Astronomy & Astrophysics最新文献

{"title":"Slim-disk modeling reveals an accreting intermediate-mass black hole in the luminous fast blue optical transient AT2018cow","authors":"Zheng Cao, Peter G. Jonker, Sixiang Wen, Ann I. Zabludoff","doi":"10.1051/0004-6361/202451297","DOIUrl":"https://doi.org/10.1051/0004-6361/202451297","url":null,"abstract":"The origin of the most luminous subclass of the fast blue optical transients (LFBOTs) is still unknown. We present an X-ray spectral analysis of AT2018cow – the LFBOT archetype – using <i>NuSTAR<i/>, <i>Swift<i/>, and <i>XMM-Newton<i/> data. The source spectrum can be explained by the presence of a slim accretion disk, and we find that the mass accretion rate decreases to sub–Eddington levels ≳200 days after the source’s discovery. Applying our slim-disk model to data obtained at multiple observational epochs, we constrain the mass of the central compact object in AT2018cow to be log( at the 68% confidence level. Our mass measurement is independent from, but consistent with, the results from previously employed methods. The mass constraint is consistent with both the tidal disruption and the black hole–star merger scenarios, if the latter model can be extrapolated to the measured black hole mass. Our work provides evidence for an accreting intermediate–mass black hole (10<sup>2<sup/> − 10<sup>6<sup/> <i>M<i/><sub>⊙<sub/>) as the central engine in AT2018cow, and, by extension, in LFBOT sources similar to AT2018cow.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"13 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670330","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":"Magnetic field of the roAp star KIC 10685175: Observations versus theory","authors":"Fangfei Shi, Huawei Zhang, Swetlana Hubrig, Silva Järvinen, Huiling Chen, Tianqi Cang, Jianning Fu, Donald Kurtz","doi":"10.1051/0004-6361/202451417","DOIUrl":"https://doi.org/10.1051/0004-6361/202451417","url":null,"abstract":"<i>Context<i/>. KIC 10685175 is a roAp star whose polar magnetic field is predicted to be 6 kG through a nonadiabatic axisymmetric pulsation theoretical model.<i>Aims<i/>. In this work, we aim to measure the magnetic field strength of KIC 10685175 using high-resolution spectropolarimetric observations, and compare it with the one predicted by the theoretical model.<i>Methods<i/>. Two high-resolution unpolarized spectra have been analyzed to ascertain the presence of magnetically split lines and derive the iron abundance of this star through equivalent width measurements of 10 Fe lines. One polarized spectrum has been used to measure the mean longitudinal magnetic field with the least-squares deconvolution technique. Further, to examine the presence of chemical spots on the stellar surface, we have measured the mean longitudinal magnetic fields using different lines belonging to different elements.<i>Results<i/>. From the study of two high-resolution unpolarized spectra, we obtained the spectroscopic atmospheric parameters including the effective temperature (<i>T<i/><sub>eff<sub/>), surface gravity (log 𝑔), iron abundance ([Fe/H]), abundance ratio of alpha elements to iron ([<i>α<i/>/Fe]), and micro-turbulent velocity (<i>V<i/><sub><i>mic<i/><sub/>). The final result is [<i>T<i/><sub>eff<sub/>, log g, [Fe/H], [<i>α<i/>/Fe], <i>V<i/><sub><i>mic<i/><sub/>)]=[8250 ± 200 K, 4.4 ± 0.1, −0.4 ± 0.2, 0.16 ± 0.1, 1.73 ± 0.2 km s<sup>−1<sup/>]. Although the Fe absorption lines appear relatively weak in comparison to typical Ap stars with similar <i>T<i/><sub>eff<sub/>, the lines belonging to rare earth elements (Eu and Nd) are stronger than those in chemically normal stars, indicating the peculiar nature of KIC 10685175. The mean longitudinal magnetic field, 〈<i>B<i/><sub><i>ℓ<i/><sub/>〉 = −226 ± 39 G, was measured in the polarized spectrum, but magnetically split lines were not detected. No significant line profile variability is evident in our spectra. Also, the longitudinal magnetic field strengths measured using line masks constructed for different elements are rather similar. Due to the poor rotation phase coverage of our data, additional spectroscopic and polarimetric observations are needed to allow us to come to any conclusions about the inhomogeneous element distribution over the stellar surface.<i>Conclusions<i/>. The estimated polar magnetic field is 4.8 ± 0.8 kG, which is consistent with the predicted polar magnetic field strength of about 6kG within 3<i>σ<i/>. This work therefore provides support for the pulsation theoretical model.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"31 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670326","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":"J-PLUS: The fraction of calcium white dwarfs along the cooling sequence","authors":"C. López-Sanjuan, P.-E. Tremblay, M. W. O’Brien, D. Spinoso, A. Ederoclite, H. Vázquez Ramió, A. J. Cenarro, A. Marín-Franch, T. Civera, J. M. Carrasco, B. T. Gänsicke, N. P. Gentile Fusillo, A. Hernán-Caballero, M. A. Hollands, A. del Pino, H. Domínguez Sánchez, J. A. Fernández-Ontiveros, F. M. Jiménez-Esteban, A. Rebassa-Mansergas, L. Schmidtobreick, R. E. Angulo, D. Cristóbal-Hornillos, R. A. Dupke, C. Hernández-Monteagudo, M. Moles, L. Sodré, J. Varela","doi":"10.1051/0004-6361/202451226","DOIUrl":"https://doi.org/10.1051/0004-6361/202451226","url":null,"abstract":"<i>Aims<i/>. We used the Javalambre Photometric Local Universe Survey (J-PLUS) second data release (DR2) photometry in 12 optical bands over 2176 deg<sup>2<sup/> to estimate the fraction of white dwarfs with the presence of Ca II H+K absorption along the cooling sequence.<i>Methods<i/>. We compared the J-PLUS photometry against metal-free theoretical models to estimate the equivalent width in the <i>J<i/>0395 passband of 10 nm centered at 395 nm (EW<sub><i>J<i/>0395<sub/>), a proxy to detect calcium absorption. A total of 4399 white dwarfs with effective temperatures within 30 000 > <i>T<i/><sub>eff<sub/> > 5500 K and masses of <i>M<i/> > 0.45 <i>M<i/><sub>⊙<sub/> were analyzed. Their EW<sub><i>J<i/>0395<sub/> distribution was modeled using two populations, corresponding to polluted and non-polluted systems, to estimate the fraction of calcium white dwarfs (<i>f<i/><sub>Ca<sub/>) as a function of <i>T<i/><sub>eff<sub/>. The probability of each individual white dwarf presenting calcium absorption, <i>p<i/><sub>Ca<sub/>, was also computed.<i>Results<i/>. The comparison of EW<sub><i>J<i/>0395<sub/> with both the measured Ca/He abundance and the identification of metal pollution from spectroscopy shows that EW<sub><i>J<i/>0395<sub/> correlates with the presence of Ca II H+K absorption. The fraction of calcium white dwarfs changes along the cooling sequence, increasing from <i>f<i/><sub>Ca<sub/> ≈ 0 at <i>T<i/><sub>eff<sub/> = 13 500 K to f<sub>Ca<sub/> ≈ 0.15 at <i>T<i/><sub>eff<sub/> = 5500 K. This trend reflects the selection function of calcium white dwarfs in the optical. We compare our results with the fractions derived from the 40 pc spectroscopic sample and from Sloan Digital Sky Survey (SDSS) spectra. The trend found in J-PLUS observations is also present in the 40 pc sample; however, SDSS shows a deficit of metal-polluted objects at <i>T<i/><sub>eff<sub/> < 12 000 K. Finally, we found 39 white dwarfs with <i>p<i/>Ca > 0.99. Twenty of them have spectra presented in previous studies, whereas we obtained follow-up spectroscopic observations for six additional targets. These 26 objects were all confirmed as metal-polluted systems.<i>Conclusions<i/>. The J-PLUS optical data provide a robust statistical measurement for the presence of Ca II H+K absorption in white dwarfs. We find a 15 ± 3% increase in the fraction of calcium white dwarfs from <i>T<i/><sub>eff<sub/> = 13 500 K to 5500 K, which reflects their selection function in the optical from the total population of metal-polluted systems.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"22 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670349","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":"Consistency of JWST black hole observations with NANOGrav gravitational wave measurements","authors":"John Ellis, Malcolm Fairbairn, Gert Hütsi, Juan Urrutia, Ville Vaskonen, Hardi Veermäe","doi":"10.1051/0004-6361/202450846","DOIUrl":"https://doi.org/10.1051/0004-6361/202450846","url":null,"abstract":"JWST observations have opened a new chapter in supermassive black hole (SMBH) studies, stimulating discussion of two puzzles: the abundance of high-z SMBHs and the fraction of dual active galactic nuclei (AGNs). We argue that the answers to these puzzles may be linked to an interpretation of the data on the nanohertz gravitational waves (GWs) discovered by NANOGrav and other pulsar timing arrays as SMBH binaries whose evolution is driven by interactions with their environments down to <i>O<i/>(0.1 pc) separations. We show that the stellar mass-black hole mass correlations found in JWST data and in low-ɀ inactive galaxies are similar, and present a global fit to these data, excluding low-ɀ AGNs. Matching the NANOGrav and dual-AGN data requires that binary evolution due to environmental effects at separations below <i>O(<i/>1 kpc) be rapid on cosmological timescales. According to this interpretation, the SMBHs in low-ɀ AGNs are the tip of the iceberg of a local SMBH population in mainly inactive galaxies. This interpretation is consistent with the ‘little red dots’ observed with JWST being AGNs, and would favour the observability of GW signals from black hole binaries in LISA and decihertz GW detectors.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"172 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670329","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":"BASS","authors":"Kriti K. Gupta, Claudio Ricci, Matthew J. Temple, Alessia Tortosa, Michael J. Koss, Roberto J. Assef, Franz E. Bauer, Richard Mushotzy, Federica Ricci, Yoshihiro Ueda, Alejandra F. Rojas, Benny Trakhtenbrot, Chin-Shin Chang, Kyuseok Oh, Ruancun Li, Taiki Kawamuro, Yaherlyn Diaz, Meredith C. Powell, Daniel Stern, C. Megan Urry, Fiona Harrison, Brad Cenko","doi":"10.1051/0004-6361/202450567","DOIUrl":"https://doi.org/10.1051/0004-6361/202450567","url":null,"abstract":"We present one of the largest multiwavelength studies of simultaneous optical-to-X-ray spectral energy distributions (SEDs) of unobscured (<i>N<i/><sub>H<sub/> < 10<sup>22<sup/> cm<sup>−2<sup/>) active galactic nuclei (AGN) in the local Universe. Using a representative sample of hard-X-ray-selected AGN from the 70-month <i>Swift<i/>/BAT catalog, with optical/UV photometric data from <i>Swift<i/>/UVOT and X-ray spectral data from <i>Swift<i/>/XRT, we constructed broadband SEDs of 236 nearby AGN (0.001 < <i>z<i/> < 0.3). We employed GALFIT to estimate host galaxy contamination in the optical/UV and determine the intrinsic AGN fluxes. We used an absorbed power law with a reflection component to model the X-ray spectra and a dust-reddened multi-temperature blackbody to fit the optical/UV SED. We calculated intrinsic luminosities at multiple wavelengths, total bolometric luminosities (<i>L<i/><sub>bol<sub/>), optical-to-X-ray spectral indices (<i>α<i/><sub>ox<sub/>), and multiple bolometric corrections (<i>κ<i/><sub><i>λ<i/><sub/>) in the optical, UV, and X-rays. We used black hole masses obtained by reverberation mapping and the virial method to estimate Eddington ratios (<i>λ<i/><sub>Edd<sub/>) for all our AGN. We confirm the tight correlation (scatter = 0.45 dex) between UV (2500 Å) and X-ray (2 keV) luminosity for our sample. We observe a significant decrease in <i>α<i/><sub>ox<sub/> with <i>L<i/><sub>bol<sub/> and <i>λ<i/><sub>Edd<sub/>, suggesting that brighter sources emit more UV photons per X-rays. We report a second-order regression relation (scatter = 0.15 dex) between the 2–10 keV bolometric correction (<i>κ<i/><sub>2 − 10<sub/>) and <i>α<i/><sub>ox<sub/>, which is useful to compute <i>L<i/><sub>bol<sub/> in the absence of multiband SEDs. We also investigate the dependence of optical/UV bolometric corrections on the physical properties of AGN and obtain a significant increase in the UV bolometric corrections (<i>κ<i/><sub>W2<sub/> and <i>κ<i/><sub>M2<sub/>) with <i>L<i/><sub>bol<sub/> and <i>λ<i/><sub>Edd<sub/>, unlike those in the optical (<i>κ<i/><sub>V<sub/> and <i>κ<i/><sub>B<sub/>), which are constant across five orders of <i>L<i/><sub>bol<sub/> and <i>λ<i/><sub>Edd<sub/>. We obtain significant dispersions (∼0.1–1 dex) in all bolometric corrections, and hence recommend using appropriate relations with observed quantities while including the reported scatter, instead of their median values.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"11 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610421","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":"Contemporaneous high-angular-resolution imaging of the AGB star W Hya in vibrationally excited H2O lines and visible polarized light with ALMA and VLT/SPHERE-ZIMPOL","authors":"K. Ohnaka, K. T. Wong, G. Weigelt, K.-H. Hofmann","doi":"10.1051/0004-6361/202451977","DOIUrl":"https://doi.org/10.1051/0004-6361/202451977","url":null,"abstract":"<i>Aims.<i/> We present contemporaneous high-angular-resolution millimeter imaging and visible polarimetric imaging of the nearby asymptotic giant branch (AGB) star W Hya to better understand the dynamics and dust formation within a few stellar radii.<i>Methods.<i/> The star W Hya was observed in two vibrationally excited H<sub>2<sub/>O lines at 268 and 251 GHz with Atacama Large Millimeter/submillimeter Array (ALMA) at a spatial resolution of 16 × 20 mas and at 748 and 820 nm at a resolution of 26 × 27 mas with the Very Large Telescope (VLT)/Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE)-Zurich Imaging Polarimeter (ZIMPOL).<i>Results.<i/> ALMA’s high spatial resolution allowed us to image strong emission of the vibrationally excited H<sub>2<sub/>O line at 268 GHz (<i>v<i/><sub>2<sub/> = 2, <i>J<i/><sub><i>K<i/><sub><i>a<i/><sub/>, <i>K<i/><sub><i>c<i/><sub/><sub/> = 6<sub>5, 2<sub/>–7<sub>4, 3<sub/>) over the stellar surface instead of absorption against the continuum, which is expected for thermal excitation. Strong, spotty emission was also detected along and just outside the stellar disk limb at an angular distance of ∼40 mas (∼1.9 <i>R<i/><sub>⋆<sub/>), extending to ∼60 mas (∼2.9 <i>R<i/><sub>⋆<sub/>). Another H<sub>2<sub/>O line (<i>v<i/><sub>2<sub/> = 2, <i>J<i/><sub><i>K<i/><sub><i>a<i/><sub/>, <i>K<i/><sub><i>c<i/><sub/><sub/> = 9<sub>2, 8<sub/>–8<sub>3, 5<sub/>) at 251 GHz with a similar upper-level energy was tentatively identified, which shows absorption over the stellar surface. This suggests that the emission over the surface seen in the 268 GHz H<sub>2<sub/>O line is suprathermal or even maser emission. The estimated gas temperature and H<sub>2<sub/>O density are consistent with the radiatively pumped masers. The 268 GHz H<sub>2<sub/>O line reveals global infall at up to ∼15 km s<sup>−1<sup/> within 2–3 <i>R<i/><sub>⋆<sub/>, but outflows at up to ∼8 km s<sup>−1<sup/> are also present. The polarized intensity maps obtained in the visible reveal clumpy dust clouds forming within ∼40 mas (∼1.9 <i>R<i/><sub>⋆<sub/>) with a particularly prominent cloud in the SW quadrant and a weaker cloud in the east. The 268 GHz H<sub>2<sub/>O emission overlaps very well with the visible polarized intensity maps, which suggests that both the nonthermal and likely maser H<sub>2<sub/>O emission and the dust originate from dense, cool pockets in the inhomogeneous atmosphere within ∼2–3 <i>R<i/><sub>⋆<sub/>.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"128 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610564","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":"Performance comparison of the Shack-Hartmann and pyramid wavefront sensors with a laser guide star for 40 m telescopes","authors":"F. Oyarzún, C. Heritier, V. Chambouleyron, T. Fusco, P. Rouquette, B. Neichel","doi":"10.1051/0004-6361/202451670","DOIUrl":"https://doi.org/10.1051/0004-6361/202451670","url":null,"abstract":"<i>Context<i/>. Upcoming giant segmented mirror telescopes will use laser guide stars (LGS) for their adaptive optics (AO) systems. Two options of wavefront sensors (WFSs) are the Shack-Hartmann wavefront sensor (SHWFS) and the pyramid wavefront sensor (PWFS).<i>Aims<i/>. In this paper, we compare the noise performance of the PWFS and the SHWFS. We aim to identify which of the two is best to use in the context of a single or tomographic configuration.<i>Methods<i/>. To compute the noise performance, we extended a noise model developed for the PWFS to be used with the SHWFS. To do this, we expressed the centroiding algorithm of the SHWFS as a matrix-vector multiplication, which allowed us to use the statistics of noise to compute its propagation through the AO loop. We validated the noise model with end-to-end simulations for telescopes of 8 and 16 m in diameter.<i>Results<i/>. For an AO system with only one WFS, we found that given the same number of subapertures, the PWFS outperforms the SHWFS. For a 40 m telescope, the limiting magnitude of the PWFS is around one magnitude higher than the SHWFS. When using multiple WFS and a generalized least-squares estimator to combine the signal, our model predicts that in a tomographic system, the SHWFS performs better than the PWFS (with a limiting magnitude that is higher by a 0.3 magnitude. When using sub-electron RON detectors for the PWFS, the performance quality is almost identical for the two WFSs.<i>Conclusions<i/>. We find that when using a single WFS with LGS, PWFS is a better alternative than the SH. For a tomographic system, both sensors would give roughly the same performance.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"12 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610471","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":"Optimised use of interferometry, spectroscopy, and stellar atmosphere models for determining the fundamental parameters of stars","authors":"N. Ebrahimkutty, M. R. Gent, D. Mourard, A. Domiciano de Souza, M. Bergemann, T. Morel, G. Morello, N. Nardetto, B. Plez","doi":"10.1051/0004-6361/202450105","DOIUrl":"https://doi.org/10.1051/0004-6361/202450105","url":null,"abstract":"<i>Context<i/>. Thanks to recent progress in the field of optical interferometry, instrument sensitivities have now reached the level achieved in the domain of new space missions dedicated to exoplanet and stellar studies. Combining interferometry with other observational approaches enables the determination of stellar parameters and helps improve our understanding of stellar physics.<i>Aims<i/>. In this paper, we aim to demonstrate a new way of using stellar atmosphere models for a joint interpretation of spectroscopic and interferometric observations.<i>Methods<i/>. Starting from a discrete grid of one-dimensional (1D) stellar atmosphere models, we developed a training algorithm, based on an artificial neural network, capable of estimating the spectrum and intensity profile of a star over a range of wavelengths and viewing angles. A minimisation algorithm based on the trained function allowed for the simultaneous fitting of the observational spectrum and interferometric complex visibilities. As a result, coherent and precise stellar parameters can be extracted.<i>Results<i/>. We show the ability of the trained function to match the modelled intensity profiles of stars in the effective temperature range of 4500–7000 K and surface gravity range of 3 to 5 dex, with a relative precision to the model that is better than 0.05%. Using simulated interferometric data and actual spectroscopic measurements, we demonstrated the performance of our algorithm on a sample of five benchmark stars. Using this method, we achieved an accuracy within 0.5% for the angular diameter, radius, and surface gravity, and within 20 K for the effective temperature.<i>Conclusions<i/>. This paper demonstrates a new method of using interferometric data combined with spectroscopic observations. This approach offers an improved determination of the radius, effective temperature, and surface gravity of stars.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"163 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610552","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":"A Tale of NGC 3785: The formation of an ultra-diffuse galaxy at the end of the longest tidal tail","authors":"Chandan Watts, Sudhanshu Barway, Omkar Bait, Yogesh Wadadekar","doi":"10.1051/0004-6361/202452002","DOIUrl":"https://doi.org/10.1051/0004-6361/202452002","url":null,"abstract":"<i>Aims.<i/> We present the discovery of an extended and faint tail observed in the isolated environment associated with galaxy NGC 3785. This study additionally provides observational evidence supporting the formation of ultra-diffuse galaxies (UDGs) at the end of the tail.<i>Methods.<i/> We utilized the Gnuastro software to detect and analyze the low surface brightness structures in the optical <i>g<i/>- and <i>r<i/>-bands using data from the Dark Energy Camera Legacy Survey. We created a detection map to identify the faint tail and measured its length using cubic spline fitting. Additionally, we found 84 star-forming clumps along the tail and performed photometric analysis on the tail portion after applying a significance threshold on the signal-to-noise ratio.<i>Results.<i/> We have measured the projected length of the tail, which is ∼390 kpc. We propose that this tail arises from the interaction of the NGC 3785 with a gas-rich galaxy, which ends up as a UDG at the end of the tail.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"44 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610477","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":"Venusian ion escape under extreme conditions: A dynamic pressure and temperature simulation study","authors":"M. C. Katrougkalou, M. Persson, S. Aizawa, N. André, R. Modolo, E. Jariel, A. Kullen, T. Karlsson","doi":"10.1051/0004-6361/202449326","DOIUrl":"https://doi.org/10.1051/0004-6361/202449326","url":null,"abstract":"<i>Context<i/>. We investigated the response of the Venusian atmospheric ion escape under the effect of interplanetary coronal mass ejections (ICMEs) using the Latmos Hybrid Simulation (LatHyS).<i>Aims<i/>. In particular, we focused on the influence of extreme ICME dynamic pressures and temperatures, with the temperature being a parameter that has not been extensively studied in the past.<i>Methods<i/>. Simulations were performed for two different dynamic pressures and three different temperatures. For the case of the dynamic pressure simulations, a density and a velocity enhancement event were studied separately. The H<sup>+<sup/> and O<sup>+<sup/> ion escape was then examined and compared for different escape channels.<i>Results<i/>. In both dynamic pressure enhancement cases, we find that there is no clear dependence of the O<sup>+<sup/> ion escape on the dynamic pressure, which is consistent with observations. On the other hand, the temperature of the incoming solar wind positively influences the H<sup>+<sup/> and O<sup>+<sup/> ion escape. This is attributed in part to the enhanced gyroradius of the particles, which allows them to penetrate deeper into the planet’s atmosphere.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"25 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610362","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}