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Weekly Update from the Open Journal of Astrophysics – 18/10/2025

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , , , , , , , , , on October 18, 2025 by telescoper

It’s time once again for the usual Saturday update of the week’s new papers at the Open Journal of Astrophysics. Since the last update we have published four  more papers, which brings the number in Volume 8 (2025) up to 156, and the total so far published by OJAp up to 391.

I’d like to encourage people to follow our feed on the Fediverse via Mastodon (where I announce papers as they are published, including the all-important DOI) so this week I’ll include links to each announcement there.

The first paper to report is “Shot noise in clustering power spectra” by Nicolas Tessore (University College London, UK) and Alex Hall (University of Edinburgh, UK). This was published in the folder Cosmology and NonGalactic Astrophysics on Tuesday October 14th 2025. This presents a discussion of the effects of ‘shot noise’, an additive contribution due to degenerate pairs of points, in angular galaxy clustering power spectra. Here is a screen grab of the overlay:

You can find the officially accepted version of the paper here. The Mastodon announcement is here:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "Shot noise in clustering power spectra" by Nicolas Tessore (University College London, UK) and Alex Hall (University of Edinburgh, UK)

doi.org/10.33232/001c.145919

October 14, 2025, 7:07 am 2 boosts 0 favorites

Next one up is “The Giant Arc – Filament or Figment?” by Till Sawala and Meri Teeriaho (University of Helsinki, Finland). This paper discusses the abundance of large arc-like structures formed in the standard cosmological model, with reference to the “Giant Arc” identified in MgII absorption systems. It was published on Wednesday October 15th in the folder Cosmology and NonGalactic Astrophysics. The overlay is here:

The officially accepted version of this paper can be found on the arXiv here and the Mastodon announcement is here:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "The Giant Arc – Filament or Figment?" by Till Sawala and Meri Teeriaho (University of Helsinki, Finland)

doi.org/10.33232/001c.145931

October 15, 2025, 6:33 am 2 boosts 3 favorites

 

The third paper this week,  published on Monday 6th October, is “Detecting wide binaries using machine learning algorithms” by Amoy Ashesh, Harsimran Kaur and Sandeep Aashish (Indian Institute of Technology, Patna, India). This was published on Friday 17th October (yesterday) in the folder Astrophysics of Galaxies. It presents a method for detecting wide binary systems in Gaia data using machine learning algorithms.

The overlay is here:

 

You can find the officially accepted version of this paper on arXiv here. The announcement on Mastodon is here:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "Detecting wide binaries using machine learning algorithms" by Amoy Ashesh, Harsimran Kaur and Sandeep Aashish (Indian Institute of Technology, Patna, India)

doi.org/10.33232/001c.146027

October 17, 2025, 6:55 am 0 boosts 0 favorites

The last one this week is “Learned harmonic mean estimation of the Bayesian evidence with normalizing flows” by Alicja Polanska & Matthew A. Price (University College London, UK), Davide Piras (Université de Genève, CH), Alessio Spurio Mancini (Royal Holloway, London, UK) and Jason D. McEwen (University College London). This one was also published on Friday 17th October, but in the folder Instrumentation and Methods for Astrophysics; it presents a new method for estimating Bayesian evidence for use in model comparison, illustrated with a cosmological example.

The corresponding overlay is here:

 

You can find the officially accepted version on arXiv here. The Mastodon announcement is here:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "Learned harmonic mean estimation of the Bayesian evidence with normalizing flows" by Alicja Polanska & Matthew A. Price (University College London, UK), Davide Piras (Université de Genève, CH), Alessio Spurio Mancini (Royal Holloway, London, UK) and Jason D. McEwen (University College London)

doi.org/10.33232/001c.146026

October 17, 2025, 7:06 am 0 boosts 0 favorites

That concludes the papers for this week. With two weeks to go I think we might reach the 400 total by the end of October.

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Weekly Update from the Open Journal of Astrophysics – 19/07/2025

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , , , , , , , , , , , , , , , on July 19, 2025 by telescoper

It’s Saturday morning again, so it’s time again for an update of papers published at the Open Journal of Astrophysics. Since the last update we have published six new papers, which brings the number in Volume 8 (2025) up to 98, and the total so far published by OJAp  up to 333. I expect we’ll pass the century for this year sometime next week.

The papers published this week, with their overlays, are as follows.  You can click on the images of the overlays to make them larger should you wish to do so.

The first paper to report is “Reconstructing Galaxy Cluster Mass Maps using Score-based Generative Modeling” by Alan Hsu (Harvard), Matthew Ho (CMU), Joyce Lin (U. Wisconsin-Madison), Carleen Markey (CMU), Michelle Ntampaka (STScI), Hy Trac (CMU) & Barnabás Póczos (CMU), all based in the USA. This paper was published on 14th July 2025 in the folder Cosmology and NonGalactic Astrophysics. It presents a diffusion-based generativbe AI model for reconstructing density profiles for galaxy clusters from observational data.

The overlay is here:

The officially-accepted version can be found on arXiv here.

The second and third papers are related. They were both published on 14th July in the folder Cosmology and NonGalactic Astrophysics.

The first of the pair is “J-PLUS: Tomographic analysis of galaxy angular density and redshift fluctuations in Data Release 3. Constraints on photo-z errors, linear bias, and peculiar velocities” by Carlos Hernández-Monteagudo (IAC, Tenerife, Spain) and 21 others. This presents an analysis of the Javalambre Photometric Local Universe Survey (J-PLUS) in redshift slices with a discussion of prospects for extracting cosmological information. The overlay is here:

 

You can find the final version of the manuscript on arXiv here.

The second of this pair is “The J-PLUS collaboration. Additive versus multiplicative systematics in surveys of the large scale structure of the Universe” by Carlos Hernández-Monteagudo (IAC) and 21 others (the same authors as the previous paper).  This paper presents an analysis of systematic effects in the Javalambre Photometric Local Universe Survey (J-PLUS), and a new model for handling such errors in this and other cosmological surveys. The overlay for this paper is here:

You can find the officially accepted version of this paper on arXiv here.

The fourth paper this week is “Why Machine Learning Models Systematically Underestimate Extreme Values” by Yuan-Sen Ting (Ohio State University). This one was published on July 16th in the folder marked Instrumentation and Methods for Astrophysics.  This paper presents a theoretical framework for understanding and addressing a bias that suppresses the dynamic range of variables in applications of machine learning to astronomical data analysis. Here is the overlay:

You can find the officially accepted version of this paper on arXiv here.

The penultimate article for this week is “Bridging Machine Learning and Cosmological Simulations: Using Neural Operators to emulate Chemical Evolution” by Pelle van de Bor, John Brennan & John A. Regan (Maynooth University) and Jonathan Mackey (Dublin Institute for Advanced Studies), all based in Ireland. This paper uses machine learning, in the form of neural operators, to emulate the Grackle method of solving non-equilibrium chemistry equations in cosmological hydrodynamic simulations and was published on 16th July also in the folder Instrumentation and Methods for Astrophysics. The overlay is here:

The final, accepted version of the paper is on arXiv here.

The last article published this week is “Astronomical Cardiology: A Search For Heartbeat Stars Using Gaia and TESS” by Jowen Callahan, D. M. Rowan, C. S. Kochanek and K. Z. Stanek (all of Ohio State University, USA). This paper presents a study of a sample of 112 new spectroscopic binaries called hearbeat stars (because their light curves resemble electrocardiagrams). It was published on 16th July 2025 in the folder marked Solar and Stellar Astrophysics. The overlay is here:

You can find the officially-accepted version on arXiv here.

And that’s all the papers for this week. I’ll do another update next Saturday.

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Weekly Update from the Open Journal of Astrophysics – 24/05/205

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , , , , , , on May 24, 2025 by telescoper

It’s  time once again for the regular Saturday update of papers published during the past week at the Open Journal of Astrophysics. Since the last update we have published three new papers, which brings the number in Volume 8 (2025) up to 62 and the total so far published by OJAp up to 297.

In chronological order of publication, the three papers published this week, with their overlays, are as follows. You can click on the images of the overlays to make them larger should you wish to do so.

The first paper to report is: “Jet-shaped filamentary ejecta in common envelope evolution” by Ron Schreier, Shlomi Hillel and Noam Soker (Technion, Haifa, Israel). This paper, which was published on Monday May 19th 2025 in the folder High-Energy Astrophysical Processes, presents three-dimensional hydrodynamical simulations of common envelope evolution of a neutron star inside the envelope of a rotating red supergiant with Rayleigh-Taylor instabilities forming filamentary ejecta.

The overlay is here:

You can find the officially accepted version on arXiv here.

Second one up is “Weighing The Options: The Unseen Companion in LAMOST J2354 is Likely a Massive White Dwarf” by M. A. Tucker, A. J. Wheeler & D. M. Rowan (Ohio State University, USA) and M. E. Huber (U. Hawaii, USA). This paper was published on Tuesday 20th May 2025 in the folder for Solar and Stellar Astrophysics. It discusses a spectroscopic study of the binary system LAMOST J235456.73+335625 (J2354) with a discussion of the implications for the nature of the dark component.

The overlay is here:

 

You can find the officially-accepted version of the paper on arXiv here.

The third and last paper of the week, published on Thursday May 22nd 2025, also in the folder Solar and Stellar Astrophysics, is “How to use Gaia parallaxes for stars with poor astrometric fits” by Kareem El-Badry (Caltech, USA).  This paper presents a method for extracting reasonable estimates of stellar parallaxes from Gaia data when the overall astrometric solution is unreliable due to errors and noise

Here is the overlay:

You can find the officially accepted version of this paper on arXiv here.

That’s all the papers for this week. Looking at the publishing workflow, I expect we will pass the 300 mark next week. We’ll see when I post the next update next Saturday.

 

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Farewell to Gaia

Posted in The Universe and Stuff with tags , , , , on January 15, 2025 by telescoper
Artist impression of ESA’s Gaia satellite observing the Milky Way. The background image of the sky is compiled from data from more than 1.8 billion stars. Spacecraft: ESA/ATG medialab; Milky Way: ESA/Gaia/DPAC. Acknowledgement: A. Moitinho

Today (15th January 2025) marks the end of an era. The European Space Agency’s Gaia spacecraft stops taking data today as it is running out of the gas propellant needed to keep it scanning the sky. The spacecraft was launched on 19 December 2013 so has been operating for just over 11 years.

For those of you not in the know, Gaia is a global space astrometry mission, whose mission was to make the largest, most precise three-dimensional map of our Galaxy by surveying more than a billion stars. Gaia was to monitor each of its target stars about 70 times over a five-year period. Alongside this core mission, it has also discovered hundreds of thousands of new celestial objects, such as extra-solar planets and brown dwarfs, and observed hundreds of thousands of asteroids within our own Solar System.

Gaia is creating an extraordinarily precise three-dimensional map of more than a thousand million stars throughout our Galaxy (The Milky Way) and beyond, mapping their motion, luminosity, temperature and chemical composition as well as any changes in such properties. This huge stellar census will provide the data needed to tackle an enormous range of important problems related to the origin, structure and evolutionary history of our Galaxy. Gaia does this by repeatedly measuring the positions of all objects down to an apparent magnitude of 20. A billion stars is about 1% of the entire stellar population of the Milky Way.

For the brighter objects, i.e. those brighter than magnitude 15, Gaia  measures their positions to an accuracy of 24 microarcseconds, comparable to measuring the diameter of a human hair at a distance of 1000 km. Distances of relatively nearby stars are measured to an accuracy of 0.001%. Even stars near the Galactic Centre, some 30,000 light-years away, have their distances measured to within an accuracy of 20%.

The huge quantity of high-precision data Gaia has produced constitutes a tremendously influential resource for astronomical research. The fourth data release from Gaia, DR4, is in the pipeline for completion soon but the final data release (DR5) will take some years to appear, so this is by no means the last we will hear from Gaia, but the end of observations does close a significant chapter. Its legacy will be immense.

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Four New Publications at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , , , , , on November 9, 2024 by telescoper

Once again it’s time for a quick update of activity at the Open Journal of Astrophysics. Since the last update a week ago we have published  four papers, which takes the count in Volume 7 (2024) up to 102 and the total published altogether by OJAp up to 217.   This means not only that we have reached a century for the year but also that so far in 2024 we have published more than double the number of papers that we published in all of 2023. I blogged about the significance of the figure 217 here.

In chronological order, the four papers published this week, with their overlays, are as follows. You can click on the images of the overlays to make them larger should you wish to do so.

First one up is “A generative model for Gaia astrometric orbit catalogs: selection functions for binary stars, giant planets, and compact object companions” by Kareem El-Badry (Caltech, USA), Casey Lam (Carnegie Observatories), Berry Holl & Jean-Louis Halbwachs (U. Geneva), Hans-Walter Rix (MPA Heidelberg, Germany), Tsevi Mazeh (Tel Aviv, Israel) and Sahar Shahaf (Weizmann Institute of Science, Israel). This one is in the folder Solar and Stellar Astrophysics. The paper presents a forward method for estimating the selection function (i.e. the probability of a system with a given set of parameters being included in a catalog). It was published on November 4th 2024.

Here is a screen grab of the overlay, which includes the abstract:

 

You can find the officially accepted version of the paper on the arXiv here.

The second paper to announce, published on 5th November 2024. is “Primordial magnetogenesis in a bouncing model with dark energy” by Marcus V. Bomfim (Rio de Janeiro, Brazil), Emmanuel Frion (Western U. Canada), Nelson Pinto-Neto (Espírito Santo, Brazil), and Sandro D. P. Vitenti (Paraná, Brazil). This paper, in the section on Cosmology and NonGalactic Astrophysics, presents a discussion of the possible generation of magnetic fields on cosmological scales by in a model involving a scalar field coupled to electromagnetism

You can see the overlay here:

 

 

 

The accepted version of this paper can be found on the arXiv here.

The third paper, published on 6th November 2024 in the folder marked Astrophysics of Galaxies, is called  “Evidence for large scale compressible turbulence in the ISM of CSWA13, a star-Forming Lensed Galaxy at z = 1.87 with outflowing wind” by Itzhak Goldman (Tel Aviv, Israel). It presents a statistical analysis of the spatial distribution and kinematics of nebular gas with discussion of the nature of the turbulence present.

Here is the overlay

 

 

The final version accepted on arXiv is here.

Last in this batch is “Star formation in the high-extinction Planck cold clump PGCC G120.69+2.66” by Anlaug Amanda Djupvik (Aarhus, Denmark), João L. Yun (Lisbon, Portugal), and Fernando Comerón (ESO, Garching, Germany). It was published on 7th November 2024 in the folder marked Astrophysics of Galaxies. The paper uses imaging and spectroscopy  information to identify sites of star formation in a molecular cloud. This is the overlay:

You can find the official accepted version on the arXiv here.

That’s all for now. I will post another update in a week.

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Sun-like Stars with Hidden Companions

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , on July 16, 2024 by telescoper

I usually only do updates at weekends about papers published in the Open Journal of Astrophysics but I’m making an exception today because a paper we published yesterday is making some waves that I think are worth propagating. The paper is called “A population of neutron star candidates in wide orbits from Gaia astrometry” and the first author is Kareem El-Badry of Caltech (USA); his institution have put out a press release to go with the paper which you an read for more details. They key point is that these are main sequence stars with (probably) neutron star companions and nobody really knows how such systems formed. The paper is also yet another illustration of the amazingly rich source of discovery data that is the European Space Agency’s Gaia mission.

The press release also contains some snazzy graphics, such as this:

The press release explains

The new study, which includes a team of co-authors from around the world, was published in The Open Journal for Astrophysics. Data from several ground-based telescopes, including the W. M. Keck Observatory on Maunakea, Hawai‘i; La Silla Observatory in Chile; and the Whipple Observatory in Arizona, were used to follow up the Gaia observations and learn more about the masses and orbits of the hidden neutron stars.

It is very gratifying to see one of our papers gaining such traction. It also exemplifies something that has struck me recently. Obviously, when we started the Open Journal of Astrophysics I really had no idea how it would go, but one thing that has surprised me (in a pleasant way) is how many articles we are getting from authors based in high-profile US institutions, such as Caltech, Harvard, Princeton and Berkeley (among others). I always assumed that such institutions were rich enough not to be worried by the cost of Article Processing Charges and, being based in America, the authors would in any case be used to paying page charges for the Astrophysical Journal which has been standard practice for ages. Whatever the reason, it sends a great message to the community to see these leading institutions going via the Diamond Open Access route. I hope this provides even more evidence to persuade even more authors that OJAp is a serious journal!

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Three New Publications at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , on May 18, 2024 by telescoper

It’s time once more for the usual  Saturday roundup of business at the  Open Journal of Astrophysics. The latest batch of publications consists of three papers, taking the count in Volume 7 (2024) up to 39 and the total published by OJAp up to 154. We’re still on track to publish around 100 papers this year, compared to last year’s 50.

All three of this week’s papers involve use of data from the European Space Agency’s Gaia mission, which is proving an immensely rich resource for astrophysics.

First one up is “Asymmetric Drift Map of the Milky Way Disk Populations between 8 -16 kpc with LAMOST and Gaia datasets” which is by  Xin Li (Nanchong, China), Peng Yang (Chengdu, China) , Hai-Feng Wang (Nanchong, China), Qing Li (Jiangmen, China), Yang-Ping Luo (Nanchong, China), Zhi-Quan Luo (Nanchong, China), Guan-Yu Wang (Nanchong, China). This is a study  of the asymmetric drift, the difference of the local circular speed and the mean rotational speed of the stellar population, for various stellar populations in the Milky Way. It is in the folder marked Astrophysics of Galaxies and was published on Tuesday 14th May 2024.

Here is a screen grab of the overlay, which includes the abstract:

 

 

You can read the paper directly on arXiv here.

The second paper to announce is “On the formation of a 33 solar-mass black hole in a low-metallicity binary” by Kareem El-Badry (Caltech, USA). It discusses theoretical models for the formation of a black hole in a particular binary system discovered in Gaia data.

This one is in the folder Solar and Stellar Astrophysics and was published on 16th May 2024. The overlay looks like this:

 

 

You can read this paper directly on the arXiv here.

The last paper of this batch, also in the in the folder Solar and Stellar Astrophysics, is entitled “Compact Binary Formation in Open Star Clusters II: Difficulty of Gaia NS formation in low-mass star clusters”  and it presents a discussion of the formation of binary neutron stars and black holes found in Gaia data based on their orbital properties. It was published on Friday May 17th 2024 (i.e. yesterday). The authors are Ataru Tanikawa (Fukui University, Japan), Long Wang (Sun-yat Sen University, China) and  Michiko S. Fujii (Tokyo University, Japan).

Here is a screengrab of the overlay:

 

 

To read the accepted version of this on the arXiv please go here.
That’s all for now. Another update next week!

 

 

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Gaia Focused Product Release

Posted in The Universe and Stuff with tags , on October 10, 2023 by telescoper

I almost forgot about this but some new data from the ESA Gaia mission will be announced this afternoon at 3pm CEST*, though it seems to be a bit late. This announcement concerns the latest batch of Gaia Focused Product (Gaia FPR) data. The release consists in the publication of 5 papers on specific aspects of the mission and the associated data.  You can watch here. Due to technical problems it has been delayed by 30 minutes and there is a new link:

While waiting to view the announcement, you may wish to familiarize yourself with the mission by reading this list of Top Ten Gaia Facts.

*Coles Extended Sabbatical Time

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The Decline of the Milky Way’s Rotation

Posted in The Universe and Stuff with tags , , , , on September 28, 2023 by telescoper

I just noticed an interesting item on the ESA website about results described in a paper by Jiao et al. (on the arXiv here) relating to the rotation of the Milky Way as determined by Gaia’s Data Release 3.

The key result in the paper is summarized in this diagram:

A galaxy rotation curve like this is a diagnostic of the radial distribution of mass. If all the mass were concentrated at the centre, the galaxy would behave like the Solar System (in which most of the mass is contained within the Sun). In such a Keplerian profile the rotation speed falls off with distance, just as the outer planets move more slowly in their orbits than the inner ones. According to modern cosmology, however, there is dark matter not concentrated in the centre, in which case the rotation curve does not decline with distance and may even rise. According to theory, at large distances, the rotation curve of a spiral galaxy should be roughly flat.

The new results seem to contract this notion. The Figure shows a rotation curve that declines for distances about 15 kpc from the Galactic Centre; for reference the Sun orbits at a radius of about 10 kpc.

One of the problems in constructing a rotation curve of our own Galaxy is that we are inside it so it isn’t possible to make measurements across the entire system like we can with other galaxies. Using the Gaia measurements and a plausible model, however, the authors find much less dark matter than anticipated.

With a bit of extrapolation using a model, this measurement leeds to a reduction in the estimated total mass of the Milky Way. The value usually bandied about is around 1012 Solar Masses, while the new measurements imply a much lower mass of about 2 × 1011 Solar Masses.

A factor of five reduction is quite a dramatic change and I’m sure this result will be challenged by those of an orthodox persuasion while also providing encouragement to dark matter sceptics. We’ll just have to wait and see how this pans out.

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New Publication at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , on February 3, 2023 by telescoper

The articles are coming in thick and fast at the Open Journal of Astrophysics. and why trying to get them refereed and published as quickly as we can. It’s time to announce yet another paper. This one was published officially yesterday (2nd February 2023) but I just found time to post about it here today before I go to my 9am tutorial.

The latest paper is the 4th paper in Volume 6 (2023) as well as the 69th in all. This one is in the Astrophysics of Galaxies folder.

The latest publication is entitled “Wide Binaries from GAIA EDR3: preference for GR over MOND?”.  The authors of this paper,  Charalambos Pittordis and Will Sutherland, are both based at Queen Mary, University of London. We published a related paper last month.

Here is a screen grab of the overlay which includes the  abstract:

 

You can click on the image to make it larger should you wish to do so. You can find the officially accepted version of the paper on the arXiv here.

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