Binary star system precisely timed with pulsar's gamma-rays

Binary star system precisely timed with pulsar's gamma-rays
In the binary system, the pulsar and its companion star orbit the the common center of mass in only 4.6 hours. The companion is heated on one side by the pulsar's radiation (magenta) and is slowly evaporated. The binary system and the companion are to scale, the pulsar has been magnified. Credit: Knispel/AEI/SDO/AIA/NASA/DSS

Pulsars are rapidly rotating compact remnants born in the explosions of massive stars. They can be observed through their lighthouse-like beams of radio waves and gamma-rays. Scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute, AEI) in Hannover, Germany, now have precisely measured the properties of a binary star system with a gamma-ray millisecond pulsar. Using new methods, the researchers analyzed archival data from the Fermi Gamma-ray Space Telescope more precisely than possible before. They discovered variations in the orbital period of the interacting binary system that can be explained by magnetic activity cycles of the companion star.

0FGL J2339.8–0530 – that is the catalog name of a celestial object which the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope identified as a source of intense gamma radiation in 2009. Observations at other wavelengths in the following years suggested a possible explanation for its nature: a in a binary system with a companion star, each orbiting their common center of mass every 4.6 hours.

Only in 2014 could the pulsar now known as "PSR J2339–0533" be identified through its pulsed radio emission. The observations at radio wavelengths are hampered through the interaction of the pulsar with its stellar partner. The pulsar's radiation heats the companion and slowly vaporizes it. This causes clouds of gas to drift through the binary system, which absorb the radio emission and temporarily make the pulsar invisible. To completely characterize the system, regular observations over several years would be required.

Clear View with Gamma-rays

However, the gamma-rays emitted by PSR J2339–0533 penetrate the gas clouds and enable observations of the pulsar. "The photon arrival times registered by the Fermi-LAT depend on the physical properties of the stars and their orbits," says Holger Pletsch, leader of an independent research group at the AEI and lead author the paper now published in The Astrophysical Journal.

In turn, a precise measurement of the binary system's physical parameters can be inferred from an analysis of the photon arrival times. "After the first radio observations we immediately had a starting point. We knew we could use archival Fermi-LAT data from the past six years to study the system at high precision", says Pletsch.

Binary star system precisely timed with pulsar's gamma-rays
The companion's magnetic activity affects the orbital period of the binary system. The changing magnetic field interacts with the plasma inside the star and deforms it. As the shape of the star varies its gravitational field also changes, which in turn affects the pulsar orbit (right). This can explain the observed orbital period variations (left). The binary system and the companion are to scale, the pulsar has been magnified. The companion's deformation is exaggerated. Credit: Knispel/AEI/SDO/AIA/NASA

Precise Measurement with New Methods

The use of new analysis algorithms was key. "Unlike previous methods that average the arrival times of many gamma-ray photons and lose time resolution as a consequence, our method is based on the arrival times of single photons", says Colin Clark, a PhD student in Pletsch's research group and co-author of the paper. "This allows us to measure the physical properties of the binary system to higher precision, especially on short time scales."

Pletsch's and Clark's results provide a very precise measurement of PSR J2339–0533, its companion, and their mutual orbits. This is the first such measurement of an interacting binary system through the gamma-ray emission of a millisecond pulsar. The scientists make full use of the Fermi-LAT time resolution, which is a few millionths of a second.

Magnetic Activity Varies the Orbital Period

The results show an unexpected variation of the orbital period. "We were surprised to discover that the orbital period slowly varies around the mean of 4.6 hours. The variations are a few thousands of a second, but compared to the measurement precision of millionths of a seconds, this is a lot", says Clark. "For the Earth's orbit this would mean that some years would be shorter or longer than others by a dozen seconds."

The most likely cause for these variations are tiny changes in the shape of the companion caused by its . Similar to our Sun the companion might be going through activity cycles. The changing magnetic field interacts with the plasma inside the star and deforms it. As the shape of the star varies its gravitational field also changes, which in turn affects the pulsar orbit. This can explain the observed orbital period variations.

"In the future simultaneous observations with optical telescopes can help us to prove the causal relationship between stellar activity and variations", says Pletsch. These observations can also improve our understanding of the . "In a sense, the Fermi-LAT observations of the allow us to peek inside the companion. This might even be used to determine the type of magnetic dynamo in the star."


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Astronomers predict fireworks from a close encounter of the stellar kind

More information: Holger J. Pletsch and Colin J. Clark 2015 ApJ 807 18. DOI: 10.1088/0004-637X/807/1/18
Journal information: Astrophysical Journal

Provided by Max Planck Society
Citation: Binary star system precisely timed with pulsar's gamma-rays (2015, July 31) retrieved 17 October 2019 from https://phys.org/news/2015-07-binary-star-precisely-pulsar-gamma-rays.html
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Jul 31, 2015
You mean... astronomers know how to do electromagnetism AS WELL AS a lot of other bits of science? I'm shocked, Shocked! Don't let the plasma cosmology people hear about this one.

Seriously though, I started grad school going for astrophysics. I took one course in it and jetted. Because astrophysicists seriously have to know *everything* in physics. Gravitation, including GR, Electromagnetism, including and especially dealing with plasmas, Thermal physics, Fluid physics... it was all just way too much for me to handle.

F the people who pollute this site with the nonsense that astrophysicists don't know what they're talking about. I dare them to spend 1 year in the shoes of an actual astrophysicist.

Jul 31, 2015
Hey shavera,

As an amateur studying the mainstream literature right along side Alfven's work, my interest in his ideas are specifically geared towards galactic formation. From what I understand, Alfven's general idea of how galaxies form is that the plasma of the galaxy itself, rotating around in an interstellar galactic magnetic field, would generate extremely powerful electric fields and potentials. This would lead to the formation of a system of filamentary currents along the plane of the galaxy, which would snake inward to the galactic center and up along its axis. Double layers could occur on these galactic scales, and the sudden release of this energy would accelerate a beam of electrons and ions along the galactic axis, radiating powerful radio waves as the electrons spiral around the field lines.

cont.

Jul 31, 2015
In essence, Birkeland currents would be generated from the rotation of the plasma in the external magnetic field, that would spiral around the arms of the galaxy inwards toward the galactic center, and ultimately produce galactic jets.

Given new observational evidence...
The ubiquitous filamentation of the plasma structuring our own galaxy: http://sci.esa.in...lky-way/
The discovery of helically shaped magnetic fields wrapping around spiral arms, funneling plasma inward towards the core: http://arxiv.org/...02.05439
The discovery of massive electric currents propagating through said galactic jets: http://arxiv.org/abs/1106.1397
The discovery that within these jets, the magnetic field lines are also helically structured, along with the said currents above most likely flow, making them field-aligned (Birkeland) currents: http://phys.org/n...ant.html

cont.

Jul 31, 2015
I think that these ideas are worth reconsidering, particularly because a model like this would also resolve the issue of galactic rotation curves without the need for dark matter (although, as I understand, dark matter is also necessary to resolve the issue of cosmic density being below Ω = 1).

My interest in revisiting this model is likewise compounded by a) the ability to create the morphology of galaxies in laboratory plasmas using similar currents, achieved simplistically by Bostick and, at least in simulation, by Peratt. Likewise, from my historical survey of astrophysics, I have noticed a repeated pattern of bias against electromagnetic phenomena having dominance in astrophysical models, beginning with Birkeland (see "The Northern Lights" by Jago) and following Alfven throughout his entire career, starting with MHD waves themselves (see: Alfven's Programme in Solar Physics, published in the IEEE).

cont.

Jul 31, 2015
His ideas, initially rejected on theoretical grounds and an lack of observational evidence, were later proven to be *generally* correct in concept by new observational evidence - particularly spacecraft measurements.

I think history is simply repeating itself now that we have new telescopes like the VLA, ALMA, and Herschel, which are bringing in new evidence that helps support his general ideas, so I'm interested in reconsidering them.

If I could ask, what were the objections to his model of galaxy formation? I understand one of them to be the lack of observable synchrotron radiation, predicted by Peratt's simulations. Are there any others? Are they observational, or theoretical? Thank you!

Aug 01, 2015
Carlo, what *mathematical* predictions does plasma cosmology make that aren't just as well answered by standard cosmology?

My broader point is that astrophysics DOES look at plasmas. On the stellar and galactic scales. They talk about them all the time. It seems remarkably disingenuous on the part of the plasma cosmology/electric universe people to pretend science doesn't.

It seems, from my reading, that plasma cosmology is an historical artifact. Kind of like caloric theories of heat. It was one idea among several, and eventually we found the description of star and galaxy formation that best explained the data we observe.

And I'll end with one important caveat. Remember above? I quit astrophysics. I don't know the whole breadth of the field. But I think it's stupid to assume those who stuck with it don't know what they're talking about, or have somehow failed to account for magnetic fields in their calculations

Aug 01, 2015
Hey shavera,

Here are some of my issues with your argument:
1) I'm not certain, hence my interest in studying both of them of the next several years. But, I feel that this also isn't the point. The fact that the present model can explain the data/measurements of what we see in space, does not mean that we necessarily have an accurate picture of the mechanism at work in, say, a galaxy. Particularly when that explanation relies on theoretical features that have never been discovered - for example, the need for dark matter to explain galactic rotation curves. If Aflven's general model explains what we see in the same manner that the standard model does, but does it *without* dark matter, and *is* supported by the new observational evidence I mentioned previously, then it may be closer to a genuine understanding of the real mechanism we're trying to figure out.

cont.

Aug 01, 2015
2) I understand that astrophysicist look at plasma, on many scales throughout the universe. And I'd agree, to suggest that they don't would be very disingenuous. But, the criticism against mainstream astrophysicist is not that they don't consider plasma phenomena or magnetism - the criticism posed by Alfven is a general misapplication of magnetohydrodynamics, mainly by treating space plasma as a perfect superconductor so that the magnetic fields we see can be treated as ideally frozen-in. Likewise, he also criticizes the lack of application of laboratory plasma phenomena - double layers, field-aligned currents, homopolar generators, etc - in our astrophysical models. You can read a general outline of his criticism by studying his Nobel Prize acceptance speech (use google).

cont.

Aug 01, 2015
Now, does his criticism hold water? *I don't know.* But, given the history that I am aware of, yes, the mainstream astrophysical community has a repeated pattern of disregarding his general ideas of incorporating these phenomena, only to have them proven correct in the future by further measurement. So, I think it would be, at least, healthy skepticism to learn about his criticisms, study the primary astrophysical literature, and *see* if his criticisms are valid.

cont.

Aug 01, 2015
3) In the end, your argument seems to boil down to an appeal to the astrophysicists' authority. Is that reasonable? On the one hand yes, they've spent many years rigorously studying several fields, and have reached a general consensus. But, on the other hand, history is history, and when it comes to electromagnetism in space, the history of the astrophysical community reveals an inability to objectively assess laboratory evidence or new astronomical observations against prevailing theory, or, to revisit old ideas. So, I'm skeptical, and I'm interested in conducting said re-examination myself. I don't think anything harmful could possibly come from studying both models against one another, keeping the necessary criticisms in mind, and seeing for myself what kind of issues come up.

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