1,906 research outputs found
The Rowan County War
An article published in the January 1910 World Wide Magazine by Edward T. Moran (a.k.a. Cora Wilson Stewart) on the Rowan County War
Polarized Broad-Line Emission from Low-Luminosity Active Galactic Nuclei
In order to determine whether unified models of active galactic nuclei apply
to low-luminosity objects, we have undertaken a spectropolarimetric survey of
of LINERs and Seyfert nuclei at the Keck Observatory. The 14 objects observed
have a median H-alpha luminosity of 8x10^{39} erg/s, well below the typical
value of ~10^{41} erg/s for Markarian Seyfert nuclei. Polarized broad H-alpha
emission is detected in three LINERs: NGC 315, NGC 1052, and NGC 4261. Each of
these is an elliptical galaxy with a double-sided radio jet, and the
emission-line polarization in each case is oriented roughly perpendicular to
the jet axis, as expected for the obscuring torus model. NGC 4261 and NGC 315
are known to contain dusty circumnuclear disks, which may be the outer
extensions of the obscuring tori. The detection of polarized broad-line
emission suggests that these objects are nearby, low-luminosity analogs of
obscured quasars residing in narrow-line radio galaxies. The nuclear continuum
of the low-luminosity Seyfert 1 galaxy NGC 4395 is polarized at p = 0.67%,
possibly the result of an electron scattering region near the nucleus.
Continuum polarization is detected in other objects, with a median level of p =
0.36% over 5100-6100 A, but in most cases this is likely to be the result of
transmission through foreground dust. The lack of significant broad-line
polarization in most type 1 LINERs is consistent with the hypothesis that we
view the broad-line regions of these objects directly, rather than in scattered
light.Comment: 28 pages, including 3 tables and 16 figures. Uses the emulateapj
latex style file. Accepted for publication in The Astrophysical Journa
Transient and Highly Polarized Double-Peaked H-alpha Emission in the Seyfert 2 Nucleus of NGC 2110
We have discovered an extremely broad, double-peaked H-alpha emission line in
the polarized flux spectrum of NGC 2110, establishing that this well-studied
Seyfert 2 galaxy contains a disk-like hidden broad-line region (BLR). Several
properties of NGC 2110 suggest that it is an obscured twin of Arp 102B, the
prototypical double-peaked emission-line active galactic nucleus (AGN). A
comparison between our data and previous spectra of NGC 2110 indicates that the
double-peaked H-alpha feature is transient. The presence of a disk-like BLR in
NGC 2110 has important implications for AGNs: it expands the range of
properties exhibited by Seyfert 2 galaxies, and the fact that the BLR is
obscured by a torus-like structure provides the first evidence that
double-peaked emitters and classical Seyfert nuclei may have the same basic
parsec-scale geometry.Comment: 5 pages, including 3 postscript figures. Uses emulateapj. Accepted
for publication in ApJ Letter
A Black Hole in the X-Ray Nova Velorum 1993
We have obtained 17 moderate-resolution (~2.5 A) optical spectra of the
Galactic X-ray Nova Velorum 1993 in quiescence with the Keck-II telescope. The
orbital period (P) is 0.285206 +/- 0.0000014 d, and the semiamplitude (K_2) is
475.4 +/- 5.9 km/s. Our derived mass function, f(M_1) = PK_2^3 /2 pi G = 3.17
+/- 0.12 M_sun, is close to the conventional absolute limiting mass for a
neutron star (~ 3.0-3.2 M_sun) -- but if the orbital inclination i is less than
80 degrees (given the absences of eclipses), then M_1 is greater than 4.2-4.4
M_sun for nominal secondary-star masses of 0.5 M_sun (M0) to 0.65 M_sun (K6).
The primary star is therefore almost certainly a black hole rather than a
neutron star. The velocity curve of the primary from H-alpha emission has a
semiamplitude (K_1) of 65.3 +/- 7.0 km/s, but with a phase offset by 237
degrees (rather than 180 degrees) from that of the secondary star. The nominal
mass ratio q = M_2/M_1 = K_1/K_2 = 0.137 +/- 0.015, and hence for M_2 =
0.5-0.65 M_sun we derive M_1 = 3.64-4.74 M_sun. An adopted mass M_1 ~ 4.4 M_sun
is significantly below the typical value of ~ 7 M_sun found for black holes in
other low-mass X-ray binaries.
Keck observations of MXB 1659-29 (V2134 Oph) in quiescence reveal a probable
optical counterpart at R = 23.6 +/- 0.4 mag.Comment: 16 pages, 9 figures, added references, revised per. referee's
comments Accepted for publication in August 1999 issue of PAS
A Composite Seyfert 2 X-ray Spectrum: Implications for the Origin of the Cosmic X-ray Background
We present a composite 1-10 keV Seyfert 2 X-ray spectrum, derived from ASCA
observations of a distance-limited sample of nearby galaxies. All 29 observed
objects were detected. Above ~3 keV, the composite spectrum is inverted,
confirming that Seyfert 2 galaxies as a class have the spectral properties
necessary to explain the flat shape of the cosmic X-ray background spectrum.
Integrating the composite spectrum over redshift, we find that the total
emission from Seyfert 2 galaxies, combined with the expected contribution from
unabsorbed type 1 objects, provides an excellent match to the spectrum and
intensity of the hard X-ray background. The principal uncertainty in this
procedure is the cosmic evolution of the Seyfert 2 X-ray luminosity function.
Separate composite spectra for objects in our sample with and without polarized
broad optical emission lines are also presented.Comment: 11 pages (AASTeX), including 3 figures. Accepted for publication in
ApJ Letter
Assigning the right credit to the wrong action: compulsivity in the general population is associated with augmented outcome-irrelevant value-based learning.
Funder: NIHR Senior InvestigatorCompulsive behavior is enacted under a belief that a specific act controls the likelihood of an undesired future event. Compulsive behaviors are widespread in the general population despite having no causal relationship with events they aspire to influence. In the current study, we tested whether there is an increased tendency to assign value to aspects of a task that do not predict an outcome (i.e., outcome-irrelevant learning) among individuals with compulsive tendencies. We studied 514 healthy individuals who completed self-report compulsivity, anxiety, depression, and schizotypal measurements, and a well-established reinforcement-learning task (i.e., the two-step task). As expected, we found a positive relationship between compulsivity and outcome-irrelevant learning. Specifically, individuals who reported having stronger compulsive tendencies (e.g., washing, checking, grooming) also tended to assign value to response keys and stimuli locations that did not predict an outcome. Controlling for overall goal-directed abilities and the co-occurrence of anxious, depressive, or schizotypal tendencies did not impact these associations. These findings indicate that outcome-irrelevant learning processes may contribute to the expression of compulsivity in a general population setting. We highlight the need for future research on the formation of non-veridical action-outcome associations as a factor related to the occurrence and maintenance of compulsive behavior
Crystal Structure Of 7-[(2e)-2-benzyl-idene-3-oxobut-oxy]-4-methyl-2h-chromen-2-one.
Two independent mol-ecules (A and B) comprise the asymmetric unit of the title compound, C21H18O4. There are significant conformational differences between the mol-ecules relating in particular to the relative orientation of the 3-oxo-2-(phenyl-methyl-idene)but-oxy substituent with respect to the superimposable chromen-2-one residues. To a first approximation, the substituents are mirror images; both are approximately perpendicular to the chromen-2-one fused ring system with dihedral angles of 88.50 (7) (A) and 81.96 (7)° (B). Another difference between the independent mol-ecules is noted in the dihedral angles between the adjacent phenyl and but-3-en-2-one groups of 8.72 (12) (A) and 27.70 (10)° (B). The conformation about the ethene bond in both mol-ecules is E. The crystal packing features C-H⋯O, C-H⋯π(ar-yl) and π-π [Cg⋯Cg = 3.6657 (8) and 3.7778 (8) Å] stacking inter-actions, which generate a three-dimensional network.71o222-22
The Discovery of the First "Changing Look" Quasar: New Insights into the Physics & Phenomenology of AGN
SDSS J015957.64+003310.5 is an X-ray selected, AGN from the Stripe
82X survey that transitioned from a Type 1 quasar to a Type 1.9 AGN between
2000 and 2010. This is the most distant AGN, and first quasar, yet observed to
have undergone such a dramatic change. We re-observed the source with the
double spectrograph on the Palomar 5m telescope in July 2014 and found that the
spectrum is unchanged since 2010. From fitting the optical spectra, we find
that the AGN flux dropped by a factor of 6 between 2000 and 2010 while the
broad H emission faded and broadened. Serendipitous X-ray observations
caught the source in both the bright and dim state, showing a similar 2-10 keV
flux diminution as the optical while lacking signatures of obscuration. The
optical and X-ray changes coincide with -band magnitude variations over
multiple epochs of Stripe 82 observations. We demonstrate that variable
absorption, as might be expected from the simplest AGN unification paradigm,
does not explain the observed photometric or spectral properties. We interpret
the changing state of J0159+0033 to be caused by dimming of the AGN continuum,
reducing the supply of ionizing photons available to excite gas in the
immediate vicinity around the black hole. J0159+0033 provides insight into the
intermittency of black hole growth in quasars, as well as an unprecedented
opportunity to study quasar physics (in the bright state) and the host galaxy
(in the dim state), which has been impossible to do in a single sources until
now.Comment: accepted for publication in Ap
Ethyl (E)-2-methoxyimino-2-(4-nitrobenzoyl)acetate
The title molecule, C12H12N2O6, features an E conformation about the oxime group. The methoxyimino and ester residues are effectively coplanar with each other (r.m.s. deviation for the nine non-H atoms = 0.127 Å) and almost orthogonal [with dihedral angles of 99.44 (13) and −77.85 (13)°, respectively] to the carbonyl and nitrophenyl groups which lie to either side of this central plane. The crystal structure is consolidated by C—H⋯O contacts
(Z)-Ethyl 2-hydroxyimino-2-(4-nitrobenzyl)ethanoate
The title molecule, C11H10N2O6, has a Z conformation about the C=N bond of the oxime unit. There are significant twists from planarity throughout the molecule, the most significant being between the hydroxyimino and ester groups which are effectively orthogonal with an N—C—C—Ocarbonyl torsion angle of 91.4 (2)°. The crystal packing features oxime–benzoyl O—H⋯O contacts that lead to chains along [010] and C—H⋯O interactions also occur
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