ON THE X-RAY PROPERTIES OF H2O MASER HOST GALAXIES

All galaxies beyond the Magellanic clouds with detected H 2 O maser emission so far are investigated and their X-ray observations are collected in detail to probe the X-ray properties of this special kind of galaxies. The soft excess and the strong iron emission line are commonly presented in their X-ray spectrum. Similar to the spectra of normal Seyfert 2 galaxies, the X-ray soft components are usually explained well by two alternative models or their combination: the absorbed power law model and the thermal emission model. The hard X-ray continua are usually flat, which should be caused by the increase of the reflection component, with the increase of the absorbing material density. Modeling their X-ray spectra shows that high absorbing column density is prevalent in our H 2 O megamaser host AGNs. Further, we investigate a possible relation between the iron line emission and the nuclear X-ray emission. It shows no significant correlation between the equivalent width (EW) of the neutral Fe Kα emission line (~ 6.4 keV) and the intrinsic nuclear X-ray luminosity. However, one trend appears clearly — the EW of the iron line decreases with the increase of the observed X-ray luminosity for our H 2 O maser galaxies. We also estimate the accretion rate of H 2 O maser host AGNs and the results show that maser galaxies may have a higher accretion rate than nonmaser Seyfert galaxies. In addition, possible relations between the EW of the iron line with the accretion rate and the central black hole mass are investigated and no significant trend of correlation can be found between them.

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X-Ray Line Emission from Supernova Remnants and Models for Nonequilibrium Ionization

Symposium - International Astronomical Union ◽

10.1017/s0074180900033738 ◽

1983 ◽

Vol 101 ◽

pp. 109-111

Author(s):

Craig L. Sarazin ◽

Andrew J. S. Hamilton ◽

Roger A. Chevalier

Keyword(s):

Supernova Remnants ◽

Thermal Emission ◽

Thermal Structure ◽

Line Emission ◽

Type I ◽

Emission Model ◽

Ionization State ◽

Severe Problem ◽

X Ray ◽

Nonequilibrium Ionization

An extensive grid of nonequilibrium ionization models for the X-ray spectra of adiabatic supernova remnants (SNRs) is described. The models are compared to the SSS spectra of remnants in the LMC, the Tycho SNR, and SNR 1006. In Tycho, we show that the observed spectrum requires significantly enhanced abundances of Si and S, and that this conclusion is independent of the detailed ionization and thermal structure in the remnant. We find that the SSS spectrum of SNR 1006 can be fit reasonably by a thermal emission model with abundances of about one half solar. In this model, the weak line emission results from the very low ionization state in the remnant, and not because the X-ray emission is non-thermal. We argue that the failure to detect strong Fe line emission in young Type I SNRs poses a severe problem for models of Type I SN, which predict that most of the ejecta be iron. Finally, the results of UV observations of a star behind SNR 1006 are mentioned; these observations show that the remnant contains a large amount of rapidly moving, cold iron.

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Strong gravity effects: X-ray spectra, variability and polarimetry

Proceedings of the International Astronomical Union ◽

10.1017/s174392130700484x ◽

2006 ◽

Vol 2 (S238) ◽

pp. 129-138

Author(s):

Andrew C. Fabian

Keyword(s):

Black Holes ◽

Black Hole ◽

Line Emission ◽

Disk Surface ◽

Seyfert Galaxies ◽

Iron Line ◽

X Ray ◽

Gravity Effects ◽

Show Evidence ◽

Iron Abundance

AbstractAccreting black holes often show iron line emission in their X-ray spectra. When this line emission is very broad or variable then it is likely to originate from close to the black hole. The theory and observations of such broad and variable iron lines are briefly reviewed here. In order for a clear broad line to be found, one or more of the following have to occur: high iron abundance, dense disk surface and minimal complex absorption.Several excellent examples are found from observations of Seyfert galaxies and Galactic Black Holes. In some cases there is strong evidence that the black hole is rapidly spinning. Further examples are expected as more long observations are made with XMM-Newton, Chandra and Suzaku. The X-ray spectra show evidence for the strong gravitational redshifts and light bending expected around black holes.

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Multi-Zone Warm and Cold Clumpy Absorbers in Three Seyfert Galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921310006885 ◽

2009 ◽

Vol 5 (S267) ◽

pp. 404-404

Author(s):

Claudio Ricci ◽

Volker Beckmann ◽

Marc Audard ◽

T. J.-L. Courvoisier

Keyword(s):

Black Hole ◽

Power Law ◽

Thermal Emission ◽

Accretion Rate ◽

Seyfert Galaxies ◽

High Energy ◽

X Ray ◽

The Past ◽

High Energy Tail ◽

Open Issue

A soft (E≲2 keV) excess over the power-law component dominant at higher energies has been found in the X-ray spectra of many Seyfert galaxies. The origin of the soft excess is still an open issue. In the past it was often associated with the high-energy tail of the thermal emission of the accretion disk, but it has been shown recently that the temperature of the disk should be constant (0.1–0.2 keV), regardless of the mass and luminosity of the AGN (Gierlinski & Done 2004). This result implies that some other mechanism is at work, as the temperature of the disk should depend on both the mass of the black hole and the accretion rate.

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ASCA Observations of LINERs

International Astronomical Union Colloquium ◽

10.1017/s0252921100039622 ◽

1997 ◽

Vol 159 ◽

pp. 54-55

Author(s):

Y. Terashima ◽

H. Kunieda ◽

N. Iyomoto ◽

K. Makishima ◽

P. J. Serlemitsos

Keyword(s):

Emission Line ◽

Seyfert Galaxies ◽

Point Sources ◽

Photon Statistics ◽

Short Time Scale ◽

Spectral Slope ◽

Iron Line ◽

X Ray ◽

Intrinsic Absorption ◽

Short Time

ASCA observations have revealed the presence of low-luminosity AGN in ~10 LINERs as a hard point sources at the nucleus. The X-ray continuum shapes (photon indices Γ ≈ 1.8) are very similar to those of Seyfert galaxies (Makishima et al. 1997, Serlemitsos et al. 1996). An iron emission line is observed from heavily absorbed low-luminosity AGNs (Makishima et al. 1997), while M81 is the only object among those with small intrinsic absorption from which an iron line detected (Ishisaki et al. 1996) on account of limited photon statistics for other objects.We summed up the ASCA spectra of 5 LINERs which host low-luminosity AGN of low intrinsic absorption to search for an iron emission line. We used 7 observations of 5 objects (NGC 1097, NGC 3310, NGC 3998, NGC 4450, and NGC 4594) to make a composite spectrum. All the objects have very similar X-ray characteristics (spectral slope, intrinsic absorption, no short time-scale variability; Iyomoto et al. 1996, Serlemitsos et al. 1996).

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X-ray properties of reverberation-mapped AGNs with super-Eddington accreting massive black holes

Proceedings of the International Astronomical Union ◽

10.1017/s1743921320002756 ◽

2019 ◽

Vol 15 (S356) ◽

pp. 143-143

Author(s):

Jaya Maithil ◽

Michael S. Brotherton ◽

Bin Luo ◽

Ohad Shemmer ◽

Sarah C. Gallagher ◽

...

Keyword(s):

Black Holes ◽

Black Hole ◽

Accretion Rate ◽

Time Lags ◽

Black Hole Mass ◽

Host Galaxies ◽

Massive Black Holes ◽

X Ray ◽

Photon Index ◽

The Impact

AbstractActive Galactic Nuclei (AGN) exhibit multi-wavelength properties that are representative of the underlying physical processes taking place in the vicinity of the accreting supermassive black hole. The black hole mass and the accretion rate are fundamental for understanding the growth of black holes, their evolution, and the impact on the host galaxies. Recent results on reverberation-mapped AGNs show that the highest accretion rate objects have systematic shorter time-lags. These super-Eddington accreting massive black holes (SEAMBHs) show BLR size 3-8 times smaller than predicted by the Radius-Luminosity (R-L) relationship. Hence, the single-epoch virial black hole mass estimates of highly accreting AGNs have an overestimation of a factor of 3-8 times. SEAMBHs likely have a slim accretion disk rather than a thin disk that is diagnostic in X-ray. I will present the extreme X-ray properties of a sample of dozen of SEAMBHs. They indeed have a steep hard X-ray photon index, Γ, and demonstrate a steeper power-law slope, ασx.

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The dark matter interpretation of the 3.5-keV line is inconsistent with blank-sky observations

Science ◽

10.1126/science.aaw3772 ◽

2020 ◽

Vol 367 (6485) ◽

pp. 1465-1467 ◽

Cited By ~ 6

Author(s):

Christopher Dessert ◽

Nicholas L. Rodd ◽

Benjamin R. Safdi

Keyword(s):

Dark Matter ◽

Emission Line ◽

Decay Rate ◽

Milky Way ◽

Line Emission ◽

Mass Range ◽

Sterile Neutrinos ◽

X Ray ◽

Upper Limit ◽

Nearby Galaxies

Observations of nearby galaxies and galaxy clusters have reported an unexpected x-ray emission line around 3.5 kilo–electron volts (keV). Proposals to explain this line include decaying dark matter—in particular, that the decay of sterile neutrinos with a mass around 7 keV could match the available data. If this interpretation is correct, the 3.5-keV line should also be emitted by dark matter in the halo of the Milky Way. We used more than 30 megaseconds of XMM-Newton (X-ray Multi-Mirror Mission) blank-sky observations to test this hypothesis, finding no evidence of the 3.5-keV line emission from the Milky Way halo. We set an upper limit on the decay rate of dark matter in this mass range, which is inconsistent with the possibility that the 3.5-keV line originates from dark matter decay.

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Structure and Emission Line Spectrum of an X-ray Heated Accretion Disk in AGN

Symposium - International Astronomical Union ◽

10.1017/s0074180900176600 ◽

1994 ◽

Vol 159 ◽

pp. 484-484

Author(s):

Yuan-Kuen Ko ◽

Timothy R. Kallman

Keyword(s):

Emission Line ◽

Active Galactic Nuclei ◽

Accretion Disk ◽

Line Emission ◽

Galactic Nuclei ◽

X Ray ◽

Disk Size ◽

Emission Line Spectrum ◽

Self Gravity ◽

A Site

We investigate the structure of an X-ray heated accretion disk in active galactic nuclei. It is found that X-ray heating can prevent the disk to be disrupted by its self-gravity under sufficient X-ray heating. The disk size can be two orders of magnitute larger than that limited by self-gravity of the disk without X-ray heating. An accretion disk corona will be formed by X-ray heating and can be a site for line emission. We present such emission line spectra which range from optical to hard X-ray energies and compare with the observational data.

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Dust Distribution in IRAS Seyfert Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900175539 ◽

1994 ◽

Vol 159 ◽

pp. 355-355

Author(s):

M. G. Pastoriza ◽

Charles Bonatto ◽

Eduardo Bica ◽

T. Storchi-Bergmann

Keyword(s):

Emission Line ◽

Power Law ◽

Dust Emission ◽

Seyfert Galaxies ◽

Emission Model ◽

Line Region ◽

Population Type ◽

The Galaxy ◽

Dilution Effects ◽

Dust Distribution

Observational evidences of dust in the nuclear region of AGNs are substantial (Rudy 1984, ApJ, 284, 33; Jones et al. 1984, PASP, 96, 692). The ionization cones observed in several Seyfert galaxies has been interpreted as shadowing effects by a dust obscuring torus which hides the broad emission line region (BLR) and the central source (Wilson 1992; Storchi-Bergmann, Mulchaey and Wilson 1992, ApJ 395, L73). A large sample of optical and far-IR data for IRAS Seyfert galaxies has been analysed together with dust emission models (Bonatto and Pastoriza 1993), where it has been concluded that the same dust emission model can be applied to both Seyfert types. In order to further study the effects of dust in the spectra of active galactic nuclei, we have obtained spectrophotometry of 21 IRAS Seyfert galaxies in the range 3500–7200 Å and analyse them in conjuction with their IRAS fluxes. The stellar population type is derived from comparisons with normal galaxy templates using dilution effects in the K CaII line as discriminator. For 55% of the sample the population is of late type. For the rest, blue continua due to recent star formation and/or power-law may amount up to 30% at 4000Å. We conclude that the bulge stellar populations of IRAS Seyfert galaxies are similar to those of normal spirals, except that they are more reddened by E(B-V)i ∼ 0.20. Population-subtracted emission line ratios indicate on average stronger reddening for the narrow-line region (E(B-V)l ∼ 0.8. From photoionization models a power-law index for the ionizing continuum α=1.5, and a metallicity larger than solar are obtained. The most luminous IRAS galaxy of the sample (IRAS555) is discuss in detail: in order to be compatible with the observed IRAS fluxes and the optical stellar continuum, the ionizing continuum must be reddened by AV > 10 magnitudes. Consequently a dust structure in this galaxy appears to be increasingly affecting stars and gas towards the galaxy center.

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