Spectacularly bright object in Andromeda caused by 'normal' black hole

Feb 23, 2012
A Hubble Space Telescope optical image of our nearest neighbour galaxy, Andromeda (M31), with the inset an X-ray image of the active centre made with the XMM-Newton observatory. The newly discovered ULX is highlighted. Credit: MPE

(PhysOrg.com) -- A spectacularly bright object recently spotted in one of the Milky Way's neighbouring galaxies is the result of a "normal" stellar black hole, astronomers have found.

An international team of scientists, led by Dr. Matt Middleton, of Durham University, analysed the Ultraluminous X-ray Source (ULX), which was originally discovered in the by NASA's Chandra x-ray observatory. They publish their results in the journals and .

Many ULXs are too far away for to study, but the relatively close proximity of Andromeda to the Milky Way – around 2.5 million light years – gave the team opportunity to study the phenomenon.

The researchers say their study could begin to answer the question about what causes ULXs. Some scientists believe they are caused by relatively small black holes, a few times the mass of our Sun. These black holes rapidly pull in gas and dust which forms an "accretion disc" and heats up causing the material to emit X-rays.

Other scientists say ULXs are caused by material being dragged in by an intermediate-sized black hole formed from the merger of many stellar black holes with a mass perhaps 1,000 times bigger than the Sun.

The Durham-led findings link the ULX spotted in Andromeda to a normal stellar black hole formed after a massive star exploded as a supernova.

An animated gif based on X-ray images from XMM-Newton, showing the ULX from the time it was first seen to enter outburst at the end of 2009 and its decay until it 'switched off' sometime in 2010. Credit: MPE

Dr Middleton, of Durham University's Department of Physics, said: "ULX sources are still pretty exotic.

"But our work shows that at least some are linked to the normal black holes left behind after the death of massive stars, objects that are found throughout the Universe, and the way that they drag in surrounding material.

"The ULX in Andromeda flared up because of the black hole's voracious appetite for new material."

Using data from Chandra, the XMM-Newton X-ray observatory, the Swift gamma ray observatory and the Hubble Space Telescope the research team were able to watch a sharp decline in the outburst from the ULX that took place over the next few months.

This decline had not been seen in any ULX before, but is common in stellar-mass X-ray binaries in the where a normal star is in close orbit around a black hole. Measurement of energy emissions from the ULX also allowed the team to rule out low rates of accretion that would be expected from an intermediate-mass black hole.

They concluded that the Andromeda ULX had the mass of a large star, in this case about 13 times the mass of the Sun.

Dr. Middleton said: "We would like to follow up this work by watching another outburst from the Andromeda ULX. The problem is that these are likely to happen only every few decades so we could be in for a long wait before this source erupts again."

The team hope that the ongoing monitoring of Andromeda by orbiting X-ray observatories may find other ULXs in the same galaxy, giving them another chance to test their theory.

Dr. Middleton said: "If we do manage to spot another ULX outburst in Andromeda it will be a big help in understanding the extreme behaviour of and the way they pull in matter – something of great importance in shaping the wider universe."

The research work in the UK was funded by the Science and Technology Facilities Council.

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More information: The new work will be published in "The missing link: a low mass X-ray binary in M31 seen as an ultraluminous X-ray source", Middleton, M. J. et al, Monthly Notices of the Royal Astronomical Society, in press.
A preprint can be downloaded from adsabs.harvard.edu/abs/2011arXiv1111.1188M

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1 / 5 (1) Feb 28, 2012
Andromeda galaxy is already suspected from being a product of relatively recent merging of two large galaxies (note the irregular shape of Andromeda disk), so that the newly revealed black hole may be a core of the former galaxy swallowed, which has been stripped of stars.
5 / 5 (2) Feb 28, 2012
"Andromeda galaxy is already suspected from being a product of relatively recent merging of two large galaxies (note the irregular shape of Andromeda disk)...."

Do you have a link to a paper discussing evidence of a recent (
5 / 5 (2) Feb 28, 2012
"Andromeda galaxy is already suspected from being a product of relatively recent merging of two large galaxies (note the irregular shape of Andromeda disk)...."

Do you have a link to a paper discussing evidence for a recent (~Gyr) major merger in Andromeda?

The relatively regular nature of the spiral arms in the Andromeda Galaxy argue against any recent major merger there.

More likely, the Andromeda Galaxy has recently undergone a *minor* merger with one of its retinue of dwarf galaxies, supplying the materiel to fuel the formation of young stars in the vicinity of the (pre-existing) SMBH: http://arxiv.org/...39v1.pdf

(sorry for the duplicate posts)
1 / 5 (2) Feb 29, 2012

The relatively regular nature of the spiral arms in the Andromeda Galaxy argue against any recent major merger there.

In fact, Andromeda has a somewhat concentric ring structure. This is further support for LaViolette's inside/out growth model. Interesting to note the contorted models needed to support the accretion explanation. More likely, and simply, these core stars simply erupted from periodic instability from growth from within.

And now there are more sources, likely ejected from the core and growing while on their journey, periodically erupting into cyclic view.


And it seems the accretion model has some severe problems for the more massive stars.

5 / 5 (2) Feb 29, 2012
again tuxford you seem to have forgotten to include the important points of laviolettes theory that their is a secret code hidden in the location of stars warning us of an impending galactic superwave hidden their during the last ice age to be rediscovered by laviolette now as we approach 2012 and the disaster is imminent. the code laviolette found also somehow reveals how matter is created from the centers of stars/galaxies. the worldwide scientific community is just engaging in a conspiracy to supress laviolettes great discovery. Thats right, he says he found a code hidden in the stars of the night sky and astrology/studying the zodiac should be a mainstream scientific field and philosophy should be re-united with science. you always forget that part tuxford.