Fastest eclipsing binary, a valuable target for gravitational wave studies

Found: Fastest eclipsing binary, a valuable target for gravitational wave studies
The 2.1-meter telescope at Kitt Peak National Observatory, where KPED is installed. Credit: P. Marenfeld & NOAO/AURA/NSF

Observations made with a new instrument developed for use at the 2.1-meter (84-inch) telescope at the National Science Foundation's Kitt Peak National Observatory have led to the discovery of the fastest eclipsing white dwarf binary yet known. Clocking in with an orbital period of only 6.91 minutes, the rapidly orbiting stars are expected to be one of the strongest sources of gravitational waves detectable with LISA, the future space-based gravitational wave detector.

The Dense "Afterlives" of Stars

After expanding into a red giant at the end of its life, a star like the Sun will eventually evolve into a dense white dwarf, an object with a mass like that of the Sun squashed down to a size comparable to Earth. Similarly, as evolve, they can engulf their companion in the red giant phase and spiral close together, eventually leaving behind a close white dwarf binary. White dwarf binaries with very tight orbits are expected to be strong sources of gravitational wave radiation. Although anticipated to be relatively common, such systems have proven elusive, with only a few identified to date.

Record-setting White Dwarf Binary

A new survey of the night sky, currently underway at Palomar Observatory and Kitt Peak National Observatory, is changing this situation.

Each night, Caltech's Zwicky Transient Facility (ZTF), a survey that uses the 48-inch telescope at Palomar Observatory, scans the sky for objects that move, blink, or otherwise vary in brightness. Promising candidates are followed up with a new instrument, the Kitt Peak 84-inch Electron Multiplying Demonstrator (KPED), at the Kitt Peak 2.1-meter telescope to identify short period eclipsing binaries. KPED is designed to measure with speed and sensitivity the changing brightness of celestial sources.

This approach has led to the discovery of ZTF J1539+5027 (or J1539 for short), a white dwarf eclipsing binary with the shortest period known to date, a mere 6.91 minutes. The stars orbit so close together that the entire system could fit within the diameter of the planet Saturn.

"As the dimmer star passes in front of the brighter one, it blocks most of the light, resulting in the seven-minute blinking pattern we see in the ZTF data," explains Caltech graduate student Kevin Burdge, lead author of the paper reporting the discovery, which appears in the today's issue of the journal Nature.

Artist's animation depicting the eclipsing binary ZTF J1530+5027, which is comprised of two extremely dense objects (white dwarfs) that orbit each other roughly every seven minutes. One second of time in the animation represents two minutes of real time. The smaller white dwarf is slightly larger than Earth and is the more massive of the two, with about 60% the mass of the sun. Its companion is larger but less massive, with only about 20% the mass of the sun. The orbital separation of these objects is shrinking by about 26 centimeters per day due to the emission of gravitational waves, depicted in green near the end of the movie. Credit: Caltech/IPAC

A Strong Source of Gravitational Waves

Closely orbiting white dwarfs are predicted to spiral together closer and faster, as the system loses energy by emitting gravitational waves. J1539's orbit is so tight that its is predicted to become measurably shorter after only a few years. Burdge's team was able to confirm the prediction from general relativity of a shrinking orbit, by comparing their new results with archival data acquired over the past ten years.

J1539 is a rare gem. It is one of only a few known sources of gravitational waves—ripples in space and time—that will be detected by the future European space mission LISA (Laser Interferometer Space Antenna), which is expected to launch in 2034. LISA, in which NASA plays a role, will be similar to the National Science Foundation's ground-based LIGO (Laser Interferometer Gravitational-wave Observatory), which made history in 2015 by making the first direct detection of gravitational waves from a pair of colliding black holes. LISA will detect gravitational waves from space at . J1539 is well matched to LISA; the 4.8 mHz gravitational wave frequency of J1539 is close to the peak of LISA's sensitivity.

Discoveries Continue for Historic Telescope

Kitt Peak's 2.1-meter telescope, the second major telescope to be constructed at the site, has been in continuous operation since 1964. Its history includes many important discoveries in astrophysics, such as the Lyman-alpha forest in quasar spectra, the first gravitational lens by a galaxy, the first pulsating white dwarf, and the first comprehensive study of the binary frequency of stars like the Sun. The latest result continues its venerable track record.

Lori Allen, Director of Kitt Peak National Observatory and Acting Director of NOAO says, "We're thrilled to see that our 2.1-meter telescope, now more than 50 years old, remains a powerful platform for discovery."

"These wonderful observations are further proof that cutting-edge science can be done on modest-sized telescopes like the 2.1-meter in the modern era," adds Chris Davis, NSF Program Officer for NOAO.

More Thrills Ahead!

As remarkable as it is, J1539 was discovered with only a small portion of the data expected from ZTF. It was found in the ZTF team's initial analysis of 10 million sources, whereas the project will eventually study more than a billion stars.

"Only months after coming online, ZTF astronomers have detected white dwarfs orbiting each other at a record pace," says NSF Assistant Director for Mathematical and Physical Sciences, Anne Kinney. "It's a discovery that will greatly improve our understanding of these systems, and it's a taste of surprises yet to come."


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More information: General relativistic orbital decay in a seven-minute-orbital-period eclipsing binary system, Nature (2019). DOI: 10.1038/s41586-019-1403-0
Journal information: Nature

Provided by Association of Universities for Research in Astronomy (AURA)
Citation: Fastest eclipsing binary, a valuable target for gravitational wave studies (2019, July 24) retrieved 15 September 2019 from https://phys.org/news/2019-07-fastest-eclipsing-binary-valuable-gravitational.html
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Jul 24, 2019
Neither here, nor in the abstract, is the distance away given. Seems odd. Usually they give that; plus the direction, at least in the constellation ball-park.
It's 7,500 miles, if anyone else is interested

Jul 24, 2019
It is odd because it is a conspiracy among the worlds scientists to convert the worlds population to Communism and the worship of Lucifer.

Just ask this U.S. Republican senator.

https://www.youtu...1kuZ31bo

Jul 24, 2019
Being exactly centered in the plane of a pair of white dwarf's orbit is almost as rare as being in the exact center of a quasar jet.
One in a trillion? No sweat, universe got lots more where that came from.

Jul 25, 2019
I suppose that the energy given off by the 2 Stars as they orbit each other, is the source of the gravitational waves, and not its effect on the Space surrounding the binary. The energy waves would move out through the Vacuum in a 360 degree pattern of flow - some of it headed in our direction. How far away are they from us here?

Jul 25, 2019
I suppose that the energy given off by the 2 Stars as they orbit each other, is the source of the gravitational waves, and not its effect on the Space surrounding the binary.
Surveillance_Egg_Unit

You obviously don't know the first thing about general relativity. Best not to form opinions about things you know nothing about.

Jul 25, 2019
Let's hope LISA will have more than "a few" gravity wave sources to look at by the time she goes up.

Neither here, nor in the abstract, is the distance away given. Seems odd.


Yes, I hoped they would give a ball park outside of "within the Milky Way", which apparently suffice for LISA. But it is a survey of transients, likely a happenstance microlensing event that for some reason or other did not give target distance.


Jul 25, 2019
It is odd because it is a conspiracy among the worlds scientists


Whether or not you are joking, this is posted after a similar conspiracy theory targeting "Americans". Personally blocked by me for your inane trolling.

Jul 31, 2019
Let's hope LISA will have more than "a few" gravity wave sources to look at by the time she goes up.

Neither here, nor in the abstract, is the distance away given. Seems odd.


Yes, I hoped they would give a ball park outside of "within the Milky Way", which apparently suffice for LISA. But it is a survey of transients, likely a happenstance microlensing event that for some reason or other did not give target distance.



Torborg it is 7800 light years from earth.

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