pinecone/core-2020-05-10-deduplication huggingface dataset:
Thermalizing a telescope in Antarctica: Analysis of ASTEP observations

The installation and operation of a telescope in Antarctica represent
particular challenges, in particular the requirement to operate at extremely
cold temperatures, to cope with rapid temperature fluctuations and to prevent
frosting. Heating of electronic subsystems is a necessity, but solutions must
be found to avoid the turbulence induced by temperature fluctua- tions on the
optical paths. ASTEP 400 is a 40 cm Newton telescope installed at the Concordia
station, Dome C since 2010 for photometric observations of fields of stars and
their exoplanets. While the telescope is designed to spread star light on
several pixels to maximize photometric stability, we show that it is
nonetheless sensitive to the extreme variations of the seeing at the ground
level (between about 0.1 and 5 arcsec) and to temperature fluctuations between
--30 degrees C and --80 degrees C. We analyze both day-time and night-time
observations and obtain the magnitude of the seeing caused by the mirrors, dome
and camera. The most important effect arises from the heating of the primary
mirror which gives rise to a mirror seeing of 0.23 arcsec K--1 . We propose
solutions to mitigate these effects.Comment: Appears in Astronomical Notes / Astronomische Nachrichten, Wiley-VCH
  Verlag, 2015, pp.1-2
The Gaia spectrophotometric standard stars survey -II. Instrumental
  effects of six ground-based observing campaigns

The Gaia SpectroPhotometric Standard Stars (SPSS) survey started in 2006, it
was awarded almost 450 observing nights, and accumulated almost 100,000 raw
data frames, with both photometric and spectroscopic observations. Such large
observational effort requires careful, homogeneous, and automated data
reduction and quality control procedures. In this paper, we quantitatively
evaluate instrumental effects that might have a significant (i.e.,$\geq$1%)
impact on the Gaia SPSS flux calibration. The measurements involve six
different instruments, monitored over the eight years of observations dedicated
to the Gaia flux standards campaigns: DOLORES@TNG in La Palma, EFOSC2@NTT and
ROSS@REM in La Silla, CAFOS@2.2m in Calar Alto, BFOSC@Cassini in Loiano, and
LaRuca@1.5m in San Pedro Martir. We examine and quantitatively evaluate the
following effects: CCD linearity and shutter times, calibration frames
stability, lamp flexures, second order contamination, light polarization, and
fringing. We present methods to correct for the relevant effects, which can be
applied to a wide range of observational projects at similar instruments.Comment: 16 pages, 13 figures, accepted for publication in Astron. Nach
The Age and Interior Rotation of Stars from Asteroseismology

We provide a status report on the determination of stellar ages from
asteroseismology for stars of various masses and evolutionary stages. The
ability to deduce the ages of stars with a relative precision of typically 10
to 20% is a unique opportunity for stellar evolution and also of great value
for both galactic and exoplanet studies. Further, a major uncalibrated
ingredient that makes stellar evolution models uncertain, is the stellar
interior rotation frequency $\Omega(r)$ and its evolution during stellar life.
We summarize the recent achievements in the derivation of $\Omega(r)$ for
different types stars, offering stringent observational constraints on
theoretical models. Core-to-envelope rotation rates during the red giant stage
are far lower than theoretical predictions, pointing towards the need to
include new physical ingredients that allow strong and efficient coupling
between the core and the envelope in the models of low-mass stars in the
evolutionary phase prior to the core helium burning. Stars are subject to
efficient mixing phenomena, even at low rotation rates. Young massive stars
with seismically determined interior rotation frequency reveal low
core-to-envelope rotation values.Comment: 10 pages, 5 figures, to appear in Astronomische
  Nachrichten/Astronomical Note
Gamma rays from a supernova of type Ia: SN2014J

SN2014J is the closest supernova of type Ia that occured in the last 40
years. This provides an opportunity for unprecedented observational detail and
coverage in many astronomical bands, which will help to better understand the
still unknown astrophysics of these supernovae. For the first time, such an
event occurs sufficiently nearby so that also gamma rays are able to contribute
to such investigations. This is important, as the primary source of the
supernova light is the radioactive energy from about 0.5 M$_\odot$ of $^{56}$Ni
produced in the explosion, and the gamma rays associated with this decay make
the supernova shine for months. The INTEGRAL gamma-ray observatory of ESA has
followed the supernova emission for almost 5 months. The characteristic gamma
ray lines from the $^{56}$Ni decay chain through $^{56}$Co to $^{56}$Fe have
been measured. We discuss these observations, and the implications of the
measured gamma-ray line characteristics as they evolve.Comment: 7 pages, 8 figures; highlight talk at AG conference Bamberg, Germany,
  Sep 201
Hot subdwarfs - Small stars marking important events in stellar
  evolution

Hot subdwarfs are considered to be the compact helium cores of red giants,
which lost almost their entire hydrogen envelope. What causes this enormous
mass loss is still unclear. Binary interactions are invoked and a significant
fraction of the hot subdwarf population is indeed found in close binaries. In a
large project we search for the close binary sdBs with the most and the least
massive companions. Significantly enhancing the known sample of close binary
sdBs we performed the first comprehensive study of this population. Triggered
by the discovery of two sdB binaries with close brown dwarf companions in the
course of this project, we were able to show that the interaction of stars with
substellar companions is an important channel to form sdB stars. Finally, we
discovered a unique and very compact binary system consisting of an sdB and a
massive white dwarf, which qualifies as progenitor candidate for a supernova
type Ia. In addition to that, we could connect those explosions to the class of
hypervelocity hot subdwarf stars, which we consider as the surviving companions
of such events. Being the stripped cores of red giants, hot subdwarfs turned
out to be important markers of peculiar events in stellar evolution ranging all
the way from star-planet interactions to the progenitors of stellar explosions
used to measure the expansion of our Universe.Comment: 10 pages, to appear in Reviews in Modern Astronomy 27, special issue
  of Astronomical Note
Schwarzschild Lecture 2014: HectoMAPping The Universe

During the last three decades progress in mapping the universe from an age of
400,000 years to the present has been stunning. Instrument/telescope
combinations have naturally determined the sampling of various redshift ranges.
Here we outline the impact of the Hectospec on the MMT on exploration of the
universe in the redshift range 0.2 < z < 0.8. We focus on dense redshift
surveys, SHELS and HectoMAP. SHELS is a complete magnitude limited survey
covering 8 square degrees. The HectoMAP survey combines a red-selected dense
redshift survey and a weak lensing map covering 50 square degrees. Combining
the dense redshift survey with a Subaru HyperSuprimeCam (HSC) weak lensing map
will provide a powerful probe of the way galaxies trace the distribution of
dark matter on a wide range of physical scales.Comment: 20 pages, 5 figure
TANAMI - Multiwavelength and Multimessenger Observations of Active
  Galaxies

Extragalactic jets launched from the immediate vicinity of supermassive black
holes in radio-loud active galactic nuclei (AGN) are key objects in modern
astronomy and astroparticle physics. AGN jets carry a fraction of the total
gravitational energy released during the accretion of matter onto supermassive
black holes and are prime suspects as possible sources of ultrahigh-energy
cosmic rays and the recently detected extraterrestrial neutrinos at PeV
energies. TANAMI (Tracking Active galactic Nuclei with Austral Milliarcsecond
Interferometry) is a multiwavelength program monitoring AGN jets of the
southern sky. It combines high-resolution imaging and spectral monitoring at
radio wavelengths with higher-frequency observations at IR, optical/UV, X-ray
and $\gamma$-ray energies. We review recent results of the TANAMI program,
highlighting AGN candidate neutrino-emitters in the error circles of the
IceCube PeV neutrino events.Comment: 7 pages, 1 figure, to appear in Astronomical Note
How environment drives galaxy evolution: lessons learnt from satellite
  galaxies

It is by now well established that galaxy evolution is driven by intrinsic
and environmental processes, both contributing to shape the observed properties
of galaxies. A number of early studies, both observational and theoretical,
have shown that the star formation activity of galaxies depends on their
environmental local density and also on galaxy hierarchy, i.e. centrals vs.
satellites. In fact, contrary to their central (most massive) galaxy of a
group/cluster, satellite galaxies are stripped of their gas and stars, and have
their star formation quenched by their environment. Large galaxy surveys like
SDSS now permit us to investigate in detail environment-driven transformation
processes by comparing centrals and satellites. In this paper I summarize what
we have so far learnt about environmental effects by analysing the observed
properties of local central and satellite galaxies in SDSS, as a function of
their stellar mass and the dark matter mass of their host group/cluster.Comment: 6 pages, 3 figure
Roche volume filling and the dissolution of open star clusters

From direct N-body simulations we find that the dynamical evolution of star
clusters is strongly influenced by the Roche volume filling factor. We present
a parameter study of the dissolution of open star clusters with different Roche
volume filling factors and different particle numbers. We study both Roche
volume underfilling and overfilling models and compare with the Roche volume
filling case. We find that in the Roche volume overfilling limit of our
simulations two-body relaxation is no longer the dominant dissolution mechanism
but the changing cluster potential. We call this mechnism "mass-loss driven
dissolution" in contrast to "two-body relaxation driven dissolution" which
occurs in the Roche volume underfilling regime. We have measured scaling
exponents of the dissolution time with the two-body relaxation time. In this
experimental study we find a decreasing scaling exponent with increasing Roche
volume filling factor. The evolution of the escaper number in the Roche volume
overfilling limit can be described by a log-logistic differential equation. We
report the finding of a resonance condition which may play a role for the
evolution of star clusters and may be calibrated by the main periodic orbit in
the large island of retrograde quasiperiodic orbits in the Poincar\'e surfaces
of section. We also report on the existence of a stability curve which may be
of relevance with respect to the structure of star clusters.Comment: 14 pages, 10+1 figures, accepted by Astronomische Nachrichte
A review of East Asian reports of aurorae and comets circa AD 775

Given that a strong 14C variation in AD 775 has recently been suggested to be
due to the largest solar flare ever recorded in history, it is relevant to
investigate whether celestial events observed around that time may have been
aurorae, possibly even very strong aurorae, or otherwise related to the 14C
variation (e.g. a suggested comet impact with Earth's atmosphere). We
critically review several celestial observations from AD 757 to the end of the
770s, most of which were previously considered to be true, and in some cases,
strong aurorae; we discuss in detail the East Asian records and their wording.
We conclude that probably none among the events after AD 770 was actually an
aurora, including the event in AD 776 Jan, which was misdated for AD 774 or
775; the observed white qi phenomenon that happened "above the moon" in the
south-east was most probably a halo effect near the full moon - too late in any
case to be related to the 14C variation in AD 774/5. There is another report of
a similar (or identical) white qi phenomenon "above the moon", reported just
before a comet observation and dated to AD 776 Jan; the reported comet observed
by the Chinese was misdated to AD 776, but actually sighted in AD 767. Our
critical review of East Asian reports of aurorae circa AD 775 shows some very
likely true Chinese auroral displays observed and reported for AD 762; there
were also several events prior to AD 771 that may have been aurorae but are
questionable.Comment: 15 pages with 4 figure
The Bochum Survey of the Southern Galactic Disk: II. Follow-up
  measurements and multi-filter photometry for 1323 square degrees monitored in
  2010-2015

This paper is the second in a series describing the southern Galactic Disk
Survey (GDS) performed at the Universit\"atssternwarte Bochum near Cerro
Armazones in Chile. Haas et al. (2012, Paper I) presented the survey design and
a the characteristics of the observations and data. They identified ~2200
variable stars in an area of 50 square degrees with more than 50 observations
in 2011. Here we present the first complete version of the GDS covering all 268
fields with 1323 square degrees along the Galactic disk including revised data
from Paper I. The individual fields were observed up to 272 times and comprise
a maximum time span between September 2010 and May 2015. We detect a total of
64151 variable sources, which are presented in a catalog including some of
their properties and their light curves. A comparison with the International
Variable Star Index (VSX) and All Sky Automated Survey (ASAS) indicates that
56794 of these sources are previously unknown variables. Furthermore, we
present UBVr'i'z' photometry for all sources within the GDS, resulting in a new
multi-color catalog of nearly 16x10^6 sources detected in at least one filter.
Both the GDS and the near-infrared VISTA Variables in the Via Lactea survey
(VVV) complement each other in the overlap area of about 300 square degrees
enabling future comparison studies
Transient accretion disc-like envelope in the symbiotic binary BF Cygni
  during its 2006 - 2015 optical outburst

The optical light of the symbiotic binary BF Cygni during its last eruption
after 2006 shows orbital variations because of an eclipse of the outbursting
compact object. The first orbital minimum is deeper than the following ones.
Moreover, the Balmer profiles of this system acquired additional satellite
components indicating bipolar collimated outflow at one time between the first
and second orbital minima. This behaviour is interpreted in the framework of
the model of collimated stellar wind from the outbursting object. It is
supposed that one extended disc-like envelope covering the accretion disc of
the compact object and collimating its stellar wind forms in the period between
the first and second minima. The uneclipsed part of this envelope is
responsible for the decrease of the depth of the orbital minimum. The
calculated $UBVR_{C}I_{C}$ fluxes of this uneclipsed part are in agreement with
the observed residual of the depths of the first and second orbital minima. The
parameters of the envelope require that it is the main emitting region of the
line H$\alpha$ but the H$\alpha$ profile is less determined from its rotation
and mostly from other mechanisms. It is concluded that the envelope is a
transient nebular region and its destruction determines the increase of the
depth of the orbital minimum with fading of the optical light.Comment: 5 pages, 1 figure; to be published in Astron. Nachrichten, in pres
Newly found sunspot observations by Peter Becker from Rostock for 1708,
  1709, and 1710

We present a few newly found old sunspot observations from the years AD 1708,
1709, and 1710, which were obtained by Peter Becker from Rostock, Germany. For
1709, Becker gave a detailed drawing: he observed a sunspot group made up of
two spots on Jan 5, 6, and 7, and just one of the two spots was observed on Jan
8 and 9. We present his drawing and his explanatory text. We can measure the
latitude and longitude of these two spots and estimate their sizes for all five
days. While the spots and groups in 1708 and the spot on four of the five days
in January 1709 were known before from other observers (e.g. Hoyt & Schatten
1998), the location of the spots in early January 1709 were not known before,
so that they can now be considered in reconstructed butterfly diagrams. The
sunspots detected by Becker on 1709 Jan 5 and 1710 Sep 10 were not known before
at all, as the only observer known for those two dates, La Hire, did not detect
that spot (group). We estimate new group sunspot numbers for the relevant days,
months, and years. The time around 1708--1710 is important, because it
documents the recovery of solar activity towards the end of the Maunder Grand
Minimum. We also show two new spot observations from G. Kirch for 1708 Sep 13
\& 14 as described in his letter to Wurzelbaur (dated Berlin AD 1708 Dec 19).Comment: 11 pages with 5 figures and 3 tables; Astronomical Notes, in press,
  to appear Sept 201
Formation of accretion centers in simulations of colliding uniform
  density H$_2$ cores

We test here the first stage of a route of modifications to be applied to the
public GADGET2 code for dynamically identifying accretion centers during the
collision process of two adjacent and identical gas cores. Each colliding core
has a uniform density profile and rigid body rotation; its mass and size have
been chosen to represent the observed core $L1544$; for the thermal and
rotational energy ratios with respect to the potential energy, we assume the
values $\alpha=0.3$ and $\beta=0.1$, respectively. These values favor the
gravitational collapse of the core. We here study cases of both -head-on and
off-center collisions, in which the pre-collision velocity increases the
initial sound speed of the barotropic gas by up to several times. In a
simulation the accretion centers are formed by the highest density particles,
so we here report their location and properties in order to realize the
collision effects on the collapsing and colliding cores. In one of the models
we observe a roughly spherical distribution of accretion centers located at the
front wave of the collision. In a forthcoming publication we will apply the
full modified GADGET code to study the collision of turbulent cores.Comment: accepted for publication in the journal Astronomische Nachrichte
Stellar science from a blue wavelength range - A possible design for the
  blue arm of 4MOST

From stellar spectra, a variety of physical properties of stars can be
derived. In particular, the chemical composition of stellar atmospheres can be
inferred from absorption line analyses. These provide key information on large
scales, such as the formation of our Galaxy, down to the small-scale
nucleosynthesis processes that take place in stars and supernovae. By extending
the observed wavelength range toward bluer wavelengths, we optimize such
studies to also include critical absorption lines in metal-poor stars, and
allow for studies of heavy elements (Z>38) whose formation processes remain
poorly constrained. In this context, spectrographs optimized for observing blue
wavelength ranges are essential, since many absorption lines at redder
wavelengths are too weak to be detected in metal-poor stars. This means that
some elements cannot be studied in the visual-redder regions, and important
scientific tracers and science cases are lost. The present era of large public
surveys will target millions of stars. Here we describe the requirements
driving the design of the forthcoming survey instrument 4MOST, a multi-object
spectrograph commissioned for the ESO VISTA 4m-telescope. We focus here on
high-density, wide-area survey of stars and the science that can be achieved
with high-resolution stellar spectroscopy. Scientific and technical
requirements that governed the design are described along with a thorough line
blending analysis. For the high-resolution spectrograph, we find that a
sampling of >2.5 (pixels per resolving element), spectral resolution of 18000
or higher, and a wavelength range covering 393-436 nm, is the most
well-balanced solution for the instrument. A spectrograph with these
characteristics will enable accurate abundance analysis (+/-0.1 dex) in the
blue and allow us to confront the outlined scientific questions. (abridged)Comment: 14 pages, 8 figures, accepted for publication in A
Isolated dSph galaxy KKs3 in the local Hubble flow

We present the SALT spectroscopy of a globular cluster in the center of the
nearby isolated dSph galaxy KKs3 situated at a distance of 2.12 Mpc. Its
heliocentric radial velocity is 316+-7 km/s that corresponds to V_{LG} = 112
km/s in the Local Group (LG) reference frame. We use its distance and velocity
along with the data on other 35 field galaxies in the proximity of the LG to
trace the local Hubble flow. Some basic properties of the local field galaxies:
their morphology, absolute magnitudes, average surface brightnesses, specific
star formation rates, and hydrogen mass-to-stellar mass ratios are briefly
discussed. Surprisingly, the sample of the neighboring isolated galaxies
displays no signs of compression under the influence of the expanding Local
Void.Comment: 12 pages, 6 figures, 1 table, accepted in the Astronomische
  Nachrichte
Variations of 14-C around AD 775 and AD 1795 - due to solar activity

The motivation for our study is the disputed cause for the strong variation
of 14-C around AD 775. Our method is to compare the 14-C variation around AD
775 with other periods of strong variability. Our results are: (a) We see three
periods, where 14-C varied over 200 yr in a special way showing a certain
pattern of strong secular variation: after a Grand Minimum with strongly
increasing 14-C, there is a series of strong short-term drop(s), rise(s), and
again drop(s) within 60 yr, ending up to 200 yr after the start of the Grand
Minimum. These three periods include the strong rises around BC 671, AD 775,
and AD 1795. (b) We show with several solar activity proxies (radioisotopes,
sunspots, and aurorae) for the AD 770s and 1790s that such intense rapid 14-C
increases can be explained by strong rapid decreases in solar activity and,
hence, wind, so that the decrease in solar modulation potential leads to an
increase in radioisotope production. (c) The strong rises around AD 775 and
1795 are due to three effects, (i) very strong activity in the previous cycles
(i.e. very low 14-C level), (ii) the declining phase of a very strong Schwabe
cycle, and (iii) a phase of very weak activity after the strong 14-C rise --
very short and/or weak cycle(s) like the suddenly starting Dalton minimum. (d)
Furthermore, we can show that the strong change at AD 1795 happened after a
pair of two packages of four Schwabe cycles with certain hemispheric leadership
(each package consists of two Gnevyshev-Ohl pairs, respectively two
Hale-Babcock pairs). We show with several additional arguments that the rise
around AD 775 was not that special. ...Comment: 25 pages with 11 figures and 2 tables - Astronomical Notes, in pres