319 research outputs found
On the Abundance of Holmium in the Sun
The abundance of holmium (Z = 67) in the Sun remains uncertain. The
photospheric abundance, based on lines of Ho II, has been reported as +0.26 +/-
0.16 (on the usual scale where log(H) = 12.00), while the meteoretic value is
+0.51 +/- 0.02. Cowan code calculations have been undertaken to improve the
partition function for this ion by including important contributions from
unobserved levels arising from the (4f^{11}6p + 4f^{10}(5d + 6s)^{2}) group.
Based on 6994 computed energy levels, the partition function for Ho II is 67.41
for a temperature of 6000 K. This is approximately 1.5 times larger than the
value derived from the 49 published levels. The new partition function alone
leads to an increase in the solar abundance of Ho to log(Ho) = +0.43. This is
within 0.08 dex of the meteoretic abundance. Support for this result has been
obtained through LTE spectrum synthesis calculations of a previously
unidentified weak line at 3416.38 A in the solar spectrum. Attributing the
feature to Ho II, the observations may be fitted with log(Ho) = +0.53. This
calculation assumes log(gf) = 0.25 and is uncertain by at least 0.1 dex.Comment: 16 pages, 4 figures, accepted for publication in Solar Physic
Abundances in Przybylski's star
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74704/1/j.1365-8711.2000.03578.x.pd
A Re-Evaluation of the Abundance of Lutetium in the Sun
Lutetium is one of the few nonvolatile elements whose solar photospheric abundance departs significantly from that derived from CI chondrites. We have applied the Cowan code to compute new oscillator strengths for Luii, and have included a correction for core polarization. The results have been used in a synthesis of the solar spectrum in the vicinity of features at 3397.062 and 6221.72. We find that the majority of the absorption in the ultraviolet feature is due to NH, making it unsuitable for extracting a reliable lutetium abundance. Our best fit to the low-noise Jungfraujoch spectrum for the weak, nine-component hyperfine Luii line at λ 6221.87 yields an abundance of +0.06 on a scale where log(H) = 12.00. This value is within 0.07 dex of the meteoritic result (+0.13). (These figures reflect the note added in proof below.)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43714/1/11207_2004_Article_146254.pd
Spinning particle in an external linearized gravitational wave field
We study the interaction of a scalar and a spinning particle with a coherent
linearized gravitational wave field treated as a classical spin two external
field. The spin degrees of freedom of the spinning particle are described by
skew-commuting variables. We derive the explicit expressions for the
eigenfunctions and the Green's functions of the theory. The discussion is exact
within the approximation of neglecting radiative corrections and we prove that
the result is completely determined by the semiclassical contribution.Comment: 11 page
Lessons from Love-Locks: The archaeology of a contemporary assemblage
This document is the Accepted Manuscript version. The final, definitive version of this paper has been published in Journal of Material Culture, November 2017, published by SAGE Publishing, All rights reserved.Loss of context is a challenge, if not the bane, of the ritual archaeologist’s craft. Those who research ritual frequently encounter difficulties in the interpretation of its often tantalisingly incomplete material record. Careful analysis of material remains may afford us glimpses into past ritual activity, but our often vast chronological separation from the ritual practitioners themselves prevent us from seeing the whole picture. The archaeologist engaging with structured deposits, for instance, is often forced to study ritual assemblages post-accumulation. Many nuances of its formation, therefore, may be lost in interpretation. This paper considers what insights an archaeologist could gain into the place, people, pace, and purpose of deposition by recording an accumulation of structured deposits during its formation, rather than after. To answer this, the paper will focus on a contemporary depositional practice: the love-lock. This custom involves the inscribing of names/initials onto a padlock, its attachment to a bridge or other public structure, and the deposition of the corresponding key into the water below; a ritual often enacted by a couple as a statement of their romantic commitment. Drawing on empirical data from a three-year diachronic site-specific investigation into a love-lock bridge in Manchester, UK, the author demonstrates the value of contemporary archaeology in engaging with the often enigmatic material culture of ritual accumulations.Peer reviewe
An Atlas of K-line Spectra for Cool Magnetic CP Stars: The Wing-Nib Anomaly (WNA)
We present a short atlas illustrating the unusual Ca {\sc ii} K-line profiles
in upper main sequence stars with anomalous abundances. Slopes of the profiles
for 10 cool, magnetic chemically peculiar (CP) stars change abruptly at the
very core, forming a deep "nib." The nibs show the same or nearly the same
radial velocity as the other atomic lines. The near wings are generally more
shallow than in normal stars. In three magnetic CP stars, the K-lines are too
weak to show this shape, though the nibs themselves are arguably present. The
Ca {\sc ii} H-lines also show deep nibs, but the profiles are complicated by
the nearby, strong H absorption. The K-line structure is nearly
unchanged with phase in CrB and Cir. Calculations, including
NLTE, show that other possibilities in addition to chemical stratification may
yield nib-like cores.Comment: 6 pages, 2 figures, and 8 figures; accepted for publication in ApJ
Reverberation Mapping Results for Five Seyfert 1 Galaxies
We present the results from a detailed analysis of photometric and
spectrophotometric data on five Seyfert 1 galaxies observed as a part of a
recent reverberation mapping program. The data were collected at several
observatories over a 140-day span beginning in 2010 August and ending in 2011
January. We obtained high sampling-rate light curves for Mrk 335, Mrk 1501,
3C120, Mrk 6, and PG2130+099, from which we have measured the time lag between
variations in the 5100 Angstrom continuum and the H-beta broad emission line.
We then used these measurements to calculate the mass of the supermassive black
hole at the center of each of these galaxies. Our new measurements
substantially improve previous measurements of MBH and the size of the broad
line-emitting region for four sources and add a measurement for one new object.
Our new measurements are consistent with photoionization physics regulating the
location of the broad line region in active galactic nuclei.Comment: 45 pages, 5 figures. Accepted for publication in ApJ. For a brief
video explaining the key results of this paper, see
http://www.youtube.com/user/OSUAstronom
Reverberation Mapping of the Seyfert 1 Galaxy NGC 7469
A large reverberation mapping study of the Seyfert 1 galaxy NGC 7469 has
yielded emission-line lags for Hbeta 4861 and He II 4686 and a central black
hole mass measurement of about 10 million solar masses, consistent with
previous measurements. A very low level of variability during the monitoring
campaign precluded meeting our original goal of recovering velocity-delay maps
from the data, but with the new Hbeta measurement, NGC 7469 is no longer an
outlier in the relationship between the size of the Hbeta-emitting broad-line
region and the AGN luminosity. It was necessary to detrend the continuum and
Hbeta and He II 4686 line light curves and those from archival UV data for
different time-series analysis methods to yield consistent results.Comment: 9 Pages, 7 figures, 6 tables. Accepted for publication in The
Astrophysical Journa
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