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Register a new userASTRO-H White Paper - Accreting Pulsars, Magnetars, and Related Sources
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S. Kitamoto
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As the endpoints of massive star evolution, neutron stars are enigmatic celestial objects characterized by extremely dense and exotic nuclear matter, magnetospheres with positrons (antimatter), rapid rotation and ultra-strong magnetic fields. Such an extreme environment has provided an accessible astrophysical laboratory to study physics under conditions unattainable on Earth and to tackle a range of fundamental questions related to: the aftermath of stellar evolution and the powerful explosions of massive stars, the equation of state and physics of some of the most exotic and magnetic stars in the Universe, the workings of the most powerful particle accelerators in our Galaxy and beyond, and the sources of gravitational waves that are yet to be detected. Recent observations revealed a great diversity of neutron stars, including ultra-strongly magnetized pulsars, referred to as magnetars, and unusual types of accreting X-ray pulsars. In this white paper, we highlight the prospects of the upcoming X-ray mission, ASTRO-H, in studying these highly magnetized neutron stars.
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The next generation X-ray observatory ASTRO-H will open up a new dimension in the study of galaxy clusters by achieving for the first time the spectral resolution required to measure velocities of the intracluster plasma, and extending at the same time the spectral coverage to energies well beyond 10 keV. This white paper provides an overview of the capabilities of ASTRO-H for exploring gas motions in galaxy clusters including their cosmological implications, the physics of AGN feedback, dynamics of cluster mergers as well as associated high-energy processes, chemical enrichment of the intracluster medium, and the nature of missing baryons and unidentified dark matter.
Interacting binaries in which a white dwarf accretes material from a companion --- cataclysmic variables (CVs) in which the mass loss is via Roche-lobe overflow, and symbiotic stars in which the white dwarf captures the wind of a late type giant --- are relatively commonplace. They display a wide range of behaviors in the optical, X-rays, and other wavelengths, which still often baffles observers and theorists alike. They are likely to be a significant contributor to the Galactic ridge X-ray emission, and the possibility that some CVs or symbiotic stars may be the progenitors of some of the Type Ia supernovae deserves serious consideration. Furthermore, these binaries serve as excellent laboratories in which to study physics of X-ray emission from high density plasma, accretion physics, reflection, and particle acceleration. ASTRO-H is well-matched to the study of X-ray emission from many of these objects. In particular, the excellent spectral resolution of the SXS will enable dynamical studies of the X-ray emitting plasma. We also discuss the possibility of identifying an accreting, near-Chandrasekhar-mass white dwarf by measuring the gravitational redshift of the 6.4 keV line.
ASTRO-H White Papers are meant to provide useful information to scientists who plan observations from the satellite. This short paper introduces the 16 ASTRO-H White Papers in addition to general description of the satellite and its new features.
We discuss the prospects for a progress to be brought by ASTRO-H in the understanding of the physics of particle acceleration in astrophysical environments. Particular emphasis will be put on the synergy with gamma-ray astronomy, in the context of the rapid developments of recent years. Selected topics include: shock acceleration in supernova remnants (SNRs) and in clusters of galaxies, and the extreme particle acceleration seen in gamma-ray binaries. Since the hydrodynamics and thermal properties of shocks in these objects are covered in other white papers, we focus on the aspects related to the process of particle acceleration. In the case of SNRs, we emphasize the importance of SXS and HXI observations of the X-ray emission of young SNRs dominated by synchrotron radiation, particularly SNR RX J1713.7-3946. We argue that the HXI observations of young SNRs, as a byproduct of SXS observations dedicated for studies of the shock dynamics and nucleosynthesis, will provide powerful constraints on shock acceleration theories. Also, we discuss gamma-ray binary systems, where extreme particle acceleration is inferred regardless of the nature (a neutron star or a black hole) of the compact object. Finally, for galaxy clusters, we propose searches for hard X-ray emission of secondary electrons from interactions of ultra-high energy cosmic rays accelerated at accretion shocks. This should allow us to understand the contribution of galaxy clusters to the flux of cosmic rays above 10^18 eV.
In this white paper we describe the prospects for ASTRO-H for the study of outflows from active galactic nuclei. The most important breakthroughs in this field are expected to arise from the high spectral resolution and sensitivity in the Fe-K band, combined with broad-band sensitivity over the full X-ray band and spectral capabilities also at lower energies. The sensitivity in the Fe-K region allows to extend the absorption measure distribution of the outflow out to the highest ionisation states accessible, where observations with current X-ray missions indicate that most of the outflowing gas is to be found. Due to the high-resolution and sensitivity it will also be able to give the definitive proof for the existence of ultra-fast outflows, and if so, characterise their physical properties in great detail. These ultra-fast outflows carry very large amounts of energy and momentum, and are of fundamental importance for feedback studies. We show how the ASTRO-H observations in general can help to constrain numerical models for outflows. The link to reflection and emission processes is also discussed, as well as the possible relation between outflows and relativistic emission lines. Finally, we discuss the prospects for other related categories of objects like BAL quasars, partially covered sources and Compton thick outflows.
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