Ep. 782: Luminous Fast Blue Optical Transients

0:00Oh Astronomy cast episode 782 luminous fast blue optical transits. Welcome to Astronomy cast for weekly facts based journey through the cosmos we help you understand not only what we know, but how we know what we know. I'm Fraser Kane. I'm the publisher

1:02of the universe today with me as always is Dr. Pamela Gays senior scientist for the planetary science institute and the director of Cosmic Quest. Hey Pamela, how you doing? It is we have our first sign of spring. The snowballs, the little tiny white bulbs have come up. They have bloomed. They haven't ruined the snow, which is what they're supposed to do. And so we've had our first our first bulbs of spring. Yeah, we haven't had those yet. All of my bulbs are sort of peeking through the ground now through the ground layer, but no flowers yet. But I probably just a week or two away and flowers on my trees on my cherries. So I'm looking forward to that. Yeah. Modern astronomy has found new ways that the universe can surprise us. Here's one which astronomers have called luminous fast blue optical transits. They're kind of like supernova, the kind of like gamma ray burst, but they're not like them. So what are they?

2:08And we'll talk about a second, but it's time for break. And we're back. So I guess set the stage when and how did astronomers sort of dawn on them? There was an entirely new class of objects out there in the universe. And we need to also come up with an acronym or a better name for this, but maybe we'll do that later. All right. So back in 2018, folks looking through Atlas and Hong Kong Observatory data, followed up on a transient from the Zwicky transient facility. So it was found in this other data set. It was backtracked to being in the Zwicky data set. And it was catalogued. I kid you not as 80 2018 COW. The cow. The cow. Right. It's not

3:12like a coal sign for a radio station. And I just love the fact that this stuff just serendipitously happens because of how we name these transients. We just cycle through the alphabet over and over and over. And it turns out the Zwicky transient facility is out there doing an obscene amount of transient discoveries that is not getting discussed. They are able to prototype a whole lot of the data pipelines that are going to be used for the Ruben Observatory using the Zwicky transient facility because it is finding supernova after supernova moving object after moving object. Weirdo blue thing in the sky after weirdo blue thing in the sky. And the cow. The cow. The cow. It was an object that put out more light than any supernova thus far seen which was not on anyone's

4:17bingo card. Yeah. That's impressive. Yeah. Yeah. 10 to the 44 Ergs per second. Now that's how you describe a lot of energy. You got to stay in Ergs. It's true. It's true. And so there was a whole lot of what on earth could cause this confusion and hopes that there would be more. Right. And the sky did not disappoint. And for the first time in my career neither did the names. I'm going to be stupidly excited about the names of these things because astronomers generically are really really bad at naming things. Yes. But the next one that was found was ZTF Zwicky transient facility. 18 ABV. The ABV is very boring. KWLA which became Koala. Right. So so this one

5:20was also in 2018 and it was documented to reach 40,000 degrees Kelvin. They didn't have a clear distance to it so they didn't initially have clear luminosity to it. They just knew it was really, really hot. Right. Really hot. And since then I mean we have found probably about 10 of these objects. And and clearly some the astronomers that study this are delighted because as you said they're giving them silly names based on a kind of a rough correlation of what the Galbathivic alpha numeric code ends up being close to his animals. So ZTF 20 ACIG MEL. So there is a C and there is an MEL it became the camel. Right. Then we have 2023 FHN became either the finch or

6:20the fawn. And the most important one I think for today's discussion is AT2024 WPP. Yeah. The wasp. Right. And this is the brightest one that has ever been seen. Yeah. Yes. Okay. So so that's great. And so give us a sense of the characteristics of the explosion. What makes it so much different than say a supernova or a gamma ray burst? So this is something that for just a matter of weeks, peaks in brightness, extremely in the blue, extremely extremely in the blue. So we're talking super hot. Right. And it's also putting out an indescribably large amount of energy. Like this thing is is is common for you. It is the the the wasp with the most

7:23powerful one. Put out the equivalent of take 10% of the sun's mass and just turn it into energy. And that's how much energy it put out. Wow. Like Eagles of Square just convert that matter to energy. Yeah. Yeah. Just straight to energy. It's not messing around. It's just like I'm here. I'm blue. Right. I am hot. I have energy. But when we think about say gamma ray burst, right. We have the short and long gamma ray burst where it's sort of like the two second mark. If it's less than two seconds, that's short gamma ray burst. And those appear to be colliding neutron stars. If long, then it's a long gamma ray burst. And those are hundreds of seconds. Yeah. And they can be yeah, much two seconds or longer. But yeah, it can be hundreds of seconds. And that is a core collapse supernova. Yeah. That's different from the gamma ray bursts. Yeah. These are like 20 days. Right. And and and like why do astronomers think that they are not either gamma ray bursts or supernova? So the gamma ray bursts, they they just don't fit with any of the gamma ray bursts

8:25that we're seeing. They're they're not showing up in Fermi data the same way that gamma ray bursts do. Right. If you don't look and smell like a gamma ray burst, you probably aren't a gamma ray burst. But then the amount of energy that's coming out of them is just so much greater than what we've seen from supernovae that initially they were like thinking maybe there's some kind of super luminous supernovae. These are some kind of supernovae we haven't seen before. And and so people went with that theory as one possibility. Then there was the maybe this is something that's getting shredded, something that's getting destroyed, something that that's getting converted from mass to energy and went down that rabbit hole as well. So so there are all these options. Yeah. We just needed more data. Right. And and we have more data. So we're going to talk about sort of

9:25where the scientists think we are now, but it's time for another break. And we're back. So, you know, we did a flurry of reporting on this at university today in the last couple of months or so where it looks like astronomers think they're starting to settle in on an explanation. It's it's true. And and it's really cool because again, remember you're a budding super villain, Pamela. I know. So when you say something is really cool, other people should say, is this causing the entire destruction of a large volume of space? Yes. Yes. I. Yeah. Yeah. The problem. Yeah. Just remember, Pamela is a super villain. Just someone who's which is something is cool. You should be afraid. All right. She loves super volcanoes. This is this is we're talking about here. But yes, it is super cool. All right. So,

10:31sometimes one answer can encompass a spectrum of behaviors. And so in this case, it's looking like what's happening is you have stellar mass black holes for some value of stellar mass that are consuming gas, consuming stars shredding neighbors with the wasp, the most powerful of these thus far seen, probably being a roughly 10 solar mass black hole being orbited by a wolf ray a star. So something young that when these two stars were on when they were zero age main sequence stars, the one that's currently a 10 solar mass black hole was the bigger of the two stars. The wolf ray was the smaller of the two stars. And had it been allowed to live, they would have ended up being a binary black hole system someday. Right.

11:32However, instead the wolf ray star got too close to the black hole, there's lots of different things that can cause stars to migrate together. And it appears that a chunk O material was torn off the wolf ray star as it was disrupted and that chunk of material, again, roughly 10% of the mass of the sun, it just became energy as you do, as you do. Right. Right. So one thing just to clarify, you said wolf ray stars are young, they are, they're in evolved form of stars, they're yes, they're so it's a star where they've gone through the main sequence phase. Now they've sort of blown away a lot of their outer layers, but they're, but they're massive and yeah, and going to explode. And this is one of those times where adjectives are, are not what we should be using. Yeah. Because a wolf ray star has an age that's still measured using

12:37millions of civilians. Yes. And so in my brain, yeah, it never becomes old, it dies young. Yeah. And and so, so basically they become angry teenagers and die. Yeah. Now again, super villain, Pamela just described that event in very clinical terms. So allow me to sort of describe the true horror of what just happened here. You've got a black hole 10 times the mass of sun orbited by another massive, very massive star. The star got too close and the black hole tore off. It disrupted it. A huge chunk of that star and just numbed it away, causing this extremely bright flash. And you got this, you know, this bright blue ultraviolet flash coming from this, this object. And it appears that these, these blue optical transits are caused when stars are dismembered by black holes. And and there's still the potential that this could be clouds of

13:43material getting consumed. That is not eliminated. There, there, these things come in a variety of brightnesses. They behave slightly differently. Not all of them are going to be wolf ray stars getting disrupted. No, which is magnificent when it does occur. But we can imagine we've lately, there has been this amazing rash of really weird stuff getting found. So there was recently a star found that had what appears to be two planets collided and formed a giant disc around a settling together super Jupiter. And and we've seen before with I think was Epsilon Eriji, where you have a binary system that has a predator planetary disc around the companion star. So we can imagine seeing these kinds of luminous fast blue optical transients and systems where

14:44there, there's material that hasn't formed into a star yet. What we know for certain is these things that appear to consistently occur in galaxies with a large amount of star formation going on in galaxies where you expect to see massive stars still living and breathing until they get shredded by their neighbor. And and it's these kinds of systems that allow stars with ages in the millions instead of the billions to exist where we're seeing these events occurring. So again, it's massive stars getting disrupted, but there's the potential also for neighboring stars to lose their planetary discs as they get eaten before life can form. And it's interesting to sort of see like we have seen various flavors of black holes consuming stars across the universe, but generally it's in the a supermassive black hole just tourist our apart. And the supermassive

15:46black hole already has a Cretian disc around it. And this was a a minor addition to the overall luminosity that is coming from the from the black hole. Or we get this situation we talked about this I think last week or a couple of weeks ago that you can have black holes or even stars passing through the accretian disc around a supermassive black hole and then you get that flash. But this is much more you know that that's like a giant stepping on a bug. This is sort of a I don't know to use the analogy like a tiger taking down something that's you know bigger than it an elephant right. I mean the thing about this is this had the potential to be a black hole black hole system that we would later see merge not us will be dead right someone would eventually see merge with gravitational waves being released into a larger black hole. But this was literally a a tensile or mass black hole saying nope you don't get to be like me you shall be my dinner.

16:48Right and so is it doomed like there's like now it's just it's going to be meal after meal after meal until it's gone into the accretian disc and then into the black hole and it'll never get that chance to detonate on its own as a supernova. Exactly. Wow. Yeah. Yeah. Awesome. Again. I mean although I think that works you know it's awesome. In that it is feel it will fill you with all to watch it. Yes to slack job. All right we're going to talk about this some more but it's time for another break. Do you want to make a difference in your community? Do you want to provide opportunities for people with disabilities to learn new skills that lead to fulfilling careers? Then donate your unneeded vehicle to Melwood. We accept all vehicles in any condition donating is fast, free and easy. Just call 1-877-AMELWOD or visit melwood.org. That's 1-877-AMELWOD or visit melwood.org. Call and make a difference today. And we're back. So first we got to deal with one other issue here which is the name.

17:53Yeah. It's terrible. It's terrible. I don't even remember. Hold on. But the acronym is no better and astronomers genuinely are usually pretty good at this so it's the terrible. It's terrible. So they named the objects well. So I asked my audience to come up with some better names and my favorite so far is a blupernova. What do you think? Yes. Yes please. Yes. All right so astronomers if you're listening that is the name. They're not ellif bots. Right? They are blupernovas. So then what does the future hold for this for the system then? So this particular system I mean it's not possible to say with any certainty exactly how things

18:57die. We're not there as a profession yet. But over time scales I'm not going to guess. Yes. Shunks are going to get consumed. There will be additional luminous blue goodness as this disrupted object forms potentially a disc as it potentially has jets. We've seen jets in other situations. It's the case of it's dying. It has to shed its angular momentum. There's gonna end up being a disc at some point. Discs like to build magnetic fields. Those like to build jets. It's going to do the black holes eat things and it looks the same no matter what the scale is. But what's cool is we're entering an age where we just started finding these less than 10 years ago. And we're able to find it because of the zwiki transient facility. It's a fairly large scope.

20:00It's out there just going bang, bang, bang, looking at the sky, looking for things that twinkle flip flare move in the night. Oh I wonder if there's like another observatory. I know. I just spoke to come online. It's gonna do that. Yeah. Southern hemisphere maybe. So that new pipeline that is going to be able to see even more starbursts and galaxies which are much more common in the early universe. You get that bigger mirror. You're gonna be able to see things, resolve things further out. You're gonna be able to see more of these in its great depths. And so I am hoping that the things that we've started to learn exist thanks to the zwiki transient facility. We're going to get statistically significant samples of that explore the whole. Here's the span of luminosities. Here is the span of periodicities. Here is one that's recurring. Here is five that have jets that as we find more and more of them we're going to start

21:04to understand all the ways that black holes eat their neighbors. And we're used to seeing this kind of consumption and cataclysmic variables which is on our list of shows we need to do. But we needed to do this show first because there is an object called the cow. Right. That is excellent. Yeah. Yeah. I mean you mentioned Veer Rubin and there's actually a couple of ultraviolet observatories that are going to be coming online. And this is a tricky one because the wavelengths that you need to be able to detect this you need to be in space. You need a space telescope. Yeah. And that there are a couple of ultraviolet observatories in the works right now that should get us to this place where we can start to observe these on a regular basis do fall in observations and cross compare with what Veer Rubin is finding. And it's expected that we should get dozens of these every year and then you can really break them down and say okay you know these are the ones where it's a wolf rice tarp and maybe these

22:05are the ones where it's a regular star or a sequence star or a distinctive red dwarf or whatever that that that you know we know that massive stars tend to come in multiple star systems. And so then what is the trajectory of those star systems are do you get two black holes orbiting each other which then merge you can neutron stars that merge you get a white two white dwarfs that eventually merge do you get white dwarfs that consume off of a companion star and then you get a type one a supernova do you get a black hole that consumes its companion or do you just get two stars that are far away and they just never do anything mean to each other at all. So the thing that I'm hoping that we see is we we have hints that hypernova that generate long duration gamma ray bursts are potentially a binary system where the massive star goes supernova onto a compact neighbor that has given it extra angular momentum. And and so we're going to be seeing potentially systems that that compact neighbor is not just a neutron star it's a black hole.

23:10And as you go supernova that material goes zoom and gets eaten and and and these are low probability objects. The most massive objects are the most rare the the initial mass function of stars is like not very many super bright ones lots and lots and lots of these really faint ones and and then we're just left with a universe of uninteresting little tiny red stars that like bake their baby planets. The more sample size we have the higher the likelihood we're going to start seeing these long duration gamma ray bursts to understand what's going on and start seeing them in more and more kinds of pairs and it's just awesome. Yep. Yep. I mean and that's the part that I really love. I mean you know to go down into totally different rabbit hole we're sort of moving into the same regime with exoplanets in their atmosphere. So we you know we only we know of say 6,000 exoplanets but we only have a few dozen that their atmosphere. So we've been

24:13imaged none that are earth sized you know around red dwarfs or around some like stars and and so we don't know what's normal yet. We don't know what is the how these things evolve and when new telescopes come on mind they will get these larger data and eventually we will be you know we will know tens of thousands hundreds of thousands millions of planetary systems and we will understand in this very rich way and then we will be able to do the same for the future of star systems that we can look out and have enough of the universe in our minds at one time that we will understand how things work how things play out what the future evolution looks like what the past looks like it's a it's a very cool direction that we're heading in and a lot of these big tools especially very Ruben are going to get us huge steps forward so any day now so we'll last remind everybody blooper novice okay we seriously need to figure out who to write too because that

25:18is excellent yeah but we just do you don't write to anybody you just start saying the word until it sticks I like that all right thanks Bella thank you Fraser and thank you so much to everyone out on patreon who is supporting us at patreon.com slash astronomy cast this week we would like to thank the following $10 a month in up patrons Adam and East Brown Alex Reign, Andrew Polestra, Antisaur, Astro Bob, Bart Flarity, Benjamin Davies, Bob Zatsky, Bresnick, Brian Kegel, Bruce Amazine, Kami Rassian, Cody Rose, Dale Alexander, David, David Green, Disasterina, Dr. Jeff Collins, Elliott Walker, Evil Melchie, Felix Goot, Frank Stewart, Galactic President, Scooper, Star McScoop Salad, Glenn Phelps, Gordon Dewis, Gregory Singleton, Helga Bjorkog, James Signorvich, Jason Kwong, Jeff Wilson, Jim Schooler, Joe Holstein, John Drake,

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