Information recorded by NASA’s Chandra X-ray Observatory of a neutron star because it handed by means of a dense patch of stellar wind emanating from its huge companion star present helpful perception in regards to the construction and composition of stellar winds and in regards to the atmosphere of the neutron star itself. A paper describing the analysis, led by Penn State astronomers, seems January 15, 2019, within the journal, Month-to-month Notices of the Royal Astronomical Society.
“Stellar winds are the fast-flowing materials — composed of protons, electrons, and steel atoms — ejected from stars,” mentioned Pragati Pradhan, a postdoctoral researcher in astronomy and astrophysics at Penn State and the lead creator of the paper. “This materials enriches the star’s environment with metals, kinetic vitality, and ionizing radiation. It’s the supply materials for star formation. Till the final decade, it was thought that stellar winds have been homogenous, however these Chandra knowledge present direct proof that stellar winds are populated with dense clumps.”
The neutron star noticed is a part of a high-mass X-ray binary system — the compact, extremely dense neutron star paired with a large ‘regular’ supergiant star. Neutron stars in binary programs produce X-rays when materials from the companion star falls towards the neutron star and is accelerated to excessive velocities. On account of this acceleration, X-rays are produced that may inturn work together with the supplies of the stellar wind to supply secondary X-rays of signature energies at numerous distances from the neutron star. Impartial — uncharged — iron atoms, for instance, produce fluorescence X-rays with energies of 6.four kilo-electron volts (keV), roughly 3000 occasions the vitality of seen mild. Astronomers use spectrometers, just like the instrument on Chandra, to seize these X-rays and separate them based mostly on their vitality to be taught in regards to the compositions of stars.
“Impartial iron atoms are a extra frequent element of stars so we normally see a big peak at 6.four keV within the knowledge from our spectrometers when X-rays from most neutron stars in a high-mass X-ray binary system,” mentioned Pradhan. “After we checked out X-ray knowledge from the high-mass X-ray binary system generally known as OAO 1657-415 we noticed that this peak at 6.four keV had an uncommon function. The height had a broad extension down to six.three keV. This extension is known as a ‘Compton shoulder’ and signifies that the X-rays from impartial iron are being again scattered by dense matter surrounding the star. That is solely the second high-mass X-ray binary system the place such a function has been detected.”
The researchers additionally used the Chandra’s state-of-the-art engineering to determine a decrease restrict on the gap from the neutron star that the X-rays from impartial iron are shaped. Their spectral evaluation confirmed that impartial iron is ionized not less than 2.5 light-seconds, a distance of roughly 750 million meters or almost 500,000 miles, from the neutron star to supply X-rays.
“On this work, we see a dimming of the X-rays from the neutron star and a distinguished line from impartial iron within the X-ray spectrum — two signatures supporting the clumpy nature of stellar winds,” mentioned Pradhan. “Moreover, the detection of Compton shoulder has additionally allowed us to map the atmosphere round this neutron star. We count on to have the ability to enhance our understanding of those phenomenon with the upcoming launch of spacecrafts like Lynx and Athena, which can have improved X-ray spectral decision.”
For Pradhan’s post-doctoral work at Penn State beneath the supervision of Professor of Astronomy and Astrophysics David Burrows, Affiliate Analysis Professor of Astronomy and Astrophysics Jamie Kennea, and Analysis Professor of Astronomy and Astrophysics Abe Falcone, she is majorly concerned in writing algorithms for on-board detection of X-rays from transient astronomical occasions reminiscent of these seen from these high-mass X-ray binary programs for devices that shall be on the Athena spacecraft.
Pradhan and her crew even have a follow-up marketing campaign wanting on the identical high-mass X-ray binary with one other NASA satellite tv for pc — NuSTAR, which is able to cowl a broader spectrum of X-rays from this supply ranging in energies from ~ three to 70 keV — in Could 2019.
“We’re excited in regards to the upcoming NuSTAR commentary too,” mentioned Pradhan. “Such observations in onerous X-rays will add one other dimension to our understanding of the physics of this method and we can have a chance to estimate the magnetic discipline of the neutron star in OAO 1657-415, which is probably going 1,000,000 occasions stronger than strongest magnetic discipline on Earth.”