Pub Date : 2025-01-14DOI: 10.1051/0004-6361/202450709
Johanna Müller-Horn, Fabian Göttgens, Stefan Dreizler, Sebastian Kamann, Sven Martens, Sara Saracino, Claire S. Ye
Spectroscopic observations of binary stars in globular clusters are essential to shed light on the poorly constrained period, eccentricity, and mass ratio distributions and to develop an understanding of the formation of peculiar stellar objects. 47 Tuc (NGC 104) is one of the most massive Galactic globular clusters, with a large population of blue stragglers and with many predicted but as-yet elusive stellar-mass black holes. This makes it an exciting candidate for binary searches. We present a multi-epoch spectroscopic survey of 47 Tuc with the VLT/MUSE integral field spectrograph to determine radial velocity variations for 21 699 stars. We find a total binary fraction in the cluster of (2.4 ± 1.0)%, consistent with previous photometric estimates, and an increased binary fraction among blue straggler stars, approximately three times higher than the cluster average. We find very few binaries with periods below three days, and none with massive dark companions. A comparison with predictions from state-of-the-art models shows that the absence of such short-period binaries and of binaries with massive companions is surprising, highlighting the need to improve our understanding of stellar and dynamical evolution in binary systems.
{"title":"Binary properties of the globular cluster 47 Tuc (NGC 104)","authors":"Johanna Müller-Horn, Fabian Göttgens, Stefan Dreizler, Sebastian Kamann, Sven Martens, Sara Saracino, Claire S. Ye","doi":"10.1051/0004-6361/202450709","DOIUrl":"https://doi.org/10.1051/0004-6361/202450709","url":null,"abstract":"Spectroscopic observations of binary stars in globular clusters are essential to shed light on the poorly constrained period, eccentricity, and mass ratio distributions and to develop an understanding of the formation of peculiar stellar objects. 47 Tuc (NGC 104) is one of the most massive Galactic globular clusters, with a large population of blue stragglers and with many predicted but as-yet elusive stellar-mass black holes. This makes it an exciting candidate for binary searches. We present a multi-epoch spectroscopic survey of 47 Tuc with the VLT/MUSE integral field spectrograph to determine radial velocity variations for 21 699 stars. We find a total binary fraction in the cluster of (2.4 ± 1.0)%, consistent with previous photometric estimates, and an increased binary fraction among blue straggler stars, approximately three times higher than the cluster average. We find very few binaries with periods below three days, and none with massive dark companions. A comparison with predictions from state-of-the-art models shows that the absence of such short-period binaries and of binaries with massive companions is surprising, highlighting the need to improve our understanding of stellar and dynamical evolution in binary systems.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"1 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986202","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: 10.1051/0004-6361/202452115
M. Dehghanian, N. Arav, M. Sharma, D. Byun, G. Walker
Context. Quasar outflows are key players in the feedback processes that influence the evolution of galaxies and the intergalactic medium. The chemical abundance of these outflows provides crucial insights into their origin and impact.Aims. We determine the absolute abundances of nitrogen and sulfur and the physical conditions of the outflow seen in quasar 3C298.Methods. We analyzed archival spectral data from the Hubble Space Telescope for 3C298. We measured the ionic column densities from the absorption troughs and compared the results to photoionization predictions made with the Cloudy code for three different spectral energy distributions (SEDs), including MF87, UV-soft, and HE0238 SEDs. We also calculated the ionic column densities of the excited and ground states of N III to estimate the electron number density and location of the outflow using the Chianti atomic database.Results. The MF87, UV-soft, and HE0238 SEDs yield nitrogen and sulfur abundances at supersolar, solar, and subsolar values, respectively, with a spread of 0.4–3 times solar. Additionally, we determined an electron number density of log(ne)≥3.3 cm−3, and the outflow might extend up to a maximum distance of 2.8 kpc.Conclusions. Our results indicate a solar metallicity within an uncertainty range of 60% that is driven by variations in the chosen SED and photoionization models. This study underscores the importance of the SED impact on determining chemical abundances in quasar outflows. These findings highlight the necessity of considering a wider range of possible abundances that span from subsolar to supersolar values.
{"title":"Determining the absolute chemical abundance of nitrogen and sulfur in the quasar outflow of 3C298","authors":"M. Dehghanian, N. Arav, M. Sharma, D. Byun, G. Walker","doi":"10.1051/0004-6361/202452115","DOIUrl":"https://doi.org/10.1051/0004-6361/202452115","url":null,"abstract":"<i>Context.<i/> Quasar outflows are key players in the feedback processes that influence the evolution of galaxies and the intergalactic medium. The chemical abundance of these outflows provides crucial insights into their origin and impact.<i>Aims.<i/> We determine the absolute abundances of nitrogen and sulfur and the physical conditions of the outflow seen in quasar 3C298.<i>Methods.<i/> We analyzed archival spectral data from the Hubble Space Telescope for 3C298. We measured the ionic column densities from the absorption troughs and compared the results to photoionization predictions made with the Cloudy code for three different spectral energy distributions (SEDs), including MF87, UV-soft, and HE0238 SEDs. We also calculated the ionic column densities of the excited and ground states of N III to estimate the electron number density and location of the outflow using the Chianti atomic database.<i>Results.<i/> The MF87, UV-soft, and HE0238 SEDs yield nitrogen and sulfur abundances at supersolar, solar, and subsolar values, respectively, with a spread of 0.4–3 times solar. Additionally, we determined an electron number density of log(<i>n<i/><sub>e<sub/>)≥3.3 cm<sup>−3<sup/>, and the outflow might extend up to a maximum distance of 2.8 kpc.<i>Conclusions.<i/> Our results indicate a solar metallicity within an uncertainty range of 60% that is driven by variations in the chosen SED and photoionization models. This study underscores the importance of the SED impact on determining chemical abundances in quasar outflows. These findings highlight the necessity of considering a wider range of possible abundances that span from subsolar to supersolar values.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"93 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986136","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: 10.1051/0004-6361/202452178
Manami Sasaki, Federico Zangrandi, Miroslav Filipović, Rami Z. E. Alsaberi, Jordan D. Collier, Frank Haberl, Ian Heywood, Patrick Kavanagh, Bärbel Koribalski, Roland Kothes, Sanja Lazarević, Pierre Maggi, Chandreyee Maitra, Sean Points, Zachary J. Smeaton, Velibor Velović
When a star dies, it can explode in a supernova, causing a strong shock wave and forming an interstellar object called a supernova remnant (SNR). Observational studies of SNRs allow us to learn about the different types of progenitors, the explosion mechanisms, the physics of interstellar shocks, and the matter cycle in galaxies. We report on the first detection of SNRs located on the outskirts of a galaxy; namely, the Large Magellanic Cloud (LMC), the largest satellite galaxy of our Galaxy. The sources were discovered ∼3° outside the main stellar and gas distribution of the LMC in the recent surveys in radio with the Australian Square Kilometre Array Pathfinder (ASKAP) and in X-rays with the extended Roentgen Survey with an Imaging Telescope Array (eROSITA). We studied them in follow-up observations with the X-ray Multi-Mirror Mission-Newton telescope and MeerKAT and confirmed them to be SNRs. Their progenitors are most likely stars that had left the LMC due to tidal interaction between the Magellanic Clouds and the Milky Way. SNR J0614-7251 is located in an environment with a similar density to those of the other known SNRs in the LMC, and has similar X-ray properties. SNR J0624-6948, on the other hand, is located in a region with a lower density, n0 < 0.01 cm−3. Its radio shell shows a spectral index and polarisation typical of an SNR.
{"title":"Supernova remnants on the outskirts of the Large Magellanic Cloud","authors":"Manami Sasaki, Federico Zangrandi, Miroslav Filipović, Rami Z. E. Alsaberi, Jordan D. Collier, Frank Haberl, Ian Heywood, Patrick Kavanagh, Bärbel Koribalski, Roland Kothes, Sanja Lazarević, Pierre Maggi, Chandreyee Maitra, Sean Points, Zachary J. Smeaton, Velibor Velović","doi":"10.1051/0004-6361/202452178","DOIUrl":"https://doi.org/10.1051/0004-6361/202452178","url":null,"abstract":"When a star dies, it can explode in a supernova, causing a strong shock wave and forming an interstellar object called a supernova remnant (SNR). Observational studies of SNRs allow us to learn about the different types of progenitors, the explosion mechanisms, the physics of interstellar shocks, and the matter cycle in galaxies. We report on the first detection of SNRs located on the outskirts of a galaxy; namely, the Large Magellanic Cloud (LMC), the largest satellite galaxy of our Galaxy. The sources were discovered ∼3° outside the main stellar and gas distribution of the LMC in the recent surveys in radio with the Australian Square Kilometre Array Pathfinder (ASKAP) and in X-rays with the extended Roentgen Survey with an Imaging Telescope Array (eROSITA). We studied them in follow-up observations with the X-ray Multi-Mirror Mission-<i>Newton<i/> telescope and MeerKAT and confirmed them to be SNRs. Their progenitors are most likely stars that had left the LMC due to tidal interaction between the Magellanic Clouds and the Milky Way. SNR J0614-7251 is located in an environment with a similar density to those of the other known SNRs in the LMC, and has similar X-ray properties. SNR J0624-6948, on the other hand, is located in a region with a lower density, <i>n<i/><sub>0<sub/> < 0.01 cm<sup>−3<sup/>. Its radio shell shows a spectral index and polarisation typical of an SNR.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"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":"142986197","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: 10.1051/0004-6361/202452868
C. M. Cordun, H. K. Vedantham, M. A. Brentjens, F. F. S. van der Tak
Context. Detection of electron cyclotron maser (ECM) emission from exoplanets in the 10–40 MHz radio band is likely the only way to measure an exoplanet’s magnetic field directly. However, no definitive detection of exoplanetary ECM emission has been made to date. A detection of the hot Jupiter Tau Boötis b was reported but with an observing mode that is not immune to confusion from off-axis interference, making the detection tentative.Aims. We searched for radio emissions from Tau Boötis b using the Low Frequency Array (LOFAR) in interferometric mode, which employs direction-of-arrival information to discriminate genuine signals from interference. Our aim was to confirm the previous tentative detection or establish an upper limit in the case of a non-detection.Methods. We conducted observations using LOFAR’s Low Band Antenna in interferometric mode, which totalled 64 hours spread over 8 nights. We created a custom data-processing pipeline to mitigate common challenges in decametric radio astronomy, including radio frequency interference, ionospheric distortions, and sidelobe noise from nearby bright radio sources. We used this pipeline to image the field around Tau Boötis b, searching for both quiescent and bursting emission from the direction of Tau Boötis b.Results. Despite the high sensitivity of the interferometric observations and extensive data processing, no significant emission was detected from Tau Boötis b in Stokes V. We establish an upper limit of 2 sigma at 24 mJy for any continuous emission from the exoplanet. The previous tentative detection of 400 mJy is thus not confirmed by the interferometric observations.Conclusions. The previous tentative detection is unlikely to be a bona fide astrophysical signal. Our upper limit is lower than the flux density predicted by scaling laws, meaning either the scaling laws need to be revised or the emission from this particular system is beamed away from Earth.
{"title":"Deep radio interferometric search for decametre radio emission from the exoplanet Tau Boötis b","authors":"C. M. Cordun, H. K. Vedantham, M. A. Brentjens, F. F. S. van der Tak","doi":"10.1051/0004-6361/202452868","DOIUrl":"https://doi.org/10.1051/0004-6361/202452868","url":null,"abstract":"<i>Context<i/>. Detection of electron cyclotron maser (ECM) emission from exoplanets in the 10–40 MHz radio band is likely the only way to measure an exoplanet’s magnetic field directly. However, no definitive detection of exoplanetary ECM emission has been made to date. A detection of the hot Jupiter Tau Boötis b was reported but with an observing mode that is not immune to confusion from off-axis interference, making the detection tentative.<i>Aims<i/>. We searched for radio emissions from Tau Boötis b using the Low Frequency Array (LOFAR) in interferometric mode, which employs direction-of-arrival information to discriminate genuine signals from interference. Our aim was to confirm the previous tentative detection or establish an upper limit in the case of a non-detection.<i>Methods<i/>. We conducted observations using LOFAR’s Low Band Antenna in interferometric mode, which totalled 64 hours spread over 8 nights. We created a custom data-processing pipeline to mitigate common challenges in decametric radio astronomy, including radio frequency interference, ionospheric distortions, and sidelobe noise from nearby bright radio sources. We used this pipeline to image the field around Tau Boötis b, searching for both quiescent and bursting emission from the direction of Tau Boötis b.<i>Results<i/>. Despite the high sensitivity of the interferometric observations and extensive data processing, no significant emission was detected from Tau Boötis b in Stokes V. We establish an upper limit of 2 sigma at 24 mJy for any continuous emission from the exoplanet. The previous tentative detection of 400 mJy is thus not confirmed by the interferometric observations.<i>Conclusions<i/>. The previous tentative detection is unlikely to be a bona fide astrophysical signal. Our upper limit is lower than the flux density predicted by scaling laws, meaning either the scaling laws need to be revised or the emission from this particular system is beamed away from Earth.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"49 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142986201","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 : 2025-01-13DOI: 10.1051/0004-6361/202451372
Zubair I. Shaikh, Georgios Nicolaou, Anil N. Raghav, Kalpesh Ghag, Omkar Dhamane
Interplanetary coronal mass ejections (ICMEs) are large-scale, coherent magnetic structures that play a pivotal role in heliospheric dynamics and space weather phenomena. Although thermodynamic analyses of ICME magnetic obstacles (MOs) at 1 au generally reveal adiabatic characteristics, the broader thermodynamic processes and associated plasma heating and cooling mechanisms remain insufficiently understood. In this study we analysed 473 ICME MOs observed at 1 au by the ACE spacecraft, utilising polytropic analysis to determine the polytropic index, α, for these structures. We identified 25 ICME MOs in which plasma protons exhibit a polytropic index α ≳ 2.00, with a mean value of 2.14 ± 0.07, indicating super-adiabatic behaviour. We also observed evidence of 12 isothermal (α ∼ 1) and 45 adiabatic (α ∼ 5/3) ICME MOs. Furthermore, in the case of super-adiabatic ICME MOs, we observe that all the total supplied heat is efficiently utilised to accomplish work in the surrounding environment, assuming the protons have three effective kinetic degrees of freedom. Therefore, as they expand, these ICMEs MOs cool faster than the adiabatic plasma. Our findings are critical to comprehending the dynamic evolution of ICMEs in interplanetary space and the energy-exchange mechanisms involved.
{"title":"Revealing super-adiabatic features of interplanetary coronal mass ejections at 1 au","authors":"Zubair I. Shaikh, Georgios Nicolaou, Anil N. Raghav, Kalpesh Ghag, Omkar Dhamane","doi":"10.1051/0004-6361/202451372","DOIUrl":"https://doi.org/10.1051/0004-6361/202451372","url":null,"abstract":"Interplanetary coronal mass ejections (ICMEs) are large-scale, coherent magnetic structures that play a pivotal role in heliospheric dynamics and space weather phenomena. Although thermodynamic analyses of ICME magnetic obstacles (MOs) at 1 au generally reveal adiabatic characteristics, the broader thermodynamic processes and associated plasma heating and cooling mechanisms remain insufficiently understood. In this study we analysed 473 ICME MOs observed at 1 au by the ACE spacecraft, utilising polytropic analysis to determine the polytropic index, <i>α<i/>, for these structures. We identified 25 ICME MOs in which plasma protons exhibit a polytropic index <i>α<i/> ≳ 2.00, with a mean value of 2.14 ± 0.07, indicating super-adiabatic behaviour. We also observed evidence of 12 isothermal (<i>α<i/> ∼ 1) and 45 adiabatic (<i>α<i/> ∼ 5/3) ICME MOs. Furthermore, in the case of super-adiabatic ICME MOs, we observe that all the total supplied heat is efficiently utilised to accomplish work in the surrounding environment, assuming the protons have three effective kinetic degrees of freedom. Therefore, as they expand, these ICMEs MOs cool faster than the adiabatic plasma. Our findings are critical to comprehending the dynamic evolution of ICMEs in interplanetary space and the energy-exchange mechanisms involved.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"27 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142967943","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 : 2025-01-13DOI: 10.1051/0004-6361/202453419
C. Cabezas, M. Agúndez, N. Marcelino, C. H. Chang, R. Fuentetaja, B. Tercero, M. Nakajima, Y. Endo, P. de Vicente, J. Cernicharo
We report the first detection in interstellar medium of the 1-cyano propargyl radical, HC3HCN. This species is an isomer of the 3-cyano propargyl radical (CH2C3N), which was recently discovered in TMC-1. The 1-cyano propargyl radical was observed in the cold dark cloud TMC-1 using data from the ongoing QUIJOTE line survey, which is being carried out with the Yebes 40m telescope. A total of seven rotational transitions with multiple hyperfine components were detected in the 31.0–50.4 GHz range. We derived a column density of (2.2 ± 0.2) × 1011 cm−2 and a rotational temperature of 7±1 K. The abundance ratio between HC3HCN and CH2C3N is 1.4. The almost equal abundance of these isomers indicates that the two species may be produced in the same reaction with a similar efficiency, probably in the reaction C + CH2CHCN and perhaps also in the reaction C2 + CH3CN and the dissociative recombination with electrons of CH2C3NH+.
{"title":"Identification of the interstellar 1-cyano propargyl radical (HCCCHCN) in TMC-1","authors":"C. Cabezas, M. Agúndez, N. Marcelino, C. H. Chang, R. Fuentetaja, B. Tercero, M. Nakajima, Y. Endo, P. de Vicente, J. Cernicharo","doi":"10.1051/0004-6361/202453419","DOIUrl":"https://doi.org/10.1051/0004-6361/202453419","url":null,"abstract":"We report the first detection in interstellar medium of the 1-cyano propargyl radical, HC<sub>3<sub/>HCN. This species is an isomer of the 3-cyano propargyl radical (CH<sub>2<sub/>C<sub>3<sub/>N), which was recently discovered in TMC-1. The 1-cyano propargyl radical was observed in the cold dark cloud TMC-1 using data from the ongoing QUIJOTE line survey, which is being carried out with the Yebes 40m telescope. A total of seven rotational transitions with multiple hyperfine components were detected in the 31.0–50.4 GHz range. We derived a column density of (2.2 ± 0.2) × 10<sup>11<sup/> cm<sup>−2<sup/> and a rotational temperature of 7±1 K. The abundance ratio between HC<sub>3<sub/>HCN and CH<sub>2<sub/>C<sub>3<sub/>N is 1.4. The almost equal abundance of these isomers indicates that the two species may be produced in the same reaction with a similar efficiency, probably in the reaction C + CH<sub>2<sub/>CHCN and perhaps also in the reaction C<sub>2<sub/> + CH<sub>3<sub/>CN and the dissociative recombination with electrons of CH<sub>2<sub/>C<sub>3<sub/>NH<sup>+<sup/>.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"29 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142967941","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 : 2025-01-10DOI: 10.1051/0004-6361/202452109
Y. Xin, Yu. Skorov, Y. Zhao, L. Rezac, P. Hartogh, M. Küppers
Aims. This study investigates the impact of microscopic and macroscopic cometary surface properties on water production variations with heliocentric distance, focusing on dust layer thickness, grain size, nucleus shape, and spin axis orientation.Methods. We employed a two-layer thermophysical model to calculate effective gas production, incorporating a dust layer of porous aggregates of submillimeter- and millimeter-sized grains. The model includes radiative thermal conductivity and permeability for volatile diffusion and considers dust layer evolution and tensile strength. We examined different cometary nucleus shape models based on spacecraft observations and calculated power-law exponents for water production rates as functions of heliocentric distance.Results. A two-layer outgassing model with fixed layer properties showed minimal qualitative differences from a simpler water ice sublimation model. The study reaffirms the critical role of the spin axis inclination and illuminated cross-section variation with the heliocentric distance in gas production. Using 67P/Churyumov-Gerasimenko’s orbital parameters, the study demonstrates that dust accumulation and layer growth significantly alter production rate exponents. Additionally, considering tensile strength in a homogeneous spherical nucleus model revealed the potential for local dust crust removal near perihelion.Conclusions. Macroscopic properties such as nucleus shape and spin axis orientation significantly influence water production rate variations with heliocentric distance. Microscopic surface characteristics and dust layer growth also play crucial roles in cometary activity. Incorporating tensile strength and dust removal mechanisms into models provides a more accurate representation of comet activity, particularly near perihelion. This refined model enhances our understanding of comet outgassing, highlighting the importance of detailed surface property data for an accurate interpretation of observations.
{"title":"Modeling of comet water production","authors":"Y. Xin, Yu. Skorov, Y. Zhao, L. Rezac, P. Hartogh, M. Küppers","doi":"10.1051/0004-6361/202452109","DOIUrl":"https://doi.org/10.1051/0004-6361/202452109","url":null,"abstract":"<i>Aims<i/>. This study investigates the impact of microscopic and macroscopic cometary surface properties on water production variations with heliocentric distance, focusing on dust layer thickness, grain size, nucleus shape, and spin axis orientation.<i>Methods<i/>. We employed a two-layer thermophysical model to calculate effective gas production, incorporating a dust layer of porous aggregates of submillimeter- and millimeter-sized grains. The model includes radiative thermal conductivity and permeability for volatile diffusion and considers dust layer evolution and tensile strength. We examined different cometary nucleus shape models based on spacecraft observations and calculated power-law exponents for water production rates as functions of heliocentric distance.<i>Results<i/>. A two-layer outgassing model with fixed layer properties showed minimal qualitative differences from a simpler water ice sublimation model. The study reaffirms the critical role of the spin axis inclination and illuminated cross-section variation with the heliocentric distance in gas production. Using 67P/Churyumov-Gerasimenko’s orbital parameters, the study demonstrates that dust accumulation and layer growth significantly alter production rate exponents. Additionally, considering tensile strength in a homogeneous spherical nucleus model revealed the potential for local dust crust removal near perihelion.<i>Conclusions<i/>. Macroscopic properties such as nucleus shape and spin axis orientation significantly influence water production rate variations with heliocentric distance. Microscopic surface characteristics and dust layer growth also play crucial roles in cometary activity. Incorporating tensile strength and dust removal mechanisms into models provides a more accurate representation of comet activity, particularly near perihelion. This refined model enhances our understanding of comet outgassing, highlighting the importance of detailed surface property data for an accurate interpretation of observations.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"89 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142967959","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}
Low mass-ratio contact binary systems are a fascinating class of eclipsing binaries; they are widely regarded as the potential progenitors of stellar mergers. For this study we analyzed 40 newly discovered low mass-ratio totally eclipsing contact binary systems identified from the Catalina Sky Survey data. The relative parameters for these systems were inferred using a neural network model combined with a Bayesian inference-based Hamiltonian Monte Carlo (HMC) algorithm, with uncertainties estimated from the posterior distributions generated by the HMC algorithm. The absolute parameters were then calculated using these relative parameters, along with distances and temperatures provided by Gaia Data Release 3. Among the 40 systems, 24 are deep low mass-ratio overcontact binaries, characterized by fill-out factors of 0.5 or higher and mass ratios of 0.25 or lower. Notably, two systems, CSS_J071952.5+243224 and CSS_J155519.0+135855, have mass ratios below 0.1, specifically 0.094 ± 0.006 and 0.086 ± 0.004, respectively. Furthermore, we compared the parameters obtained in this study with those from 39 low mass-ratio contact binary systems identified in previous research, finding that the estimated parameters are largely consistent. Finally, to evaluate the evolutionary status of the 40 systems, we calculated the ratio of spin angular momentum to orbital angular momentum for each and found that all are currently in a relatively stable evolutionary phase.
{"title":"Photometric analysis of 40 low mass-ratio contact binary systems in the Catalina Sky Survey","authors":"JinLiang Wang, Xu Ding, Wei Liu, LiHuan Yu, Chong Xu, KaiFan Ji","doi":"10.1051/0004-6361/202451987","DOIUrl":"https://doi.org/10.1051/0004-6361/202451987","url":null,"abstract":"Low mass-ratio contact binary systems are a fascinating class of eclipsing binaries; they are widely regarded as the potential progenitors of stellar mergers. For this study we analyzed 40 newly discovered low mass-ratio totally eclipsing contact binary systems identified from the Catalina Sky Survey data. The relative parameters for these systems were inferred using a neural network model combined with a Bayesian inference-based Hamiltonian Monte Carlo (HMC) algorithm, with uncertainties estimated from the posterior distributions generated by the HMC algorithm. The absolute parameters were then calculated using these relative parameters, along with distances and temperatures provided by Gaia Data Release 3. Among the 40 systems, 24 are deep low mass-ratio overcontact binaries, characterized by fill-out factors of 0.5 or higher and mass ratios of 0.25 or lower. Notably, two systems, CSS_J071952.5+243224 and CSS_J155519.0+135855, have mass ratios below 0.1, specifically 0.094 ± 0.006 and 0.086 ± 0.004, respectively. Furthermore, we compared the parameters obtained in this study with those from 39 low mass-ratio contact binary systems identified in previous research, finding that the estimated parameters are largely consistent. Finally, to evaluate the evolutionary status of the 40 systems, we calculated the ratio of spin angular momentum to orbital angular momentum for each and found that all are currently in a relatively stable evolutionary phase.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142967960","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 : 2025-01-10DOI: 10.1051/0004-6361/202453100
Camila Aros-Bunster, Matthias R. Schreiber, Odette Toloza, Mercedes S. Hernandez, Diogo Belloni, Kareem El-Badry, Zach Vanderbosch, Felipe Lagos-Vilches, Boris T. Gänsicke, Detlev Koester
The white dwarf (WD) binary SDSS J1257+5428 comprises an extremely low-mass WD with a mass of 0.1–0.24 M⊙ and a more massive companion of ∼1 M⊙ that is more than 0.6 Gyr younger. The origin of this system has been termed paradoxical because current theories for the formation of WD binaries are unable to explain its existence. Any additional observational constraint on the formation of SDSS J1257+5428 might provide important insights into double WD formation in general. We present the discovery of a tertiary WD, which makes SDSS J1257+5428 the third known triple WD. We used KECK/LRIS spectroscopy, Gaia and SDSS photometry, and WD atmosphere models to characterize the distant tertiary (projected separation ∼8000 au). We find the tertiary WD to be cool (6200 − 6400 K) and massive (log(g) = 8.88 − 8.97), which translates to a cooling age of ≳4 Gyr. This cooling age represents a lower limit on the total age of the triple system. While at first glance it seems likely that the inner binary formed through a stable mass transfer phase followed by common envelope evolution, reproducing the stellar mass and period required for the progenitor of the ∼1 M⊙ WD in the inner binary through stable mass transfer seems impossible. We therefore speculate that the system might be the descendant of a cataclysmic variable with an evolved donor.
{"title":"The third known triple white dwarf: The close double white dwarf SDSS J125733.63+542850.5 hosts a white dwarf tertiary","authors":"Camila Aros-Bunster, Matthias R. Schreiber, Odette Toloza, Mercedes S. Hernandez, Diogo Belloni, Kareem El-Badry, Zach Vanderbosch, Felipe Lagos-Vilches, Boris T. Gänsicke, Detlev Koester","doi":"10.1051/0004-6361/202453100","DOIUrl":"https://doi.org/10.1051/0004-6361/202453100","url":null,"abstract":"The white dwarf (WD) binary SDSS J1257+5428 comprises an extremely low-mass WD with a mass of 0.1–0.24 M<sub>⊙<sub/> and a more massive companion of ∼1 M<sub>⊙<sub/> that is more than 0.6 Gyr younger. The origin of this system has been termed paradoxical because current theories for the formation of WD binaries are unable to explain its existence. Any additional observational constraint on the formation of SDSS J1257+5428 might provide important insights into double WD formation in general. We present the discovery of a tertiary WD, which makes SDSS J1257+5428 the third known triple WD. We used KECK/LRIS spectroscopy, <i>Gaia<i/> and SDSS photometry, and WD atmosphere models to characterize the distant tertiary (projected separation ∼8000 au). We find the tertiary WD to be cool (6200 − 6400 K) and massive (log(<i>g<i/>) = 8.88 − 8.97), which translates to a cooling age of ≳4 Gyr. This cooling age represents a lower limit on the total age of the triple system. While at first glance it seems likely that the inner binary formed through a stable mass transfer phase followed by common envelope evolution, reproducing the stellar mass and period required for the progenitor of the ∼1 M<sub>⊙<sub/> WD in the inner binary through stable mass transfer seems impossible. We therefore speculate that the system might be the descendant of a cataclysmic variable with an evolved donor.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"9 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142967942","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 : 2025-01-10DOI: 10.1051/0004-6361/202451243
Qingshun Hu, Songmei Qin, Yangping Luo, Yuting Li
Context. The study of open cluster morphology is pivotal for exploring their formation and evolutionary processes.Aims. We manage to assess the morphological stability of 105 nearby open clusters within tidal radii on the X-Y, X-Z, and Y-Z planes of the heliocentric Cartesian coordinate system, utilizing member catalogs from the literature. Meanwhile, we also delve into factors potentially impacting the clusters’ morphological stability on these projection planes.Methods. We used the rose diagram method by constructing the 3D projected morphology of sample clusters to quantify the morphological stability of their 3D projected morphology.Results. Our analysis indicates there is a demonstrated linear positive correlation between the number of sample clusters’ member stars within tidal radii and their morphological stability in different 3D projection planes. This may suggest that the more member stars there are within the tidal radius of a cluster, the stronger its own gravitational binding capacity is, resulting in strong morphological stability. We find a direct link between the clusters’ morphological stabilities in the X-Z plane within tidal radii and their velocity dispersion in the same plane, suggesting that the morphological stabilities in the X-Z plane may be dependent on internal dynamics. Moreover, the morphological stability of the clusters’ 3D projection is influenced by their spatial positions along the Y axis, but not linearly, indicating that the environmental changes at the clusters’ location may affect their morphological stability. Likewise, specific external forces can have an effect on their morphological stability.Conclusions. This research introduces a novel perspective for understanding the morphological stability of open clusters, with a particular focus on their 3D projected morphologies.
{"title":"3D projection analysis: Characterizing the morphological stability of nearby open clusters","authors":"Qingshun Hu, Songmei Qin, Yangping Luo, Yuting Li","doi":"10.1051/0004-6361/202451243","DOIUrl":"https://doi.org/10.1051/0004-6361/202451243","url":null,"abstract":"<i>Context<i/>. The study of open cluster morphology is pivotal for exploring their formation and evolutionary processes.<i>Aims<i/>. We manage to assess the morphological stability of 105 nearby open clusters within tidal radii on the X-Y, X-Z, and Y-Z planes of the heliocentric Cartesian coordinate system, utilizing member catalogs from the literature. Meanwhile, we also delve into factors potentially impacting the clusters’ morphological stability on these projection planes.<i>Methods<i/>. We used the rose diagram method by constructing the 3D projected morphology of sample clusters to quantify the morphological stability of their 3D projected morphology.<i>Results<i/>. Our analysis indicates there is a demonstrated linear positive correlation between the number of sample clusters’ member stars within tidal radii and their morphological stability in different 3D projection planes. This may suggest that the more member stars there are within the tidal radius of a cluster, the stronger its own gravitational binding capacity is, resulting in strong morphological stability. We find a direct link between the clusters’ morphological stabilities in the X-Z plane within tidal radii and their velocity dispersion in the same plane, suggesting that the morphological stabilities in the X-Z plane may be dependent on internal dynamics. Moreover, the morphological stability of the clusters’ 3D projection is influenced by their spatial positions along the <i>Y<i/> axis, but not linearly, indicating that the environmental changes at the clusters’ location may affect their morphological stability. Likewise, specific external forces can have an effect on their morphological stability.<i>Conclusions<i/>. This research introduces a novel perspective for understanding the morphological stability of open clusters, with a particular focus on their 3D projected morphologies.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"6 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142968001","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：