144 research outputs found
The polarization properties of Broad Absorption Line QSOs: observational results
Correlations between BAL QSO intrinsic properties and polarization have been
searched for. Some results are summarized here, providing possible constraints
on BAL outflow models.Comment: 4 pages, 5 figures; to appear in ``Mass Outflow in Active Galactic
Nuclei: New Perspectives'' ASP Conference Series, eds. D.M. Crenshaw, S.B.
Kraemer, and I.M. Georg
Large-scale coherent orientations of quasar polarisation vectors: interpretation in terms of axion-like particles
The observation of redshift-dependent coherent orientations of quasar
polarisation vectors over cosmological distances in some regions of the sky is
reviewed. Based on a good-quality sample of 355 measured quasars, this
observation seems to infer the existence of a new effect acting on light
propagation on such huge distances. A solution in terms of nearly massless
axion-like particles has been proposed in the literature and its current status
is discussed.Comment: Replaced because of a previously badly displayed caption. Contributed
to "Axions 2010", Gainesville (FL), January 15-17 2010. To be published in
AIP conference series. 6 page
Sub-arcsecond imaging and spectroscopy of the radio-loud highly polarized quasar PKS 1610-771
We report on imaging and spectroscopic observations of the radio-loud, highly
polarized quasar PKS 1610-771 (z = 1.71). Our long-slit spectroscopy of the
companion 4.55 arcseconds NW of the quasar confirms the stellar nature of this
object, so ruling out the previously suspected gravitationally lensed nature of
this system. PKS 1610-771 looks fuzzy on our sub-arcsecond R and I images and
appears located in a rich environment of faint galaxies. Possible
magnification, without image splitting of the quasar itself, by some of these
maybe foreground galaxies cannot be excluded. The continuum fuzz (made of the
closest two objects, viz. A and D) is elongated in a direction orthogonal to
the E vector of the optical polarization, as in high-redshift radio-galaxies.
The spectrum of PKS 1610-771 appears strongly curved, in a convex way, with a
maximum of intensity at ~ 7,600 A (2,800 A rest frame), possibly indicating a
strong ultraviolet absorption by dust.Comment: 6 pages, uuencoded gziped tar file including TeX file + postscript
figures. Accepted for publication in A&A main journa
The atypical emission-line star Hen3-209
We analyse observations, spanning 15 years, dedicated to the extreme
emission-line object Hen3-209. Our photometric data indicate that the
luminosity of the star undergoes marked variations with a peak-to-peak
amplitude of 0.65mag. These variations are recurrent, with a period of
16.093+-0.005d. The spectrum of Hen3-209 is peculiar with many different lines
(HI, HeI, FeII,...) showing P Cygni profiles. The line profiles are apparently
changing in harmony with the photometry. The spectrum also contains [OIII]
lines that display a saddle profile topped by three peaks, with a maximum
separation of about 600km/s. Hen3-209 is most likely an evolved luminous object
suffering from mass ejection events and maybe belonging to a binary system.Comment: 6p, 5 fig, accepted for publication in MNRAS
(www.blackwell-synergy.com
HST Observations of the Gravitationally Lensed Cloverleaf Broad Absorption Line QSO H1413+1143: Modeling the Lens
We investigate gravitational lens models for the quadruply-lensed Cloverleaf
BAL QSO H1413+1143 based on the HST WFPC/WFPC2 astrometric and photometric data
of the system by Turnshek et al. and the HST NICMOS-2 data by Falco et al. The
accurate image positions and the dust-extinction-corrected relative
amplifications, along with a possible detection of the lensing galaxy in the
infrared, permit more accurate lens models than were previously possible. While
more recent models are qualitatively consistent with the HST data, none of the
previous models considered the dust-extinction-corrected relative
amplifications of the image components. We use the power-law elliptical mass
model to fit the HST data. We find that a single elliptical galaxy perturbed by
an external shear can fit the image positions within the observational
uncertainties; however, the predicted relative magnifications are only roughly
consistent with the observational relative amplifications. We find that a
primary galaxy combined with a secondary galaxy in the vicinity of the
Cloverleaf or a cluster centered (south-)west of the Cloverleaf can fit both
the image positions and relative amplifications within the observational
uncertainties. We discuss future observations which could be used to test
and/or further constrain lens models of the Cloverleaf.Comment: 23 pages (in aaspp.sty) including 5 tables and 3 figures, Accepted
for publication in the Astrophysical Journa
Strong Gravitational Lensing and the Structure of Quasar Outflows
We show that by analyzing the spectra of lensed broad absorption line quasars
(BALQSOs), it is possible to reveal key properties of the outflowing gas in the
inner regions of these objects. This results from the fact that each image of
the quasar corresponds to a different line of sight through the outflow. This
combined with dynamical estimates for the location of the flow, adds new
information concerning the lateral, non line of sight structure of the
absorbing gas. Here we consider a sample of lensed BALQSOs and note that the
similarity of BAL profiles of different images of the same quasar implies that
the flow is relatively isotropic on small scales. We show that its geometry is
inconsistent with the ballistically accelerated spherical cloud model, and that
wind models provide a better description of the flow structure. Furthermore,
observations seem to disagree with naive interpretations of recent
time-dependent wind simulations. This may hint on several important physical
processes that govern the structure and dynamics of such flows. Future
prospects for the study of quasar outflows with the effect of strong
gravitational lensing are discussed.Comment: 4 pages, 1 figure, accepted for publication in ApJ
TRAPPIST: a robotic telescope dedicated to the study of planetary systems
We present here a new robotic telescope called TRAPPIST (TRAnsiting Planets
and PlanetesImals Small Telescope). Equipped with a high-quality CCD camera
mounted on a 0.6 meter light weight optical tube, TRAPPIST has been installed
in April 2010 at the ESO La Silla Observatory (Chile), and is now beginning its
scientific program. The science goal of TRAPPIST is the study of planetary
systems through two approaches: the detection and study of exoplanets, and the
study of comets. We describe here the objectives of the project, the hardware,
and we present some of the first results obtained during the commissioning
phase.Comment: To appear in Detection and Dynamics of Transiting Exoplanets,
Proceedings of Haute Provence Observatory Colloquium (23-27 August 2010),
eds. F. Bouchy, R.F. Diaz & C.Moutou, Platypus press 201
Submillimetre observations of a sample of broad absorption line quasars
The broad absorption line (BAL) features seen in a small fraction of quasar
optical/UV spectra are attributed to bulk outflows away from the quasar core.
Observational evidence suggests that dust plays a key role in these systems,
although whether the inferred dust properties are a signature of orientation
effects or whether they are indicative of an evolutionary sequence remains an
outstanding issue. Submillimetre (submm) detections of BAL quasars (BALQSOs),
which would clearly help to resolve this issue, have so far been sparse. This
paper reports on new submm observations of seven BALQSOs. The strongest
influence on the observed flux is found to be the redshift, with the two
highest redshift sources appearing intrinsically more submm-luminous than the
lower redshift ones. Since this trend is also seen in other high redshift AGN,
including non-BAL quasars it implies that the dust emission properties of these
systems are no different from those of the general AGN population, which is
difficult to reconcile with the evolutionary interpretation of the BAL
phenomenon.Comment: 5 Pages, to appear in ApJ Letter
Herschel imaging and spectroscopy of the nebula around the luminous blue variable star WRAY 15-751
We have obtained far-infrared Herschel PACS imaging and spectroscopic
observations of the nebular environment of the luminous blue variable WRAY
15-751. These images clearly show that the main, dusty nebula is a shell of
radius 0.5 pc and width 0.35 pc extending outside the H-alpha nebula. They also
reveal a second, bigger and fainter dust nebula, observed for the first time.
Both nebulae lie in an empty cavity, likely the remnant of the O-star wind
bubble formed when the star was on the main sequence. The kinematic ages of the
nebulae are about 20000 and 80000 years and each nebula contains about 0.05
Msun of dust. Modeling of the inner nebula indicates a Fe-rich dust. The
far-infrared spectrum of the main nebula revealed forbidden emission lines
coming from ionized and neutral gas. Our study shows that the main nebula
consists of a shell of ionized gas surrounded by a thin photodissociation
region illuminated by an "average" early-B star. The derived abundance ratios
N/O=1.0+/-0.4 and C/O=0.4+/-0.2 indicate a mild N/O enrichment. We estimate
that the inner shell contains 1.7+/-0.6 Msun of gas. Assuming a similar
dust-to-gas ratio for the outer nebula, the total mass ejected by WRAY 15-751
amounts to 4+/-2 Msun. The measured abundances, masses and kinematic ages of
the nebulae were used to constrain the evolution of the star and the epoch at
which the nebulae were ejected. Our results point to an ejection of the nebulae
during the RSG evolutionary phase of an ~ 40 Msun star. The presence of
multiple shells around the star suggests that the mass-loss was not a
continuous ejection but rather a series of episodes of extreme mass-loss. Our
measurements are compatible with the recent evolutionary tracks computed for an
40 Msun star with little rotation. They support the O-BSG-RSG-YSG-LBV filiation
and the idea that high-luminosity and low-luminosity LBVs follow different
evolutionary paths.Comment: 19 pages, 13 figures, accepted for publication in A&
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