Gas shells and magnetic fields in the Orion-Eridanus superbubble

Aims. The Orion-Eridanus superbubble has been blown by supernovae and supersonic winds of the massive stars in the Orion OB associations. It is the nearest site at which stellar feedback on the interstellar medium that surrounds young massive clusters can be studied. The formation history and current structure of the superbubble are still poorly understood, however. It has been pointed out that the picture of a single expanding object should be replaced by a combination of nested shells that are superimposed along the line of sight. We have investigated the composite structure of the Eridanus side of the superbubble in the light of a new decomposition of the atomic and molecular gas. Methods. We used H I 21 cm and CO (J = 1−0) emission lines to separate coherent gas shells in space and velocity, and we studied their relation to the warm ionised gas probed in Hα emission, the hot plasma emitting X-rays, and the magnetic fields traced by dust polarised emission. We also constrained the relative distances to the clouds using dust reddening maps and X-ray absorption. We applied the Davis–Chandrasekhar–Fermi method to the dust polarisation data to estimate the plane-of-sky components of the magnetic field in several clouds and along the outer rim of the superbubble. Results. Our gas decomposition has revealed several shells inside the superbubble that span distances from about 150–250 pc. One of these shells forms a nearly complete ring filled with hot plasma. Other shells likely correspond to the layers of swept-up gas that is compressed behind the expanding outer shock wave. We used the gas and magnetic field data downstream of the shock to derive the shock expansion velocity, which is close to ~20 km s−1. Taking the X-ray absorption by the gas into account, we find that the hot plasma inside the superbubble is over-pressured compared to plasma in the Local Bubble. The plasma comprises a mix of hotter and cooler gas along the lines of sight, with temperatures of (3–9) and (0.3 − 1.2) × 106 K, respectively. The magnetic field along the western and southern rims and in the approaching wall of the superbubble appears to be shaped and compressed by the ongoing expansion. We find plane-of-sky magnetic field strengths from 3 to 15 μG along the rim.

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Statistics of Radio-X-Ray Emission and Magnetic Fields in the Intergalactic Medium

Symposium - International Astronomical Union ◽

10.1017/s0074180900241168 ◽

1990 ◽

Vol 139 ◽

pp. 414-415

Author(s):

Hitoshi Hanami

Keyword(s):

Magnetic Field ◽

Cosmic Rays ◽

Magnetic Fields ◽

Intergalactic Medium ◽

Relativistic Electrons ◽

X Ray ◽

Cooling Flows ◽

Hot Plasma ◽

Inverse Compton ◽

The Magnetic Field

X-ray observations have demonstrated that the intergalactic medium in many clusters (cf. Coma, Perseus) contains a thin, hot plasma that may be produced by the accretion process in the gravitational potential of clusters with radiative cooling; this is usually called “cooling flows” (Fabian, Nulsen, and Canizares 1984; Sarazin 1986). On the other hand, the existence of radio halos in some clusters has been reported (Coma: Jaffe, Perola, and Valentijn 1976; A401: Roland et al. 1981). In addition, many elliptical galaxies in the center of clusters are also strong synchrotron radio sources. These radio emissions provide evidence for large amounts of relativistic electrons associated with the active phenomena in or around these galaxies and clusters. We can estimate the values or limits on the magnetic field in the cluster from the limits on the inverse Compton X-ray emission with the synchrotron radio emission (cf. Jaffe 1980). The intracluster field strength Bo is roughly 1 μG. It has been suggested that the influence of cosmic rays and magnetic fields is important for the properties and dynamics of the intercluster medium (Böhringer and Morfill 1988; Soker and Sarazin 1989). If cooling flows are real, this inward flow can impede the escape of the cosmic rays from the central galaxies in clusters and enhance the magnetic field. The confinement of the cosmic rays and the magnetic field in the center of clusters affects the gas of the intracluster medium.

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Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

International Astronomical Union Colloquium ◽

10.1017/s0252921100064630 ◽

2000 ◽

Vol 179 ◽

pp. 263-264

Author(s):

K. Sundara Raman ◽

K. B. Ramesh ◽

R. Selvendran ◽

P. S. M. Aleem ◽

K. M. Hiremath

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Magnetic Flux ◽

Ultra Violet ◽

Active Regions ◽

Morphological Properties ◽

Energy Storage And Conversion ◽

The Sun ◽

X Rays ◽

The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

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Investigating the Magnetospheres of Rapidly Rotating B-type Stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317002812 ◽

2016 ◽

Vol 12 (S329) ◽

pp. 369-372

Author(s):

C. L. Fletcher ◽

V. Petit ◽

Y. Nazé ◽

G. A. Wade ◽

R. H. Townsend ◽

...

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Centrifugal Force ◽

Point Of View ◽

Closed Field ◽

Theoretical Point ◽

X Rays ◽

Rapid Rotation ◽

X Ray ◽

Surface Magnetic Field

AbstractRecent spectropolarimetric surveys of bright, hot stars have found that ~10% of OB-type stars contain strong (mostly dipolar) surface magnetic fields (~kG). The prominent paradigm describing the interaction between the stellar winds and the surface magnetic field is the magnetically confined wind shock (MCWS) model. In this model, the stellar wind plasma is forced to move along the closed field loops of the magnetic field, colliding at the magnetic equator, and creating a shock. As the shocked material cools radiatively it will emit X-rays. Therefore, X-ray spectroscopy is a key tool in detecting and characterizing the hot wind material confined by the magnetic fields of these stars. Some B-type stars are found to have very short rotational periods. The effects of the rapid rotation on the X-ray production within the magnetosphere have yet to be explored in detail. The added centrifugal force due to rapid rotation is predicted to cause faster wind outflows along the field lines, leading to higher shock temperatures and harder X-rays. However, this is not observed in all rapidly rotating magnetic B-type stars. In order to address this from a theoretical point of view, we use the X-ray Analytical Dynamical Magnetosphere (XADM) model, originally developed for slow rotators, with an implementation of new rapid rotational physics. Using X-ray spectroscopy from ESA’s XMM-Newton space telescope, we observed 5 rapidly rotating B-types stars to add to the previous list of observations. Comparing the observed X-ray luminosity and hardness ratio to that predicted by the XADM allows us to determine the role the added centrifugal force plays in the magnetospheric X-ray emission of these stars.

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Cyclotron lines in highly magnetized neutron stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834479 ◽

2019 ◽

Vol 622 ◽

pp. A61 ◽

Cited By ~ 34

Author(s):

R. Staubert ◽

J. Trümper ◽

E. Kendziorra ◽

D. Klochkov ◽

K. Postnov ◽

...

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Neutron Stars ◽

Direct Measurement ◽

Resonant Scattering ◽

Electron Cyclotron ◽

X Ray ◽

Cyclotron Line ◽

The Magnetic Field ◽

Proton Cyclotron

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 photons by electrons in the strong magnetic fields. The main content of this contribution focusses on electron cyclotron lines as found in accreting X-ray binary pulsars (XRBP) with magnetic fields on the order of several 1012Gauss. Also, possible proton cyclotron lines from single neutron stars with even stronger magnetic fields are briefly discussed. With regard to electron cyclotron lines, we present an updated list of XRBPs that show evidence of such absorption lines. The first such line was discovered in a 1976 balloon observation of the accreting binary pulsar Hercules X-1, it is considered to be the first direct measurement of the magnetic field of a neutron star. As of today (end 2018), we list 35 XRBPs showing evidence of one ore more electron cyclotron absorption line(s). A few have been measured only once and must be confirmed (several more objects are listed as candidates). In addition to the Tables of objects, we summarize the evidence of variability of the cyclotron line as a function of various parameters (especially pulse phase, luminosity and time), and add a discussion of the different observed phenomena and associated attempts of theoretical modeling. We also discuss our understanding of the underlying physics of accretion onto highly magnetized neutron stars. For proton cyclotron lines, we present tables with seven neutron stars and discuss their nature and the physics in these objects.

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First X-Ray Microprobe and Microspectroscopy Results From The Gsecars Sector At The Advanced Photon Source

Microscopy and Microanalysis ◽

10.1017/s1431927600011417 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 905-906

Author(s):

Mark L. Rivers ◽

Stephen R. Sutton ◽

Peter Eng ◽

Matthew Newville

Keyword(s):

National Laboratory ◽

Argonne National Laboratory ◽

Third Generation ◽

X Rays ◽

Environmental Sciences ◽

X Ray ◽

State Determination ◽

X Ray Absorption ◽

The Magnetic Field ◽

Photon Source

The Advanced Photon Source (APS) at Argonne National Laboratory is a third-generation synchrotron x-ray source, optimized for producing x-rays from undulators. Such undulator sources provide extremely bright, quasi-monochromatic radiation which is ideal for an x-ray microprobe. Such microprobes can be used for trace element quantification with x-ray fluorescence, or for chemical state determination with x-ray absorption spectroscopy. The GeoSoilEnviroCARS (GSECARS) sector at the APS is building an x-ray microprobe for research in earth, planetary, soil and environmental sciences.The GSECARS undulator source is a standard APS Undulator “A” which is a 3.3 cm period device with 72 periods. The energies of the undulator peaks can be varied by adjusting the gap, and hence the magnetic field of the undulator. The energy of the first harmonic can be varied in this way from approximately 3.1 keV to 14 keV. A measured undulator spectrum is shown in Figure 1.

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Thermal and non-thermal connection in radio mini-halos

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318007020 ◽

2018 ◽

Vol 14 (S342) ◽

pp. 137-140

Author(s):

A. Ignesti ◽

G. Brunetti ◽

M. Gitti ◽

S. Giacintucci

Keyword(s):

Magnetic Field ◽

Surface Brightness ◽

X Rays ◽

X Ray ◽

Point Analysis ◽

Spectrum Radio ◽

Point To Point ◽

The Magnetic Field ◽

Relativistic Particles ◽

Open Issues

AbstractSeveral cool-core clusters are known to host a radio mini-halo, a diffuse, steep-spectrum radio source located in their cores, thus probing the presence of non-thermal components as magnetic field and relativistic particles on scales not directly influenced by the central AGN. The nature of the mechanism that produces a population of radio-emitting relativistic particles on the scale of hundreds of kiloparsecs is still unclear. At the same time, it is still debated if the central AGN may play a role in the formation of mini-halos by providing the seed of the relativistic particles. We aim to investigate these open issues by studying the connection between thermal and non-thermal components of the intra-cluster medium. We performed a point-to-point analysis of the radio and the X-ray surface brightness of a compilation of mini-halos. We find that mini-halos have super-linear scalings between radio and X-rays, with radio brightness declining more steeply than the X-ray brightness. This trend is opposite to that generally observed in giant radio halos, thus marking a possible difference in the physics of the two radio sources. Finally, using the scalings between radio and X-rays and assuming a hadronic origin of mini-halos we derive constraints on the magnetic field in the core of the hosting clusters.

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On Special Features of Non-Thermal Solar X Radiation above 10 keV

International Astronomical Union Colloquium ◽

10.1017/s0252921100089958 ◽

1972 ◽

Vol 14 ◽

pp. 761-762

Author(s):

G. Elwert ◽

E. Haug

Keyword(s):

Magnetic Field ◽

Angular Distribution ◽

Power Law ◽

Impulsive Phase ◽

X Rays ◽

Energetic Electrons ◽

X Ray ◽

Preferred Direction ◽

Field Lines ◽

The Magnetic Field

The polarization and angular distribution of solar hard X radiation above 10 keV was calculated under the assumption that the X rays originate as bremsstrahlung from energetic electrons moving in a preferred direction. The source electrons are supposed to have a power-law spectrum. These conditions are to be expected in the impulsive phase of an X-ray burst. The spiral orbits of the electrons around the magnetic field lines are taken into account.

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Performance Evaluation of an MR-Compatible Rotating Anode X-Ray Tube

Volume 4A: Dynamics, Vibration and Control ◽

10.1115/imece2013-66460 ◽

2013 ◽

Author(s):

Mihye Shin ◽

Prasheel Lillaney ◽

Waldo Hinshaw ◽

Rebecca Fahrig

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Magnetic Moments ◽

X Ray ◽

Close Proximity ◽

Motor Design ◽

Design Requirements ◽

And Performance ◽

The Magnetic Field ◽

Lorentz Force Law

The key technical innovation needed for close proximity hybrid x-ray/MR (XMR) imaging systems is a new rotating anode x-ray tube motor that can operate in the presence of strong magnetic fields. In order for the new motor design to be optimized between conflicting design requirements, we implemented a numerical model for evaluating the dynamics of the motor. The model predicts the amount of produced torque, rotation speed, and time to accelerate based on the Lorentz force law; the motor is accelerated by the interaction between the magnetic moments of the motor wire loops and an external magnetic field. It also includes an empirical model of bearing friction and electromagnetic force from the magnetic field. Our proposed computational model is validated by experiments using several different magnitudes of external magnetic fields, which averagely shows an agreement within 0.5 % error during acceleration. We are using this model to improve the efficiency and performance of future iterations of the x-ray tube motor.

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Rheological and Resistance Properties of Magnetorheological Elastomer with Cobalt for Sensor Application

Applied Sciences ◽

10.3390/app10051638 ◽

2020 ◽

Vol 10 (5) ◽

pp. 1638 ◽

Cited By ~ 4

Author(s):

Afiq Azri Zainudin ◽

Nurul Azhani Yunus ◽

Saiful Amri Mazlan ◽

Muhammad Kashfi Shabdin ◽

Siti Aishah Abdul Aziz ◽

...

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Vibrating Sample Magnetometer ◽

Magnetorheological Elastomer ◽

X Ray ◽

Sensing Applications ◽

Morphological Aspects ◽

Frequency Sweep Test ◽

Applied Forces ◽

The Magnetic Field

Cobalt particles have been introduced as a filler due to the advantages of embedding their magnetic and electrical properties in magnetorheological elastomer (MRE). In the present research, the rheology and resistance of MRE are experimentally evaluated. Isotropic and anisotropic MRE samples containing silicone rubber and cobalt particles were fabricated. The magnetic properties of MRE are conducted using a vibrating sample magnetometer (VSM). The morphological aspects of MRE are observed by using field emission scanning electron microscopy (FESEM) and characterized by energy-dispersive X-ray spectroscopy (EDX). Rheological properties under various magnetic field strengths were measured for the magnetic field, strain amplitude, and frequency sweep test by using a parallel-plate rheometer. Subsequently, the resistance of MRE is tested under different applied forces and magnetic fields. The MRE storage modulus depicted an enhancement in field-dependent modulus across all the applied magnetic fields. The electrical resistance generated from the sample can be manipulated by external magnetic fields and mechanical loads. The conductivity of MRE is due to the existence of cobalt arrangements observed by FESEM. By introducing cobalt as filler and obtaining satisfactory results, the study might open new avenues for cobalt to be used as filler in MRE fabrication for future sensing applications.

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Magnetic field at the inner disk edge

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307009416 ◽

2007 ◽

Vol 3 (S243) ◽

pp. 51-62 ◽

Cited By ~ 1

Author(s):

Moira Jardine ◽

Scott G. Gregory ◽

Jean-François Donati

Keyword(s):

Magnetic Field ◽

Doppler Imaging ◽

Evolutionary Stage ◽

X Rays ◽

X Ray ◽

Stellar Radius ◽

T Tauri ◽

The Impact ◽

The Magnetic Field ◽

Present Understanding

AbstractOur present understanding of the coronal structure of T Tauri stars is fragmentary and observations in different wavelength regimes often appear to give contradictory results. X-ray data suggest the presence of magnetic loops on a variety of scales, from compact loops of size less than a stellar radius, up to very large loops of up to 10 stellar radii which may connect to the disk. While some stars show a clear rotational modulation in X-rays, implying distinct bright and dark regions, many do not. This picture is complicated by the accretion process itself, which also contributes to the X-ray emission. The location of the inner edge of the accretion disk and the nature of the magnetic field there are still hotly-contested issues. Accretion indicators often suggest the presence of discrete accretion funnels. This has implications for the structure of the corona, as does the presence of an outflowing wind. All of these factors are linked to the structure of the magnetic field, which we are now beginning to unravel through Zeeman-Doppler imaging. In this review I will describe the present state of our understanding of the magnetic structure of T Tauri coronae and the impact this has during such an early evolutionary stage.

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