An X-ray variable absorber within the Broad Line Region in Fairall 51

Fairall 51 is a polar-scattered Seyfert 1 galaxy, a type of active galaxies believed to represent a bridge between unobscured type-1 and obscured type-2 objects. Fairall 51 has shown complex and variable X-ray absorption but only little is known about its origin. In our research, we observed Fairall 51 with the X-ray satellite Suzaku in order to constrain a characteristic time-scale of its variability. We performed timing and spectral analysis of four observations separated by 1.5, 2 and 5.5 day intervals. We found that the 0.5-50 keV broadband X-ray spectra are dominated by a primary power-law emission (with the photon index ~ 2). This emission is affected by at least three absorbers with different ionisations (log(xi) ~ 1-4). The spectrum is further shaped by a reprocessed emission, possibly coming from two regions -- the accretion disc and a more distant scattering region. The accretion disc emission is smeared by the relativistic effects, from which we measured the spin of the black hole as a ~ 0.8 (+-0.2). We found that most of the spectral variability can be attributed to the least ionised absorber whose column density changed by a factor of two between the first (highest-flux) and the last (lowest-flux) observation. A week-long scale of the variability indicates that the absorber is located at the distance ~ 0.05 pc from the centre, i.e., in the Broad Line Region.Comment: 12 pages, 9 figures, accepted to A&

X-ray Variability Study of Polar Scattered Seyfert 1 Galaxies

We study 12 Seyfert 1 galaxies with a high level of optical polarization. Optical light emerging from the innermost regions is predominantly scattered in a polar region above the central engine directly in our line of sight. These sources show characteristics of Seyfert 2 galaxies such as, e.g., polarized broad lines. The polarization signatures suggest a viewing angle of 45 degrees classifying them as intermediate Seyfert 1/2 types. The unified model predicts this line of sight to pass through the outer layer of the torus resulting in significant soft X-ray variability due to a strongly varying column density. The aim is to find evidence for this geometrical assumption in the spectral variability of all available historical observations of these sources by XMM-Newton and Swift.Comment: Conference proceedings for the 10th INTEGRAL/BART Workshop on 22-25 April 2013, Karlovy Vary (Carlsbad), Czech Republi

The Soft-Excess in Mrk 509: Warm Corona or Relativistic Reflection?

We present the analysis of the first NuSTAR observations ($\sim 220$ ks), simultaneous with the last SUZAKU observations ($\sim 50$ ks), of the active galactic nucleus of the bright Seyfert 1 galaxy Mrk 509. The time-averaged spectrum in the $1-79$ keV X-ray band is dominated by a power-law continuum ($\Gamma\sim 1.8-1.9$), a strong soft excess around 1 keV, and signatures of X-ray reflection in the form of Fe K emission ($\sim 6.4$ keV), an Fe K absorption edge ($\sim 7.1$ keV), and a Compton hump due to electron scattering ($\sim 20-30$ keV). We show that these data can be described by two very different prescriptions for the soft excess: a warm ($kT\sim 0.5-1$ keV) and optically thick ($\tau\sim10-20$) Comptonizing corona, or a relativistically blurred ionized reflection spectrum from the inner regions of the accretion disk. While these two scenarios cannot be distinguished based on their fit statistics, we argue that the parameters required by the warm corona model are physically incompatible with the conditions of standard coronae. Detailed photoionization calculations show that even in the most favorable conditions, the warm corona should produce strong absorption in the observed spectrum. On the other hand, while the relativistic reflection model provides a satisfactory description of the data, it also requires extreme parameters, such as maximum black hole spin, a very low and compact hot corona, and a very high density for the inner accretion disk. Deeper observations of this source are thus necessary to confirm the presence of relativistic reflection, and to further understand the nature of its soft excess.Comment: Accepted for publication in ApJ, 18 pages, 7 figure

Optical properties of Peaked Spectrum radio sources

In this work, we study the optical properties of compact radio sources selected from the literature in order to determine the impact of the radio-jet in their circumnuclear environment. Our sample includes 58 Compact Steep Spectrum (CSS) and GigaHertz Peaked Spectrum (GPS) and 14 Megahertz-Peaked spectrum (MPS) radio sources located at z ≤ 1. The radio luminosity (LR) of the sample varies between Log LR ∼ 23.2 and 27.7 W Hz−1. We obtained optical spectra for all sources from SDSS-DR12 and performed a stellar population synthesis using the STARLIGHT code. We derived stellar masses (M ), ages t , star formation rates (SFR), metallicities Z and internal reddening AV for all young AGNs of our sample. A visual inspection of the SDSS images was made to assign a morphological class for each source. Our results indicate that the sample is dominated by intermediate to old stellar populations and there is no strong correlation between optical and radio properties of these sources. Also, we found that young AGNs can be hosted by elliptical, spiral and interacting galaxies, confirming recent findings. When comparing the optical properties of CSS/GPS and MPS sources, we do not find any significant difference. Finally, the Mid-Infrared WISE colours analysis suggests that the compact radio sources defined as powerful AGNs are, in general, gas-rich systems

Implications of the Warm Corona and Relativistic Reflection Models for the Soft Excess in Mrk 509

We present the analysis of the first Nuclear Spectroscopic Telescope Array observations (~220 ks), simultaneous with the last Suzaku observations (~50 ks), of the active galactic nucleus of the bright Seyfert 1 galaxy Mrk 509. The time-averaged spectrum in the 1–79 keV X-ray band is dominated by a power-law continuum (Γ ~ 1.8–1.9), a strong soft excess around 1 keV, and signatures of X-ray reflection in the form of Fe K emission (~6.4 keV), an Fe K absorption edge (~7.1 keV), and a Compton hump due to electron scattering (~20–30 keV). We show that these data can be described by two very different prescriptions for the soft excess: a warm (kT ~ 0.5–1 keV) and optically thick (τ ~ 10–20) Comptonizing corona or a relativistically blurred ionized reflection spectrum from the inner regions of the accretion disk. While these two scenarios cannot be distinguished based on their fit statistics, we argue that the parameters required by the warm corona model are physically incompatible with the conditions of standard coronae. Detailed photoionization calculations show that even in the most favorable conditions, the warm corona should produce strong absorption in the observed spectrum. On the other hand, while the relativistic reflection model provides a satisfactory description of the data, it also requires extreme parameters, such as maximum black hole spin, a very low and compact hot corona, and a very high density for the inner accretion disk. Deeper observations of this source are thus necessary to confirm the presence of relativistic reflection and further understand the nature of its soft excess

Science for society

Chapter 8 presents an introduction and sections on: education and outreach in an interdisciplinary environment; science with and for the citizens; open communication and responsible citizens; science and ethics; the limits of scienc

Implications of the Warm Corona and Relativistic Reflection Models for the Soft Excess in Mrk 509

We present the analysis of the first Nuclear Spectroscopic Telescope Array observations (~220 ks), simultaneous with the last Suzaku observations (~50 ks), of the active galactic nucleus of the bright Seyfert 1 galaxy Mrk 509. The time-averaged spectrum in the 1–79 keV X-ray band is dominated by a power-law continuum (Γ ~ 1.8–1.9), a strong soft excess around 1 keV, and signatures of X-ray reflection in the form of Fe K emission (~6.4 keV), an Fe K absorption edge (~7.1 keV), and a Compton hump due to electron scattering (~20–30 keV). We show that these data can be described by two very different prescriptions for the soft excess: a warm (kT ~ 0.5–1 keV) and optically thick (τ ~ 10–20) Comptonizing corona or a relativistically blurred ionized reflection spectrum from the inner regions of the accretion disk. While these two scenarios cannot be distinguished based on their fit statistics, we argue that the parameters required by the warm corona model are physically incompatible with the conditions of standard coronae. Detailed photoionization calculations show that even in the most favorable conditions, the warm corona should produce strong absorption in the observed spectrum. On the other hand, while the relativistic reflection model provides a satisfactory description of the data, it also requires extreme parameters, such as maximum black hole spin, a very low and compact hot corona, and a very high density for the inner accretion disk. Deeper observations of this source are thus necessary to confirm the presence of relativistic reflection and further understand the nature of its soft excess

Astronomy organizations should lead in our battle against the climate crisis

The alarming sound in the latest IPCC ‘code red’ report was unmistakable: “Without immediate and deep emissions reductions across all sectors, limiting global warming to 1.5 °C is beyond reach.” Only a few weeks later, the World Meteorological Organization reported that there is now a 50% chance that we will temporarily reach 1.5 °C warming already in the next five years. And indeed, with the increasing frequency and severity of natural disasters such as flooding, heat waves and droughts, it is becoming harder not to see a looming climate catastrophe unless massive and immediate action is taken. Astronomers worldwide are well aware of our peril and are demanding astronomy organizations to act — nearly 3,000 have signed Astronomers for Planet Earth’s open letter demanding climate action from our institutions

Single-Dish Radio Polarimetry in the F-GAMMA Program with the Effelsberg 100-m Radio Telescope

Studying the variability of polarized AGN jet emission in the radio band is crucial for understanding the dynamics of moving shocks as well as the structure of the underlying magnetic field. The 100-m Effelsberg Telescope is a high-quality instrument for studying the long-term variability of both total and polarized intensity as well as the electric-vector position angle. Since 2007, the F-GAMMA program has been monitoring the linear polarized emission of roughly 60 blazars at 11 frequencies between 2.7 and 43 GHz. Here, we describe the calibration of the polarimetric data at 5 and 10 GHz and the resulting F-GAMMA full-Stokes light curves for the exemplary case of the radio galaxy 3C 111