Anne’s Picture of the Day: SXP 1062

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November 13, 2012

SXP 1062, a pulsar in a supernova remnant

Image Credit: X-ray: NASA/CXC/Univ.Potsdam/L.Oskinova et al & ESA/XMM-Newton; Optical: AURA/NOAO/CTIO/Univ.Potsdam/L.Oskinova et al

SXP 1062 is a young pulsar within a supernova remnant of some 744 light years across, located in the Wing of the Small Magellanic Cloud (a small satellite galaxy to our Milky Way), about 180,000 light-years away in the southern constellation of Tucana.

The Wing of the Small Magellanic Cloud is a peripheral region of this small galaxy. The Wing is part of the tidal feature that connects the Small Magellanic Cloud to its neighbour, the Large Magellanic Cloud.

The bubble-shaped feature on the right-hand side of the image is the supernova remnant that encloses the pulsar (the bright white source in the center). The diffuse blue glow at the center represents X-ray emission from both the pulsar and the hot gas that fills the remnant of the supernova.

Optical images show that SXP 1062 is part of a binary system, and that it accretes mass from this stellar companion, a massive, hot, blue star. On the left side in this image (seen in optical light) is a spectacular formation of gas and dust in a star-forming region. (Can someone tell me its name?)

A supernova occurs when a star explodes at the end of its life. After some supernova explosions, when the star collapses and becomes so dense that protons and electrons squish together to form neutrons, there remains a small, ultra-dense neutron star. Rapidly rotating, highly magnetized neutron stars are called pulsars. (After other supernova explosions, a black hole may be left behind.) The explosion throws a large, roughly spherical cloud of dust and hot gas into space surrounding the neutron star (or black hole). When this slams into the existing interstellar medium, it heats up so much it glows in X-rays.

Since supernova remnants shine only for a few tens of thousands of years before dispersing into the interstellar medium, not many pulsars have been detected while still embedded in their expanding shell. This is the first clear example of such a pair in the Small Magellanic Cloud.

SXP 1062 is rotating unusually slowly — about once every 18 minutes, in an extremely long period — 1,062 seconds. (In contrast, some pulsars are found to revolve multiple times per second, including most newly born pulsars.) This relatively leisurely pace of SXP 1062 makes it one of the slowest rotating pulsars in the Small Magellanic Cloud

Since pulsars slow down as they age, SXP 1062′s sluggish rotation seems to imply an advanced age, in contrast to the fairly young age of the supernova remnant (between 10,000 and 40,000 years old) that surrounds it. This means that the pulsar is very young, from an astronomical perspective, since it was presumably formed in the same explosion that produced the supernova remnant. Therefore, assuming that it was born with rapid spin, it is a mystery why SXP 1062 has been able to slow down by so much, so quickly.

This false-colour image combines the X-ray view, based on data from XMM-Newton (blue), with optical data from NOAO’s Cerro Tololo Inter-American Observatory (CTIO), obtained using two special filters that reveal the glow of oxygen (green) and hydrogen (red).

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