Featured Research

from universities, journals, and other organizations

Middleweight Black Hole: Swift, XMM-Newton Satellites Tune Into X-ray Source

Date:
November 10, 2009
Source:
NASA/Goddard Space Flight Center
Summary:
While astronomers have studied lightweight and heavyweight black holes for decades, the evidence for black holes with intermediate masses has been much harder to come by. Now, astronomers find that an X-ray source in galaxy NGC 5408 represents one of the best cases for a middleweight black hole to date.

Swift X-ray observations of galaxy NGC 5408 indicate its ultraluminous X-ray source undergoes periodic changes every 115.5 days. This cycle, astronomers suspect, is linked to the orbit of a donor star around a middleweight black hole, as shown in this artist's view.
Credit: NASA

While astronomers have studied lightweight and heavyweight black holes for decades, the evidence for black holes with intermediate masses has been much harder to come by. Now, astronomers at NASA's Goddard Space Flight Center in Greenbelt, Md., find that an X-ray source in galaxy NGC 5408 represents one of the best cases for a middleweight black hole to date.

"Intermediate-mass black holes contain between 100 and 10,000 times the sun's mass," explained Tod Strohmayer, an astrophysicist at Goddard. "We observe the heavyweight black holes in the centers of galaxies and the lightweight ones orbiting stars in our own galaxy. But finding the 'tweeners' remains a challenge."

Several nearby galaxies contain brilliant objects known as ultraluminous X-ray sources (ULXs). They appear to emit more energy than any known process powered by stars but less energy than the centers of active galaxies, which are known to contain million-solar-mass black holes.

"ULXs are good candidates for intermediate-mass black holes, and the one in galaxy NGC 5408 is especially interesting," said Richard Mushotzky, an astrophysicist at the University of Maryland, College Park. The galaxy lies 15.8 million light-years away in the constellation Centaurus.

Using the European Space Agency's orbiting XMM-Newton observatory, Strohmayer and Mushotzky studied the source -- known as NGC 5408 X-1 -- in 2006 and 2008.

XMM-Newton detected what the astronomers call "quasi-periodic oscillations," a nearly regular "flickering" caused by the pile-up of hot gas deep within the accretion disk that forms around a massive object. The rate of this flickering was about 100 times slower than that seen from stellar-mass black holes. Yet, in X-rays, NGC 5408 X-1 outshines these systems by about the same factor.

Based on the timing of the oscillations and other characteristics of the emission, Strohmayer and Mushotzky conclude that NGC 5408 X-1 contains between 1,000 and 9,000 solar masses. This study appears in the October 1 issue of The Astrophysical Journal.

"For this mass range, a black hole's event horizon -- the part beyond which we cannot see -- is between 3,800 and 34,000 miles across, or less than half of Earth's diameter to about four times its size," said Strohmayer.

If NGC 5408 X-1 is indeed actively gobbling gas to fuel its prodigious X-ray emission, the material likely flows to the black hole from an orbiting star. This is typical for stellar-mass black holes in our galaxy.

Strohmayer next enlisted the help of NASA's Swift satellite to search for subtle variations of X-rays that would signal the orbit of NGC 5408 X-1's donor star. "Swift uniquely provides both the X-ray imaging sensitivity and the scheduling flexibility to enable a search like this," he added. Beginning in April 2008, Swift began turning its X-Ray Telescope toward NGC 5408 X-1 a couple of times a week as part of an on-going campaign.

Swift detects a slight rise and fall of X-rays every 115.5 days. "If this is indeed the orbital period of a stellar companion," Strohmayer said, "then it's likely a giant or supergiant star between three and five times the sun's mass." This study has been accepted for publication in a future issue of The Astrophysical Journal.

The Swift observations cover only about four orbital cycles, so continued observation is needed to confirm the orbital nature of the X-ray modulation.

"Astronomers have been studying NGC 5408 X-1 for a long time because it is one of the best candidates for an intermediate-mass black hole," adds Philip Kaaret at the University of Iowa, who has studied the object at radio wavelengths but is unaffiliated with either study. "These new results probe what is happening close to the black hole and add strong evidence that it is unusually massive."


Story Source:

The above story is based on materials provided by NASA/Goddard Space Flight Center. Note: Materials may be edited for content and length.


Cite This Page:

NASA/Goddard Space Flight Center. "Middleweight Black Hole: Swift, XMM-Newton Satellites Tune Into X-ray Source." ScienceDaily. ScienceDaily, 10 November 2009. <www.sciencedaily.com/releases/2009/11/091110105404.htm>.
NASA/Goddard Space Flight Center. (2009, November 10). Middleweight Black Hole: Swift, XMM-Newton Satellites Tune Into X-ray Source. ScienceDaily. Retrieved April 17, 2014 from www.sciencedaily.com/releases/2009/11/091110105404.htm
NASA/Goddard Space Flight Center. "Middleweight Black Hole: Swift, XMM-Newton Satellites Tune Into X-ray Source." ScienceDaily. www.sciencedaily.com/releases/2009/11/091110105404.htm (accessed April 17, 2014).

Share This



More Space & Time News

Thursday, April 17, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

New Baby Moon 'Peggy' Spotted In Saturn's Rings

New Baby Moon 'Peggy' Spotted In Saturn's Rings

Newsy (Apr. 15, 2014) A bump in the rings could be a half-mile-wide miniature moon. It was found by accident in Cassini probe images. Video provided by Newsy
Powered by NewsLook.com
Americas Glimpse Total Lunar Eclipse

Americas Glimpse Total Lunar Eclipse

AFP (Apr. 15, 2014) A total lunar eclipse, the first since December 2011, took place early Tuesday morning with the Americas getting the best glimpse. Duration: 1:19 Video provided by AFP
Powered by NewsLook.com
NASA Showcases Lunar Eclipse

NASA Showcases Lunar Eclipse

AP (Apr. 15, 2014) Star gazers in parts of North and South America got a rare treat early Tuesday morning - a total eclipse of the moon. (April 15) Video provided by AP
Powered by NewsLook.com
Spacecrafts Could Use Urine As Fuel Source

Spacecrafts Could Use Urine As Fuel Source

Newsy (Apr. 15, 2014) New research says the urea from urine could be recycled for fuel. Urea is filtered out of wastewater when making drinking water. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins