New Astronomy最新文献_第5页

Characterizing the spiral Lin–Shu-type density-wave structure of the Milky Way in the 3-kpc-scale solar neighborhood: Astrophysical conclusions

IF 1.9 4区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

New Astronomy

Pub Date : 2024-12-06 DOI: 10.1016/j.newast.2024.102340

Evgeny Griv , Michael Gedalin , Luis Martinez-Medina , Angeles Pérez-Villegas , Ing-Guey Jiang

In the concluding work of a series of studies, the disk’s spiral structure of the Milky Way is anew considered as a Lin–Shu-type density-wave pattern. As a step forward, a sample of

\sim 500000

stars from a total of 656161 sources within 3 kpc from the Sun and

\pm 250

pc from the disk’s mean plane identified in the Gaia EDR3 is examined. The parameters of Galactic rotation and solar peculiar motion corrected for the effects of 3D density waves, and the radial, azimuthal, and vertical components of the streaming motion of stars due to the spiral arms are derived from the measured velocities of objects. The parameters of the waves are also estimated. Two almost equal scales of periodic compression/rarefaction irregularity of the streaming velocity field with the radial and vertical wavelengths of

≲ 2

kpc in the form of a spiral density wave propagating in the disk at the Sun are revealed, which are reasonably related to the global spiral pattern. The Sun is located between the central part and the inner edge of the Orion (Local) wave arm. The spiral pattern in the kinematics of stars is consistent with the spatial distribution of the nearby arm segments traced by young populations. In agreement with the original Lin and Shu proposal, the gravitational field associated with the arms is a small deviation from the total gravitational field of the Galaxy that is axisymmetric in the mean. The very existence of the spiral arrangement in the velocity field suggests that the localized disk is gravitationally unstable.

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引用次数: 0

Spectroscopic and photometric study for five late G- to K-type short-period contact binaries 五个晚G- k型短周期接触双星的光谱和光度研究

IF 1.9 4区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

New Astronomy

Pub Date : 2024-11-26 DOI: 10.1016/j.newast.2024.102329

Qing Dong , Raúl Michel , Zhi-Hua Wang , Iván Mora Zamora

We reported spectroscopy and photometry for five ultra-short period W UMa-type contact binaries. Eleven sets of low resolution spectra are obtained from the Large Sky Area Multiobject Fiber Spectroscopic Telescope (LAMOST) database and analyzed. It has been determined that these systems are late G- to K-type stars: G7V for J0658, G9V for LINEAR 3562115, K0V for PS Com, and K5V for LINEAR 11570575. Additionally, it was observed that the cooler the star, the stronger the sodium absorption line. Seven sets of complete light curves, including two sets of TESS data for PS Com and V0568 Peg, were analyzed using the W-D code. All the five targets are W-subtype systems with mass ratios (

q

) greater than 1. The light curves of the two medium contact systems (J0658 and LINEAR 11570575) are symmetric. In contrast, the light curves of the three shallow contact binaries (LINEAR 3562115, PS Com, and V0568 Peg) show differences between their two maxima, Max.I and Max.II, suggesting the presence of cool or hot spots on their surfaces. According to the H-R diagram, the more massive components of these targets are situated between the ZAMS and TAMS, while the less massive ones are overheated due to energy transfer within the common envelope. As these binaries lose angular momentum, they will evolve into deep, low mass ratio contact binaries.

我们报告了五颗超短周期W UMa型接触双星的光谱和测光结果。我们从大天区多天体光纤光谱望远镜（LAMOST）数据库中获得了11组低分辨率光谱，并对其进行了分析。经测定，这些系统都是晚期G型到K型恒星：J0658为G7V，LINEAR 3562115为G9V，PS Com为K0V，LINEAR 11570575为K5V。此外，还观察到恒星温度越低，钠吸收线就越强。利用 W-D 代码分析了七组完整的光变曲线，包括 PS Com 和 V0568 Peg 的两组 TESS 数据。五个目标都是质量比（q）大于 1 的 W 亚型系统。两个中等接触系统（J0658 和 LINEAR 11570575）的光变曲线是对称的。相比之下，三个浅接触双星（LINEAR 3562115、PS Com和V0568 Peg）的光曲线在两个最大值（Max.I和Max.II）之间存在差异，这表明它们的表面存在冷点或热点。根据H-R图，这些目标中质量较大的部分位于ZAMS和TAMS之间，而质量较小的部分则由于共同包层内的能量转移而过热。随着这些双星失去角动量，它们将演变成深层的低质量比接触双星。

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引用次数: 0

A robust assessment of the local anisotropy of the Hubble constant in the Pantheon+ sample Pantheon+ 样本中哈勃常数局部各向异性的稳健评估

IF 1.9 4区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

New Astronomy

Pub Date : 2024-11-23 DOI: 10.1016/j.newast.2024.102331

Yves-Henri Sanejouand

Magnitude predictions of

Λ

CDM, as parametrized by the Planck collaboration, are not consistent with the supernova Ia data of the whole Pantheon+ sample even when, in order to take into account the uncertainty about its value, the Hubble constant is adjusted. This is a likely consequence of the increase of the number of low-redshift supernovae in the Pantheon+ sample, with respect to previous such samples.

In order to find directions in the sky where the Hubble flow is quiet, that is, where model predictions are consistent with both low and high-redshift supernova data, predicted magnitudes of several models were compared to the corrected B band magnitudes of the supernovae of the Pantheon+ sample.

When supernovae at redshifts below 0.035 are ignored, with

H_{0} = 73.4

km

\cdot

s

^{- 1} \cdot

Mpc⁻¹,

Λ

CDM predictions become consistent with Pantheon+ data. This is also the case when subsets of low-redshift supernovae roughly centered on the direction of the CMB dipole are considered, together with high-redshift ones, at least when CMB and peculiar velocities corrections are taken into account for the redshifts. These results seem robust, since they are also obtained with a simple, single-parameter tired-light model.

由普朗克合作组织参数化的ΛCDM 的震级预测与整个 Pantheon+ 样本的 Ia 超新星数据并不一致，即使为了考虑其值的不确定性而调整了哈勃常数。这可能是 Pantheon+ 样本中低红移超新星的数量比以前的此类样本有所增加的结果。为了在天空中找到哈勃流平静的方向，也就是模型预测与低红移和高红移超新星数据都一致的方向，我们将几个模型的预测星等与Pantheon+样本中超新星的校正B波段星等进行了比较。当忽略红移低于0.035的超新星时，H0=73.4 km⋅s-1⋅Mpc-1, ΛCDM的预测与Pantheon+的数据变得一致。如果把大致以 CMB 偶极子方向为中心的低红移超新星子集与高红移超新星子集放在一起考虑，至少在考虑到 CMB 和奇特速度对红移的修正时，情况也是如此。这些结果似乎很可靠，因为它们也是用简单的单参数累光模型得到的。

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引用次数: 0

A comprehensive study on the K2-type binary V1393 Tau in four-year observations 通过四年观测对K2型双星V1393 Tau的综合研究

IF 1.9 4区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

New Astronomy

Pub Date : 2024-11-13 DOI: 10.1016/j.newast.2024.102330

Ligang Yu , Shaung Wang , Michel Raúl , Liyun Zhang

We carried out a low resolution spectrum, the first ground-based multi-color light curves (LCs) analysis, and Transiting Exoplanet Survey Satellite (TESS) data analysis for the binary V1393 Tau. We determined its spectral type of K2V and updated an orbital period 0.24738715 days. By the Wilson-Devinney program, we solved ten sets of light curves. From the BVRcIc-band

L C_{2022.11}

, we obtained a mass ratio

q = 2.500 (3)

and a fill-out factor

f = 11.73 (6) %

, which implies that V1393 Tau is a W-type shallow-contact binary. We traced the spot migration and evolution through modeling light curves during the past four years. The spot’s size alternately becomes smaller or bigger, and its longitude intervenes between

λ = 82.3 9^{\circ}

in

L C_{S 70}

and

102.5 6^{\circ}

in

L C_{2022.10}

except for

L C_{S 32}

.

我们对双星V1393 Tau进行了低分辨率光谱、首次地基多色光曲线（LCs）分析和越轨系外行星巡天卫星（TESS）数据分析。我们确定其光谱类型为 K2V，并更新了其轨道周期为 0.24738715 天。通过威尔逊-德文尼程序，我们求解了十组光变曲线。通过BVRcIc波段LC2022.11，我们得到了质量比q=2.500(3)和填充因子f=11.73(6)%，这意味着V1393 Tau是一颗W型浅接触双星。我们通过建模光变曲线追踪了过去四年中光斑的迁移和演变过程。除LCS32外，光斑的大小交替变小或变大，其经度介于LCS70的λ=82.39∘和LC2022.10的102.56∘之间。

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引用次数: 0

The baryonic mass estimates of the Milky Way halo in the form of high-velocity clouds 高速云形式的银河系晕的重子质量估算

IF 1.9 4区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

New Astronomy

Pub Date : 2024-11-07 DOI: 10.1016/j.newast.2024.102328

Noraiz Tahir , Martín López-Corredoira , Francesco De Paolis

The halo of our Galaxy is populated with a significant number of high-velocity clouds (HVCs) moving with a speed up to 500 km/s. It is suggested that these HVCs might contain a non-negligible fraction of the missing baryons. The main aim of the current paper is to estimate the baryonic mass of the Milky Way halo in the form of HVCs in order to constrain a fraction of missing baryons in the form of these clouds. Such findings would give substantial help in the studying halo dynamics of our Galaxy.

We first estimate the HVCs distance. We consider the most recent and updated HVC catalog, namely the Galactic All Sky Survey (GASS), which, however, covers the southern sky declinations, south of

b \leq 6 0^{\circ}

. Following a model presented in the literature, we assume that most of the HVCs (not all of the HVCs in the Milky Way) were ejected from the Magellanic Clouds (MCls) which is at a distance of about 50 kpc. We assume that the HVCs have a temperature in the range of about

1 0^{2}

–

1 0^{4}

K, and are distributed in the Galactic halo as the Navarro–Frenk–White (NFW) profile. Since the GASS survey covers a small portion of the sky, we estimate the number of missing clouds by using Monte Carlo (MC) simulations. The next step will be to estimate the total mass of the Milky Way contained in the form of these HVCs. The total mass resulted to be

\sim (7 \pm 2) \times 1 0^{9} M_{⊙}

in the form of HVCs and compact high-velocity clouds (CHVCs).

我们银河系的光环中存在着大量的高速云（HVCs），其运动速度高达每秒 500 公里。有人认为，这些高速云可能包含了不可忽略的一部分缺失重子。本文的主要目的是估算以高速云形式存在的银河光环的重子质量，以确定以这些云的形式存在的部分缺失重子。我们首先估算了HVCs的距离。我们首先估算了HVCs的距离。我们考虑了最新的HVC星表，即银河系全天空巡天（GASS），但它只覆盖了南部天空的偏角，即b≤60∘以南。根据文献中提供的模型，我们假定大部分 HVC（不是银河系中的所有 HVC）都是从麦哲伦云（MCls）中喷出的，麦哲伦云的距离约为 50 kpc。我们假定HVC的温度范围约为102-104 K，并以纳瓦罗-弗伦克-怀特（NFW）剖面的形式分布在银河晕中。由于 GASS 勘测只覆盖了一小部分天空，我们通过蒙特卡罗（Monte Carlo，MC）模拟来估计缺失云的数量。下一步将是估算这些 HVC 所包含的银河系总质量。结果显示，HVC和紧密高速云的总质量为(7±2)×109M⊙。

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引用次数: 0

Modifications of SPH towards three-dimensional simulations of an icy moon with internal ocean 对 SPH 进行修改，以实现具有内部海洋的冰质卫星的三维模拟

IF 1.9 4区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

New Astronomy

Pub Date : 2024-11-02 DOI: 10.1016/j.newast.2024.102320

Keiya Murashima , Natsuki Hosono , Takayuki R. Saitoh , Takanori Sasaki

There are some traces of the existence of internal ocean in some icy moons, such as the vapor plumes of Europa and Enceladus. This implies a region of liquid water beneath the surface ice shell. Since liquid water would be essential for the origin of life, it is important to understand the development of these internal oceans, particularly their temperature distribution and evolution. The balance between tidal heating and radiative cooling is believed to sustain liquid water beneath an icy moon’s surface. We aim to simulate the tidal heating of an internal ocean in an icy moon using 3-dimensional numerical fluid calculations with the Smoothed Particle Hydrodynamics (SPH) method. We incorporated viscosity and thermal conduction terms into the governing equations of SPH. However, we encountered two issues while calculating rigid body rotation using SPH with a viscous term: (1) conventional viscosity formulations generated unphysical forces that hindered rotation, and (2) there was artificial internal energy partitioning within the layered structure, which was due to the standard SPH formulations. To address the first issue, we modified the viscosity formulation. For the second, we adopted Density Independent SPH (DISPH) developed in previous studies to improve behavior at discontinuous surfaces. Additionally, we implemented radiative cooling using an algorithm to define fluid surfaces via the particle method. We also introduced an equation of state accounting for phase transitions. With these modifications, we have refined the SPH method to encompass all necessary physical processes for simulating the evolution of icy moons with internal oceans.

一些冰卫星存在内部海洋的痕迹，如木卫二和土卫二的蒸汽羽流。这意味着在表面冰壳下有一个液态水区域。由于液态水是生命起源的必要条件，因此了解这些内部海洋的发展，特别是其温度分布和演化非常重要。潮汐加热和辐射冷却之间的平衡被认为是维持冰月表面下液态水的关键。我们的目标是利用平滑粒子流体力学（SPH）方法进行三维数值流体计算，模拟冰月内部海洋的潮汐加热。我们在 SPH 的控制方程中加入了粘度和热传导项。然而，在使用带有粘性项的 SPH 计算刚体旋转时，我们遇到了两个问题：(1) 传统的粘性公式会产生阻碍旋转的非物理力；(2) 由于标准的 SPH 公式，分层结构中存在人为的内部能量分配。为了解决第一个问题，我们修改了粘度公式。针对第二个问题，我们采用了之前研究中开发的密度独立 SPH（DISPH），以改善不连续表面的行为。此外，我们还通过粒子法定义流体表面的算法实现了辐射冷却。我们还引入了考虑相变的状态方程。通过这些修改，我们完善了 SPH 方法，使其包含了模拟具有内部海洋的冰卫星演变的所有必要物理过程。

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引用次数: 0

Photometric study for the short period contact binary V724 And 短周期接触双星 V724 And 的光度研究

IF 1.9 4区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

New Astronomy

Pub Date : 2024-10-31 DOI: 10.1016/j.newast.2024.102318

Bin Zhang , Yi-Dan Gao , Zhen Zhong , Bing Lv

We present the new light curve synthesis and orbital period change analysis of V724 And. We found that it is a W-subtype contact binary system with a mass ratio of q = 2.31 and a fill-out factor of f = 10.8%. The weak O’Connell effect can be explained by a cool star-spot on the more massive component star. By analyzing orbital period changes, it is found that the target displays a secular period decrease superimposed on a cyclic oscillation. The orbital period decreases at a rate of dp/dt = −4.13 × 10⁻⁸ d yr⁻¹, which can be explained by the mass transfer from the more massive one to the less massive component. The new discovery suggests that the semi-amplitude and period of the cyclic variation are A = 0.0013 d and P = 10.54 yr, respectively, which implies that V724 And is a possibly triple system. The minimum mass of the tertiary companion is estimated as M

_{3 m i n}

= 0.054 M

_{⊙}

, which plays an important role during the formation and evolution of the central binary system.

我们对 V724 And 进行了新的光曲线合成和轨道周期变化分析。我们发现它是一个 W 亚型接触双星系统，质量比为 q = 2.31，填充因子为 f = 10.8%。较弱的奥康纳尔效应可以用质量较大的组成恒星上的冷星点来解释。通过分析轨道周期的变化，可以发现该目标在周期性振荡的基础上又出现了周期性下降。轨道周期的下降速率为 dp/dt = -4.13 × 10-8 d yr-1，这可以用质量较大的成分向质量较小的成分的质量转移来解释。新发现表明，周期变化的半振幅和周期分别为 A = 0.0013 d 和 P = 10.54 yr，这意味着 V724 And 可能是一个三重系统。三级伴星的最小质量估计为 M3min = 0.054 M⊙，它在中心双星系统的形成和演化过程中起着重要作用。

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引用次数: 0

TESS and AAVSO observations of the eclipsing Z Cam-type cataclysmic variable V416 Dra TESS和美国天文观测台（AAVSO）对Z Cam型大灾变V416 Dra的蚀变观测

IF 1.9 4区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

New Astronomy

Pub Date : 2024-10-31 DOI: 10.1016/j.newast.2024.102319

Hongfei Yang, Zhongtao Han, Weiwei Na, Hushan Xu, Tingting Yang

We present a photometric analysis of the eclipsing Z Cam-type dwarf nova V416 Dra based on TESS and AAVSO data. The AAVSO light curve, spanning nearly 17 years, shows numerous outbursts recurring approximately every 20.2 and 38.6 days. We examined the amplitude vs. recurrence-time relation in V416 Dra, which appears to reflect the common characteristics of long outbursts in Z Cam stars. The TESS light curves revealed that V416 Dra is a shallow eclipse binary and shows some SU UMa-like superoutbursts, which may be related to the special structure of the accretion disk. The period-searching results show that there are the forest of peaks within the period range of 0.4–2.5 days, related to donor star’s activity. Moreover, we also find the presence of some typical quasi-periodic oscillation (QPO) signals with periods of 14–41 and 177–200 min, respectively. These results will help us locate the origin of the QPOs in V416 Dra accurately.

我们根据TESS和AAVSO的数据，对日食Z Cam型矮新星V416 Dra进行了光度分析。AAVSO的光变曲线跨越了近17年的时间，显示了大约每20.2天和38.6天发生一次的多次爆发。我们研究了V416 Dra的振幅与爆发时间的关系，这似乎反映了Z Cam星长爆发的共同特征。TESS光曲线显示，V416 Dra是一颗浅食双星，并出现了一些类似于SU UMa的超爆发，这可能与吸积盘的特殊结构有关。周期搜索结果表明，在0.4-2.5天的周期范围内存在着峰林，这与供体星的活动有关。此外，我们还发现了一些典型的准周期振荡（QPO）信号，周期分别为 14-41 分钟和 177-200 分钟。这些结果将有助于我们准确定位 V416 Dra 中 QPO 的起源。

引用次数: 0

Predicting the Physical Properties of Dark Matter Subhalos from Baryonic Parameters Using Machine Learning 利用机器学习从重子参数预测暗物质亚halos的物理特性

IF 1.9 4区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

New Astronomy

Pub Date : 2024-10-20 DOI: 10.1016/j.newast.2024.102316

Moonzarin Reza

Dark matter subhalos play an important role in galaxy formation and evolution. However, accurate prediction of dark matter properties remains a challenge of modern-day astronomy. In recent times, machine learning (ML) tools have shown promising results in solving numerous astrophysical problems. In this paper, we use data from the EAGLE simulations to determine the total mass and the half-mass radius of dark matter subhalos using structural properties of gas, star, black hole, and photometric features using gradient boosted decision trees (GBDT) and dense neural network. GBDT does not require data preprocessing, and results in better performance compared to the neural network. According to GBDT, the most important feature for subhalo radius and mass estimation is gas radius and black hole mass respectively. The all-features combined approach results in the highest test accuracy — Pearson’s correlation coefficient = 0.947 and 0.981, coefficient of determination = 0.898 and 0.962, normalized median absolute deviation = 0.111 and 0.114 for radius and mass respectively. We evaluate our model for masses and redshifts beyond its training range and find that GBDT demonstrates significantly better extrapolation capabilities than the neural network. We also test our model on simulations with different resolutions, and find that the discrepancies lie within 10% if the resolution is changed. This novel study incorporates the structural parameters of gas and black hole to determine the dark matter properties using a ML-based approach. The promising results of this study prove that ML tools can improve our current understanding of dark matter, and answer some of the basic cosmological questions.

暗物质亚halos 在星系形成和演化过程中发挥着重要作用。然而，准确预测暗物质特性仍然是现代天文学面临的一项挑战。近来，机器学习（ML）工具在解决众多天体物理问题方面取得了可喜的成果。在本文中，我们利用来自 EAGLE 模拟的数据，使用梯度提升决策树（GBDT）和密集神经网络，利用气体、恒星、黑洞的结构特性和光度特征来确定暗物质亚halos 的总质量和半质量半径。GBDT 不需要数据预处理，与神经网络相比性能更好。根据梯度提升决策树，估计子晕半径和质量的最重要特征分别是气体半径和黑洞质量。结合所有特征的方法获得了最高的测试精度--对于半径和质量，皮尔逊相关系数分别为 0.947 和 0.981，判定系数分别为 0.898 和 0.962，归一化中位绝对偏差分别为 0.111 和 0.114。我们对超出训练范围的质量和红移模型进行了评估，发现 GBDT 的外推能力明显优于神经网络。我们还在不同分辨率的模拟中测试了我们的模型，发现如果改变分辨率，差异在 10%以内。这项新颖的研究结合了气体和黑洞的结构参数，利用基于 ML 的方法确定了暗物质的属性。这项研究的良好结果证明，ML 工具可以改善我们目前对暗物质的理解，并回答一些基本的宇宙学问题。

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引用次数: 0

Slowly rotating charged Bardeen stellar structure 缓慢旋转的带电巴丁恒星结构

IF 1.9 4区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

New Astronomy

Pub Date : 2024-10-04 DOI: 10.1016/j.newast.2024.102314

Adnan Malik , Zoya Asghar , M. Farasat Shamir , Fatemah Mofarreh

This paper is devoted to investigating the dynamics of charged stellar structures with Bardeen exterior geometry. For this purpose, firstly a proposed metric coefficient is utilized, which is defined as

a = N {(1 + 2 h r^{2})}^{m / 2}

. Here,

h

and

N

are arbitrary constants determined from matching conditions and

m

is a positive integer. The pressure and density profiles are found to be positive and monotonically decreasing, with maximum values occurring at the center. Furthermore, the energy conditions and causality conditions are satisfied, and the adiabatic index falls within an acceptable range. The second part of the paper focuses on the dynamics of rotating stars. Numerical values for relevant parameters are assumed to obtain the masses and radii of stars within the desired range. Five different compact stars, namely,

V e l a X - 1

,

C e n X - 3

,

4 U 1820 - 30

,

4 U 1608 - 52

, and

P S R 1903 + 327

, are considered. The behavior of the moment of inertia of the sphere against the solar mass is investigated, revealing an increase in the moment of inertia with an increase in solar mass. Furthermore, the relationships of mass and energy density against the radius of the compact structure exhibit natural behavior, supporting the acceptability of the analysis. Overall, the study supports the existence of realistic charged compact structures with Bardeen exterior geometry.

本文致力于研究具有巴丁外部几何形状的带电恒星结构的动力学。这里，h 和 N 是根据匹配条件确定的任意常数，m 是正整数。研究发现，压力和密度曲线均为正值且单调递减，最大值出现在中心位置。此外，还满足了能量条件和因果关系条件，绝热指数也在可接受的范围内。论文的第二部分侧重于旋转恒星的动力学。假定了相关参数的数值，以便在所需范围内获得恒星的质量和半径。本文考虑了五颗不同的紧凑型恒星，即 VelaX-1、CenX-3、4U1820-30、4U1608-52 和 PSR1903+327。研究了球体惯性矩与太阳质量的关系，发现惯性矩随着太阳质量的增加而增加。此外，质量和能量密度与紧凑结构半径的关系表现出自然的行为，支持了分析的可接受性。总之，这项研究支持了具有巴丁外部几何形状的现实带电紧凑结构的存在。

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引用次数: 0