1,150 research outputs found
E/E-product data management in consideration of model-based systems engineering
This paper presents objectives for permeable electric/electronics product data management for mechatronic products in consideration of model-based systems engineering from the early product development phase till a lifecycle management. Idiosyncrasies of mechatronic products, requirements engineering, model-based systems engineering, artifact-orientation, and interconnections of artifacts are evaluated and postulate objectives, how artifacts have to be designed in order to support the linkage of model-based systems engineering and product data management (PDM). The objectives, derived from the different theories and requirements to foster permeable PDM, are: i) Identify all existing norms for the development of mechanical, electronic, and software aspects and elaborate how information artifacts have to be defined. ii) (Textual) Requirements have to be technically feasible to be linked to information artifacts and system models already in the early development phase. iii) System models have to be aligned to information artifacts from the models' creation onwards and standardization in exchange formats has to be ensured. iv) Information artifacts with own lifecycles shall alleviate PDM in the early product development phase. v) Interconnections shall ameliorate associativity through capturing process information between single artifacts. A first concept is presented, visualizing the aforementioned objectives and their contribution in the early development process of mechatronic products, how a permeable PDM might be achieved
Iron in Hot DA White Dwarfs
We present a study of the iron abundance pattern in hot hydrogen-rich (DA)
white dwarfs. The study is based on new and archival far ultraviolet
spectroscopy of a sample of white dwarfs in the temperature range 30,000 K <
T_eff < 64,000 K. The spectra obtained with the Far Ultraviolet Spectroscopic
Explorer along with spectra obtained with the Hubble Space Telescope Imaging
Spectrograph and the International Ultraviolet Explorer sample FeIII to FeVI
absorption lines enabling a detailed iron abundance analysis over a wider range
of effective temperatures than previously afforded. The measurements reveal
abundance variations in excess of two orders of magnitude between the highest
and the lowest temperatures probed, but also show considerable variations (over
one order of magnitude) between objects with similar temperatures and surface
gravities. Such variations in cooler objects may be imputed to accretion from
unseen companions or so-called circumstellar debris although the effect of
residual mass-loss and selective radiation pressure in the hottest objects in
the sample remain dominant.Comment: Accepted for publication in Ap
A Meta-Model to Connect Model-based Systems Engineering with Product Data Management by Dint of the Blockchain
Quantitative spectral analysis of the sdB star HD 188112: a helium-core white dwarf progenitor
HD 188112 is a bright (V = 10.2 mag) hot subdwarf B (sdB) star with a mass
too low to ignite core helium burning and is therefore considered as a
pre-extremely low mass (ELM) white dwarf (WD). ELM WDs (M 0.3 Msun) are
He-core objects produced by the evolution of compact binary systems. We present
in this paper a detailed abundance analysis of HD 188112 based on
high-resolution Hubble Space Telescope (HST) near and far-ultraviolet
spectroscopy. We also constrain the mass of the star's companion. We use hybrid
non-LTE model atmospheres to fit the observed spectral lines and derive the
abundances of more than a dozen elements as well as the rotational broadening
of metallic lines. We confirm the previous binary system parameters by
combining radial velocities measured in our UV spectra with the already
published ones. The system has a period of 0.60658584 days and a WD companion
with M 0.70 Msun. By assuming a tidally locked rotation, combined with
the projected rotational velocity (v sin i = 7.9 0.3 km s) we
constrain the companion mass to be between 0.9 and 1.3 Msun. We further discuss
the future evolution of the system as a potential progenitor of a
(underluminous) type Ia supernova. We measure abundances for Mg, Al, Si, P, S,
Ca, Ti, Cr, Mn, Fe, Ni, and Zn, as well as for the trans-iron elements Ga, Sn,
and Pb. In addition, we derive upper limits for the C, N, O elements and find
HD 188112 to be strongly depleted in carbon. We find evidence of non-LTE
effects on the line strength of some ionic species such as Si II and Ni II. The
metallic abundances indicate that the star is metal-poor, with an abundance
pattern most likely produced by diffusion effects.Comment: Accepted for publication in A&
The Optical Transient Search in the Bamberg Southern Sky Survey: Preliminary Results
A large fraction of gamma-ray bursts temporarily emit optical light, i.e. optical afterglows and optical transients. So far, optical transients have only been detected after related gamma-ray satellite detection. However, taking into account their optical magnitudes at maximum light, these objects should be detectable in various historical and recent optical surveys, including the photographic sky patrol. Here we report on an extended study based on blink-comparison of 5004 Bamberg Observatory Southern Sky Patrol Plates performed within a student high school project (Jugend Forscht)
First Kepler results on compact pulsators II: KIC 010139564, a new pulsating subdwarf B (V361 Hya) star with an additional low-frequency mode
We present the discovery of nonradial pulsations in a hot subdwarf B star
based on 30.5 days of nearly continuous time-series photometry using the
\emph{Kepler} spacecraft. KIC 010139564 is found to be a short-period pulsator
of the V361 Hya (EC 14026) class with more than 10 independent pulsation modes
whose periods range from 130 to 190 seconds. It also shows one periodicity at a
period of 3165 seconds. If this periodicity is a high order g-mode, then this
star may be the hottest member of the hybrid DW Lyn stars. In addition to the
resolved pulsation frequencies, additional periodic variations in the light
curve suggest that a significant number of additional pulsation frequencies may
be present. The long duration of the run, the extremely high duty cycle, and
the well-behaved noise properties allow us to explore the stability of the
periodic variations, and to place strong constraints on how many of them are
independent stellar oscillation modes. We find that most of the identified
periodicities are indeed stable in phase and amplitude, suggesting a rotation
period of 2-3 weeks for this star, but further observations are needed to
confirm this suspicion.Comment: 10 pages, accepted for publication in MNRA
Substellar companions and the formation of hot subdwarf stars
"Copyright 2011 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics."We give a brief review over the observational evidence for close substellar companions to hot subdwarf stars. The formation of these core helium-burning objects requires huge mass loss of their red giant progenitors. It has been suggested that besides stellar companions substellar objects in close orbits may be able to trigger this mass loss. Such objects can be easily detected around hot subdwarf stars by medium or high resolution spectroscopy with an RV accuracy at the km s(-1)-level. Eclipsing systems of Vir type stick out of transit surveys because of their characteristic light curves. The best evidence that substellar objects in close orbits around sdBs exist and that they are able to trigger the required mass loss is provided by the eclipsing system SDSS J0820+0008, which was found in the course of the MUCHFUSS project. Furthermore, several candidate systems have been discovered.Final Accepted Versio
Multi-object spectroscopy of stars in the CoRoT fields I: Early-type stars in the CoRoT-fields IRa01, LRa01, LRa02
Observations of giant stars indicate that the frequency of giant planets is
much higher for intermediate-mass stars than for solar-like stars. Up to now
all known planets of giant stars orbit at relatively far distances from their
host stars. It is not known whether intermediate-mass stars also had many
close-in planets when they were on the main sequence, which were then engulfed
when the star became a giant star. To understand the formation and evolution of
planets it is therefore important to find out whether main-sequence stars of
intermediate-mass have close-in planets or not. A survey for transiting planets
of intermediate-mass stars would be ideal to solve this question, because the
detection of transiting planets is not affected by the rapid rotation of these
stars. As a first step for an efficient survey we need to identify
intermediate-mass stars in the CoRoT-fields, which can then be used as an input
list. To compile the input list we derived the spectral types of essentially
all O, B and A stars down to 14.5 mag in the CoRoT fields IRa01, LRa01, LRa02
taken with the multi-object spectrograph AAOmega. We determined the spectral
types by comparing the spectra with template spectra from a library. In total
we identify 1856 A and B stars that have been observed with CoRoT. Given the
number of planets that have been detected in these fields amongst late-type
stars, we estimate that there are one to four transiting planets of
intermediate-mass stars waiting to be discovered. Our survey not only allows us
to carry out a dedicated planet search programme but is also essential for any
types of studies of the light curves of early-type stars in the CoRoT database.
We also show that it would be possible to extend the survey to all fields that
CoRoT has observed using photometrically determined spectral types.Comment: 57 pages, 12 figures, accepted for publication in Astronomy and
Astrophysic
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