854 research outputs found
Stellar activity and rotation of the planet host Kepler-17 from long-term space-borne photometry
The study of young Sun-like stars is of fundamental importance to understand
the magnetic activity and rotational evolution of the Sun. Space-borne
photometry by the Kepler telescope provides unprecedented datasets to
investigate these phenomena in Sun-like stars. We present a new analysis of the
entire Kepler photometric time series of the moderately young Sun-like star
Kepler-17 that is accompanied by a transiting hot Jupiter. We applied a
maximum-entropy spot model to the long-cadence out-of-transit photometry of the
target to derive maps of the starspot filling factor versus the longitude and
the time. These maps are compared to the spots occulted during transits to
validate our reconstruction and derive information on the latitudes of the
starspots. We find two main active longitudes on the photosphere of Kepler-17,
one of which has a lifetime of at least days, although with a
varying level of activity. The latitudinal differential rotation is of solar
type, that is, with the equator rotating faster than the poles. We estimate a
minimum relative amplitude between
and , our determination being affected by the finite lifetime of
individual starspots and depending on the adopted spot model parameters. We
find marginal evidence of a short-term intermittent activity cycle of
days and an indication of a longer cycle of days characterized by an
equatorward migration of the mean latitude of the spots as in the Sun. The
rotation of Kepler-17 is likely to be significantly affected by the tides
raised by its massive close-by planet. We confirm the reliability of
maximum-entropy spot models to map starspots in young active stars and
characterize the activity and differential rotation of this young Sun-like
planetary host.Comment: Accepted by Astronomy and Astrophysics - 22 pages, 29 figure, 1
table, 2 appendixe
Directorium divini cultus ad Cathedralis Ecclesiae Minoriccensis : eiusque Dioecesis usum
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Directorium divini cultus ad Cathedralis Ecclesiae Minoriccensis : eiusque Dioecesis usum
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A Study of the Advances in IoT Security
The Internet-of-things (IoT) holds a lot of benefits to our lives by removing menial tasks and improving efficiency of everyday objects. You are trusting your personal data and device control to the manufactures and you may not be aware of how much risk your putting your privacy at by sending your data over the internet. The internet-of-things may not be as secure as you think when the devices used are constrained by a lot of variables which attackers can exploit to gain access to your data / device and anything they connected to and as the internet-of-things is all about connecting devices together one weak point can be all it takes to gain full access. In this paper we have a look at the current advances in IoT security and the most efficient methods to protect IoT devices
Matching fields of a long superconducting film
We obtain the vortex configurations, the matching fields and the
magnetization of a superconducting film with a finite cross section. The
applied magnetic field is normal to this cross section, and we use London
theory to calculate many of its properties, such as the local magnetic field,
the free energy and the induction for the mixed state. Thus previous similar
theoretical works, done for an infinitely long superconducting film, are
recovered here, in the special limit of a very long cross section.Comment: Contains a REVTeX file and 4 figure
The hind- and midfoot alignment analyzed after a medializing calcaneal osteotomy using a 3D weight bearing CT
Reliability and correlation analysis of computed methods to convert conventional 2D radiological hindfoot measurements to 3D equivalents using weight bearing CT
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