Monthly Notices of the Royal Astronomical Society最新文献

On the sausage magnetohydrodynamic waves in magnetic flux tubes: finite plasma beta and phase mixing 磁通管中的香肠磁流体动力波：有限等离子体贝塔和相混合

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-19 DOI: 10.1093/mnras/stae2173

Zanyar Ebrahimi

{"title":"On the sausage magnetohydrodynamic waves in magnetic flux tubes: finite plasma beta and phase mixing","authors":"Zanyar Ebrahimi","doi":"10.1093/mnras/stae2173","DOIUrl":"https://doi.org/10.1093/mnras/stae2173","url":null,"abstract":"Over the past twenty years, there has been increasing evidence of the existence of sausage waves in the solar atmosphere. These observations make them useful tools in the context of atmospheric seismology. Here, we study sausage magnetohydrodynamic waves in a magnetic flux tube of non-zero plasma beta with a circular cross-section and a radially inhomogeneous plasma density. Solving numerically the equations of motion for an initial value problem, the spatio-temporal evolution of the velocity perturbations is obtained for different sets of parameters. We show that the ratio of the amplitudes of the longitudinal and radial perturbations is determined by the amount of plasma beta. Additionally, the longitudinal component of the velocity perturbation experiences phase-mixing within a layer surrounding the boundary of the flux tube with a rate depending on the amount of plasma beta. The results revealed that in the presence of a non-zero plasma beta, the flux tube exhibits oscillations in both the radial and longitudinal directions, characterized by a combination of two frequencies: one belonging to the slow continuum and the other to the Alfvén continuum. Also, the period of radial oscillation is obtained for different sets of parameters. The dependence of the period of the radial oscillation on the wavenumber confirms the results obtained in previous studies.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

引用次数: 0

CXOU J005245.0-722844: Discovery of a be star / white dwarf binary system in the SMC via a very fast, super-eddington X-ray outburst event CXOU J005245.0-722844：通过快速、超边顿X射线爆发事件发现SMC中的比星/白矮星双星系统

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-19 DOI: 10.1093/mnras/stae2176

T M Gaudin, M J Coe, J A Kennea, I M Monageng, D A H Buckley, A Udalski, P A Evans

{"title":"CXOU J005245.0-722844: Discovery of a be star / white dwarf binary system in the SMC via a very fast, super-eddington X-ray outburst event","authors":"T M Gaudin, M J Coe, J A Kennea, I M Monageng, D A H Buckley, A Udalski, P A Evans","doi":"10.1093/mnras/stae2176","DOIUrl":"https://doi.org/10.1093/mnras/stae2176","url":null,"abstract":"CXOU J005245.0-722844 is an X-ray source in the Small Magellanic Cloud (SMC) that has long been known as a Be/X-ray binary (BeXRB) star, containing an OBe main sequence star and a compact object. In this paper, we report on a new very fast X-ray outburst from CXOU J005245.0-722844. X-ray observations taken by Swift constrain the duration of the outburst to less than 16 days and find that the source reached super-Eddington X-ray luminosities during the initial phases of the eruption. The XRT spectrum of CXOU J005245.0-722844 during this outburst reveals a super-soft X-ray source, best fit by an absorbed thermal blackbody model. Optical and Ultraviolet follow-up observations from the Optical Gravitational Lensing Experiment (OGLE), Asteroid Terrestrial-impact Last Alert System (ATLAS), and Swift identify a brief ∼0.5 magnitude optical burst coincident with the X-ray outburst that lasted for less than 7 days. Optical photometry additionally identifies the orbital period of the system to be 17.55 days and identifies a shortening of the period to 17.14 days in the years leading up to the outburst. Optical spectroscopy from the Southern African Large Telescope (SALT) confirms that the optical companion is an early-type OBe star. We conclude from our observations that the compact object in this system is a white dwarf (WD), making this the seventh candidate Be/WD X-ray binary. The X-ray outburst is found to be the result of a very-fast, ultra-luminous nova similar to the outburst of MAXI J0158-744.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256355","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

引用次数: 0

Kinematic study of the orion complex: Analysing the young stellar clusters from big and small structures 猎户座复合体的运动学研究：从大小结构分析年轻恒星簇群

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-19 DOI: 10.1093/mnras/stae2157

Sergio Sánchez-Sanjuán, Jesús Hernández, Ángeles Pérez-Villegas, Carlos Román-Zúñiga, Luis Aguilar, Javier Ballesteros-Paredes, Andrea Bonilla-Barroso

{"title":"Kinematic study of the orion complex: Analysing the young stellar clusters from big and small structures","authors":"Sergio Sánchez-Sanjuán, Jesús Hernández, Ángeles Pérez-Villegas, Carlos Román-Zúñiga, Luis Aguilar, Javier Ballesteros-Paredes, Andrea Bonilla-Barroso","doi":"10.1093/mnras/stae2157","DOIUrl":"https://doi.org/10.1093/mnras/stae2157","url":null,"abstract":"In this work, we analysed young stellar clusters with spatial and kinematic coherence in the Orion star-forming complex. For this study, we selected a sample of pre-main sequence candidates using parallaxes, proper motions and positions on the colour-magnitude diagram. After applying a hierarchical clustering algorithm in the 5D parameter space provided by Gaia DR3, we divided the recovered clusters into two regimes: Big Structures and Small Structures, defined by the number of detected stars per cluster. In the first regime, we found 13 stellar groups distributed along the declination axis in the regions where there is a high density of stars. In the second regime, we recovered 34 clusters classified into two types: 14 as small groups completely independent from the larger structures, including four candidates of new clusters, and 12 classified as sub-structures embedded within five larger clusters. Additionally, radial velocity data from APOGEE-2 and GALAH DR3 was included to study the phase space in some regions of the Orion complex. From the Big Structure regime, we found evidence of a general expansion in the Orion OB1 association over a common centre, giving a clue about the dynamical effects the region is undergoing. Likewise, in the Small Structure regime, the projected kinematics shows the ballistic expansion in the λ Orionis association and the detection of likely events of clusters’ close encounters in the OB1 association.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

引用次数: 0

Effects of nucleon-nucleon short-range correlation and symmetry energy on the evolution of newly born magnetars 核子-核子短程相关性和对称能对新生磁星演化的影响

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-19 DOI: 10.1093/mnras/stae2170

C X Liu, T F Feng, J M Dong

{"title":"Effects of nucleon-nucleon short-range correlation and symmetry energy on the evolution of newly born magnetars","authors":"C X Liu, T F Feng, J M Dong","doi":"10.1093/mnras/stae2170","DOIUrl":"https://doi.org/10.1093/mnras/stae2170","url":null,"abstract":"Millisecond magnetars are widely suggested as the central engines powering hydrogen-poor superluminous supernovae (SLSNe). These magnetars primarily lose huge rotational energy through gravitational wave radiation (GWR) and magnetic dipole radiation (MDR), with MDR serving as an energy source for SLSNe. We study the evolution of the magnetar spin, magnetic inclination angle, and the resulting thermal radiative luminosity of the SLSNe, where the impacts of the nucleon-nucleon short-range correlation, the mass and initial spin of the magnetar, and the density-dependent symmetry energy of the dense nuclear matter on the evolution are discussed. The relativistic mean-field theory is employed to calculate the nuclear matter properties, and we particularly concentrate on the time- and space-dependent bulk viscosity which is crucial for the magnetic inclination angle evolution. It is found that the nucleon-nucleon short-range correlation weakens the damping of bulk viscosity of dense matter and therefore inhibits the growth of magnetic inclination angle, and it reduces the MDR (GWR) peak luminosity of a canonical magnetar by several times while it raises the peak thermal radiation luminosity of SLSNe by several times. For magnetars with nonrotating mass obviously lower than the $1.4 , rm M_odot$ with slow initial rotation, the magnetic inclination angle is more likely to evolve towards 0 degrees quickly, and these magnetars are not suitable as the central engine for SLSNe. Within the ‘family’ of FSUGarnet interaction, a stiffer symmetry energy gives a lower threshold of direct Urca process and hence gives a much larger bulk viscosity coefficient, and thus it promotes the growth of the magnetic inclination angle and the GWR for canonical stars but reduces the peak brightness of SLSNe significantly.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

引用次数: 0

The imprint of the first stars on the faint end of the white dwarf luminosity function 第一批恒星在白矮星光度函数暗端留下的印记

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-19 DOI: 10.1093/mnras/stae2172

Bartosz Dzięcioł, Tilman Hartwig, Naoki Yoshida

{"title":"The imprint of the first stars on the faint end of the white dwarf luminosity function","authors":"Bartosz Dzięcioł, Tilman Hartwig, Naoki Yoshida","doi":"10.1093/mnras/stae2172","DOIUrl":"https://doi.org/10.1093/mnras/stae2172","url":null,"abstract":"Population III stars are characterized by extremely low metallicities as they are thought to be formed from a pristine gas in the early Universe. Although the existence of Population III stars is widely accepted, the lack of direct observational evidence hampers the study of the nature of the putative stars. In this article, we explore the possibilities of constraining the nature of the oldest stars by using the luminosity function of their remnants – white dwarfs. We study the formation and evolution of white dwarf populations by following star formation in a Milky Way-like galaxy using the semi-analytic model a-sloth. We derive the white dwarf luminosity function by applying a linear Initial-Final Mass Relation and Mestel’s cooling model. The obtained luminosity function is generally in agreement with available observations and theoretical predictions – with an exponential increase to a maximum of Mabs = 16 and a sudden drop for Mabs &gt; 16. We explore the uncertainties of our model and compare them to the observational estimates. We adopt two different models of the initial mass function of Population III stars to show that the faint end of the luminosity function imprints the signature of Population III remnants. If the feature is detected in future observations, it would provide a clue to Population III stars and would also be an indirect evidence of low- to intermediate-mass Population III stars. We discuss the challenges and prospects for detecting the signatures.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

引用次数: 0

Short-lived gravitational instability in isolated irradiated discs 孤立辐照圆盘中的短暂引力不稳定性

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-19 DOI: 10.1093/mnras/stae2167

Sahl Rowther, Daniel J Price, Christophe Pinte, Rebecca Nealon, Farzana Meru, Richard Alexander

{"title":"Short-lived gravitational instability in isolated irradiated discs","authors":"Sahl Rowther, Daniel J Price, Christophe Pinte, Rebecca Nealon, Farzana Meru, Richard Alexander","doi":"10.1093/mnras/stae2167","DOIUrl":"https://doi.org/10.1093/mnras/stae2167","url":null,"abstract":"Irradiation from the central star controls the temperature structure in protoplanetary discs. Yet simulations of gravitational instability typically use models of stellar irradiation with varying complexity, or ignore it altogether, assuming heat generated by spiral shocks is balanced by cooling, leading to a self-regulated state. In this paper, we perform simulations of irradiated, gravitationally unstable protoplanetary discs using 3D hydrodynamics coupled with live Monte-Carlo radiative transfer. We find that the resulting temperature profile is approximately constant in time, since the thermal effects of the star dominate. Hence, the disc cannot regulate gravitational instabilities by adjusting the temperatures in the disc. In a 0.1M⊙ disc, the disc instead adjusts by angular momentum transport induced by the spiral arms, leading to steadily decreasing surface density, and hence quenching of the instability. Thus, strong spiral arms caused by self-gravity would not persist for longer than ten thousand years in the absence of fresh infall, although weak spiral structures remain present over longer timescales. Using synthetic images at 1.3mm, we find that spirals formed in irradiated discs are challenging to detect. In higher mass discs, we find that fragmentation is likely because the dominant stellar irradiation overwhelms the stabilising influence of PdV work and shock heating in the spiral arms.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256360","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

引用次数: 0

Inelastic scattering of PO+ by H2 at interstellar temperatures 星际温度下 H2 对 PO+ 的非弹性散射

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-19 DOI: 10.1093/mnras/stae2166

Pooja Chahal, Apoorv Kushwaha, T J Dhilip Kumar

{"title":"Inelastic scattering of PO+ by H2 at interstellar temperatures","authors":"Pooja Chahal, Apoorv Kushwaha, T J Dhilip Kumar","doi":"10.1093/mnras/stae2166","DOIUrl":"https://doi.org/10.1093/mnras/stae2166","url":null,"abstract":"Phosphorous species are of great interest in interstellar chemistry since they are the basic blocks for building life here on Earth. Modelling the abundance and environment of recently detected PO+ under non Local Thermodynamic Equilibrium (LTE) requires rotational spectra of the molecule along with accurate collisional rates with the most abundant species, hydrogen and helium. A new 4D ab initio potential energy surface (PES) of PO+ - H2 collision is calculated using CCSD(T)/CBS(DTQ) methodology considering rigid rotor approximation. The region containing the minima of the PES is augmented using neural networks (NN) model while very high potentials (&gt;2500 cm−1) and asymptotic region have been approximated using Slater and R−4 functions respectively. The close coupling calculations have been performed using MOLSCAT software for both ortho and para-H2. The rate coefficients have been reported for transitions j − j′ = 1 − 0, 2 − 1, 3 − 2 and 5 − 4 through which PO+ has been experimentally detected in ISM. The rate coefficients for even and odd transitions of PO+ with para-H2 are compared with that of helium and are found to be 1.1-2.0 times higher. For even transitions (Δj = 2), the ortho-H2 rates are 10% higher than para-H2 rates. However, the trend reverses in the case of odd transitions (Δj = 1) when higher J transitions are considered at low temperatures. At higher temperatures, the ortho rates cross the para-H2 rates and become larger than the latter. The new rate coefficients with both ortho and para-H2 will enable accurate modelling of the PO+ abundance in the interstellar medium under non-LTE conditions.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

引用次数: 0

Periodicity search in the timing of the 25 millisecond pulsars from the second data release of the European pulsar timing array 欧洲脉冲星定时阵列第二次数据发布中的 25 毫秒脉冲星定时周期性搜索

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-19 DOI: 10.1093/mnras/stae2162

Iuliana C Niţu, Michael J Keith, David J Champion, Ismaël Cognard, Gregory Desvignes, Lucas Guillemot, Yanjun Guo, Huanchen Hu, Jiwoong Jang, Jedrzej Jawor, Ramesh Karuppusamy, Evan F Keane, Michael Kramer, Kristen Lackeos, Kuo Liu, Robert A Main, Delphine Perrodin, Nataliya K Porayko, Golam M Shaifullah, Gilles Theureau

{"title":"Periodicity search in the timing of the 25 millisecond pulsars from the second data release of the European pulsar timing array","authors":"Iuliana C Niţu, Michael J Keith, David J Champion, Ismaël Cognard, Gregory Desvignes, Lucas Guillemot, Yanjun Guo, Huanchen Hu, Jiwoong Jang, Jedrzej Jawor, Ramesh Karuppusamy, Evan F Keane, Michael Kramer, Kristen Lackeos, Kuo Liu, Robert A Main, Delphine Perrodin, Nataliya K Porayko, Golam M Shaifullah, Gilles Theureau","doi":"10.1093/mnras/stae2162","DOIUrl":"https://doi.org/10.1093/mnras/stae2162","url":null,"abstract":"In this work, we investigated the presence of strictly periodic, as well as quasi-periodic signals, in the timing of the 25 millisecond pulsars from the EPTA DR2 dataset. This is especially interesting in the context of the recent hints of a gravitational wave background in these data, and the necessary further study of red-noise timing processes, which are known to behave quasi-periodically in some normal pulsars. We used Bayesian timing models developed through the run_enterprise pipeline: a strict periodicity was modelled as the influence of a planetary companion on the pulsar, while a quasi-periodicity was represented as a Fourier-domain Gaussian process. We found that neither model would clearly improve the timing models of the 25 millisecond pulsars in this dataset. This implies that noise and parameter estimates are unlikely to be biased by the presence of a (quasi-)periodicity in the timing data. Nevertheless, the results for PSRs J1744−1134 and J1012+5307 suggest that the standard noise models for these pulsars may not be sufficient. We also measure upper limits for the projected masses of planetary companions around each of the 25 pulsars. The data of PSR J1909−3744 yielded the best mass limits, such that we constrained the 95-percentile to ∼2 × 10−4 M⊕ (roughly the mass of the dwarf planet Ceres) for orbital periods between 5 d–17 yr. These are the best pulsar planet mass limits to date.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

引用次数: 0

The Gaia Ultracool Dwarf Sample – IV. GTC/OSIRIS optical spectra of Gaia late-M and L dwarfs 盖亚超冷矮星样本 - IV.盖亚晚M矮星和L矮星的 GTC/OSIRIS 光学光谱

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-19 DOI: 10.1093/mnras/stae2102

W J Cooper, H R A Jones, R L Smart, S L Folkes, J A Caballero, F Marocco, M C Gálvez Ortiz, A J Burgasser, J D Kirkpatrick, L M Sarro, B Burningham, A Cabrera-Lavers, P E Tremblay, C Reylé, N Lodieu, Z H Zhang, N J Cook, J F Faherty, D García-Álvarez, D Montes, D J Pinfield, A S Rajpurohit, J Shi

{"title":"The Gaia Ultracool Dwarf Sample – IV. GTC/OSIRIS optical spectra of Gaia late-M and L dwarfs","authors":"W J Cooper, H R A Jones, R L Smart, S L Folkes, J A Caballero, F Marocco, M C Gálvez Ortiz, A J Burgasser, J D Kirkpatrick, L M Sarro, B Burningham, A Cabrera-Lavers, P E Tremblay, C Reylé, N Lodieu, Z H Zhang, N J Cook, J F Faherty, D García-Álvarez, D Montes, D J Pinfield, A S Rajpurohit, J Shi","doi":"10.1093/mnras/stae2102","DOIUrl":"https://doi.org/10.1093/mnras/stae2102","url":null,"abstract":"As part of our comprehensive, ongoing characterisation of the low-mass end of the main sequence in the Solar neighbourhood, we used the OSIRIS instrument at the 10.4 m Gran Telescopio Canarias to acquire low- and mid-resolution (R≈300 and R≈2500) optical spectroscopy of 53 late-M and L ultracool dwarfs. Most of these objects are known but poorly investigated and lacking complete kinematics. We measured spectral indices, determined spectral types (six of which are new) and inferred effective temperature and surface gravity from BT-Settl synthetic spectra fits for all objects. We were able to measure radial velocities via line centre fitting and cross correlation for 46 objects, 29 of which lacked previous radial velocity measurements. Using these radial velocities in combination with the latest Gaia DR3 data, we also calculated Galactocentric space velocities. From their kinematics, we identified two candidates outside of the thin disc and four in young stellar kinematic groups. Two further ultracool dwarfs are apparently young field objects: 2MASSW J1246467+402715 (L4β), which has a potential, weak lithium absorption line, and G 196–3B (L3β), which was already known as young due to its well-studied primary companion.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

引用次数: 0

Uncovering Tidal Treasures: Automated Classification of faint tidal features in DECaLS Data 发现潮汐宝藏：DECaLS 数据中微弱潮汐特征的自动分类

IF 4.8 3区物理与天体物理

Monthly Notices of the Royal Astronomical Society Pub Date : 2024-09-19 DOI: 10.1093/mnras/stae2169

Alexander J Gordon, Annette M N Ferguson, Robert G Mann

{"title":"Uncovering Tidal Treasures: Automated Classification of faint tidal features in DECaLS Data","authors":"Alexander J Gordon, Annette M N Ferguson, Robert G Mann","doi":"10.1093/mnras/stae2169","DOIUrl":"https://doi.org/10.1093/mnras/stae2169","url":null,"abstract":"Tidal features are a key observable prediction of the hierarchical model of galaxy formation and contain a wealth of information about the properties and history of a galaxy. Modern wide-field surveys such as LSST and Euclid will revolutionise the study of tidal features. However, the volume of data will prohibit visual inspection to identify features, thereby motivating a need to develop automated detection methods. This paper presents a visual classification of ∼2, 000 galaxies from the DECaLS survey into different tidal feature categories: arms, streams, shells, and diffuse. We trained a Convolutional Neural Network (CNN) to reproduce the assigned visual classifications using these labels. Evaluated on a testing set where galaxies with tidal features were outnumbered ∼1 : 10, our network performed very well and retrieved a median 98.7 ± 0.3, 99.1 ± 0.5, 97.0 ± 0.8, and $99.4^{+0.2}_{-0.6}$ per cent of the actual instances of arm, stream, shell, and diffuse features respectively for just 20percnt contamination. A modified version that identified galaxies with any feature against those without achieved scores of $0.981^{+0.001}_{-0.003}$, $0.834^{+0.014}_{-0.026}$, $0.974^{+0.008}_{-0.004}$, and $0.900^{+0.073}_{-0.015}$ for the accuracy, precision, recall, and F1 metrics, respectively. We used a Gradient-weighted Class Activation Mapping analysis to highlight important regions on images for a given classification to verify the network was classifying the galaxies correctly. This is the first demonstration of using CNNs to classify tidal features into sub-categories, and it will pave the way for the identification of different categories of tidal features in the vast samples of galaxies that forthcoming wide-field surveys will deliver.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":null,"pages":null},"PeriodicalIF":4.8,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142256314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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}

引用次数: 0