ABSTRACT We present an analysis of Mg ii λ2798 and Fe ii UV emission lines for archival Sloan Digital Sky Survey (SDSS) quasars to explore the diagnostics of the magnesium-to-iron abundance ratio in ...a broad-line region cloud. Our sample consists of 17,432 quasars selected from the SDSS Data Release 7 with a redshift range of 0.72 < z < 1.63. A strong anticorrelation between the Mg ii equivalent width (EW) and the Eddington ratio is found, while only a weak positive correlation is found between the Fe ii EW and the Eddington ratio. To investigate the origin of these differing behaviors of Mg ii and Fe ii emission lines, we perform photoionization calculations using the Cloudy code, where constraints from recent reverberation mapping studies are considered. We find from calculations that (1) Mg ii and Fe ii emission lines are created at different regions in a photoionized cloud, and (2) their EW correlations with the Eddington ratio can be explained by just changing the cloud gas density. These results indicate that the Mg ii/Fe ii flux ratio, which has been used as a first-order proxy for the Mg/Fe abundance ratio in chemical evolution studies with quasar emission lines, depends largely on the cloud gas density. By correcting this density dependence, we propose new diagnostics of the Mg/Fe abundance ratio for a broad-line region cloud. In comparing the derived Mg/Fe abundance ratios with chemical evolution models, we suggest that -enrichment by mass loss from metal-poor intermediate-mass stars occurred at z ∼ 2 or earlier.
We report a method of recovering degraded lead-acid batteries using an on–off constant current charge and short–large discharge pulse method. When the increases in inner impedance are within ∼20% of ...the initial impedance value, their system will permit discharge times to recover to a level approximately matching their initial time values. In one experiment, when the discharge time of a <5-year-old lead-acid battery used for engine starting had degraded to about 50% of its initial discharge capacity, the authors found that 80% of the initial state discharge time could be recovered and maintained via their method. In a separate experiment, a deep-cycle battery was forcibly degraded by 12 h of depletion at a constant current of 10 A discharged at a terminal voltage of 10.2 V. The results of that experiment show that use of their on–off constant current charge method for the deep-cycle battery (recovered at 80% initial discharge time) quadrupled the post-recovery discharge time in comparison with a battery recovered via constant voltage charge. Taken together, these results indicate that use of their proposed on–off constant current charge system can successfully recover both degraded engine start and deep-cycle lead-acid batteries.
We present the final results from a high sampling rate, multi-month, spectrophotometric reverberation mapping campaign undertaken to obtain either new or improved H{beta} reverberation lag ...measurements for several relatively low-luminosity active galactic nuclei (AGNs). We have reliably measured the time delay between variations in the continuum and H{beta} emission line in six local Seyfert 1 galaxies. These measurements are used to calculate the mass of the supermassive black hole at the center of each of these AGNs. We place our results in context to the most current calibration of the broad-line region (BLR) R{sub BLR}-L relationship, where our results remove outliers and reduce the scatter at the low-luminosity end of this relationship. We also present velocity-resolved H{beta} time-delay measurements for our complete sample, though the clearest velocity-resolved kinematic signatures have already been published.
A new, improved version of a cosmic crystallography method for constraining cosmic topology is introduced. Like the circles-in-the-sky method using CMB data, we work in a thin, shell-like region ...containing plenty of objects. Two pairs of objects (quadruplet) linked by a holonomy show a specific distribution pattern, and three filters of separation, vectorial condition, and lifetime of objects extract these quadruplets. Each object Pi is assigned an integer si, which is the number of candidate quadruplets including Pi as their members. Then an additional device of si-histogram is used to extract topological ghosts, which tend to have high values of si. In this paper we consider flat spaces with Euclidean geometry, and the filters are designed to constrain their holonomies. As the second filter, we prepared five types that are specialized for constraining specific holonomies: one for translation, one for half-turn corkscrew motion and glide reflection, and three for nth turn corkscrew motion for n = 4,3, and 6. Every multiconnected space has holonomies that are detected by at least one of these five filters.Our method is applied to the catalogs of toy quasars in flat Λ-CDM universes whose typical sizes correspond to z ~ 5. With these simulations our method is found to work quite well. These are the situations in which type-II pair crystallography methods are insensitive because of the tiny number of ghosts. Moreover, in the flat cases, our method should be more sensitive than the type-I pair (or, in general, n-tuplet) methods because of its multifilter construction and its independence from n.
Context.
A rich population of low-mass brown dwarfs and isolated planetary mass objects has been reported in the Upper Scorpius and Ophiuchus star-forming complex.
Aims.
We investigate the ...membership, nature, and properties of 17 of these isolated planetary mass candidates using low-resolution near-infrared spectra.
Methods.
We investigated the membership by looking for evidence of their youth using four diagnostics: the slope of the continuum between the
J
and
Ks
band, the
H
cont
, and the TLI-g gravity-sensitive indices. In addition, we compared the spectra to young and field (old) M and L-dwarf standards.
Results.
All the targets but one are confirmed as young ultracool objects, with spectral types between L0 and L6 and masses in the range 0.004–0.013
M
⊙
, according to evolutionary models. The status of the last target is unclear at this point.
Conclusions.
Only one possible contaminant has been identified among the 17 targets, suggesting that the contamination level of the original sample must be low (≲6%).
We discuss the origin of the optical variations in the narrow-line Seyfert 1 galaxy NGC 4051 and present the results of a cross-correlation study using X-ray and optical light curves spanning more ...than 12 years. The emission is highly variable in all wavebands, and the amplitude of the optical variations is found to be smaller than that of the X-rays, even after correcting for the contaminating host galaxy flux falling inside the photometric aperture. The optical power spectrum is best described by an unbroken power-law model with slope α= 1.4+0.6−0.2 and displays lower variability power than the 2–10 keV X-rays on all time-scales probed. We find the light curves to be significantly correlated at an optical delay of 1.2+1.0−0.3 d behind the X-rays. This time-scale is consistent with the light traveltime to the optical emitting region of the accretion disc, suggesting that the optical variations are driven by X-ray reprocessing. We show, however, that a model whereby the optical variations arise from reprocessing by a flat accretion disc cannot account for all the optical variability. There is also a second significant peak in the cross-correlation function, at an optical delay of 39+2.7−8.4 d. The lag is consistent with the dust sublimation radius in this source, suggesting that there is a measurable amount of optical flux coming from the dust torus. We discuss the origin of the additional optical flux in terms of reprocessing of X-rays and reflection of optical light by the dust.
We present the results of concurrent X-ray and optical monitoring of the Seyfert 1 galaxy Mrk 79 over a period of more than 5 yr. We find that on short to medium time-scales (days to a few tens of ...days) the 2–10 keV X-ray and optical u- and V-band fluxes are significantly correlated, with a delay between the bands consistent with 0 d. We show that most of these variations may be well reproduced by a model where the short-term optical variations originate from reprocessing of X-rays by an optically thick accretion disc. The optical light curves, however, also display long time-scale variations over thousands of days, which are not present in the X-ray light curve. These optical variations must originate from an independent variability mechanism and we show that they can be produced by variations in the (geometrically) thin disc accretion rate as well as by varying reprocessed fractions through changes in the location of the X-ray corona.
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