7 research outputs found
A test of the failed disk wind scenario for the origin of the broad line region in active galactic nuclei
It has been recently proposed that the broad line region in active galactic
nuclei originates from dusty clouds driven from the accretion disk by radiation
pressure, at a distance from the black hole where the disk is cooler than the
dust sublimation temperature. We test this scenario by checking the consistency
of independent broad line region and accretion disk reverberation measurements,
for a sample of 11 well studied active galactic nuclei. We show that
independent disk and broad line region reverberation mapping measurements are
compatible with a universal disk temperature at the H{\beta} radius of
T[R(H{\beta})]=1670(231) K which is close to typical dust sublimation
temperatures.Comment: 4 pages, 2 figures. Accepted for publication on MNRA
The Discovery of a High Redshift X-ray Emitting QSO Very Close to the Nucleus of NGC 7319
A strong X-ray source only 8" from the nucleus of the Sy2 galaxy NGC 7319 in
Stephan's Quintet has been discovered by Chandra. We have identified the
optical counterpart and show it is a QSO with . It is also a ULX
with . From the optical spectra of the QSO
and interstellar gas in the galaxy (z = .022) we show that it is very likely
that the QSO and the gas are interacting.Comment: 8 figures, 5 color, minimized ps siz
Testing quasilinear modified Newtonian dynamics in the Solar System
A unique signature of the modified Newtonian dynamics (MOND) paradigm is its
peculiar behavior in the vicinity of the points where the total Newtonian
acceleration exactly cancels. In the Solar System, these are the saddle points
of the gravitational potential near the planets. Typically, such points are
embedded into low-acceleration bubbles where modified gravity theories a` la
MOND predict significant deviations from Newton's laws. As has been pointed out
recently, the Earth-Sun bubble may be visited by the LISA Pathfinder spacecraft
in the near future, providing a unique occasion to put these theories to a
direct test. In this work, we present a high-precision model of the Solar
System's gravitational potential to determine accurate positions and motions of
these saddle points and study the predicted dynamical anomalies within the
framework of quasi-linear MOND. Considering the expected sensitivity of the
LISA Pathfinder probe, we argue that interpolation functions which exhibit a
"faster" transition between the two dynamical regimes have a good chance of
surviving a null result. An example of such a function is the QMOND analog of
the so-called simple interpolating function which agrees well with much of the
extragalactic phenomenology. We have also discovered that several of Saturn's
outermost satellites periodically intersect the Saturn-Sun bubble, providing
the first example of Solar System objects that regularly undergo the MOND
regime.Comment: 18 pages, 21 figures. Submitted to Physical Review
Spitzer Space Telescope Measurements of Dust Reverberation Lags in the Seyfert 1 Galaxy NGC 6418
We present results from a fifteen-month campaign of high-cadence (~ 3 days)
mid-infrared Spitzer and optical (B and V ) monitoring of the Seyfert 1 galaxy
NGC 6418, with the objective of determining the characteristic size of the
dusty torus in this active galactic nucleus (AGN). We find that the 3.6 m
and 4.5 m flux variations lag behind those of the optical continuum by
days and days, respectively. We
report a cross-correlation time lag between the 4.5 m and 3.6 m flux
of days. The lags indicate that the dust emitting at 3.6
m and 4.5 m is located at a distance of approximately 1 light-month
(~ 0.03 pc) from the source of the AGN UV-optical continuum. The reverberation
radii are consistent with the inferred lower limit to the sublimation radius
for pure graphite grains at 1800 K, but smaller by a factor of ~ 2 than the
corresponding lower limit for silicate grains; this is similar to what has been
found for near-infrared (K-band) lags in other AGN. The 3.6 and 4.5 m
reverberation radii fall above the K-band
size-luminosity relationship by factors and ,
respectively, while the 4.5 m reverberation radius is only 27% larger than
the 3.6 m radius. This is broadly consistent with clumpy torus models, in
which individual optically thick clouds emit strongly over a broad wavelength
range.Comment: 13 pages, 9 figure
\u3cem\u3eSpitzer Space Telescope\u3c/em\u3e Measurements of Dust Reverberation Lags in the Seyfert 1 Galaxy NGC 6418
We present results from a 15 month campaign of high-cadence (~3 days) mid-infrared Spitzer and optical (B and V) monitoring of the Seyfert 1 galaxy NGC 6418, with the objective of determining the characteristic size of the dusty torus in this active galactic nucleus (AGN). . . .
For the remainder of the abstract, please visit:
http://dx.doi.org/10.1088/0004-637X/801/2/12