bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Search for Extraterrestrial Eukaryotes: Biological and Planetary Science Aspects
Authors: Chela-Flores Julian 
Published: July 2016

AbstractOne pressing question in bioastronomy is to attempt to devise assays in the search for extraterrestrial eukaryotes (SETE). In the positive case of encountering a fossil of a certain microorganism, it is not yet clear how to identify it in an unequivocal manner, even if found arrested and preserved in the midst of biological activity, as in some known Archean sediments on Earth. On the other hand, for living microorganisms the present approach may have some advantages over the straightforward probe of the morphological features of the putative eukaryote, as we argue that we are not constrained to base identification on morphological properties, such as the presence of organelles, which are known to be missing in some higher taxa. We sketch a possible experimental set-up required for a robot to investigate whether eukaryogenesis has already taken place in Mars or Europa. Besides, we also discuss the biological and astronomical implications of a SETE program. Previous observation and theoretical work have suggested that underneath the ice crust of the Jovian satellite Europa there may be an ocean of liquid water. We therefore argue that as hot springs may be present at the bottom of that ocean, eukaryotes should be searched for, not only deep in the Martian permafrost, as discussed by others, but a SETE program should be extended to the aquatic environment of the Jovian satellite as well. Our current work emphasising gene silencing, may suggest how to decide on the degree evolution which microbiota may have reached in the Europa ocean, a topic which deserves our attention, as eukaryogenesis is the process which introduced the basic cellular plan of those Earth-bound organisms that have been raised to the level of intelligent beings. We make a specific suggestion for a robotic investigation of eukaryogenesis in solar system exploration.
The Ohio Seti Program and the Argus Telescope
Authors: Dixon Robert S. 
Published: July 2016

AbstractThe Ohio State SETI program has been in operation since 1974, making it the longest-running search. The Ohio State radio telescope is equivalent in size to a 175-foot circular dish. The latest and best all-sky meridian-transit survey is about 60% complete, searching in the Water Hole (1.4 to 1.7 GHz). Signals detected are automatically examined at greater resolution and then tracked for up to 1 hour. A dual-beam pattern-matching system is used for real-time signal detection and RFI rejection. A new 4 million channel receiver built at UC Berkeley is now being installed. A simultaneous broadband continuum survey at 1415 MHz is in progress, searching for natural radio sources that have changed since the previous OSU continuum survey was made 20 years ago. A new radio telescope called Argus is being designed that will look in all directions simultaneously, allow usage by everyone simultaneously, and have no moving or machined parts. It is a large timed array which is based on computers rather than steel. All possible beams are formed all the time, so there is no scanning or need to «point» the telescope. This approach has many advantages over dish-type telescopes, such as RFI rejection and retroactive observations. Ohio State University has decided to abandon its radio telescope at the end of 1997 and allow it to be torn down by land developers.
Twenty Years of Serendip, The Berkeley Seti Effort: Past Results and Future Plans
Authors: Bowyer Stuart , Werthimer Dan , Donnelly Charles , Cobb Jeff , Ng David , Lampton Michael 
Published: July 2016

AbstractThe Berkeley SETI effort has been ongoing for more than twenty years. During this period we have carried out extensive SETI searches, but of at least equal importance, we have been on the forefront of instrumentation development, the development of interference rejection and detection algorithms, and educational efforts. Our instrumentation has evolved from a 100 channel spectrometer (SERENDIP I) to our latest machine (SERENDIP IV) with 168 million channels. In addition to supporting our SETI work, our hardware has been used by NASA for RFI surveys and to check the Mars Survey relay transmitter. Our designs have influenced several of the major SETI hardware systems, and a SERENDIP III system is currently being used in the Ohio State SETI group. Our hardware has also been incorporated in pulsar instrumentation at NAIC (Arecibo), NRAO (Greenbank) and Bonn, Germany. We have just completed a 4 year search at the world’s largest radio telescope at Arecibo. We covered 93% of the observable sky at least once, and 44% of the sky at least 5 times, with a sensitivity of ~ 3 × l0−25Wm−2. We collected and analyzed information from over 1014spectral bins and logged and analyzed over 2 × 108signals of potential special interest. We have developed extensive analysis programs to identify and remove interference and to search for signal characteristics which are expected from an extraterrestrial signal. Our algorithms were successful in removing all but 0.01% of spurious RFI in the Arecibo data set. We have involved over 30 undergraduate and graduate students in our effort, and 5 Master's theses have been awarded for work on the SERENDIP project. Our next effort will use our SERENDIP IV hardware at Arecibo Observatory to carry out a 21 cm survey of the Arecibo sky.
The Berkeley Seti Program: Serendip IV Instrumentation
Authors: Werthimer Dan , Bowyer Stuart , Ng David , Donnelly Charles , Cobb Jeff , Lampton Michael , Airieau Sabine 
Published: July 2016

AbstractThe SERENDIP program is an ongoing search for narrow band radio signals from extraterrestrial civilizations. Each generation SERENDIP instrument has on average been about 35 times more powerful than its predecessor. In this paper we discuss the hardware design of the latest generation instrument, SERENDIP IV, which will be deployed in early 1997 for a 21 cm sky survey at the National Astronomy and Ionospheric Center’s 305 meter radio telescope in Arecibo, Puerto Rico. SERENDIP IV is a 167 million channel spectrum analyzer, covering a 100 Mhz bandwidth, with 0.6 Hz resolution and a 1.7 second integration time. SERENDIP IV’s modular design incorporates a bank of digital mixers and filters to separate the 100 MHz band into forty 2.5 MHz sub-bands. Each 2.5 MHz sub-band is further broken down into 0.6 Hz bins by means of a four million point fast Fourier transform. The resulting power spectra are analyzed by 40 high speed processors. Narrow band signals having power significantly above background noise levels are recorded along with telescope coordinates, time, and frequency. The data are sent in real time to Berkeley for analysis. SERENDIP IV hardware is also utilized by the Ohio State University SETI program and pulsar programs at Nancay Observatory (France), the US Naval Research Lab, the Effelsberg telescope (Germany), NRAO’s Greenbank Observatory and NAIC’s Arecibo Observatory.
A New Class of Seti Targets
Authors: Shostak G. Seth 
Published: July 2016

AbstractA new class of SETI targets is proposed, consisting of stellar systems whose ecliptic planes coincide with our line-of-sight. The most favorable of these systems are moderately separated, edge-on binary stars with at least one solar-type component. Such targets maximize the likelihood that a transmitting civilization’s antennas are beamed in our direction, and therefore represent an improvement over current experiments by approximately 106per target. While few favorable systems are known, this is a consequence of historical selection effects in the observation of binaries. An estimate of their frequency shows that a thousand such systems exist within 1,200 ly of the Sun.
A New Major Seti Project Based on Project Serendip Data and 100,000 Personal Computers
Authors: Sullivan Woodruff T. , Werthimer Dan , Bowyer Stuart , Cobb Jeff , Gedye David , Anderson David 
Published: July 2016

AbstractWe are now developing an innovative SETI project, tentatively named seti@home, involving massively parallel computation on desktop computers scattered around the world. The public will be uniquely involved in a real scientific project. Individuals will download a Screensaver program that will not only provide the usual attractive graphics when their computer is idle, but will also perform sophisticated analysis of SETI data using the host computer. The data are tapped off Project Serendip IV’s receiver and SETI survey operating on the 305-meter diameter Arecibo radio telescope. We make a continuous tape-recording of a 2 MHz bandwidth signal centered on the 21 cm H I line. The data on these tapes are then preliminarily screened and parceled out by a server that supplies small chunks of data (50 sec of 20 kHz bandwidth, a total of 0.25 MB) over the Internet to clients possessing the screen-saver software. After the client computer has automatically analyzed a complete chunk of data (in a much more detailed manner than Serendip normally does) a report on the best candidate signals is sent back to the server, whereupon a new chunk of data is sent out. If 50,000-100,000 customers can be achieved, the computing power will be equivalent to a substantial fraction of a typical supercomputer, and seti@home will cover a comparable volume of parameter space to that of Serendip IV.
Internal Dynamics of Slowly Rotating Stars: the Effect of μ-Gradients on the Meridional Circulation
Authors: Théado S. , Vauclair S. 
Published: July 2016

AbstractIn slowly rotating stars, the coupling of helium settling and meridional circulation leads to a particular hydrodynamical process which was not introduced in previous computations of abundance variations. The μ-gradients induced by element settling can lead to a quasi-paralysis stage in which the efficiencies of both the meridional circulation and the microscopic diffusion are strongly reduced. Such an effect was studied in the eighties for nuclear-induced μ-gradients by Mestel et al., who called it “creeping paralysis”. Below convective zones, this process has important consequences. Here we discuss the case of the halo stars and the sun.
RR Lyrae Variables in Local Group Galaxies: M31
Authors: Clementini G. , Federici L. , Cacciari C. , Bellazzini M. , Corsi C. , Smith H.A. 
Published: July 2016

AbstractCandidate RR Lyrae variables have been identified for the first time in four globular clusters of the Andromeda galaxy (M31). Using HST-WFPC2 archive observations we have found 2, 4, 11 and 8 RR Lyrae variables of both ab and c Bailey types in G11, G33, G64 and G322 (Sargent et al., 1977), respectively. These numbers are quite consistent with the horizontal branch morphology exhibited by the four clusters.
The Contribution of GEOS to the Study of Stellar Pulsations
Authors: Boninsegna R. , Vandenbroere J. ,   the GEOS team, Le Borgne J.F. 
Published: July 2016

The GEOS, Groupe Européen d’Observation Stellaires, is composed of observers living in France, Italy, Spain, Belgium and Switzerland. The main purpose is to give amateur astronomers the opportunity of carrying out scientific analyses in specific fields. Further details can be found at the web site http://www.upv.es/geos/In the past years, GEOS has approached the analysis of visual estimates of variable stars (Ralincourt et al., 1987) in an original manner, obtaining accurate light curves on red semiregulars. Moreover, the collaboration with teams of professional researchers allowed the group to obtain interesting results on the double-mode Cepheid EW Set (Figer et al., 1991), on the Be star OT Gem (Arellano Ferro et al., 1998) and on the eclipsing binary V753 Cyg (Beltraminelli et al., 2000). More recently, several GEOS members have started collecting a large sample of times of maximum brightness of RR Lyr stars in order to build-up a database as extensive as possible. Such a database is decribed below together with the results of a campaign on RR Lyr itself.
Search for Nonradial Pulsations in the Be Star ω Ori during the MuSiCoS Campaign 1998
Authors: Neiner C. , Hubert A.-M. , Floquet M. , Henrichs H.F. ,   the MuSiCoS team
Published: July 2016

Abstractω Ori is a rapidly rotating B2IIIe star with known spectral variability. We applied a frequency analysis to the MuSiCoS (MUlti Site Continuous Spectroscopy) campaign 1998-dataset to search for line-profile variations (Ipv). Variability was found in all studied spectral lines and interpreted as due to non-radial pulsations (NRP).
HR 4074: an Emission-Free NRP Twin of the Be Star 28 CMa
Authors: Štefl S. , Rivinius Th. , Baade D. 
Published: July 2016

In spite of considerable progress in the investigation of rapid line-profile variations (lpv) of Be stars, at least two models still compete in the literature: the rotational modulation, assuming mostly corotating circumstellar structures (Balona, 2000), and nonradial pulsations (Maintz et al. and Rivinius et al., these proceedings). Attempts to explain the lpv of Be stars were often connected with the proto-typical star 28 (ω) CMa (HR 2749 = HD 56139, B2IV-Ve, v sin i = 80 km/s). Štefl et al. (1998) described variability in three line-profile components: in the narrow component of the line core, in the line core itself and in the wings. The Balmer emission of 28 CMa is variable and has always been observed to be at least moderate, mostly strong.HR 4074 (HD 89890, B3 III, v sin i = 70 km/s) has a different history of its emission activity. From a single spectrogram taken in 1893, Pickering (1898) reported an emission in Hβ. Subsequent observations never confirmed this. If it was not mis-identified by Pickering, HR 4074 would be in the probably longest B-star phase known of any Be star. HR 4074 is very probably not an SPB star - the spectral type is too early, the rotational velocity too high and light variations too low for this classification. Baade (1984) detected rapid lpv with a period P ≈ 2.25 d. Our time series analysis of radial velocity (RV) variations, measured as line modes, and that of full profiles give P = (2.3179 ± 0.0008) d.
Spectroscopy of Rapidly Oscillating Ap Stars
Authors: Weiss W.W. , Ryabchikova T.A. , Savanov I. , Piskunov N. , Tsymbal V. , Mittermayer P. , Martinez P. , Kochukhov O. , Nesvacil N. 
Published: July 2016

AbstractWe identify Spectroscopic differences between roAp stars and Ap stars with no observational evidence for pulsation, but with otherwise similar Teff and log g values. These differences concern the abundance pattern, Hydrogen line profile anomalies, evidence for stratification, and effects of pulsation on spectral lines.
Problems with the Pulsation Mode Selection Mechanism in the Lower Instability Strip (Observations and Theory)
Authors: Breger M. , Pamyatnykh A.A. 
Published: July 2016

AbstractWe examine the severe disagreement between the number of predicted and observed pulsation modes for δ Scuti stars. The selection of nonradial modes trapped in the outer envelope is considered on the basis of kinetic energy arguments. The trapped l = 1 modes for the star 4 CVn are in good, but not perfect agreement with the observations. The trapping of the l = 2 modes is weaker, so that this simple rule of mode selection may apply to l = 1, and possibly not to l = 2 modes.
P-Mode Observations on α Cen A with CORALIE
Authors: Carrier F. , Bouchy F. , Meynet G. , Maeder A. , Provost J. , Berthomieu G. , Morel P. , Thévenin F. 
Published: July 2016

AbstractWe have made a clear detection of p-mode oscillations in the G2V star α Cen A with the CORALIE spectrograph. The power spectrum clearly shows several identifiable peaks between 1.8 and 2.9 mHz. A preliminary astrophysical interpretation of these p-modes is presented.
Asteroseismology of Delta Scuti Stars – A Parameter Study
Authors: Templeton M. , Basu S. , Demarque P. 
Published: July 2016

AbstractWe assess the potential of asteroseismology for determining the fundamental properties of individual δ Scuti stars. We computed a grid of evolution and adiabatic pulsation models to study systematic changes in l = 0,1,2, and 3 modes as functions of fundamental stellar properties. Mass has the strongest effect on evolution and on pulsation, followed by the metal abundance. Changes to the helium content have very little effect on the frequencies until near the end of the main sequence. Changes to each of the four parameters change the p-mode frequencies more than they do the g- and mixed-mode frequencies, suggesting that these parameters have a greater effect on the outer layers of the star. We also present pulsation models of FG Virginis, outlining a possible method of locating favorable models in the stellar parameter space based upon a definitive identification of only two modes. We plot evolution models on the (period-period ratio) and (temperature-period ratio) planes to select candidate models, and modify the core overshooting parameter to fit the observed star.
Towards Ensemble Asteroseismology of the Pulsating DB White Dwarf Stars
Authors: Handler G. , Wood M.A. , Nitta A. ,   the Whole Earth Telescope Network of Collaborators
Published: July 2016

The origin of the helium-atmosphere DB white dwarfs is still a matter of debate. In particular, the question is unresolved whether binary evolution produces a significant number of DBs. The pulsating DB white dwarfs (DBV stars) offer a complementary insight into this problem through asteroseismology; DBs descending from binaries will have different interior structures than DBs originating from single stars (Nitta & Winget, 1998).GD 358 is by far the best-observed pulsating DBV star, and the only one for which asteroseismology has been performed to date. This star’s structure has been shown to be inconsistent with an origin from binary evolution (Nitta & Winget, 1998), but most of the other DBVs are relatively poorly studied.We therefore analysed archival data on all DBVs and obtained new measurements of stars with very little data available (Table 1), firstly to identify suitable targets for asteroseismological investigations and secondly to examine the pulsation spectra of the DBVs as a group, following the works of Clemens (1994) and Kleinman (1995) on the pulsating DA white dwarfs. Our study also produced new seismological results on individual stars and promising targets for future Whole Earth Telescope (WET, Nather et al., 1990) runs.
Brief Review of Solar Models and Solar Neutrino Experiments
Authors: Morrison Douglas R.O. 
Published: July 2016

AbstractSolar Evolutionary Models are briefly reviewed and while the models are robust, there are uncertainties in the input data which justify rather larger errors. The 1992 experimental results from GALLEX, SAGE II and Kamiokande are shown to be consistent with calculated fluxes of solar neutrinos whereas the Chlorine results continue to be significantly low though this experiment has a problem with the high variability with time of its results in contradiction to Kamiokande. It is concluded that the evidence for a solar neutrino problem is not compelling and New Physics are not demanded. Further experiments are essential to search for neutrino masses and to study the Sun.
Influence of Rotation on the Stellar Parameters
Authors: Wenske V. , Schönberner D. 
Published: July 2016

For several years it has become quite common to derive stellar parameters like effective temperature, Teff, and surface acceleration, g, by means of properly calibrated photometric indices, and to use these values for the derivation of important properties of stellar aggregates (viz. ages, star formation history, distances, etc.). Photometric observations, however, fail to give informations about one important property of a star: its rotational rate!The main effect of rotation is to increase the size of the star, mainly in the equatorial region, leading to lower surface temperatures and accelerations. Since in non–spherical stars Teff and g depend on the latitude, the observed values, which are, of course, averages over the visible hemisphere, depend on the angle of inclination, i. Collins & Sonneborn (1977) utilized the rigidly rotating stellar models of Sackmann and Anand (1970) to compute emergent fluxes and photometric indices for various stellar masses, inclination angles i and rotational parameters being the break–up rotational rate. These indices, viz. C0 and β, represent then averages over the visible part of the rotally distorted stellar models. Closer inspections indicated also that emergent fluxes and line profiles of rotationally distorted stars can be matched by the predictations of standard model atmospheres to a very high accuray, even for w close to unity (Wenske 1992, Diplom Thesis).
Coulomb Interactions in the Equation of State
Authors: Stolzmann W. , Blöcker T. 
Published: July 2016

Various models are used in order to develop an accurate equation of state (EOS) for stellar matter (see e.g. Saumon and Chabrier 1991). The complexity of physical effects, for instance degeneracy, relativity, Coulomb- and non-Coulombic interactions requires detailed knowledge from the many-particle physics.For many applications it is desirable to have theories for these effects over a wide range of densities and temperatures. One of the main sources of uncertainties in the EOS models is the exchange-correlation contribution at any degeneracy and relativity. Previous investigations determine thermodynamic quantities of a partially (e.g. Graboske et al. 1969, Kraeft et al. 1986, Däppen et al. 1988) or fully ionized (e.g. Hubbard and DeWitt 1985, Ichimaru et al. 1987) plasma, resp. Interpolation procedures (Magni and Mazzitelli 1979, Fontaine et al. 1977) combine both cases in the EOS but show non-continuous behaviour.
Observable Effects of Rotation on Stellar Abundances
Authors: Balachandran Suchitra 
Published: July 2016

AbstractThis is a review of our understanding of the effects of rotation on the stellar interior through an examination of observed surface stellar abundances. First, the evolution of angular momentum from the pre-main sequence through the giant phase is summarized. Attempts are then made to decipher the signature of abundance anomalies due to meridional circulation and rotational braking with reference to available theoretical models. Finally, special cases such as tidally-locked binaries and chromospherically-active giants are examined to determine if their rotational peculiarites have induced abundance anomalies.
Rotational Velocity Dispersion in the Hyades and Other Galactic Clusters From The V Sin I Observations
Authors: Gaigé Yves 
Published: July 2016

Let us recall briefly the main points of the theory as developped by Chandrasekhar and Münch (1950): if the axis of rotation of a star is inclined with an angle i to the line of sight, the apparent velocity is given by y = v sin i where v is the true rotational velocity. Assuming that the axes of rotation are randomly distributed in space, the frequency function f(v) of the true velocities may be related to the corresponding φ(y) of the apparent ones by the integral equations:The central moments of f(v) can be derived directly from the observations by means of (1) without the knowledge of the function itself; for instance, the mean and the mean square deviation are given respectively by: