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Hi! I'd love be added to the science feed. I'm an astrophysics PostDoc at the University of Southampton: orcid.org/0000-0002-65...

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ORCID

I’m a PostDoc at the University of Southampton working on tidal disruption events and supernovae!

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The paper of course goes into much more detail on how the search for these objects actually works and on the detailed analysis of each (though it is nearly 50 pages ☠️). Very happy to answer any questions folks have about it and stay tuned for more! Thanks again to all my collaborators! 😁

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As we add more and more objects to these relations (much more to come on this in the not too distant future 👀) the shared behaviour is beginning to reveal the commonality of the local environments of the supermassive black holes lurking in the cores of galaxies.

Instead, their outbursts in the longer wavelength (redder) MIR band tend to be brighter than in the shorter wavelength (bluer) band. This is also confirmed by those TDEs with redder outbursts also having larger outbursts overall.

Here I would *strongly* advise those interested in the details to read the paper, but in brief: Changing look AGN outbursts follow a 1-to-1 relation in their peak changes in luminosity in the two WISE bands. whereas ECLEs and other TDEs don't follow this relation.

AT 2018dyk: tidal disruption event or active galactic nucleus? Follow-up observations of an extreme coronal line emitter with the Dark Energy Spectroscopic Instrument

The particularly keen may remember this from my last paper on AT 2018dyk - academic.oup.com/mnras/articl... With the new objects we've been able to better estimate the uncertainties on the relations and confirm more data isn't making it vanish back through the veil of low number stats 😅

academic.oup.com

ABSTRACT. We present fresh insights into the nature of the tidal disruption event (TDE) candidate AT 2018dyk. AT 2018dyk has sparked a debate in the litera

In particular their behaviour in MIR is very comparable to previously identified objects which is all tied up in this plot:

A two panel figure showing the differences in mid-infrared outburst behaviour between TDEs showing high energy emission lines and changing look AGN.

Left: Changing look AGN closely follow a 1-to-1 relation between their peak changes in brightnesses in the two WISE bands. TDEs showing high energy emission lines in contrast deviate from this, with their outbursts significantly larger relative to their original brightness in redder of the two bands. Right: Those high energy TDEs showing large outbursts also show redder outbursts in the MIR. This is not the case for AGN.

The good news being that whilst all three are unique they all show the same general behaviour and evolution compared to the known objects - which helps to confirm that they are all produced in the same way rather than multiple groups that happen to look superficially alike.

Raichu Pokemon Charging Up

We compared these three new ECLEs (Pidgeot, Raichu and Raticate - named because I am a Pokemon obsessed Millennial who struggles with phonenumber-esqe internal IDs 😅) to the existing (limited) sample to get a better handle on the range of properties these objects can display.

static.klipy.com

Alt: The Pokemon Raichu rubbing its cheeks.

Thankfully, because their spectral signatures are quite distinct this is a solvable problem - as long as you look at enough galaxies! In this work we explored DESI's Early Data Release and found 3 new ECLEs (and several other strange objects).

As powerful tools as they are ECLEs have the thorny issue that they are rare. We describe in the paper that if you look at a million galaxies for a year you'd expect to see about 5 ECLEs. Needle in a haystack anyone?

A lot of the high energy photons that get absorbed by the material is re-radiated in the mid-infrared (MIR) over several years. This allows us to monitor the behaviour of these sources for some time and map out what's going on at various distances from the black hole.

this can light up any material nearby like a possessed Christmas tree 🎄 making it visible to us millions of light years away. This material isn't related to the star being torn apart itself, it was happily chilling in its galaxy's centre before being exposed to the universe's brightest sunbed.

The material at the centres of most galaxies is very difficult to observe and map in detail because its (generally) cold and dark which makes it hard to probe. When a star gets torn apart (the event itself is called a tidal disruption event / TDE) by the central black hole and emits a lot of energy

They actually get their name as the lines of highly ionised iron (iron atoms that have lost between 6 and 13 electrons) were first picked up in the Sun's extremely hot outer atmosphere - it's corona. Its not just the very high energies that make these interesting objects though.

... emission signatures in the resulting spectrum of the galaxy we can observe like a supermarket barcode (or black box recording). As these events are so violent they can knock a lot of electrons out of atoms and produce really distinct patterns if you know what to look for.

Such a process is (to the shock of no one) rather violent, and produces a lot of high energy photons (X-rays / ultraviolet etc). If the X-rays collide with material that up to now was happily orbiting the black hole they can knock electrons out of atoms and this in turn generates specific ...

This builds on my previous work looking for Extreme Coronal Line Emitters (ECLEs), using the Dark Energy Spectroscopic Instrument (DESI). "But Peter, what's an ECLE?" I hear you ask. Well the simplest way to think about them is the echoing screams of stars being torn apart by black holes 😱

Emma Monk @monkemma.bsky.social · 24/06/2026

Reposted by Peter Clark

It was inevitable, wasn't it🙄 Of course the Telegraph would run with something like this👇 So let's remove some of the rose-tinted spectacles and also look at some of that data comparing 1976 with modern heat waves Because the 1976 nostalgia porn is wearing a bit thin at this stage 🧵1/23

Telegraph headiline:

"Heatwave hysterics wouldn't have lasted a day in 1976", overlaid with a bold “MONK DEBUNKED” stamp.

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Peter Clark @lightbulb500.bsky.social · 31/03/2026

A heads up that abstract submissions for this years National Astronomy Meeting in Birmingham (UK) close on April 2nd! Plenty of interesting sessions, and not just because I'm organising one of them 👀 We'd love to see you at the 'First results from the next generation of transient surveys' session!

uobevents-national-astronomy-meeting-2026.eventsair.site

Programme

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Reposted by Peter Clark

University of Southampton @unisouthampton.bsky.social · 22/10/2025

Revolutionary new space telescope @4most-eu.bsky.social has captured its first data from the universe. Our scientists are part of the team behind the super-scope and say it’ll reveal how galaxies and black holes formed. Read more 👉 tr.ee/ba4NEs

The VISTA 4MOST, a large, intricate astronomical device, housed inside an industrial facility. The structure features a prominent circular component with visible wiring and metal framework, supported by a sturdy blue frame with stairs and a raised platform for access.

The VISTA mountain top observatory stands on rocky terrain under a clear night sky, with the Milky Way stretching across and a bright planet shining above.

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Reposted by Peter Clark

Royal Astronomical Society @royalastrosoc.bsky.social · 07/08/2025

Researchers at the University of Portsmouth and UFRGS in Brazil say the cosmic behemoth is close to the theoretical upper limit of what is possible in the universe and is 10,000 times heavier than the black hole at the centre of our own Milky Way galaxy. Read more at: ras.ac.uk/news-and-pre...

ras.ac.uk

'Most massive black hole ever discovered' is detected

Astronomers have discovered potentially the most massive black hole ever detected. The cosmic behemoth is close to the theoretical upper limit of what is possible in...

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Reposted by Peter Clark

Lewis Goodall @lewisgoodall.com · 15/07/2025

Two governments took The News Agents to secret court for two years via a constitutionally unprecedented superinjunction to stop you from hearing this story. The MoD is responsible for a data leak that put up to 100,000 Afghans at risk of death. www.youtube.com/watch?v=Zdc6...

youtube.com

The secret court that silenced the News Agents...until now

YouTube video by The News Agents

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Reposted by Peter Clark

SpaceAustralia.com @spaceaustralia.com · 05/06/2025

An Emerging Risk To #RadioAstronomy 📡 Using a prototype SKA-Low instrument, a new analysis from @icrar.bsky.social has detected Starlink signals leaking into protected radio bands. @cosmicrami.com writes about this new study. www.spaceaustralia.com/news/emergin... 📸 Astro_Work 🔭 #SpaceAustralia

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Peter Clark @lightbulb500.bsky.social · 05/06/2025

Didn't have this level of political chaos on the bingo card today 👀

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Thanks for reading! Very happy to answer any questions you might have on this or the paper itself ☺️

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MIR observations are a powerful tool in helping to break the degeneracies between these groups. On a final note, the MIR observations were made by favourite telescope WISE, which was decommissioned and burned up in Earth's atmosphere last year after more than 14 years of data gathering. 🫡

Artist's impression of the WISE spacecraft in orbit.

Credit: NASA/JPL-Caltech

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There is a lot more in the paper about the analysis and sample comparisons, but this thread is already feeling like another paper so I will end it here 😅 To conclude! AT 2018dyk is fascinating TDE that occurred in a gas rich environment. Telling TDEs apart from AGN flares is *not* an easy job

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all had small and relatively 'blue' outbursts. This is an indication that the different classes of object have environmental differences - perhaps differing amounts of gas/dust or configurations. I'll be extending and refining this analysis with more objects going forward so stay tuned!

outbursts in the longer wavelength (redder) MIR band tend to be brighter than in the shorter wavelength (bluer) band. This is also confirmed (those limited by the small number statistics) by those TDEs with redder outbursts also having larger outbursts. Whereas the changing look AGN we explored

I *strongly* advise those interested in the details to read the paper, but in summary. Changing look AGN outbursts follow a 1-to-1 relation in their peak changes in luminosity in the two WISE bands. TDEs showing the high energy iron emission lines don't follow this relation. Instead, their

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the MIR behaviour these objects could be used to help tell them apart in a consistent way. In short - yes it can! Though a lot more work and observations will be needed to tie down the specifics. Enter this plot:

If this sounds familiar from how the iron and OIII lines are generated, that's because its the same processes involved. Just at a lower energy regime. As TDEs and AGN related flares are still hard to tell apart - and alas not every galaxy has MaNGA data to help with this - I started to wonder if

in this case is rich in gas because we see a significant flare in the mid-infrared (MIR) at the time following 18dyk's optical detection. Such MIR flares occur when the optical and UV photons thrown out by a TDE get absorbed by nearby material and then reradiated at longer wavelengths over time.

is a less extreme version of this where material at greater distances (or lines of sight) from the SMBH is responding to the increased flux produced by the TDE. We will have to revisit the galaxy in a few more years to see how this emission has evolved. We also know that the region around the SMBH

TDEs release a lot of high energy photons which can ionise and affect the gas close to the SMBH. We see this in the earlier spectra of 18dyk around its peak brightness which have highly ionised iron emission lines. These lines are only generated in the presence of X-rays. The delayed OIII emission

This, combined with the new spectrum closely resembling the original SDSS spectrum and with the light-curves (both optical an mid-infrared) of 18dyk behaving in a very transient manner (Flat -> Outburst -> Flat), strongly point to 18dyk being a TDE. What about the increased OIII emission though? 👀