Astronomische Nachrichten最新文献

{"title":"Accretion Onto Weakly Magnetized Neutron Stars: Polarization Theory and Its Application to X-Ray Burster GX 13+1","authors":"Anna Bobrikova,&nbsp;Sofia V. Forsblom","doi":"10.1002/asna.20240128","DOIUrl":"https://doi.org/10.1002/asna.20240128","url":null,"abstract":"<p>Observations show that the x-ray emission of the accreting weakly magnetized neutron stars (WMNSs) is polarized. In this article, we summarize the analytical models for the polarized emission of various components of the WMNSs. We introduce a missing theoretical model, where we assume the emission comes from the spreading layer, the extension of the boundary layer between the accretion disk and the neutron star. We show how these models and the results of the simulations provide new insights into the x-ray polarization from weakly magnetized neutron stars observed with the imaging x-ray polarimetry explorer (IXPE). We specifically focus on the most peculiar case of the X-ray burster GX 13+1.</p>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asna.20240128","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143115699","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":"Semi-Stable Active Region Around the Co-Rotation Latitude of Low-Mass Close Binary KIC 7671594","authors":"N. Ö. Kaya,&nbsp;H. A. Dal","doi":"10.1002/asna.20240115","DOIUrl":"https://doi.org/10.1002/asna.20240115","url":null,"abstract":"<div>\u0000 \u0000 <p>We present the new findings from the light variation of KIC 7671594. We have analyzed the light curve of the system, which is likely a low-mass eclipsing close binary. We have detected a spotted active region migration on the active component. This spotted active region on the stellar surface appears to be stable during the first 2.70 years, but it exhibits rapid migration during the last 0.85 years of the observing season. The OPEA model was derived using 1128 flares and their corresponding parameters. In the model, the <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mtext>Plateau</mtext>\u0000 </mrow>\u0000 <annotation>$$ Plateau $$</annotation>\u0000 </semantics></math> value was found to be 2.46703 ± 0.25234 s, and the <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mtext>half</mtext>\u0000 <mo>−</mo>\u0000 <mtext>life</mtext>\u0000 </mrow>\u0000 <annotation>$$ half- life $$</annotation>\u0000 </semantics></math> was calculated as 7332.28 s. The flare <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>N</mi>\u0000 <mn>1</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation>$$ {N}_1 $$</annotation>\u0000 </semantics></math> frequency was determined to be 0.03719 <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msup>\u0000 <mi>h</mi>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>1</mn>\u0000 </mrow>\u0000 </msup>\u0000 </mrow>\u0000 <annotation>$$ {h}^{-1} $$</annotation>\u0000 </semantics></math>, while <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <msub>\u0000 <mi>N</mi>\u0000 <mn>2</mn>\u0000 </msub>\u0000 </mrow>\u0000 <annotation>$$ {N}_2 $$</annotation>\u0000 </semantics></math> was found to be 0.00028. We have concluded that KIC 7671594 is likely a low-mass eclipsing binary system with a main sequence component that possesses an active region covered by some cool spots around its co-rotation latitude.</p>\u0000 </div>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"345 9-10","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143186945","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":"Radial Metallicity Gradients for the Chemically Selected Galactic Thin Disc Main-Sequence Stars","authors":"F. Akbaba,&nbsp;T. Ak,&nbsp;S. Bilir,&nbsp;O. Plevne,&nbsp;Ö. Önal Taş,&nbsp;G. M. Seabroke","doi":"10.1002/asna.20240052","DOIUrl":"https://doi.org/10.1002/asna.20240052","url":null,"abstract":"&lt;div&gt;\u0000 \u0000 &lt;p&gt;We present the radial metallicity gradients within the Galactic thin disc population through main-sequence stars selected on the chemical plane using GALAH DR3 accompanied with &lt;i&gt;Gaia&lt;/i&gt; DR3 astrometric data. The [Fe/H], [&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;α&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ alpha $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;/Fe] and [Mg/H] radial gradients are estimated for guiding radius as &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;0.074&lt;/mn&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;mn&gt;0.006&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ -0.074pm 0.006 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;mn&gt;0.004&lt;/mn&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;mn&gt;0.002&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ +0.004pm 0.002 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;0.074&lt;/mn&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;mn&gt;0.006&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ -0.074pm 0.006 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; dex kpc&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt; &lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ {}^{-1} $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and for the traceback early orbital radius as &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;0.040&lt;/mn&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;mn&gt;0.002&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ -0.040pm 0.002 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;+&lt;/mo&gt;\u0000 &lt;mn&gt;0.003&lt;/mn&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;mn&gt;0.001&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ +0.003pm 0.001 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;−&lt;/mo&gt;\u0000 &lt;mn&gt;0.039&lt;/mn&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;mn&gt;0.002&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ -0.039pm 0.002 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; dex kpc&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mrow&gt;\u0000 ","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"345 9-10","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143186450","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":"Weakly Magnetized Accreting Neutron Stars as Seen by IXPE","authors":"Alessandro Di Marco,&nbsp;IXPE Science Team","doi":"10.1002/asna.20240126","DOIUrl":"https://doi.org/10.1002/asna.20240126","url":null,"abstract":"<p>The Imaging X-ray Polarimetry Explorer, recently awarded by the American Astronomical Society with the Bruno Rossi prize, observed several accreting neutron stars in X-ray binaries during the first 2 years of its prime mission. Results obtained for weakly magnetized neutron stars allow us to model the geometry and the physical status of the different emitting regions (accretion disk, boundary/spreading layer) in a completely novel way, showing a more intricate scenario with respect to the one initially anticipated based on theoretical models. In particular, polarization measurements have demonstrated variations with energy and time, which are highly intriguing. Here, a summary of the IXPE findings for these sources, in particular 4U 1820–303, and Cir X–1 are reported.</p>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asna.20240126","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143110556","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":"Mass-Loss, Composition and Observational Signatures of Stellar Winds From X-Ray Bursts","authors":"Yago Herrera,&nbsp;Daniel Muñoz Vela,&nbsp;Gloria Sala,&nbsp;Jordi José,&nbsp;Yuri Cavecchi","doi":"10.1002/asna.20240122","DOIUrl":"https://doi.org/10.1002/asna.20240122","url":null,"abstract":"<p>X-Ray bursts (XRBs) are powerful thermonuclear events on the surface of accreting neutron stars (NSs), which can synthesize intermediate-mass elements. Although the high surface gravity prevents an explosive ejection, a small fraction of the envelope may be ejected by radiation-driven winds. In our previous works, we have developed a non-relativistic radiative wind model and coupled it to an XRB hydrodynamic simulation. We now apply this technique to another model featuring consecutive bursts. We determine the mass-loss and chemical composition of the wind ejecta. Results show that, for a representative XRB, about <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>0.1</mn>\u0000 <mo>%</mo>\u0000 </mrow>\u0000 <annotation>$$ 0.1% $$</annotation>\u0000 </semantics></math> of the envelope mass is ejected per burst, at an average rate of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>3.9</mn>\u0000 <mo>×</mo>\u0000 <msup>\u0000 <mn>10</mn>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>12</mn>\u0000 </mrow>\u0000 </msup>\u0000 <mspace></mspace>\u0000 <msub>\u0000 <mi>M</mi>\u0000 <mo>⊙</mo>\u0000 </msub>\u0000 <msup>\u0000 <mtext>year</mtext>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>1</mn>\u0000 </mrow>\u0000 </msup>\u0000 </mrow>\u0000 <annotation>$$ 3.9times {10}^{-12}kern0.1em {mathrm{M}}_{odot }{mathrm{year}}^{-1} $$</annotation>\u0000 </semantics></math>. Between <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>66</mn>\u0000 <mo>%</mo>\u0000 </mrow>\u0000 <annotation>$$ 66% $$</annotation>\u0000 </semantics></math> and <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>76</mn>\u0000 <mo>%</mo>\u0000 </mrow>\u0000 <annotation>$$ 76% $$</annotation>\u0000 </semantics></math> of the ejecta composition is ⁶⁰Ni, ⁶⁴Zn, ⁶⁸Ge, ⁴He and ⁵⁸Ni. We also report on the evolution of observational quantities during the wind phase and simulate NICER observations that resemble those of 4 U 1820–40.</p>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asna.20240122","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143120670","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":"White Dwarf Stars in the Big Data Era","authors":"Maria Camisassa","doi":"10.1002/asna.20240118","DOIUrl":"https://doi.org/10.1002/asna.20240118","url":null,"abstract":"<p>White dwarf stars are the most common endpoint of stellar evolution. Therefore, these old, numerous and compact objects provide valuable information on the late stages of stellar evolution, the physics of dense plasma and the structure and evolution of our Galaxy. The ESA <i>Gaia</i> space mission has revolutionized this research field, providing parallaxes and multi-band photometry for nearly 360,000 white dwarfs. Furthermore, this data, combined with spectroscopical and spectropolarimetric observations, have provided new information on their chemical abundances and magnetic fields. This large data set has raised new questions on the nature of white dwarfs, boosting our theoretical efforts for understanding the physics that governs their evolution and for improving the statistical analysis of their collective properties. In this article, I summarize the current state of our understanding of the collective properties of white dwarfs, based of detailed theoretical models and population synthesis studies.</p>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asna.20240118","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143120205","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":"Spectroscopic and Photometric Analyses of the Trapezium Stars θ1 Ori A and θ1 Ori D","authors":"A. Elmaslı,&nbsp;K. Ö. Ünal,&nbsp;D. Ozuyar","doi":"10.1002/asna.20240080","DOIUrl":"https://doi.org/10.1002/asna.20240080","url":null,"abstract":"&lt;div&gt;\u0000 \u0000 &lt;p&gt;In this paper, we report on the spectroscopic and photometric observations of the two Trapezium stars, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;θ&lt;/mi&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ {theta}^1 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; Ori A and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;θ&lt;/mi&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ {theta}^1 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; Ori D. The spectra of these stars were extracted from the ESO and ESPaDOnS archives. Both stars exhibit nebular emission features, particularly within the core of the Balmer profiles and He I lines at &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;λ&lt;/mi&gt;\u0000 &lt;mn&gt;5875&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ lambda 5875 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;λ&lt;/mi&gt;\u0000 &lt;mn&gt;6680&lt;/mn&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ lambda 6680 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;. Additionally, the spectral energy distributions of these targets were constructed, revealing an infrared excess in both. These emission structures and infrared excesses are attributed to the H II region caused by &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;θ&lt;/mi&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ {theta}^1 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; Ori C. Furthermore, detailed spectroscopic analysis performed to &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;θ&lt;/mi&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ {theta}^1 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; Ori A and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msup&gt;\u0000 &lt;mi&gt;θ&lt;/mi&gt;\u0000 &lt;mn&gt;1&lt;/mn&gt;\u0000 &lt;/msup&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt;$$ {theta}^1 $$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; Ori D revealed similar abundance patterns, with slight differences in carbon, magnesium, and aluminum. The effective temperatures derived from the spectroscopic analysis were used to determine their positions on the Hertzsprung-Russell (H-R) diagram. Additionally, the evolutionary tracks and isochrones constructed on the H-R diagram allowed for the estimation of their evolutionary masses and ages. Finally, TESS observatio","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"345 9-10","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143187201","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":"Spectral Studies of Super-Eddington Accreting Neutron Stars in the Magellanic Clouds","authors":"Georgios Vasilopoulos,&nbsp;Marios Kouzis,&nbsp;Brent F. West,&nbsp;Peter A. Becker","doi":"10.1002/asna.20240114","DOIUrl":"https://doi.org/10.1002/asna.20240114","url":null,"abstract":"<p>Major outbursts of BeXRBs offer a unique laboratory for studying accretion onto magnetized neutron stars (NSs) over a large dynamic range. The accreting material is entrained from the accretion disk by the strong magnetic field, and then channeled onto the NS, forming a so-called accretion column (AC). Physical simulation of the AC requires consideration of various physical processes occurring in strongly magnetized plasma, including complex multi-dimensional radiative transfer and the presence of a radiation-dominated shock. Analytical models based on the Becker and Wolff (2007) model have proven successful at reproducing the observed AC spectra in super-critical sources in which radiation pressure plays the dominant role in controlling the dynamics of the accreting material. In this study, we will apply the model to obtain spectra observed during super-Eddington outbursts of BeXRBs in the Magellanic Clouds.</p>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asna.20240114","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143118756","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":"The Long-Term Variability of a Population of ULXs Monitored by Chandra","authors":"Hannah P. Earnshaw,&nbsp;Gauri Patti,&nbsp;Murray Brightman,&nbsp;Rajath Sathyaprakash,&nbsp;Dominic J. Walton,&nbsp;Felix Fürst,&nbsp;Timothy P. Roberts,&nbsp;Fiona A. Harrison","doi":"10.1002/asna.20240103","DOIUrl":"https://doi.org/10.1002/asna.20240103","url":null,"abstract":"<div>\u0000 \u0000 <p>We present preliminary results of a <i>Chandra</i> Large Program to monitor the ultraluminous x-ray source (ULX) populations of three nearby, ULX-rich galaxies over the course of a year, finding the ULX population to show a variety of long-term variability behaviours. Of a sample of 36 ULXs, some show persistent or moderately variable flux, often with a significant relationship between hardness and luminosity, consistent with a supercritically accreting source with varying accretion rates. Six show very high-amplitude variability with no strong relationship between luminosity and hardness, though not all of them show evidence of any long-term periodicity, nor of the bimodal distribution indicative of the propeller effect. We find evidence of additional eclipses for two previously-identified eclipsing ULXs. Additionally, many sources that were previously identified as ULXs in previous studies were not detected at ULX luminosities during our monitoring campaign, indicating a large number of transient ULXs.</p>\u0000 </div>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143118139","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":"Highly Significant Detection of X-Ray Polarization in Sco X-1 and Its Polarization Angle Misaligned With the Direction of the Radio Jet","authors":"Fabio La Monaca,&nbsp;IXPE Science Team","doi":"10.1002/asna.20240107","DOIUrl":"https://doi.org/10.1002/asna.20240107","url":null,"abstract":"<p>The Imaging X-ray Polarimetry Explorer has successfully measured the X-ray polarization of Scorpius X-1, the brightest Z-source, in the 2–8 keV energy band. The degree of polarization was found to be <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 <mn>1.0</mn>\u0000 <mo>%</mo>\u0000 </mrow>\u0000 <annotation>$$ sim 1.0% $$</annotation>\u0000 </semantics></math> with a polarization angle of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 <mn>8</mn>\u0000 </mrow>\u0000 <annotation>$$ sim 8 $$</annotation>\u0000 </semantics></math>°. This measurement was conducted simultaneously with NICER, NuSTAR, and Insight-HXMT observations, enabling a detailed analysis of the source's broad-band spectrum across soft and hard X-rays. The source was observed for the majority of the time in its soft state, with occasional flaring. Furthermore, low-frequency quasiperiodic oscillations were observed. Through a spectro-polarimetric analysis, we determined that the accretion disk exhibits a polarization &lt;3.2% (90% CL) and the Comptonized component at higher energy a polarization of <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 <mn>1.3</mn>\u0000 <mo>%</mo>\u0000 </mrow>\u0000 <annotation>$$ sim 1.3% $$</annotation>\u0000 </semantics></math>. An attempt was also performed to measure the polarization of the reflection component. Moreover, a rotation in X-ray polarization is observed compared to previous observations by OSO-8 and PolarLight, as well as with respect to the position angle of the radio jet. This finding suggests that the polarization may vary with the state of the source, which means a change in the geometry of the corona with the accretion flow or potentially indicating a relativistic precession.</p>","PeriodicalId":55442,"journal":{"name":"Astronomische Nachrichten","volume":"346 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/asna.20240107","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143117449","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}