New Astronomy Reviews最新文献

{"title":"Observations of pre- and proto-brown dwarfs in nearby clouds: Paving the way to further constraining theories of brown dwarf formation","authors":"Aina Palau ,&nbsp;Nuria Huélamo ,&nbsp;David Barrado ,&nbsp;Michael M. Dunham ,&nbsp;Chang Won Lee","doi":"10.1016/j.newar.2024.101711","DOIUrl":"10.1016/j.newar.2024.101711","url":null,"abstract":"<div><div>Brown Dwarfs (BDs) are crucial objects in our understanding of both star and planet formation, as well as in our understanding of what mechanisms shape the lower end of the Initial Mass Function (IMF). However, since the discovery of the first BD in 1995, there is still an unconcluded debate about which is the dominant formation mechanism of these objects. For this, it is mandatory to study BDs in their earliest evolutionary stages (what we call pre- and proto-BDs), comparable to the ‘pre-stellar’ and ‘Class 0/I’ stages well characterized for the formation of low-mass stars. In this review, the recent efforts aimed at searching, identifying and characterizing pre- and proto-BD candidates in nearby star-forming regions are presented, and revised requirements for an object to be a promising proto-BD or pre-BD candidate are provided, based on a new, unexplored so far, relation between the internal luminosity and the accreted mass. By applying these requirements, a list of 68 promising proto-BD candidates is presented, along with a compilation of possible pre-BDs from the literature. In addition, updated correlations of protostellar properties such as mass infall rate or outflow momentum rate with bolometric luminosity are provided down to the low-mass BD regime, where no significant deviations are apparent. Furthermore, the number proto-BD candidates in different clouds of the Solar Neighborhood seem to follow the known relations of number of protostars with cloud properties. In addition, proto(star-to-BD) ratios for the different clouds are also explored, unveiling a particular underproduction of low-mass proto-BD candidates in Ophiuchus compared to Lupus and Taurus. Possible explanations for this behavior are discussed, including heating of the Ophiuchus cloud by the nearby OB stars. The overall results of this work, along with the possibility that the planetary-mass regime of the IMF is subtly shaped by stellar feedback, tend to favor a Jeans-fragmentation process and therefore a star-like formation scenario down to the planetary boundary, of <span><math><mrow><mo>∼</mo><mn>0</mn><mo>.</mo><mn>01</mn></mrow></math></span> <span><math><msub><mrow><mi>M</mi></mrow><mrow><mo>⊙</mo></mrow></msub></math></span>, below which other mechanisms might be at work. Future observational constraints, such as those provided by upcoming facilities like the next-generation Very Large Array, or the use of isotope ratios based on James Webb Space Telescope data, will provide definite clues to disentangle the origin of BDs in the planetary-mass regime.</div></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"99 ","pages":"Article 101711"},"PeriodicalIF":11.7,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142651061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring Titan’s subsurface: Insights from Cassini RADAR and prospects for future investigations","authors":"Peiying He ,&nbsp;Chunyu Ding","doi":"10.1016/j.newar.2024.101710","DOIUrl":"10.1016/j.newar.2024.101710","url":null,"abstract":"<div><div>Although the Ku-band Cassini RADAR was not primarily designed to probe Titan’s subsurface structure, it unexpectedly provided valuable data on penetration, notably measuring the depth and dielectric properties of several lakes or seas in altimetry mode. While the RADAR did not possess the same penetration capability as the radar instruments that are used to search for water on Mars, its detection results and potential still warrant comprehensive integration and summary. This paper reviews the latest research findings on Titan’s subsurface observations, encompassing liquid bodies and dunes, grounded on RADAR’s penetration performance and principles. In consideration of the Dragonfly mission and its scientific goals, the paper reviews the distribution of water ice on Titan. The upcoming observations hold promise for investigating relevant features at low latitudes, such as impact craters with exposed ice-rich material. Finally, suggestions and prospects for future subsurface radar exploration of Titan are presented. The exploration of subsurface structures on Titan remains a captivating field of study, bearing significant implications for planetary science and astrobiology.</div></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"99 ","pages":"Article 101710"},"PeriodicalIF":11.7,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421385","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gamma-ray bursts at extremely small fluence","authors":"Vladimir Lipunov,&nbsp;Sergey Svertilov,&nbsp;Vladislav Topolev","doi":"10.1016/j.newar.2024.101708","DOIUrl":"10.1016/j.newar.2024.101708","url":null,"abstract":"<div><p>In this review we show that the space experiment with gamma-ray detector with sensitivity 2 orders of magnitude higher than existing ones will make it possible to discover up to a thousand neutron star mergers, even at those moments when gravitational wave (GW) antennas are not working. At the same time, synchronous detection of neutron stars mergers by gamma-ray and GW detectors will make it possible not only to study in detail the physical processes occurring at the time of the catastrophe, but also to determine the full gamma ray beam pattern, including the average jet divergence angle and the real energy of the explosion. A gamma detector that has the required sensitivity at a relatively low flight weight is proposed. The latter, in turn, will make it possible to clarify our ideas about the genesis of double relativistic stars in the Universe.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"99 ","pages":"Article 101708"},"PeriodicalIF":11.7,"publicationDate":"2024-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141997793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The CR volume for black holes and the corresponding entropy variation: A review","authors":"Shad Ali,&nbsp;Tong Liu","doi":"10.1016/j.newar.2024.101709","DOIUrl":"10.1016/j.newar.2024.101709","url":null,"abstract":"<div><p>This paper reviews the work done on black hole interior volume, entropy, and evaporation. An insight into the basics for understanding the interior volume is presented. A general analogy to investigate the interior volume of a black hole, the associated quantum mode’s entropy, and the evolution relation between the interior and exterior entropy is explained. Using this analogy, we predicted the future of information stored in a BH, its radiation, and evaporation. The results are noted in tables <span><span>1</span></span> and <span><span>2</span></span>. To apply this analogy in BH space–time, we investigated the interior volume, entropy, and evaluation relation for different types of BHs. Finally, we also investigated the nature of BH radiation and the probability of particle emission during the evaporation process.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"99 ","pages":"Article 101709"},"PeriodicalIF":11.7,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141932683","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Blind source separation in 3rd generation gravitational-wave detectors","authors":"Francesca Badaracco ,&nbsp;Biswajit Banerjee ,&nbsp;Marica Branchesi ,&nbsp;Andrea Chincarini","doi":"10.1016/j.newar.2024.101707","DOIUrl":"https://doi.org/10.1016/j.newar.2024.101707","url":null,"abstract":"<div><p>Third generation and future upgrades of current gravitational-wave detectors will present exquisite sensitivities which will allow to detect a plethora of gravitational wave signals. Hence, a new problem to be solved arises: the detection and parameter estimation of overlapped signals. The problem of separating and identifying two signals that overlap in time, space or frequency is something well known in other fields (e.g. medicine and telecommunication). Blind source separation techniques are all those methods that aim at separating two or more unknown signals. This article provides a methodological review of the most common blind source separation techniques and it analyses whether they can be successfully applied to overlapped gravitational wave signals or not, while comparing the limits and advantages of each method.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"99 ","pages":"Article 101707"},"PeriodicalIF":11.7,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141540239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Galactic Archaeology with Gaia","authors":"Alis J. Deason ,&nbsp;Vasily Belokurov","doi":"10.1016/j.newar.2024.101706","DOIUrl":"https://doi.org/10.1016/j.newar.2024.101706","url":null,"abstract":"<div><p>The <em>Gaia</em> mission has revolutionized our view of the Milky Way and its satellite citizens. The field of Galactic Archaeology has been piecing together the formation and evolution of the Galaxy for decades, and we have made great strides, with often limited data, towards discovering and characterizing the subcomponents of the Galaxy and its building blocks. Now, the exquisite 6D phase-space plus chemical information from <em>Gaia</em> and its complementary spectroscopic surveys has handed us a plethora of data to pore over as we move towards a quantitative rather than qualitative view of the Galaxy and its progenitors. We review the state of the field in the post-<em>Gaia</em> era, and examine the key lessons that will dictate the future direction of Galactic halo research.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"99 ","pages":"Article 101706"},"PeriodicalIF":11.7,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1387647324000137/pdfft?md5=871e1270905e3ddfaeb1ce290d17df14&pid=1-s2.0-S1387647324000137-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141540240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Gaia white dwarf revolution","authors":"Pier-Emmanuel Tremblay ,&nbsp;Antoine Bédard ,&nbsp;Mairi W. O’Brien ,&nbsp;James Munday ,&nbsp;Abbigail K. Elms ,&nbsp;Nicola Pietro Gentillo Fusillo ,&nbsp;Snehalata Sahu","doi":"10.1016/j.newar.2024.101705","DOIUrl":"https://doi.org/10.1016/j.newar.2024.101705","url":null,"abstract":"<div><p>This review highlights the role of the <em>Gaia</em> space mission in transforming white dwarf research. These stellar remnants constitute 5%–7% of the local stellar population in volume, yet before <em>Gaia</em> the lack of trigonometric parallaxes hindered their identification. The mission’s Data Release 2 in 2018 provided the first unbiased colour-absolute magnitude diagram of the local stellar population, identifying 260<!--> <!-->000 white dwarfs, with the number later increasing to over 355<!--> <!-->000 in Data Release 3. Since then, more than 400 white dwarf studies have made critical use of <em>Gaia</em> data, establishing it as a fundamental resource for white dwarf identification, fundamental parameter determination and more recently spectral type characterisation. The review underscores the routine reliance on <em>Gaia</em> parallaxes and extensive use of its photometry in white dwarf surveys. We also discuss recent discoveries firmly grounded in <em>Gaia</em> data, including white dwarf mergers, exotic compact binaries and evolved planetary systems.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"99 ","pages":"Article 101705"},"PeriodicalIF":6.0,"publicationDate":"2024-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1387647324000125/pdfft?md5=f02105109b88418117c5a223365ea37c&pid=1-s2.0-S1387647324000125-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141314532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"How Gaia sheds light on the Milky Way star cluster population","authors":"T. Cantat-Gaudin ,&nbsp;L. Casamiquela","doi":"10.1016/j.newar.2024.101696","DOIUrl":"https://doi.org/10.1016/j.newar.2024.101696","url":null,"abstract":"<div><p>Star clusters are among the first celestial objects catalogued by early astronomers. As simple and coeval populations, their study has been instrumental in charting the properties of the Milky Way and providing insight into stellar evolution through the 20th century. Clusters were traditionally spotted as local stellar overdensities in the plane of the sky. In recent decades, for a limited number of nearby clusters, it became possible to identify cluster members through their clustering in proper motion space. With its astrometric data of unprecedented precision, the <em>Gaia</em> mission has completely revolutionised our ability to discover and characterise Milky Way star clusters, to map their large-scale distribution, and to investigate their internal structure. In this review we focus on the population of open clusters, residing in the Galactic disc. We summarise the current state of the <em>Gaia</em>-updated cluster census and studies of young clusters and associations. We discuss recent developments in techniques for cluster detection and age estimation. We also review results enabled by <em>Gaia</em> data concerning the dynamical evolution of gravitationally bound clusters and their stellar inventory.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"99 ","pages":"Article 101696"},"PeriodicalIF":6.0,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1387647324000034/pdfft?md5=8eac01af85918c36af6d25a99bc9205b&pid=1-s2.0-S1387647324000034-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141313646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Developing a framework for understanding wormholes in modified gravity: A comprehensive review","authors":"Jitendra Kumar ,&nbsp;S.K. Maurya ,&nbsp;Sweeti Kiroriwal ,&nbsp;Sourav Chaudhary","doi":"10.1016/j.newar.2024.101695","DOIUrl":"10.1016/j.newar.2024.101695","url":null,"abstract":"<div><p>Wormholes have captured the interest of scientists and readers of science fiction as a fascinating possibility for traveling through huge cosmic distances or presumably enabling time travel. This review aims to present a thorough overview of wormholes in the context of modified gravity, highlighting the theoretical foundations, and significant developments in this rapidly developing area. In this article, we first give an overview of the concept of a wormhole in the different frameworks of modified gravities. Then this is followed by the wormhole framework, embedding diagrams, the existence of the wormholes, and thorough analysis in various modified gravities like <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mstyle><mi>R</mi></mstyle><mo>)</mo></mrow></mrow></math></span>, <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mstyle><mi>G</mi></mstyle><mo>)</mo></mrow></mrow></math></span>, <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mstyle><mi>T</mi></mstyle><mo>)</mo></mrow></mrow></math></span>, <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mstyle><mi>R</mi></mstyle><mo>,</mo><msub><mrow><mstyle><mi>L</mi></mstyle></mrow><mrow><mi>m</mi></mrow></msub><mo>)</mo></mrow></mrow></math></span>, <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mstyle><mi>R</mi><mo>,</mo><mi>T</mi></mstyle><mo>)</mo></mrow></mrow></math></span>, <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mstyle><mi>Q</mi></mstyle><mo>)</mo></mrow></mrow></math></span>, and <span><math><mrow><mi>f</mi><mrow><mo>(</mo><mstyle><mi>Q</mi><mo>,</mo><mi>T</mi></mstyle><mo>)</mo></mrow></mrow></math></span>. For distinct purposes, various models have been created. Many authors have used a variety of techniques to get a solution. Hereafter, the emphasis will be on the stability analysis of wormholes through different approaches namely Energy Conditions (ECs), Tolman–Oppenheimer–Volkoff (TOV), Volume Integral Quantifier(VIQ), Active Gravitational Mass(AGM), and Total Gravitational Energy (TGE). The possible observable features of such wormholes are briefly discussed. All the solutions are organized by the suggested framework to demonstrate broad concepts of wormhole solutions.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"98 ","pages":"Article 101695"},"PeriodicalIF":6.0,"publicationDate":"2024-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141144197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gaia’s binary star renaissance","authors":"Kareem El-Badry","doi":"10.1016/j.newar.2024.101694","DOIUrl":"https://doi.org/10.1016/j.newar.2024.101694","url":null,"abstract":"<div><p>Stellar multiplicity is among the oldest and richest problems in astrophysics. Binary stars are a cornerstone of stellar mass and radius measurements that underpin modern stellar evolutionary models. Binaries are the progenitors of many of the most interesting and exotic astrophysical phenomena, ranging from type Ia supernovae to gamma ray bursts, hypervelocity stars, and most detectable stellar black holes. They are also ubiquitous, accounting for about half of all stars in the Universe. In the era of gravitational waves, wide-field surveys, and open-source stellar models, binaries are coming back stronger than a nineties trend. Much of the progress in the last decade has been enabled by the <em>Gaia</em> mission, which provides high-precision astrometry for more than a billion stars in the Milky Way. The <em>Gaia</em> data probe a wider range of binary separations and mass ratios than most previous surveys, enabling both an improved binary population census and discovery of rare objects. I summarize recent results in the study of binary stars brought about by <em>Gaia</em>, focusing in particular on developments related to wide (<span><math><mrow><mi>a</mi><mo>≳</mo><mn>100</mn></mrow></math></span> <!--> <!-->au) binaries, evidence of binarity from astrometric noise and proper motion anomaly, astrometric and radial velocity orbits from <em>Gaia</em> DR3, and binaries containing non-accreting compact objects. Limitations of the <em>Gaia</em> data, the importance of ground-based follow-up, and anticipated improvements with <em>Gaia</em> DR4 are also discussed.</p></div>","PeriodicalId":19718,"journal":{"name":"New Astronomy Reviews","volume":"98 ","pages":"Article 101694"},"PeriodicalIF":6.0,"publicationDate":"2024-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141084233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}