Astronomische Nachrichten最新文献

{"title":"The Meaning of Quasi-Simultaneous X-Rays and Gamma-Ray Observations of RS Oph in Outburst","authors":"Marina Orio,&nbsp;Ke Fang,&nbsp;Jay Gallagher,&nbsp;Gerardo Juan M. Luna,&nbsp;Joanna Mikolajewska","doi":"10.1002/asna.20240140","DOIUrl":"https://doi.org/10.1002/asna.20240140","url":null,"abstract":"<p>Shocks in novae outbursts are ubiquitous, but in symbiotic novae, they are particularly powerful, probably because of the surrounding red giant wind. The recurrent nova RS Oph is the best example of this phenomenon. The presence of shocked plasma in outburst was inferred from optical spectra, and it was confirmed by X-ray observations since 1985. Since 2010, the gamma-ray observatory Fermi has proven that novae in general are the site of particle acceleration, producing copious gamma-ray flux in the few-GeV range. In the last outburst of the symbiotic RS Oph in 2021, gamma-rays were not only detected with Fermi in the GeV range but also detected in the TeV range of the Cherenkov telescopes, for about 3 weeks. Diesing et al. in 2023 showed that there must have been at least two distinct episodes of shocks, likely of hadronic nature, both generating particle acceleration. We present new NuSTAR data and re-discuss XMM-Newton high-resolution grating spectra and NICER data that we recently published. We concluded that the primary shock causing the particle acceleration observed in the range of TeV gamma-rays with the Cherenkov telescopes was the same phenomenon observed and studied with the x-ray observatories. However, the shocked plasma from which the particles were accelerated causing the gamma-ray flux observed after 1 day with Fermi was—at least initially—unobservable. We suggest that this first episode of shock occurred when the nova ejecta collided with a dense outflow close to the atmosphere of the red giant, with such a high absorbing column that x-rays were absorbed.</p>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asna.20240140","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143114534","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Issue Information: Astron. Nachr. 09/2024","authors":"","doi":"10.1002/asna.20249008","DOIUrl":"https://doi.org/10.1002/asna.20249008","url":null,"abstract":"","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"345 9-10","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asna.20249008","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143186909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Cover Picture: Astron. Nachr. 9/2024","authors":"Balázs Pál,&nbsp;László Dobos","doi":"10.1002/asna.20249017","DOIUrl":"https://doi.org/10.1002/asna.20249017","url":null,"abstract":"<p>Denoising a medium resolution stellar spectrum with neural networks. <i>Top</i>: Example of a noiseless simulated stellar spectrum (blue) transformed to an “observation” by adding a realistic noise component (gray) such that the effective S/N≈19. <i>Middle</i>: Comparison of the original noiseless simulated spectrum (blue) and the reconstructed spectrum (dashed orange) using a trained denoising autoencoder. The two lines overlap almost entirely, indicating the high accuracy of the machine learning method. <i>Bottom</i>: Relative error calculated as the fraction of pixel-wise residual noise and the original noiseless flux. The mean and maximum of the relative error are 0.175% and 1.806%, respectively. Formore details see the related paper by Pál and Dobos, published in this issue e240049. \u0000 <figure>\u0000 <div><picture>\u0000 <source></source></picture><p></p>\u0000 </div>\u0000 </figure></p>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"345 9-10","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asna.20249017","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143186908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Phase Structure of Holographic Superconductors With Spontaneous Scalarization","authors":"Hong Guo,&nbsp;Wei-Liang Qian,&nbsp;Bean Wang","doi":"10.1002/asna.20240145","DOIUrl":"https://doi.org/10.1002/asna.20240145","url":null,"abstract":"<div>\u0000 \u0000 <p>Within the holographic framework, we investigate the Einstein-scalar-Gauss-Bonnet theory coupled with a Maxwell field in an asymptotically anti-de Sitter (AdS) spacetime. Our findings reveal that holographic superconductor solutions exist when the Gauss-Bonnet coupling constant is below the critical value <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>λ</mi>\u0000 <mi>c</mi>\u0000 </msub>\u0000 <mo>≈</mo>\u0000 <mn>0.6339</mn>\u0000 </mrow>\u0000 <annotation>$$ {lambda}_capprox 0.6339 $$</annotation>\u0000 </semantics></math>, while spontaneous scalarization solutions emerge for <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>λ</mi>\u0000 <mo>&gt;</mo>\u0000 <msub>\u0000 <mi>λ</mi>\u0000 <mi>c</mi>\u0000 </msub>\u0000 </mrow>\u0000 <annotation>$$ lambda &gt;{lambda}_c $$</annotation>\u0000 </semantics></math>. This raises the question whether the hairy black holes triggered by different mechanisms are smoothly joined by a phase transition or whether these are actually identical solutions. To examine this transition in greater detail, we constructed a phase diagram in terms of temperature and chemical potential. By explicitly evaluating the Gibbs free energy and its derivatives, we demonstrate that a smooth yet first-order phase transition occurs between the two hairy solutions. In particular, a thermodynamic process can be devised in which a superconducting black hole transitions into a scalarized black hole by raising or lowering the temperature.</p>\u0000 </div>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 3-4","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144206622","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Consistent Crust-Core Interpolation and Its Effect on Non-radial Neutron Star Oscillations","authors":"Martín O. Canullán-Pascual,&nbsp;Mauro Mariani,&nbsp;Ignacio F. Ranea-Sandoval,&nbsp;Milva G. Orsaria,&nbsp;Fridolin Weber","doi":"10.1002/asna.20240150","DOIUrl":"https://doi.org/10.1002/asna.20240150","url":null,"abstract":"<div>\u0000 \u0000 <p>To model the structure of neutron stars (NSs) theoretically, it is common to consider layers with different density regimes. Matching the equation of state (EoS) for the crust and core and obtaining a suitable description of these extreme conditions are crucial for understanding the properties of these compact objects. In this work, we construct 10 different NS EoSs incorporating three distinct crust models, which are connected to the core using a thermodynamically and causally consistent formalism. For cold NSs, we propose a linear relationship between pressure and energy density in a narrow region between the crust and core, effectively establishing an interpolation function in the pressure-baryonic chemical potential plane. We then compare this EoS matching method with the classical approach, which neglects causal and thermodynamic consistency. We solve the Tolman–Oppenheimer–Volkoff equation to obtain the mass-radius relationship and compare our results with observational constraints on NSs. Furthermore, we investigate the influence of the new matching formalism on non-radial oscillation frequencies and damping times. Our findings suggest that the method used to <i>glue</i> the crust and core EoS impacts NS observables, such as the radius, oscillation frequencies, and damping times of non-radial modes, which may be crucial for interpreting future gravitational wave observations from neutron star mergers or isolated pulsars. The effects are particularly noticeable for low-mass NSs, regardless of the specific EoS model chosen. In particular, we find that the <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>p</mi>\u0000 <mn>1</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation>$$ {p}_1 $$</annotation>\u0000 </semantics></math> oscillation mode exhibits significant differences in frequencies among alternative matching methods, whereas the fundamental <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>f</mi>\u0000 </mrow>\u0000 <annotation>$$ f $$</annotation>\u0000 </semantics></math>-mode remains unaffected by changes in crust models or interpolation schemes.</p>\u0000 </div>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 3-4","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144206623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Revisiting Variable Stars Near Globular Clusters South of −29° Declination","authors":"Andrew C. Layden,&nbsp;Julia Evangelista,&nbsp;Sakshi Gupta,&nbsp;Mithilesh Mittameda,&nbsp;Eva Mulloy,&nbsp;Sohan I. Muslim,&nbsp;Tiyinoluwa Olushola-Alao,&nbsp;Akul Rishi","doi":"10.1002/asna.20240135","DOIUrl":"https://doi.org/10.1002/asna.20240135","url":null,"abstract":"<p>We review an often-cited but seldom-accessed catalogue by Fourcade and Laborde (1966) of 785 variable stars near 47 southern Galactic globular clusters, and recover the locations of 85 stars that were not incorporated into subsequent variable star catalogues and hence have become “lost” to the literature. We match the positions of these stars with those of modern variable star databases (Gaia, ASAS-SN, and VSX) and find 96% appear in at least one of these catalogues. We used proper motions and radial velocities from the Gaia Third Data Release to assess cluster membership, finding that most are field stars, but up to five may be members of NGC 5927 and one of NGC 6624.</p>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 2","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asna.20240135","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143489842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Searching the Non-Accreting White Dwarf Population in eROSITA Data","authors":"S. Friedrich,&nbsp;C. Maitra,&nbsp;K. Dennerl,&nbsp;A. Schwope,&nbsp;K. Werner,&nbsp;B. Stelzer","doi":"10.1002/asna.20240139","DOIUrl":"https://doi.org/10.1002/asna.20240139","url":null,"abstract":"<p>eROSITA is the soft X-ray instrument aboard the Spectrum Roentgen Gamma (SRG) satellite that is most sensitive in the energy range between 0.2 and 2.3 keV. Between December 2019 and December 2021, eROSITA completed four all-sky surveys, producing all-sky X-ray source lists and sky maps of unprecedented depth. In the energy range between 0.2 keV and 1 keV, we detected about 38,000 sources with a hardness ratio below −0.94, covering a small sample of known white dwarfs found with eROSITA in the dataset to which the German eROSITA consortium has rights (half sky). Two hundred and sixty four of these soft sources have a probability of more than 90% to be a white dwarf. This is more than the 175 white dwarfs ROSAT found in the whole sky. Here we present the results of a pilot study to increase the sensitivity of eROSITA for soft sources by extending the detection threshold down to 0.1 keV. First tests with dedicated sky regions are promising.</p>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asna.20240139","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143113520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Letter From the Editor","authors":"Klaus G. Strassmeier","doi":"10.1002/asna.20240141","DOIUrl":"https://doi.org/10.1002/asna.20240141","url":null,"abstract":"<p>With the present first issue of volume 346 in 2025, we enter the 204th year of continuous appearance of Astronomische Nachrichten/Astronomical Notes (AN). The continuing complexity of worldwide scientific publishing had kept us busy over the years; it also impacts AN. The tricky part for our comparably small journal is maintaining a high standard, but also being openly accessible at the same time, preferably without costs. The end product shall be a peer-reviewed, content-oriented, and thus user-oriented, widely distributed and easily accessible journal with original research papers that one is happy to cite.</p><p>This is achieved with accompanying editorial changes. While we currently still rely on the ScholarOne submission platform for user interaction, it will be replaced with the new editorial system Research Exchange (ReX) that is being rolled out as a peer-review tool to all Wiley journals during the course of this year. eLocators instead of the sequential page numbers for easy identification, a modern web appearance where you can find the latest but also all historical volumes of AN, and open access as part of the European DEAL treaty remain cornerstones. AN's most recent Journal Impact Factor (Clarivate) is 1.1.</p><p>As before, the Leibniz-Institute for Astrophysics Potsdam (AIP) continues hosting the editorial office in close collaboration with Wiley. The editorial team can be contacted through <span>[email protected]</span>. Papers are welcomed in all fields of astronomy, astrophysics, and solar-system research, as well as related aspects in instrumentation, astrobiologic, and historic studies. Many thanks in advance. We are looking forward to another year of submissions.</p><p>The author declares no conflicts of interest.</p>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2025-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asna.20240141","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143112296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Stellar Physics and General Relativity","authors":"Shuichi Yokoyama","doi":"10.1002/asna.20240127","DOIUrl":"https://doi.org/10.1002/asna.20240127","url":null,"abstract":"<p>The general theory of relativity is currently established as the most precise theory of gravity supported by observations, and its application is diverse ranging from astronomy to cosmology, while its application to astrophysics has been restricted only to compact stars due to the assumption that the Newtonian approximation is sufficient for celestial bodies with medium density such as the sun. Surprisingly, the recent research of the author has implied that this long-held assumption is not valid, and that nonperturbative effects significantly change relevant results obtained by Newtonian gravity. In particular, local physical quantities inside the sun are newly predicted to exhibit power law differently from the so-called standard solar model. This surprising result is reviewed including brief discussion of physics behind the discrepancy and a little new application.</p>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 3-4","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asna.20240127","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144206988","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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":"Concluding Remarks to the IWARA 2024","authors":"J. E. Horvath","doi":"10.1002/asna.20240137","DOIUrl":"https://doi.org/10.1002/asna.20240137","url":null,"abstract":"<div>\u0000 \u0000 <p>A brief discussion of the science presented at the IWARA 2024 (with emphasis in Cosmology) is given as a summary of the workshop held in Machu Picchu, Peru.</p>\u0000 </div>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 3-4","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144206982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}