The Australia Today’s Post

📃Scientific paper: On Cepheid distances in the $H_0$ measurement Abstract: Classical Cepheids were the first stellar standard candles and have played a crucial role for astronomical distance measurements ever since the discovery of the Leavitt law (period-luminosity relation). Enormous improvements in distance accuracy have been achieved since Hertzsprung's first application of Leavitt's law to measure the distance to the Small Magellanic Cloud in 1913, notably in very recent years thanks to a large data set of highly accurate space astrometry from the ESA mission Gaia. Complemented by homogeneous space photometry, Cepheids enable the most accurate distance estimates to galaxies hosting type-Ia supernovae up to approximately 70 Mpc distant. Here, I review the history of Cepheid distance measurements, open questions on the side of stellar astrophysics, and recent studies seeking to quantify and mitigate systematics with a view to further improve the accuracy on the Hubble constant. For example, the recently launched James Webb Space Telescope will enhance precision due to 4x lower sensitivity to source blending in crowded regions and greater sensitivity in dust-insensitive infrared bands. Future 30m-class telescopes could in principle further improve Cepheid distance measurements towards the Hubble flow, if technical challenges related to a continuously evolving instrument can be overcome. ;Comment: 20 pages plus references. Finalized in early October 2023. To appear as a chapter in the Book "The Hubble Constant Tension", edited by E. Di ... Continued on ES/IODE ➡️ https://etcse.fr/eB6Yl ------- If you find this interesting, feel free to follow, comment and share. We need your help to enhance our visibility, so that our platform continues to serve you.

📃Scientific paper: Precision spectrophotometry for PNLF distances: the case of NGC 300 Abstract: The Multi-Unit Spectroscopic Explorer (MUSE) has enabled a renaissance of the planetary nebula luminosity function (PNLF) as a standard candle. In the case of NGC 300, we learned that the precise spectrophotometry of MUSE was crucial to obtain an accurate PNLF distance. We present the advantage of the integral field spectrograph compared to the slit spectrograph in delivering precise spectrophotometry by simulating a slit observation on integral field spectroscopy data. We also discuss the possible systematic shift in measuring the PNLF distance using the least-square method, especially when the PNLF cutoff is affected by small number statistics. ;Comment: 5 pages, 4 figures, Submitted to the Proceedings of IAU Symposium 384: Planetary Nebulae: a Universal Toolbox in the Era of Precision Astrophysics Continued on ES/IODE ➡️ https://etcse.fr/uwq5O ------- If you find this interesting, feel free to follow, comment and share. We need your help to enhance our visibility, so that our platform continues to serve you.

A 60-Earth Mass planet discovered by PARAS-2 attached to PRL's 2.5m Mt. Abu telescope PRL scientists have discovered a 60-Earth mass planet around a Sun-like star, which has an orbital period of 5 days and a bulk density of 2.5 g/cc, using PARAS-2 (PRL Advanced Radial-velocity Abu-sky Search) high-resolution spectrograph connected to the PRL's 2.5m telescope at Mt. Abu Observatory in Gurushikhar. This exoplanet is known as TOI 6651b and this discovery challenges the planet formation theories because of its high bulk density and very short orbital period. PARAS-2 is indigenously designed and built at PRL. It is the highest resolution (100,000) optical fibre stabilized spectrograph in Asia. This is the fourth planet discovered by PRL's scientists and is the first one using the recently commissioned 2.5m telescope. [This result entitled, Discovery and characterization of a dense sub-Saturn TOI-6651b has been published in the journal Astronomy and Astrophysics. https://lnkd.in/dxG5zHN4] ISRO - Indian Space Research Organization

📃Scientific paper: Plasma Radiation Model of Fast Radio Bursts from Magnetars Abstract: We propose a novel idea for the coherent intense millisecond radio emission of cosmic fast radio bursts (FRBs), which have recently been identified with flares from a magnetar. Motivated by the conventional paradigm of Type III solar radio bursts, we will explore the emission of coherent plasma line radiation at the electron plasma frequency and its harmonic as potential candidates of the coherent FRB emissions associated with magnetar flares. We discuss the emissions region parameters in relativistic strongly magnetized plasmas consisting of electrons, positrons and protons. The goal is to make observable predictions of this model to confront the multi-wavelength observations of FRBs from magnetars. These results will impact both observational radio astronomy and space-based astrophysics ;Comment: 13 pages 7 figures Continued on ES/IODE ➡️ https://etcse.fr/QbHO ------- If you find this interesting, feel free to follow, comment and share. We need your help to enhance our visibility, so that our platform continues to serve you.

A 60-Earth Mass planet discovered by PARAS-2 attached to PRL's 2.5m Mt. Abu telescope PRL scientists have discovered a 60-Earth mass planet around a Sun-like star, which has an orbital period of 5 days and a bulk density of 2.5 g/cc, using PARAS-2 (PRL Advanced Radial-velocity Abu-sky Search) high-resolution spectrograph connected to the PRL's 2.5m telescope at Mt. Abu Observatory in Gurushikhar. This exoplanet is known as TOI 6651b and this discovery challenges the planet formation theories because of its high bulk density and very short orbital period. PARAS-2 is indigenously designed and built at PRL. It is the highest resolution (100,000) optical fibre stabilized spectrograph in Asia. This is the fourth planet discovered by PRL's scientists and is the first one using the recently commissioned 2.5m telescope. [This result entitled, Discovery and characterization of a dense sub-Saturn TOI-6651b has been published in the journal Astronomy and Astrophysics. https://lnkd.in/ddMrcJxC] ISRO - Indian Space Research Organization

📃Scientific paper: Two 100 TeV neutrinos coincident with the Seyfert galaxy NGC 7469 Abstract: In 2013, the IceCube collaboration announced the detection of a diffuse high-energy astrophysical neutrino flux. The origin of this flux is still largely unknown. The most significant individual source is the close-by Seyfert galaxy NGC 1068 at 4.2-sigma level with a soft spectral index. To identify sources based on their counterpart, IceCube releases realtime alerts corresponding to neutrinos with a high probability of astrophysical origin. We report here the spatial coincidence of two neutrino alerts, IC220424A and IC230416A, with the Seyfert galaxy NGC 7469 at a distance of 70 Mpc. We evaluate, a-posteriori, the chance probability of such a coincidence and discuss this source as a neutrino emitter based on its multi-wavelength properties and in comparison to NGC 1068. To calculate the chance coincidence considering neutrino emission from a specific source population, we perform a Goodness-of-Fit test with a test statistic derived from a likelihood ratio that includes the neutrino angular uncertainty and the source distance. We apply this test first to a catalog of AGN sources and second to a catalog of Seyfert galaxies only. Our a-posteriori evaluation excludes the chance coincidence of the two neutrinos with the Seyfert galaxy NGC 7469 at 3.3-sigma level. To be compatible with non-detections of TeV neutrinos, the source would need to have a hard spectral index. ;Comment: 9 pages, 6 figures, submitted to Astronomy & Astrophysics Continued on ES/IODE ➡️ https://etcse.fr/5sDVr ------- If you find this interesting, feel free to follow, comment and share. We need your help to enhance our visibility, so that our platform continues to serve you.

My first paper is now available on arXiv. It presents the results obtained in my Master's thesis. Title: Superradiance of charged black holes embedded in dark matter halos. Abstract:Astrophysical environments are ubiquitous in the Universe; from accretion disks around black holes to galactic dark matter halos, distributions of astrophysical material veil the vast majority of Cosmos. Including environmental effects in strong-field gravity and astrophysics is, therefore, a rather tantalizing task in the quest for novel gravitational-wave phenomena. Here, we examine how environments affect the high-energy process of superradiance. In particular, we study the amplification of charged scalar waves under the expense of the electrostatic energy contained in a charged black hole that is embedded in an observationally-motivated, and qualitatively generic, dark matter halo. We find that the superradiant amplification of massless charged scalar fields scattering off environmentally-enriched charged black holes can be equally efficient to those occurring in vacuum charged black holes. This occurs due to the fact that the sole interplay between the scalar wave and the black hole is the electromagnetic interaction. The addition of mass on the charged scalar waves leads to a rapid suppression of superradiant amplification. This transpires to a great extent due to the `friction' that the mass introduces to the black hole potential. Nevertheless, for sufficiently large scalar masses, the amplification factors can be also subdominantly affected by the compactness of the halo. This occurs because the gravitational interaction between the dense halo and the wave's mass grows, thus further suppressing the superradiant amplification. https://lnkd.in/e9VjaA6Y

Professor Mayank Vahia, a true titan in #astrophysics and #astronomy. Completed #PhD from the esteemed #UniversityofMumbai. His scholarly journey has been nothing short of remarkable, from his impactful tenure as a #professor at Tata Institute of Fundamental Research (#TIFR), #Mumbai, to his current role as the esteemed Dean of the School of #Mathematical #Sciences at #NMIMS, Mumbai. Professor Vahia's dedication to advancing our understanding of the #cosmos knows no bounds. His interests span the vast expanse of the #universe, from the intricate workings of astrophysics to the fascinating tapestry of astronomical #history. His passion for the cosmos knows no bounds, diving deep into astrophysics and unravelling the threads of astronomical #history. But what truly makes him shine is his dedication to making science accessible to all, bridging the gap between #science and #society. #ScienceCommunication #ScienceAndSociety Tech #Facts #Scicomm #IndiaScience #KnowledgeIsPower #IndiaScience