Valencia Zhang, Saul Rappaport, Rahul Jayaraman, Donald W Kurtz, Gerald Handler, James Fuller, Tamas Borkovits
We have discovered a δ Scuti pulsator in a tight binary (P = 1.053 d) with nine pulsation modes whose frequencies are between 38 and 56 d−1. Each of these modes exhibits amplitude modulations and π-rad phase shifts twice per orbital cycle. Five of these modes exhibit amplitude and phase shifts that are readily explained by dipole pulsations along an axis that is aligned with the binary’s tidal axis. The novelty of the system lies in the remaining four pulsation modes, which we show are dipole pulsations along an axis that is perpendicular to both the tidal axis and the binary’s orbital angular momentum axis. There are additionally two pulsation modes whose amplitudes and phases do not change significantly with orbital phase; they are explained as dipole modes along an axis aligned with the orbital/rotation axis. Hence, we propose that TIC 184743498 is a tri-axial pulsator, the first of its kind.
{"title":"TIC 184743498: The first tri-axial stellar pulsator","authors":"Valencia Zhang, Saul Rappaport, Rahul Jayaraman, Donald W Kurtz, Gerald Handler, James Fuller, Tamas Borkovits","doi":"10.1093/mnras/stae010","DOIUrl":"https://doi.org/10.1093/mnras/stae010","url":null,"abstract":"We have discovered a δ Scuti pulsator in a tight binary (P = 1.053 d) with nine pulsation modes whose frequencies are between 38 and 56 d−1. Each of these modes exhibits amplitude modulations and π-rad phase shifts twice per orbital cycle. Five of these modes exhibit amplitude and phase shifts that are readily explained by dipole pulsations along an axis that is aligned with the binary’s tidal axis. The novelty of the system lies in the remaining four pulsation modes, which we show are dipole pulsations along an axis that is perpendicular to both the tidal axis and the binary’s orbital angular momentum axis. There are additionally two pulsation modes whose amplitudes and phases do not change significantly with orbital phase; they are explained as dipole modes along an axis aligned with the orbital/rotation axis. Hence, we propose that TIC 184743498 is a tri-axial pulsator, the first of its kind.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"9 4 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139459617","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}
The statistical technique “Complex Demodulation” (CDM) is used to track the amplitude and phase changes of periodicities in five naked T Tauri stars. The periodicities are most likely caused by dark spots on the stellar surfaces which are rotated into and out of view. Two of the stars (CD-56 1438, CD-72 248) show two independent periodicities, probably due to being binary weak-lined T Tauri stars. Two different low pass filters, operating respectively in the frequency and time domains, are used as part of the CDM methodology. Statistical aspects of the estimated amplitudes and phases are investigated in some detail: in particular, expressions are derived for standard errors, and for possible biases. A large variety of different types of amplitude and phase changes are found including approximately linear or quadratic, abrupt level shifts, pulses and oscillatory. Long term changes in amplitudes are aperiodic, but mimic long term cycles.
{"title":"Amplitude and Phase Changes in TESS Photometry of Five Short Period Weak-Lined T Tauri Stars","authors":"C Koen","doi":"10.1093/mnras/stae161","DOIUrl":"https://doi.org/10.1093/mnras/stae161","url":null,"abstract":"The statistical technique “Complex Demodulation” (CDM) is used to track the amplitude and phase changes of periodicities in five naked T Tauri stars. The periodicities are most likely caused by dark spots on the stellar surfaces which are rotated into and out of view. Two of the stars (CD-56 1438, CD-72 248) show two independent periodicities, probably due to being binary weak-lined T Tauri stars. Two different low pass filters, operating respectively in the frequency and time domains, are used as part of the CDM methodology. Statistical aspects of the estimated amplitudes and phases are investigated in some detail: in particular, expressions are derived for standard errors, and for possible biases. A large variety of different types of amplitude and phase changes are found including approximately linear or quadratic, abrupt level shifts, pulses and oscillatory. Long term changes in amplitudes are aperiodic, but mimic long term cycles.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"82 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139460110","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}
Superfluid vortices pinned to nuclear lattice sites or magnetic flux tubes in a neutron star evolve abruptly through a sequence of metastable spatial configurations, punctuated by unpinning avalanches associated with rotational glitches, as the stellar crust spins down electromagnetically. The metastable configurations are approximately but not exactly axisymmetric, causing the emission of persistent, quasimonochromatic, current quadrupole gravitational radiation. The characteristic gravitational wave strain h0 as a function of the spin frequency f and distance D from the Earth is bounded above by $h_0 = 1.2substack{+1.3 -0.9} times 10^{-32} (f/30,,{rm Hz})^{2.5} (D/1,,{rm kpc})^{-1}$, corresponding to a Poissonian spatial configuration (equal probability per unit area, i.e. zero inter-vortex repulsion), and bounded below by $h_0 = 1.8substack{+2.0 -1.5} times 10^{-50} (f/30,,{rm Hz})^{1.5} (D/1,,{rm kpc})^{-1}$, corresponding to a regular array (periodic separation, i.e. maximum inter-vortex repulsion). N-body point vortex simulations predict an intermediate scaling, $h_0 = 7.3substack{+7.9 -5.4} times 10^{-42} (f/30,,{rm Hz})^{1.9} (D/1,,{rm kpc})^{-1}$, which reflects a balance between the randomizing but spatially correlated action of superfluid vortex avalanches and the regularizing action of inter-vortex repulsion. The scaling is calibrated by conducting simulations with Nv ≤ 5 × 103 vortices and extrapolated to the astrophysical regime Nv ∼ 1017(f/30 Hz). The scaling is provisional, pending future computational advances to raise Nv and include three-dimensional effects such as vortex tension and turbulence.
{"title":"Persistent gravitational radiation from glitching pulsars. II. Updated scaling with vortex number","authors":"T Cheunchitra, A Melatos, J B Carlin, G Howitt","doi":"10.1093/mnras/stae130","DOIUrl":"https://doi.org/10.1093/mnras/stae130","url":null,"abstract":"Superfluid vortices pinned to nuclear lattice sites or magnetic flux tubes in a neutron star evolve abruptly through a sequence of metastable spatial configurations, punctuated by unpinning avalanches associated with rotational glitches, as the stellar crust spins down electromagnetically. The metastable configurations are approximately but not exactly axisymmetric, causing the emission of persistent, quasimonochromatic, current quadrupole gravitational radiation. The characteristic gravitational wave strain h0 as a function of the spin frequency f and distance D from the Earth is bounded above by $h_0 = 1.2substack{+1.3 -0.9} times 10^{-32} (f/30,,{rm Hz})^{2.5} (D/1,,{rm kpc})^{-1}$, corresponding to a Poissonian spatial configuration (equal probability per unit area, i.e. zero inter-vortex repulsion), and bounded below by $h_0 = 1.8substack{+2.0 -1.5} times 10^{-50} (f/30,,{rm Hz})^{1.5} (D/1,,{rm kpc})^{-1}$, corresponding to a regular array (periodic separation, i.e. maximum inter-vortex repulsion). N-body point vortex simulations predict an intermediate scaling, $h_0 = 7.3substack{+7.9 -5.4} times 10^{-42} (f/30,,{rm Hz})^{1.9} (D/1,,{rm kpc})^{-1}$, which reflects a balance between the randomizing but spatially correlated action of superfluid vortex avalanches and the regularizing action of inter-vortex repulsion. The scaling is calibrated by conducting simulations with Nv ≤ 5 × 103 vortices and extrapolated to the astrophysical regime Nv ∼ 1017(f/30 Hz). The scaling is provisional, pending future computational advances to raise Nv and include three-dimensional effects such as vortex tension and turbulence.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"8 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139460738","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}
The large number of gravitational wave (GW) detections have revealed the properties of the merging black hole binary population, but how such systems are formed is still heavily debated. Understanding the imprint of stellar physics on the observable GW population will shed light on how we can use the gravitational wave data, along with other observations, to constrain the poorly understood evolution of massive binaries. We perform a parameter study on the classical isolated binary formation channel with the population synthesis code SeBa to investigate how sensitive the properties of the coalescing binary black hole population are on the uncertainties related to first phase of mass transfer and stellar winds. We vary five assumptions: 1 and 2) the mass transfer efficiency and the angular momentum loss during the first mass transfer phase, 3) the mass transfer stability criteria for giant donors with radiative envelopes, 4) the effective temperature at which an evolved star develops a deep convective envelope, and 5) the mass loss rates of stellar winds. We find that current uncertainties related to first phase of mass transfer have a huge impact on the relative importance of different dominant channels, while the observable demographics of GW sources are not significantly affected. Our varied parameters have a complex, interrelated effect on the population properties of GW sources. Therefore, inference of massive binary physics from GW data alone remains extremely challenging, given the large uncertainties in our current models.
大量引力波（GW）探测揭示了并合黑洞双星群的特性，但这类系统是如何形成的仍存在很大争议。了解恒星物理学对可观测到的引力波群体的影响，将有助于我们了解如何利用引力波数据和其他观测数据来约束人们对大质量双星演化的不甚了解。我们利用种群合成代码 SeBa 对经典孤立双星形成通道进行了参数研究，以调查凝聚双黑洞种群的特性对质量转移第一阶段和恒星风相关不确定性的敏感程度。我们改变了五个假设：1和2）质量转移第一阶段的质量转移效率和角动量损失；3）具有辐射包层的巨型供体的质量转移稳定性标准；4）演化恒星形成深对流包层时的有效温度；5）恒星风的质量损失率。我们发现，目前与质量转移第一阶段有关的不确定性对不同主导通道的相对重要性有巨大影响，而全球变暖源的可观测人口统计则没有受到显著影响。我们所改变的参数对 GW 源的群体特性有着复杂而又相互关联的影响。因此，鉴于我们目前的模型存在很大的不确定性，仅从 GW 数据推断大质量双星物理学仍然极具挑战性。
{"title":"Importance of stable mass transfer and stellar winds for the formation of gravitational wave sources","authors":"Andris Dorozsmai, Silvia Toonen","doi":"10.1093/mnras/stae152","DOIUrl":"https://doi.org/10.1093/mnras/stae152","url":null,"abstract":"The large number of gravitational wave (GW) detections have revealed the properties of the merging black hole binary population, but how such systems are formed is still heavily debated. Understanding the imprint of stellar physics on the observable GW population will shed light on how we can use the gravitational wave data, along with other observations, to constrain the poorly understood evolution of massive binaries. We perform a parameter study on the classical isolated binary formation channel with the population synthesis code SeBa to investigate how sensitive the properties of the coalescing binary black hole population are on the uncertainties related to first phase of mass transfer and stellar winds. We vary five assumptions: 1 and 2) the mass transfer efficiency and the angular momentum loss during the first mass transfer phase, 3) the mass transfer stability criteria for giant donors with radiative envelopes, 4) the effective temperature at which an evolved star develops a deep convective envelope, and 5) the mass loss rates of stellar winds. We find that current uncertainties related to first phase of mass transfer have a huge impact on the relative importance of different dominant channels, while the observable demographics of GW sources are not significantly affected. Our varied parameters have a complex, interrelated effect on the population properties of GW sources. Therefore, inference of massive binary physics from GW data alone remains extremely challenging, given the large uncertainties in our current models.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"1 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139459613","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}
Jaya Maithil, Michael S Brotherton, Ohad Shemmer, Bin Luo, Pu Du, Jian-Min Wang, Hu Chen, Sarah C Gallagher, Yan-Rong Li, Rodrigo S Nemmen
The X-ray properties of Active Galactic Nuclei (AGNs) depend on their underlying physical parameters, particularly the accretion rate. We identified eight reverberation-mapped AGNs with some of the largest known accretion rates without high-quality X-ray data. We obtained new Chandra ACIS-S X-ray observations and nearly simultaneous optical spectrophotometry to investigate the properties of these AGNs with extreme super-Eddington accreting black holes (SEAMBHs). We combined our new X-ray measurements with those of other reverberation-mapped AGNs, which have the best-determined masses and accretion rates. The trend of the steepening of the spectral slope between X-ray and optical-UV, αox, with increasing optical-UV luminosity, L2500Å, holds true for even the most extreme SEAMBHs. One of our new SEAMBHs appears X-ray weak for its luminosity, perhaps due to absorption associated with orientation effects involving a slim disk thought to be present in highly accreting systems. The correlation of the $rm 2-8~ keV$ X-ray photon index with the accretion rate also holds for the extreme SEAMBHs, which show some of the largest photon indices reported for AGNs.
活动星系核（AGN）的 X 射线特性取决于其基本物理参数，特别是吸积率。在没有高质量 X 射线数据的情况下，我们发现了八个具有已知最大吸积率的反响映射 AGN。我们获得了新的钱德拉 ACIS-S X 射线观测数据和几乎同步的光学分光光度测量数据，以研究这些具有极端超爱丁顿吸积黑洞（SEAMBHs）的 AGN 的性质。我们将新的X射线测量结果与其他反响映射AGN的测量结果相结合，这些AGN的质量和吸积率都是最好确定的。X射线和光学紫外光谱斜率αox随着光学紫外光度L2500Å的增加而陡峭化的趋势，即使对最极端的SEAMBHs来说也是如此。在我们新发现的SEAMBHs中，有一个在其光度下显得X射线很弱，这可能是由于与细长盘的定向效应有关的吸收，而这种定向效应被认为是存在于高吸积系统中的。在极端的SEAMBHs中，$rm 2-8~ keV$ X射线光子指数与吸积率的相关性也是成立的，它们显示了一些已报道的AGNs中最大的光子指数。
{"title":"X-ray properties of reverberation-mapped AGNs with super-Eddington accreting massive black holes","authors":"Jaya Maithil, Michael S Brotherton, Ohad Shemmer, Bin Luo, Pu Du, Jian-Min Wang, Hu Chen, Sarah C Gallagher, Yan-Rong Li, Rodrigo S Nemmen","doi":"10.1093/mnras/stae115","DOIUrl":"https://doi.org/10.1093/mnras/stae115","url":null,"abstract":"The X-ray properties of Active Galactic Nuclei (AGNs) depend on their underlying physical parameters, particularly the accretion rate. We identified eight reverberation-mapped AGNs with some of the largest known accretion rates without high-quality X-ray data. We obtained new Chandra ACIS-S X-ray observations and nearly simultaneous optical spectrophotometry to investigate the properties of these AGNs with extreme super-Eddington accreting black holes (SEAMBHs). We combined our new X-ray measurements with those of other reverberation-mapped AGNs, which have the best-determined masses and accretion rates. The trend of the steepening of the spectral slope between X-ray and optical-UV, αox, with increasing optical-UV luminosity, L2500Å, holds true for even the most extreme SEAMBHs. One of our new SEAMBHs appears X-ray weak for its luminosity, perhaps due to absorption associated with orientation effects involving a slim disk thought to be present in highly accreting systems. The correlation of the $rm 2-8~ keV$ X-ray photon index with the accretion rate also holds for the extreme SEAMBHs, which show some of the largest photon indices reported for AGNs.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"67 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139460533","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}
Luca Amendola, Davi C Rodrigues, Sumit Kumar, Miguel Quartin
We test the possibility that the black holes (BHs) detected by LIGO-Virgo-KAGRA (LVK) may be cosmologically coupled and grow in mass proportionally to the cosmological scale factor to some power k, which may also act as the dark energy source if k ≈ 3. This approach was proposed as an extension of Kerr BHs embedded in cosmological backgrounds and possibly without singularities or horizons. In our analysis, we develop and apply two methods to test these cosmologically coupled BHs (CCBHs) either with or without connection to dark energy. We consider different scenarios for the time between the binary BH formation and its merger, and we find that the standard log-uniform distribution yields weaker constraints than the CCBH-corrected case. Assuming that the minimum mass of a BH with stellar progenitor is 2M⊙, we estimate the probability that at least one BH among the observed ones had an initial mass below this threshold. We obtain these probabilities either directly from the observed data or by assuming the LVK power-law-plus-peak mass distribution. In the latter case we find, at 2σ level, that k < 2.1 for the standard log-uniform distribution, or k < 1.1 for the CCBH-corrected distribution. Slightly weaker bounds are obtained in the direct method. Considering the uncertainties on the nature of CCBHs, we also find that the required minimum CCBH mass value to eliminate the tensions for k = 3 should be lower than 0.5 M⊙ (again at 2σ). Finally, we show that future observations have the potential to decisively confirm these bounds.
{"title":"Constraints on cosmologically coupled black holes from gravitational wave observations and minimal formation mass","authors":"Luca Amendola, Davi C Rodrigues, Sumit Kumar, Miguel Quartin","doi":"10.1093/mnras/stae143","DOIUrl":"https://doi.org/10.1093/mnras/stae143","url":null,"abstract":"We test the possibility that the black holes (BHs) detected by LIGO-Virgo-KAGRA (LVK) may be cosmologically coupled and grow in mass proportionally to the cosmological scale factor to some power k, which may also act as the dark energy source if k ≈ 3. This approach was proposed as an extension of Kerr BHs embedded in cosmological backgrounds and possibly without singularities or horizons. In our analysis, we develop and apply two methods to test these cosmologically coupled BHs (CCBHs) either with or without connection to dark energy. We consider different scenarios for the time between the binary BH formation and its merger, and we find that the standard log-uniform distribution yields weaker constraints than the CCBH-corrected case. Assuming that the minimum mass of a BH with stellar progenitor is 2M⊙, we estimate the probability that at least one BH among the observed ones had an initial mass below this threshold. We obtain these probabilities either directly from the observed data or by assuming the LVK power-law-plus-peak mass distribution. In the latter case we find, at 2σ level, that k &lt; 2.1 for the standard log-uniform distribution, or k &lt; 1.1 for the CCBH-corrected distribution. Slightly weaker bounds are obtained in the direct method. Considering the uncertainties on the nature of CCBHs, we also find that the required minimum CCBH mass value to eliminate the tensions for k = 3 should be lower than 0.5 M⊙ (again at 2σ). Finally, we show that future observations have the potential to decisively confirm these bounds.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"6 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139460694","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}
A Luna, T Marchetti, M Rejkuba, N W C Leigh, J Alonso-García, A Valenzuela Navarro, D Minniti, L C Smith
We search for high-velocity stars in the inner region of the Galactic bulge using a selected sample of red clump stars. Some of those stars might be considered hypervelocity stars (HVSs). Even though the HVSs ejection relies on an interaction with the supermassive black hole (SMBH) at the centre of the Galaxy, there are no confirmed detections of HVSs in the inner region of our Galaxy. With the detection of HVSs, ejection mechanism models can be constrained by exploring the stellar dynamics in the Galactic centre through a recent stellar interaction with the SMBH. Based on a previously developed methodology by our group, we searched with a sample of preliminary data from version 2 of the Vista Variables in the Via Lactea (VVV) Infrared Astrometric Catalogue (VIRAC2) and Gaia DR3 data, including accurate optical and NIR proper motions. This search resulted in a sample of 46 stars with transverse velocities larger than the local escape velocity within the Galactic bulge, of which 4 are prime candidate HVSs with high-proper motions consistent with being ejections from the Galactic centre. Adding to that, we studied a sample of reddened stars without a Gaia DR3 counterpart and found 481 stars with transverse velocities larger than the local escape velocity, from which 65 stars have proper motions pointing out of the Galactic centre and are candidate HVSs. In total, we found 69 candidate HVSs pointing away from the Galactic centre with transverse velocities larger than the local escape velocity.
我们利用精选的红团块恒星样本在银河系凸起内部区域寻找高速恒星。其中一些恒星可能被认为是超高速恒星（HVSs）。尽管HVSs的抛射依赖于与银河系中心的超大质量黑洞（SMBH）的相互作用，但在我们的银河系内部区域还没有确凿的HVSs探测结果。在探测到HVS之后，就可以通过探索银河系中心恒星与SMBH近期相互作用的动态来约束抛射机制模型。根据我们课题组之前开发的方法，我们利用 Vista Variables in the Via Lactea (VVV) Infrared Astrometric Catalogue (VIRAC2) 第 2 版的初步数据样本和 Gaia DR3 数据（包括精确的光学和近红外正确运动）进行了搜索。通过搜索，我们获得了银河凸起内横向速度大于当地逃逸速度的 46 颗恒星样本，其中 4 颗恒星是主要的候选 HVS，它们的高正确运动符合从银河中心喷出的情况。此外，我们还研究了一个没有 Gaia DR3 对应星的变红恒星样本，发现了 481 颗横向速度大于本地逃逸速度的恒星，其中 65 颗恒星的正确运动指向银河中心之外，是候选 HVS。我们总共发现了 69 颗横向速度大于当地逃逸速度的、指向银河中心以外的候选 HVS。
{"title":"New candidate hypervelocity red clump stars in the inner Galactic bulge","authors":"A Luna, T Marchetti, M Rejkuba, N W C Leigh, J Alonso-García, A Valenzuela Navarro, D Minniti, L C Smith","doi":"10.1093/mnras/stae128","DOIUrl":"https://doi.org/10.1093/mnras/stae128","url":null,"abstract":"We search for high-velocity stars in the inner region of the Galactic bulge using a selected sample of red clump stars. Some of those stars might be considered hypervelocity stars (HVSs). Even though the HVSs ejection relies on an interaction with the supermassive black hole (SMBH) at the centre of the Galaxy, there are no confirmed detections of HVSs in the inner region of our Galaxy. With the detection of HVSs, ejection mechanism models can be constrained by exploring the stellar dynamics in the Galactic centre through a recent stellar interaction with the SMBH. Based on a previously developed methodology by our group, we searched with a sample of preliminary data from version 2 of the Vista Variables in the Via Lactea (VVV) Infrared Astrometric Catalogue (VIRAC2) and Gaia DR3 data, including accurate optical and NIR proper motions. This search resulted in a sample of 46 stars with transverse velocities larger than the local escape velocity within the Galactic bulge, of which 4 are prime candidate HVSs with high-proper motions consistent with being ejections from the Galactic centre. Adding to that, we studied a sample of reddened stars without a Gaia DR3 counterpart and found 481 stars with transverse velocities larger than the local escape velocity, from which 65 stars have proper motions pointing out of the Galactic centre and are candidate HVSs. In total, we found 69 candidate HVSs pointing away from the Galactic centre with transverse velocities larger than the local escape velocity.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"67 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139460575","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}
Run Wen, Xian Zhong Zheng, Yunkun Han, Xiaohu Yang, Xin Wang, Hu Zou, Fengshan Liu, Xin Zhang, Ying Zu, Dong Dong Shi, Yizhou Gu, Yirong Wang
The Chinese Space Station Telescope (CSST) slitless spectroscopic survey will observe objects to a limiting magnitude of ∼23 mag (5σ, point sources) in U, V, and I over 17,500 square degrees. The spectroscopic observations are expected to be highly efficient and complete for mapping galaxies over 0 < z < 1 with secure redshift measurements at spectral resolutions of R ∼ 200, providing unprecedented datasets for cosmological studies. To quantitatively examine the survey potential, we develop a software tool, namely the CSST Emulator for Slitless Spectroscopy (CESS), to quickly generate simulated 1-D slitless spectra with limited computing resources. We introduce the architecture of CESS and the detailed process of creating simulated CSST slitless spectra. The extended light distribution of a galaxy induces the self-broadening effect on the 1-D slitless spectrum. We quantify the effect using morphological parameters: Sérsic index, effective radius, position angle, and axis ratio. Moreover, we also develop a module for CESS to estimate the overlap contamination rate for CSST grating observations of galaxies in galaxy clusters. Applying CESS to the high-resolution model spectra of a sample of ∼140 million galaxies with mz < 21 mag selected from the DESI LS DR9 catalogue, we obtain the simulated CSST slitless spectra. We examine the dependence of measurement errors on different types of galaxies due to instrumental and observational effects and quantitatively investigate the redshift completeness for different environments out to z ∼ 1. Our results show that the CSST spectroscopy is able to provide secure redshifts for about one-quarter of the sample galaxies.
中国空间站望远镜（CSST）无缝隙光谱巡天将在 17500 平方度的范围内观测 U、V 和 I 三类极限星等为 23 等（5σ，点源）的天体。预计光谱观测将非常高效和完整地测绘 0 < z < 1 以上的星系，并以 R ∼ 200 的光谱分辨率进行可靠的红移测量，为宇宙学研究提供前所未有的数据集。为了定量研究巡天的潜力，我们开发了一个软件工具，即 CSST 仿真器无缝光谱（CESS），利用有限的计算资源快速生成模拟的一维无缝光谱。我们将介绍CESS的结构和创建模拟CSST无缝光谱的详细过程。星系的扩展光分布会对一维无缝光谱产生自扩宽效应。我们利用形态参数来量化这种效应：塞里斯指数、有效半径、位置角和轴比。此外，我们还为 CESS 开发了一个模块，用于估算对星系团中的星系进行 CSST 光栅观测时的重叠污染率。将 CESS 应用于从 DESI LS DR9 目录中选取的 1.4 亿个 mz < 21 mag 的星系样本的高分辨率模型光谱，我们得到了模拟的 CSST 无缝光谱。我们研究了仪器和观测效应导致的测量误差对不同类型星系的依赖性，并定量研究了不同环境下 z ∼ 1 的红移完整性。结果表明，CSST 光谱能够为大约四分之一的样本星系提供可靠的红移。
{"title":"CSST Large-scale Structure Analysis Pipeline: II. the CSST Emulator for Slitless Spectroscopy (CESS)","authors":"Run Wen, Xian Zhong Zheng, Yunkun Han, Xiaohu Yang, Xin Wang, Hu Zou, Fengshan Liu, Xin Zhang, Ying Zu, Dong Dong Shi, Yizhou Gu, Yirong Wang","doi":"10.1093/mnras/stae157","DOIUrl":"https://doi.org/10.1093/mnras/stae157","url":null,"abstract":"The Chinese Space Station Telescope (CSST) slitless spectroscopic survey will observe objects to a limiting magnitude of ∼23 mag (5σ, point sources) in U, V, and I over 17,500 square degrees. The spectroscopic observations are expected to be highly efficient and complete for mapping galaxies over 0 &lt; z &lt; 1 with secure redshift measurements at spectral resolutions of R ∼ 200, providing unprecedented datasets for cosmological studies. To quantitatively examine the survey potential, we develop a software tool, namely the CSST Emulator for Slitless Spectroscopy (CESS), to quickly generate simulated 1-D slitless spectra with limited computing resources. We introduce the architecture of CESS and the detailed process of creating simulated CSST slitless spectra. The extended light distribution of a galaxy induces the self-broadening effect on the 1-D slitless spectrum. We quantify the effect using morphological parameters: Sérsic index, effective radius, position angle, and axis ratio. Moreover, we also develop a module for CESS to estimate the overlap contamination rate for CSST grating observations of galaxies in galaxy clusters. Applying CESS to the high-resolution model spectra of a sample of ∼140 million galaxies with mz &lt; 21 mag selected from the DESI LS DR9 catalogue, we obtain the simulated CSST slitless spectra. We examine the dependence of measurement errors on different types of galaxies due to instrumental and observational effects and quantitatively investigate the redshift completeness for different environments out to z ∼ 1. Our results show that the CSST spectroscopy is able to provide secure redshifts for about one-quarter of the sample galaxies.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"40 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139460742","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}
Paul A Crowther, M J Barlow, P Royer, D J Hillier, J M Bestenlehner, P W Morris, R Wesson
We present Herschel PACS spectroscopy of the [O iii] 88.4μm fine-structure line in the nearby WC8+O binary system γ Vel to determine its oxygen abundance. The critical density of this line corresponds to several 105R* such that it is spatially extended in PACS observations at the 336 pc distance to γ Vel. Two approaches are used, the first involving a detailed stellar atmosphere analysis of γ Vel using cmfgen, extending to Ne ∼ 100 cm−3 in order to fully sample the line formation region of [O iii] 88.4 μm. The second approach involves the analytical model introduced by Barlow et al. and revised by Dessart et al., additionally exploiting ISO LWS spectroscopy of [O iii] 51.8 μm. We obtain higher luminosities for the WR and O components of γ Vel with respect to De Marco et al., log L/L⊙ = 5.31 and 5.56, respectively, primarily due to the revised (higher) interferometric distance. We obtain an oxygen mass fraction of XO = 1.0±0.3% for an outer wind volume filling factor of f = 0.5 ± 0.25, favouring either standard or slightly reduced Kunz et al. rates for the 12C(α, γ)16O reaction from comparison with BPASS binary population synthesis models. We also revisit neon and sulphur abundances in the outer wind of γ Vel from ISO SWS spectroscopy of [S iv] 10.5 μm, [Ne ii] 12.8 μm and [Ne iii] 15.5 μm. The inferred neon abundance XNe = 2.0$_{-0.6}^{+0.4}$% is in excellent agreement with BPASS predictions, while the sulphur abundance of XS = 0.04 ± 0.01% agrees with the solar abundance, as expected for unprocessed elements.
我们展示了赫歇尔 PACS 对附近 WC8+O 双星系统 γ Vel 中 [O iii] 88.4μm 细结构线的光谱分析，以确定其氧丰度。这条线的临界密度相当于几个 105R*，因此在距离 γ Vel 336 pc 处的 PACS 观测中，它在空间上是延伸的。我们采用了两种方法，第一种是利用 cmfgen 对 γ Vel 进行详细的恒星大气分析，将其扩展到 Ne ∼ 100 cm-3，以便对 [O iii] 88.4 μm 的谱线形成区域进行全面采样。第二种方法涉及 Barlow 等人提出并经 Dessart 等人修订的分析模型，另外还利用了 [O iii] 51.8 μm 的 ISO LWS 光谱。与 De Marco 等人的研究相比，我们得到的 γ Vel 的 WR 和 O 分量的光度更高，分别为 log L/L⊙ = 5.31 和 5.56，这主要是由于修订后的（更高的）干涉距离所致。通过与 BPASS 双星种群合成模型的比较，我们得出外风体积填充因子为 f = 0.5 ± 0.25 时的氧气质量分数为 XO = 1.0±0.3%，这表明 Kunz 等人的 12C(α,γ)16O 反应速率符合标准或略有降低。我们还通过 ISO SWS 光谱测定的 [S iv] 10.5 μm、[Ne ii] 12.8 μm 和 [Ne iii] 15.5 μm，重新研究了 γ Vel 外风中的氖和硫丰度。推断出的氖丰度 XNe = 2.0$_{-0.6}^{+0.4}$%与 BPASS 预测非常吻合，而硫丰度 XS = 0.04 ± 0.01% 与太阳丰度吻合，这是对未加工元素的预期。
{"title":"Oxygen abundance of γ Vel from [O iii] 88μm Herschel/PACS spectroscopy","authors":"Paul A Crowther, M J Barlow, P Royer, D J Hillier, J M Bestenlehner, P W Morris, R Wesson","doi":"10.1093/mnras/stae145","DOIUrl":"https://doi.org/10.1093/mnras/stae145","url":null,"abstract":"We present Herschel PACS spectroscopy of the [O iii] 88.4μm fine-structure line in the nearby WC8+O binary system γ Vel to determine its oxygen abundance. The critical density of this line corresponds to several 105R* such that it is spatially extended in PACS observations at the 336 pc distance to γ Vel. Two approaches are used, the first involving a detailed stellar atmosphere analysis of γ Vel using cmfgen, extending to Ne ∼ 100 cm−3 in order to fully sample the line formation region of [O iii] 88.4 μm. The second approach involves the analytical model introduced by Barlow et al. and revised by Dessart et al., additionally exploiting ISO LWS spectroscopy of [O iii] 51.8 μm. We obtain higher luminosities for the WR and O components of γ Vel with respect to De Marco et al., log L/L⊙ = 5.31 and 5.56, respectively, primarily due to the revised (higher) interferometric distance. We obtain an oxygen mass fraction of XO = 1.0±0.3% for an outer wind volume filling factor of f = 0.5 ± 0.25, favouring either standard or slightly reduced Kunz et al. rates for the 12C(α, γ)16O reaction from comparison with BPASS binary population synthesis models. We also revisit neon and sulphur abundances in the outer wind of γ Vel from ISO SWS spectroscopy of [S iv] 10.5 μm, [Ne ii] 12.8 μm and [Ne iii] 15.5 μm. The inferred neon abundance XNe = 2.0$_{-0.6}^{+0.4}$% is in excellent agreement with BPASS predictions, while the sulphur abundance of XS = 0.04 ± 0.01% agrees with the solar abundance, as expected for unprocessed elements.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"1 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139459608","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}
Stellar light curves contain valuable information about oscillations and granulation, offering insights into stars’ internal structures and evolutionary states. Traditional asteroseismic techniques, primarily focused on power spectral analysis, often overlook the crucial phase information in these light curves. Addressing this gap, recent machine learning applications, particularly those using Convolutional Neural Networks (CNNs), have made strides in inferring stellar properties from light curves. However, CNNs are limited by their localized feature extraction capabilities. In response, we introduce Astroconformer, a Transformer-based deep learning framework, specifically designed to capture long-range dependencies in stellar light curves. Our empirical analysis centers on estimating surface gravity (log g), using a dataset derived from single-quarter Kepler light curves with log g values ranging from 0.2 to 4.4. Astroconformer demonstrates superior performance, achieving a root-mean-square-error (RMSE) of 0.017 dex at log g ≈ 3 in data-rich regimes and up to 0.1 dex in sparser areas. This performance surpasses both K-nearest neighbor models and advanced CNNs. Ablation studies highlight the influence of receptive field size on model effectiveness, with larger fields correlating to improved results. Astroconformer also excels in extracting νmax with high precision. It achieves less than 2 % relative median absolute error for 90-day red giant light curves. Notably, the error remains under 3 % for 30-day light curves, whose oscillations are undetectable by a conventional pipeline in 30 % cases. Furthermore, the attention mechanisms in Astroconformer align closely with the characteristics of stellar oscillations and granulation observed in light curves.
{"title":"Astroconformer: The prospects of analyzing stellar light curves with transformer-based deep learning models","authors":"Jia-Shu Pan, Yuan-Sen Ting, Jie Yu","doi":"10.1093/mnras/stae068","DOIUrl":"https://doi.org/10.1093/mnras/stae068","url":null,"abstract":"Stellar light curves contain valuable information about oscillations and granulation, offering insights into stars’ internal structures and evolutionary states. Traditional asteroseismic techniques, primarily focused on power spectral analysis, often overlook the crucial phase information in these light curves. Addressing this gap, recent machine learning applications, particularly those using Convolutional Neural Networks (CNNs), have made strides in inferring stellar properties from light curves. However, CNNs are limited by their localized feature extraction capabilities. In response, we introduce Astroconformer, a Transformer-based deep learning framework, specifically designed to capture long-range dependencies in stellar light curves. Our empirical analysis centers on estimating surface gravity (log g), using a dataset derived from single-quarter Kepler light curves with log g values ranging from 0.2 to 4.4. Astroconformer demonstrates superior performance, achieving a root-mean-square-error (RMSE) of 0.017 dex at log g ≈ 3 in data-rich regimes and up to 0.1 dex in sparser areas. This performance surpasses both K-nearest neighbor models and advanced CNNs. Ablation studies highlight the influence of receptive field size on model effectiveness, with larger fields correlating to improved results. Astroconformer also excels in extracting νmax with high precision. It achieves less than 2 % relative median absolute error for 90-day red giant light curves. Notably, the error remains under 3 % for 30-day light curves, whose oscillations are undetectable by a conventional pipeline in 30 % cases. Furthermore, the attention mechanisms in Astroconformer align closely with the characteristics of stellar oscillations and granulation observed in light curves.","PeriodicalId":18930,"journal":{"name":"Monthly Notices of the Royal Astronomical Society","volume":"26 1","pages":""},"PeriodicalIF":4.8,"publicationDate":"2024-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139460498","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}
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