Finn E. Christensen
A5083512039- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Advanced X-ray Imaging Techniques
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Particle Detector Development and Performance
- X-ray Spectroscopy and Fluorescence Analysis
- Galaxies: Formation, Evolution, Phenomena
- High-pressure geophysics and materials
- Nuclear Physics and Applications
- Astronomy and Astrophysical Research
- Calibration and Measurement Techniques
- Adaptive optics and wavefront sensing
- Dark Matter and Cosmic Phenomena
- Astronomical Observations and Instrumentation
- Advanced Surface Polishing Techniques
- Solar and Space Plasma Dynamics
- Particle Accelerators and Free-Electron Lasers
- X-ray Diffraction in Crystallography
- Advanced Semiconductor Detectors and Materials
- Geophysics and Gravity Measurements
- Surface Roughness and Optical Measurements
- Superconducting Materials and Applications
- Stellar, planetary, and galactic studies
- Mechanics and Biomechanics Studies
DTU Space
2015-2024
Technical University of Denmark
2015-2024
Max Planck Institute for Extraterrestrial Physics
2024
European Space Research and Technology Centre
2020-2024
Brera Astronomical Observatory
2022-2023
DXC Technology (Denmark)
2023
University of Leicester
2023
Teledyne e2v (United Kingdom)
2022
Lawrence Livermore National Laboratory
2004-2019
Laboratoire Charles Fabry
2019
The Nuclear Spectroscopic Telescope Array (NuSTAR) mission, launched on 2012 June 13, is the first focusing high-energy X-ray telescope in orbit. NuSTAR operates band from 3 to 79 keV, extending sensitivity of far beyond ∼10 keV cutoff achieved by all previous satellites. inherently low background associated with concentrating light enables probe hard sky a more than 100-fold improvement over collimated or coded mask instruments that have operated this bandpass. Using its unprecedented...
Hypothetical low-mass particles, such as axions, provide a compelling explanation for the dark matter in universe. Such particles are expected to emerge abundantly from hot interior of stars. To test this prediction, CERN Axion Solar Telescope (CAST) uses 9 T refurbished Large Hadron Collider magnet directed towards Sun. In strong magnetic field, solar axions can be converted X-ray photons which recorded by detectors. 2013–2015 run, thanks low-background detectors and new telescope,...
This White Paper, submitted to the recent ESA call for science themes define its future large missions, advocates need a transformational leap in our understanding of two key questions astrophysics: 1) How does ordinary matter assemble into scale structures that we see today? 2) do black holes grow and shape Universe? Hot gas clusters, groups intergalactic medium dominates baryonic content local Universe. To understand astrophysical processes responsible formation assembly these structures,...
The International Axion Observatory (IAXO) will be a forth generation axion helioscope. As its primary physics goal, IAXO look for axions or axion-like particles (ALPs) originating in the Sun via Primakoff conversion of solar plasma photons. In terms signal-to-noise ratio, about 4–5 orders magnitude more sensitive than CAST, currently most powerful helioscope, reaching sensitivity to axion-photon couplings down few × 10−12 GeV−1 and thus probing large fraction unexplored ALP parameter space....
We present the calibration of Nuclear Spectroscopic Telescope Array (NuSTAR) X-ray satellite. used Crab as primary effective area calibrator and constructed a piece-wise linear spline function to modify vignetting response. The achieved residuals for all off-axis angles energies, compared assumed spectrum, are typically better than ±2% up 40 keV 5%–10% above due limited counting statistics. An empirical adjustment theoretical two-dimensional point-spread (PSF) was found using several strong...
The evolution of galaxies is connected to the growth supermassive black holes in their centers. During quasar phase, a huge luminosity released as matter falls onto hole, and radiation-driven winds can transfer most this energy back host galaxy. Over five different epochs, we detected signatures nearly spherical stream highly ionized gas broadband x-ray spectra luminous PDS 456. This persistent wind expelled at relativistic speeds from inner accretion disk, its wide aperture suggests an...
We report the discovery of 3.76 s pulsations from a new burst source near Sgr A* observed by NuSTAR observatory. The strong signal SGR J1745−29 presents complex pulse profile modulated with pulsed fraction 27% ± 3% in 3–10 keV band. Two observations spaced nine days apart yield spin-down rate =(6.5 1.4) × 10−12. This implies magnetic field B = 1.6 1014 G, power =5 1033 erg s−1, and characteristic age P/2 =9 103 yr for rotating dipole model. However, current may be erratic, especially during...
The search for diffuse non-thermal inverse Compton (IC) emission from galaxy clusters at hard X-ray energies has been undertaken with many instruments, most detections being either of low significance or controversial. Background and contamination uncertainties present in the data non-focusing observatories result lower sensitivity to IC a greater chance false detection. We 266ks NuSTAR observations Bullet cluster, detected 3-30 keV. NuSTAR's unprecedented focusing capability largely...
A novel geometry in which it is possible to do x-ray diffraction from a horizontal surface of fluids applied liquid crystals. large-diameter drop octyloxycyanobiphenyl (8OCB) on glass plate treated for homeotropic alignment yields perfect the smectic-$A$ layers at top over an area several square millimeters. The bulk nematic as well isotropic phase was found consist with penetration depth equal longitudinal correlation length...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExtended x-ray absorption fine structure study of the cobalt-molybdenum hydrodesulfurization catalystsBjerne S. Clausen, Henrik Topsoe, Roberto Candia, Jorgen Villadsen, Bruno Lengeler, Jens Als-Nielsen, and Finn ChristensenCite this: J. Phys. Chem. 1981, 85, 25, 3868–3872Publication Date (Print):December 1, 1981Publication History Published online1 May 2002Published inissue 1 December...
We report the results of a multi-band observing campaign on famous blazar 3C 279 conducted during phase increased activity from 2013 December to 2014 April, including first observations it with NuSTAR. The $\gamma$-ray emission source measured by Fermi-LAT showed multiple distinct flares reaching highest flux level in this object since beginning Fermi mission, $F(E > 100\,{\rm MeV})$ $10^{-5}$ photons cm$^{-2}$ s$^{-1}$, and doubling time scale as short 2 hours. spectrum one was very hard,...
We report on observations of NGC1068 with NuSTAR, which provide the best constraints to date its $>10$~keV spectral shape. find no strong variability over past two decades, consistent Compton-thick AGN classification. The combined Chandra, XMM-Newton, and Swift-BAT dataset offers new insights into complex reflected emission. critical combination high signal-to-noise NuSTAR data a spatial decomposition Chandra allow us break several model degeneracies greatly aid physical interpretation. When...
The black hole binary Cygnus X-1 was observed in late-2012 with the Nuclear Spectroscopic Telescope Array (NuSTAR) and Suzaku, providing spectral coverage over ~1-300 keV range. source soft state a multi-temperature blackbody, power-law, reflection components along absorption from highly ionized material system. high throughput of NuSTAR allows for very quality measurement complex iron line region as well rest component. is clearly broadened well-described by relativistic blurring model, an...
We present 3-50 keV NuSTAR observations of the AGN Mrk 335 in a very low flux state. The spectrum is dominated by strong features at energies iron line 5-7 and Compton hump from 10-30 keV. source variable during observation, with variability concentrated energies, which suggesting either relativistic reflection or absorption scenario. In this work we focus on interpretation, making use new models that self consistently calculate fraction, blurring angle-dependent for different coronal...
Stellar metals shine toward our eyes only Taking a different look at familiar star may still yield surprises. Boggs et al. trained the x-ray vision of NuSTAR observatory on well-studied supernova 1987A. Core-collapse explosions such as SN 1987A produce titanium isotope, 44 Ti, whose radioactive decay yields hard emission lines. All associated with 44Ti appears to be from material moving us, none away. This implies that explosion was not symmetric. These findings help explain mechanics and...
We present simultaneous Nuclear Spectroscopic Telescope Array (NuSTAR ) and Suzaku observations of the X-ray binary Cygnus X-1 in hard state. This is first time this state has been observed Cyg with NuSTAR, which enables us to study reflection broadband spectra unprecedented detail. confirm that iron line cannot be fit a combination narrow lines absorption features, instead requiring relativistically blurred profile from companion wind. use models García et al. simultaneously measure black...
We present the results of NuSTAR and XMM-Newton observations two ultraluminous X-ray sources (ULX) NGC 1313 X-1 X-2. The combined spectral bandpass satellites enables us to produce first spectrum between 0.3 30 keV, while X-2 is not significantly detected by above 10 keV. data demonstrate that has a clear cutoff whose presence was only marginally detectable with previous observations. This rules out interpretation as black hole in standard low/hard state, it deeper than predicted for...
We present coordinated multiwavelength observations of the bright, nearby BL Lac object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, VERITAS, and other collaborations instruments, providing data from radio to very-high-energy (VHE) gamma-ray bands. NuSTAR yielded previously unattainable sensitivity 3-79 keV range, revealing that spectrum softens when source is dimmer until X-ray spectral shape saturates into a steep power law with photon index...
The distribution of elements produced in the inner-most layers a supernova explosion is key diagnostic for studying collapse massive stars. Here we present results 2.4 Ms \textit{NuSTAR} observing campaign aimed at remnant Cassiopeia A (Cas A). We perform spatially-resolved spectroscopic analyses $^{44}$Ti ejecta which use to determine Doppler shift and thus three-dimensional (3D) velocities ejecta. find an initial mass 1.54 $\pm$ 0.21 $\times 10^{-4}$ M$_{\odot}$ has day average momentum...
We report on a NuSTAR and XMM-Newton program that has observed sample of three extremely luminous, heavily obscured WISE-selected AGN at z~2 in broad X-ray band (0.1 - 79 keV). The parent sample, selected to be faint or undetected the WISE 3.4um (W1) 4.6um (W2) bands but bright 12um (W3) 22um (W4), are rare, with only ~1000 so-called W1W2-dropouts across extragalactic sky. Optical spectroscopy reveals typical redshifts for this population, implying rest-frame mid-IR luminosities L(6um)~6e46...
We present results from the coordinated broadband X-ray observations of extreme ultraluminous source Holmberg IX X-1 performed by NuSTAR, XMM-Newton and Suzaku in late 2012. These provide first high-quality spectra above 10 keV to date, extending coverage this remarkable up ~30 keV. Broadband were undertaken at two epochs, between which exhibited both flux strong spectral variability, increasing luminosity Lx = (1.90+/-0.03)e40 erg/s (3.35+/-0.03)e40 erg/s. Neither epoch exhibits a spectrum...
We present X-ray spectral analyses for three Seyfert 2 active galactic nuclei, NGC 424, 1320, and IC 2560, observed by NuSTAR in the 3-79 keV band. The high quality hard spectra allow detailed modeling of Compton reflection component first time these sources. Using quasi-simultaneous Swift/XRT data, as well archival XMM-Newton we find that all nuclei are obscured Compton-thick material with column densities excess ~5 x $10^{24}$ cm$^{-2}$, their above 3 dominated intrinsic continuum on...