https://astro.theoj.org/ The Open Journal of Astrophysics is an arXiv overlay journal providing open access to peer-reviewed research in astrophysics and cosmology. en Thu, 04 Jun 2026 11:06:00 +0000 The "Reduced Speed of Light" approximation in cosmological simulations can lead to photon non-conservation, and while some missing photons can be counted, adding them back is challenging. https://doi.org/10.33232/001c.162879 https://astro.theoj.org/article/162879-photon-non-conservation-in-the-reduced-speed-of-light-approximation-and-how-to-almost-fix-it Wed, 03 Jun 2026 05:08:00 +0000 The thermal Sunyaev-Zel'dovich effect and constrained simulations are used to analyze the thermal pressure of ionized gas in galaxy clusters and produce a set of digital twins for cosmological study https://doi.org/10.33232/001c.162811 https://astro.theoj.org/article/162811-validating-digital-twins-of-the-local-universe-with-the-thermal-sunyaev-zel-dovich-signal Tue, 02 Jun 2026 07:48:00 +0000 A model to understand the role of nozzle shock in the circularization of stellar debris during a tidal disruption event when a star approaches a supermassive black hole (SMBH) https://doi.org/10.33232/001c.162785 https://astro.theoj.org/article/162785-resolving-the-debate-about-nozzle-shocks-in-tidal-disruption-events Tue, 02 Jun 2026 07:27:00 +0000 The study suggests that X-ray transients, similar to tidal disruption events, are produced in eccentric stellar-compact object binaries, with their frequency gradually increasing over time. https://doi.org/10.33232/001c.162784 https://astro.theoj.org/article/162784-transient-x-ray-sources-as-extremely-eccentric-mass-transfer-binaries-with-compact-companions Tue, 02 Jun 2026 07:14:00 +0000 This article explores how uncertainties in binary formation affect the cross-correlation signal between gravitational wave events and galaxy catalogues, finding that time-delay distribution significantly impacts the signal. https://doi.org/10.33232/001c.162783 https://astro.theoj.org/article/162783-the-impact-of-the-formation-channel-on-gravitational-wave-galaxy-cross-correlations Tue, 26 May 2026 06:56:00 +0000 Testing the accuracy of stellar age estimates from recent catalogs, finding that spectroscopic metallicities provide reliable subgiant ages, while photometric ages underestimate uncertainties. Accurate chemical abundance measurements are essential. https://doi.org/10.33232/001c.162534 https://astro.theoj.org/article/162534-how-precisely-can-we-measure-the-ages-of-subgiant-and-giant-stars Tue, 26 May 2026 06:35:00 +0000 This study explores the use of control variates in cosmological simulations, introducing a new 'shifted control variate' that improves precision and enables accurate bispectrum emulators, aiding in cosmology modeling. https://doi.org/10.33232/001c.162533 https://astro.theoj.org/article/162533-control-variates-from-eulerian-and-lagrangian-perturbation-theory-application-to-the-bispectrum Mon, 25 May 2026 07:21:00 +0000 The study uses machine learning to detect unrecognized blends in deep ground-based imaging, improving sample purity and potentially enhancing accuracy in future cosmological surveys. https://doi.org/10.33232/001c.162504 https://astro.theoj.org/article/162504-catalog-based-detection-of-unrecognized-blends-in-deep-optical-ground-based-imaging Mon, 25 May 2026 07:03:00 +0000 This study presents evidence that "black hole stars" (BH*), early stages of black hole growth, power Little Red Dots (LRDs) and every massive black hole may have been a BH* https://doi.org/10.33232/001c.162505 https://astro.theoj.org/article/162505-little-red-dot-host-galaxy-black-hole-star-a-gas-enshrouded-heart-at-the-center-of-every-little-red-dot Fri, 22 May 2026 08:48:00 +0000 A demonstration of the use of international Low Frequency Array (LOFAR) stations in tracking and characterizing pulsars, providing new insights into these neutron stars' emission properties. https://doi.org/10.33232/001c.162455 https://astro.theoj.org/article/162455-pulsar-timing-solutions-for-17-pulsars-at-150-mhz-from-the-irish-lofar-station