pinecone/core-2020-05-10-deduplication huggingface dataset:
The Stellar Activity - Rotation Relationship

Using a new catalog of 824 solar and late-type stars with X-ray luminosities
and rotation periods we have studied the relationship between rotation and
stellar activity. From an unbiased subset of this sample the power law slope of
the unsaturated regime, $L_X/L_{bol}\propto Ro^\beta$, is fit as
$\beta=-2.70\pm0.13$. This is inconsistent with the canonical $\beta=-2$ slope
to a confidence of 5$\sigma$ and argues for an interface-type dynamo.
Super-saturation is observed for the fastest rotators in our sample and its
parametric dependencies are explored. Significant correlations are found with
both the corotation radius and the excess polar updraft, the latter theory
being supported by other observations. We also present a new X-ray population
synthesis model of the mature stellar component of our Galaxy and use it to
reproduce deep observations of a high Galactic latitude field. The model,
XStar, can be used to test models of stellar spin-down and dynamo decay, as
well as for estimating stellar X-ray contamination rates for non-stellar
studies.Comment: 4 pages, 4 figures. To appear in the proceedings of Cool Stars 17:
  17th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, AN 334,
  1-2, Eds Klaus Strassmeier and Mercedes Lopez-Morale
Starspots and spin-orbit alignment for Kepler cool host stars

The angle between the spin axis of the host star and the orbit of its planets (i.e., the stellar obliquity) is precious information about the formation and evolution of exoplanetary systems. Measurements of the Rossiter-McLaughlin effect revealed that many stars that host a hot-Jupiter have high obliquities, suggesting that hot-Jupiter formation involves excitation of orbital inclinations. In this contribution we show how the passage of the planet over starspots can be used to measure the obliquity of exoplanetary systems. This technique is used to obtain – for the first time – the obliquity of a system with several planets that lie in a disk, Kepler-30, with the result that the star has an obliquity smaller than 10 degrees. The implications for the formation of exoplanetary systems, in particular the hot-Jupiter population, are also discussed
The stratified evolution of a cool star

A low mass star usually experiences stratification and abundance anomalies
during its evolution. A 0.95 solar mass star with a metallicity Z = 0.004 is
followed from the main-sequence to the Horizontal Branch (HB). On the
main-sequence the larger effects of stratification may come from accretion as
was suggested in relation to metallicity and planet formation. As it evolves
through the giant branch, stratification appears around the hydrogen burning
shell. It may create hydrodynamic instabilities and be related to abundance
anomalies on the giant branch. After the He flash the star evolves to the HB.
If it loses enough mass, it ends up a hot HB star (or in the field an sdB star)
with effective temperatures larger than 11000 K. All sdB stars are observed to
have an approximately solar iron abundance whatever their original metallicity,
implying overabundances by factors of up to 100. So should the 0.95 solar mass
star. How its internal hydrodynamic properties on the main sequence may
influence its fate on the HB is currently uncertain.Comment: Astronomische Nachrichten - Astronomical Notes (AN) papers presented
  at the Cool Stars 17 conference 2012 (AN 334, issue 1-2
A multiwavelength view of star-disk interaction in NGC 2264

Variability is a signature property of cool young stars, particularly for
those surrounded by disks. Traditional single-band time series display complex
features associated with accretion, disk structure, and accompanying stellar
activity, but these processes are challenging to model. To make progress in
connecting observed time domain properties with the underlying physics of young
stars and their disks, we have embarked on an unprecedented multiwavelength
monitoring campaign: the Coordinated Synoptic Investigation of NGC 2264 ("CSI
2264"). Beginning in December 2011, CSI 2264 has acquired 30 continuous days of
mid-infrared time series from Spitzer, simultaneous optical monitoring from
CoRoT and MOST, X-ray observations with Chandra, as well as complementary data
from a number of ground-based telescopes. The extraordinary photometric
precision, cadence, and time baseline of these observations enable detailed
correlation of variability properties at different wavelengths, corresponding
to locations from the stellar surface to the inner AU of the disk. We present
the early results of the program, and discuss the need for further modeling
efforts into young stars and their disks.Comment: Astronomische Nachrichten (AN) Vol 334, in press; contribution to
  proceedings of the 17th Cambridge Workshop on Cool Stars, Stellar Systems and
  the Sun (ed. Strassmeier & Lopez-Morales); 4 pages, 4 figure
Accretion, winds and outflows in young stars

Young stars and planetary systems form in molecular clouds. For classical T
Tauri stars (CTTS, F-K type precursors) the accretion disk does not reach down
to the central star, but it is truncated near the co-rotation radius. The inner
edge of the disk is ionized by the stellar radiation, so that the accretion
stream is funneled along the magnetic field lines. On the stellar surface an
accretion shock develops, which is observed over a wide wavelength range as
X-ray emission, UV excess, optical veiling and optical and IR emission lines.
Some of the accretion tracers, e.g. H\alpha, can be calibrated to measure the
accretion rate. This accretion process is variable on time scales of hours to
years due to changing accretion rates, stellar rotation and reconfiguration of
the magnetic field. Furthermore, many accreting systems also drive strong
outflows which are ultimately powered by accretion. Several components could
contribute to the outflows: slow, wide-angle disk winds, X-winds launched close
to the inner disk rim, and thermally driven stellar winds. In any case, the
outflows contain material of very different temperatures and speeds. The disk
wind is cool and can have a molecular component with just a few tens of km/s,
while the central component of the outflow can reach a few 100 km/s. In some
cases the inner part of the outflow is collimated to a small-angle jet. These
jets have an onion-like structure, where the inner components are consecutively
hotter and faster. The jets can contain working surfaces, which show up as
Herbig-Haro knots. Accretion and outflows in the CTTS phase do not only
determine stellar parameters like the rotation rate on the main-sequence, they
also can have a profound impact on the environment of young stars. This review
concentrates on CTTS in near-by star forming regions where observations of high
spatial and spectral resolution are available.Comment: accepted by AN, to appears as special issue "Proceedings of Cool
  Stars 17
The SLoWPoKES Catalog of Low-mass Ultra-wide Binaries: A Cool Stars
  Resource for Testing Fundamental Properties and for Constraining Binary
  Formation Theory

We present results from the Sloan Low-mass Wide Pairs of Kinematically
Equivalent Stars (SLoWPoKES) catalog of ultra-wide (10^3-10^5.5 AU), low-mass
(K5-M7) common proper motion binaries. We constructed a Galactic model, based
on empirical stellar number density and 3D velocity distributions, to select
bona fide pairs with probability of chance alignment <5%, making SLoWPoKES an
efficient sample for followup observations. Our initial catalog contains 1342
disk dwarf, subdwarf, and white dwarf-red dwarf systems and is the largest
collection of low-mass, wide binaries ever assembled. The diversity---in mass,
metallicity, age, and evolutionary states---of SLoWPoKES pairs makes it a
valuable resource of coeval laboratories to examine and constrain the physical
properties of low-mass stars. SLoWPoKES pairs show signatures of two (or more)
formation modes in the distribution of the physical separation and higher-order
multiplicity. Neither dynamical dissipation of primordial triples/quadruples or
dynamical capture of ejected stars can explain the observed populations by
itself. We use followup spectroscopic observations to recalibrate the
metallicity-sensitive {\zeta}_(TiO/CaH) index by assuming that both members of
the binary system have the same composition. Our new formulation is a
significantly better tracer of absolute metallicity, particularly for the
early-type M dwarfs. The SLoWPoKES catalog is publicly available on a custom
data visualization portal.Comment: To appear in Cool Star XVII proceeding
Infrared Parallaxes of Young Field Brown Dwarfs and Connections to
  Directly Imaged Gas-Giant Exoplanets

We have measured high-precision parallaxes for a large sample of candidate
young (~10-100 Myr) and intermediate-age (~100-600 Myr) ultracool dwarfs, with
spectral types ranging from M8 to T2.5. These objects are compelling benchmarks
for substellar evolution and ultracool atmospheres at lower surface gravities
(i.e., masses) than most of the field population. We find that the absolute
magnitudes of our young sample can be systematically offset from ordinary
(older) field dwarfs, with the young late-M objects being brighter and the
young/dusty mid-L (L3-L6.5) objects being fainter, especially at J band. Thus,
we conclude the "underluminosity" of the young planetary-mass companions HR
8799b and 2MASS J1207-39b compared to field dwarfs is also manifested in young
free-floating brown dwarfs, though the effect is not as extreme. At the same
time, some young objects over the full spectral type range of our sample are
similar to field objects, and thus a simple correspondence between youth and
magnitude offset relative to the field population appears to be lacking.
Comparing the kinematics of our sample to nearby stellar associations and
moving groups, we identify several new moving group members, including the
first free-floating L dwarf in the AB Dor moving group, 2MASS J0355+11.
Altogether, the effects of surface gravity (age) and dust content on the
magnitudes and colors of substellar objects appear to be degenerate.Comment: Proceedings of Cool Stars 1
On the feasibility of employing solar-like oscillators as detectors for
  the stochastic background of gravitational waves

We present a hydrodynamic model that describes excitation of linear stellar
oscillations by a stochastic background of gravitational waves (SBGW) of
astrophysical and cosmological origin. We find that this excitation mechanism
is capable of generating solar g-mode amplitudes close to or comparable with
values expected from excitation by turbulent convection, which is considered to
be the main driving force for solar-like oscillations. A method is presented
that places direct upper bounds on the SBGW in a frequency range, in which the
SBGW is expected to contain rich astrophysical information. Employing estimates
for solar g-mode amplitudes, the proposed method is demonstrated to have the
potential to compete with sensitivities reached by gravitational wave
experiments in other frequency ranges.Comment: 5 pages, 2 figures. Proceedings of the ESF conference "The modern Era
  of Helio- and Asteroseismology" 2012. Identical to published versio
Long-term photometry of three active red giants in close binary systems:
  V2253 Oph, IT Com and IS Vir

We present and analyze long-term optical photometric measurements of the
three active stars V2253 Oph, IT Com and IS Vir. All three systems are
single-lined spectroscopic binaries with an early K giant as primary component
but in different stages of orbital-rotational synchronization. Our photometry
is supplemented by 2MASS and WISE near-IR and mid-IR magnitudes and then used
to obtain more accurate effective temperatures and extinctions. For V2253 Oph
and IT Com, we found their spectral energy distributions consistent with pure
photospheric emission. For IS Vir, we detect a marginal mid-IR excess which
hints towards a dust disk. The orbital and rotational planes of IT Com appear
to be coplanar, contrary to previous findings in the literature. We apply a
multiple frequency analysis technique to determine photometric periods, and
possibly changes of periods, ranging from days to decades. New rotational
periods of 21.55+-0.03d, 65.1+-0.3d, and 23.50+-0.04d were determined for V2253
Oph, IT Com, and IS Vir, respectively. Splitting of these periods led to
tentative detections of differential surface rotations of delta P/P ~0.02 for
V2253 Oph and 0.07 for IT Com. Using a time-frequency technique based on
short-term Fourier transforms we present evidence of cyclic light variations of
length ~10yrs for V2253 Oph and 5-6yrs for IS Vir. A single flip-flop event has
been observed for IT Com of duration 2-3yrs. Its exchange of the dominant
active longitude had happened close to a time of periastron passage, suggesting
some response of the magnetic activity from the orbital dynamics. The 21.55-d
rotational modulation of V2253 Oph showed phase coherence also with the orbital
period, which is 15 times longer than the rotational period, thus also
indicating a tidal feedback with the stellar magnetic activity.Comment: 13 pages, 14 figures, accepted to A
X-ray observations of the merging cluster CIZA J2242.8+5301

Multiwavelength studies of radio relics at merger shocks set powerful
constraints on the relics origin and formation mechanism. However, for X-ray
observations, a main difficulty is represented by the low X-ray surface
brightness far out in the cluster outskirts, where relics are typically found.
Here, we present XMM-Newton results from a 130-ks observation of CIZA
J2242.8+5301, a cluster at z=0.19 that hosts a double radio relic. We focus on
the well-defined northern relic. There is a difference of ~55% between the
temperature we measure behind the relic, and the temperature measured with
Suzaku. We analyse the reasons for this large discrepancy, and discuss the
possibility of reliably measuring the temperature beyond the northern relic.Comment: To appear in the proceedings of the conference "Galaxy Clusters as
  Giant Cosmic Laboratories", which will be published as a regular issue of the
  Astronomische Nachrichten (AN
Some results on the radio-SZ correlation for galaxy cluster radio halos

We present correlation results for the radio halo power in galaxy clusters
with the integrated thermal Sunyaev-Zel'dovich (SZ) effect signal, including
new results obtained at sub-GHz frequencies. The radio data is compiled from
several published works, and the SZ measurements are taken from the Planck ESZ
cluster catalog. The tight correlation between the radio halo power and the SZ
effect demonstrates a clear correspondence between the thermal and non-thermal
electron populations in the intra-cluster medium, as already has been shown in
X-ray based studies. The radio power varies roughly as the square of the global
SZ signal, but when the SZ signal is scaled to within the radio halo radius the
correlation becomes approximately linear, with reduced intrinsic scatter. We do
not find any strong indication of a bi-modal division in the radio halo cluster
population, as has been reported in the literature, which suggests that such
duality could be an artifact of X-ray selection. We compare the SZ signal
dependence of radio halos with simplified predictions from theoretical models,
and discuss some implications and shortcomings of the present work.Comment: To be published in the Astronomische Nachrichten (AN); proceeding
  article for the XMM-Newton 2012 science workshop: "Galaxy Clusters as Giant
  Cosmic Laboratories
The jet feedback mechanism (JFM): from supernovae to clusters of
  galaxies

We study the similarities of jet-medium interactions in several quite
different astrophysical systems using 2D and 3D hydrodynamical numerical
simulations, and find many similarities. The systems include cooling flow (CF)
clusters of galaxies, core-collapse supernovae (CCSNe), planetary nebulae
(PNe), and common envelope (CE) evolution. The similarities include hot bubbles
inflated by jets in a bipolar structure, vortices on the sides of the jets,
vortices inside the inflated bubbles, fragmentation of bubbles to two and more
bubbles, and buoyancy of bubbles. The activity in many cases is regulated by a
negative feedback mechanism. Namely, higher accretion rate leads to stronger
jet activity that in turn suppresses the accretion process. After the jets
power decreases the accretion resumes, and the cycle restarts. In the case of
CF in galaxies and clusters of galaxies we also study the accretion process,
which is most likely by cold clumps, i.e., the cold feedback mechanism. In CF
clusters we find that heating of the intra-cluster medium (ICM) is done by
mixing hot shocked jet gas with the ICM, and not by shocks. Our results
strengthen the jet feedback mechanism (JFM) as a common process in many
astrophysical objects.Comment: An extended version of a paper submitted to the proceedings of Galaxy
  Clusters as Giant Cosmic Laboratories (ESAC, Madrid, Spain 21st - 23rd May
  2012) to be published at Astronomische Nachrichte
The origin of the chemical elements in cluster cores

Metals play a fundamental role in ICM cooling processes in cluster cores
through the emission of spectral lines. But when and how were these metals
formed and distributed through the ICM? The X-ray band has the unique property
of containing emission lines from all elements from carbon to zinc within the
0.1-10 keV band. Using XMM-Newton, the abundances of about 11 elements are
studied, which contain valuable information about their origin. Most elements
were formed in type Ia and core-collapse supernovae, which have very different
chemical yields. Massive stars and AGB stars also contribute by providing most
of the carbon and nitrogen in the ICM. Because feedback processes suppress star
formation in the cluster centre, the element abundances allow us to directly
probe the star formation history of the majority of stars that are thought to
have formed between z=2-3. The spatial distribution in the core and the
evolution with redshift also provide information about how these elements are
transported from the member galaxies to the ICM. I review the current progress
in chemical enrichment studies of the ICM and give an outlook to the future
opportunities provided by XMM-Newton's successors, like Astro-H.Comment: 6 pages, 6 figures, accepted for publication in Astronomische
  Nachrichten (AN) as part of the proceedings of the XMM-Newton Science
  Workshop: "Galaxy Clusters as Giant Cosmic Laboratories" at ESAC, Madrid,
  Spain, 21-23 May 201
Metal jumps across sloshing cold fronts: the case of A496

Cold-fronts in cool-core clusters are thought to be induced by minor mergers
and to develop through a sloshing mechanism. While temperature and
surface-brightness jumps have been detected and measured in many systems, a
detailed characterization of the metal abundance across the discontinuity is
only available for a handful of objects. Within the sloshing scenario, we
expect the central cool and metal rich gas to be displaced outwards into lower
abundance regions, thus generating a metal discontinuity across the front. We
analyzed a long (120 ksec) XMM-Newton observation of A496 to study the metal
distribution and its correlation with the cold-fronts. We find Fe
discontinuities across the two main cold-fronts located ~60 kpc NNW and ~160
kpc South of the peak and a metal excess in the South direction.Comment: 4 pages; proceedings of the XMM-Newton Science Workshop: "Galaxy
  Clusters as Giant Cosmic Laboratories" at ESAC, Madrid, Spain, 21-23 May
  2012; accepted for publication in Astronomische Nachrichten (AN
The XMM Cluster Survey: Present status and latest results

The XMM Cluster Survey (XCS) is a serendipitous search for galaxy clusters using all publicly available data in the XMM‐ Newton  Science Archive. Our recent first data release (XCS‐DR1) contains 503 optically confirmed groups and clusters, among which 256 new to the literature and 357 whose X‐ray emission was detected for the first time. We discuss their properties and provide an update on the work being done. As examples of the applications of XCS‐DR1, we mention the 17 fossil groups/clusters identified with the help of the Sloan Digital Sky Survey. Their brightest galaxies have stellar populations and star‐formation histories which are similar to normal brightest cluster galaxies, but their stellar masses are significantly larger and correspond to a much bigger fraction of the total group/cluster optical luminosity. We also highlight the 15 clusters expected tobe also detected by the  Planck  satellite, and characterize the expected overlap between the final XCS and  Planck  cluster catalogues. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
Galaxy And Mass Assembly (GAMA): The M-Z relation for galaxy groups

The stellar mass and metallicity are among the fundamental parameters of
galaxies. An understanding of the interplay between those properties as well as
their environmental dependence will give us a general picture of the physics
and feedback processes ongoing in groups of galaxies. We study the
relationships and environmental dependencies between the stellar mass, and gas
metallicity for more than 1900 galaxies in groups up to redshift 0.35 using the
Galaxy And Mass Assembly (GAMA) survey. Using a control sample of more than
28,000 star-forming field galaxies, we find evidence for a decrement of the gas
metallicity for galaxies in groups.Comment: 4 pages, 2 figures, referee proceeding of the XMM-Newton 2012 Science
  Workshop: "Galaxy Clusters as Giant Cosmic Laboratories
The 2200 A bump and the UV extinction curve

The 2200 A bump is a major figure of interstellar extinction. Extinction
curves with no bump however exist and are, with no exception, linear from the
near-infrared down to 2500 A at least, often over all the visible-UV spectrum.
The duality linear versus bump-like extinction curves can be used to
re-investigate the relationship between the bump and the continuum of
interstellar extinction, and answer questions as why do we observe two
different kinds of extinction (linear or with a bump) in interstellar clouds?
How are they related? How does the existence of two different extinction laws
fits with the requirement that extinction curves depend exclusively on the
reddening E(B-V) and on a single additional parameter? What is this free
parameter?
  It will be found that (1) interstellar dust models, which suppose the
existence of three different types of particles, each contributing to the
extinction in a specific wavelength range, fail to account for the
observations; (2) the 2200 A bump is very unlikely to be absorption by some yet
unidentified molecule; (3) the true law of interstellar extinction must be
linear from the visible to the far-UV, and is the same for all directions,
including other galaxies.
  In extinction curves with a bump the excess of starlight (or the lack of
extinction) observed at wavelengths less than lambda=4000 A is due to a large
contribution of light scattered by hydrogen on the line of sight. Although
counter-intuitive this contribution is predicted by theory. The free parameter
of interstellar extinction is related to distances between the observer, the
cloud on the line of sight, and the star behind it (the parameter is likely to
be the ratio of the distances from the cloud to the star and to the observer).
The continuum of the extinction curve or the bump contain no information
concerning the chemical composition of interstellar cloud.Comment: 10 pages, 2 figure