scholarly journals Dynamo-generated magnetic fields in fast rotating single giants

2008 ◽  
Vol 4 (S259) ◽  
pp. 433-434 ◽  
Author(s):  
Renada Konstantinova-Antova ◽  
Michel Aurière ◽  
Klaus-Peter Schröder ◽  
Pascal Petit
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Stellar Evolution ◽  
Red Giants ◽  
Good Opportunity ◽  
Early Results ◽  
First Time ◽  
Fast Rotating

AbstractRed giants offer a good opportunity to study the interplay of magnetic fields and stellar evolution. Using the spectro-polarimeter NARVAL of the Telescope Bernard Lyot (TBL), Pic du Midi, France and the LSD technique we began a survey of magnetic fields in single G-K-M giants. Early results include 6 MF-detections with fast rotating giants, and for the first time a magnetic field was detected directly in an evolved M-giant: EK Boo. Our results could be explained in the terms of α–ω dynamo operating in these giants.

Introductory remarks

1994 ◽  
Vol 349 (1690) ◽  
pp. 169-170
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Royal Society ◽  
Lunar Regolith ◽  
The Moon ◽  
Global Magnetic Field ◽  
The Subject ◽  
Planetary Missions ◽  
Speculative Hypothesis ◽  
First Time

This year marks not only the twenty-fifth anniversary of the first manned landing on the Moon ( Apollo 11 ) but also the thirty-fifth anniversary of the first planetary missions. The latter was the Soviet Luna 1 and 2 carrying magnetometers to test whether the Moon possessed a global magnetic field. Luna 1 passed the Moon but Luna 2 crash landed, both showed that the Moon had no magnetic field as large as 50 or 100 y (1 y = 10 -5 G = 10 -9 T). Such an experiment had been proposed by S. Chapman ( Nature 160, 395 (1947)) to test a speculative hypothesis concerning magnetic fields of cosmic bodies by P. M. S. Blackett ( Nature 159, 658 (1947)). Chapman’s suggestion was greeted by general amusement: 12 years later it was accomplished. Also two years after the launch of Sputnik 1 in 1957, Luna 3 was launched and for the first time viewed the far side of the Moon on 9 October, 1959. Laboratories from many countries were invited by NASA to take part in the analysis of rocks returned from the Apollo missions and later from the Soviet automated return of cores from the lunar regolith. British laboratories were very active in this work, and a review of the results of the new understanding of the Moon as a result of space missions formed the subject of a Royal Society Discussion Meeting in 1975 (published in Phil. Trans. R. Soc. Lond . A 285). British laboratories received samples from the automated Soviet missions that took cores from the regolith and returned them to Earth. Work on Luna 16 and 20 samples were published in Phil. Trans. R. Soc. Lond . A 284 131-177 (1977) and on Luna 24 in Phil. Trans. R. Soc. Lond . A 297 1-50 (1979).

scholarly journals Spectropolarimetric study of selected cool supergiants

2014 ◽  
Vol 9 (S307) ◽  
pp. 369-370
Author(s):  
V. Butkovskaya ◽  
S. Plachinda ◽  
D. Baklanova
Keyword(s):  
Magnetic Fields ◽  
Stellar Evolution ◽  
Good Opportunity ◽  
Classical Cepheids

AbstractCool supergiants offer a good opportunity to study the interplay of magnetic fields and stellar evolution. We present the results of spectropolarimetric study of the cool supergiants and classical Cepheids η Aql and ζ Gem.

scholarly journals Magnetic Field Effect in the Process of Rinsing a Magnetic Separator Matrix

1988 ◽  
Vol 2 (3) ◽  
pp. 119-136
Author(s):  
Jiri Galas
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Circuit Design ◽  
Field Effect ◽  
Magnetic Circuit ◽  
Magnetic Field Effect ◽  
Magnetic Separator ◽  
High Gradient ◽  
First Time

This paper surveys fundamental aspects of the problem of rinsing matrices in high gradient magnetic separators. This is done, for the first time, in terms of the magnetic circuit design. Equations have been constructed to describe the effects of spurious remanent magnetic fields on the rinsing process.

scholarly journals Observations of Lithium in red giant stars

2009 ◽  
Vol 5 (S268) ◽  
pp. 301-309
Author(s):  
Verne V. Smith
Keyword(s):  
Stellar Evolution ◽  
Asymptotic Giant Branch ◽  
Red Giants ◽  
Asymptotic Giant Branch Stars ◽  
Multiple Sources ◽  
Lithium Abundance ◽  
Giant Stars ◽  
Red Giant ◽  
First Time ◽  
Giant Branch Stars

AbstractConnections between observations of the lithium abundance in various types of red giants and stellar evolution are discussed here. The emphasis is on three main topics; 1) the depletion of Li as stars ascend the red giant branch for the first time, 2) the synthesis of 7Li in luminous and massive asymptotic giant branch stars via the mechanism of hot-bottom burning, and 3) the possible multiple sources of excess Li abundances found in a tiny fraction of various types of G and K giants.

scholarly journals MHD Models of Planetary Nebulae: Review

2003 ◽  
Vol 209 ◽  
pp. 457-464 ◽  
Author(s):  
Guillermo García-Segura
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Ab Initio ◽  
Radiation Pressure ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Basic Question ◽  
Red Giants ◽  
Outer Envelope ◽  
Parent Star

When we discuss about MHD effects in planetary nebulae (PNe), there naturally arises a basic question: which magnetic field do we study? One possibility is the ISM magnetic field (e.g. Heiligman 1980), even more if we are concerned with moving PNe (e.g. Soker & Dgani 1997). The next possibility is the internal or stellar magnetic field (Gurzadian 1962). It is important to start this review by quoting Aller (1958): “It has been pointed out by Minkowski and others that the structural appearance of many planetary nebulae strongly suggest the presence of magnetic fields. It seems unlikely that such magnetic fields are produced ab initio in the nebular shell. Rather, they must have existed in the outer envelope of the parent star. Certain red giants stars with magnetic fields may evolve in such a way that the expansion of the shell is largely governed by the presence of such a field. Magnetic effects may actually be more important than gas pressure differentials and radiation pressure in controlling the evolution of a planetary nebula”.

scholarly journals Butterfly diagram of a Sun-like star observed using asteroseismology

2018 ◽  
Vol 619 ◽  
pp. L9 ◽  
Author(s):  
M. Bazot ◽  
M. B. Nielsen ◽  
D. Mary ◽  
J. Christensen-Dalsgaard ◽  
O. Benomar ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Stellar Evolution ◽  
Theoretical Models ◽  
Observational Constraint ◽  
Stellar Rotation ◽  
Magnetic Field Generation ◽  
Rotation Rates ◽  
Butterfly Diagram ◽  
Stellar Magnetic Fields ◽  
First Time

Stellar magnetic fields are poorly understood, but are known to be important for stellar evolution and exoplanet habitability. They drive stellar activity, which is the main observational constraint on theoretical models for magnetic field generation and evolution. Starspots are the main manifestation of the magnetic fields at the stellar surface. In this study we measured the variation in their latitude with time, called a butterfly diagram in the solar case, for the solar analogue HD 173701 (KIC 8006161). To this end, we used Kepler data to combine starspot rotation rates at different epochs and the asteroseismically determined latitudinal variation in the stellar rotation rates. We observe a clear variation in the latitude of the starspots. It is the first time such a diagram has been constructed using asteroseismic data.

scholarly journals Proto-Planetary Nebulae

1978 ◽  
Vol 76 ◽  
pp. 305-313 ◽  
Author(s):  
B. Zuckerman
Keyword(s):  
Stellar Evolution ◽  
Planetary Nebula ◽  
White Dwarfs ◽  
Planetary Nebulae ◽  
Red Giants ◽  
Intermediate Mass ◽  
Gaseous Nebulae ◽  
First Time

Although rare, planetary nebulae have been extensively studied by astronomers. This affection is certainly due in part to the beauty of the gaseous nebulae but it is also due to the belief that many, probably most, stars of intermediate mass (1–4 M) become planetary nebulae at least once during their lifetimes. If the planetary nebula is an (almost) inevitable stage in stellar evolution, it is important to determine its evolutionary precursors and followers. The latter are likely to be the white dwarfs and the former are generally believed to be red giants. With the advent of infrared and radio techniques it now appears possible, for the first time, to specify the immediate progenitors of planetary nebulae.

scholarly journals Radio-continuum surveys with SKA and LOFAR: a first look at the perspectives for radio mini-halos

2018 ◽  
Vol 617 ◽  
pp. A11 ◽  
Author(s):  
M. Gitti ◽  
G. Brunetti ◽  
R. Cassano ◽  
S. Ettori
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
High Redshift ◽  
Low Frequency ◽  
Physical Nature ◽  
Radio Continuum ◽  
X Ray ◽  
Statistical Studies ◽  
Low Magnetic Field ◽  
First Time

Context. Diffuse synchrotron radio emission has been observed in a number of cool-core clusters on scales comparable to that of the cooling region. These radio sources are called “mini-halos”. In order to understand their origin, which is still unclear, joint radio and X-ray statistical studies of large cluster samples are necessary to investigate the radio mini-halo properties and their connection with the cluster thermodynamics. Aims. We here extend our previous explorative study and investigate the perspectives offered by surveys in the radio continuum with the LOw Frequency ARray (LOFAR) and the Square Kilometre Array (SKA), in particular examining the effect of the intracluster magnetic field in the mini-halo region for the first time. Methods. By considering the minimum flux detectable in radio surveys and exploiting the Pradio − LX correlation observed for known mini-halos, we estimate the detection limits achievable by future radio observational follow-up of X-ray cluster samples, such as HIFLUGCS and eROSITA. This allows us to estimate the maximum number of radio mini-halos that can potentially be discovered in future surveys as a function of redshift and magnetic field strength. Results. Under the optimistic assumption that all cool-core systems host a mini-halo and that the radio versus X-ray scaling relation extends to systems with lower X-ray luminosity, we show that future radio surveys with LOFAR and SKA1 (at ∼140 MHz and ∼1.4 GHz) have the potential to discover ∼1000–10 000 radio mini-halo candidates up to redshift z =  1. This shows that these surveys may be able to produce a breakthrough in the study of these sources. We further note that future SKA1 radio surveys at redshift z > 0.6 will allow us to distinguish between different magnetic fields in the mini-halo region, because higher magnetic fields are expected to produce more powerful mini-halos, thus implying a larger number of mini-halo candidates detected at high redshift. For example, the non-detection with SKA1 of mini-halos at z > 0.6 will suggest a low magnetic field (B < few μG). The synergy of these radio surveys with future X-ray observations and theoretical studies is essential in establishing the radio mini-halo physical nature.

scholarly journals Surface magnetic fields across the HR Diagram

2014 ◽  
Vol 10 (S305) ◽  
pp. 12-21
Author(s):  
John D. Landstreet
Keyword(s):  
Magnetic Field ◽  
Stellar Evolution ◽  
Field Structure ◽  
Stellar Structure ◽  
Detailed Data ◽  
Magnetic Field Structure ◽  
The Past ◽  
Magnetic Stars ◽  
First Time ◽  
Broad Outline

AbstractThe past 20 years have seen remarkable advances in spectropolarimetric instrumentation that have allowed us, for the first time, to identify some magnetic stars in most major stages of stellar evolution. We are beginning to see the broad outline of how such fields change during stellar evolution, to confront theoretical hypotheses and models of magnetic field structure and evolution with detailed data, and to understand more of the ways in which the presence of a field in turn affects stellar structure and evolution.

scholarly journals The influence of the Earth’s magnetic field on strapdown inertial gravimetry using Q-Flex accelerometers: static and dynamic experiments

2021 ◽  
Vol 95 (9) ◽  
Author(s):  
Felix Johann ◽  
David Becker ◽  
Matthias Becker ◽  
Matthias Hoss ◽  
Alexander Löwer ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Measurement Errors ◽  
Calibration Function ◽  
Earth’S Magnetic Field ◽  
Dynamic Experiments ◽  
Dependent Measurement ◽  
Earth's Magnetic Field ◽  
First Time ◽  
Calibration Approach

AbstractIn recent strapdown airborne and shipborne gravimetry campaigns with servo accelerometers of the widely used Q-Flex type, results have been impaired by heading-dependent measurement errors. This paper shows that the effect is, in all likelihood, caused by the sensitivity of the Q-Flex type sensor to the Earth’s magnetic field. In order to assess the influence of magnetic fields on the utilised strapdown IMU of the type iMAR iNAV-RQH-1003, the IMU has been exposed to various magnetic fields of known directions and intensities in a 3-D Helmholtz coil. Based on the results, a calibration function for the vertical accelerometer is developed. At the example of five shipborne and airborne campaigns, it is outlined that under specific circumstances the precision of the gravimetry results can be strongly improved using the magnetic calibration approach: The non-adjusted RMSE at repeated lines decreased from 1.19 to 0.26 mGal at a shipborne campaign at Lake Müritz, Germany. To the knowledge of the authors, a significant influence of the Earth’s magnetic field on strapdown inertial gravimetry is demonstrated for the first time.

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