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The soft X-ray background (SXRB, 0.1 — 2.0 keV) is generally believed to be comprised of a local component, the Local (Hot) Bubble (LHB), which is only marginally absorbed, and of distant emission (galactic halo, extragalactic background). It is vital to know the foreground emission (spectrum, intensity) if one wants to disentangle and determine the 3-dimensional structure of the X-ray emitting regions...
We report on FIR measurements of the dust component towards LVC 88+36-2, a dense neutral filament in the Local Hot Bubble. The measurements were performed with ISOPHOT, the photometer on-board ESA’s Infrared Space Observatory ISO1. The dust temperature derived is about 18 K and stays constant across the filament. Limb brightening at 60µm is measured in agreement with cirrus clouds not located...
Modeling the Local Bubble is one of those activities fraught with danger. It is very easy to be too naive, to fail to consider the dependence of the model on assumptions about the nearby ambient state, or the likelihood of such a structure. It is similarly easy to become so caught up in the details of the vicinity that it is unclear where to begin a necessarily idealized modeling effort. And finally,...
We have modeled the Local Bubble (LB) using a one-dimensional hydrocode (odin) that can simulate multiple supernova remnants, with non-equilibrium ion evolution and dust. Our model assumes that the local interstellar medium was a cool (104 K) gas approximately 5–10 Myr ago; it was then disturbed by 2 or 3 supernovae exploding within 20–30 pc of each other over a period of 2–4 million years. The LB...
Equations are derived which describe the propagation of strong shocks in the interstellar matter, without any restrictions for symmetry, in a thin layer approximation (2.5 dimensions). Using these equations permits to calculate the propagation of shock waves from nonsymmetric supernovae explosions in a medium with arbitrary density distribution and the formation of superbubbles in galaxies.
The so-called cumulative effect take place in converging conical shock waves arising behind dense obstacles overtaken by incident interstellar shock. A significant part of energy of converging flow of matter swept-up by a radiative conical shock can be transferred to a dense jet-like ejection (“bullet”) directed along the cone axis. Possible applications of this effect for star-forming regions (e...
In the paper we present results of numerical simulations of magnetorotational model of explosion of magnetized cloud. For the simulation we used a specially developed 2D implicit numerical scheme on Lagrangian triangular grid with grid reconstruction. Our results show that due to the amplification of toroidal magnetic field component and transfer of angular momentum, a compression wave in the envelope...
We describe results from high-resolution (Δv = 0.3−1.5 km s−1) observations of absorption lines due to interstellar Na I, Ca II, K I, Ca I, and Ti II. At those resolutions, we can identify and characterize many (but not all) of the individual clouds along a given line of sight; complex spatial and/or velocity structure appears to be the norm. Both the spectra and the statistics of individual cloud...
With new high resolution UV spectra of ε CMa we show that the gas column density in this sight-line is less than 4 1017 cm−2, that the neutral gas density is less than 10−5 cm−3 after the first 3 parsecs, and that the Local Cloud seems to be almost undepleted and to extend to no more than 0.6 pc in this direction.
We present new results based on the analysis of ROSAT PSPC observations towards nearby neutral clouds. These clouds are detectable as deep soft X-ray absorption features within the 1/4 keV energy band. Towards one of these clouds, optical absorption line measurements determine an upper distance limit of D ≤ 60 pc. The presented data suggest that this filament is only a part of a much more extended...
In recent years the nature of the low density clouds within the Local Bubble has been increasingly well characterized. These clouds, including the one which surrounds the solar system, are embedded in the hot gas and therefore should be evaporating via thermal conduction. If several evaporation fronts exist within the Local Bubble, the emissivity and spectrum of the hot gas is significantly different...
We present HST observations of the interstellar medium toward the star β CMa known to be located in a low density extension of the Local Bubble. Most of the matter in the sight-line is ionized and clumped in two main components. One of them, as well as one of the components detected toward ɛ CMa, is mostly ionized and only slightly depleted. Their ionization ratios are compatible with collisional...
The current status of observations of energetic particles in the “local bubble” is reviewed. This includes primarily “direct” measurements of cosmic rays made in the Solar System, but also the “remote sensing” made possible by observing cosmic ray produced γ-rays in the nearby interstellar clouds. Since the energetic events responsible for the formation of our local bubble may also have produced copious...
The excess of γ-ray emission in the energy range 3 – 7 MeV discovered by COMPTEL in the direction of the Orion complex may imply that there is a powerful source of low energy cosmic rays in the local galactic medium. Several interpretations of the excess have been suggested. One of them assumes that the emission is identified with nuclear de-excitation lines of excited 16O and 14C. To provide the...
Observations of interstellar Na I in the spectra of 93 stars within 315 pc from the Sun show that it lies in a tunnel of gas moving away from Scorpio-Centaurus and is surrounded by gas moving toward the Galactic center. Gas approaches the Sun from Scorpio-Centaurus expanding from (r, l, b)=(160 pc, 313°7, +28°2) with LSR velocity 15.3 km s−1. The radius of this shell is 153 pc. We identify...
We present a definition of the local void of neutral gas from observations in the radio frequency window. We question the concept of the Local Bubble in sense of a more or less spherical volume which is surrounded by a shell of denser gas. The concept of the Local Bubble is challenged by the discovery of numerous neutral, dense clouds inside the local void. The search for a “shell” around the suspected...
We present here the results from an extensive scintillation study of twenty pulsars in the dispersion measure (DM) range 3 – 35 pc cm−3 carried out using the Ooty Radio Telescope, to investigate the distribution of ionized material in the local interstellar medium (LISM). Our analysis reveals several anomalies in the scattering strength, which suggest that the distribution of scattering material in...
A possibility of obtaining information on small scale inhomogeneities of the electron component of the local interstellar medium (LISM) is investigated using interstellar scintillations of extragalactic radio sources. We analyse Culgoora array observational data on variability of 190 extragalactic radio sources, covering most of the sky, at 80 and 160 MHz. The variability at time scales from 1 month...
We discuss details in the galactic HI distribution, which are relevant for studies of the Local Bubble. All results are based on the 21 cm Sky survey with the Large Pulkovo Radiotelescope. The antenna temperature scans were decomposed in two components and after the subtraction of the broad one two details in the residual are presented in this paper. The first is an estimate of the distance to the...
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