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Artist’s impression of the X-ray pulsar GX 301-2 passing through a stream of gas from its giant companion star. Credit: NASA’s Goddard Space Flight Center Conceptual Image Lab.
Keeping time with spinning neutron stars
Keeping time with spinning neutron stars
X-ray pulsars are neutron stars that pull gas from a companion star and spin like cosmic lighthouses, sending out a pulse of X-rays with every turn. Daksha will keep watch on the brightest of them all the time, tracking how their spin speeds up and slows down as they feed.
For astronomers: technical details
For astronomers: technical details
Using barycentred, time-tagged photons combined across detector faces, Daksha’s MEPs can detect pulsations from accreting pulsars with 20–50 keV flux above ~2.6×10⁻¹⁰ (3.1×10⁻¹⁰) erg cm⁻² s⁻¹ at 3σ (5σ) in 2.5 days, with Earth occultation helping to separate sources. Expect continuous monitoring of ~15 persistent pulsars, ~6 transient pulsars in outburst per year, and ~2 new transient pulsars per year. See Bhalerao et al. 2024, Science with the Daksha High Energy Transients Mission (Experimental Astronomy 57, 23), section “X-ray pulsars”. All Daksha papers are listed on our Publications page.
What is an X-ray pulsar?
What is an X-ray pulsar?
Some neutron stars live in pairs with an ordinary star, and pull gas off their companion. The neutron star’s strong magnetic field funnels this gas onto its magnetic poles, where it crashes down, heats to millions of degrees and glows in X-rays. As the neutron star spins — anywhere from several times a second to once every ten minutes or more — these hot spots sweep past us like the beam of a lighthouse, and we see regular pulses of X-rays.
Why their spin matters
Why their spin matters
Gas falling onto a pulsar gives it a push, speeding up or slowing down its spin. By timing the pulses precisely, astronomers can measure this push and learn how the gas flows — whether it arrives in a smooth disc or in clumps from the companion’s wind. Some pulsars flare up for weeks at a time, spinning up dramatically during each outburst. Pulsars can also “glitch” — suddenly change their spin — giving clues to what goes on inside a neutron star.
What Daksha will do
What Daksha will do
Because Daksha sees most of the sky at once, it can monitor all the brightest X-ray pulsars at the same time, every day, instead of pointing at them one by one. Each X-ray is timed to better than a thousandth of a second, so the pulses can be picked out even though Daksha’s detectors don’t form images. Daksha is expected to track about 15 pulsars continuously, follow several more as they flare up each year, and discover new ones.
Support Daksha
Support Daksha
If you would like to see Daksha fly, please take a minute to fill in our short support form. Every response helps show the scientific community’s interest in the mission.
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