pinecone/core-2020-05-10-deduplication huggingface dataset:
Integer-ambiguity resolution in astronomy and geodesy

Recent theoretical developments in astronomical aperture synthesis have
revealed the existence of integer-ambiguity problems. Those problems, which
appear in the self-calibration procedures of radio imaging, have been shown to
be similar to the nearest-lattice point (NLP) problems encountered in
high-precision geodetic positioning, and in global navigation satellite
systems. In this paper, we analyse the theoretical aspects of the matter and
propose new methods for solving those NLP problems. The related optimization
aspects concern both the preconditioning stage, and the discrete-search stage
in which the integer ambiguities are finally fixed. Our algorithms, which are
described in an explicit manner, can easily be implemented. They lead to
substantial gains in the processing time of both stages. Their efficiency was
shown via intensive numerical tests.Comment: 12 pages. Soumis et accept\'e pour publication dans "Astronomische
  Nachrichten
Probing the temporal and spatial variations of dust emission in the
  protoplanetary disk of DG Tau with VLTI/MIDI - Preliminary results

The signatures of dust processing and grain growth - related to the formation
of rocky planets - are easily seen in mid-infrared spectral features. One
important diagnostic tool in this context is the silicate feature in the
spectra of young stellar objects (YSO). The low-mass YSO, DG Tau shows unique
temporal variations in its silicate feature. We conducted multi-epoch
observations of DG Tau with the MID-Infrared Interferometric instrument of the
Very Large Telescope Interferometer to obtain the spectra of the inner and
outer disk regions in order to investigate where the previously reported
variations of the silicate feature originate from. Here we present the
preliminary results of the first two epochs of observations. We found that on a
time-scale of two months, the source showed significant brightening. At the
same time the mid-infrared emitting region expanded. While the identification
of the silicate feature is difficult, our results qualitatively agree with the
scenario explaining the varying silicate feature with dust lifted up above the
disk.Comment: 4 pages, 4 figures. Accepted for publication in Astronomische
  Nachrichte
Relativistic model for cold spherical interstellar gas clouds

We investigate insterstellar gas spheres by determining the metric functions,
the material distribution, and the features of particle orbits in terms of
stability and geodesics. An exact solution of the Einstein's equations for
interstellar gas clouds is derived that is compatible with the results of
recent astronomical measurements. The solution determines the distribution of
pressure and density, and it is suitable to describe the energy, speed,
trajectory, and further relevant physical features of the cloud's particles. We
describe the spacetime inside the nebula and give the density profile and the
geodesics of particles. We find that circular orbits are stable and the cloud
rotates rigidly by an angular velocity that is inversely proportional to the
radius
The Fly's Eye Camera System -- an instrument design for large \'etendue
  time-domain survey

In this paper we briefly summarize the design concepts of the Fly's Eye
Camera System, a proposed high resolution all-sky monitoring device which
intends to perform high cadence time domain astronomy in multiple optical
passbands while still accomplish a high \'etendue. Fundings have already been
accepted by the Hungarian Academy of Sciences in order to design and build a
Fly's Eye device unit. Beyond the technical details and the actual scientific
goals, this paper also discusses the possibilities and yields of a network
operation involving ~10 sites distributed geographically in a nearly
homogeneous manner. Currently, we expect to finalize the mount assembly -- that
performs the sidereal tracking during the exposures -- until the end of 2012
and to have a working prototype with a reduced number of individual cameras
sometimes in the spring or summer of 2013.Comment: Accepted for publication in AN, 4.05 pages. Website of the project:
  http://flyseye.net
A statistical dynamical study of meteorite impactors: a case study based
  on parameters derived from the Bosumtwi impact event

The study of meteorite craters on Earth provides information about the
dynamic evolution of bodies within the Solar System. Bosumtwi crater is a well
studied, 10.5 km in diameter, ca. 1.07 Ma old impact structure located in
Ghana. The impactor was $\sim$ 1 km in diameter, an ordinary chondrite and
struck the Earth with an angle between 30$^\circ$ and 45$^\circ$ from the
horizontal. We have used a two phase backward integration to constrain the most
probable parent region of the impactor. We find that the most likely source
region is a high inclination object from the Middle Main Belt.Comment: Accepted in Astronomical Note
Turbulent magnetic energy spectrum and the cancellation function of
  solar photospheric magnetic fields

A simple analytical relation of form {\alpha} = 2 {\kappa} -1 between the
magnetic energy spectral exponent {\alpha} of the turbulent magnetic field in
the solar photosphere and its magnetic flux cancellation exponent {\kappa},
valid under certain restrictive assumptions, is tested and extended outside its
range of validity in a series of Monte Carlo simulations. In these numerical
tests artificial "magnetograms" are constructed in 1D and 2D by superposing a
discrete set of Fourier modes of the magnetic field distribution with
amplitudes following a power law spectrum and measuring the cancellation
function on these simulated magnetograms. Our results confirm the validity of
the analytical relation and extend it to the domain {\alpha} < -1 where
{\kappa} ---> 0 as {\alpha} ---> - infinity. The observationally derived upper
limit of 0.38 on {\kappa} implies {\alpha} < -0.24 in the granular size range,
apparently at odds with a small scale dynamo driven in the inertial range.Comment: 4 pages, 4 figure
Oscillator Models of the Solar Cycle and the Waldmeier Effect

We study the behaviour of the van der Pol oscillator when either its damping
parameter $\mu$ or its nonlinearity parameter $\xi$ is subject to additive or
multiplicative random noise. Assuming various power law exponents for the
relation between the oscillating variable and the sunspot number, for each case
we map the parameter plane defined by the amplitude and the correlation time of
the perturbation and mark the parameter regime where the sunspot number
displays solar-like behaviour. Solar-like behaviour is defined here as a good
correlation between the rise rate and cycle amplitude {\it and} the lack of a
good correlation between the decay rate and amplitude, together with
significant ($\ga 10$\,%) r.m.s. variation in cycle lengths and cycle
amplitudes. It is found that perturbing $\mu$ alone the perturbed van der Pol
oscillator does not show solar-like behaviour. When the perturbed variable is
$\xi$, solar-like behaviour is displayed for perturbations with a correlation
time of about 3--4 years and significant amplitude. Such studies may provide
useful constraints on solar dynamo models and their parameters.Comment: 4 pages, 2 figure
A quest for activity cycles in low mass stars

Long-term photometric measurements in a sample of ultrashort-period (P~0.5
days or less) single and binary stars of different interior structures are
analysed. A loose correlation exists between the rotational rate and cycle
lengths of active stars, regardless of their evolutionary state and the
corresponding physical parameters. The shortest cycles are expected on the
fastest rotators in the order of 1-2 years, which is reported in this paper.Comment: 4 pages, 3 figures, 1 table, accepted for publication in A
Doppler imaging of the double-lined active binary V824 Ara

We introduce an iterative spectral disentangling technique combined with
Doppler imaging in order to recover surface temperature maps for both
components of double-lined active binary systems. Our method provides an
opportunity to separate spectra of the active components while minimizing the
unwanted disturbances on the given line profile from the other component. The
efficiency of the method is demonstrated on real data of the double-lined RS
CVn-type binary V824 Ara. The resulting Doppler images reveal cool spots on the
polar regions as well as low-latitude features on both of the stars. Moreover,
both components have hot spots, that are facing each other. This may indicate
interconnection between the stellar magnetic fields.Comment: 5 pages, 6 figure
Analysis of the possible Blazhko-effect Cepheid V473 Lyrae

V473 Lyrae is a peculiar Galactic Cepheid, showing strong amplitude
modulation that resembles the Blazhko-effect observed in RR Lyrae stars. We
collected data spanning several modulation cycles and started a detailed
analysis. The first results indicate that the star shows both amplitude and
phase modulations with an average period of 1204 days, but both the cycle
length and the strength of the modulation are subjected to considerable
variations. A possible quintuplet component in the Fourier spectrum and
additional period changes were also detected.Comment: 5 pages, 6 figures, accepted for publication in AN. Proceedings for
  the 6th Workshop of Young Researchers in Astronomy and Astrophysic
Hunting for binary Cepheids using lucky imaging technique

Detecting companions to Cepheids is difficult. In most cases the bright
pulsator overshines the fainter secondary. Since Cepheids play a key role in
determining the cosmic distance scale it is crucial to find binaries among the
calibrating stars of the period-luminosity relation. Here we present an ongoing
observing project of searching for faint and close companions of Galactic
Cepheids using lucky imaging technique.Comment: 4 pages, 2 figures, published in AN. Proceedings for the 6th Workshop
  of Young Researchers in Astronomy and Astrophysic
Stability of librational motion in the spatial circular restricted
  three-body problem for high inclinations and mass ratios

In the spatial circular restricted three-body problem librational motion
around the Lagrangian points $L_4$ and $L_5$ exists up to high inclinations of
the massless object. We report the results of numerical investigations on the
stability of this librational motion for systematic variations in the
inclination of the Trojan and the mass-ratio $\mu$ of the two massive bodies.
We show that stable motion prevails for inclinations below 60 degrees and
mass-ratios $\mu < 0.04$ for typical integration times up to $10^6$ revolution
periods. At even higher mass-ratios -- beyond the critical mass-ratio for the
planar case -- stable orbits were found to exist for up to $10^7$ periods at
moderate inclinations. We extracted the librational frequencies on a grid in
the parameter space from the Fourier spectra and traced their variation.
Several resonances between the short and long period librational frequency as
well as the vertical frequency lie inside the investigated region. The
application of the Lyapunov characteristic indicator and spectral number
methods also reveals the chaotic regions. This simple model is equally
applicable in the Solar system for low mass ratios for Trojans of the planets,
as well as to Trojan-type exoplanets in binary star systems at high
mass-ratios.Comment: 4 pages, 4 figures, contribution to the 6th Workshop of Young
  Researchers in Astronomy and Astrophysics, Budapest 201
Photo-Met: a non-parametric method for estimating stellar metallicity
  from photometric observations

Getting spectra at good signal-to-noise ratios takes orders of magnitudes
more time than photometric observations. Building on the technique developed
for photometric redshift estimation of galaxies, we develop and demonstrate a
non-parametric photometric method for estimating the chemical composition of
galactic stars. We investigate the efficiency of our method using
spectroscopically determined stellar metallicities from SDSS DR7. The technique
is generic in the sense that it is not restricted to certain stellar types or
stellar parameter ranges and makes it possible to obtain metallicities and
error estimates for a much larger sample than spectroscopic surveys would
allow. We find that our method performs well, especially for brighter stars and
higher metallicities and, in contrast to many other techniques, we are able to
reliably estimate the error of the predicted metallicities.Comment: 5 pages, 4 figures, accepted for publication in A
Refined position angle measurements for galaxies of the SDSS Stripe 82
  co-added dataset

Position angle measurements of Sloan Digital Sky Survey (SDSS) galaxies, as
measured by the surface brightness profile fitting code of the SDSS photometric
pipeline (Lupton 2001), are known to be strongly biased, especially in the case
of almost face-on and highly inclined galaxies. To address this issue we
developed a reliable algorithm which determines position angles by means of
isophote fitting. In this paper we present our algorithm and a catalogue of
position angles for 26397 SDSS galaxies taken from the deep co-added Stripe 82
(equatorial stripe) images.Comment: 4 pages, 4 figures. Data are published on-line at
  http://www.vo.elte.hu/galmorp
Phase statistics of the WMAP 7 year data

We performed a comprehensive statistical analysis using complex phases of the
a_lm coefficients computed from the most recent data of the Wilkinson Microwave
Anisotropy Probe (WMAP). Our aim was to confirm or constrain the presence of
non-Gaussianities in the data. We found phase correlations - that suggest
non-Gaussianity - at high-l in a_lm coefficients by applying various
statistical tests. Most of all, we detected a non-Gaussian signal reaching a
significance of 4.7 sigma using random walk statistics and simulations.
However, our conclusion is that the non-Gaussian behavior is due to
contamination from galactic foregrounds that show up in small scales only. When
masked out the contaminated regions, we found no significant non-Gaussianity.
Furthermore, we constrained the f_NL parameter using CMB simulations that mimic
primordial non-Gaussianity. Our estimate is f_NL=40 +/- 200, in agreement with
previous measurements and inflationary expectations.Comment: 4 pages, 4 figures, Accepted for Publication in A
Constraints on supermassive black hole spins from observations of active
  galaxy jets

We discuss the origin of the low-energy cutoff, or LEC, seen in the radio
spectra of many extragalactic jets and relate this to the spin of the
supermassive black holes that presumably power them. Pion decay via
proton-proton collisions is a possible mechanism to supply a secondary positron
population with a low energy limit. We expect that pion production would occur
in advection dominated accretion flows or ADAFs. In radiatively inefficient
ADAFs the heat energy of the accreting gas is unable to radiate in less than
the accretion time and the particle temperature could be high enough so that
thermal protons can yield such pion production. Strong starbursts are another
option for the injection of a truncated particle population into the jet. The
role of both mechanisms is discussed with respect to the black hole spin
estimate. The energy demanded to produce the pion decay process involves a
minimum threshold for kinetic energy of the interacting protons. Therefore the
mean proton speed in the flow can determine whether a LEC is generated. In
ADAFs the random velocity of the protons can exceed the minimum speed limit of
pion production around the jet launching region in the innermost part of the
flow. Finally we summarize the additional work needed to put the model
assumptions on a more rigorous basis
Investigation the connection between the intermediate gamma-ray bursts
  and X-ray flashes

Gamma-ray bursts can be divided into three groups: short-, intermediate and
long-duration bursts. While the progenitors of the short and long ones are
relatively known, the progenitor objects of the intermediate-duration bursts
are generally unknown, however, recent statistical studies suggest, that they
should be related to the long-duration bursts. In this work we investigate
whether there is a differ- ence between the global parameters of the X-ray
flashes and intermediate-duration group of gamma-ray bursts. The statistical
tests do not show any significant discrepancy regarding most of the parameters,
except the BAT photon index, which is only a consequence of the defintion of
the X-ray flashes.Comment: 9 pages, 10 figures, submitted to Astronomische Nachrichte
Weak and strong field approximations and circular orbits of
  Kehagias-Sfetsos space-time

The Kehagias-Sfetsos asymptotically flat black hole and naked singularity
solutions of Ho\v{r}ava-Lifshitz gravity are investigated both in the
weak-field and strong-field regimes. In the weak-field limit the gravitational
field generated by the Kehagias-Sfetsos spherically symmetric solution is
weaker then in the case of the Schwarzschild black hole of general relativity.
In the strong-field regime naked singularities with $\omega_{0} \ll 1 $ display
an unusual distance dependence: gravity becomes weaker when approaching the
singularity. The stability of circular orbits is also analyzed. While in the
black hole case the square of the angular momentum should be larger than a
certain finite, non-zero minimal value, in the naked singularity case there are
stable circular orbits for any non-zero value of the angular momentum. In this
regime we prove the existence of an infimum of the allowed radii of circular
orbits (corresponding to vanishing angular momentum)
Black hole tidal charge constrained by strong gravitational lensing

Spherically symmetric brane black holes have tidal charge, which modifies
both weak and strong lensing characteristics. Even if lensing measurements are
in agreement with a Schwarzschild lens, the margin of error of the detecting
instrument allows for a certain tidal charge. In this paper we derive the
respective constraint on the tidal charge of the supermassive black hole (SMBH)
in the center of our galaxy, from the radius of the first relativistic Einstein
ring, emerging in strong lensing. We find that even if general relativistic
predictions are confirmed by high precision strong lensing measurements, SMBHs
could have a much larger tidal charge, than the Sun or neutron stars
Modified methods of stellar magnetic field measurements

The standard methods of the magnetic field measurement, based on an analysis
of the relation between the Stokes $V$-parameter and the first derivative of
the total line profile intensity, were modified by applying a linear integral
operator $\hat{L}$ to the both sides of this relation. As the operator
$\hat{L}$, the operator of the wavelet transform with DOG-wavelets is used. The
key advantage of the proposed method is an effective suppression of the noise
contribution to the line profile and the Stokes parameter $V$. The efficiency
of the method has been studied using the model line profiles with various noise
contributions. To test the proposed method, the spectropolarimetric
observations of the A0-type star $\alpha^2\,$ CVn, young O-type star $\theta^1$
Ori C and A0 supergiant HD 92207 were used. The longitudinal magnetic field
strengths for these stars calculated by our method appeared to be in a good
agreement with those determined by other methods.Comment: 11 pages, 6 figure
The stellar content of the young open cluster Trumpler 37

With an apparent cluster diameter of 1.5{\deg} and an age of ~4 Myr, Trumpler
37 is an ideal target for photometric monitoring of young stars as well as for
the search of planetary transits, eclipsing binaries and other sources of
variability. The YETI consortium has monitored Trumpler 37 throughout 2010 and
2011 to obtain a comprehensive view of variable phenomena in this region. In
this first paper we present the cluster properties and membership determination
as derived from an extensive investigation of the literature. We also compared
the coordinate list to some YETI images. For 1872 stars we found literature
data. Among them 774 have high probability of being member and 125 a medium
probability. Based on infrared data we re-calculate a cluster extinction of
0.9-1.2 mag. We can confirm the age and distance to be 3-5 Myr and ~870 pc.
Stellar masses are determined from theoretical models and the mass function is
fitted with a power-law index of alpha=1.90 (0.1-0.4 M_sun) and alpha=1.12
(1-10 M_sun).Comment: 9 pages, 10 figures, 2 long tables, accepte
Modelling Giant Radio Halos

We review models for giant radio halos in clusters of galaxies, with a focus
on numerical and theoretical work. After summarising the most important
observations of these objects, we present an introduction to the theoretical
aspects of hadronic models. We compare these models with observations using
simulations and find severe problems for hadronic models. We give a short
introduction to reacceleration models and show results from the first
simulation of CRe reaccel- eration in cluster mergers. We find that in-line
with previous theoretical work, reacceleration models are able to elegantly
explain main observables of giant radio halos
The M4 Core Project with HST --- I. Overview and First-Epoch

We present an overview of the ongoing Hubble Space Telescope large program
GO-12911. The program is focused on the core of M4, the nearest Galactic
globular cluster, and the observations are designed to constrain the number of
binaries with massive companions (black holes, neutron stars, or white dwarfs)
by measuring the ``wobble'' of the luminous (main-sequence) companion around
the center of mass of the pair, with an astrometric precision of ~50
micro-arcseconds. The high spatial resolution and stable medium-band PSFs of
WFC3/UVIS will make these measurements possible. In this work we describe: (i)
the motivation behind this study, (ii) our observing strategy, (iii) the many
other investigations enabled by this unique data set, and which of those our
team is conducting, and (iv) a preliminary reduction of the first-epoch
data-set collected on October 10, 2012.Comment: 25 pages, 14 figures (9 at low resolution), 3 tables. Published in:
  Astronomische Nachrichten, Volume 334, Issue 10, pages 1062-1085, December
  2013. http://onlinelibrary.wiley.com/doi/10.1002/asna.201311911/abstrac
An investigation into the radial velocity variability of GJ 581 - On the
  significance of GJ 581g

We investigate the radial velocity variation of GJ 581 based on measurements
from the HARPS and Keck HIRES spectrographs. A Fourier pre-whitening procedure
is able to extract four planetary signals in the HARPS data and two from the
Keck data. Combining both data sets increases the significance of the four
planet signals found by HARPS. This indicates that the Keck data also supports
the presence of four planets. A periodogram analysis of the residual radial
velocity measurements after removal of the four planetary signals shows several
periodic signals that are significant when assessing the false alarm
probability via a bootstrap. However, it is demonstrated that these are not due
to planetary companions. This analysis is able to confirm the presence of four
planets around GJ 581, but not the presence of GJ 581g.Comment: Accepted for publication in Astronomical Notes/Astronomische
  Nachtrichte