Peter Clark
@lightbulb500.bsky.social
Postdoctoral Research Fellow at the University of Southampton. Working on tidal disruption events and supernovae 💥💥😎. Opinions are my own. He/Him
Reposted by Peter Clark
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...
Read more at: ras.ac.uk/news-and-pre...
'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...
ras.ac.uk
August 7, 2025 at 1:56 PM
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...
Read more at: ras.ac.uk/news-and-pre...
Thanks for reading!
Very happy to answer any questions you might have on this or the paper itself ☺️
Very happy to answer any questions you might have on this or the paper itself ☺️
May 30, 2025 at 1:56 PM
Thanks for reading!
Very happy to answer any questions you might have on this or the paper itself ☺️
Very happy to answer any questions you might have on this or the paper itself ☺️
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. 🫡
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. 🫡
May 30, 2025 at 1:56 PM
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. 🫡
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. 🫡
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
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
May 30, 2025 at 1:56 PM
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
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
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!
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!
May 30, 2025 at 1:56 PM
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!
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
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
May 30, 2025 at 1:56 PM
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
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
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
May 30, 2025 at 1:56 PM
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
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
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:
In short - yes it can! Though a lot more work and observations will be needed to tie down the specifics.
Enter this plot:
May 30, 2025 at 1:56 PM
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:
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
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
May 30, 2025 at 1:56 PM
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
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.
May 30, 2025 at 1:56 PM
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
We also know that the region around the SMBH
May 30, 2025 at 1:56 PM
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
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
The delayed OIII emission
May 30, 2025 at 1:56 PM
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
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? 👀
What about the increased OIII emission though? 👀
May 30, 2025 at 1:56 PM
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? 👀
What about the increased OIII emission though? 👀
region of the galaxy each, and all obtained simultaneously.
This allowed us to perform a much more in-depth analysis of how these emission lines are being produced - with this indicating that the emission lines prior to 18dyk being produced by evolved stars rather than AGN activity.
This allowed us to perform a much more in-depth analysis of how these emission lines are being produced - with this indicating that the emission lines prior to 18dyk being produced by evolved stars rather than AGN activity.
May 30, 2025 at 1:56 PM
region of the galaxy each, and all obtained simultaneously.
This allowed us to perform a much more in-depth analysis of how these emission lines are being produced - with this indicating that the emission lines prior to 18dyk being produced by evolved stars rather than AGN activity.
This allowed us to perform a much more in-depth analysis of how these emission lines are being produced - with this indicating that the emission lines prior to 18dyk being produced by evolved stars rather than AGN activity.
Strong OIII emission is usually a sign of AGN activity, but its more complicated than that as emission lines can be generated my multiple different processes.
To investigate further we also explore archival MaNGA data of the galaxy, which in essence consists of many spectra each covering a small
To investigate further we also explore archival MaNGA data of the galaxy, which in essence consists of many spectra each covering a small
May 30, 2025 at 1:56 PM
Strong OIII emission is usually a sign of AGN activity, but its more complicated than that as emission lines can be generated my multiple different processes.
To investigate further we also explore archival MaNGA data of the galaxy, which in essence consists of many spectra each covering a small
To investigate further we also explore archival MaNGA data of the galaxy, which in essence consists of many spectra each covering a small
18dyk's host galaxy doesn't make this easy as its previous (before 18dyk occured) emission line behaviour classifies it as a Low-ionization nuclear emission-line region (LINER) which can be produced by either a relatively 'weak' AGN or emission from evolved stars unrelated to a SMBH.
May 30, 2025 at 1:56 PM
18dyk's host galaxy doesn't make this easy as its previous (before 18dyk occured) emission line behaviour classifies it as a Low-ionization nuclear emission-line region (LINER) which can be produced by either a relatively 'weak' AGN or emission from evolved stars unrelated to a SMBH.
This shows us that whatever the process that generated 18dyk was, its not an ongoing one, with the host galaxy having returned close to its original state.
I say *close* to because the spectra don't match exactly - the more recent DESI spectrum has much stronger OIII emission than the SDSS spectrum
I say *close* to because the spectra don't match exactly - the more recent DESI spectrum has much stronger OIII emission than the SDSS spectrum
May 30, 2025 at 1:56 PM
This shows us that whatever the process that generated 18dyk was, its not an ongoing one, with the host galaxy having returned close to its original state.
I say *close* to because the spectra don't match exactly - the more recent DESI spectrum has much stronger OIII emission than the SDSS spectrum
I say *close* to because the spectra don't match exactly - the more recent DESI spectrum has much stronger OIII emission than the SDSS spectrum
This spectrum is particularly interesting as we can now explore what the host galaxy is doing now that 18dyk itself has faded away.
We first compared this new spectrum to an archival spectrum obtained by the SDSS years before 18dyk was seen to outburst. With the two looking remarkably similar.
We first compared this new spectrum to an archival spectrum obtained by the SDSS years before 18dyk was seen to outburst. With the two looking remarkably similar.
May 30, 2025 at 1:56 PM
This spectrum is particularly interesting as we can now explore what the host galaxy is doing now that 18dyk itself has faded away.
We first compared this new spectrum to an archival spectrum obtained by the SDSS years before 18dyk was seen to outburst. With the two looking remarkably similar.
We first compared this new spectrum to an archival spectrum obtained by the SDSS years before 18dyk was seen to outburst. With the two looking remarkably similar.
We decided to explore a new spectrum of the galaxy that hosted 18dyk obtained by the Dark Energy Spectroscopic Instrument - DESI which you may be familiar with from its recent cosmology results : newscenter.lbl.gov/2024/04/04/d...
newscenter.lbl.gov
May 30, 2025 at 1:56 PM
We decided to explore a new spectrum of the galaxy that hosted 18dyk obtained by the Dark Energy Spectroscopic Instrument - DESI which you may be familiar with from its recent cosmology results : newscenter.lbl.gov/2024/04/04/d...