142 research outputs found
On The Fine Tuning and Physical Origin of Line-Locked Absorption Systems in Active Galaxies
Line locking (LL) of absorption line systems is a clear signature of the
dynamical importance of radiation pressure force in driving astrophysical
flows, with recent findings suggesting that it may be common in quasars
exhibiting multiple intrinsic narrow absorption-line (NAL) systems. In this
work we probe the phase space conducive to LL and follow the detailed
kinematics of those systems that may lock at the velocity separation of the CIV
doublet. We find that a small volume of the
phase-phase admits LL, suggesting a high-degree of fine-tuning between the
physical properties of locked systems. The stability of LL against quasar
luminosity variations is quantified with implications for the long-term
variability amplitude of quasars and the velocity-separation statistic between
multiple NAL systems. The high occurrence of LL by the CIV doublet implies that
the hidden extreme-UV emission from quasars is unlikely to be significantly
under-estimated by current models. Further, the ratio of the LL velocity to the
outflow velocity may serve as a powerful constraint on the composition of the
accelerating medium. We conclude that LL poses significant challenges to
current theories for the formation of non-intervening NAL systems, and
speculate that it may be a manifestation of expanding circumstellar shells
around asymptotic giant branch (AGB) stars in the quasar-host bulge.Comment: 22 pages, 13 figures, ApJ in pres
XMM-Newton Spectroscopy of the Starburst Dominated Ultra Luminous Infrared Galaxy NGC 6240
We present new XMM-Newton observation of the Ultra Luminous Infrared Galaxy
(ULIRG) NGC 6240. We analyze the reflecting grating spectrometer (RGS) data,
and data from the other instruments, and find a starburst dominated 0.5-3 keV
spectrum with global properties resembling those observed in M82 but with a
much higher luminosity. We show that the starburst region can be divided into
an outer zone, beyond a radius of about 2.1 kpc, with a gas temperature of
about 10^7 K and a central region with temperatures in the range (2-6) x 10^7
K. The gas in the outer region emits most of the observed Oviii Lyman-alpha
line and the gas in the inner region the emission lines of higher ionization
ions, including a strong Fexxv line. We also identify a small inner part, very
close to the active nuclei, with typical Seyfert 2 properties including a large
amount of photoionized gas producing a strong Fe K-alpha 6.4 keV line. The
combined abundance, temperature and emission measure analysis indicates super
solar Ne/O, Mg/O, Si/O, S/O and possibly also Fe/O. The analysis suggests
densities in the range of (0.07-0.28) x epsilon^(-1/2) cm^(-3) and a total
thermal gas mass of about 4 x 10^8 x epsilon^(1/2) solar masses, where epsilon
is the volume filling factor. We used a simple model to argue that a massive
starburst with an age of about 2 x 10^7 years can explain most of the observed
properties of the source. NGC 6240 is perhaps the clearest case of an X-ray
bright luminous AGN, in a merger, whose soft X-ray spectrum is dominated by a
powerful starburst.Comment: 10 pages, 6 diagrams, accepted by ApJ, added a few minor change
Continuum reverberation mapping of MCG 08-11-011
We report the results from a photometric reverberation mapping campaign
carried out with the C18 telescope at the Wise Observatory from 2019 to 2020,
targeting the active galactic nucleus (AGN) MCG 08-11-011. The monitoring was
conducted on a daily basis with specially designed narrow-band filters,
spanning from optical to near-infrared wavelengths ( to {\AA})
and avoiding prominent broad emission lines. We aim to measure inter-band
continuum time lags, determine the size-wavelength relation, and estimate the
host-subtracted AGN luminosity for this system. We used the point-spread
function photometry to extract the continuum light curves and measure the
inter-band time lags using several methods, including the interpolated
cross-correlation function, the z-transformed discrete correlation function, a
von Neumann estimator, JAVELIN (in spectroscopic and photometric mode), MICA,
and a multivariate correlation function. We find wavelength-dependent lags,
, up to 7 days between the multiband light curves of MCG
08-11-011. The observed lags are larger than predictions based on standard
thin-disk theory by a factor of . We discern a significantly steeper
() size-wavelength relation than the expected for a geometrically thin and optically thick accretion
disk, which may result from the contribution of diffuse continuum emission to
the flux. These results are similar to those found by previous continuum
reverberation mapping campaigns.Comment: arXiv admin note: text overlap with arXiv:2111.0738
The Properties and the Evolution of the Highly Ionized Gas in MR2251-178
We present the first XMM-Newton observations of the radio-quiet quasar
MR2251-178. We model the X-ray spectrum with two power laws, one at high
energies with a slope of \Gamma=1.6 and the other to model the soft excess with
a slope of \Gamma=2.9, both absorbed by at least two warm absorbers (WAs). The
high-resolution grating spectrum shows emission lines from N VI, O VII, O VIII,
Ne IX, and Ne X, as well as absorption lines from the low ionization ions O
III, O IV, and O V. A study of the spectral variations in MR2251-178 over a
period of 8.5 years yields that all X-ray observations can be fitted with the
above model. Luminosity variations over timescales of years seem to correlate
with the soft excess variations but not with the WA properties variations. The
overall picture is that of a stratified WA that enters and disappears from the
line-of-sight on timescales of several months. We also present the first FUSE
spectrum of MR2251-178. The general characteristics of the UV and X-ray
absorbers seem to be consistent.Comment: To appear in the proceedings of "AGN Physics with the SDSS", eds. G.
T. Richards and P. B. Hall (San Francisco: ASP) (2004), 4 pages including 3
figures, newpasp.st
Narrow Components within the Fe Kalpha Profile of NGC 3516: Evidence for the Importance of General Relativistic Effects?
We present results from a simultaneous Chandra HETG and XMM-Newton
observation of NGC 3516. We find evidence for several narrow components of Fe
Kalpha along with a broad line. We consider the possibility that the lines
arise in an blob of material ejected from the nucleus with velocity ~0.25c. We
also consider an origin in a neutral accretion disk, suffering enhanced
illumination at 35 and 175 gravitational radii, perhaps due to magnetic
reconnection. The presence of these narrow features indicates there is no
Comptonizing region along the line-of-sight to the nucleus. This in turn is
compelling support for the hypothesis that broad Fe Kalpha components are, in
general, produced by strong gravity.Comment: 12 pages, 3 color figures. LaTeX with postscript figures. Resubmitted
June 7 2002, to Astrophysical Journal Letter
The Chandra view of the Largest Quasar Lens SDSS J1029+2623
We present results from Chandra observations of the cluster lens SDSS
J1029+2623 at z_l=0.58, which is a gravitationally lensed quasar with the
largest known image separation. We clearly detect X-ray emission both from the
lensing cluster and the three lensed quasar images. The cluster has an X-ray
temperature of kT = 8.1 (+2.0, -1.2) keV and bolometric luminosity of L_X =
9.6e44 erg s^-1. Its surface brightness is centered near one of the brightest
cluster galaxies, and it is elongated East-West. We identify a subpeak
North-West of the main peak, which is suggestive of an ongoing merger. Even so,
the X-ray mass inferred from the hydrostatic equilibrium assumption appears to
be consistent with the lensing mass from the Einstein radius of the system. We
find significant absorption in the soft X-ray spectrum of the faintest quasar
image, which can be caused by an intervening material at either the lens or
source redshift. The X-ray flux ratios between the quasar images (after
correcting for absorption) are in reasonable agreement with those at optical
and radio wavelengths, and all the flux ratios are inconsistent with those
predicted by simple mass models. This implies that microlensing effect is not
significant for this system and dark matter substructure is mainly responsible
for the anomalous flux ratios.Comment: 35 pages, 8 figures. Accepted for publication in Ap
Supernova PTF12glz: a possible shock breakout driven through an aspherical wind
We present visible-light and ultraviolet (UV) observations of the supernova
PTF12glz. The SN was discovered and monitored in near-UV and R bands as part of
a joint GALEX and Palomar Transient Factory campaign. It is among the most
energetic Type IIn supernovae observed to date (~10^51erg). If the radiated
energy mainly came from the thermalization of the shock kinetic energy, we show
that PTF12glz was surrounded by ~1 solar mass of circumstellar material (CSM)
prior to its explosive death. PTF12glz shows a puzzling peculiarity: at early
times, while the freely expanding ejecta are presumably masked by the optically
thick CSM, the radius of the blackbody that best fits the observations grows at
~8000km/s. Such a velocity is characteristic of fast moving ejecta rather than
optically thick CSM. This phase of radial expansion takes place before any
spectroscopic signature of expanding ejecta appears in the spectrum and while
both the spectroscopic data and the bolometric luminosity seem to indicate that
the CSM is optically thick. We propose a geometrical solution to this puzzle,
involving an aspherical structure of the CSM around PTF12glz. By modeling
radiative diffusion through a slab of CSM, we show that an aspherical geometry
of the CSM can result in a growing effective radius. This simple model also
allows us to recover the decreasing blackbody temperature of PTF12glz.
SLAB-Diffusion, the code we wrote to model the radiative diffusion of photons
through a slab of CSM and evaluate the observed radius and temperature, is made
available on-line.Comment: Sumbitted to ApJ. Comments are welcom
Observations of Outflowing UV Absorbers in NGC 4051 with the Cosmic Origins Spectrograph
We present new Hubble Space Telescope (HST)/Cosmic Origins Spectrograph
observations of the Narrow-Line Seyfert 1 galaxy NGC 4051. These data were
obtained as part of a coordinated observing program including X-ray
observations with the Chandra/High Energy Transmission Grating (HETG)
Spectrometer and Suzaku. We detected nine kinematic components of UV
absorption, which were previously identified using the HST/Space Telescope
Imaging Spectrograph. None of the absorption components showed evidence for
changes in column density or profile within the \sim 10 yr between the STIS and
COS observations, which we interpret as evidence of 1) saturation, for the
stronger components, or 2) very low densities, i.e., n_H < 1 cm^-3, for the
weaker components. After applying a +200 km s^-1 offset to the HETG spectrum,
we found that the radial velocities of the UV absorbers lay within the O VII
profile. Based on photoionization models, we suggest that, while UV components
2, 5 and 7 produce significant O VII absorption, the bulk of the X-ray
absorption detected in the HETG analysis occurs in more highly ionized gas.
Moreover, the mass loss rate is dominated by high ionization gas which lacks a
significant UV footprint.Comment: 41 pages, 10 Figures; accepted for publication in the Astrophysical
Journa
Microlensing in H1413+117 : disentangling line profile emission and absorption in a broad absorption line quasar
On the basis of 16 years of spectroscopic observations of the four components
of the gravitationally lensed broad absorption line (BAL) quasar H1413+117,
covering the ultraviolet to visible rest-frame spectral range, we analyze the
spectral differences observed in the P Cygni-type line profiles and have used
the microlensing effect to derive new clues to the BAL profile formation. We
confirm that the spectral differences observed in component D can be attributed
to a microlensing effect lasting at least a decade. We show that microlensing
magnifies the continuum source in image D, leaving the emission line region
essentially unaffected. We interpret the differences seen in the absorption
profiles of component D as the result of an emission line superimposed onto a
nearly black absorption profile. We also find that the continuum source and a
part of the broad emission line region are likely de-magnified in component C,
while components A and B are not affected by microlensing. We show that
microlensing of the continuum source in component D has a chromatic dependence
compatible with the thermal continuum emission of a standard Shakura-Sunyaev
accretion disk. Using a simple decomposition method to separate the part of the
line profiles affected by microlensing and coming from a compact region from
the part unaffected by this effect and coming from a larger region, we
disentangle the true absorption line profiles from the true emission line
profiles. The extracted emission line profiles appear double-peaked, suggesting
that the emission is occulted by a strong absorber, narrower in velocity than
the full absorption profile, and emitting little by itself. We propose that the
outflow around H1413+117 is constituted by a high-velocity polar flow and a
denser, lower velocity disk seen nearly edge-on.Comment: Accepted for publication in Astronomy and Astrophysic
- …