Astrophysics and Space Science最新文献

Towards cosmological inference on unlabeled out-of-distribution HI observational data

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2025-02-10 DOI: 10.1007/s10509-025-04405-y

Sambatra Andrianomena, Sultan Hassan

{"title":"Towards cosmological inference on unlabeled out-of-distribution HI observational data","authors":"Sambatra Andrianomena, Sultan Hassan","doi":"10.1007/s10509-025-04405-y","DOIUrl":"10.1007/s10509-025-04405-y","url":null,"abstract":"<div>We present an approach that can be utilized in order to account for the covariate shift between two datasets of the same observable with different distributions. This helps improve the generalizability of a neural network model trained on in-distribution samples (IDs) when inferring cosmology at the field level on out-of-distribution samples (OODs) of unknown labels. We make use of HI maps from the two simulation suites in CAMELS, IllustrisTNG and SIMBA. We consider two different techniques, namely adversarial approach and optimal transport, to adapt a target network whose initial weights are those of a source network pre-trained on a labeled dataset. Results show that after adaptation, salient features that are extracted by source and target encoders are well aligned in the embedding space. This indicates that the target encoder has learned the representations of the target domain via the adversarial training and optimal transport. Furthermore, in all scenarios considered in our analyses, the target encoder, which does not have access to any labels ((Omega _{mathrm{m}})) during adaptation phase, is able to retrieve the underlying (Omega _{mathrm{m}}) from out-of-distribution maps to a great accuracy of (R^{2}) score ≥ 0.9, comparable to the performance of the source encoder trained in a supervised learning setup. We further test the viability of the techniques when only a few out-of-distribution instances are available for training and find that the target encoder still reasonably recovers the matter density. Our approach is critical in extracting information from upcoming large scale surveys.</div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 2","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143373255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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

Spectroscopic diagnosis of a B-class flare and an associated filament eruption

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2025-02-10 DOI: 10.1007/s10509-025-04404-z

B. Suresh Babu, Pradeep Kayshap, Sharad C. Tripathi

{"title":"Spectroscopic diagnosis of a B-class flare and an associated filament eruption","authors":"B. Suresh Babu, Pradeep Kayshap, Sharad C. Tripathi","doi":"10.1007/s10509-025-04404-z","DOIUrl":"10.1007/s10509-025-04404-z","url":null,"abstract":"<div>The flare ribbon and an associated filament eruption are diagnosed using O iv 1401.16 Å, Si iv 1402.77 Å, and Mg ii k 2796.35 Å spectral lines provided by Interface Region Imaging Spectrograph (IRIS). The flare ribbons have downflow (redshifts) in all these lines, and this redshift decreases from the transition region to the chromosphere. While the overlapping region (flare-ribbon+filament rise/eruption) is dominated by upflows (blueshifts) in all three spectral lines. We found an extremely blueshifted Si iv profile (i.e., blueshift around −180 km/s) in the overlapping region. The mean non-thermal velocity (vnt) in the flare ribbons is higher in O iv than Si iv. While, in the overlapping region, O iv have lower vnt than Si iv. Note that very high vnt around 80 km/s (in Si iv) exists in this weak B-class flare. The Mg ii k line widths are almost the same in the flare ribbon and overlapping region but, they are extremely broad than previously reported. We found double peak profiles of Si iv and O iv in the overlapping region. Most probably, one peak is due to downflow (flare ribbon) and another due to upflow (filament rise/eruption). We report a high redshift of more than 150 km/s in the weak B-class flare. In some cases, both peaks show upflows which might be the result of the superposition of two different sources, i.e., overlapping of two different velocity distributions in the line of sight.</div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 2","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143373341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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

Solar orbiter: a short review of the mission and early science results

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2025-02-05 DOI: 10.1007/s10509-025-04400-3

Louise Harra, Daniel Müller

{"title":"Solar orbiter: a short review of the mission and early science results","authors":"Louise Harra, Daniel Müller","doi":"10.1007/s10509-025-04400-3","DOIUrl":"10.1007/s10509-025-04400-3","url":null,"abstract":"<div>On 9 February 2020 at 11:03 pm EST, an Atlas V 411 rocket launched the ESA/ NASA Solar Orbiter mission. This mission was the culmination of decades of work across many countries to achieve the goal of getting close to the Sun and measuring how the Sun creates and maintains the heliosphere. The mission’s goal is to understand how the inner heliosphere works and how solar activity impacts it. The spacecraft achieves this with a specially designed highly elliptical orbit that gets close to the Sun twice a year. It reaches as close as 0.28 au requiring a novel heat shield to protect the instruments from the intense heat (the front side of the heat shield reaches around 500 ∘C at this location). There are ten scientific instruments onboard: Six remote-sensing instruments observe solar activity across the electromagnetic spectrum on small and large scales, including imaging the source regions of the solar wind. They are accompanied by four in-situ instruments to probe the properties of the solar wind as it flows past the spacecraft. This review paper describes a selection of results from Solar Orbiter during its cruise phase and the beginning of its nominal scientific operations phase, and looks towards the next phases of the mission, when the spacecraft leaves the ecliptic plane to observe the solar poles for the first time.</div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 2","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s10509-025-04400-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143184792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Mergers of compact objects with cores of massive stars: evolutionary pathways, r-process nucleosynthesis and multi-messenger signatures

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2025-02-04 DOI: 10.1007/s10509-025-04402-1

Aldana Grichener

{"title":"Mergers of compact objects with cores of massive stars: evolutionary pathways, r-process nucleosynthesis and multi-messenger signatures","authors":"Aldana Grichener","doi":"10.1007/s10509-025-04402-1","DOIUrl":"10.1007/s10509-025-04402-1","url":null,"abstract":"<div>The study of massive binary systems has steadily progressed over the past decades, with increasing focus on their evolution, interactions and mergers, driven by improvements in computational modelling and observational techniques. In particular, when a binary system involves a massive giant and a neutron star (NS) or a black hole (BH) that go through common envelope evolution (CEE), it might result in the merger of the compact object with the core of its giant companion, giving rise to various high energy astrophysical phenomena. We review the different evolutionary channels that lead to compact object-core mergers, key physical processes with emphasis on the role of accretion physics, feasibility of r-process nucleosynthesis, expected observable electromagnetic, neutrino and gravitational-wave (GW) signatures, as well as potential correlation with detected core collapse supernovae (CCSNe), luminous fast blue optical transients (LFBOTs) and low luminosity long gamma-ray bursts (LGRBs). After presenting our current understanding of these mergers, we conclude discussing prospects for future advancements.</div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 2","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143108631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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

Model-independent gamma-ray bursts constraints on cosmological models using machine learning

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2025-01-31 DOI: 10.1007/s10509-025-04401-2

Bin Zhang, Huifeng Wang, Xiaodong Nong, GuangZhen Wang, Puxun Wu, Nan Liang

引用次数: 0

An efficient approximation method for nonlinear singular value problems arising in astrophysics: an operational matrix approach

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2025-01-29 DOI: 10.1007/s10509-025-04399-7

G. Hariharan, J. Kavitha, R. Seethalakshmi, H. Jafari

引用次数: 0

SDSS-IV MaNGA: the environmental effects on some fundamental properties of early-type galaxies

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2025-01-27 DOI: 10.1007/s10509-025-04396-w

E. Abdellah, R. M. Samir, Z. Awad, M. Y. Amin

{"title":"SDSS-IV MaNGA: the environmental effects on some fundamental properties of early-type galaxies","authors":"E. Abdellah, R. M. Samir, Z. Awad, M. Y. Amin","doi":"10.1007/s10509-025-04396-w","DOIUrl":"10.1007/s10509-025-04396-w","url":null,"abstract":"<div>We studied the dependence of selected structural and kinematic properties of early-type galaxies (ETGs) on their environments. The selected sample, extracted from the SDSS-DR17 MaNGA survey, consists of 946 ETGs in clusters (cETGs) and 288 isolated ETGs (iETGs) within a spectroscopic redshift (zleq 0.15). We investigated the distribution of these galaxies in the Fundamental Plane (FP), Kormendy Relation (KR), Faber-Jackson Relation (FJR) and the Mass-Size Relation (MSR). We found that massive galaxies, whose stellar masses (M_{*}> 10^{11}M_{odot }), are predominantly elliptical ((>65%)). The analysis of the four scaling relations showed that the effect of the host environment is negligible for massive ((M_{*}>10^{11.5}M_{odot })) ETGs, most likely because of their passive evolution through dry mergers and/or stellar aging. On the other hand, low-mass ETGs are influenced by their environment, where iETGs with (M_{*}<10^{10}M_{odot }) and velocity dispersion (sigma _{0}leq 100) km/sec are (25%) more luminous and (11.5%) larger than cETGs. Low-mass cETGs may have suffered processes that removed their gas content and hence quenched star formation while low-mass iETGs may have experienced a recent wet merger that triggered star formation and led to their, currently, observed low mass-to-light ratio. However, further spectral analysis is needed to confirm these findings.</div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143109337","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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

Time-lag in hadronic channel: to explore delayed VHE-flare of 3C 279

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2025-01-27 DOI: 10.1007/s10509-025-04398-8

Sunanda, Reetanjali Moharana

引用次数: 0

EFT calculations of (S_{34}(E)) for the (^{3}H(alpha ,gamma )^{7}Li) radiative capture reaction

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2025-01-24 DOI: 10.1007/s10509-024-04385-5

H. Sadeghi, M. Khoddam

引用次数: 0

The shape of magnetic hole in affecting electron distribution function and wave properties 磁孔的形状影响电子分布函数和波的性质

IF 1.8 4区物理与天体物理

Astrophysics and Space Science Pub Date : 2025-01-21 DOI: 10.1007/s10509-025-04397-9

Z. Y. Xu, H. S. Fu, Y. Yu, Z. Wang, W. D. Fu, W. Z. Zhang, J. B. Cao

{"title":"The shape of magnetic hole in affecting electron distribution function and wave properties","authors":"Z. Y. Xu, H. S. Fu, Y. Yu, Z. Wang, W. D. Fu, W. Z. Zhang, J. B. Cao","doi":"10.1007/s10509-025-04397-9","DOIUrl":"10.1007/s10509-025-04397-9","url":null,"abstract":"<div>Magnetic holes (MHs) have been widely observed in astrophysical and space plasmas. However, due to the lack of reconstruction method, the effects of MH shape on electron distribution function and wave properties are still unclear. In this study, we report a series of MHs in Earth’s magnetotail. We particularly focus on two of them with the clearest data features, reconstruct their topologies using the Second-Order Taylor Expansion (SOTE) method, and find their shapes to be bulging and deflated. Comparatively, the bulging MH exhibits a donut electron distribution, which may be attributed to the combined effects of internal expansion-induced betatron cooling and boundary contraction-induced betatron acceleration, while the deflated MH presents a pancake electron distribution. The beam instability and temperature anisotropy inside the bulging MH also excite electron cyclotron waves and whistler waves, respectively, while the deflated MH does not exhibit these types of waves. All these findings help us understand the geometric properties and evolutions of MHs.</div>","PeriodicalId":8644,"journal":{"name":"Astrophysics and Space Science","volume":"370 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142994907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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