The StarXiv ✨ podcast

Simple cartoon of the assembly of a supermassive disc (SMD)and supermassivestar(SMS)system that appear as little red dots (LRD). Major mergers of galaxies with at least ∼10^8 solar masses of gas trigger strong inflows that result in a compact self-gravitating disc at sub-pc scale, with typical temperatures of ∼4000 K.The disc feeds a highly accreting SMS which radiates as a hot black body (∼20000 K) due to its own accretion luminosity

Can super massive stars with compact massive accretion disks form massive black hole seeds AND explain the observations of Little Red Dots? This paper claims they can! Michelle talks us through the details. 🔭☄️ arxiv.org/abs/2507.22014

In Payel's last paper, new simulations are run to trace the dynamic evolution of stellar clumps like in the Sparkler galaxy at z=1.4 using JWST, to see if their detected masses and dimensions can be reconciled with the considerably smaller values observed in Milky Way GCs.🔭☄️
arxiv.org/pdf/2507.13904

Images of two fields near or centered on the redshift 7 quasar. Newly detected galaxies at the same redshift are highlighted as green circles. In total, there are 19-22 galaxies in the vicinity to the quasar that could help it grow. But is that enough..?

Michelle also delved into this paper that tries to understand whether an unusual quasar at redshift 7 has enough galaxies nearby to allow it to get back on the black hole stellar mass relation by redshift zero. 🔭 ☄️ arxiv.org/abs/2507.13489

Payel then discusses a paper looking at how hierarchical mergers of stellar-mass black holes in nuclear star clusters or AGN disks can create a binary black hole system with individual masses falling within the range of the pair-instability supernovae black hole mass gap.
🔭☄️
arxiv.org/pdf/2507.17551

What creates a puffy, hot, and very fast moving white dwarf? Payel discusses a paper exploring whether these stars might be carbon-core burning white dwarfs in double-degenerate binaries, flung out by their exploding partner. 🔭☄️
arxiv.org/pdf/2507.15952

Posterior distribution showing derived properties of a dark matter sub-halo The panels show the PDFs that display our constraint for the mass of the sub-halo (in solar masses), and its Galactic d,l,b position (where d is the heliocentric distance in kilo- parsec and l and b are in degrees) using the set of high S /N binary pulsars that are centered near the binary pulsar set PSR J1640+2224, PSR J1713+0747.

Did we finally detect a starless dark matter subhalo? Michelle leads us through a paper that claims to find one near the Sun using pulsar accelerations 😍 🔭 ☄️ arxiv.org/abs/2507.16932

StarXiv: a podcast discussing the latest astronomy papers Astronomy Podcast · Updated fortnightly · Hello! Welcome to the StarXiv, hosted by Dr Michelle Collins and Dr Payel Das. This is a biweekkly podcast that delves into the latest astronomy papers &…

You can also listen on Spotify, Apple podcasts or wherever you get your podcasts. Don't forget to subscribe, so you never miss an episode! podcasts.apple.com/gb/podcast/s...

Episode 17 has dropped! Tune in to hear Payel & Michelle talk about about a dark matter subhalo detection, the problem(s) with super massive black holes, massive star clusters in the Sparkler, speedy white dwarfs and more! 🔭☄️ starxiv.com/2025/08/04/e...

Episode 17 – detecting dark matter, unusual black holes and speedy stars In this episode, Michelle and Payel explore the detection of a starless dark matter subhalo, the characteristics of fast, puffy white dwarfs, and the formation and merging processes of black holes. They also discuss star clusters in the Sparkler galaxy, referencing relevant research papers for further insight.

Episode 17 – detecting dark matter, unusual black holes and speedy stars

In this episode, Michelle and Payel explore the detection of a starless dark matter subhalo, the characteristics of fast, puffy white dwarfs, and the formation and merging processes of black holes. They also discuss star…

Episode 16 – interstellar visitors, molten planets and faint, dark galaxies In this episode, Michelle and Payel squash in more papers than ever, as Michelle delves into a flurry of papers about new newly discovered interstellar comet: 3I/ATLAS. They also discuss what sets …

Two more days until we record our next podcast! Summer seems to be a very productive time for finishing papers - well done astronomers! You can tune into our last episode at starxiv.com/2025/07/21/e..., or on Spotify, Apple podcasts, Amazon, or wherever you get your podcasts. 🔭☄️🧪

A figure showing the planet mass vs radius of planet, with TOI-2431b highlighted. Its position suggests its composition is similar to but slightly denser than the Earth.

Michelle also discussed the detection of the ultra-short period planet TOI-2341b, which has an orbital period of only 5.4 hours! This object is so close to its star that its surface is likely molten 🌋 🔭 ☄️ arxiv.org/abs/2507.08464

Gah! Just a little too late to make it into my 3I/ATLAS @starxiv.bsky.social round up! The episode just went live but this would have been a great addition🤩☄️🔭

In Payel's last paper, the authors employed symbolic regression with simulations to model the probability distribution function of distances to dark haloes from two bright neighbouring galaxies. This could guide future observational efforts. 🔭 ☄️
arxiv.org/pdf/2507.01814

Payel's second paper looked at local highly star-forming galaxies to gather more clues about the high N/O, low-metallicity galaxies found at high redshift by JWST. Outflows might play a role! 🔭 ☄️
arxiv.org/pdf/2507.11658

Discovery imaging of the comet from ATLAS. 3I/ATLAS sits inside the red circle (which is hard to see). The directon of motion is shown with an arrow. The comet itself is a faint little blip among a field of bright stars. The images on the right have the background stars sibtracted so you can see the comet more easily.

A stacked image taken with the VLT FORS2 instrument. You can clearly see the come as a blob with associated haze. This is its coma!

Here we have the reflectance spectrum of 3I/ATLAS (black) compared with the other 2 interstellar comets and 67P. It is very red, but also quite featureless.

g, r and i band images of the comet, as well as its brightness profile compared to a star (where you clearly see a more extended profile for 3I/ATLAS). The images again show a hazy object.

Michelle took on the mammoth task of summarising 4 papers on our newest interstellar visitor, the 3I/ATLAS comet! She discussed its orbit (highly eccentric and fast moving), colour (pretty red), coma and activitiy (yes and undetected as yet) and origin (a thick disk star?). 🔭 ☄️

If in doubt, it's feedback! Payel discussed a paper that patched models for tiny UFDs to large-scale MW models, revealing that the metallicity of the intergalactic medium doesn't influence UFD metallicities. However, mass-loading factors were deemed important. 🔭☄️
arxiv.org/pdf/2507.03182

StarXiv: a podcast discussing the latest astronomy papers Podcast · Michelle and Payel · Hello! Welcome to the StarXiv, hosted by Dr Michelle Collins and Dr Payel Das. This is a biweekkly podcast that delves into the latest astronomy papers & results from…

You can also listen on Spotify, Apple podcasts, Amazon, or wherever you get your podcasts. open.spotify.com/show/7rDlEt8...

Our latest episode is live! Listen to Michelle and Payel discuss interstellar comets, molten worlds, nitrogen rich galaxies, ultra-faint and dark galaxies! This episode, they packed in 8 papers! It's quite a ride. 🔭☄️ starxiv.com/2025/07/21/e...

Episode 16 – interstellar visitors, molten planets and faint, dark galaxies

In this episode, Michelle and Payel squash in more papers than ever, as Michelle delves into a flurry of papers about new newly discovered interstellar comet: 3I/ATLAS. They also discuss what sets the metallicities of the…

The top panel shows the flux measured for COSBO-& in a range of bands from near-infrared to the radio (the spectral energy distribution or SED). They measured the redshift using all bands (black, IR from JWST (green) and mid-IR to radio (yellow). The more filters included, the more accurate the redshift. They also neasure stellar mass, star formation rate, dust mass, and extinction. The posteriors for these (and the redshift) are shown in the lower panels.

Michelle's last paper was a quick research note on how and why photometric redshifts can fail dramatically. This paper focused on the COSBO-7galaxy, and the authors show why different teams got different results, and how to fix this going forward. arxiv.org/abs/2507.01251 🔭 ☄️

Birth radius is recovered as one of the latent variables important for observables known to be relevant for radial migration.

In Payel's last paper, she talks about how to look for things you didn't know existed using graphs. The authors discover birth radius as a latent variable important for observations relation to radial migration.
arxiv.org/abs/2507.00134 🔭 ☄️

How spin period and X-ray luminosity vary against star mass and orbital period.

Payel also discovered that binaries could explain the existence of the ultra-long period pulsars that Michelle discussed a few podcasts ago. Hurray for binaries!
arxiv.org/abs/2507.00946 🔭 ☄️

The PAndAS survey map of the Andromeda galaxy (centre) and its messy outskirts. You can make out stellar streams from past accretions, as well as Andromeda's messy outer disk. The outer GCs are indicated with points, coloured by whether they are aligned with substructure, not aligned with substructure, or ambiguous. What a beauty of a galaxy!

Michelle couldn't help but talk about the globualr cluster (GC) system of the Universe's greatest galaxy: Andromeda. The authors study the outer GCs of M31 and show that those which align with streams have redder horizontal branches. A cool way to identify accreted GCs arxiv.org/abs/2506.21267 🔭 ☄️

Flares coincide with transit point.

Payel discovered in this paper that planets can induce flares on the stars they orbit! As long as they're close enough in. Find out more about the first ever planet-induced flare at:
arxiv.org/abs/2507.00791 🔭 ☄️

A schematic showing the evolution of a population III galaxy. They start with a pure population III galaxy on the left, initially pristine. It then self-pollutes as its first stars go supernova. After this, population II stars start to form and the fraction of population III stars rapidly decreases, until the galaxy is 100% population II (on the right).

How will we find Population III galaxies? Michelle dived into a paper that simulated the spectra we expect to see from these fossil galaxies. They show how the emission features vary with time, and even find a handful of new candidates! arxiv.org/abs/2506.17400 🔭 ☄️

StarXiv: a podcast discussing the latest astronomy papers Podcast · Michelle and Payel · Hello! Welcome to the StarXiv, hosted by Dr Michelle Collins and Dr Payel Das. This is a biweekkly podcast that delves into the latest astronomy papers & results from…

You can also find us on Spotify, Apple podcasts, Amazon music or wherever you get your podcasts. open.spotify.com/show/7rDlEt8...

Happy Monday! Start the week with episode 15 of the StarXiv! Listen to Michelle and Payel discuss long period radio pulsars, planetary induced flares, globular clusters in Andromeda, lGalactic archaeology, avoiding redshift catastrophe and pop III galaxies starxiv.com/2025/07/07/e... 🔭 ☄️

Episode 15 – Flare-inducing planets, avoiding catastrophe, and accreted star clusters

In this episode, Michelle and Payel delve into topics including long period pulsars, population III galaxies, and Galactic archaeology. They discuss noteworthy research on metal-free galaxies, stellar flares…

Episode 14 – A cosmic owl, misaligned planetary systems, and the Milky Way as an outlier In this episode, we had Payel and Nicole filling in for Michelle who’s away on holiday. Nicole is a PhD student, also at the University of Surrey Astrophysics research group. They discuss the…

I'm back from two weeks of leave, and having caught up on email, I'm now into the arxiv! Have to be ready for recording the next @starxiv.bsky.social this Friday! Check out the last episode from @payeldas.bsky.social and @nbuckley0810.bsky.social on our website! 🔭☄️🧪 starxiv.com/2025/06/22/e...

Nicole’s last paper looked at what kind of IMF can explain the early metal-rich galaxies seen by JWST. Turns out you need stars ≥200 M☉ to match the cosmic SFRD and MZSFR at z ≈ 4–10. The best model also needs weak outflows and compact galaxies! 🔭
arxiv.org/abs/2506.06139