Search Publications
Cyclotron lines in highly magnetized neutron stars
Haberl, F.; Klochkov, D.; Santangelo, A. +10 more
Cyclotron lines, also called cyclotron resonant scattering features are spectral features, generally appearing in absorption, in the X-ray spectra of objects containing highly magnetized neutron stars, allowing the direct measurement of the magnetic field strength in these objects. Cyclotron features are thought to be due to resonant scattering of…
ALMA observations of molecular tori around massive black holes
Krips, M.; van der Werf, P.; Combes, F. +12 more
We report Atacama Large Millimeter/submillimeter Array (ALMA) observations of CO(3-2) emission in a sample of seven Seyfert/LINER galaxies at the unprecedented spatial resolution of 0.″1 = 4-8 pc. Our aim is to explore the close environment of active galactic nuclei (AGN), and the dynamical structures leading to their fueling…
Reclassification of Cepheids in the Gaia Data Release 2. Period-luminosity and period-Wesenheit relations in the Gaia passbands
Ripepi, V.; Molinaro, R.; Eyer, L. +3 more
Context. Classical Cepheids are the most important primary indicators for the extragalactic distance scale. Establishing the precise zero points of their period-luminosity and period-Wesenheit (PL/PW) relations has profound consequences on the estimate of H0. Type II Cepheids are also important distance indicators and tracers of old ste…
Prolonged sub-luminous state of the new transitional pulsar candidate CXOU J110926.4‑650224
Rea, Nanda; Coti Zelati, Francesco; Torres, Diego F. +12 more
We report on a multi-wavelength study of the unclassified X-ray source CXOU J110926.4‑650224 (J1109). We identified the optical counterpart as a blue star with a magnitude of ∼20.1 (3300–10500 Å). The optical emission was variable on timescales from hundreds to thousands of seconds. The spectrum showed prominent emission lines with variable profil…
Background modelling for γ-ray spectroscopy with INTEGRAL/SPI
Diehl, Roland; Greiner, Jochen; Siegert, Thomas +3 more
Context. The coded-mask spectrometer-telescope SPI on board the INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) records photons in the energy range between 20 and 8000 keV. A robust and versatile method for modelling the dominating instrumental background radiation is difficult to establish for such a telescope in the rapidly changing s…
Comparing simulated 26Al maps to gamma-ray measurements
Krumholz, Mark R.; Diehl, Roland; Greiner, Jochen +4 more
Context. The diffuse gamma-ray emission of 26Al at 1.8 MeV reflects ongoing nucleosynthesis in the Milky Way and traces massive-star feedback in the interstellar medium due to its 1 Myr radioactive lifetime. The morphology and dynamics of the interstellar medium are investigated in astrophysics through 3D hydrodynamic simulations in fin…
Overview of non-transient γ-ray binaries and prospects for the Cherenkov Telescope Array
Walter, R.; Sidoli, L.; La Palombara, N. +20 more
Aims: Despite recent progress in the field, there are still many open questions regarding γ-ray binaries. In this paper we provide an overview of non-transient γ-ray binaries and discuss how observations with the Cherenkov Telescope Array (CTA) will contribute to their study.
Methods: We simulated the spectral behaviour of the non-transi…
Constraints on positron annihilation kinematics in the inner Galaxy
Diehl, Roland; Siegert, Thomas; Panther, Fiona H. +4 more
Context. The annihilation of cosmic positrons with electrons in the interstellar medium results in the strongest persistent γ-ray line signal in the sky. For the past 50 yr, this 511 keV emission - predominantly from the galactic bulge region and from a low surface-brightness disk - has puzzled observers and theoreticians. A key issue for understa…
Vertical position of the Sun with γ-rays
Siegert, Thomas
We illustrate a method for estimating the vertical position of the Sun above the Galactic plane by γ-ray observations. Photons of γ-ray wavelengths are particularly well suited for geometrical and kinematic studies of the Milky Way because they are not subject to extinction by interstellar gas or dust. Here, we use the radioactive decay line of
A broadband spectral analysis of 4U 1702-429 using XMM-Newton and BeppoSAX data
Santangelo, A.; Sanna, A.; Segreto, A. +8 more
Context. Most of the X-ray binary systems containing neutron stars classified as Atoll sources show two different spectral states, referred to as soft and hard. Moreover, a large number of these systems show a reflection component relativistically smeared in their spectra, which provides information on the innermost region of the system.
Aims…