Pub Date : 2025-01-15DOI: 10.1051/0004-6361/202452977
Daniel Félix-González, Pablo del Mazo-Sevillano, Alfredo Aguado, Octavio Roncero, Jacques Le Bourlot, Evelyne Roueff, Franck Le Petit, Emeric Bron
Context. In diffuse interstellar clouds, the excitation temperature derived from the lowest levels of H3+ is systematically lower than that derived from H2. The differences may be attributed to the lack of state-specific formation and destruction rates of H3+, which are needed to thermalize the two species.Aims. In this work, we aim to investigate the possible influence of rotational excitation collisions of H3+ with atomic hydrogen on its excitation temperature.Methods. We used a time-independent close-coupling method to calculate the state-to-state rate coefficients, incorporating a very accurate and full-dimensional potential energy surface recently developed for H4+. We take a symmetric top approach to describe a frozen H3+ as an equilateral triangle.Results. We derive rotational excitation collision rate coefficients of H3+ with atomic hydrogen in a temperature range corresponding to diffuse interstellar conditions up to (J, K, ±) = (7, 6, +) and (J, K, ±) = (6, 4, +) for its ortho and para forms. This allows us to obtain a consistent set of collisional excitation rate coefficients and to improve on a previous study that included speculations regarding these contributions.Conclusions. The new state-specific inelastic H3+ + H rate coefficients yield differences of up to 20% in the excitation temperature, and their impact increases with decreasing molecular fraction. We also confirm the impact of chemical state-to-state destruction reactions on the excitation balance of H3+, and that reactive H + H3+ collisions are also needed to account for possible further ortho to para transitions.
{"title":"Inelastic H + H3+ collision rates and their impact on the determination of the excitation temperature of H3+","authors":"Daniel Félix-González, Pablo del Mazo-Sevillano, Alfredo Aguado, Octavio Roncero, Jacques Le Bourlot, Evelyne Roueff, Franck Le Petit, Emeric Bron","doi":"10.1051/0004-6361/202452977","DOIUrl":"https://doi.org/10.1051/0004-6361/202452977","url":null,"abstract":"<i>Context.<i/> In diffuse interstellar clouds, the excitation temperature derived from the lowest levels of H<sub>3<sub/><sup>+<sup/> is systematically lower than that derived from H<sub>2<sub/>. The differences may be attributed to the lack of state-specific formation and destruction rates of H<sub>3<sub/><sup>+<sup/>, which are needed to thermalize the two species.<i>Aims.<i/> In this work, we aim to investigate the possible influence of rotational excitation collisions of H<sub>3<sub/><sup>+<sup/> with atomic hydrogen on its excitation temperature.<i>Methods.<i/> We used a time-independent close-coupling method to calculate the state-to-state rate coefficients, incorporating a very accurate and full-dimensional potential energy surface recently developed for H<sub>4<sub/><sup>+<sup/>. We take a symmetric top approach to describe a frozen H<sub>3<sub/><sup>+<sup/> as an equilateral triangle.<i>Results.<i/> We derive rotational excitation collision rate coefficients of H<sub>3<sub/><sup>+<sup/> with atomic hydrogen in a temperature range corresponding to diffuse interstellar conditions up to (<i>J, K<i/>, ±) = (7, 6, +) and (<i>J, K<i/>, ±) = (6, 4, +) for its ortho and para forms. This allows us to obtain a consistent set of collisional excitation rate coefficients and to improve on a previous study that included speculations regarding these contributions.<i>Conclusions.<i/> The new state-specific inelastic H<sub>3<sub/><sup>+<sup/> + H rate coefficients yield differences of up to 20% in the excitation temperature, and their impact increases with decreasing molecular fraction. We also confirm the impact of chemical state-to-state destruction reactions on the excitation balance of H<sub>3<sub/><sup>+<sup/>, and that reactive H + H<sub>3<sub/><sup>+<sup/> collisions are also needed to account for possible further ortho to para transitions.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"45 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986200","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}
Pub Date : 2025-01-15DOI: 10.1051/0004-6361/202451385
J. L. Cano, M. Micheli, P. Ramírez-Moreta, T. Hoffmann, L. Conversi, M. Fenucci, D. Oliviero, F. Ocaña
Context. The observability of an asteroid from the ground depends on the distance to the Sun and the observer, on the phase angle, on the object shape, and on its surface reflectivity properties. Several magnitude systems have been proposed in the past decades to model the visual magnitude of the object based on these parameters.Aims. Independently of the magnitude system, there is a three-dimensional representation of the geometrical locus of equal visual magnitude when this value is constrained for a given asteroid. We called this the detection polar curve, or just, the detection polar. We derived a process in order to represent it graphically.Methods. We analysed the shape of this geometrical locus for the H, G magnitude system and determined its applicability to the representation of the detectability of an asteroid in its trajectory. We thus calculated the asteroid detection polar equation, as well as the threshold values that change the type of asteroid detectability solution.Results. The resulting detection polar is discussed, the synodic orbit visualisation tool is introduced, as are examples of how it can be used to analyse the graphical representation of an asteroid trajectory, and to represent the detection polar for a given limiting visual magnitude.
{"title":"Asteroid detection polar equation calculation and graphical representation","authors":"J. L. Cano, M. Micheli, P. Ramírez-Moreta, T. Hoffmann, L. Conversi, M. Fenucci, D. Oliviero, F. Ocaña","doi":"10.1051/0004-6361/202451385","DOIUrl":"https://doi.org/10.1051/0004-6361/202451385","url":null,"abstract":"<i>Context.<i/> The observability of an asteroid from the ground depends on the distance to the Sun and the observer, on the phase angle, on the object shape, and on its surface reflectivity properties. Several magnitude systems have been proposed in the past decades to model the visual magnitude of the object based on these parameters.<i>Aims.<i/> Independently of the magnitude system, there is a three-dimensional representation of the geometrical locus of equal visual magnitude when this value is constrained for a given asteroid. We called this the detection polar curve, or just, the detection polar. We derived a process in order to represent it graphically.<i>Methods.<i/> We analysed the shape of this geometrical locus for the <i>H, G<i/> magnitude system and determined its applicability to the representation of the detectability of an asteroid in its trajectory. We thus calculated the asteroid detection polar equation, as well as the threshold values that change the type of asteroid detectability solution.<i>Results.<i/> The resulting detection polar is discussed, the synodic orbit visualisation tool is introduced, as are examples of how it can be used to analyse the graphical representation of an asteroid trajectory, and to represent the detection polar for a given limiting visual magnitude.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"37 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986203","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}
Pub Date : 2025-01-15DOI: 10.1051/0004-6361/202452800
Diego Calderón, Jorge Cuadra, Christopher M. P. Russell, Andreas Burkert, Stephan Rosswog, Mayura Balakrishnan
Context. The reported discovery of a cold (~104 K) disc-like structure within the central 5 × 10−3 pc around the super-massive black hole at the centre of the Milk Way, Sagittarius A* (Sgr A*), has challenged our understanding of the gas dynamics and thermodynamic state of the plasma in its immediate vicinity. State-of-the-art simulations do not agree on whether or not such a disc can indeed be a product of the multiple stellar wind interactions of the mass-losing stars in the region.Aims. The aims of this study are to constrain the conditions for the formation of a cold disc as a natural outcome of the system of the mass-losing stars orbiting around Sgr A*, to investigate whether the disc is a transient or long-lasting structure, and to assess the validity of the model through direct comparisons with observations.Methods. We performed a set of hydrodynamic simulations of the observed Wolf-Rayet (WR) stars feeding Sgr A* using the finite- volume adaptive mesh refinement code Ramses. We focus, for the first time, on the impact of the chemical composition of the plasma emanating from the WR stars.Results. The simulations show that the chemical composition of the plasma affects the radiative cooling to a sufficient degree to impact the properties of the medium, such as density and temperature, and, as a consequence, the rate at which the material inflows onto Sgr A*. We demonstrate that the formation of a cold disc from the stellar winds is possible for certain chemical compositions that are consistent with the current observational constraints. However, even in such cases, it is not possible to reproduce the reported properties of the observed disc-like structure, namely its inclination and the fluxes of its hydrogen recombination lines.Conclusions. We conclude that the stellar winds alone are not sufficient to form the cold disc around Sgr A* inferred from observations. Either relevant ingredients are still missing in the model, or the interpretation of the observed data needs to be revised.
{"title":"The formation and stability of a cold disc made out of stellar winds in the Galactic centre","authors":"Diego Calderón, Jorge Cuadra, Christopher M. P. Russell, Andreas Burkert, Stephan Rosswog, Mayura Balakrishnan","doi":"10.1051/0004-6361/202452800","DOIUrl":"https://doi.org/10.1051/0004-6361/202452800","url":null,"abstract":"<i>Context<i/>. The reported discovery of a cold (~10<sup>4<sup/> K) disc-like structure within the central 5 × 10<sup>−3<sup/> pc around the super-massive black hole at the centre of the Milk Way, Sagittarius A* (Sgr A*), has challenged our understanding of the gas dynamics and thermodynamic state of the plasma in its immediate vicinity. State-of-the-art simulations do not agree on whether or not such a disc can indeed be a product of the multiple stellar wind interactions of the mass-losing stars in the region.<i>Aims<i/>. The aims of this study are to constrain the conditions for the formation of a cold disc as a natural outcome of the system of the mass-losing stars orbiting around Sgr A*, to investigate whether the disc is a transient or long-lasting structure, and to assess the validity of the model through direct comparisons with observations.<i>Methods<i/>. We performed a set of hydrodynamic simulations of the observed Wolf-Rayet (WR) stars feeding Sgr A* using the finite- volume adaptive mesh refinement code Ramses. We focus, for the first time, on the impact of the chemical composition of the plasma emanating from the WR stars.<i>Results<i/>. The simulations show that the chemical composition of the plasma affects the radiative cooling to a sufficient degree to impact the properties of the medium, such as density and temperature, and, as a consequence, the rate at which the material inflows onto Sgr A*. We demonstrate that the formation of a cold disc from the stellar winds is possible for certain chemical compositions that are consistent with the current observational constraints. However, even in such cases, it is not possible to reproduce the reported properties of the observed disc-like structure, namely its inclination and the fluxes of its hydrogen recombination lines.<i>Conclusions<i/>. We conclude that the stellar winds alone are not sufficient to form the cold disc around Sgr A* inferred from observations. Either relevant ingredients are still missing in the model, or the interpretation of the observed data needs to be revised.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"10 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986204","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}
Pub Date : 2025-01-15DOI: 10.1051/0004-6361/202348177
Nolan Grieves, François Bouchy, David J. Armstrong, Babatunde Akinsanmi, Angelica Psaridi, Solène Ulmer-Moll, Yolanda G. C. Frensch, Ravit Helled, Simon Müller, Henrik Knierim, Nuno C. Santos, Vardan Adibekyan, Léna Parc, Monika Lendl, Matthew P. Battley, Nicolas Unger, Guillaume Chaverot, Daniel Bayliss, Xavier Dumusque, Faith Hawthorn, Pedro Figueira, Marcelo Aron Fetzner Keniger, Jorge Lillo-Box, Louise Dyregaard Nielsen, Ares Osborn, Sérgio G. Sousa, Paul Strøm, Stéphane Udry
Hot Jupiters generally do not have nearby planet companions, as they may have cleared out other planets during their inward migration from more distant orbits. This gives evidence that hot Jupiters more often migrate inward via high-eccentricity migration due to dynamical interactions between planets rather than more dynamically cool migration mechanisms through the protoplanetary disk. Here we further refine the unique system of WASP-132 by characterizing the mass of the recently validated 1.0-day period super-Earth WASP-132c (TOI-822.02), interior to the 7.1-day period hot Jupiter WASP-132b. Additionally, we announce the discovery of a giant planet at a 5-year period (2.7 AU). We also detected a long-term trend in the radial velocity data indicative of another outer companion. Using over nine years of CORALIE radial velocities (RVs) and over two months of highly sampled HARPS RVs, we determined the masses of the planets from smallest to largest orbital period to be , and , respectively. Using TESS and CHEOPS photometry data, we measured the radii of the two inner transiting planets to be and . We find a bulk density of for WASP-132c, which is slightly above the Earth-like composition line on the mass-radius diagram. WASP-132 is a unique multi-planetary system in that both an inner rocky planet and an outer giant planet are in a system with a hot Jupiter. This suggests it migrated via a rarer dynamically cool mechanism and helps to further our understanding of how hot Jupiter systems form and evolve.
{"title":"Discovery of a cold giant planet and mass measurement of a hot super-Earth in the multi-planetary system WASP-132","authors":"Nolan Grieves, François Bouchy, David J. Armstrong, Babatunde Akinsanmi, Angelica Psaridi, Solène Ulmer-Moll, Yolanda G. C. Frensch, Ravit Helled, Simon Müller, Henrik Knierim, Nuno C. Santos, Vardan Adibekyan, Léna Parc, Monika Lendl, Matthew P. Battley, Nicolas Unger, Guillaume Chaverot, Daniel Bayliss, Xavier Dumusque, Faith Hawthorn, Pedro Figueira, Marcelo Aron Fetzner Keniger, Jorge Lillo-Box, Louise Dyregaard Nielsen, Ares Osborn, Sérgio G. Sousa, Paul Strøm, Stéphane Udry","doi":"10.1051/0004-6361/202348177","DOIUrl":"https://doi.org/10.1051/0004-6361/202348177","url":null,"abstract":"Hot Jupiters generally do not have nearby planet companions, as they may have cleared out other planets during their inward migration from more distant orbits. This gives evidence that hot Jupiters more often migrate inward via high-eccentricity migration due to dynamical interactions between planets rather than more dynamically cool migration mechanisms through the protoplanetary disk. Here we further refine the unique system of WASP-132 by characterizing the mass of the recently validated 1.0-day period super-Earth WASP-132c (TOI-822.02), interior to the 7.1-day period hot Jupiter WASP-132b. Additionally, we announce the discovery of a giant planet at a 5-year period (2.7 AU). We also detected a long-term trend in the radial velocity data indicative of another outer companion. Using over nine years of CORALIE radial velocities (RVs) and over two months of highly sampled HARPS RVs, we determined the masses of the planets from smallest to largest orbital period to be , and , respectively. Using TESS and CHEOPS photometry data, we measured the radii of the two inner transiting planets to be and . We find a bulk density of for WASP-132c, which is slightly above the Earth-like composition line on the mass-radius diagram. WASP-132 is a unique multi-planetary system in that both an inner rocky planet and an outer giant planet are in a system with a hot Jupiter. This suggests it migrated via a rarer dynamically cool mechanism and helps to further our understanding of how hot Jupiter systems form and evolve.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"7 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986134","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}
Pub Date : 2025-01-15DOI: 10.1051/0004-6361/202449986
Bin Liu, Cunhui Li, Zhongcheng Mu, Xiaodong Liu
The main-belt asteroid 2010 LH15 has been classified as an active asteroid, based on the recent discovery of dust activity from the archival images observed in 2010 and 2019. In this study, we perform measurements and dynamical modeling of the dust tail of the active asteroid 2010 LH15 using ZTF archival data from July 26 to August 31, 2019, with the derived physical properties from these relatively independent methods being compatible. The photometric results show that the radius of the nucleus is 1.11 ± 0.02 km, with an assumed geometric albedo of pr = 0.05, and the color index of the nucleus is relatively close to that of the ejecta around the nucleus, with a value of Hg − Hr = 0.44 ± 0.07. The effective scattering cross section increases at an average rate of 0.28 ± 0.02 km2 day−1 throughout the observation period, indicating that the activity of LH15 is likely driven by mechanisms capable of causing a sustained process like sublimation. Further dust dynamics modeling indicates that the dust activity initiates as early as about June 26, 2019, with the ejected dust particles having a radius ranging from 0.03 mm to 3 mm. The dependence of the terminal velocity on dust size is consistent with a sublimation-driven mechanism. If the orbit of LH15 is stable, its sublimation origin will extend the inner boundary of the water-ice-bearing region in the main asteroid belt inward by approximately 0.1 AU.
{"title":"Physical properties of newly active asteroid 2010 LH15","authors":"Bin Liu, Cunhui Li, Zhongcheng Mu, Xiaodong Liu","doi":"10.1051/0004-6361/202449986","DOIUrl":"https://doi.org/10.1051/0004-6361/202449986","url":null,"abstract":"The main-belt asteroid 2010 LH<sub>15<sub/> has been classified as an active asteroid, based on the recent discovery of dust activity from the archival images observed in 2010 and 2019. In this study, we perform measurements and dynamical modeling of the dust tail of the active asteroid 2010 LH<sub>15<sub/> using ZTF archival data from July 26 to August 31, 2019, with the derived physical properties from these relatively independent methods being compatible. The photometric results show that the radius of the nucleus is 1.11 ± 0.02 km, with an assumed geometric albedo of <i>p<sub>r<sub/><i/> = 0.05, and the color index of the nucleus is relatively close to that of the ejecta around the nucleus, with a value of <i>H<sub>g<sub/><i/> − <i>H<sub>r<sub/><i/> = 0.44 ± 0.07. The effective scattering cross section increases at an average rate of 0.28 ± 0.02 km<sup>2<sup/> day<sup>−1<sup/> throughout the observation period, indicating that the activity of LH<sub>15<sub/> is likely driven by mechanisms capable of causing a sustained process like sublimation. Further dust dynamics modeling indicates that the dust activity initiates as early as about June 26, 2019, with the ejected dust particles having a radius ranging from 0.03 mm to 3 mm. The dependence of the terminal velocity on dust size is consistent with a sublimation-driven mechanism. If the orbit of LH<sub>15<sub/> is stable, its sublimation origin will extend the inner boundary of the water-ice-bearing region in the main asteroid belt inward by approximately 0.1 AU.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"2 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986199","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}
Context. Given their high luminosities (L ≳ 104L⊙), red supergiants (RSGs) are good tracers of the chemical abundances of the young stellar population in the Milky Way and nearby galaxies. However, previous abundance analyses tailored to RSGs suffer some systematic uncertainties originating in, most notably, the synthesized molecular spectral lines for RSGs.Aims. We establish a new abundance analysis procedure for RSGs that circumvents difficulties faced in previous works, and test the procedure with ten nearby RSGs observed with the near-infrared high-resolution spectrograph WINERED (0.97−1.32 µm, R = 28 000). The wavelength range covered here is advantageous in that the molecular lines contaminating atomic lines of interest are mostly weak.Methods. We first determined the effective temperatures (Teff) of the targets with the line-depth ratio (LDR) method, and calculated the surface gravities (log 𝑔) according to the Stefan-Boltzmann law. We then determined the microturbulent velocities (vmicro) and metallicities ([Fe/H]) simultaneously through the fitting of individual Fe I lines. Finally, we also determined the abundance ratios ([X/Fe] for element X) through the fitting of individual lines.Results. We determined the [X/Fe] of ten elements (Na I, Mg I, Al I, Si I, K I, Ca I, Ti I, Cr I, Ni I, and Y II). We estimated the relative precision in the derived abundances to be 0.04−0.12 dex for elements with more than two lines analyzed (e.g., Fe I and Mg I) and up to 0.18dex for the other elements (e.g., Y II). We compared the resultant abundances of RSGs with the well-established abundances of another type of young star, namely the Cepheids, in order to evaluate the potential systematic bias in our abundance measurements, assuming that the young stars (i.e., both RSGs and Cepheids) in the solar neighborhood have common chemical abundances. We find that the determined RSG abundances are highly consistent with those of Cepheids within <0.1 dex for some elements (notably [Fe/H] and [Mg/Fe]), which means the bias in the abundance determination for these elements is likely to be small. In contrast, the consistency is worse for some other elements (e.g., [Si/Fe] and [Y/Fe]). Nevertheless, the dispersion of the chemical abundances among our target RSGs is comparable with the individual statistical errors on the abundances. Hence, the procedure is likely to be useful to evaluate the relative difference in chemical abundances among RSGs.
{"title":"MAGIS (Measuring Abundances of red super Giants with Infrared Spectroscopy) project","authors":"Daisuke Taniguchi, Noriyuki Matsunaga, Naoto Kobayashi, Mingjie Jian, Brian Thorsbro, Kei Fukue, Satoshi Hamano, Yuji Ikeda, Hideyo Kawakita, Sohei Kondo, Shogo Otsubo, Hiroaki Sameshima, Takuji Tsujimoto, Chikako Yasui","doi":"10.1051/0004-6361/202452392","DOIUrl":"https://doi.org/10.1051/0004-6361/202452392","url":null,"abstract":"<i>Context<i/>. Given their high luminosities (<i>L<i/> ≳ 10<sup>4<sup/> <i>L<i/><sub>⊙<sub/>), red supergiants (RSGs) are good tracers of the chemical abundances of the young stellar population in the Milky Way and nearby galaxies. However, previous abundance analyses tailored to RSGs suffer some systematic uncertainties originating in, most notably, the synthesized molecular spectral lines for RSGs.<i>Aims<i/>. We establish a new abundance analysis procedure for RSGs that circumvents difficulties faced in previous works, and test the procedure with ten nearby RSGs observed with the near-infrared high-resolution spectrograph WINERED (0.97−1.32 µm, <i>R<i/> = 28 000). The wavelength range covered here is advantageous in that the molecular lines contaminating atomic lines of interest are mostly weak.<i>Methods<i/>. We first determined the effective temperatures (<i>T<i/><sub>eff<sub/>) of the targets with the line-depth ratio (LDR) method, and calculated the surface gravities (log 𝑔) according to the Stefan-Boltzmann law. We then determined the microturbulent velocities (<i>v<i/><sub>micro<sub/>) and metallicities ([Fe/H]) simultaneously through the fitting of individual Fe I lines. Finally, we also determined the abundance ratios ([X/Fe] for element X) through the fitting of individual lines.<i>Results<i/>. We determined the [X/Fe] of ten elements (Na I, Mg I, Al I, Si I, K I, Ca I, Ti I, Cr I, Ni I, and Y II). We estimated the relative precision in the derived abundances to be 0.04−0.12 dex for elements with more than two lines analyzed (e.g., Fe I and Mg I) and up to 0.18dex for the other elements (e.g., Y II). We compared the resultant abundances of RSGs with the well-established abundances of another type of young star, namely the Cepheids, in order to evaluate the potential systematic bias in our abundance measurements, assuming that the young stars (i.e., both RSGs and Cepheids) in the solar neighborhood have common chemical abundances. We find that the determined RSG abundances are highly consistent with those of Cepheids within <0.1 dex for some elements (notably [Fe/H] and [Mg/Fe]), which means the bias in the abundance determination for these elements is likely to be small. In contrast, the consistency is worse for some other elements (e.g., [Si/Fe] and [Y/Fe]). Nevertheless, the dispersion of the chemical abundances among our target RSGs is comparable with the individual statistical errors on the abundances. Hence, the procedure is likely to be useful to evaluate the relative difference in chemical abundances among RSGs.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"51 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986133","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}
Pub Date : 2025-01-14DOI: 10.1051/0004-6361/202453208
Lukas Neumann, María J. Jiménez-Donaire, Adam K. Leroy, Frank Bigiel, Antonio Usero, Jiayi Sun, Eva Schinnerer, Miguel Querejeta, Sophia K. Stuber, Ivana Bešlić, Ashley Barnes, Jakob den Brok, Yixian Cao, Cosima Eibensteiner, Hao He, Ralf S. Klessen, Fu-Heng Liang, Daizhong Liu, Hsi-An Pan, Thomas G. Williams
Dense, cold gas is the key ingredient for star formation. Over the last two decades, HCN(1 − 0) emission has been the most accessible dense gas tracer for studying external galaxies. We present new measurements that demonstrate the relationship between dense gas tracers, bulk molecular gas tracers, and star formation in the ALMA ALMOND survey, the largest sample of resolved (1–2 kpc resolution) HCN maps of galaxies in the local Universe (d < 25 Mpc). We measured HCN/CO, a line ratio sensitive to the physical density distribution, and the star formation rate to HCN ratio (SFR/HCN), a proxy for the dense gas star formation efficiency, as a function of molecular gas surface density, stellar mass surface density, and dynamical equilibrium pressure across 31 galaxies (a factor of > 3 more compared to the previously largest such study, EMPIRE). HCN/CO increases (slope of ≈0.5 and scatter of ≈0.2 dex) and SFR/HCN decreases (slope of ≈ − 0.6 and scatter of ≈0.4 dex) with increasing molecular gas surface density, stellar mass surface density, and pressure. Galaxy centres with high stellar mass surface densities show a factor of a few higher HCN/CO and lower SFR/HCN compared to the disc average, but the two environments follow the same average trend. Our results emphasise that molecular gas properties vary systematically with the galactic environment and demonstrate that the scatter in the Gao–Solomon relation (SFR/HCN) has a physical origin.
{"title":"Dense gas scaling relations at kiloparsec scales across nearby galaxies with the ALMA ALMOND and IRAM 30 m EMPIRE surveys","authors":"Lukas Neumann, María J. Jiménez-Donaire, Adam K. Leroy, Frank Bigiel, Antonio Usero, Jiayi Sun, Eva Schinnerer, Miguel Querejeta, Sophia K. Stuber, Ivana Bešlić, Ashley Barnes, Jakob den Brok, Yixian Cao, Cosima Eibensteiner, Hao He, Ralf S. Klessen, Fu-Heng Liang, Daizhong Liu, Hsi-An Pan, Thomas G. Williams","doi":"10.1051/0004-6361/202453208","DOIUrl":"https://doi.org/10.1051/0004-6361/202453208","url":null,"abstract":"Dense, cold gas is the key ingredient for star formation. Over the last two decades, HCN(1 − 0) emission has been the most accessible dense gas tracer for studying external galaxies. We present new measurements that demonstrate the relationship between dense gas tracers, bulk molecular gas tracers, and star formation in the ALMA ALMOND survey, the largest sample of resolved (1–2 kpc resolution) HCN maps of galaxies in the local Universe (<i>d<i/> < 25 Mpc). We measured HCN/CO, a line ratio sensitive to the physical density distribution, and the star formation rate to HCN ratio (SFR/HCN), a proxy for the dense gas star formation efficiency, as a function of molecular gas surface density, stellar mass surface density, and dynamical equilibrium pressure across 31 galaxies (a factor of > 3 more compared to the previously largest such study, EMPIRE). HCN/CO increases (slope of ≈0.5 and scatter of ≈0.2 dex) and SFR/HCN decreases (slope of ≈ − 0.6 and scatter of ≈0.4 dex) with increasing molecular gas surface density, stellar mass surface density, and pressure. Galaxy centres with high stellar mass surface densities show a factor of a few higher HCN/CO and lower SFR/HCN compared to the disc average, but the two environments follow the same average trend. Our results emphasise that molecular gas properties vary systematically with the galactic environment and demonstrate that the scatter in the Gao–Solomon relation (SFR/HCN) has a physical origin.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"47 15 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986198","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}
Pub Date : 2025-01-14DOI: 10.1051/0004-6361/202453197
Klaus Werner, Nicole Reindl, Max Pritzkuleit, Stephan Geier
We have detected three new hydrogen-deficient (H < 0.001 mass fraction) pre-white dwarfs (WDs) with helium-dominated atmospheres. The first object is a relatively cool PG1159 star (effective temperature Teff = 72 000 K) that has the lowest surface gravity of any PG1159 star known (log g = 4.8). It is a PG1159 star in the earliest pre-WD phase. The second object is a hot subdwarf O (sdO) star (Teff = 50 000 K, log g = 5.3) with high carbon and oxygen abundances. It is only the third known member of the recently established CO-sdO spectral class, which comprises stars that are thought to be formed by a merger of a disrupted low-mass CO WD with a higher-mass He WD. The third object is one of the rare stars of spectral type O(He) (Teff = 90 000 K, log g = 5.5).
{"title":"Three new hot hydrogen-deficient pre-white dwarfs","authors":"Klaus Werner, Nicole Reindl, Max Pritzkuleit, Stephan Geier","doi":"10.1051/0004-6361/202453197","DOIUrl":"https://doi.org/10.1051/0004-6361/202453197","url":null,"abstract":"We have detected three new hydrogen-deficient (H < 0.001 mass fraction) pre-white dwarfs (WDs) with helium-dominated atmospheres. The first object is a relatively cool PG1159 star (effective temperature <i>T<i/><sub>eff<sub/> = 72 000 K) that has the lowest surface gravity of any PG1159 star known (log <i>g<i/> = 4.8). It is a PG1159 star in the earliest pre-WD phase. The second object is a hot subdwarf O (sdO) star (<i>T<i/><sub>eff<sub/> = 50 000 K, log <i>g<i/> = 5.3) with high carbon and oxygen abundances. It is only the third known member of the recently established CO-sdO spectral class, which comprises stars that are thought to be formed by a merger of a disrupted low-mass CO WD with a higher-mass He WD. The third object is one of the rare stars of spectral type O(He) (<i>T<i/><sub>eff<sub/> = 90 000 K, log <i>g<i/> = 5.5).","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"41 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986135","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}
Aims. We discovered that the changing-look active galactic nucleus (CLAGN) SDSS J101152.98+544206.4 (J1011+5442 for short) gradually returns to the type I state after a short period between 2014 and 2019 in the faint type 1.9 state.Methods. Motivated by the rebrightening in the optical and mid-infrared light curves from ZTF and WISE, we obtained new spectroscopic observations with the Xinglong 2.16 m, the Lijiang 2.4 m, and the MMT 6.5 m optical telescopes in 2024.Results. After changing its optical AGN type from 1 to 1.9 between 2003 and 2015 according to the repeat spectroscopy from the Time Domain Spectroscopic Survey, J1011+5442 returned to its type I state in 2024. We detect the significant and very broad Hβ lines (full width at half maximum of ≳5000 km/s) based on the new spectra, which suggests that J1011+5442 was in the intermediate state between the dim state in 2015 and the bright state in 2003. The long-term optical and mid-infrared light curves also show a brightening trend between 2019 and 2024 as the broad Hβ line appeared. The time lag of about 100 days between the mid-infrared and optical variability is consistent with the prediction of dust reverberation mapping.Conclusions. The behavior of the photometric and spectroscopic observations of J1011+5442 is consistent with the argument that the repeating changing-look phenomenon is regulated by the variation in the accretion rate.
{"title":"The changing-look AGN SDSS J101152.98+544206.4 is returning to a type I state","authors":"Bing Lyu, Xue-Bing Wu, Yuxuan Pang, Huimei Wang, Rui Zhu, Yuming Fu, Qingwen Wu, Zhen Yan, Wenfei Yu, Hao Liu, Shi-Ju Kang, Junjie Jin, Jinyi Yang, Feige Wang","doi":"10.1051/0004-6361/202451699","DOIUrl":"https://doi.org/10.1051/0004-6361/202451699","url":null,"abstract":"<i>Aims.<i/> We discovered that the changing-look active galactic nucleus (CLAGN) SDSS J101152.98+544206.4 (J1011+5442 for short) gradually returns to the type I state after a short period between 2014 and 2019 in the faint type 1.9 state.<i>Methods.<i/> Motivated by the rebrightening in the optical and mid-infrared light curves from ZTF and WISE, we obtained new spectroscopic observations with the Xinglong 2.16 m, the Lijiang 2.4 m, and the MMT 6.5 m optical telescopes in 2024.<i>Results.<i/> After changing its optical AGN type from 1 to 1.9 between 2003 and 2015 according to the repeat spectroscopy from the Time Domain Spectroscopic Survey, J1011+5442 returned to its type I state in 2024. We detect the significant and very broad H<i>β<i/> lines (full width at half maximum of ≳5000 km/s) based on the new spectra, which suggests that J1011+5442 was in the intermediate state between the dim state in 2015 and the bright state in 2003. The long-term optical and mid-infrared light curves also show a brightening trend between 2019 and 2024 as the broad H<i>β<i/> line appeared. The time lag of about 100 days between the mid-infrared and optical variability is consistent with the prediction of dust reverberation mapping.<i>Conclusions.<i/> The behavior of the photometric and spectroscopic observations of J1011+5442 is consistent with the argument that the repeating changing-look phenomenon is regulated by the variation in the accretion rate.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"31 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986137","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}
Pub Date : 2025-01-14DOI: 10.1051/0004-6361/202452861
G. Valle, M. Dell’Omodarme, P. G. Prada Moroni, S. Degl’Innocenti
Context. A recent investigation highlighted peculiar trends between the radii derived from surface brightness-colour relations (SBCRs) combined with Gaia DR3 parallaxes with respect to asteroseismic scaling relation radii from K2 data.Aims.Kepler data differ from K2 data in many aspects. We investigated on the robustness of the results based on Kepler data.Methods. We cross-matched asteroseismic and astrometric data for over 12 000 red giant branch and red clump stars from the end-of-mission Kepler catalogue with the Gaia DR3 and TESS Input Catalogue v8.2 to obtain precise parallaxes, V- and K-band magnitudes, and E(B − V) colour excesses. Two well-tested SBCRs from the literature were adopted to estimate stellar radii.Results. The analysis confirmed that SBCR and asteroseismic radii agree very well. The overall differences are only 1–2% depending on the adopted SBCR. The dispersion of 7% was about two-thirds of what was found for K2-based data. As a difference from the K2-based investigation, the ratio of SBCRs-to-asteroseismic radii did not depend on the metallicity [Fe/H]. Moreover, the intriguing decreasing trend with [α/Fe] of the radius ratio for massive stars that was observed in K2 data was absent in Kepler data. The SBCR radii are systematically higher than asteroseismic estimates by 5% for stars with masses below 1.0 M⊙.Conclusions. The SBCRs have proven to be a highly effective tool for estimating radii with a precision comparable to that obtained from asteroseismology, but at a significantly lower observational cost. Moreover, the superior concordance of Kepler-derived radii with SBCR measurements and the absence of the discrepancies observed in the K2-derived radii suggest the existence of underlying systematic errors that impact specific mass and metallicity regimes within the K2 dataset.
{"title":"Testing the asteroseismic estimates of stellar radii with surface brightness-colour relations and Gaia DR3 parallaxes","authors":"G. Valle, M. Dell’Omodarme, P. G. Prada Moroni, S. Degl’Innocenti","doi":"10.1051/0004-6361/202452861","DOIUrl":"https://doi.org/10.1051/0004-6361/202452861","url":null,"abstract":"<i>Context.<i/> A recent investigation highlighted peculiar trends between the radii derived from surface brightness-colour relations (SBCRs) combined with <i>Gaia<i/> DR3 parallaxes with respect to asteroseismic scaling relation radii from K2 data.<i>Aims.Kepler<i/> data differ from K2 data in many aspects. We investigated on the robustness of the results based on <i>Kepler<i/> data.<i>Methods.<i/> We cross-matched asteroseismic and astrometric data for over 12 000 red giant branch and red clump stars from the end-of-mission <i>Kepler<i/> catalogue with the <i>Gaia<i/> DR3 and TESS Input Catalogue v8.2 to obtain precise parallaxes, <i>V<i/>- and <i>K<i/>-band magnitudes, and <i>E<i/>(<i>B<i/> − <i>V<i/>) colour excesses. Two well-tested SBCRs from the literature were adopted to estimate stellar radii.<i>Results.<i/> The analysis confirmed that SBCR and asteroseismic radii agree very well. The overall differences are only 1–2% depending on the adopted SBCR. The dispersion of 7% was about two-thirds of what was found for K2-based data. As a difference from the K2-based investigation, the ratio of SBCRs-to-asteroseismic radii did not depend on the metallicity [Fe/H]. Moreover, the intriguing decreasing trend with [<i>α<i/>/Fe] of the radius ratio for massive stars that was observed in K2 data was absent in <i>Kepler<i/> data. The SBCR radii are systematically higher than asteroseismic estimates by 5% for stars with masses below 1.0 <i>M<i/><sub>⊙<sub/>.<i>Conclusions.<i/> The SBCRs have proven to be a highly effective tool for estimating radii with a precision comparable to that obtained from asteroseismology, but at a significantly lower observational cost. Moreover, the superior concordance of <i>Kepler<i/>-derived radii with SBCR measurements and the absence of the discrepancies observed in the K2-derived radii suggest the existence of underlying systematic errors that impact specific mass and metallicity regimes within the K2 dataset.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"4 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986205","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}
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