1,075 research outputs found
Interpreting broad emission-line variations I : Factors influencing the emission-line response
We investigate the sensitivity of the measured broad emission-line
responsivity dlog f_line/dlog f_cont to continuum variations in the context of
straw-man BLR geometries of varying size with fixed BLR boundaries, and for
which the intrinsic emission-line responsivity is known a priori. We find for a
generic emission-line that the measured responsivity, delay and maximum of the
cross-correlation function are correlated for characteristic continuum
variability timescales T_char less than the maximum delay for that line
tau_max(line) for a particular choice of BLR geometry and observer orientation.
The above correlations are manifestations of geometric dilution arising from
reverberation effects within the spatially extended BLR. When present,
geometric dilution reduces the measured responsivity, delay and maximum of the
cross-correlation function. We also find that the measured responsivity and
delay show a strong dependence on light-curve duration, with shorter campaigns
resulting in smaller than expected values, and only a weak dependence on
sampling rate.
The observed strong negative correlation between continuum level and line
responsivity found in previous studies cannot be explained by differences in
the sampling pattern, light-curve duration or in terms of purely geometrical
effects. To explain this and to satisfy the observed positive correlation
between continuum luminosity and BLR size in an individual source, the
responsivity-weighted radius must increase with increasing continuum
luminosity. For a BLR with fixed inner and outer boundaries this requires
radial surface emissivity distributions which deviate significantly from a
simple power-law, and in such a way that the intrinsic emission-line
responsivity increases toward larger BLR radii, in line with photoionisation
calculations.Comment: 21 pages, 17 figures, accepted for publication in MNRAS July 201
The broad emission-line region: the confluence of the outer accretion disc with the inner edge of the dusty torus
(Abridged) We investigate the observational characteristics of BLR geometries
in which the BLR clouds bridge the gap, both in distance and scale height,
between the outer accretion disc and the hot dust, forming an effective surface
of a "bowl". The gas dynamics are dominated by gravity, and we include the
effects of transverse Doppler shift, gravitational redshift and scale-height
dependent macro-turbulence. Our simple model reproduces many of the phenomena
observed in broad emission-line variability studies, including (i) the absence
of response in the core of the optical recombination lines on short timescales,
(ii) the enhanced red-wing response on short timescales, (iii) differences
between the measured delays for the HILs and LILs, and (iv) identifies
turbulence as a means of producing Lorentzian profiles (esp. for LILs) in low
inclination systems, and for suppressing significant continuum--emission-line
delays between the line wings and line core (esp. in LILs). A key motivation of
this work was to reveal the physical underpinnings of the reported measurements
of SMBH masses and their uncertainties. We find that SMBH masses derived from
measurements of the fwhm of the mean and rms profiles show the closest
correspondence between the emission lines in a single object, even though the
emission line fwhm is a more biased mass indicator with respect to inclination.
The predicted large discrepancies in the SMBH mass estimates between emission
lines at low inclination, as derived using the line dispersion, we suggest may
be used as a means of identifying near face-on systems. Our general results do
not depend on specific choices in the simplifying assumptions, but are in fact
generic properties of BLR geometries with axial symmetry that span a
substantial range in radially-increasing scale height supported by turbulence,
which then merge into the inner dusty TOR.Comment: 29 pages, 23 figures and 1 tabl
GEODYN system description, volume 1
A computer program for the estimation of orbit and geodetic parameters is presented. The areas in which the program is operational are defined. The specific uses of the program are given as: (1) determination of definitive orbits, (2) tracking instrument calibration, (3) satellite operational predictions, and (4) geodetic parameter estimation. The relationship between the various elements in the solution of the orbit and geodetic parameter estimation problem is analyzed. The solution of the problems corresponds to the orbit generation mode in the first case and to the data reduction mode in the second case
Detection limits for close eclipsing and transiting sub-stellar and planetary companions to white dwarfs in the WASP survey
We used photometric data from the WASP (Wide-Angle Search for Planets) survey
to explore the possibility of detecting eclipses and transit signals of brown
dwarfs, gas giants and terrestrial companions in close orbit around white
dwarfs. We performed extensive Monte Carlo simulations and we found that for
Gaussian random noise WASP is sensitive to companions as small as the Moon
orbiting a 12 white dwarf. For fainter stars WASP is sensitive to
increasingly larger bodies. Our sensitivity drops in the presence of co-variant
noise structure in the data, nevertheless Earth-size bodies remain readily
detectable in relatively low S/N data. We searched for eclipses and transit
signals in a sample of 194 white dwarfs in the WASP archive however, no
evidence for companions was found. We used our results to place tentative upper
limits to the frequency of such systems. While we can only place weak limits on
the likely frequency of Earth-sized or smaller companions; brown dwarfs and gas
giants (radius R) with periods 0.2 days must certainly be
rare (). More stringent constraints requires significantly larger white
dwarf samples, higher observing cadence and continuous coverage. The short
duration of eclipses and transits of white dwarfs compared to the cadence of
WASP observations appears to be one of the main factors limiting the detection
rate in a survey optimised for planetary transits of main sequence stars.Comment: 8 pages, 3 figure
Analysis of UV protection requirements and testing of candidate attenuators for the Haloe optical instrument
Results of calculations are presented which simulate photolytic processes occurring in HALOE gas calibration cells exposed to extra-terrestrial solar ultraviolet photons. These calculations indicate that significant photolysis takes place in two of the sapphire-enclosed cells over the exposure periods of the proposed mission. A subsequent laboratory investigation is also described in which a high-voltage discharge hydrogen light source is used in conjunction with a vacuum ultraviolet spectrograph. The UV emission from this lamp was used to expose two candidate UV attenuators (ZnSe and coated Ge) to ascertain their suitability as UV filters while maintaining original infrared optical properties. Both materials were found to be effectively opaque to vacuum UV radiaton and suffered no adverse effects regarding their infrared transmissivity
Investigation of the enhanced spatial density of submicron lunar ejecta between L values 1.2 and 3.0 in the earth's magnetosphere: Theory
Initial results from the measurement conducted by the dust particle experiment on the lunar orbiting satellite Lunar Explorer 35 (LE 35) were reported with the data interpreted as indicating that the moon is a significant source of micrometeroids. Primary sporadic and stream meteoroids impacting the surface of the moon at hypervelocity was proposed as the source of micron and submicron particles that leave the lunar craters with velocities sufficient to escape the moon's gravitational sphere of influence. No enhanced flux of lunar ejecta with masses greater than a nanogram was detected by LE 35 or the Lunar Orbiters. Hypervelocity meteoroid simulation experiments concentrating on ejecta production combined with extensive analyses of the orbital dynamics of micron and submicron lunar ejecta in selenocentric, cislunar, and geocentric space have shown that a pulse of these lunar ejecta, with a time correlation relative to the position of the moon relative to the earth, intercepts the earth's magnetopause surface (EMPs). As shown, a strong reason exists for expecting a significant enhancement of submicron dust particles in the region of the magnetosphere between L values of 1.2 and 3.0. This is the basis for the proposal of a series of experiments to investigate the enhancement or even trapping of submicron lunar ejecta in this region. The subsequent interaction of this mass with the upper-lower atmosphere of the earth and possible geophysical effects can then be studied
A Novel Approach for Detecting Outliers by Using Isolation Forest with Reducing Under Fitting Issue
The effectiveness of machine learning for a particular activity depends on a variety of parameters. The incident database's description and validity come first and primary. Information retrieval even during the training cycle is more challenging if there is a lot of repetitious, unimportant information or incomplete information available. It is good knowledge that running time for ML tasks is significantly impacted by conditions as follows and sorting stages. To increase the accuracy of any model data cleansing is essential. Without sufficient data scrubbing, no predictive model accuracy can begin. EDA, or exploratory data analysis, is the name of this procedure. In this study, we discussed outlier identification, one of many EDA processes for complete perfect data. In this research, we attempted to use the isolation forest approach to calculate the outlier factor. Then a model known as an outlier finding model is created. The problem of outlier detection leads to a collection of connected supervised learning for binary classification. We carry out in-depth tests on various datasets and demonstrate that in our latest outlier finding technique compare with the old way. Our approach yields superior outcomes in terms of accuracy, precision, recall & F-1 score. Additionally, we successfully lowered the machine learning algorithms' under fitting issue
Reception Ex Nihilo: Doubling, Improvisation, and Metatheater in the Plautine Comedy and Seinfeld
https://egrove.olemiss.edu/classics_lectures/1016/thumbnail.jp
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