Resumen: Protoneutron stars, highly compact objects formed in the core of exploding supernovae (SNe), are powerful sources of axionlike particles (ALPs). In the SN core, ALPs are dominantly produced via nucleon-nucleon bremsstrahlung and pion conversion, resulting in an energetic ALP spectrum peaked at energies O(100) MeV. In this work, we revisit the diffuse ALP background, produced from all past core-collapse supernovae, and update the constraints derived from -LAT observations. Assuming the maximum ALP-nucleon coupling allowed by the SN 1987A cooling, we set the upper limit gaγγ≲2×10−13 GeV−1 for ALP mass ma≲10−10 eV, which is approximately a factor of two improvement with respect to the existing bounds. On the other hand, for ma≳10−10 eV, we find that including pion conversion strengthens the bound on gaγγ, approximately by a factor of two compared to the constraint obtained from bremsstrahlung alone. Additionally, we present a sensitivity study for future experiments such as AMEGO-X, e-ASTROGAM, GRAMS-balloon, GRAMS-satellite, and MAST. We find that the expected constraint from MAST would be comparable to -LAT bound. However, SN 1987A constraint remains one order of magnitude stronger as compared to the bound derived from the current and future gamma-ray telescopes. Idioma: Inglés DOI: 10.1103/d194-7t6x Año: 2025 Publicado en: Physical Review D 112, 1 (2025), 015006 [10 pp.] ISSN: 2470-0010 Financiación: info:eu-repo/grantAgreement/ES/AEI/PID2021-126078NB-C21 Financiación: info:eu-repo/grantAgreement/EUR/COST/CA21106-COSMIC Wispers Financiación: info:eu-repo/grantAgreement/EC/H2020/788781/EU/Towards the detection of the axion with the International Axion Observatory/IAXOplus Financiación: info:eu-repo/grantAgreement/ES/MINECO/PID2019-108122GB-C31 Financiación: info:eu-repo/grantAgreement/ES/NextGenerationEU/INVESTIGO-095-28 Tipo y forma: Article (Published version) Área (Departamento): Área Astronomía y Astrofísica (Dpto. Física Teórica) Área (Departamento): Área Física Atóm.Molec.y Nucl. (Dpto. Física Teórica)