 |
|
The missing link in the evolution of magnetic cataclysmic stars?
September 17, 2007An international team of astronomers might have discovered the missing link in the evolution of the so-called magnetic cataclysmic variable stars. They determined the spin and orbital periods of the binary star Paloma. They found that the Paloma system has a weird way of rotating that fills the gap between two classes of magnetic cataclysmic stars. Their results will soon be published in Astronomy & Astrophysics.
Cataclysmic variables (CVs) are a class of binary stars made up of a white dwarf [1] and a normal star much like our Sun. Both stars orbit so close to each other that the white dwarf accretes matter from the companion star. In most of the several hundred CVs known, the matter spirals around the white dwarf, forming a disk, before being accreted and incorporated into the star. About 20% of the known CVs include a white dwarf with a strong magnetic field of several million Gauss [2]. They are known as "magnetic CVs". The magnetic field of the white dwarf can be strong enough to disrupt the accretion disk or even to prevent the disc from forming.
Astronomers currently know two classes of magnetic CVs:
* Polars (also known as the prototype star AM Herculis) have a strong enough magnetic field to synchronize the spin period of the stars and the orbital period of the system [3]. A departure from synchronization is observed for four AM Herculis stars, which are thought to be normal AM Herculis systems currently desynchronized by a recent nova explosion. The difference between the spin period and the orbital period, that is, the degree of asynchronism, is less than 2% for these near-synchronous polars.
* Intermediate polars (known as DQ Herculis stars) have a lower magnetic field, and the spin period of the stars is shorter than the orbital period. The majority of the DQ Herculis stars have orbital periods longer than 3 hours and spin periods ranging from 33 seconds to 1 hour.
In a cataclysmic variable system, both stars are so close to each other (the whole system would match the size of our Sun) that astronomers cannot distinguish one star from the other. For studying CVs, they rely on indirect observations: measuring the variation in the brightness of the system, thereby estimating its characteristics (orbit size, period).
Dr. R. Schwarz and his colleagues [4] studied the candidate magnetic CV Paloma (also known as RX J0524+42), which has not yet been characterised. It does not fit either of the known CVs categories. The team presents both long- and short-term monitoring of this stellar system, using several European telescopes (1.2m OHP, 70 cm AIP, 1.23m Calar Alto), over a period ranging from 1995 to 2001. With this monitoring, they built the light curves and estimated the periods of the system. ROSAT observations of the system confirm that it has a strong magnetic field and thus belongs to the magnetic CVs.
From their observations, the team concludes that the faster white dwarf performs 14 spins around its own axis during 13 orbital revolutions. The weird degree of synchronization of the system presents the characteristics that makes Paloma so interesting. This bridges the gap between the two main classes of magnetic CVs: it spins much more slowly than any known intermediate polar, but is too much desynchronized to be an AM Herculis star. Paloma thus revives the old idea that both classes are evolutionarily linked together and that intermediate polars are the ancestors of the older AM Herculis stars. Theoreticians predict that Paloma is in the process of synchronization and should become a spin-locked AM Herculis star over the next 100 million years.
Journal Astronomy & Astrophysics
* Polars (also known as the prototype star AM Herculis) have a strong enough magnetic field to synchronize the spin period of the stars and the orbital period of the system [3]. A departure from synchronization is observed for four AM Herculis stars, which are thought to be normal AM Herculis systems currently desynchronized by a recent nova explosion. The difference between the spin period and the orbital period, that is, the degree of asynchronism, is less than 2% for these near-synchronous polars.
* Intermediate polars (known as DQ Herculis stars) have a lower magnetic field, and the spin period of the stars is shorter than the orbital period. The majority of the DQ Herculis stars have orbital periods longer than 3 hours and spin periods ranging from 33 seconds to 1 hour.
In a cataclysmic variable system, both stars are so close to each other (the whole system would match the size of our Sun) that astronomers cannot distinguish one star from the other. For studying CVs, they rely on indirect observations: measuring the variation in the brightness of the system, thereby estimating its characteristics (orbit size, period).
Dr. R. Schwarz and his colleagues [4] studied the candidate magnetic CV Paloma (also known as RX J0524+42), which has not yet been characterised. It does not fit either of the known CVs categories. The team presents both long- and short-term monitoring of this stellar system, using several European telescopes (1.2m OHP, 70 cm AIP, 1.23m Calar Alto), over a period ranging from 1995 to 2001. With this monitoring, they built the light curves and estimated the periods of the system. ROSAT observations of the system confirm that it has a strong magnetic field and thus belongs to the magnetic CVs.
From their observations, the team concludes that the faster white dwarf performs 14 spins around its own axis during 13 orbital revolutions. The weird degree of synchronization of the system presents the characteristics that makes Paloma so interesting. This bridges the gap between the two main classes of magnetic CVs: it spins much more slowly than any known intermediate polar, but is too much desynchronized to be an AM Herculis star. Paloma thus revives the old idea that both classes are evolutionarily linked together and that intermediate polars are the ancestors of the older AM Herculis stars. Theoreticians predict that Paloma is in the process of synchronization and should become a spin-locked AM Herculis star over the next 100 million years.
Journal Astronomy & Astrophysics
Magnetic Field Current Events and Magnetic Field News RSSNIST/CSM sensor could help avert pipeline failures
Researchers at the National Institute of Standards and Technology (NIST) and Colorado School of Mines (CSM) have developed a prototype sensor that quickly detects very small amounts of hydrogen accumulation in coated pipeline steel.
Young Galaxy's Magnetism Surprises Astronomers
Astronomers have made the first direct measurement of the magnetic field in a young, distant galaxy, and the result is a big surprise.
Zooming way in, technique offers close-ups of electrons, nuclei
Providing a glimpse into the infinitesimal, physicists have found a novel way of spying on some of the universe's tiniest building blocks.
First detection of magnetic field in distant galaxy produces a surprise
Using a powerful radio telescope to peer into the early universe, a team of California astronomers has obtained the first direct measurement of a nascent galaxy's magnetic field as it appeared 6.5 billion years ago.
CU-Boulder space scientists set for second spacecraft flyby of Mercury
NASA's MESSENGER spacecraft, which is toting an $8.7 million University of Colorado at Boulder instrument to measure Mercury's wispy atmosphere and blistering surface, will make its second flyby of the mysterious, rocky planet Oct. 6.
Lava flows reveal clues to magnetic field reversals
Ancient lava flows are guiding a better understanding of what generates and controls the Earth's magnetic field - and what may drive it to occasionally reverse direction.
Researchers Discover Unexpected Properties of Materials in Lowermost Mantle
Materials deep inside Earth have unexpected atomic properties that might force earth scientists to revise their models of Earth's internal processes, a team of researchers has discovered.
Superconductivity can induce magnetism
When an electrical current passes through a wire it emanates heat - a principle that's found in toasters and incandescent light bulbs.
Physicists harness effects of disorder in magnetic sensors
University of Chicago scientists have discovered how to make magnetic sensors capable of operating at the high temperatures that ceramic engines in cars and aircraft of the future will require.
Stanford's 'autonomous' helicopters teach themselves to fly
Stanford computer scientists have developed an artificial intelligence system that enables robotic helicopters to teach themselves to fly difficult stunts by watching other helicopters perform the same maneuvers.
More Magnetic Field Current Events and Magnetic Field News Articles
 | Conversations on Electric and Magnetic Fields in the Cosmos (Princeton Series in Astrophysics) by Eugene N. Parker Today's standard textbooks treat the theoretical structure of electric and magnetic fields, but their emphasis is on electromagnetic radiation and static-electric and magnetic fields. In this book, Eugene Parker provides advanced graduate students and researchers with a much-needed complement to existing texts, one that discusses the dynamic electromagnetism of the cosmos--that is, the vast... |
| Know Your Magnetic Field by William E. Gray | |
 | Magnetic Fields Near and Far: Galactic and Extragalactic Single-Dish Radio Observations of the Zeeman Effect by Timothy Robishaw According to astrophysical theory, magnetic fields should play an important role in the structure and dynamics of the interstellar medium. While astronomical observations confirm this directly, the observational record is sparse. This is because magnetic fields can only be measured via polarimetric methods, and most of these methods can only provide an indirect inference of the magnetic field... |
 | Exploitation of a Ship's Magnetic Field Signatures (Synthesis Lectures on Computational Electromagnetics) by John J. Holmes Surface ship and submarine magnetic field signatures have been exploited for over 80 years by naval influence mines, and both underwater and airborne surveillance systems. The generating mechanism of the four major shipboard sources of magnetic fields is explained, along with a detailed description of the induced and permanent ferromagnetic signature characteristics. A brief historical summary of... |
| Magnetic Fields by Andre Breton, Philippe Soupault tr David... | |
 | Biological Effects of Electric and Magnetic Fields : Beneficial and Harmful Effects (Vol 2) Recent concerns over the possible hazards of electrical and magnetic fields in the home and workplace are comprehensively addressed within this book. The chapters contain detailed research on the biological effects of electric and magnetic fields, and evidence for and against any interaction of electromagnetic fields (EMFs) and the biological systems. The two... |
 | Biological Effects of Electric and Magnetic Fields, Volume 1: Sources and Mechanisms Recent concerns over the possible hazards of electrical and magnetic fields in the home and workplace are comprehensively addressed within this book. The chapters contain detailed research on the biological effects of electric and magnetic fields, and evidence for and against any interaction of electromagnetic fields (EMFs) and biological systems. The two... |
 | Magnetic Field Therapy Handbook: Balancing Your Energy Field by Walls |
| Magnetic Field (S) by Ron Loewinsohn | |
 | The Magnetic Field of the Earth (International Geophysics Series (Reprint)) by Ronald T. Merrill Topics involved in studies of the Earth's magnetic field and its secular variation range from the intricate observations of geomagnetism, to worldwide studies of archeomagnetism and paleomagnetism, through to the complex mathematics of dynamo theory. Traditionally these different aspects of geomagnetism have been studied and presented in isolation from each other. The Magnetic Field of the Earth... |
| © 2008 BrightSurf.com |