922 research outputs found
Analysing the Suzaku Spectra of the Broad-Line Seyfert 1 Galaxy CBS 126
We analysed new simultaneous \emph{Suzaku} and \emph{Swift} data of the Broad
Line Seyfert 1 (BLS1) galaxy CBS 126. A clear Fe emission line and a strong
soft excess are present in the source spectra. We fit the spectra with a
relativistic reflection model and find the model tends to fit the data with a
high iron abundance possibly due to the large soft excess present. By checking
the difference and the RMS spectra, we find there is likely an absorption edge
at 0.89 keV, which might be caused by oxygen or neon. We also produced
an analysis of the time-resolved spectra in order to examine the existence of
the edge. Although high iron abundance is required more in the time-resolved
spectra, a model of solar iron abundance together with an absorption edge gives
a more physical explanation. Variation of the ionisation parameter is an
alternative, plausible explanation for the excess seen in the difference
spectra. It is difficult to know if there are warm absorbers in this source
from the current data. To further investigate the presence of possible warm
absorbers, higher signal-to-noise low-energy data are needed. The work
presented here tentatively suggests that the spectra of a BLS1 can be explained
by a relativistic reflection model similar to that often seen in their
narrow-line cousins.Comment: 10 pages, 12 figures, accepted for publication in MNRA
Seyfert galaxies with Swift: giant flares, rapid drops, and other surprises
Swift has initiated a new era of understanding the extremes of active
galactic nuclei (AGN) variability, their drivers and underlying physics. This
is based on its rapid response, high sensitivity, good spatial resolution, and
its ability to collect simultaneously X--ray-to-optical SEDs. Here, we present
results from our recent monitoring campaigns with Swift of highly variable AGN,
including outbursts, deep low states, and unusual long-term trends in several
Seyfert galaxies including Mrk 335, WPVS007, and RXJ2314.9+2243. We also report
detection of a new X-ray and optical outburst of IC 3599 and our Swift
follow-ups. IC 3599 was previously known as one of the AGN with the
highest-amplitude outbursts. We briefly discuss implications of this second
outburst of IC 3599 for emission scenarios including accretion-disk
variability, repeat tidal disruption events, and the presence of a binary
supermassive black hole.Comment: to appear in "Swift: 10 years of discovery", Proceedings of Scienc
Discovery of an Ultrasoft X-ray Transient Source in the 2XMM Catalog: a Tidal Disruption Event Candidate
We have discovered an ultrasoft X-ray transient source, 2XMMi
J184725.1-631724, which was detected serendipitously in two XMM-Newton
observations in the direction of the center of the galaxy IC 4765-f01-1504 at a
redshift of 0.0353. These two observations were separated by 211 days, with the
0.2-10 keV absorbed flux increasing by a factor of about 9. Their spectra are
best described by a model dominated by a thermal disk or a single-temperature
blackbody component (contributing >80% of the flux) plus a weak power-law
component. The thermal emission has a temperature of a few tens of eV, and the
weak power-law component has a photon index of ~3.5. Similar to the black hole
X-ray binaries in the thermal state, our source exhibits an accretion disk
whose luminosity appears to follow the relation. This would
indicate that the black hole mass is about 10^5-10^6 M_sun using the
best-fitting inner disk radius. Both XMM-Newton observations show variability
of about 21% on timescales of hours, which can be explained as due to fast
variations in the mass accretion rate. The source was not detected by ROSAT in
an observation in 1992, indicating a variability factor of >64 over longer
timescales. The source was not detected again in X-rays in a Swift observation
in 2011 February, implying a flux decrease by a factor of >12 since the last
XMM-Newton observation. The transient nature, in addition to the extreme
softness of the X-ray spectra and the inactivity of the galaxy implied by the
lack of strong optical emission lines, makes it a candidate tidal disruption
event. If this is the case, the first XMM-Newton observation would have been in
the rising phase, and the second one in the decay phase.Comment: 12 pages, 6 figures. Accepted for publication in Ap
A Complete Sample of Soft X-ray Selected AGN: II. Statistical Analysis
Direct correlations and a Principal Component Analysis (PCA) are presented
for a complete sample of 110 soft X-ray selected AGN of which about half are
Narrow-Line Seyfert 1 galaxies (NLS1s). The direct correlation analyses show
that narrower FWHM(H-beta) correlates with steeper X-ray spectrum, stronger
optical FeII emission, weaker [OIII] emission and stronger short-term X-ray
variability. This direct correlation analysis and the PCA confirm the Boroson &
Green (1992) Eigenvector 1 relationship for AGN: FeII strength anti-correlates
with [OIII] line strength. Eigenvector 1 is well-correlated with the Eddington
luminosity ratio L/L_Edd while Eigenvector 2 shows a very good correlation with
the mass of the central black hole and the mass accretion rate. The Eddington
ratio L/L_Edd correlates with the X-ray spectral index alpha-X and the black
home mass anti-correlates with the X-ray variability chi^2/nu. The Eddington
ration L/L_Edd may be interpreted as the age of an AGN: AGN with steep X-ray
spectra, strong FeII, and weak [OIII] are AGN in an early phase of their
evolution. In this hypothesis NLS1s are young AGN.Comment: Accepted for publication in AJ (April 2004), 21 pages, 13 figure
XMM-Newton observations of SDSS J143030.22001115.1: an unusually flat spectrum AGN
We present XMM observations of the AGN SDSS 1430-0011. The low S/N spectrum
of this source obtained in a snap shot Chandra observation showed an unusually
flat continuum. With the follow up XMM observations we find that the source
spectrum is complex; it either has an ionized absorber or a partially covering
absorber. The underlying power-law is in the normal range observed for AGNs.
The low luminosity of the source during Chandra observations can be understood
in terms of variations in the absorber properties. The X-ray and optical
properties of this source are such that it cannot be securely classified as
either a narrow line Seyfert 1 or a broad line Seyfert 1 galaxy.Comment: Submitted to A
First XMM-Newton study of two Narrow-Line Seyfert 1 galaxies discovered in the Sloan Digital Sky Survey
The Early Data Release of the Sloan Digital Sky Survey (SDSS) contains 150
Narrow-Line Seyfert 1 (NLS1) galaxies, most of them previously unknown. We
present here the study of the X-ray emission from two of these active galaxies
(SDSS J030639.57+000343.2 and SDSS J141519.50-003021.6), based upon XMM-Newton
observations. The spectral and timing characteristics of the two sources are
presented and compared against the typical properties of known NLS1 galaxies.
We found that these two NLS1 are within the dispersion range of the typical
values of this class of AGN, although with some interesting features that
deserve further studies.Comment: 5 pages, 8 figures. Accepted for publication on A&A Main Journa
Radio Loud AGN in the Context of the Eigenvector 1 Parameter Space
We consider the properties of radio-loud (RL) AGN in the context of the
Eigenvector 1 (E1) parameter space. RL sources show a restricted E1 parameter
space occupation relative to the radio-quiet (RQ) majority. The Fanaroff-Riley
II ``parent population'' of relatively un-boosted RL sources (median
radio/optical flux ratio ~490) shows the most restricted occupation. RL sources
have different broad line properties (and inferred black hole masses and
Eddington ratios). FWHM H_beta for the broad line component in RL sources are
at least twice as large as the RQ majority. The average broad FeII emission
line strength is also about half that for RQ sources. Our sample suggests that
the RL cutoff occurs near R_k=70 or logP(6cm)=32.0 ergs/s/Hz. Sources below
this cutoff are RQ although we cannot rule out the existence of a distinct
intermediate population. We show that the Doppler boosted core-dominated RL
sources (median flux ratio ~1000) lie towards smaller FWHM(H_beta_bc) and
stronger FeII in E1 as expected if the lines arise in an accretion disk. Our
subsample of superluminal sources, with orientation inferred from the
synchrotron self Compton model, reinforce this general E1 trend and allow us to
estimate the role of source orientation in driving E1 domain occupation.Comment: 9 pages, 3 figures, accepted for publication in ApJ
Survey of finance companies, 1996
Finance companies are major suppliers of credit to consumers and businesses. The sector is made up of roughly 1,250 nondepository financial institutions, with 20 firms accounting for three-fourths of the receivables. The Federal Reserve System has been surveying the assets and liabilities of finance companies, typically at five-year intervals, since June 1955. This article summarizes the results of the 1996 survey. Special features of that survey are a breakdown of automobile leases into consumer and business components and, relative to previous surveys, greater detail on the composition of real estate credit and more information on securitized loans and leases.Finance companies
Probing the Ionizing Continuum of Narrow-Line Seyfert 1 Galaxies. I.Observational Results
We present optical spectra and emission-line ratios of 12 Narrow-Line Seyfert
1 (NLS1) galaxies that we observed to study the ionizing EUV continuum. A
common feature in the EUV continuum of active galactic nuclei is the big blue
bump (BBB), generally associated with thermal accretion disk emission. While
Galactic absorption prevents direct access to the EUV range, it can be mapped
by measuring the strength of a variety of forbidden optical emission lines that
respond to different EUV continuum regions. We find that narrow emission-line
ratios involving [OII]3727, Hbeta, [OIII]5007, [OI]6300, Halpha,[NII]6583, and
[SII]6716,6731 indicate no significant difference between NLS1s and Broad-Line
Seyfert 1 (BLS1) galaxies, which suggests that the spectral energy
distributions of their ionizing EUV - soft X-ray continua are similar. The
relative strength of important forbidden high ionization lines like [NeV]3426
compared to HeII4686 and the relative strength of [FeX]6374 appear to show the
same range as in BLS1 galaxies. However, a trend of weaker
F([OI]6300)/F(Halpha) emission-line ratios is indicated for NLS1s compared to
BLS1s. To recover the broad emission-line profiles we used Gaussian components.
This approach indicates that the broad Hbeta profile can be well described with
a broad component (FWHM = 3275 +- 800 km/s) and an intermediate broad component
(FWHM = 1200 +- 300 km/s). The width of the broad component is in the typical
range of normal BLS1s. The emission-line flux that is associated with the broad
component in these NLS1s amounts to at least 60% of the total flux. Thus it
dominates the total line flux, similar to BLS1 galaxies.Comment: 34 pages, 9 figures. accepted for publication in the
Astrophys.Journa
SDSS J143030.22-001115.1: A misclassified narrow-line Seyfert 1 galaxy with flat X-ray spectrum
We used multi-component profiles to model H and [O III]4959,5007 lines for SDSS J143030.22-001115.1, a narrow-line Seyfert 1
galaxy (NLS1) in a sample of 150 NLS1s candidates selected from the Sloan
Digital Sky Survey (SDSS) Early Data Release (EDR). After subtracting the
H contribution from narrow line regions (NLRs), we found that its full
width half maximum (FWHM) of broad H line is nearly 2900 \kms,
significantly larger than the customarily adopted criterion of 2000 \kms. With
its weak Fe II multiples, we think that SDSS J143030.22-001115.1 can't be
classified as a genuine NLS1. When we calculate the virial black hole masses of
NLS1s, we should use the H linewidth after subtracting the H
contribution from NLRs.Comment: 7 pages, 1 table, accepted by ChJA
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