Powerful warm winds seen blowing from a neutron star as it rips up its companion

Date:
March 2, 2022
Source:
University of Southampton
Summary:
Black holes and neutron stars are some of the most extreme
objects in the Universe, ripping up neighboring stars. But they
are messy eaters and much of they take in gets flung back into
space. Scientists have now observed a neutron star blasting out
warm and cold wind as it devoured another star. The findings shed
new light on the behavior of these stellar cannibals and how they
influence the evolution of galaxies.



FULL STORY ========================================================================== Using the most powerful telescopes on Earth and in space, a team
of astronomers has found for the first time blasts of hot, warm and
cold winds from a neutron star whilst it consumes matter from a nearby
star. The discovery provides new insight into the behaviours of some of
the most extreme objects in the universe.


========================================================================== Low-mass X-ray binaries (LMXBs) are systems containing a neutron star
or black hole. They are fuelled by material ripped from a neighbouring
star, a process known as accretion. Most accretion occurs during violent eruptions where the systems brighten dramatically. At the same time,
some of the material that spirals in is propelled back into space in
the form of disc winds and jets.

The most common signs of outflowing material from astronomical objects
are associated with "warm" gas. Despite this, only winds of "hot" or
"cold" gas have been observed in transient X-ray binaries, until now.

In this new study, a team of researchers from eleven countries, led
by the University of Southampton, studied the recent eruption of the
X-ray binary known as Swift J1858. They used a combination of telescopes, including NASA's Hubble Space Telescope (HST), the European Space Agency's XMM-Newton satellite, the European Southern Observatory Organisation's
Very Large Telescope (VLT) and the Spanish Gran Telescopio Canarias (GTC).

The results, published in the journal Nature, showed persistent signatures
of a warm wind at ultraviolet wavelengths occurring at the same time as signatures of a cold wind at optical wavelengths. This is the first time
that winds from such a system have been seen across different bands of
the electromagnetic spectrum.

Lead author Dr Noel Castro Segura, of the University of Southampton said: "Eruptions like this are rare, and each of them is unique. Normally
they are heavily obscured by interstellar dust, which makes observing
them really difficult. Swift J1858 was special, because even though it
is located on the other side of our galaxy, the obscuration was small
enough to allow for a full multiwavelength study." "Only one other
system -- the black hole X-ray binary, V404 Cyg -- has shown similar properties. However, our attempt to perform the same experiment on that
system was unsuccessful, because the eruption ended before we could get
the ground-based and space-based telescopes to observe it simultaneously,"
co- Author Dr Herna'ndez Santisteban from University of St Andrews said.



========================================================================== Swift J1858 is a newly discovered X-ray transient event that displays
extreme variability across the electromagnetic spectrum, which presented
a rare opportunity.

"All the astronomers in the field were incredibly excited, to the point
that we combined our efforts to cover the full spectrum, from radio to
X-ray using state-of-art observatories on Earth and in space," Dr Castro
Segura continued.

Co-author Nathalie Degenaar, from the University of Amsterdam added,
"Neutron stars have an immensely strong gravitational pull that allows
them to gobble up gas from other stars. The stellar cannibals are,
however, messy eaters and much of the gas that neutron stars pull
towards them is not consumed, but flung into space at high speed. This behaviour has a large impact both on the neutron star itself, and on
its immediate surroundings. In this paper we report on a new discovery
that provides key information about the messy eating patterns of these
cosmic cookie monsters." "This time we had cosmic luck on our side,
as we were able to co-ordinate ten telescopes and point them towards
the J1858, all while it was fully active.

This allows us to obtain much more information, since we can use different techniques at different wavelengths," Dr Herna'ndez Santisteban said.

Dr Degenaar added, "designing such an ambitious observing campaign --
built around the best telescopes on Earth and in space -- was a huge
challenge. So, it is incredibly exciting that all this work has paid
off and allowed us to make a key discovery that would not have been
possible otherwise." As well as discovering the different types of
winds, the team were able to study the temporal evolution of the gas
that flows out. They found that the warm wind was not affected by the
strong variations in the brightness of the system. The absence of such
a response had previously been an unconfirmed theoretical prediction
based on sophisticated simulations.



==========================================================================
"In this research we combined the unique capabilities of the HST with
the best ground-based telescopes, such as the VLT and GTC, to obtain
a complete picture of the dynamics of the gas in the system, from the near-infrared to ultraviolet wavelengths. This allowed us to unveil
for first time the true nature of these powerful outflows," Dr Castro
Segura said.

"The new insights provided by our results are key to understanding
how these objects interact with their environment. By shedding energy
and matter into the galaxy, they contribute to the formation of new
generations of stars, and to the evolution of the galaxy itself," Dr
Castro Segura concluded.

The study was funded by grants from agencies including the Science and Technology Facilities Council (STFC) and NASA among others.

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


========================================================================== Journal Reference:
1. N. Castro Segura, C. Knigge, K. S. Long, D. Altamirano, M. Armas
Padilla,
C. Bailyn, D. A. H. Buckley, D. J. K. Buisson, J. Casares,
P. Charles, J.

A. Combi, V. A. Cu'neo, N. D. Degenaar, S. del Palacio, M. Di'az
Trigo, R. Fender, P. Gandhi, M. Georganti, C. Gutie'rrez,
J. V. Hernandez Santisteban, F. Jime'nez-Ibarra, J. Matthews,
M. Me'ndez, M. Middleton, T. Mun~oz-Darias, M. O"zbey Arabacı,
M. Pahari, L. Rhodes, T. D.

Russell, S. Scaringi, J. van den Eijnden, G. Vasilopoulos, F. M.

Vincentelli, P. Wiseman. A persistent ultraviolet outflow from an
accreting neutron star binary transient. Nature, 2022; 603 (7899):
52 DOI: 10.1038/s41586-021-04324-2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220302110552.htm

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