Ultra-bright X-ray source awakens near a galaxy not so far away

Date:
June 3, 2020
Source:
Royal Astronomical Society
Summary:
A new ultra-bright source of X-rays has awakened in between
our galactic neighbors the Magellanic Clouds, after a 26-year
slumber. This is the second-closest such object known to date,
with a brightness greater than a million Suns.



FULL STORY ==========================================================================
A new ultra-bright source of X-rays has awakened in between our galactic neighbours the Magellanic Clouds, after a 26-year slumber. This is the
second- closest such object known to date, with a brightness greater
than a million Suns. The discovery is published in the journal Monthly
Notices of the Royal Astronomical Society.


==========================================================================
The object, known as RX J0209.6-7427, was first detected during a 6-month
long outburst in 1993. Though it was initially identified as a Be-type
X-ray binary, its true nature remained a mystery as it lingered in a
dormant state for the next 26 years, only flaring up again in November
last year.

Now, a team of Indian scientists have used AstroSat, India's first
dedicated space observatory, to reveal the extreme nature of the
source, and have detected broad-energy X-ray pulsations in the object
for the first time. This classifies it as a type of object known as an ultra-luminous X-ray pulsar (ULXP).

The pulsar is located in the Magellanic Bridge, a stream of gas and stars linking the Magellanic Clouds. These are two of our nearest galactic companions, and some of the most distant objects visible to the naked
eye. The new X-ray source is the second-closest ULXP known to date,
after a 2018 discovery in our own Milky Way galaxy, and is only the
eighth such object ever discovered.

Ultra-luminous X-ray sources are observable as single points in the sky,
but with brightnesses comparable to entire galaxies. "The conventional
theory is that in order to shine so brightly, ULXPs must be glowing
accretion discs around black holes," said Amar Deo Chandra, lead author
on the new study.

"However, recent discoveries of pulsations in these objects suggest that
they may in fact have neutron stars at their heart." A neutron star
is the remnant of a dead star which contains as much matter as our Sun,
but is compressed into a tiny radius of as little as 10km -- the size of
a small city. The neutron star in this object is thought to be spinning
as rapidly as 100 times per second, and emits pulses of energetic X-rays
from its magnetic poles, leading to the new 'X-ray pulsar' classification.

The group of astronomers, from IISER Kolkata, IUCAA Pune and the Center
for Excellence in Basic Sciences (UM-DAE CEBS) Mumbai, have also found
that the pulsar may even be speeding up, setting off bright X-ray
'fireworks'. This is thought to happen when the neutron star captures
material from a companion star, injecting energy into the system and
speeding up the rotation.

The scarcity of similar sources makes detecting and studying new ULXPs essential for X-ray astronomers seeking to understand the Universe.

"This is only the eighth ULXP detected so far, and the first one near the Magellanic Clouds," Chandra adds. "It raises the interesting possibility
that a significant fraction of ultra-luminous X-ray sources may really
be neutron stars accreting at super Eddington rates, rather than black
holes as previously thought."

========================================================================== Story Source: Materials provided by Royal_Astronomical_Society. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Manojendu Choudhury, P C Agrawal, Jayashree Roy, Amar Deo
Chandra. Study
of recent outburst in the Be/X-ray binary RX J0209.6-7427 with
AstroSat: a new ultraluminous X-ray pulsar in the Magellanic
Bridge? Monthly Notices of the Royal Astronomical Society, 2020;
495 (3): 2664 DOI: 10.1093/mnras/staa1041 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200603120534.htm https://www.sciencedaily.com/releases/2020/06/200603120534.htm

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