67 research outputs found
The mass of the black hole in RE J1034+396
The black hole mass measurement in active galaxies is a challenge,
particularly in sources where the reverberation method cannot be applied. We
aim to determine the black hole mass in a very special object, RE J1034+396,
one of the two AGN with QPO oscillations detected in X-rays, and a single
bright AGN with optical band totally dominated by starlight. We fit the stellar
content using the code starlight, and the broad band disk contribution to
optical/UV/X-ray emission is modeled with optxagnf. We also determine the black
hole mass using several other independent methods. Various methods give
contradictory results. Most measurements of the blacc hole mass are in the
range 1.e6-1.e7 Msun, and the measurements based on dynamics give higher values
than measurements based on Hbeta and Mg II emission lines.Comment: A&A, in pres
RT Crucis: A look into the X-ray emission of a peculiar symbiotic star
© 2016 ESO.Symbiotic stars are a heterogeneous class of interacting binaries. Among them, RT Cru has been classified as prototype of a subclass that is characterised by hard X-ray spectra that extend past âŒ20 keV. We analyse âŒ8.6 Ms of archival INTEGRAL data collected during the period 2003-2014, ⌠140 ks of Swift/XRT data, and a Suzaku observation of 39 ks, to study the spectral X-ray emission and investigate the nature of the compact object. Based on the 2MASS photometry, we estimate the distance to the source of 1.2-2.4 kpc. The X-ray spectrum obtained with Swift/XRT, JEM-X, IBIS/ISGRI, and Suzaku data is well fitted by a cooling flow model modified by an absorber that fully covers the source and two partially covering absorbers. Assuming that the hard X-ray emission of RT Cru originates from an optically thin boundary layer around a non-magnetic white dwarf, we estimated a mass of the white dwarf of MWD â 1.2Mâ. The mass accretion rate obtained for this source might be too high for the optically thin boundary layer scenario. Therefore we investigate other plausible scenarios to model its hard X-ray emission. We show that, alternatively, the observed X-ray spectrum can be explained with the X-ray emission from the post-shock region above the polar caps of a magnetised white dwarf with mass MWD â 0.9-1.1Mâ
Universal spectral shape of high accretion rate AGN
The spectra of quasars and NLS1 galaxies show surprising similarity in their
spectral shape. They seem to scale only with the accretion rate. This is in
contradiction with the simple expectations from the standard disk model which
predicts lower disk temperature for higher black hole mass. Here we consider
two mechanisms modifying the disk spectrum: the irradiation of the outer disk
due to the scattering of the flux by the extended ionized medium (warm absorber
and the development of the warm Comptonizing disk skin under the effect of the
radiation pressure instability. Those two mechanisms seem to lead to a spectrum
which indeed roughly scales, as observed, only with the accretion rate. The
scenario applies only to objects with relatively high luminosity to the
Eddington luminosity ratio for which disk evaporation is inefficient.Comment: 14 pages, 14 figures, 1 table, accepted for publication in A&
Constraints on the black hole spin in the quasar SDSS J094533.99+100950.1
The spin of the black hole is an important parameter which may be responsible
for the properties of the inflow and outflow of the material surrounding a
black hole. Broad band IR/optical/UV spectrum of the quasar SDSS
J094533.99+100950.1 is clearly disk-dominated, with the spectrum peaking up in
the observed frequency range. Therefore, disk fitting method usually used for
Galactic black holes can be used in this object to determine the black hole
spin. We develop the numerical code for computing disk properties, including
radius-dependent hardening factor, and we apply the ray-tracing method to
incorporate all general relativity effects in light propagation. We show that
the simple multicolor disk model gives a good fit, without any other component
required, and the disk extends down to the marginally stable orbit. The best
fit accretion rate is 0.13, well below the Eddington limit, and the black hole
spin is moderate, 0.3. The contour error for the fit combined with the
constraints for the black hole mass and the disk inclination gives a constraint
that the spin is lower than 0.8. We discuss the sources of possible systematic
errors in the parameter determinations
Narrow-line Seyfert 1 galaxies: an amasing class of AGN
[Abridged] Narrow-line Seyfert 1 (NLS1) galaxies are a class of active
galactic nuclei (AGN) that have all the properties of type 1 Seyfert galaxies
but show peculiar characteristics, including the narrowest Balmer lines,
strongest Fe II emission, and extreme properties in the X-rays. Line and
continuum radio observations provide an optimal tool to access the (often)
optically obscured innermost regions of AGN and reveal the kinematics of the
gas around their central engines. We investigate the interplay between the
peculiar NLS1 class of AGN and the maser phenomenon, to help us understand the
nature of the maser emission in some NLS1s where water maser emission has been
detected. We observed a sample of NLS1 galaxies with the Green Bank Telescope
in a search for water maser emission at 22 GHz. We also reduced and analysed
archival Green Bank Telescope and Very Large Array data and produced 22-GHz
spectra for the five NLS1 galaxies with detected maser emission. In particular,
we imaged the maser and nuclear radio continuum of NGC5506 at subarcsec scales
with the Very Large Array. We discovered maser emission in two NLS1 galaxies:
IGRJ16385-2057, and IRAS03450+0055. In addition to the three previously known
maser detections in the NLS1s Mrk766, NGC4051, and NGC5506, this yields a water
maser detection rate in NLS1 galaxies of ~7% (5/71). This value rises
significantly to ~21% (5/24) when considering only NLS1 galaxies at recessional
velocities less than 10000 km/s. For NGC4051 and NGC5506, we find that the
water maser emission is located within 5 and 12 pc, respectively, of nuclear
radio continuum knots, which are interpreted as core-jet structures.Comment: 11 pages, 5 figures, 2 tables. Accepted by Astronomy & Astrophysic
Relationships between serum adiponectin and soluble TNF-α receptors and glucose and lipid oxidation in lean and obese subjects
Insulin resistance might be associated with an impaired ability of insulin to stimulate glucose oxidation and inhibit lipid oxidation. Insulin action is also inversely associated with TNF-α system and positively related to adiponectin. The aim of the present study was to analyze the associations between serum adiponectin, soluble TNF-α receptors concentrations and the whole-body insulin sensitivity, lipid and glucose oxidation, non-oxidative glucose metabolism (NOGM) and metabolic flexibility in lean and obese subjects. We examined 53 subjects: 25 lean (BMI < 25 kg Ă mâ2) and 28 with overweight or obesity (BMI > 25 kg Ă mâ2) with normal glucose tolerance. Hyperinsulinemic euglycemic clamp and indirect calorimetry were performed. An increase in respiratory exchange ratio in response to insulin was used as a measure of metabolic flexibility. Obese subjects had lower insulin sensitivity, adiponectin and higher sTNFR1 (all P < 0.001) and sTNFR2 (P = 0.001). Insulin sensitivity was positively related to adiponectin (r = 0.49, P < 0.001) and negatively related to sTNFR1 (r = â0.40, P = 0.004) and sTNFR2 (r = â0.52, P < 0.001). Adiponectin was related to the rate of glucose (r = 0.47, P < 0.001) and lipid (r = â0.40, P = 0.003) oxidation during the clamp, NOGM (r = 0.41, P = 0.002) and metabolic flexibility (r = 0.36, P = 0.007). Serum sTNFR1 and sTNFR2 were associated with the rate of glucose (r = â0.45, P = 0.001; r = â0.51, P < 0.001, respectively) and lipid (r = 0.52, P < 0.001; r = 0.46, P = 0.001, respectively) oxidation during hyperinsulinemia, NOGM (r = â0.31, P = 0.02; r = â0.43, P = 0.002, respectively) and metabolic flexibility (r = â0.47 and r = â0.51, respectively, both P < 0.001) in an opposite manner than adiponectin. Our data suggest that soluble TNF-α receptors and adiponectin have multiple effects on glucose and lipid metabolism in obesity
Contribution a l'etude de resonateurs dielectriques: application des resonateurs partiellement metallises a la realisation d'oscillateurs UHF
SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : T 79184 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc
RT Crucis: A look into the X-ray emission of a peculiar symbiotic star
© 2016 ESO.Symbiotic stars are a heterogeneous class of interacting binaries. Among them, RT Cru has been classified as prototype of a subclass that is characterised by hard X-ray spectra that extend past âŒ20 keV. We analyse âŒ8.6 Ms of archival INTEGRAL data collected during the period 2003-2014, ⌠140 ks of Swift/XRT data, and a Suzaku observation of 39 ks, to study the spectral X-ray emission and investigate the nature of the compact object. Based on the 2MASS photometry, we estimate the distance to the source of 1.2-2.4 kpc. The X-ray spectrum obtained with Swift/XRT, JEM-X, IBIS/ISGRI, and Suzaku data is well fitted by a cooling flow model modified by an absorber that fully covers the source and two partially covering absorbers. Assuming that the hard X-ray emission of RT Cru originates from an optically thin boundary layer around a non-magnetic white dwarf, we estimated a mass of the white dwarf of MWD â 1.2Mâ. The mass accretion rate obtained for this source might be too high for the optically thin boundary layer scenario. Therefore we investigate other plausible scenarios to model its hard X-ray emission. We show that, alternatively, the observed X-ray spectrum can be explained with the X-ray emission from the post-shock region above the polar caps of a magnetised white dwarf with mass MWD â 0.9-1.1Mâ
RT Crucis: A look into the X-ray emission of a peculiar symbiotic star
© 2016 ESO.Symbiotic stars are a heterogeneous class of interacting binaries. Among them, RT Cru has been classified as prototype of a subclass that is characterised by hard X-ray spectra that extend past âŒ20 keV. We analyse âŒ8.6 Ms of archival INTEGRAL data collected during the period 2003-2014, ⌠140 ks of Swift/XRT data, and a Suzaku observation of 39 ks, to study the spectral X-ray emission and investigate the nature of the compact object. Based on the 2MASS photometry, we estimate the distance to the source of 1.2-2.4 kpc. The X-ray spectrum obtained with Swift/XRT, JEM-X, IBIS/ISGRI, and Suzaku data is well fitted by a cooling flow model modified by an absorber that fully covers the source and two partially covering absorbers. Assuming that the hard X-ray emission of RT Cru originates from an optically thin boundary layer around a non-magnetic white dwarf, we estimated a mass of the white dwarf of MWD â 1.2Mâ. The mass accretion rate obtained for this source might be too high for the optically thin boundary layer scenario. Therefore we investigate other plausible scenarios to model its hard X-ray emission. We show that, alternatively, the observed X-ray spectrum can be explained with the X-ray emission from the post-shock region above the polar caps of a magnetised white dwarf with mass MWD â 0.9-1.1Mâ
- âŠ