pinecone/core-2020-05-10-deduplication huggingface dataset:
Prospects of Stellar Abundance Studies from Near-IR Spectra Observed
  with the E-ELT

In 2006 ESO Council authorized a Phase B study of a European AO-telescope
with a 42 m segmented primary with a 5-mirror design, the E-ELT. Several
reports and working groups have already presented science cases for an E-ELT,
specifically exploiting the new capabilities of such a large telescope. One of
the aims of the design has been to find a balance in the performances between
an E-ELT and the James Webb Space Telescope, JWST. Apart from the larger
photon-collecting area, the strengths of the former is the higher attainable
spatial and spectral resolutions. The E-ELT AO system will have an optimal
performance in the near-IR, which makes it specially advantageous.
High-resolution spectroscopy in the near-infrared has, however, not been
discussed much. This paper aims at filling that gap, by specifically discussing
spectroscopy of stellar (mainly red giant), photospheric abundances. Based on
studies in the literature of stellar abundances, at the needed medium to high
spectral resolutions in the near-infrared (0.8-2.4 microns), I will try to
extrapolate published results to the performance of the E-ELT and explore what
could be done at the E-ELT in this field. A discussion on what instrument
characteristics that would be needed for stellar abundance analyses in the
near-IR will be given.Comment: Accepted for publication in Astronomische Nachrichten, A
Masses and Luminosities of O and B - type stars and red super giants

Massive stars are of interest as progenitors of super novae, i.e. neutron
stars and black holes, which can be sources of gravitational waves. Recent
population synthesis models can predict neutron star and gravitational wave
observations but deal with a fixed super nova rate or an assumed initial mass
function for the population of massive stars. Here we investigate those massive
stars, which are supernova progenitors, i.e. with O and early B type stars, and
also all super giants within 3kpc. We restrict our sample to those massive
stars detected both in 2MASS and observed by Hipparcos, i.e. only those stars
with parallax and precise photometry. To determine the luminosities we
calculated the extinctions from published multi-colour photometry, spectral
types, luminosity class, all corrected for multiplicity and recently revised
Hipparcos distances. We use luminosities and temperatures to estimate the
masses and ages of these stars using different models from different authors.
Having estimated the luminosities of all our stars within 3kpc, in particular
for all O- and early B-type stars, we have determined the median and mean
luminosities for all spectral types for luminosity classes I, III, and V. Our
luminosity values for super giants deviate from earlier results: Previous work
generally overestimates distances and luminosities compared to our data, this
is likely due to Hipparcos parallaxes (generally more accurate and larger than
previous ground-based data) and the fact that many massive stars have recently
been resolved into multiples of lower masses and luminosities. From
luminosities and effective temperatures we derived masses and ages using mass
tracks and isochrones from different authors. From masses and ages we estimated
lifetimes and derived a lower limit for the supernova rate of ~20 events/Myr
averaged over the next 10 Myrs within 600 pc from the sun. These data are then
used to search for areas in the sky with higher likelihood for a supernova or
gravitational wave event (like OB associations).Comment: 13 pages, 13 figures, submitted to AN Dec 12 200
Spectroscopy of Solar Neutrinos

In the last years, liquid-scintillator detectors have opened a new window for
the observation of low-energetic astrophysical neutrino sources. In 2007, the
solar neutrino experiment Borexino began its data-taking in the Gran Sasso
underground laboratory. High energy resolution and excellent radioactive
background conditions in the detector allow the first-time spectroscopic
measurement of solar neutrinos in the sub-MeV energy regime. The experimental
results of the Beryllium-7 neutrino flux measurements as well as the prospects
for the detection of solar Boron-8, pep and CNO neutrinos are presented in the
context of the currently discussed ambiguities in solar metallicity. In
addition, the potential of the future SNO+ and LENA experiments for
high-precision solar neutrino spectroscopy will be outlined.Comment: 6 pages, 5 figures, highlight talk at the annual fall meeting of the
  German Astronomische Gesellschaft in Potsdam (Sep 2009
Relationship between group sunspot number and Wolf sunspot number

Continuous wavelet transform and cross-wavelet transform have been used to
investigate the phase periodicity and synchrony of the monthly mean Wolf
($R_{z}$) and group ($R_{g}$) sunspot numbers during the period of June 1795 to
December 1995. The Schwabe cycle is the only one common period in Rg and Rz,
but it is not well-defined in case of cycles 5-7 of Rg and in case of cycles 5
and 6 of $R_{z}$. In fact, the Schwabe period is slightly different in $R_{g}$
and $R_{z}$ before cycle 12, but from cycle 12 onwards it is almost the same
for the two time series. Asynchrony of the two time series is more obviously
seen in cycles 5 and 6 than in the following cycles, and usually more obviously
seen around the maximum time of a cycle than during the rest of the cycle.
$R_{g}$ is found to fit $R_{z}$ better in both amplitudes and peak epoch during
the minimum time time of a solar cycle than during the maximum time of the
cycle, which should be caused by their different definition, and around the
maximum time of a cycle, $R_{g}$ is usually less than $R_{z}$. Asynchrony of
$R_{g}$ and $R_{z}$ should somewhat agree with different sunspot cycle
characteristics exhibited by themselves
Numerical Modelling of the Vertical Structure and Dark Halo Parameters
  in Disc Galaxies

The non-linear dynamics of bending instability and vertical structure of a
galactic stellar disc embedded into a spherical halo are studied with N-body
numerical modelling. Development of the bending instability in stellar galactic
disc is considered as the main factor that increases the disc thickness.
Correlation between the disc vertical scale height and the halo-to-disc mass
ratio is predicted from the simulations. The method of assessment of the
spherical-to-disc mass ratio for edge-on spiral galaxies with small bulges is
considered. Modelling of eight edge-on galaxies: NGC 891, NGC 4738, NGC 5170,
UGC 6080, UGC 7321, UGC 8286, UGC 9422 and UGC 9556 is performed. Parameters of
stellar discs, dark haloes and bulges are estimated. The lower limit of the
dark-to-luminous mass ratio in our galaxies is of the order of 1 within the
limits of their stellar discs. The dark haloes dominate by mass in the galaxies
with very thin stellar discs (NGC 5170, UGC 7321 and UGC 8286).Comment: Accepted by the Astronomische Nachrichte
The exceptional Herbig Ae star HD101412: The first detection of resolved
  magnetically split lines and the presence of chemical spots in a Herbig star

We obtained high-resolution, high signal-to-noise UVES and a few lower
quality HARPS spectra revealing the presence of resolved magnetically split
lines. HD101412 is the first Herbig Ae star for which the rotational Doppler
effect was found to be small in comparison to the magnetic splitting. The
measured mean magnetic field modulus varies from 2.5 to 3.5kG, while the mean
quadratic field was found to vary in the range of 3.5 to 4.8kG. To determine
the period of variations, we used radial velocity, equivalent width, line
width, and line asymmetry measurements of variable spectral lines of several
elements, as well as magnetic field measurements. The most pronounced
variability was detected for spectral lines of He I and the iron peak elements,
whereas the spectral lines of CNO elements are only slightly variable. From
spectral variations and magnetic field measurements we derived a potential
rotation period P_rot=13.86d, which has to be proven in future studies with a
larger number of observations. It is the first time that the presence of
element spots is detected on the surface of a Herbig Ae/Be star. Our previous
study of Herbig Ae stars revealed a trend towards stronger magnetic fields for
younger Herbig Ae stars, confirmed by statistical tests. This is in contrast to
a few other (non-statistical) studies claiming that magnetic Herbig Ae stars
are progenitors of the magnetic Ap stars. New developments in MHD theory show
that the measured magnetic field strengths are compatible with a current-driven
instability of toroidal fields generated by differential rotation in the
stellar interior. This explanation for magnetic intermediate-mass stars could
be an alternative to a frozen-in fossil field.Comment: 7 pages, 6 figures, 1 table, to appear in Astronomische Nachrichte
The calculation of longitude and latitude from geodesic measurements

The solution of the geodesic problem for an oblate ellipsoid is developed in
terms of series. Tables are provided to simplify the computation. [This is an
English translation of F. W. Bessel, Astronomische Nachrichten 4(86), 241-254
(1825). The mathematical notation has been updated to conform to current
conventions and, in a few places, the equations have been rearranged for
clarity. Several errors have been corrected, a figure has been included, and
the tables have been recomputed.]Comment: 11 pages, including 1 figure and 4 pages of tables. Version 2 and 3
  fix some minor errors. This translation was edited by Charles F. F. Karney
  and Rodney E. Deakin. A transcription of the original paper is available at
  arXiv:0908.1823 . For links to other 18th and 19th century papers on
  geodesics, see
  http://geographiclib.sourceforge.net/geodesic-papers/biblio.htm
Sulphur abundances in halo stars from Multiplet 3 at 1045 nm

Sulphur is a volatile alpha-element which is not locked into dust grains in
the interstellar medium (ISM). Hence, its abundance does not need to be
corrected for dust depletion when comparing the ISM to the stellar atmospheres.
The abundance of sulphur in the photosphere of metal-poor stars is a matter of
debate: according to some authors, [S/Fe] versus [Fe/H] forms a plateau at low
metallicity, while, according to other studies, there is a large scatter or
perhaps a bimodal distribution. In metal-poor stars sulphur is detectable by
its lines of Mult.1 at 920 nm, but this range is heavily contaminated by
telluric absorptions, and one line of the multiplet is blended by the hydrogen
Paschen zeta line. We study the possibility of using Mult. 3 (at 1045 nm) for
deriving the sulphur abundance because this range, now observable at the VLT
with the infra-red spectrograph CRIRES, is little contaminated by telluric
absorption and not affected by blends at least in metal-poor stars. We compare
the abundances derived from Multiplets 1 and 3, taking into account NLTE
corrections and 3D effects. Here we present the results for a sample of four
stars, although the scatter is less pronounced than in previous analysis, we
cannot find a plateau in [S/Fe], and confirm the scatter of the sulphur
abundance at low metallicity.Comment: to be published in Astronomische Nachrichte
A Self-Consistent Treatment of the Electromotive Force in
  Magnetohydrodynamics for Large Diffusivities

The coupled equations that describe the effect of large-scale magnetic and
velocity fields on forced high-diffusivity magnetohydrodynamic flows are
investigated through an extension of mean field electrodynamics. Our results
generalise those of R\"adler & Brandenburg (2010), who consider a similar
situation but assume that the effect of the Lorentz force on the momentum
equation can be neglected. New mean coupling terms are shown to appear, which
can lead to large-scale growth of magnetic and velocity fields even when the
usual $\alpha$-effects are absent.Comment: Submitted to Astron. Nach
Stellar Archaeology -- Exploring the Universe with Metal-Poor Stars

The abundance patterns of the most metal-poor stars in the Galactic halo and
small dwarf galaxies provide us with a wealth of information about the early
Universe. In particular, these old survivors allow us to study the nature of
the first stars and supernovae, the relevant nucleosynthesis processes
responsible for the formation and evolution of the elements, early star- and
galaxy formation processes, as well as the assembly process of the stellar halo
from dwarf galaxies a long time ago. This review presents the current state of
the field of "stellar archaeology" -- the diverse use of metal-poor stars to
explore the high-redshift Universe and its constituents. In particular, the
conditions for early star formation are discussed, how these ultimately led to
a chemical evolution, and what the role of the most iron-poor stars is for
learning about Population III supernovae yields. Rapid neutron-capture
signatures found in metal-poor stars can be used to obtain stellar ages, but
also to constrain this complex nucleosynthesis process with observational
measurements. Moreover, chemical abundances of extremely metal-poor stars in
different types of dwarf galaxies can be used to infer details on the formation
scenario of the halo. and the role of dwarf galaxies as Galactic building
blocks. I conclude with an outlook as to where this field may be heading within
the next decade. A table of ~1000 metal-poor stars and their abundances as
collected from the literature is provided in electronic format.Comment: Ludwig Biermann Award Lecture 2009; data table can be found at
  http://www.cfa.harvard.edu/~afrebel/abundances/abund.html; published in AN
  331, 47
High-Fidelity Spectroscopy at the Highest Resolutions

High-fidelity spectroscopy presents challenges for both observations and in
designing instruments. High-resolution and high-accuracy spectra are required
for verifying hydrodynamic stellar atmospheres and for resolving intergalactic
absorption-line structures in quasars. Even with great photon fluxes from large
telescopes with matching spectrometers, precise measurements of line profiles
and wavelength positions encounter various physical, observational, and
instrumental limits. The analysis may be limited by astrophysical and telluric
blends, lack of suitable lines, imprecise laboratory wavelengths, or
instrumental imperfections. To some extent, such limits can be pushed by
forming averages over many similar spectral lines, thus averaging away small
random blends and wavelength errors. In situations where theoretical
predictions of lineshapes and shifts can be accurately made (e.g., hydrodynamic
models of solar-type stars), the consistency between noisy observations and
theoretical predictions may be verified; however this is not feasible for,
e.g., the complex of intergalactic metal lines in spectra of distant quasars,
where the primary data must come from observations. To more fully resolve
lineshapes and interpret wavelength shifts in stars and quasars alike, spectral
resolutions on order R=300,000 or more are required; a level that is becoming
(but is not yet) available. A grand challenge remains to design efficient
spectrometers with resolutions approaching R=1,000,000 for the forthcoming
generation of extremely large telescopes.Comment: 6 pages, 4 figures, to appear in Reviews in Modern Astronomy vol. 22
  (2010
Metallicity and kinematical clues to the formation of the Local Group

The kinematics and elemental abundances of resolved stars in the nearby
Universe can be used to infer conditions at high redshift, trace how galaxies
evolve and constrain the nature of dark matter. This approach is complementary
to direct study of systems at high redshift, but I will show that analysis of
individual stars allows one to break degeneracies, such as between star
formation rate and stellar Initial Mass Function, that complicate the analysis
of unresolved, distant galaxies.Comment: 10 pages, 5 figures. Invited review at the Astronomische Gesellschaft
  Annual Fall Meeting, `Deciphering the Universe through Spectroscopy',
  Potsdam, 21-25 September 200
Pulsations and planets: the asteroseismology-extrasolar-planet
  connection

The disciplines of asteroseismology and extrasolar planet science overlap
methodically in the branch of high-precision photometric time series
observations. Light curves are, amongst others, useful to measure intrinsic
stellar variability due to oscillations, as well as to discover and
characterize those extrasolar planets that transit in front of their host
stars, periodically causing shallow dips in the observed brightness. Both
fields ultimately derive fundamental parameters of stellar and planetary
objects, allowing to study for example the physics of various classes of
pulsating stars, or the variety of planetary systems, in the overall context of
stellar and planetary system formation and evolution. Both methods typically
also require extensive spectroscopic follow-up to fully explore the dynamic
characteristics of the processes under investigation. In particularly
interesting cases, a combination of observed pulsations and signatures of a
planet allows to characterize a system's components to a very high degree of
completeness by combining complementary information. The planning of the
relevant space missions has consequently converged with respect to science
cases, where at the outset there was primarily a coincidence in instrumentation
and techniques. Whether space- or ground-based, a specific type of stellar
pulsations can themselves be used in an innovative way to search for extrasolar
planets. Results from this additional method at the interface of stellar
pulsation studies and exoplanet hunts in a beyond-mainstream area are
presented.Comment: Ludwig Biermann Award Lecture 2009, Annual Fall Meeting of the
  Astronomische Gesellschaft (AG), Potsdam, 21-25 September 2009. 13 pages, 4
  figures, 1 tabl
Open clusters and the galactic disk

It is textbook knowledge that open clusters are conspicuous members of the
thin disk of our Galaxy, but their role as contributors to the stellar
population of the disk was regarded as minor. Starting from a homogenous
stellar sky survey, the ASCC-2.5, we revisited the population of open clusters
in the solar neighbourhood from scratch. In the course of this enterprise we
detected 130 formerly unknown open clusters, constructed volume- and
magnitude-limited samples of clusters, re-determined distances, motions, sizes,
ages, luminosities and masses of 650 open clusters. We derived the present-day
luminosity and mass functions of open clusters (not the stellar mass function
in open clusters), the cluster initial mass function CIMF and the formation
rate of open clusters. We find that open clusters contributed around 40 percent
to the stellar content of the disk during the history of our Galaxy. Hence,
open clusters are important building blocks of the Galactic disk.Comment: 7 pages, 7 figure
On the Nature of the Purported Common Proper Motion Companions to the
  Exoplanet Host Star 51 Peg

Greaves (2006) proposed that three red, high proper motion stars within 10
degrees of 51 Peg (NLTT 54007, 54064, & 55547) are co-moving companions to this
famous exoplanet host star. While the stars clearly have proper motions similar
to 51 Peg, the inferred kinematic parallaxes for these stars produce extremely
inconsistent color-magnitude positions 2 to 4 magnitudes below the main
sequence. All three stars are likely to be background stars unrelated to 51
Peg.Comment: 5 pages, 1 figure, AN, in pres
The role of emerging bipoles in the formation of a sunspot penumbra

The generation of magnetic flux in the solar interior and its transport from
the convection zone into the photosphere, the chromosphere, and the corona will
be in the focus of solar physics research for the next decades. With 4m class
telescopes, one plans to measure essential processes of radiative
magneto-hydrodynamics that are needed to understand the nature of solar
magnetic fields. One key-ingredient to understand the behavior of solar
magnetic field is the process of flux emergence into the solar photosphere, and
how the magnetic flux reorganizes to form the magnetic phenomena of active
regions like sunspots and pores. Here, we present a spectropolarimetric and
imaging data set from a region of emerging magnetic flux, in which a proto-spot
without penumbra forms a penumbra. During the formation of the penumbra the
area and the magnetic flux of the spot increases. First results of our data
analysis demonstrate that the additional magnetic flux, which contributes to
the increasing area of the penumbra, is supplied by the region of emerging
magnetic flux. We observe emerging bipoles that are aligned such that the spot
polarity is closer to the spot. As an emerging bipole separates, the pole of
the spot polarity migrates towards the spot, and finally merges with it. We
speculate that this is a fundamental process, which makes the sunspot
accumulate magnetic flux. As more and more flux is accumulated a penumbra forms
and transforms the proto-spot into a fully-fledged sunspot.Comment: 4 pages, 2 figures, submitted to Astronomische Nachrichte
Center to limb variation of penumbral Stokes V profiles

We investigated the horizontal and the vertical component of the Evershed
flow (EF). To this end, we computed average Stokes V profiles for various
velocity classes in penumbrae at different heliocentric angles. Our results
show that for blueshifted profiles an additional lobe with the same polarity as
the spot is present in the blue side of the average Stokes V profile. The
amplitude of the additional lobe grows with increasing blueshift and with
increasing heliocentric angle. For small redshifts, the profiles show an
additional lobe with the opposite polarity as the spot on the red side of the
average Stokes V profile. Even at disk center, the original polarity of the
average Stokes V profile is reversed for strong redshifts. The transition
between the different types of Stokes V profiles is continuous and indicates
that not only the vertical, but also the horizontal EF is a magnetized stream
of plasma in a magnetic background field
Spectro-Polarimetry in the Era of Large Solar Telescope

This paper discusses some of the challenges of spectro-polarimetric
observations with a large aperture solar telescope such as the ATST or the EST.
The observer needs to reach a compromise among spatial and spectral resolution,
time cadence, and signal-to-noise ratio, as only three of those four parameters
can be pushed to the limit. Tunable filters and grating spectrographs provide a
natural compromise as the former are more suitable for high-spatial resolution
observations while the latter are a better choice when one needs to work with
many wavelengths at full spectral resolution. Given the requirements for the
new science targeted by these facilities, it is important that 1)tunable
filters have some multi-wavelength capability; and 2)grating spectrographs have
some 2D field of view
IR spectroscopy of COmosphere dynamics with the CO first overtone band

We discuss observations of the weak first overtone CO absorption band near
2300 nm with the U.S. National Solar Observatory Array Camera (NAC), a modern
mid-infrared detector. This molecular band provides a thermal diagnostic that
forms lower in the atmosphere than the stronger fundamental band near 4600 nm.
The observed center-to-limb increase in CO line width qualitatively agrees with
the proposed higher temperature shocks or faster plasma motions higher in the
COmosphere. The spatial extent of chromospheric shock waves is currently at or
below the diffraction limit of the available C0 lines at existing telescopes.
Five minute period oscillations in line strength and measured Doppler shifts
are consistent with the p-mode excitation of the photospheric gas. We also show
recent efforts at direct imaging at 4600 nm. We stress that future
large-aperture solar telescopes must be teamed with improved, dynamic
mid-infrared instruments, like the NAC, to capitalize on the features that
motivate such facilities.Comment: 4 pages, 3 figures, Published in Astronomische Nachrichten on behalf
  of the 1st EAST-ATST Workshop: "Science with Large Solar Telescopes