic extinction, and birefringence of aligned spheroidal dust grains can be implemented and tested in 3D Monte Carlo radiative transfer (MCRT) codes…
View article: Spatially resolving polycyclic aromatic hydrocarbons in Herbig Ae disks with VISIR-NEAR at the VLT
Spatially resolving polycyclic aromatic hydrocarbons in Herbig Ae disks with VISIR-NEAR at the VLT Open
We use the long-slit spectroscopy mode of the VISIR-NEAR experiment to perform diffraction-limited observations of eight nearby Herbig Ae protoplanetary disks. We extract spectra for various locations along the slit with a spectral resolut…
View article: Disentangling the AGN and Star formation Contributions to the Radio–X-Ray Emission of Radio-loud Quasars at 1 < Z < 2
Disentangling the AGN and Star formation Contributions to the Radio–X-Ray Emission of Radio-loud Quasars at 1 < Z < 2 Open
We constrain the emission mechanisms responsible for the prodigious electromagnetic output generated by active galactic nuclei (AGNs) and their host galaxies with a novel state-of-the-art AGN radio-to-X-ray spectral energy distribution mod…
View article: Paradigmatic examples for testing models of optical light polarization by spheroidal dust
Paradigmatic examples for testing models of optical light polarization by spheroidal dust Open
We present a general framework on how the polarization of radiation due to scattering, dichroic extinction, and birefringence of aligned spheroidal dust grains can be implemented and tested in 3D Monte Carlo radiative transfer (MCRT) codes…
View article: Dark dust
Dark dust Open
Distance estimates derived from spectroscopy or parallax have been unified by considering extinction by large grains. The addition of such a population of what is called dark dust to models of the diffuse interstellar medium is tested agai…
View article: Dark dust II: Properties in the general field of the diffuse ISM
Dark dust II: Properties in the general field of the diffuse ISM Open
Distance estimates derived from spectroscopy or parallax have been unified by considering extinction by large grains. The addition of such a population of what is called Dark Dust to models of the diffuse interstellar medium is tested agai…
View article: Efficiently combining <i>α</i> CenA multi-epoch high-contrast imaging data
Efficiently combining <i>α</i> CenA multi-epoch high-contrast imaging data Open
Context. Keplerian-Stacker is an algorithm capable of combining multiple observations acquired at different epochs by taking into account the orbital motion of a potential planet present in the images to boost the ultimate detection limit.…
View article: Lessons learned from the NEAR experiment and prospects for the upcoming mid-IR HCI instruments
Lessons learned from the NEAR experiment and prospects for the upcoming mid-IR HCI instruments Open
The mid-infrared (IR) regime is well suited to directly detect the thermal\nsignatures of exoplanets in our solar neighborhood. The NEAR experiment:\ndemonstration of high-contrast imaging (HCI) capability at ten microns, can\nreach sub-mJ…
View article: Status update on the development of METIS, the mid-infrared ELT imager and spectrograph
Status update on the development of METIS, the mid-infrared ELT imager and spectrograph Open
editorial reviewed
View article: Broadened profiles of diffuse interstellar bands
Broadened profiles of diffuse interstellar bands Open
The paper describes profile broadening and peak wavelength variation of diffuse interstellar bands (DIBs) measured for 46 lines of sight, probably caused by the physical properties of intervening clouds. The full width at half-maximum of f…
View article: High-contrast imaging at ten microns: A search for exoplanets around Eps Indi A, Eps Eri, Tau Ceti, Sirius A, and Sirius B
High-contrast imaging at ten microns: A search for exoplanets around Eps Indi A, Eps Eri, Tau Ceti, Sirius A, and Sirius B Open
Context. The direct imaging of rocky exoplanets is one of the major science goals of upcoming large telescopes. The contrast requirement for imaging such planets is challenging. However, the mid-IR (infrared) regime provides the optimum co…
View article: Constraints on the nearby exoplanet <i>ϵ</i> Indi Ab from deep near- and mid-infrared imaging limits
Constraints on the nearby exoplanet <i>ϵ</i> Indi Ab from deep near- and mid-infrared imaging limits Open
The past decade has seen increasing efforts in detecting and characterising exoplanets using high-contrast imaging in the near- and mid-infrared, which is the optimal wavelength domain for studying old, cold planets. In this work, we prese…
View article: Author Correction: Imaging low-mass planets within the habitable zone of α Centauri
Author Correction: Imaging low-mass planets within the habitable zone of α Centauri Open
View article: New mid-infrared imaging constraints on companions and protoplanetary disks around six young stars
New mid-infrared imaging constraints on companions and protoplanetary disks around six young stars Open
Context. Mid-infrared (mid-IR) imaging traces the sub-micron and micron-sized dust grains in protoplanetary disks and it offers constraints on the geometrical properties of the disks and potential companions, particularly if those companio…
View article: Instrumentation for ESO’s Extremely Large Telescope
Instrumentation for ESO’s Extremely Large Telescope Open
Design and construction of the instruments for ESO’s Extremely Large Telescope (ELT) began in 2015. We present here a brief overview of the status of the ELT Instrumentation Plan. Dedicated articles on each instrument are presented elsewhe…
View article: Imaging low-mass planets within the habitable zone of α Centauri
Imaging low-mass planets within the habitable zone of α Centauri Open
Giant exoplanets on wide orbits have been directly imaged around young stars. If the thermal background in the mid-infrared can be mitigated, then exoplanets with lower masses can also be imaged. Here we present a ground-based mid-infrared…
View article: FORS-Up: May the FORS Be With Us For Another 15 Years
FORS-Up: May the FORS Be With Us For Another 15 Years Open
The FORS Upgrade project (FORS-Up) will extend the life of the popular workhorse instrument attached to ESO’s Very Large Telescope (VLT), FORS2. The project — a collaboration between ESO and INAF–Astronomical Observatory of Trieste — aims …
View article: FORS-Up: Making the most versatile instrument in Paranal ready for 15 more years of operations
FORS-Up: Making the most versatile instrument in Paranal ready for 15 more years of operations Open
The FORS Upgrade project (FORS-Up) aims at bringing a new life to the highly demanded workhorse instrument attached to ESO's Very Large Telescope (VLT). FORS2 is a multimode optical instrument, which started regular science operations in 2…
View article: Disentangling the AGN and Star-Formation Contributions to the Radio-X-ray Emission of Radio-Loud Quasars at 1
Disentangling the AGN and Star-Formation Contributions to the Radio-X-ray Emission of Radio-Loud Quasars at 1 Open
We constrain the emission mechanisms responsible for the prodigious electromagnetic output generated by active galactic nuclei (AGN) and their host galaxies with a novel state-of-the-art AGN radio- to-X-ray spectral energy distribution mod…
View article: Disentangling the AGN and star-formation contributions to the radio-X-ray emission of radio-loud quasars at $1<z<2$
Disentangling the AGN and star-formation contributions to the radio-X-ray emission of radio-loud quasars at $1<z<2$ Open
\n We constrain the emission mechanisms responsible for the prodigious electromagnetic output generated by active galactic nuclei (AGNs) and their host galaxies with a novel state-of-the-art AGN radio-to-X-ray spectral energy distribution …
View article: Design, pointing control, and on-sky performance of the mid-infrared vortex coronagraph for the VLT/NEAR experiment
Design, pointing control, and on-sky performance of the mid-infrared vortex coronagraph for the VLT/NEAR experiment Open
Vortex coronagraphs have been shown to be a promising avenue for high-contrast imaging in the close-in environment of stars at thermal infrared (IR) wavelengths. They are included in the baseline design of the mid-infrared extremely large …
View article: On the Relation between Diffuse Bands and Other Interstellar Features*
On the Relation between Diffuse Bands and Other Interstellar Features* Open
We discuss possible relations between different constituents of interstellar clouds, such as gas atoms (Fe i ), simple molecular species (CH, CN), and the carriers of the puzzling diffuse interstellar bands (DIBs 5780, 5797, 5850 Å) as wel…
View article: precision: a fast python pipeline for high-contrast imaging – application to SPHERE observations of the red supergiant VX Sagitariae
precision: a fast python pipeline for high-contrast imaging – application to SPHERE observations of the red supergiant VX Sagitariae Open
The search for extrasolar planets has driven rapid advances in instrumentation, resulting in cameras such as SPHERE at the VLT, GPI at Gemini South and SCExAO at Subaru, capable of achieving very high contrast (∼106) around bright stars wi…