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1.
The Diffuse X‐ray emission from the Local Galaxy (DXL) sounding rocket is a NASA approved mission with a scheduled first launch in December 2012. Its goal is to identify and separate the X‐ray emission of the solar wind charge exchange (SWCX) from that of the local hot bubble (LHB) to improve our understanding of both. To separate the SWCX contribution from the LHB, DXL will use the SWCX signature due to the helium focusing cone at l = 185°, b = –18°. DXL uses large area proportional counters, with an area of 1000 cm2 and grasp of about 10 cm2 sr both in the 1/4 and 3/4 keV bands. Thanks to the large grasp, DXL will achieve in a 5‐minute flight what cannot be achieved by current and future X‐ray satellites (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

2.
In recent work it was demonstrated that narrow‐line Seyfert 1 galaxies, which possessed spectral complexity in the 2–10 keV band were at the same time X‐ray weak. In this contribution I show how X‐ray weakness can be understood in the context of reflection and light bending picture. In fact, X‐ray weakness should be expected from objects that are in a reflection dominated state. With simultaneous UV and X‐ray data available with most XMM‐Newton observations, an estimate of the X‐ray weakness is relatively straightforward. As such, it is an easy way to substantiate conclusions of reflection dominated spectra, and we use this method to examine recent claims. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

3.
We present the analysis of optical and X‐ray XMM‐Newton data of the source 4U 1344‐60. On the basis of the optical data we propose to classify 4U 1344‐60 as a Seyfert 1.5 galaxy and we measured a redshift value z = 0.012 ± 0.001. The observed X‐ray spectrum is complex. The continuum emission can be described as a power law obscured by two neutral absorption components. 4U 1344‐60 exhibits a broad and skewed iron line at 6.4 keV most likely originated in a few gravitational radius of an accretion disc. The analysis also reveals the presence of two narrow emission line‐like features at ∼4.9 keV and ∼5.3 keV. Assuming that hot spots on the surface of the accretion disc, orbiting very close to the black hole is responsible of these emission lines, the accretion disc would present an inclination of 20° and the active regions would be located in the 6–10 R g radius range. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

4.
Observations of hundreds of supersoft X‐ray sources (SSSs) in external galaxies have shed light on the diversity of the class and on the natures of the sources. SSSs are linked to the physics of Type Ia supernovae and accretion‐induced collapse, ultraluminous X‐ray sources and black holes, the ionization of the interstellar medium, and tidal disruption by supermassive black holes. The class of SSSs has an extension to higher luminosities: ultraluminous SSSs have luminosities above 1039 erg s–1. There is also an extension to higher energies: quasisoft X‐ray sources (QSSs) emit photons with energies above 1 keV, but few or none with energies above 2 keV. Finally, a significant fraction of the SSSs found in external galaxies switch states between observations, becoming either quasisoft or hard. For many systems “supersoft” refers to a temporary state; SSSs are sources, possibly including a variety of fundamentally different system types, that pass through such a state. We review those results derived from extragalactic data and related theoretical work that are most surprising and that suggest directions for future research (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

5.
Both Chandra and XMM‐Newton have performed long look programs for studying the YSO physics. I will discuss recent results on the controversial issue of Class 0 YSO X‐ray emission, the observational evidence of magnetic funnels interconnecting the YSO with its circumstellar disk and the Fe 6.4 keV fluorescent line emission and its origin. While recent results of the XMM‐Newton DROXO program challenge the “standard” interpretation of the Fe 6.4 kev line origin as due to photoionized fluorescing disk material, the discovery of X‐ray excited Ne 12.81 μ m line is a clear evidence of the interaction between X‐rays and disk material. Future long look observations with XMM‐Newton are required to clarify the X‐ray effects on YSO disk. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

6.
Charge‐transfer is the main process linking neutrals and charged particles in the interaction regions of neutral (or partly ionized) gas with a plasma. In this paper we illustrate the importance of charge‐transfer with respect to the dynamics and the structure of neutral gas‐plasma interfaces. We consider the following phenomena: (1) the heliospheric interface ‐ region where the solar wind plasma interacts with the partly‐ionized local interstellar medium (LISM) and (2) neutral interstellar clouds embedded in a hot, tenuous plasma such as the million degree gas that fills the so‐called “Local Bubble”. In (1), we discuss several effects in the outer heliosphere caused by charge exchange of interstellar neutral atoms and plasma protons. In (2) we describe the role of charge exchange in the formation of a transition region between the cloud and the surrounding plasma based on a two‐component model of the cloud‐plasma interaction. In the model the cloud consists of relatively cold and dense atomic hydrogen gas, surrounded by hot, low density, fully ionized plasma. We discuss the structure of the cloud‐plasma interface and the effect of charge exchange on the lifetime of interstellar clouds. Charge transfer between neutral atoms and minor ions in the plasma produces X‐ray emission. Assuming standard abundances of minor ions in the hot gas surrounding the cold interstellar cloud, we estimate the X‐ray emissivity consecutive to the charge transfer reactions. Our model shows that the charge‐transfer X‐ray emission from the neutral cloud‐plasma interface may be comparable to the diffuse thermal X‐ray emission from the million degree gas cavity itself (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

7.
GRB 100219A at z = 4.667 has been the highest redshift gamma‐ray burst observed with the X‐shooter spectrograph up to now. The spectrum covering the range from 5000 to 24000 Å and a large number of absorption lines allows to make a detailed study of the interstellar medium in a high redshift galaxy. The ISM in the low ionisation state and the kinematics of the absorption line components reveal a complex velocity field. The metallicity measured from different absorption lines is around 0.1 solar. Other GRB hosts at redshift beyond ∼3 have similar metallicities albeit with a large scatter in the metallicity distribution. X‐shooter will allow us to determine metallicities of a larger number of GRB hosts beyond redshift 5, to probe the early chemical enrichment of the Universe and to study its evolution from redshift 2 to beyond 10 (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

8.
We present monitoring analysis of 8 XMM‐Newton observations of the Seyfert 2 galaxy Mrk 3, spanning a period of ∼19 months. The continuum flux in the 3–12 keV band remains constant during this observing period. The X‐ray spectrum is well described, in agreement with previous works, by a highly absorbed (N H > 1024 cm–2) power law model, with a photon index Γ = 1.9 and a strong reflection component. A strong Fe Kα line at 6.4 keV with an equivalent width of ∼500 eV is detected in the X‐ray spectrum. When we consider the co‐added spectrum we also detect a weaker emission line at 7.4 keV corresponding to neutral Ni Kα emission and weak evidence for the presence of an ionized Fe Kα line at 6.7 keV. Direct comparison with the results obtained from an earlier XMM‐Newton observation of Mrk 3, shows a decrease in the continuum flux of ∼30 per cent followed by a similar decrease in the reflected component. Both emission line components at 6.4 and 6.7 keV do not vary. However we find that an alternative model where the N H varies by 20 per cent is also plausible. In this case both the continuum and the reflected emission do not change. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

9.
This article summarizes the processes of high‐energy emission in young stellar objects. Stars of spectral type A and B are called Herbig Ae/Be (HAeBe) stars in this stage, all later spectral types are termed classical T Tauri stars (CTTS). Both types are studied by high‐resolution X‐ray and UV spectroscopy and modeling. Three mechanisms contribute to the highenergy emission from CTTS: 1) CTTS have active coronae similar to main‐sequence stars, 2) the accreted material passes through an accretion shock at the stellar surface, which heats it to a few MK, and 3) some CTTS drive powerful outflows. Shocks within these jets can heat the plasma to X‐ray emitting temperatures. Coronae are already well characterized in the literature; for the latter two scenarios models are shown. The magnetic field suppresses motion perpendicular to the field lines in the accretion shock, thus justifying a 1D geometry. The radiative loss is calculated as optically thin emission. A mixture of shocked and coronal gas is fitted to X‐ray observations of accreting CTTS. Specifically, the model explains the peculiar line‐ratios in the He‐like triplets of Ne IX and O VII. All stars require only small mass accretion rates to power the X‐ray emission. In contrast, the HAeBe HD 163296 has line ratios similar to coronal sources, indicating that neither a high density nor a strong UV‐field is present in the region of the X‐ray emission. This could be caused by a shock in its jet. Similar emission is found in the deeply absorbed CTTS DG Tau. Shock velocities between 400 and 500 km s–1 are required to explain the observed spectrum (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

10.
Mkn 841 has been observed during 3 different periods (January 2001, January 2005 and July 2005) by XMM‐Newton for a total cumulated exposure time of ∼108 ks. We present in this paper a broad band spectral analysis of the complete EPIC‐pn data sets. These observations confirm the presence of the strong soft excess and complex iron line profile known to be present in this source since a long time. They also reveal their extreme and puzzling spectral and temporal behaviors. Indeed, the 0.5–2 keV soft X‐ray flux decreases by a factor 3 between 2001 and 2005 and the line shape appears to be a mixed of broad and narrow components, both variable but on different timescales. The broad‐band 0.5–10 keV spectra are well described by a model including a primary power law continuum, a blurred photoionized reflection and a narrow iron line, the blurred reflection fitting self‐consistently the soft excess and the broad line component. The origin and nature of the narrow component is unclear. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

11.
About 15 years ago, charge exchange (CX) X‐ray emission was discovered in comet observations, and was identified as the radiative decay of excited states of highly‐charge solar wind ions populated in collisions with neutral cometary material. This non‐thermal X‐ray emission mechanism is now generally acknowledged in planetary environments (e.g. Mars, Earth), as well as interstellar atoms sweeping through the heliosphere. In this paper I present the most recent improvements made in simulations of the heliospheric CX X‐ray emission. The model results are compared to X‐ray data from Suzaku, XMM‐Newton and Chandra spanning over a 10‐year period, and some conclusions are drawn on the heliospheric contribution to the diffuse soft X‐ray background. The solar system CX X‐ray sources can serve as prototypes in terms of modeling and diagnostics to more distant astrophysical objects where CX emission signatures are being discovered (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

12.
This paper shows that our understanding of the statistical properties of X‐ray selected normal galaxies (e.g. X‐ray luminosity function) can be significantly improved by combining a wide‐area XMM‐Newton survey with the moderare resolution and high S/N optical spectroscopy of the SDSS. Such a combined dataset has the potential to minimise uncertainties that affect existing normal galaxy samples at X‐rays, such as small number statistics, cosmic variance, AGN contamination and incompleteness at bright X‐ray luminosities. It is demonstrated that a 100 deg2 XMM‐Newton survey in the SDSS area to the limit fX(0.5–2 keV) ≈ 5 × 10–15 erg cm–2 s–1 will detect over 400 X‐ray selected normal galaxies with excellent control over systematic biases, thereby providing tight contraints on the X‐ray luminosity function at z ≈ 0.1. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

13.
High resolution X‐ray spectroscopy is a powerful tool for studying the nature of the matter surrounding the neutron star in X‐ray binaries and its interaction between the stellar wind and the compact object. In particular, absorption features in their spectra could reveal the presence of atmospheres of the neutron star or their magnetic field strength. Here we present an investigation of the absorption feature at 2.1 keV in the X‐ray spectrum of the high mass X‐ray binary 4U 1538–52 based on our previous analysis of the XMM‐Newton data. We study various possible origins and discuss the different physical scenarios in order to explain this feature. A likely interpretation is that the feature is associated with atomic transitions in an O/Ne neutron star atmosphere or of hydrogen and helium like Fe or Si ions formed in the stellar wind of the donor. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

14.
We present the analysis of X‐ray spectral variability made on a sample of 7 Seyfert 1 bright galaxies, using XMM‐Newton data. From the “XMM‐Newton Science Archive” we selected those bright Seyfert 1 showing one or more prominent flares in their 2–10 keV light curves. For each of them we extracted spectra in 3 different time intervals: before, during and after the flare. We fitted them with a simple power law and then shifted a narrow emission and absorption line template across the 2.5–10 keV data, in order to investigate the presence of line‐like features with a confidence level greater than 99%. Some highly significant features were detected in 3 out of 7 sources studied. In particular, the 3 sources, namely PG 1211+143, NGC 4051 and NGC 3783, showed the presence of a variable emission feature in the 4.5–5.8 keV band, characterized by an increase of its intensity after the flare peak. Because of the observed variability pattern, this feature seems to be ascribable to a reverbered redshifted relativistic component of the Fe K line. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

15.
The Herschel Space Observatory is well suited to address several important questions in star‐ and planet formation, as is evident from its first year of operation. This paper focuses on observations of water, a key molecule in the physics and chemistry of star‐formation. In the WISH Key Program, a comprehensive set of water lines is being obtained with the HIFI and PACS instruments toward a large sample of well‐characterized protostars, covering a wide range of luminosities and evolutionary stages. Lines of H2O, CO and their isotopologues, as well as chemically related hydrides, [O I] and [C II] are observed. Together, the data determine the abundance of water in cold and warm gas, reveal the entire CO ladder up to 4000 K above ground, elucidate the physical processes responsible for the warm gas (passive heating, UV or X‐ray‐heating, shocks), quantify the main cooling agents, and probe dynamical processes associated with forming stars and planets (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

16.
Hadronic cosmic rays of energies below about 100 MeV nucleon–1 are thought to be an important component of the Galactic ecosystem. However, since these particles cannot be detected near Earth due to the solar modulation effect, their composition and flux in the interstellar medium are very uncertain. Atomic interactions of low‐energy cosmic rays with interstellar gas can produce a characteristic nonthermal X‐ray emission comprising very broad lines from de‐excitations in fast ions following charge exchange. We suggest that broad lines at ∼0.57 and ∼0.65 keV could be detected from a dark molecular cloud in the local interstellar medium. These lines would be produced by fast oxygen ions of kinetic energies around 1 MeV nucleon–1 (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

17.
Luminosity functions are one of the most important observational clues when studying galaxy evolution over cosmic time. In this paper we present the X‐ray luminosity functions for X‐ray detected AGN in the SXDS and GWS fields. The limiting fluxes of our samples are 9.0 ×10–15 and 4.8 ×10–16 erg cm–2 s–1 in the 0.5–7.0 keV band in the two fields, respectively. We carried out analysis in three X‐ray bands and in two redshift intervals up to z ≤ 1.4. Moreover, we derive the luminosity functions for different optical morphologies and X‐ray types. We confirm strong luminosity evolution in all three bands, finding the most luminous objects at higher redshift. However, no signs of density evolution are found in any tested X‐ray band. We obtain similar results for compact and early‐type objects. Finally, we observe the “Steffen effect”, where X‐ray type‐1 sources are more numerous at higher luminosities in comparison with type‐2 sources. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

18.
We present the results of soft X‐ray studies of the classical nova V2491 Cygni using the Suzaku observatory. On day 29 after outburst, a soft X‐ray component with a peak at ∼0.5 keV has appeared, which is tantalising evidence for the beginning of the super‐soft X‐ray emission phase. We show that an absorbed blackbody model can describe the observed spectra, yielding a temperature of 57 eV, neutral hydrogen column density of 2 × 1021 cm–2, and a bolometric luminosity of ∼1036 erg s–1. However, at the same time, we also found a good fit with an absorbed thin‐thermal plasma model, yielding a temperature of 0.1 keV, neutral hydrogen column density of 4 × 1021 cm–2, and a volume emission measure of ∼1058 cm–3. Owing to low spectral resolution and low signal‐to‐noise ratio below 0.6 keV, the statistical parameter uncertainties are large, but the ambiguity of the two very different models demonstrates that the systematic errors are the main point of concern. The thin‐thermal plasma model implies that the soft emission originates from optically thin ejecta, while the blackbody model suggests that we are seeing optically thick emission from the white dwarf (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

19.
We report on the iron Kα line properties of a sample of Seyfert galaxies observed with the XMM‐Newton EPIC pn instrument. Using a systematic and uniform analysis, we find that complexity at iron‐K is extremely common in the XMM‐Newton spectra. Once appropriate soft X‐ray absorption, narrow 6.4 keV emission and associated Compton reflection are accounted for, ∼75% of the sample show an improvement when a further component is introduced. The typical properties of the broad emission are both qualitatively and quantitatively consistent with previous results from ASCA. The complexity is in general very well described by relativistic accretion disk models. In most cases the characteristic emission radius is constrained to be within ∼50R g, where strong gravitational effects become important. We find in about 1/3 of the sample the accretion disk interpretation is strongly favoured over competing models. In a few objects no broad line is apparent. We find evidence for emission within 6R g in only two cases, both of which exhibit highly complex absorption. Evidence for black hole spin based on the X‐ray spectra therefore remains tentative. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

20.
Current, accumulating evidence for (mildly) relativistic blue‐ and red‐shifted absorption lines in AGNs is reviewed. XMM‐Newton and Chandra sensitive X‐ray observations are starting to probe not only the kinematics (velocity) but also the dynamics (accelerations) of highly ionized gas flowing in‐and‐out from, likely, a few gravitational radii from the black hole. It is thus emphasized that X‐ray absorption‐line spectroscopy provides new potential to map the accretion flows near black holes, to probe the launching regions of relativistic jets/outflows, and to quantify the cosmological feedback of AGNs. Prospects to tackle these issues with future high energy missions are briefly addressed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

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