37,213 research outputs found
Signature of non-isotropic distribution of stellar rotation inclination angles in the Praesepe cluster
The distribution of the stellar rotation axes of 113 main sequence stars in
the open cluster Praesepe are examined by using current photometric rotation
periods, spectroscopic rotation velocities, and estimated stellar radii. Three
different samples of stellar rotation data on spotted stars from the Galactic
field and two independent samples of planetary hosts are used as control
samples to support the consistency of the analysis. Considering the high
completeness of the Praesepe sample and the behavior of the control samples, we
find that the main sequence F - K stars in this cluster are susceptible to
rotational axis alignment. Using a cone model, the most likely inclination
angle is 76+/-14 degrees with a half opening angle of 47+/-24 degrees.
Non-isotropic distribution of the inclination angles is preferred over the
isotropic distribution, except if the rotation velocities used in this work are
systematically overestimated. We found no indication of this being the case on
the basis of the currently available data.Comment: Accepted for publication in Astronomy & Astrophysics: 5 pages with 4
figure
Are the gyro-ages of field stars underestimated?
By using the current photometric rotational data on eight galactic open
clusters, we show that the evolutionary stellar model (isochrone) ages of these
clusters are tightly correlated with the period shifts applied to the (B-V)_0 -
P_rot ridges that optimally align these ridges to the one defined by Praesepe
and the Hyades. On the other hand, when the traditional Skumanich-type
multiplicative transformation is used, the ridges become far less aligned due
to the age-dependent slope change introduced by the period multiplication.
Therefore, we employ our simple additive gyro-age calibration on various
datasets of Galactic field stars to test its applicability. We show that, in
the overall sense, the gyro-ages are systematically greater than the isochrone
ages. The difference could exceed several giga years, depending on the stellar
parameters. Although the age overlap between the open clusters used in the
calibration and the field star samples is only partial, the systematic
difference indicates the limitation of the currently available gyro-age methods
and suggests that the rotation of field stars slows down with a considerably
lower speed than we would expect from the simple extrapolation of the stellar
rotation rates in open clusters.Comment: 10 pages, 15 figures; accepted for publication in Astronomy &
Astrophysic
Synergies between Exoplanet Surveys and Variable Star Research
With the discovery of the first transiting extrasolar planetary system back
to 1999, a great number of projects started to hunt for other similar systems.
Because of the incidence rate of such systems was unknown and the length of the
shallow transit events is only a few percent of the orbital period, the goal
was to monitor continuously as many stars as possible for at least a period of
a few months. Small aperture, large field of view automated telescope systems
have been installed with a parallel development of new data reduction and
analysis methods, leading to better than 1% per data point precision for
thousands of stars. With the successful launch of the photometric satellites
CoRot and Kepler, the precision increased further by one-two orders of
magnitude. Millions of stars have been analyzed and searched for transits. In
the history of variable star astronomy this is the biggest undertaking so far,
resulting in photometric time series inventories immensely valuable for the
whole field. In this review we briefly discuss the methods of data analysis
that were inspired by the main science driver of these surveys and highlight
some of the most interesting variable star results that impact the field of
variable star astronomy.Comment: This is a review presented at "Wide-field variability surveys: a
21st-century perspective" - 22nd Los Alamos Stellar Pulsation Conference
Series Meeting, held in: San Pedro de Atacama, Chile, Nov. 28-Dec. 2, 2016.
To appear in Web of Conferences Journal: 13 pages, 8 figure
Gender Equality in Virtual Work II.: Regulatory Suggestions
This article focuses on gender equality in virtual work, taking special account of the regulatory
challenges. It contributes to broader debates on the workers' situation in the sharing economy in two
ways. Firstly, it makes an inaugural attempt to evaluate the implications of the new forms of work in
the sharing economy for female virtual workers, looking at the issue of equal treatment. Secondly, it
offers preliminary suggestions regarding a future regulation to improve equality between genders in
virtual work.
This is the second part of a paper on gender equality in virtual work. The first part (published in
the 2018/1 issue of the Hungarian Labour Law E-Journal) defined "virtual work", classified its two
basic forms and emphasised the specific traits of this form of work to demonstrate the need of special
protection against discrimination. Subsequently, it identified the possible beneficial and adverse
implications of virtual work for female workers and gender equality.
This second part firstly provides a summary of the gender equality law of the European Union
that serves as a point of reference when speaking about antidiscrimination law. Section 2 offers three
normative perspectives and suggestions as to how to enhance gender equality in virtual work. Finally,
the paper concludes
Gender Equality in Virtual Work I.: Risks
This article focuses on gender equality in virtual work, taking special account of the regulatory
challenges. It contributes to broader debates on the workers' situation in the sharing economy in two
ways. Firstly, it makes an inaugural attempt to evaluate the implications of the new forms of work in
the sharing economy for female virtual workers, looking at the issue of equal treatment. Secondly, it
offers preliminary suggestions regarding a future regulation to improve equality between genders in
virtual work.
The paper is divided into four main parts. The first section defines "virtual work", classifies its two
basic forms and emphasises the specific traits of this form of work to demonstrate the need of special
protection against discrimination. Secondly, the paper identifies the possible beneficial and adverse
implications of virtual work for female workers and gender equality. Thirdly, the paper provides a
summary of the gender equality law of the European Union that serves as a point of reference when
speaking about antidiscrimination law. Section 4 offers three normative perspectives and suggestions
as to how to enhance gender equality in virtual work. Finally, the paper concludes.
This first part of this two-part paper concentrates on the risks of virtual work for equal treatment,
while the second part is going to address the regulatory options and suggestions
Are all RR Lyrae stars modulated?
We analyzed 151 variables previously classified as fundamental mode RR Lyrae
stars from Campaigns 01-04 of the Kepler two wheel (K2) archive. By employing a
method based on the application of systematics filtering with the aid of
co-trending light curves in the presence of the large amplitude signal
component, we searched for additional Fourier signals in the close neighborhood
of the fundamental period. We found only 13 stars without such components,
yielding the highest rate of 91% of modulated (Blazhko) stars detected so far.
A detection efficiency test suggests that this occurrence rate likely implies a
100% underlying rate. Furthermore, the same test performed on a subset of the
Large Magellanic Cloud RR Lyrae stars from the MACHO archive shows that the
conjecture of high true occurrence rate fits well to the low observed rate
derived from this database.Comment: Submitted to Astronomy & Astrophysics (6 pages, 8 figures
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