Data suggest black holes swallow stellar debris in bursts

March 15, 2017 by Jennifer Chu
In this artist's rendering, a thick accretion disk has formed around a supermassive black hole following the tidal disruption of a star that wandered too close. Stellar debris has fallen toward the black hole and collected into a thick chaotic disk of hot gas. Flashes of X-ray light near the center of the disk result in light echoes that allow astronomers to map the structure of the funnel-like flow, revealing for the first time strong gravity effects around a normally quiescent black hole. Credit: NASA/Swift/Aurore Simonnet, Sonoma State University

In the center of a distant galaxy, almost 300 million light years from Earth, scientists have discovered a supermassive black hole that is "choking" on a sudden influx of stellar debris.

In a paper published today in Astrophysical Journal Letters, researchers from MIT, NASA's Goddard Space Flight Center, and elsewhere report on a "tidal disruption flare"—a dramatic burst of electromagnetic activity that occurs when a black hole obliterates a nearby star. The flare was first discovered on Nov. 11, 2014, and scientists have since trained a variety of telescopes on the event to learn more about how black holes grow and evolve.

The MIT-led team looked through data collected by two different telescopes and identified a curious pattern in the energy emitted by the flare: As the obliterated star's dust fell into the black hole, the researchers observed small fluctuations in the optical and ultraviolet (UV) bands of the electromagnetic spectrum. This very same pattern repeated itself 32 days later, this time in the X-ray band.

The researchers used simulations of the event performed by others to infer that such energy "echoes" were produced from the following scenario: As a star migrated close to the black hole, it was quickly ripped apart by the black hole's gravitational energy. The resulting stellar debris, swirling ever closer to the black hole, collided with itself, giving off bursts of optical and UV light at the collision sites. As it was pulled further in, the colliding debris heated up, producing X-ray flares, in the same pattern as the optical bursts, just before the debris fell into the black hole.

"In essence, this black hole has not had much to feed on for a while, and suddenly along comes an unlucky star full of matter," says Dheeraj Pasham, the paper's first author and a postdoc in MIT's Kavli Institute for Astrophysics and Space Research. "What we're seeing is, this stellar material is not just continuously being fed onto the black hole, but it's interacting with itself—stopping and going, stopping and going. This is telling us that the black hole is 'choking' on this sudden supply of stellar debris."

Pasham's co-authors include MIT Kavli postdoc Aleksander Sadowski and researchers from NASA's Goddard Space Flight Center, the University of Maryland, the Harvard-Smithsonian Center for Astrophysics, Columbia University, and Johns Hopkins University.

A "lucky" sighting

Pasham says tidal disruption flares are a potential window into the universe's many "hidden" black holes, which are not actively accreting, or feeding on material.

"Almost every massive galaxy contains a supermassive black hole," Pasham says. "But we won't know about them if they're sitting around doing nothing, unless there's an event like a tidal disruption flare."

Such flares occur when a star, migrating close to a black hole, gets pulled apart from the black hole's immense gravitational energy. This stellar obliteration can give off incredible bursts of energy all along the electromagnetic spectrum, from the radio band, through the optical and UV wavelengths, and on through the X-ray and high-energy gamma ray bands. As extreme as they are, tidal disruption flares are difficult to observe, as they happen infrequently.

This animation illustrates how debris from a tidally disrupted star collides with itself, creating shock waves that emit ultraviolet and optical light far from the black hole. According to Swift observations of ASASSN-14li, these clumps took about a month to fall back to the black hole, where they produced changes in the X-ray emission that correlated with the earlier UV and optical changes. Credit: NASA's Goddard Space Flight Center

"You'd have to stare at one galaxy for roughly 10,000 to 100,000 years to see a star getting disrupted by the black hole at the center," Pasham says.

Nevertheless, on Nov. 11, 2014, a global network of robotic telescopes named ASASSN (All Sky Automated Survey for SuperNovae) picked up signals of a possible tidal disruption flare from a galaxy 300 million light years away. Scientists quickly focused other telescopes on the event, including the X-ray telescope aboard NASA's Swift satellite, an orbiting spacecraft that scans the sky for bursts of extremely high energy.

"Only recently have telescopes started 'talking' to each other, and for this particular event we were lucky because a lot of people were ready for it," Pasham says. "It just resulted in a lot of data."

A light-on collision

With access to these data, Pasham and his colleagues wanted to solve a longstanding mystery: Where did a flare's bursts of light first arise? Using models of black hole dynamics, scientists have been able to estimate that as a black hole rips a star apart, the resulting tidal disruption flare can produce X-ray emissions very close to the black hole. But it's been difficult to pinpoint the origin of optical and UV emissions. Doing so would be an added step toward understanding what happens when a star gets disrupted.

"Supermassive black holes and their host galaxies grow in-situ," Pasham says. "Knowing exactly what happens in tidal disruption flares could help us understand this black hole and galaxy coevolution process."

The researchers studied the first 270 days following the detection of the tidal disruption flare, named ASASSN-14li. In particular, they analyzed X-ray and optical/UV data taken by the Swift satellite and the Las Cumbres Observatory Global

Telescope. They identified fluctuations, or bursts, in the X-ray band—two broad peaks (one around day 50, and the other around day 110) followed by a short dip around day 80. They identified this very same pattern in the optical/UV data some 32 days earlier.

To explain these emission "echoes," the team ran simulations of a tidal disruption flare produced from a black hole obliterating a star. The researchers modeled the resulting accretion disc—an elliptical disc of stellar debris swirling around the black hole—along with its probable speed, radius, and rate of infall, or speed at which material falls onto the black hole.

From simulations run by others, the researchers conclude that the optical and UV bursts likely originated from the collision of stellar debris on the outer perimeter of the black hole. As this colliding material circles closer into the black hole, it heats up, eventually giving off X-ray emissions, which can lag behind the optical emissions, similar to what the scientists observed in the data.

"For supermassive steadily accreting, you wouldn't expect this choking to happen," Pasham says. "The material around the black hole would be slowly rotating and losing some energy with each circular orbit. But that's not what's happening here. Because you have a lot of material falling onto the black hole, it's interacting with itself, falling in again, and interacting again. If there are more events in the future, maybe we can see if this is what happens for other flares."

Explore further: Researchers discover a black hole feeding frenzy that breaks records

More information: Dheeraj R. Pasham et al. Optical/UV-to-X-Ray Echoes from the Tidal Disruption Flare ASASSN-14li, The Astrophysical Journal (2017). DOI: 10.3847/2041-8213/aa6003 , iopscience.iop.org/article/10. … 847/2041-8213/aa6003

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Tuxford
1 / 5 (7) Mar 15, 2017
"Almost every massive galaxy contains a supermassive black hole," Pasham says.

Why? Doesn't the accepting merger maniac even wonder?
"Supermassive black holes and their host galaxies grow in-situ," Pasham says.

Chicken and the egg problem. But the merger maniac insists it was the chicken first (and keeps on looking for a non-existent answer to his confusion), rather than the central egg. Nonsense. Even biologists know better. They could teach the astrophysicists a thing or two.
SiaoX
1 / 5 (3) Mar 15, 2017
Actually the black holes are much larger and more prominent at the case of young galaxies, than at the case of the older ones. Our central black hole inside the Milky Way (which is at least 12 GYrs old) is quite tiny and inconspicuous. This would already provide some clue, what's actually going on - if only the theorists wouldn't believe so firmly, that the black holes cannot evaporate at all.
Benni
1 / 5 (8) Mar 15, 2017
Actually the black holes are much larger and more prominent at the case of young galaxies, than at the case of the older ones. Our central black hole inside the Milky Way (which is at least 12 GYrs old) is quite tiny and inconspicuous. This would already provide some clue, what's actually going on - if only the theorists wouldn't believe so firmly, that the black holes cannot evaporate at all.


.........you know this because you have Schneibo's pictures?
antialias_physorg
4.4 / 5 (8) Mar 15, 2017
Actually the black holes are much larger and more prominent at the case of young galaxies,

And you get this 'actually' statistic...from where exactly? Link?
cantdrive85
1.5 / 5 (8) Mar 15, 2017
Study after study would suggest astrophysicists ignorance of real plasma physics would lead them to the fanciful conjecture they spout about as above.
wduckss
1 / 5 (8) Mar 15, 2017
Such flares occur when a star, migrating close to a black hole. "
from article

"This is the official viewpoint: the size of a super-massive black hole is ~ 0.001 to 400 AU https://en.wikipe...perties.
The central diameter of our galaxy and the equatorial area is 40,000 light-years and those from galaxy pole to the other ones, 30,000 light-years
(Http://www.astrod...y.html).
Even if there was a maximal super-massive black hole in the center of our galaxy, it would be at least 15,000 light-years away from the surface area of the galaxy and its polar regions and 20,000 light-years in the equatorial area . Such a black hole would be covered with a layer of matter, from 15,000 to 20,000 light-years thick. "
from http://www.svemir...ack-hole
RNP
4.5 / 5 (8) Mar 15, 2017
@SiaoX, antialias_physorg
The strongest trend is for BH mass to correlate with the mass of the bulge/galaxy harbouring it. Given that the most massive galaxies also tend to be the oldest, there is a trend for the oldest galaxies to harbor the biggest BH.

Google "black hole mass correlations" to see what I mean, or see a paper that goes into a lot more detail; https://arxiv.org...5899.pdf

Note that the paper I link uses velocity dispersion (sigma) as an observable proxy for galaxy mass.
SlartiBartfast
3.7 / 5 (6) Mar 15, 2017
Study after study would suggest astrophysicists ignorance of real plasma physics would lead them to the fanciful conjecture they spout about as above.


I did a study, and the results are in: you don't know how to use apostrophes!
SlartiBartfast
4.3 / 5 (12) Mar 15, 2017
Tuxford, wduckss, cantdrive85, (and SiaoX to a lesser extent). There's nothing like an article about black holes to bring together all the loons :-/
SiaoX
1 / 5 (2) Mar 15, 2017
BH mass to correlate with the mass of the bulge/galaxy harbouring it
But how the BH mass correlates with age of galaxy and how the activity of BH correlated with age of galaxy? Most of active black holes and AGNs exist in the older (i.e. more distant) areas of universe. The oldest galaxies (hydrogen rich galaxies of low metallicity) harbor only small black holes, because these galaxies are typically dwarf galaxies.
RNP
4.5 / 5 (8) Mar 15, 2017
@SaioX
I suggest you try to find references for your claims, most of which are wrong.

1) We see more AGN at large distances because there is more volume per unit distance at large distances.
3) More distant parts of the Universe are younger, not older.
2) Dwarf galaxies are on average younger than more massive galaxies.
SiaoX
1 / 5 (4) Mar 15, 2017
we see more AGN at large distances because there is more volume per unit distance at large distances
It should follow cubic law after then - but the distribution of AGN is completely different. Every great theory is killed with many small details. Note that highest number of AGNs should be observable, when the distant Universe was "young", which also doesn't work well. Dwarf galaxies have usually higher hydrogen content, which is attributed to their higher age. In Big Bang model the hydrogen was formed first, the higher hydrogen content galaxy has, the older is in Big Bang model. Please don't tell me, that it doesn't work too... ;-)
SlartiBartfast
4.1 / 5 (9) Mar 15, 2017
we see more AGN at large distances because there is more volume per unit distance at large distances
It should follow cubic law after then


Sigh, square law, not cube. That's just basic, and you still got that wrong.

And the graph you linked to is completely irrelevant.
RNP
4.6 / 5 (7) Mar 15, 2017
@SiaoX
It should follow cubic law after then...

...but the distribution of AGN is completely different.

...Note that highest number of AGNs should be observable, when the distant Universe was "young"

...Dwarf galaxies have usually higher hydrogen content, which is attributed to their higher age.



First, note that, for a uniform distribution, the total number with unit distance should go as the square of the distance, not the cube. But more importantly, where is your evidence/references for the rest of your (basically false) claims?
RNP
4.5 / 5 (8) Mar 15, 2017
@SlartiBartfast
Sorry, I did not see your post until I had posted mine. Personally, I find errors such as the square/cube problem above telling, but forgivable. The lack of any actual justifications for his/her claims is what gets my goat.
gculpex
not rated yet Mar 15, 2017
This study was already done in the first season of Star trek:NG.

LOL!!!
barakn
4.3 / 5 (6) Mar 15, 2017
Tuxford, wduckss, cantdrive85, (and SiaoX to a lesser extent). There's nothing like an article about black holes to bring together all the loons :-/

SiaoX is the latest Zephir sockpuppet, no? The only reason he doesn't sound loonier is that he knows he'll get reported the instant he mentions AWT or water ripples....
SiaoX
1 / 5 (1) Mar 15, 2017
for a uniform distribution, the total number with unit distance should go as the square of the distance
The volume (and number of randomly distributed objects in it) is proportional the cube, i.e. third power of radius. It's rather difficult to argue with people, who don't know literally anything from subject. The sources were already linked in my comments (I'm the only one who is linking the sources here, BTW).
RNP
5 / 5 (4) Mar 15, 2017
@SiaoX
The volume (and number of randomly distributed objects in it) is proportional the cube, i.e. third power of radius. It's rather difficult to argue with people, who don't know literally anything from subject.


You are confusing the number within a volume (which goes as r-cubed) with the number we were discussing which was the number per unit distance (which goes as r-squared). To save embarrassing yourself further, I suggest you refrain from further comment until you understand the difference.
Captain Stumpy
5 / 5 (3) Mar 15, 2017
Study after study would suggest astrophysicists ignorance of real plasma physics would lead them to the fanciful conjecture they spout about as above.
@nazi sympathizing eu pseudoscience cult idiot
this coming from the guy that things magic invisible lightning killed D/1993 F2, made moon craters and the grand canyon and makes Enceladus geysers?

if you would just forward the evidence with measurements and validation from the journals, please, validating your argument

oh wait... there is none
nevermind

.

.

SiaoX is the latest Zephir sockpuppet, no? The only reason he doesn't sound loonier is that he knows he'll get reported the instant he mentions AWT or water ripples....
@barakn
language, syntax, linking, spelling, arguments and everything else points to yes at this time

but at least he aint talking ripples and water striders, eh?
SiaoX
1 / 5 (3) Mar 15, 2017
You are confusing the number within a volume (which goes as r-cubed) with the number we were discussing which was the number per unit distance (which goes as r-squared)
The number of stars per unit distance is not defined quantity. Anyway, my point was, it actually doesn't matter - the observed distribution of AGN's fits neither cubic, neither any other power law. And the occurrence of newly formed galaxies ends just at distance, at which they should form most prominently.
HeloMenelo
4 / 5 (4) Mar 15, 2017
Tuxford, wduckss, cantdrive85, (and SiaoX to a lesser extent). There's nothing like an article about black holes to bring together all the loons :-/


Aaaahh Bonobo and his puppets desperate for those bananas posting in here, looks like we're gonna have some fun today :D
HeloMenelo
4.2 / 5 (5) Mar 15, 2017
Study after study would suggest astrophysicists ignorance of real plasma physics would lead them to the fanciful conjecture they spout about as above.
@nazi sympathizing eu pseudoscience cult idiot
this coming from the guy that things magic invisible lightning killed D/1993 F2, made moon craters and the grand canyon and makes Enceladus geysers?

if you would just forward the evidence with measurements and validation from the journals, please, validating your argument

oh wait... there is none
nevermind

:D cracking me up, antigoracle/cannotdrive puppet also believes co2 is not toxic, he likely also believes the moon landings were fake, and the moon is made out of cheese.
Macksb
5 / 5 (2) Mar 15, 2017
I'm interested in the patters here. The two main "pattern" paragraphs are fuzzy and conflicting.

1. The third paragraph from the top says:

a. Small fluctuations (unspecified) appear first in the optical and UV bands.

b. Second, 32 days later, the very same fluctuations appear in the X ray band.

2. Near the end of the article, at the fourth paragraph from the bottom, we get a different sequence.

a. The "very same pattern" (as the X ray pattern) appears in the optical and UV bands 32 days EARLIER than the pattern that appears in the X ray band.

b. The X ray pattern is described as: Day 50 peak. Day 80 minimum. Day 110 peak.

I'll ask a specific (though ignorant) question for clarity. The pattern might be 30 day intervals. Optical first. So maybe:

Optical and UV bands first: Day 50 peak. Day 80 minimum. Day 110 peak.

X ray band: Day 142 peak (32 days later). Day 172 minimum (30 day interval). Day 202 (peak).

Help me.

Tuxford
1 / 5 (4) Mar 15, 2017
Actually the black holes are much larger and more prominent at the case of young galaxies, than at the case of the older ones. Our central black hole inside the Milky Way (which is at least 12 GYrs old) is quite tiny and inconspicuous. This would already provide some clue, what's actually going on - if only the theorists wouldn't believe so firmly, that the black holes cannot evaporate at all.

That is because the egg comes first!
https://phys.org/...wth.html
galaxies with supermassive black holes that are growing faster than the galaxies themselves

https://phys.org/...ync.html
And no one dared respond to my comment thereunder, since I had predicted such a relation to exist which was thereby verified in the following year:
https://phys.org/...ter.html

RNP
5 / 5 (3) Mar 16, 2017
@Macksb

I'm interested in the patters here. The two main "pattern" paragraphs are fuzzy and conflicting.

1. The third paragraph from the top says:

a. Small fluctuations (unspecified) appear first in the optical and UV bands.

b. Second, 32 days later, the very same fluctuations appear in the X ray band.

2. Near the end of the article, at the fourth paragraph from the bottom, we get a different sequence.

a. The "very same pattern" (as the X ray pattern) appears in the optical and UV bands 32 days EARLIER than the pattern that appears in the X ray band.


I do not understand why you say the two paragraphs are conflicting. The first paragraph you mention says the X-rays come after the optical/UV, while the second paragraph you mention says the optical/UV comes before the X-ray. There is no conflict.
Macksb
5 / 5 (1) Mar 16, 2017
RNP

Thanks for looking into this.

Yes, both paragraphs say the optical pattern is first.

But if the X ray pattern starts on day 50, and the X ray pattern starts 32 days after the conclusion of the optical pattern, on what day does the optical pattern start?

Day 50 minus 32 days is Day 18. The optical pattern takes a full 60 days (peak, minimum, peak). So the optical pattern would have to start before day zero.

Do you agree with the six suggested "dates" that I propose at the end of my prior post (2 posts above this)?

RNP
5 / 5 (3) Mar 16, 2017
@Macksb
I think I see the problem. I think you have misinterpreted the phrase "This very same pattern repeated itself 32 days later, this time in the X-ray band.".

It is perhaps better expressed using the words of the authors themselves in the abstract of the paper:

"We find that its X-ray variations are correlated with and lag the optical/UV fluctuations by 32 ± 4 days."

Is that clearer?
Macksb
5 / 5 (1) Mar 16, 2017
That's a big step forward. I am grateful.

I am still not clear on the six "dates" that comprise a full cycle of the two sequences, following the format I used near the end of my first post.

Optical days A, B, C: Peak, min, peak.

X ray days D, E, F. Peak, min, peak.

Maybe D is A plus 32. Or maybe D is C plus 32. Or something else? (In any case, 32 plus or minus 4 days as fully stated.)

Again, thanks.
RNP
not rated yet Mar 16, 2017
@Macksb
It is:
D=A+32
E=B+32
F=C+32

Macksb
5 / 5 (1) Mar 16, 2017
Thank you again!

If I may trouble you again:

What day is A? Perhaps it is Day 18 (because the Physorg press release says the X ray pattern started on Day 50).

And what exactly is Day zero--what is the marking event on which this calendar is based so precisely?

I owe you a drink or two, at least.

As I think you know, I have an unreasonable focus on sequences of periodic oscillations and their patterns. Like Captain Ahab's focus on Moby Dick, and perhaps worse in my case. You are gracious beyond measure in offering your help.
RNP
not rated yet Mar 16, 2017
@Macksb
The article says: "The researchers studied the first 270 days following the detection of the tidal disruption flare, named ASASSN-14li."

Note that the "tidal disruption flare" is not part of the ensuing pattern, which began on day 50 of the observations.

BTW. My pleasure.
Macksb
Mar 16, 2017
This comment has been removed by a moderator.
Macksb
not rated yet Mar 17, 2017
RNP

So the sequence of periodic oscillations starts with a peak in the optical, UV bands.

Then 32 days later the first peak of the X ray oscillations happens when the optical UV oscillation is at a minimum.

Then the X ray oscillation drops to its minimum as the optical UV oscillation hits its second peak. And so on.

This is the classic pattern of a system of two coupled periodic oscillations. The phases in the X ray band are the opposite of the phases in the optical, UV bands. 180 degrees offset.

Macksb
not rated yet Mar 18, 2017
Following up on my last post, the pattern of these six periodic oscillations is quite regular. Plain vanilla. Thus I am uncomfortable with the "choking" analogy. Choking suggests spasmodic, irregular.

I wonder if the period of the six periodic oscillations in the pattern (cycles of 60 to 64 days) relates in some way to a higher scale period. The first such higher scale period that comes to mind is the orbital period, around the black hole, of the soon-to-be swallowed (and liquidated to its energy equivalent) star.

That orbital period can be computed using Kepler's third law (period squared, radius cubed, etc.) where the radius is the "circumferential radius." (Schwarzschild metric.)

If some harmonic relationship exists between that orbital period and the periodic pattern of the six oscillations, then that would indicate an even higher level of regularity.

In any event, I congratulate the authors on their very interesting work

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