NASAs Chandra X-ray Observatory has actually been gathering data on a kilonova– an effective occasion illustrated here that takes place when two neutron stars merge– associated with GW170817. Credit: X-ray data from NASA, CXC and Northwestern Univ./ A. Hajela; visual by NASA/CXC/M.
Astronomers may have spotted a “sonic boom” from a powerful blast referred to as a kilonova. This occasion– called GW170817– is a result of a merger of two neutron stars and is the very first item for which both gravitational waves and electromagnetic radiation, or light, have been detected kind Earth. Continued detections of this light by NASAs Chandra X-ray Observatory– evaluated by a cooperation that includes Penn State researchers– exposed this cosmic phenomenon.
” Chandra has actually continued to spot electromagnetic radiation from this neutron star merger nearly four years after the occasion was first detected,” stated David Radice, assistant professor of physics and of astronomy and astrophysics at Penn State and a member of the cooperation. “These observations provide crucial info about what happens after the preliminary accident, such as when and how the two merged things may form a great void.”
A kilonova happens when 2 neutron stars– some of the densest things in deep space– combine. On August 17, 2017, astronomers discovered gravitational waves from such a merger using the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) in the United States and the Virgo detector in Italy, accompanying a burst of gamma rays. Ever since, astronomers have been utilizing telescopes all over the world and in space, consisting of NASAs Chandra X-ray Observatory, to study GW170817 throughout the electro-magnetic spectrum, which includes X-rays.
” We have gone into uncharted territory here in studying the consequences of a neutron star merger,” said Aprajita Hajela of Northwestern University, who led the new research study of GW170817.
Astronomers think that after neutron stars merge, the particles creates light in the infrared and noticeable spectrum from the decay of radioactive aspects like platinum and gold formed in the particles from the merger. This burst of light is called a kilonova. When it comes to GW170817, visible light and infrared emission were found numerous hours after the gravitational waves.
The neutron star merger looked really different in X-rays. Right after the initial LIGO detection was revealed, researchers asked for that Chandra quickly pivot from its current target to GW170817. In the beginning, they did not see any X-rays from the source, however on Aug. 26, 2017, Chandra looked again and discovered a point source of X-rays.
This non-detection of X-rays rapidly followed by a detection supplies evidence for a narrow jet of high-energy particles produced by the neutron star merger. The jet is “off-axis”– that is, not pointing straight towards Earth. Researchers believe that Chandra originally saw the narrow jet from its side, and for that reason saw no X-rays instantly after the gravitational waves were found.
As time passed, the product in the jet slowed down and broadened as it knocked into surrounding product. This triggered the cone of the jet to start to expand more into Chandras direct view, and X-ray emission was detected.
Given that early 2018, the X-ray emission triggered by the jet had actually gradually been getting fainter as the jet further decreased and broadened. The research team then discovered that from March 2020 till completion of 2020 the decline stopped and the X-ray emission was roughly continuous in brightness. This was a significant indication.
” The fact that the X-rays stopped fading quickly was our best proof yet that something in addition to a jet is being discovered in X-rays in this source,” stated co-author Raffaella Margutti of the University of California at Berkeley. “A completely different source of X-rays seems needed to describe what were seeing.”
A leading description for this new source of X-rays is that the broadening debris from the merger has created a shock, like the sonic boom from a supersonic plane. An alternative description is that the X-rays come from material falling towards a black hole that formed after the neutron stars combined.
” Further research study of GW170817 could have far-reaching ramifications,” stated co-author Kate Alexander, likewise from Northwestern University. “The detection of a kilonova afterglow would suggest that the merger did not right away produce a black hole. Alternatively, this things might use astronomers a possibility to study how matter falls onto a black hole a couple of years after its birth.”
To identify between the two descriptions, astronomers will keep monitoring GW170817 in X-rays and radio waves. If the explanation includes matter falling onto a newly formed black hole, then the X-ray output ought to remain steady or decline rapidly, and no radio emission will be spotted over time.
” This observation also paves the way for more research study,” stated co-author Ashley Villar, assistant professor of astronomy and astrophysics at Penn State. “When LIGO starts its fourth observing run, we want to discover more kilonovae and really explore the diversity of these occasions, consisting of how the mass and energy signatures vary in the afterglow and how nonthermal parts like jet structure might differ. The richness of this dataset is essential in lighting up the physics driving this variety.”
To learn more on this research study see:
The neutron star merger looked very various in X-rays. At first, they did not see any X-rays from the source, however on Aug. 26, 2017, Chandra looked once again and discovered a point source of X-rays.
Scientists believe that Chandra originally viewed the narrow jet from its side, and for that reason saw no X-rays right away after the gravitational waves were discovered.
Recommendation: “The emergence of a brand-new source of X-rays from the binary neutron star merger GW170817” by A. Hajela, R. Margutti, J. S. Bright, K. D. Alexander, B. D. Metzger, V. Nedora, A. Kathirgamaraju, B. Margalit, D. Radice, E. Berger, A. MacFadyen, D. Giannios, R. Chornock, I. Heywood, L. Sironi, O. Gottlieb, D. Coppejans, T. Laskar, Y. Cendes, R. Barniol Duran, T. Eftekhari, W. Fong, A. McDowell, M. Nicholl, X. Xie, J. Zrake, S. Bernuzzi, F. S. Broekgaarden, C. D. Kilpatrick, G. Terreran, V. A. Villar, P. K. Blanchard, S. Gomez, G. Hosseinzadeh, D. J. Matthews and J. C. Rastinejad, 5 April 2021, Astrophysics > > High Energy Astrophysical Phenomena.arXiv:2104.02070.
A paper explaining these outcomes appears in the current concern of The Astrophysical Journal Letters.
NASAs Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatorys Chandra X-ray Center manages science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
NASAs Chandra X-ray Observatory has actually been collecting data on a kilonova– a powerful occasion illustrated here that occurs when 2 neutron stars merge– associated with GW170817. Given that then, astronomers have actually been utilizing telescopes all over the world and in area, including NASAs Chandra X-ray Observatory, to study GW170817 across the electro-magnetic spectrum, which includes X-rays.