The StarXiv ✨ podcast

Left panel: optical CMD, namely F555W-(F439W-F555W), of the globular cluster NGC 362 based on HST photometry from Piotto et al. (2002); three red filled squires show the expected consecutive locations of an initial MS binary in its evolution toward RGB-like merger remnant, schematically shown in the right panel; the blue points show the stars of the RGB in its total range beginning from the RGB base. Right panel: schematic illustration of the main consecutive stages of the evolution of a hard binary initially composed of two MS stars (1), then converted into a (MSS+HeWD) binary (2), which finally merges forming RGB-like merger product (3) evolving along the cluster RGB.

Nicole’s final paper discussed this new take on second-gen (G2) stars in globular clusters: maybe they weren’t born polluted… maybe they merged into it. Mergers of MS + HeWD binaries can produce G2-like stars with He and N enrichment — even in the field.
arxiv.org/abs/2509.15337 🔭☄️

The BepiColombo trajectories for MFB1 (marked, blue), MFB2 (marked, green) and MFB3 (marked, purple) in MSM coordinates: (a) X-Z plane, (b) X-Y plane, and (c) X-ρ plane. Each trajectory is shaded as a function of time and arrows indicate the MIPA boresight for each flyby, spaced 10 minutes apart. Panel (a) includes example field lines from the KT17 model. Panel (c) includes the location of the magnetospheric boundaries observed by MIPA (bow shock = X, magnetopause = +) and closest approach (star). All panels include the Shue magnetopause model (dark blue, Shue et al., 1997) and average bow shock (red) positions using parameters from Winslow et al. (2013).

Michelle's final paper takes us through BepiColombo's latest results on the magnetosphere of Mercury with data taken form 3 fly-bys over the nightside of the planet. Listen to learn more about the complex snap-backs and plasma flows of this little planet. 🔭 ☄️ arxiv.org/abs/2509.17872

Adaptively smoothed and combined image of Mrk1216. The solid white annuli mark the regions selected for analysis, extending out to R500. The central region is coloured black for visual clarity. The green dashed annulus indicates the background region.

Nicole’s second paper looked at the fossil galaxy Mrk1216 — compact and untouched since z ≈ 2. Its hot gas is still α-enhanced, with [Mg/Fe] ≈ 0.37 and a flat Type Ia SN contribution out to large radii. All signs point to early, rapid star formation.
arxiv.org/abs/2509.14613 🔭☄️

Data showing the flare profiles measured in 2024 and 2025. The luminosity and period have dramatically increased!

In Michelle's second paper, we learned about quasi-periodic eruptions from Ansky and what might generate them. In this case, new monitoring shows that the period and intensity of Ansky's QPEs are increasing, but why? Tune in to find out ☄️ 🔭 !https://arxiv.org/abs/2509.16304

Top: Number of stars per time bin. Bottom: dM along with 16th to 84th percentile spread of dM over TSF assuming instantaneous and homogeneous mixing across spheres of radius R. (The zero-point of TSF is the time at which each star forms.) Prior to ∼7Myr after a star forms, smaller spheres have smaller dM. The dM for each sphere intersects at ∼7Myr, suggesting τchem=7Myr. After 7Myr, the dM of spheres R≤0.1kpc continues to increase dramatically, consistent with rapidly changing local gas, whereas the dM of spheres R≥0.5kpc flattens, consistent with expectations for an IMF-averaged gas abundance.

Nicole talked about early metal mixing with Aeos, a sim of Pop III enrichment. Gas is only chemically coherent within 100 pc and 7 Myr after a SN. Beyond that, stars form with distinct abundance patterns. This Mahalanobis distance plot shows this divergence.
arxiv.org/abs/2509.13580 🔭☄️

Amateur image of NGC 7531 (left). DESI Legacy Imaging Survey image of NGC 7531 (right). Sky-subtracted image of NGC 7531 as processed by Gnuastro’s NoiseChisel program was used as a basis for photometry measurements. Features are labelled: (a): main shell; (b): faint outer shell; c: counter plume.

Michelle's first paper discusses the Pearl in the Shell, a study of an ultra compact dwarf and a debris cloud around a nearby spiral galaxy. The study combines data from professional and amatCheck it out in our latest episode! arxiv.org/abs/2509.14038 🔭 ☄️

Episode 21 is live! Tune in to here the latest results on Mercury's magnetosphere, population III stars, relic galaxies, quasi-periodic eruptions and more, with your hosts, Michelle and Nicole. Available on our website, Spotify, Apple, or wherever you get podcasts 🔭 ☄️

Episode 21 – Mercury, chemistry and quasi periodic eruptions  In this episode, Michelle and Nicole explore various astronomical topics, including merger debris around a galaxy, metal-mixing in early stars, quasi-periodic eruptions in Ansky, relic galaxies, Mercury's magnetosphere, and second-generation stars in globular clusters. Tune in on Spotify, Apple Podcasts, or other platforms for more insights.

Episode 21 – Mercury, chemistry and quasi periodic eruptions 

In this episode, Michelle and Nicole explore various astronomical topics, including merger debris around a galaxy, metal-mixing in early stars, quasi-periodic eruptions in Ansky, relic galaxies, Mercury's magnetosphere, and…

Payel's final paper claims a remarkable agreement between theory and observations with regards to gravitational wave mission from stellar mass black hole binaries! 🔭 ☄️
arxiv.org/pdf/2508.20787

Probability of LG dSphs to host terrestrial planets dwelling for ∆tin a safe environment, Phost, as a function of the dSph luminosity. Curves are obtained through the probability of galaxies forming planets and the probability of them surviving for ∆t= 1 Gyr (left panel, solid) and ∆t= 4 Gyr (right panel, dashed). Shaded areas represent the uncertainties from the error propagation.

Michelle's final paper asks whether the faintest dwarf galaxies may be the first safe places to form habitable worlds. Can ultra-faint dwarfs form terrestrial planets early and develop life? We dive into it in this episode. 🔭 ☄️ arxiv.org/abs/2509.01669

Top: A color composite of our ACS/WFC1 imaging (∼100′′×202′′). The green circle (r = 8.4′′) marks the VLA H I maximum column density, with a radius corresponding to the effective radius of a Leo T analog at the distance of M94. Bottom: Simulated dwarf galaxies spanning a range of stellar masses, generated under the same observing conditions and shown at the same physical scale as the ACS data. A Leo T analog (M⋆ = 100,000 solar masses) would be readily detected, but no stellar counterpart is visible down to at least M⋆ ∼ a few thousand solar masses M⊙.

Michelle's second paper reports on Cloud-9, a proposed 'star free' galaxy (or reionization limited HI cloud, RELHIC). They follow it up with very deep HST imaging, but still can't find any stars there. So is it star free? Listen to learn more! arxiv.org/abs/2508.20157

In Payel's second paper, the authors discover a new isolated dwarf elliptical, contradicting the predictions of the morphology-density relation. How did it get there? 🔭 ☄️
arxiv.org/pdf/2508.20459

Payel's first paper explores the impact of Ly-alpha photos on a potential mode of feedback-free star formation after the birth of the most massive stars and before their deaths as supernovae. 🔭 ☄️
arxiv.org/pdf/2509.02566

Michelle can't get enough of Little Red Dots! When will we know what they are? Listen to episode 20 for more! 🔭 ☄️

Sketch of the proposed hot AGN-dust scenario, both for stellar- dominated (left) and AGN-dominated (right) Optical/UV continuum. The drawing shows the AGn sin a dust free centre, the clumpy torus further out and then the source of the UV and optical coming either from stars alone or stars plus hot AGN dust

Michelle's first paper takes us back to her addiction to Little Red dots. This paper discusses the need for active galactic nuclei at the heart of these puzzling objects. Tune in for more! 🔭 ☄️ arxiv.org/abs/2509.07100

Episode 20 is live! Join Payel and Michelle as they discuss blackholes, ancient galaxies, starless galaxies, star formation and whether life may flourish in the faintest galaxies. Join us on our website, Spotify , Apple or wherever you listen to podcasts 🔭 ☄️

Episode 20 – Dark galaxies, black holes, star formation and life in the faintest galaxies?

In this episode of StarXiv, Michelle and Payel discuss black holes, feedback-free star formation, dark galaxies, runaway dwarf galaxies, and exploring the potential for life in the faintest galaxies.…

A schematic of an interstellar objects orbit through the solar system, complete with a listing of the types of observations we can take of the object (and when we could take them) overlaid at the top.

Michelle's final paper investigates interstellar objects (such as the 3 detected interstellar comets) for signs of alien technosignatures! So far, all 3 objects are comets, but if there were a probe out there, how could we find out? This paper outlines the methods. 🔭 ☄️ arxiv.org/abs/2508.16825

Payel's last paper confirms JWST/NIRSPEC findings of overmassive black holes at high redshift using an independent method relying on photometric variability. Find out more at arxiv.org/abs/2508.15905 🔭 ☄️

It was a really nice paper. Great work!

A labelled polarized light image of the WISPIT-2 protoplanetary disk, In this version, the position of the planet in a gap between the concentric rings can be seen and is highlighted.

This image shows the protoplanetary disk with its 4 concentric rings and gaps all labelled.

Michelle's second paper focuses on the direct detection of a gas giant forming in a multi-ringed protoplanetary disk from the WISPIT survey. This can help us learn about where planets are forming. 🔭 ☄️ arxiv.org/abs/2508.19053

Payel's second paper reveals the potential for high-resolution spectra of M-dwarfs, which make up 75% of all stars in the Milky Way, to reveal finer details of our Galaxy's chemical evolution history. Find out more at arxiv.org/abs/2508.18424 🔭 ☄️

In Payel's first paper, the authors increase the number of local high N/O emitters almost five-fold using the first data release from DESI! Find out more at arxiv.org/abs/2508.11998 🔭 ☄️

Table 1 from the paper which shows the star formation rate of stars within Local open clusters (derived using two different methods), compared with the local star formation rate. The fraction of stars forming in clusters is high, with > 80%!

Michelle's first paper discussed the birth sites of stars. Do they form mostly in embedded clusters, or are they forming unbound across a range of environments? Seems like clustered based on this great paper! arxiv.org/abs/2508.12788 🔭 ☄️

StarXiv: a podcast discussing the latest astronomy papers | Podcast on RSS.com Hello! Welcome to the StarXiv, hosted by Dr Michelle Collins and Dr Payel Das. This is a biweekly podcast that delves into the latest astronomy papers & results from the arXiv. Michelle and Payel are…

You can also subscribe to us on Spotify, Apple Podcasts, RSS or wherever you get your podcasts. rss.com/podcasts/sta...

Can you believe that we've been running this show for nearly a year? Listen to our latest episode, out today! Michelle & Payel cover stellar chemistry, nitrogen rich galaxies, the birth site of Milky Way stars, planets and alien technosignatures. 🔭 ☄️ starxiv.com/2025/09/01/e...

Episode 19 – Peering into the Local Universe, distant blackholes, forming planets and alien signatures

In this episode, Michelle and Payel explore the chemistry of nearby M-dwarf stars and the formation of giant planets at significant distances from their hosts. They discuss supermassive black…

Caption from figure 1 in the paper: Minimum stellar obliquity, Δi, as a function of spectral type. a, Point colors represent the misalignment status of each system (n=49). Dark purple circles are misaligned at the >2𝜎 level, and light blue points show no evidence of misalignment. The yellow star represents the location of the pre-main sequence Sun (which would have corresponded to a spectral type of about K9 at an age of approximately 5 Myr) assuming that the origin of its current obliquity is primordial. Error bars are shown at 1𝜎 confidence. b, Reconstructed distributions of Δi. The light green area shows the Gaussian KDE of the distribution of Δi. The HBM results for the Rayleigh distribution generated with a log-Uniform prior (labeled as ‘log-U Pr’) are represented by the dotted dark blue line, and the same model fit with a Truncated Gaussian prior (‘TG Pr’) is shown by the solid light-blue line. The Gaussian distribution model fits produced with a log-Uniform prior and Truncated Gaussian prior are plotted as the purple dashed and solid lines, respectively. The Truncated Gaussian model fit generated with a Uniform prior (‘U Pr’) is shown in dark teal. c, Best-fit HBM results using a Beta distribution for the minimum obliquities of a sample of 25 hot (‘H’) and 22 warm (‘W’) Jupiter systems15 also determined using a similar Δi methodology, shown here for comparison. Here, ‘log-N Pr.’ represents model fits produced with a log-Normal prior.

Michelle's final paper looked at the (mis)alignment between stars and their planetary systems. The work combines ALMA, TESS and K2 data to study the alignment of stars and their protoplanetary disks, with the goal of finding out if misalignments could be primordial. 🔭 ☄️ arxiv.org/abs/2508.06488

The link from the website was temporarily down, but it is now restored! For those of you that prefer the website to other apps 🔭🧪☄️

Figure 1. Mean [Al/Fe] versus mean [Fe/H] of primordial populations in Galactic GCs. Their associated standard deviations are shown as error bars. The black dotted line indicates the metallicity of [Fe/H]=−1.5. GCs with [Fe/H]<−1.5 are not suitable for our chemically based classification (grey region). The black dashed line separates chemically classified in-situ and accreted clusters. In comparison, MKH classification is also shown (in-situ: purple, accreted: red).

Nicole talked about this letter’s new way to classify globular clusters - not by orbits, but by chemistry. Above [Fe/H] ≈ –1.5, [Al/Fe] splits in-situ from accreted GCs. Primordial stars in accreted GCs are Al- and Mg-poor - signs of slower enrichment.
arxiv.org/abs/2508.00526 🔭☄️