pinecone/core-2020-05-10-deduplication huggingface dataset:
New Concept for Testing General Relativity: The Laser Astrometric Test
  of Relativity (LATOR) Mission

This paper discusses new Fundamental physics experiment that will test
relativistic gravity at the accuracy better than the effects of the second
order in the gravitational field strength, ~G^2. The Laser Astrometric Test Of
Relativity (LATOR) mission uses laser interferometry between two
micro-spacecraft whose lines of sight pass close by the Sun to accurately
measure deflection of light in the solar gravity. The key element of the
experimental design is a redundant geometry optical truss provided by a
long-baseline (100 m) multi-channel stellar optical interferometer placed on
the International Space Station (ISS). The spatial interferometer is used for
measuring the angles between the two spacecraft and for orbit determination
purposes. LATOR will not only improve the value of the parameterized
post-Newtonian (PPN) $\gamma$ to unprecedented levels of accuracy of 1 part in
10e8, it will also reach ability to measure effects of the next post-Newtonian
order (1/c^4) of light deflection resulting from gravity's intrinsic
non-linearity. The solar quadrupole moment parameter, J2, will be measured with
high precision, as well as a variety of other relativistic effects including
Lense-Thirring precession. LATOR will lead to very robust advances in the tests
of Fundamental physics: this mission could discover a violation or extension of
general relativity, or reveal the presence of an additional long range
interaction in the physical law. There are no analogs to the LATOR experiment;
it is unique and is a natural culmination of solar system gravity experiments.Comment: 11 pages, 4 figures, invited talk presented at AIAA Meeting "Space
  2003", 23 September 2003, Long Beach, C
Neutral hydrogen in radio galaxies: results from nearby, importance for
  far away

The study of neutral hydrogen emission and absorption in radio galaxies is
giving new and important insights on a variety of phenomena observed in these
objects. Such observations are helping to understand the origin of the host
galaxy, the effects of the interaction between the radio jet and the ISM, the
presence of fast gaseous outflows as well as jet-induced star formation. Recent
results obtained on these phenomena are summarized in this review. Although the
HI observations concentrate on nearby radio galaxies, the results also have
relevance for the high-z objects as all these phenomena are important, and
likely even more common, in high-redshift radio sources.Comment: Invited review to appear in the proceedings of the Granada workshop
  on High Redshift Radio Galaxies, Villar-Martin et al. eds. AN in press (7
  pages, 10 figures). The full paper with high resolution images can be
  downloaded from http://www.astron.nl/~morganti/Papers/Granada.pd
Concerning the instantaneous mass and the extent of an expanding universe

In this article we want to answer the cosmologically relevant question what, with some good semantic and physical reason, could be called the mass of an infinitely extended, homogeneously matter-filled and expanding universe. To answer this question we produce a space-like sum of instantaneous cosmic energy depositions surrounding equally each spacepoint in the homogeneous universe. We calculate the added-up instantaneous cosmic energy per volume around an arbitrary space point in the expanding universe. To carry out this sum we use as basic metrics an analogy to the inner Schwarzschild metric applied to stars, but this time applied to the spacepoint-related universe. It is then shown that this leads to the added-up proper energy within a sphere of a finite outer critical radius defining the point-related infinity. As a surprise this radius turns out to be reciprocal to the square root of the prevailing average cosmic energy density. The equivalent mass of the universe can then also be calculated and, by the expression which is obtained here, shows a scaling with this critical radius of this universe, a virtue of the universe which was already often called for in earlier works by E.Mach, H.Thirring and F.Hoyle and others. This radius on the other hand can be shown to be nearly equal to the Schwarzschild radius of the so-defined mass of the universe
Applicability of colour index calibrations to T Tauri stars

We examine the applicability of effective temperature scales of several broad
band colours to T Tauri stars (TTS). We take into account different colour
systems as well as stellar parameters like metallicity and surface gravity
which influence the conversion from colour indices or spectral type to
effective temperature. For a large sample of TTS, we derive temperatures from
broad band colour indices and check if they are consistent in a statistical
sense with temperatures inferred from spectral types. There are some scales
(for V-H, V-K, I-J, J-H, and J-K) which indeed predict the same temperatures as
the spectral types and therefore can be at least used to confirm effective
temperatures. Furthermore, we examine whether TTS with dynamically derived
masses can be used for a test of evolutionary models and effective temperature
calibrations. We compare the observed parameters of the eclipsing T Tauri
binary V1642 Ori A to the predictions of evolutionary models in both the H-R
and the Kiel diagram using temperatures derived with several colour index
scales. We check whether the evolutionary models and the colour index scales
are consistent with coevality and the dynamical masses of the binary
components. It turns out that the Kiel diagram offers a stricter test than the
H-R diagram. Only the evolutionary models of Baraffe et al. (1998) with mixing
length parameter 1.9 and of D'Antona & Mazzitelli (1994, 1997) show consistent
results in the Kiel diagram in combination with some conversion scales of
Houdashelt et al. (2000) and of Kenyon & Hartmann (1995).Comment: 13 pages, 4 tables, 6 figures, accepted for publication in A
A Planetary System with an Escaping Mars

The chaotic behaviour of the motion of the planets in our Solar System is
well established. In this work to model a hypothetical extrasolar planetary
system our Solar System was modified in such a way that we replaced the Earth
by a more massive planet and let the other planets and all the orbital elements
unchanged. The major result of former numerical experiments with a modified
Solar System was the appearance of a chaotic window at $\kappa_E \in (4,6)$,
where the dynamical state of the system was highly chaotic and even the body
with the smallest mass escaped in some cases. On the contrary for very large
values of the mass of the Earth, even greater than that of Jupiter regular
dynamical behaviour was observed. In this paper the investigations are extended
to the complete Solar System and showed, that this chaotic window does still
exist. Tests in different 'Solar Systems' clarified that including only Jupiter
and Saturn with their actual masses together with a more 'massive' Earth ($4 <
\kappa_E < 6$) perturbs the orbit of Mars so that it can even be ejected from
the system. Using the results of the Laplace-Lagrange secular theory we found
secular resonances acting between the motions of the nodes of Mars, Jupiter and
Saturn. These secular resonances give rise to strong chaos, which is the cause
of the appearance of the instability window.Comment: 6 pages, 8 figures, submitted to Astronomische Nachrichte
About universes with scale-related total masses and their abolition of presently outstanding cosmological problems

Cosmological consequences of a strictly valid total energy conservation for the whole universe are investigated in this paper. Interestingly enough as one consequence of ergodically behaving universes very specific scaling laws with the diameter R of the universe can be derived for relevant cosmic quantities. Especially the 1/R^2- scaling of mass - and vacuum energy - density then automatically leads to a vanishing cosmic curvature parameter k=0 and also reveals, that for such universes no horizon problem occurs. In addition the longstanding problem of observationally indicated very low cosmic vacuum energies in contrast to the very large quantumfield estimates is easily solved when the vacuum energy density decay with 1/R^2 is taken into account reconciling presently observed vacuum energy density values with those from theoretical expectations. We also suggest why the mass of the universe can permanently increase and can in fact grow up from a Planck mass as a pure vacuum fluctuation
Outstanding problems in local helioseismology

Time-distance helioseismology and related techniques show great promise for
probing the structure and dynamics of the subphotospheric layers of the Sun.
Indeed time-distance helioseismology has already been applied to make
inferences about structures and flows under sunspots and active regions, to map
long-lived convective flow patterns, and so on. Yet certainly there are still
many inadequacies in the current approaches and, as the data get better and the
questions we seek to address get more subtle, methods that were previously
regarded as adequate are no longer acceptable. Here we give a short and partial
description of outstanding problems in local helioseismology, using
time-distance helioseismology as a guiding example.Comment: 7 pages, 0 figure
Linear Sensitivity of Helioseismic Travel Times to Local Flows

Time-distance helioseismology is a technique for measuring the time for waves
to travel from one point on the solar surface to another. These wave travel
times are affected by advection by subsurface flows. Inferences of plasma flows
based on observed travel times depend critically on the ability to accurately
model the effects of subsurface flows on time-distance measurements. We present
a Born approximation based computation of the sensitivity of time distance
travel times to weak, steady, inhomogeneous subsurface flows. Three sensitivity
functions are obtained, one for each component of the 3D vector flow. We show
that the depth sensitivity of travel times to horizontally uniform flows is
given approximately by the kinetic energy density of the oscillation modes
which contribute to the travel times. For flows with strong depth dependence,
the Born approximation can give substantially different results than the ray
approximation.Comment: 6 pages, 6 figure
Surface magnetic field effects in local helioseismology

Using helioseismic holography strong evidence is presented that the phase (or
equivalent travel-time) of helioseismic signatures in Dopplergrams within
sunspots depend upon the line-of-sight angle in the plane containing the
magnetic field and vertical directions. This is shown for the velocity signal
in the penumbrae of two sunspots at 3, 4 and 5 mHz. Phase-sensitive holography
demonstrates that they are significantly affected in a strong, moderately
inclined magnetic field. This research indicates that the effects of the
surface magnetic field are potentially very significant for local helioseismic
analysis of active regions.Comment: 6 pages, 8 figure
SLiM: a code for the simulation of wave propagation through an
  inhomogeneous, magnetised solar atmosphere

In this paper we describe the semi-spectral linear MHD (SLiM) code which we
have written to follow the interaction of linear waves through an inhomogeneous
three-dimensional solar atmosphere. The background model allows almost
arbitrary perturbations of density, temperature, sound speed as well as
magnetic and velocity fields. We give details of several of the tests we have
used to check the code. The code will be useful in understanding the
helioseismic signatures of various solar features, including sunspots.Comment: 6 pages, 7 figure
A New Numerical Method for Solving Radiation Driven Winds from Hot Stars

We present a general method for solving the non--linear differential equation of monotonically increasing steady--state radiation driven winds. We graphically identify all the singular points before transforming the momentum equation to a system of differential equations with all the gradients explicitly give. This permits a topological classification of all singular points and to calculate the maximum and minimum mass--loss of the wind. We use our method to analyse for the first time the topology of the non--rotating frozen in ionisation m--CAK wind, with the inclusion of the finite disk correction factor and find up to 4 singular points, three of the x--type and one attractor--type. The only singular point (and solution passing through) that satisfies the boundary condition at the stellar surface is the standard m--CAK singular point
Old Metal-rich Globular Cluster Populations: Peak Color and Peak
  Metallicity Trends with Mass of Host Spheroids

We address the problem of the factors contributing to a peak color trend of
old metal-rich globular cluster (MRGC) populations with mass of their hosts,
early-type galaxies and spheroidal subsystems of spiral ones (spheroids). The
color-mass trend is often converted to a metallicity-mass trend under the
assumption that age effects are small or negligible. While direct estimates of
the ages of MRGC populations neither can rule out nor reliably support the
populations' age trend, key data on timing of the formation of spheroids and
other indirect evidence imply it in the sense: the more massive spheroid the
older on average its MRGC population. We show that the contribution of an
allowable age trend of the MRGC populations to their peak color trend can
achieve up to ~50 % or so. In this event the comparable value of the color
trend, ~30 %, is due to alpha-element ratio systematic variations of the order
of Delta[alpha/Fe] ~ 0.1 to 0.2 dex because of a correlation between the
[alpha/Fe] ratios and age. Hence a systematic variation of exactly [Fe/H]
ratios may turn out to be less significant among the contributors, and its
range many times lower, i.e. of the order of Delta[Fe/H] ~ 0.1 or even none,
than the corresponding range deduced by assuming no age trend.Comment: 5 pages, 1 figure, accepted for publication in Astronomische
  Nachrichte
Low mass visual binaries in the solar neighbourhood: The case of
  HD141272

We search for stellar and substellar companions of young nearby stars to
investigate stellar multiplicity and formation of stellar and substellar
companions. We detect common proper-motion companions of stars via multi-epoch
imaging. Their companionship is finally confirmed with photometry and
spectroscopy. Here we report the discovery of a new co-moving (13 sigma)
stellar companion ~17.8 arcsec (350 AU in projected separation) north of the
nearby star HD141272 (21 pc). With EMMI/NTT optical spectroscopy we determined
the spectral type of the companion to be M3+-0.5V. The derived spectral type as
well as the near infrared photometry of the companion are both fully consistent
with a 0.26+-0.07 Msol dwarf located at the distance of HD141272 (21 pc).
Furthermore the photometry data rules out the pre-main sequence status, since
the system is consistent with the ZAMS of the Pleiades.Comment: 6 pages, 6 figure
EM Cygni: a study of its eclipse timings

EM Cygni is a Z Cam-subtype eclipsing dwarf nova. Its orbital period
variations were reported in the past but the results were in conflict to each
other while other studies allowed the possibility of no period variation. In
this study we report accurate new times of minima of this eclipsing binary and
update its O-C diagram. We also estimate the mass transfer rate in EM Cygni
system and conclude that the mass transfer is far from the critical value. The
mass transfer rate determined from the eclipse timings is in agreement with the
spectroscopically determined value.Comment: 5 pages, 4 figures, accepted for publication in Astronomische
  Nahrichte
Simulations of the anisotropic kinetic and magnetic alpha effects

The validity of a closure called the minimal tau approximation (MTA), is
tested in the context of dynamo theory, wherein triple correlations are assumed
to provide relaxation of the turbulent electromotive force. Under MTA, the
alpha effect in mean field dynamo theory becomes proportional to a relaxation
time scale multiplied by the difference between kinetic and current helicities.
It is shown that the value of the relaxation time is positive and, in units of
the turnover time at the forcing wavenumber, it is of the order of unity. It is
quenched by the magnetic field -- roughly independently of the magnetic
Reynolds number. However, this independence becomes uncertain at large magnetic
Reynolds number. Kinetic and current helicities are shown to be dominated by
large scale properties of the flow.Comment: 6 pages, 6 figures, accepted by Astron. Nach
Evolution of Magnetic Fields in Stars Across the Upper Main Sequence:
  II. Observed distribution of the magnetic field geometry

We re-discuss the evolutionary state of upper main sequence magnetic stars
using a sample of Ap and Bp stars with accurate Hipparcos parallaxes and
definitely determined longitudinal magnetic fields. We confirm our previous
results obtained from the study of Ap and Bp stars with accurate measurements
of the mean magnetic field modulus and mean quadratic magnetic fields that
magnetic stars of mass M < 3 M_sun are concentrated towards the centre of the
main-sequence band. In contrast, stars with masses M > 3 M_sun seem to be
concentrated closer to the ZAMS. The study of a few known members of nearby
open clusters with accurate Hipparcos parallaxes confirms these conclusions.
Stronger magnetic fields tend to be found in hotter, younger and more massive
stars, as well as in stars with shorter rotation periods. No evidence is found
for any loss of angular momentum during the main-sequence life. The magnetic
flux remains constant over the stellar life time on the main sequence. An
excess of stars with large obliquities beta is detected in both higher and
lower mass stars. The obliquity angle distribution as inferred from the
distribution of r-values appears random at the time magnetic stars become
observable on the H-R diagram. After quite a short time spent on the main
sequence, the obliquity angle beta tends to reach values close to either 90 deg
or 0 deg for M < 3 M_sun. The evolution of the obliquity angle beta seems to be
somewhat different for low and high mass stars. While we find a strong hint for
an increase of beta with the elapsed time on the main sequence for stars with M
> 3 M_sun, no similar trend is found for stars with M < 3 M_sun. However, the
predominance of high values of beta at advanced ages in these stars is notable.Comment: 16 pages, 22 figures, 5 tables, accepted for publication in A
Photospheric and chromospheric activity on EY Dra

Magnetic activity in the photosphere and chromosphere of the M dwarf EY Dra
is studied and possible correlations between the two are investigated using
photometric observations in the V and R bands and optical and near infrared
spectroscopy. The longitudinal spot configuration in the photosphere is
obtained from the V band photometry, and the chromospheric structures are
investigated using variations in the H alpha line profile and observations of
the Paschen beta line. The shape of the V band light-curve indicates two active
regions on the stellar surface, about 0.4 in phase apart. The spectroscopic
observations show enhanced H alpha emission observed close to the phases of the
photometrically detected starspots. This could indicate chromospheric plages
associated with the photospheric starspots. Some indications of prominence
structures are also seen. The chromospheric pressure is limited to logTR < -4
based on the non-detection of emission in the Paschen beta wavelength region.Comment: 7 pages, 7 figures, accepted for publication in Astronomische
  Nachrichten (Astronomical Notes
Effective temperature vs line-depth ratio for ELODIE spectra. Gravity
  and rotational velocity effects

The dependence on the temperature of photospheric line-depth ratios (LDRs) in
the spectral range 6190-6280 A is investigated by using a sample of 174 ELODIE
Archive stellar spectra of luminosity class from V to III. The rotational
broadening effect on LDRs is also studied. We provide useful calibrations of
effective temperature versus LDRs for giant and main sequence stars with
3800<Teff<6000 K and vsini in the range 0-30 km/s. We found that, with the
exception of very few line pairs, LDRs, measured at a spectral resolution as
high as 42000, depend on vsini and that, by neglecting the rotational
broadening effect, one can mistake the Teff determination of 100 K in the worst
cases.Comment: 10 pages, 12 figures, Accepted by A
Comparison of dust-to-gas ratios in luminous, ultraluminous, and
  hyperluminous infrared galaxies

The dust-to-gas ratios in three different samples of luminous, ultraluminous,
and hyperluminous infrared galaxies are calculated by modelling their radio to
soft X-ray spectral energy distributions using composite models which account
for the photoionizing radiation from HII regions, starbursts, or AGNs, and for
shocks. The models are limited to a set which broadly reproduces the mid-IR
fine structure line ratios of local, IR bright, starburst galaxies. The results
show that two types of clouds contribute to the IR emission. Those
characterized by low shock velocities and low preshock densities explain the
far-IR dust emission, while those with higher velocities and densities
contribute to mid-IR dust emission. An AGN is found in nearly all of the
ultraluminous IR galaxies and in half of the luminous IR galaxies of the
sample. High IR luminosities depend on dust-to-gas ratios of about 0.1 by mass,
however, most hyperluminous IR galaxies show dust-to-gas ratios much lower than
those calculated for the luminous and ultraluminous IR galaxies.Comment: 19 pages+ 7 figures. in press in A
Absolute and convective instabilities in an inviscid compressible mixing
  layer

We consider the stability of a compressible shear flow separating two streams
of different speeds and temperatures. The velocity and temperature profiles in
this mixing layer are hyperbolic tangents.
  The normal mode analysis of the flow stability reduces to an eigenvalue
problem for the pressure perturbation. We briefly describe the numerical method
that we used to solve this problem. Then, we introduce the notions of the
absolute and convective instabilities and examine the effects of Mach number,
and the velocity and temperature ratios of each stream on the transition
between convective and absolute instabilities. Finally, we discuss the
implication of the results presented in this paper for the heliopause
stability.Comment: 5 pages, 6 figures, accepted by Astronomical Notes (Astron.
  Nachrichten
Photometric monitoring of the blazar 3C 345 for the period 1996 - 2006

We present the results of the blazar 3C 345 monitoring in Johnson-Cousins
BVRI bands for the period 1996 - 2006. We have collected 29 V and 43 R data
points for this period; the BI light curves contain a few measurements only.
The accuracy of our photometry is not better than 0.03 mag in the VR bands. The
total amplitude of the variability obtained from our data is 2.06 mag in the V
band and 2.25 mag in the R one. 3C 345 showed periods of flaring activity
during 1998/99 and 2001: a maximum of the blazar brightness was detected in
2001 February - 15.345 mag in the V band and 14.944 mag in the R one. We
confirm that during brighter stages 3C 345 becomes redder; for higher fluxes
the colour index seems to be less dependent on the magnitude. The intra-night
monitoring of 3C 345 in three consecutive nights in 2001 August revealed no
significant intra-night variability; 3C 345 did not show evident flux changes
over timescales of weeks around the period of the intra-night monitoring. This
result supports the existing facts that intra-night variability is correlated
with rapid flux changes rather than with specific flux levels