Hi My Friends: A VUELO DE UN QUINDE EL BLOG., An extraordinary outburst produced by a black hole in a nearby galaxy has provided direct evidence for a population of old, volatile stellar black holes. The discovery, made by astronomers using NASA's Chandra X-ray Observatory, provides new insight into the nature of a mysterious class of black holes that can produce as much energy in X-rays as a million suns radiate at all wavelengths.
NASA's Chandra X-ray Observatory has discovered an extraordinary outburst by a black hole in the spiral galaxy M83, located about 15 million light years from Earth. Using Chandra, astronomers found a new ultraluminous X-ray source (ULX), objects that give off more X-rays than most "normal" binary systems in which a companion star is in orbit around a neutron star or black hole.
On the left is an optical image of M83 from the Very Large Telescope in Chile, operated by the European Southern Observatory. On the right is a composite image showing X-ray data from Chandra in pink and optical data from the Hubble Space Telescope in blue and yellow. The ULX is located near the bottom of the composite image.
In Chandra observations that spanned several years, the ULX in M83 increased in X-ray brightness by at least 3,000 times. This sudden brightening is one of the largest changes in X-rays ever seen for this type of object, which do not usually show dormant periods.
Optical images reveal a bright blue source at the position of the ULX during the X-ray outburst. Before the outburst the blue source is not seen. These results imply that the companion to the black hole in M83 is a red giant star, more than about 500 million years old, with a mass less than about four times the Sun's. According to theoretical models for the evolution of stars, the black hole should be almost as old as its companion.
Astronomers think that the bright, blue optical emission seen during the X-ray outburst must have been caused by a disk surrounding the black hole that brightened dramatically as it gained more material from the companion star.
Another highly variable ULX with an old, red star as a companion to a black hole was found recently in M31. The new ULXs in M83 and M31 provide direct evidence for a population of black holes that are much older and more volatile than those usually considered to be found in these objects.
The researchers estimate a mass range for the M83 ULX from 40 to 100 times that of the Sun. Lower masses of about 15 times the mass of the Sun are possible, but only if the ULX is producing more X-rays than predicted by standard models of how material falls onto black holes.
Evidence was also found that the black hole in this system may have formed from a star surprisingly rich in "metals", as astronomers call elements heavier than helium. The ULX is located in a region that is known, from previous observations, to be rich with metals.
Large numbers of metals increase the mass-loss rate for massive stars, decreasing their mass before they collapse. This, in turn, decreases the mass of the resulting black hole. Theoretical models suggest that with a high metal content only black holes with masses less than about 15 times that of the Sun should form. Therefore, these results may challenge these models.
This surprisingly rich "recipe" for a black hole is not the only possible explanation. It may also be that the black hole is so old that it formed at a time when heavy elements were much less abundant in M83, before seeding by later generations of supernovas. Another explanation is that the mass of the black hole is only about 15 times that of the sun.
Credits: Left image - Optical: ESO/VLT; Close-up - X-ray: NASA/CXC/Curtin University/R. Soria et al., Optical: NASA/STScI/Middlebury College/F. Winkler et al.
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NASA's Chandra Sees Remarkable Outburst From Old Black Hole;
An extraordinary outburst produced by a black hole in a nearby galaxy has provided direct evidence for a population of old, volatile stellar black holes. The discovery, made by astronomers using NASA's Chandra X-ray Observatory, provides new insight into the nature of a mysterious class of black holes that can produce as much energy in X-rays as a million suns radiate at all wavelengths.
Researchers used Chandra to discover a new ultraluminous X-ray source, or ULX. These objects give off more X-rays than most binary systems, in which a companion star orbits the remains of a collapsed star. These collapsed stars form either a dense core called a neutron star or a black hole. The extra X-ray emission suggests ULXs contain black holes that might be much more massive than the ones found elsewhere in our galaxy.
The companion stars to ULXs, when identified, are usually young, massive stars, implying their black holes are also young. The latest research, however, provides direct evidence that ULXs can contain much older black holes and some sources may have been misidentified as young ones.
The intriguing new ULX is located in M83, a spiral galaxy about 15 million light years from Earth, discovered in 2010 with Chandra. Astronomers compared this data with Chandra images from 2000 and 2001, which showed the source had increased in X-ray brightness by at least 3,000 times and has since become the brightest X-ray source in M83.
The sudden brightening of the M83 ULX is one of the largest changes in X-rays ever seen for this type of object, which do not usually show dormant periods. No sign of the ULX was found in historical X-ray images made with Einstein Observatory in 1980, ROSAT in 1994, the European Space Agency's XMM-Newton in 2003 and 2008, or NASA's Swift observatory in 2005.
"The flaring up of this ULX took us by surprise and was a sure sign we had discovered something new about the way black holes grow," said Roberto Soria of Curtin University in Australia, who led the new study. The dramatic jump in X-ray brightness, according to the researchers, likely occurred because of a sudden increase in the amount of material falling into the black hole.
In 2011, Soria and his colleagues used optical images from the Gemini Observatory and NASA's Hubble Space Telescope to discover a bright blue source at the position of the X-ray source. The object had not been previously observed in a Magellan Telescope image taken in April 2009 or a Hubble image obtained in August 2009. The lack of a blue source in the earlier images indicates the black hole's companion star is fainter, redder and has a much lower mass than most of the companions that previously have been directly linked to ULXs. The bright, blue optical emission seen in 2011 must have been caused by a dramatic accumulation of more material from the companion star.
"If the ULX only had been observed during its peak of X-ray emission in 2010, the system easily could have been mistaken for a black hole with a massive, much younger stellar companion, about 10 to 20 million years old," said co-author William Blair of Johns Hopkins University in Baltimore.
The companion to the black hole in M83 is likely a red giant star at least 500 million years old, with a mass less than four times the sun's. Theoretical models for the evolution of stars suggest the black hole should be almost as old as its companion.
Another ULX containing a volatile, old black hole recently was discovered in the Andromeda galaxy by Amanpreet Kaur, from Clemson University, and colleagues and published in the February 2012 issue of Astronomy and Astrophysics. Matthew Middleton and colleagues from the University of Durham reported more information in the March 2012 issue of the Monthly Notices of the Royal Astronomical Society. They used data from Chandra, XMM-Newton and HST to show the ULX is highly variable and its companion is an old, red star.
"With these two objects, it's becoming clear there are two classes of ULX, one containing young, persistently growing black holes and the other containing old black holes that grow erratically," said Kip Kuntz, a co-author of the new M83 paper, also of Johns Hopkins University. "We were very fortunate to observe the M83 object at just the right time to make the before and after comparison."
A paper describing these results will appear in the May 10th issue of The Astrophysical Journal.
NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.
For Chandra images, multimedia and related materials, visit:
http://www.nasa.gov/chandra For an additional interactive image, podcast, and video on the finding, visit:
http://chandra.si.edu/
Guillermo Gonzalo Sánchez Achutegui
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