arXiv subjects

Astrid Orr

Publications and source records attributed to Astrid Orr.

5 recordsLinked to original sources

arXiv2019

The ASIM Mission on the International Space Station

The Atmosphere-Space Interactions Monitor (ASIM) is an instrument suite on the International Space Station (ISS) for measurements of lightning, Transient Luminous Events (TLEs) and Terrestrial Gamma-ray Flashes (TGFs). Developed in the framework of the European Space Agency (ESA), it was launched April 2, 2018 on the SpaceX CRS-14 flight to the ISS. ASIM was mounted on an external platform of ESA's Columbus module eleven days later and is planned to take measurements during minimum 3 years.

astro-ph.IM↗

arXiv2000

NLS1s and Sy1s: A comparison of ionized X-ray absorber properties

The first results from a systematic study of warm absorbers in NLS1s using BeppoSAX public archive data are presented here. We confirm ASCA results showing that a warm absorber, as modeled by two oxygen K-shell absorption edges, is less frequent in NLS1s than in broad line (BL) Sy1s (about 20 per cent versus about 50 per cent). However, our study suggests that the ionization state of NLS1s is not lower than that of BLS1s, as opposed to the ASCA-based results. The soft excess temperatures of our sample, when fitted with blackbody emission models, lie within a small range of values (about 0.02-0.15 keV in the rest frame) with no marked dependence on source luminosity. This is in agreement with ASCA-based findings for NLS1s and early results from IUE-ROSAT BL Sy1 observations.

astro-ph↗

arXiv1998

Quasi-simultaneous observations of 3C 273 by BeppoSAX and ASCA

We report the results of quasi-simultaneous observations of the bright quasar 3C 273 using the BeppoSAX Low-Energy Concentrator Spectrometer (LECS) and the ASCA Solid-State Imaging Spectrometer (SIS). These observations are part of an intercalibration programme and demonstrate good agreement between both instruments in the common energy range 0.5-10 keV. In particular, the absorption feature discovered by BeppoSAX/LECS at $\sim$ 0.5 keV is consistently seen by ASCA/SIS. We present the most accurate measurement yet of the spectral shape of this absorption feature and provide constraints on its physical interpretation. A self-consistent warm absorber model in photoionization equilibrium only gives an adequate spectral fit if a very high velocity inflow is allowed for the warm absorber (v $\sim$ 0.36 c). The ionization parameter and the column density of the warm absorber are then $\sim$ 1 and $\sim$ 1.3e21 cm^-2, respectively. If the differences in best-fit neutral absorption column density between the LECS and each SIS are taken as estimates of the systematic spectral uncertainties, then these are < 0.8e20 and < 2.e20 cm^-2 (at 90 % confidence) for SIS0 and SIS1, respectively.

astro-ph↗

arXiv1997

BeppoSAX observations of low-energy spectral features in AGN

The combination of the broad band coverage and moderate spectral resolution of the LECS and MECS instruments on-board BeppoSAX allow the spectra of AGN to be studied in unprecedented detail down to 0.1 keV. We describe the calibration and the performance of the LECS and report on observations of low-energy absorption features in the spectra of both a low (MCG-6-30-15) and a high luminosity (3C 273) AGN. These features provide important diagnostics on the location and nature of the material surrounding the AGN. A comparison of LECS and ASCA/SIS low energy performance is also presented in the case of 3C 273.

astro-ph↗

arXiv1997

Soft X-ray observations of the complex warm absorber in MCG-6-30-15 with BeppoSAX

We report on soft X-ray observations of the Seyfert 1 galaxy MCG-6-30-15 with the Low and Medium Energy Concentrator Spectrometers on board BeppoSAX. The time averaged 0.1-4 keV spectrum shows evidence for a complex warm absorber. K-edges of highly ionized oxygen (O vii and O viii) can only partly describe the soft X-ray spectrum below 2 keV. A spectral variability study reveales large and rapid changes in absorption at the energy of the O viii K-edge and in the continuum shape and count rate. These fluctuations are not simply correlated.

astro-ph↗