297 research outputs found
Chandra and XMM Observations of the ADC Source 0921-630
We analyze observations of the low mass X-ray binary 2S0921-63 obtained with
the gratings and CCDs on Chandra and XMM. This object is a high inclination
system showing evidence for an accretion disk corona (ADC). Such a corona has
the potential to constrain the properties of the heated accretion disk in this
system, and other LMXBs by extension. We find evidence for line emission which
is generally consistent with that found by previous experiments, although we
are able to detect more lines. For the first time in this source, we find that
the iron K line has multiple components. We set limits on the line widths and
velocity offsets, and we fit the spectra to photoionization models and discuss
the implications for accretion disk corona models. For the first time in any
ADC source we use these fits, together with density constraints based on the O
VII line ratio, in order to constrain the flux in the medium-ionization region
of the ADC. Under various assumptions about the source luminosity this
constrains the location of the emitting region. These estimates, together with
estimates for the emission measure, favor a scenario in which the intrinsic
luminosity of the source is comparable to what we observe.Comment: 40 pages, 11 figures submitted to Ap.
The Compact Structure of Radio-Loud Broad Absorption Line Quasars
We present the results of EVN+MERLIN VLBI polarization observations of 8
Broad Absorption Line (BAL) quasars at 1.6 GHz, including 4 LoBALs and 4 HiBALs
with either steep or flat spectra on VLA scales. Only one steep-spectrum
source, J1122+3124, shows two-sided structure on the scale of 2 kpc. The other
four steep-spectrum sources and three flat-spectrum sources display either an
unresolved image or a core-jet structure on scales of less than three hundred
parsecs. In all cases the marginally resolved core is the dominant radio
component. Linear polarization in the cores has been detected in the range of a
few to 10 percent. Polarization, together with high brightness temperatures
(from 2*10^9-5*10^10 K), suggest a synchrotron origin for the radio emission.
There is no apparent difference in the radio orphologies or polarization
between low-ionization and high-ionization BAL QSOs nor between flat- and
steep-spectrum sources. We discuss the orientation of BAL QSOs with both flat
and steep spectra, and consider a possible evolutionary scenario for BAL QSOs.
In this scenario, BAL QSOs are probably the young population of radio sources,
which are Compact Steep Spectrum or GHz peaked radio source analog at the low
end of radio power.Comment: 16 pages, 3 figures, 4 tables; accepted for publication in MNRA
IRAS observations of active galaxies
The IRAS survey gives an unbiased view of the infrared properties of the active galaxies. Seyfert galaxies occupy much the same area in color-color plots as to normal infrared bright galaxies, but extend the range towards flatter 60 to 25 mm slopes. Statistically the Seyfert 1 galaxies can be distinguished from the Seyfert 2 galaxies, lying predominantly closer to the area with constant slopes between 25 and 200 mm. The infrared measurements of the Seyfert galaxies cannot distinguish between the emission mechanisms in these objects although they agree with the currently popular ideas; they do provide a measure of the total luminosity of the Seyferts. The quasar's position in the color-color diagrams continue the trend of the Seyferts. The quasar 3C48 is shown to be exceptional among the radio loud quasars in that it has a high infrared luminosity which dominates the power output of the quasar and is most likely associated with the underlying host galaxy
Ultraviolet observations of the X-ray photoionized wind of Cygnus X-1 during X-ray soft/high state
(Shortened) Ultraviolet observations of the black hole X-ray binary Cygnus
X-1 were obtained using the STIS on HSTubble. We detect P Cygni line features
show strong, broad absorption components when the X-ray source is behind the
companion star and noticeably weaker absorption when the X-ray source is
between us and the companion star. We fit the P Cygni profiles using the SEI
method applied to a spherically symmetric stellar wind subject to X-ray
photoionization from the black hole. The Si IV doublet provides the most
reliable estimates of the parameters of the wind and X-ray illumination. The
velocity increases with radius according to
, with and
km s.The microturbulent velocity was
km s. Our fit implies a ratio of X-ray luminosity to wind mass-loss rate
of L, measured at = 4.8. Our
models determine parameters that may be used to estimate the accretion rate
onto the black hole and independently predict the X-ray luminosity. Our
predicted L matches that determined by contemporaneous RXTE ASM remarkably
well, but is a factor of 3 lower than the rate according to
Bondi-Hoyle-Littleton spherical wind accretion. We suggest that some of the
energy of accretion may go into powering a jet.Comment: 34 pages, 21 figures, 4 tables, accepted for publication in Ap
The Black Hole Mass - Galaxy Bulge Relationship for QSOs in the SDSS DR3
We investigate the relationship between black hole mass and host galaxy
velocity dispersion for QSOs in Data Release 3 of the Sloan Digital Sky Survey.
We derive black hole mass from the broad Hbeta line width and continuum
luminosity, and the bulge stellar velocity dispersion from the [OIII] narrow
line width. At higher redshifts, we use MgII and [OII] in place of Hbeta and
[OIII]. For redshifts z < 0.5, our results agree with the black hole mass -
bulge velocity dispersion relationship for nearby galaxies. For 0.5 < z < 1.2,
this relationship appears to show evolution with redshift in the sense that the
bulges are too small for their black holes. However, we find that part of this
apparent trend can be attributed to observational biases, including a Malmquist
bias involving the QSO luminosity. Accounting for these biases, we find ~0.2
dex evolution in the black hole mass-bulge velocity dispersion relationship
between now and redshift z ~ 1.Comment: Accepted by ApJ, 15 pages, 9 figure
Enhanced Star Formation in Narrow Line Seyfert 1 AGN revealed by Spitzer
We present new low resolution Spitzer mid-infrared spectroscopy of a sample
of 20 ROSAT selected local Narrow Line Seyfert 1 galaxies (NLS1s). We detect
strong AGN continuum in all and clear PAH emission in 70% of the sources. The
6.2 micron PAH luminosity spans three orders of magnitudes, from ~10^(39) erg/s
to ~10^(42) erg/s providing strong evidence for intense ongoing star formation
in the circumnuclear regions of these sources. Using the IRS/Spitzer archive we
gather a large number of additional NLS1s and their broad line counterparts
(BLS1s) and constructed NLS1 and BLS1 sub-samples to compare them in various
ways. The comparison shows a clear separation according to FWHM(H_beta) such
that objects with narrower broad H_beta lines are the strongest PAH emitters.
We test this division in various ways trying to remove biases due to luminosity
and aperture size. Specifically, we find that star formation activity around
NLS1 AGN is larger than around BLS1 of the same AGN luminosity. The above
result seems to hold over the entire range of distance and luminosity. Moreover
the star formation rate is higher in low black hole mass and high L/L_Edd
systems indicating that black hole growth and star formation are occurring
simultaneously.Comment: 30 pages, 11 figures, 4 tables. Now accepted in MNRA
The Intrinsic Absorber in QSO 2359-1241: Keck and HST Observations
We present detailed analyses of the absorption spectrum seen in QSO 2359-1241
(NVSS J235953-124148). Keck HIRES data reveal absorption from twenty
transitions arising from: He I, Mg I, Mg II, Ca II, and Fe II. HST data show
broad absorption lines (BALs) from Al III 1857, C IV 1549, Si IV 1397, and N V
1240. Absorption from excited Fe II states constrains the temperature of the
absorber to 2000K < T < 10,000K and puts a lower limit of 10^5 cm^{-3} on the
electron number density. Saturation diagnostics show that the real column
densities of He I and Fe II can be determined, allowing to derive meaningful
constraints on the ionization equilibrium and abundances in the flow. The
ionization parameter is constrained by the iron, helium and magnesium data to
-3.0 < log(U) < -2.5 and the observed column densities can be reproduced
without assuming departure from solar abundances. From comparison of the He I
and Fe II absorption features we infer that the outflow seen in QSO 2359-1241
is not shielded by a hydrogen ionization front and therefore that the existence
of low-ionization species in the outflow (e.g., Mg II, Al III, Fe II) does not
necessitate the existence of such a front. We find that the velocity width of
the absorption systematically increases as a function of ionization and to a
lesser extent with abundance. Complementary analyses of the radio and
polarization properties of the object are discussed in a companion paper
(Brotherton et al. 2000).Comment: 30 pages, 9 figures, in press with the Ap
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