R. I. Gainutdinov, Yu. V. Baryshev, V. V. Sokolov
A review of modern VLTI observations of the orbital motion of closest stars to the relativistic compact object Sgr A* and its ability to test gravitation theories in the conditions of Post-Newtonian approximation. The observed orbital parameters, second order Doppler effect and gravitational redshift, measured for several S-stars, are compared with theoretical PN predictions.
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Parametrized Post-Newtonian (PPN) equations of motion for several S-stars nearest to the Galactic Center compact relativistic object SgrA* are considered. The effect of the orbital periods difference between Newtonian and Post-Newtonian cases is taken into account. The best fit PN orbit of S2 has a period which is 16 days longer than Newtonian one. The PPN parameters $β_\text{PPN}$ and $γ_\text{PPN}$ are measured. Bayesian sampling is used to fit the trajectories of the PPN laws of motion. Posterior estimates of $β_\text{PPN}$ and $γ_\text{PPN}$ are $0.97^{+0.42}_{-0.65}$ and $0.81^{+0.46}_{-0…
Long-term classical and general relativistic effects on the radial velocities of the stars orbiting Sgr A*
本文解析地计算了一颗典型的S星在几种动力学效应作用下，绕银河系中心（GC）的超大质量黑洞（SBH）运行时径向速度v_r的累积时间变化，即在一个轨道旋转上的平均值。它们是SBH的广义相对论引力电磁场（GEM）、四极质量矩Q2和SBH周围弥漫的暗物质分布。它们都引起非零的长期径向加速度与轨道的偏心率e成比例。以S2星为例，它沿着一个高偏心率（e = 0.8831）的椭圆轨道运行，周期为Pb = 15.9 yr，我们数值计算了它的径向加速度的大小。
Testing the Spacetime Geometry of Sgr A* with the Relativistic Orbit of S2 star
通过S2星的轨道数据，研究Sgr A*周围不同时空几何模型的相对论检验，发现多个模型在现有数据下无法区分，同时利用AIC和BIC准则评估不同模型性能，并约束非Schwarzschild时空中的电荷类参数。
The star S0-2, orbiting the Galactic central massive black hole candidate Sgr A*, passed its pericenter in May 2018. This event is the first chance to detect the general relativistic (GR) effect of a massive black hole, free from non-gravitational physics. The observable GR evidence in the event is the difference between the GR redshift and the Newtonian redshift of photons coming from S0-2. Within the present observational precision, the 1st post-Newtonian (1PN) GR evidence is detectable. In this paper, we give a theoretical analysis of the time evolution of the 1PN GR evidence, under a presu…
We observe the S-cluster star S62 on its Keplerian orbit around the supermassive black hole in the center of our galaxy, SgrA*. The orbital time period of S62 around SgrA* is 9.9 years. We derive its mass to be around 2 M_solar which is consistent with other members of the S-cluster. From the Lucy-Richardson deconvolved images, we determine a K-band magnitude of 16.1 mag. We observe almost two complete orbits of the star with two different and independent telescopes and three different instruments. The close distance of S62 to SgrA* at its periapse of around 2 mas results in a gravitational pe…
Clocks around Sgr A*
银河系中心附近的S星和任何可能在类似轨道上的恒星都可以统一地建模为绕黑洞运行的时钟，因此是相对论效应的潜在探测器，包括黑洞自旋。许多S星的高离心率意味着相对论效应在近心点附近达到强烈的峰值;例如，轨道进动不是一个平滑的效应，而是在近心点附近几乎是一个踢。我们认为，当分析红移或脉冲到达数据来测量相对论效应时，近心点周围的浓度将是一个优势，因为累积的岁差将被银河系中心区域其他质量的牛顿扰动所淹没。小波分解可能是从牛顿微扰中解开相对论效应的一种方法。假设一个合理的模型，牛顿扰动的S2，相对论似乎是最强的，在近心点周围的两年时间间隔，在小波模式的时间尺度约6个月。
Probing dense environments around Sgr A* with S-stars dynamics
通过计算S2星轨道的进动，研究Sgr A*周围环境的特性，扩展GRAVITY约束，并探讨boson云对星轨衰减的影响。
Shadows around Sgr A* and M87* as a tool to test gravity theories
本文基于Randall-Sundrum理论中带潮汐荷的Reissner-Nordström黑洞解，推导了阴影大小的解析表达式，并探讨了利用EHT对M87和银河系中心的观测数据来评估替代引力理论参数及潮汐荷的可能性。
Jet-lag in Sgr A*: What size and timing measurements tell us about the central black hole in the Milky Way
银河系中心的黑洞，Sgr A*，是处于非常低的活动水平的星系核的原型。它的无线电通过亚毫米波发射已知来自接近事件视界的区域，然而，发射源仍在争论中。一个成功的理论解释的排放是基于一个相对论性喷流模型缩小从强大的类星体。我们想测试这个建立的喷流模型的预测能力对新的可用测量波长依赖的时间滞后和Sgr A* 的尺寸-波长结构。利用所有可用的封闭振幅VLBI数据从不同的群体，我们再次推导出的固有波长依赖的大小的Sgr A*。这使我们能够计算出无线电耀斑的预期频率依赖的时间滞后，假设一系列的流入和流出速度。此外，我们计算了在以前发表的压力驱动射流模型中预期的时间滞后。然后将预测的滞后与22、43和350 GHz的无线电监测观测结果进行比较。时间滞后和尺寸测量的组合意味着一个温和的相对论外流与整体外流速度的伽玛 * β ~ 0.5-2。新测得的时间滞后再现射流模型没有任何重大的微调。结果进一步加强了Sgr A* 中厘米至毫米波射电辐射来自轻度相对论性喷流样外流的情况。射电时间滞后和VLBI闭合振幅测量的组合是评估Sgr A* 中的流速和方向的一种强有力的新工具。未来在一定波长范围内的VLBI和时间滞后测量将揭示更多关于Sgr A* 的信息，例如喷嘴的存在，并首次测量发射点附近相对论性喷流的详细速度结构。
Can we see pulsars around Sgr A*? - The latest searches with the Effelsberg telescope
相对论双星系统中的射电望远镜是研究大质量致密天体周围弯曲时空的独特工具。发现一颗脉冲星紧密地围绕着银河系中心的超大质量黑洞Sgr A* 旋转，这将为引力物理学提供一个极好的试验台。到目前为止，在Sgr A* 的几弧分钟内没有发现任何射电脉冲星的原因是一个主要因素：Sgr A* 周围中央100 pc的星际介质电离成分的不均匀性引起的无线电波的极端散射。导致脉冲时间展宽的散射只能通过在更高频率下观察来减轻。在这里，我们描述了最近的搜索银河系中心区域进行的频率为18.95 GHz的Effelsberg射电望远镜。
General Relativistic effects and the NIR variability of Sgr A* II: A systematic approach to temporal asymmetry
本文利用三阶结构函数系统研究Sgr A*近红外光变的时间不对称性，发现其上升与衰减时标几乎对称，并归因于多普勒增强主导而非引力透镜，同时通过相对论性半物理模型约束倾角小于45度。
The ongoing monitoring of the Galactic center and Sgr A*, the central supermassive black hole, produces surprising and unexpected findings. This goes hand in hand with the technical evolution of ground- and space-based telescopes and instruments, but also with the progression of image filter techniques such as the Lucy Richardson algorithm. As we continue to trace the members of the S cluster close to Sgr A* on their expected trajectory around the supermassive black hole, we present the finding of a new stellar source, which we call S4716. The newly found star orbits SgrA* in about 4.0 yr and …
After the amazing discoveries by the GRAVITY collaboration in the last few years on the star S2 orbiting the black hole Sgr A* in the center of the Milky Way, we present a detailed investigation of the impact of gravitational lensing on the reconstruction of stellar orbits around this massive black hole. We evaluate the lensing astrometric effects on the stars S2, S38 and S55 and how these systematically affect the derived orbital parameters. The effect is below current uncertainties, but not negligible. With the addition of more observations on these stars, it will be possible to let the astr…
Estimating the parameters of the Sgr A* black hole
测量银河系中心周围的相对论效应可能会在不久的将来强烈约束可能存在于银河系中心（Sgr A*）的超大质量黑洞的参数。此外，作为这些测量的副产品，还可能严格限制最里面的星团和银河系中心周围的暗物质团的质量密度分布参数。
Hypervelocity Planets and Transits Around Hypervelocity Stars
银河系中心的大质量黑洞SgrA * 对双星系统的破坏可以导致SgrA * 周围的一颗恒星被捕获，并将其伴星作为超高速恒星（HVS）弹射出去。我们认为这些恒星可能有行星，并研究这些行星的动力学。利用直接的$N$体积分程序，我们模拟了大量围绕SgrA * 的不同双星轨道。对于某些轨道参数，行星以高速喷射。在另一些情况下，一颗HVS被一颗或多颗行星围绕着它运行，在这种情况下，当行星经过恒星表面时，就有可能被观测到。一颗行星也可能与它的宿主恒星相撞。在这种情况下，恒星的大气层将富含金属。在其他情况下，一颗行星被SgrA * 潮汐干扰，导致明亮的耀斑。
Sgr A East is the supernova remnant closest to the centre of the Milky Way. Its age has been estimated to be either very young, around 1-2 kyr, or about 10 kyr, and its exact origin remains unclear. We aspire to create a simple model of a supernova explosion that reproduces the shape, size, and location of Sgr A East. Using a simplified hydrodynamical code, we simulated the evolution of a supernova remnant in the medium around the Galactic centre. The latter consists of a nearby massive molecular cloud with which Sgr A East is known to be interacting and a wind from the nuclear star cluster. O…
Turbulence is a crucial factor in many models of planet formation, but it has only been directly constrained among a small number of planet forming disks. Building on the upper limits on turbulence placed in disks around HD 163296 and TW Hya, we present ALMA CO J=2-1 line observations at $\sim0.3"$ (20-50 au) resolution and 80 ms$^{-1}$ channel spacing of the disks around DM Tau, MWC 480, and V4046 Sgr. Using parametric models of disk structure, we robustly detect non-thermal gas motions around DM Tau of between 0.25 c$_s$ and 0.33 c$_s$, with the range dominated by systematic effects, making …
We present a study of diffuse extended ionised gas toward three clouds located in the Galactic Centre (GC). One line of sight (LOS) is toward the 20 km s$^{-1}$ cloud (LOS$-$0.11) in the Sgr A region, another LOS is toward the 50 km s$^{-1}$ cloud (LOS$-$0.02), also in Sgr A, while the third is toward the Sgr B2 cloud (LOS+0.693). The emission from the ionised gas is detected from H$nα$ and H$mβ$ radio recombination lines (RRLs). He$nα$ and He$mβ$ RRL emission is detected with the same $n$ and $m$ as those from the hydrogen RRLs only toward LOS+0.693. RRLs probe gas with positive and negative …
Surviving the hole I: Spatially resolved chemistry around Sgr A*
在银河系中心的超大质量黑洞Sgr A* 周围几个中央秒差距内的星际区域由许多重叠的分子结构组成，这些分子结构受到银河系中最恶劣的物理环境之一的影响。本文给出了银河系中心区~ 4pc处1.3mm处CN、~（13）CN、H_2CO、SiO、c-C_3 H_2和HC_3N辐射的高分辨率（4“× 3”~ 0.16x0.11pc）干涉观测结果。在不同分子的分布中观察到强烈的差异。抗紫外线物种CN，唯一的物种跟踪所有以前确定的环核盘（CND）结构，主要集中在光学厚团块在旋转丝周围的Sgr A*。H2 CO排放跟踪壳状结构，我们解释为扩张的Sgr A东对50公里/秒和20公里/秒的巨大分子云（GMC）。计算了CND区大部分地区的~（12）C/~（13）C ~（15-45）同位素比值。由SiO和HC_3 N示踪的致密分子物质位于CND南部。在该区域观察到的c-C3 H2/HC 3 N比比银河系PDR低一个数量级以上。向中心区域仅检测到CN的吸收。除了已知的窄视线反射外，还观察到了90 km/s宽的光学厚光谱特征。我们发现了更宽（>100 km/s）吸收特征的证据。大约70-75%的气体质量，集中在27%的致密分子团中，与旋转结构有关，并显示出与微型螺旋结构中的每个电离气体弧有关的证据。化学分化已被证明是一个强大的工具，解开许多重叠的分子组分在这个拥挤和严重模糊的区域。
We present high-pass filtered NACO and SINFONI images of the newly discovered stars S4711-S4715 between 2004 and 2016. Our deep H+K-band (SINFONI) and K-band (NACO) data show the S-cluster star S4711 on a highly eccentric trajectory around Sgr~A* with an orbital period of 7.6 years and a periapse distance of 144 AU to the super massive black hole (SMBH). S4711 is hereby the star with the shortest orbital period and the smallest mean distance to the SMBH during its orbit to date. The used high-pass filtered images are based on co-added data sets to improve the signal to noise. The spectroscopic…
Constraining intermediate-mass black holes from the stellar disc of SgrA*
本文结合矢量共振弛豫的动力学预言与SgrA*恒星盘观测，定量研究中等质量黑洞群体对恒星盘存活性的影响，从而约束SgrA*周围未观测到的恒星团。
The Event Horizon Telescope (EHT) will soon provide the first high-resolution images of the Galactic Centre supermassive black hole (SMBH) candidate Sagittarius A* (Sgr A*), enabling us to probe gravity in the strong-field regime. Besides studying the accretion process in extreme environments, the obtained data and reconstructed images could be used to investigate the underlying spacetime structure. In its current configuration, the EHT is able to distinguish between a rotating Kerr black hole and a horizon-less object like a boson star. Future developments can increase the ability of the EHT …
ALMA and VLA measurements of frequency-dependent time lags in Sagittarius A*: evidence for a relativistic outflow
对银河系中心超大质量黑洞射电源人马座A*（Sgr A*）的射电和毫米波观测表明，它表现为部分自吸收的同步辐射源。测量的Sgr A* 的大小表明，毫米波长的发射来自一个小的区域，由内部吸积流和可能的准直流出。对Sgr A* 的现有观测揭示了在43 GHz和22 GHz处的光变曲线之间的时滞，这与快速膨胀的等离子体流一致，并支持存在来自吸积黑洞环境的准直流出物。在这里，我们希望在一个很宽的频率范围内测量同步的频率依赖的时间滞后的光变曲线的Sgr A* 约束的方向和速度的无线电发射等离子体附近的黑洞。Sgr A* 的光变曲线于2012年5月使用ALMA在100 GHz下使用VLA在48、39、37、27、25.5和19 GHz下拍摄。由于高度限制和两个观测站之间的经度差异，光变曲线的可用重叠时间约为4小时。虽然Sgr A* 处于相对平静的阶段，但ALMA和VLA的高灵敏度使我们能够检测并拟合观测到的小耀斑的最大值，其中通量密度变化约10%。通量密度最大值在频率从100 GHz到19 GHz的拟合时间，以及互相关分析，揭示了一个简单的频率依赖的时间滞后关系，在较高的频率导致那些在较低的频率。考虑到观测到的Sgr A* 的大小-频率关系，这些时间滞后表明了适度的相对论性（较低的估计值：双侧0.5c，单侧0.77c）准直流出。
A Parsec-scale Circumstellar Shell Around VX Sgr: Mass Loss and RSG/TŻO Nature
研究发现VX Sgr周围存在0.59秒差距的弧形星周壳层，排除其为弓激波产物，通过运动学年龄排除超AGB模型，估算质量损失率并探讨其超新星抛射物与星周物质的相互作用，以明确VX Sgr的RSG/TŻO性质。
The Submillimeter Bump in Sgr A* from Relativistic MHD Simulations
最近对银河系中心黑洞的高分辨率观测允许与吸积盘模拟进行直接比较。我们比较两个温度同步辐射模型从三维，广义相对论磁流体动力学模拟毫米观测的Sgr A*。适合非常长的基线干涉和光谱指数测量不利于单色面对黑洞阴影模型从我们以前的工作。倾斜角\le 20度排除为3 σ。在90%的置信度下，我们估计了该黑洞的倾角和位置角，吸积流的电子温度和吸积速率分别为i=50+35-15度，θ =-23+97-22度，T_e=（5.4 +/- 3.0）× 10 ^10 K和Mdot=（5+15-2）× 10 ^-9 M_sun / yr。黑洞阴影在所有最佳拟合模型中都是清晰的，并且可以通过在智利和加利福尼亚州、亚利桑那州或墨西哥之间的基线上的观测在1.3毫米或.87毫米处通过直接采样可见度振幅或使用闭合相位信息来检测。毫米耀斑的行为与观察一致，是目前在所有可行的模型，是由磁湍流的吸积流的内半径。在光学薄频率的变化是强烈相关的吸积率。模拟结果给出了1.3mm发射区的普遍图象，它是吸积流内径中靠近中平面的一个小区域，大致等温，ν/ν c ~ 1-20，其中ν c是热同步辐射的临界频率。
The orbit of the star S2 around SgrA* from VLT and Keck data
最近的两篇论文（Ghez et al. 2008，Gillessen et al. 2009）利用恒星轨道估算了银河系中心大质量黑洞的质量和距离。这两个天体测量数据集是独立的，并产生了一致的结果，即使测量的位置不匹配时，简单地重叠的两个集。在这封信中，我们表明，这两套可以带来很好的协议时，允许一个小的偏移量的定义的参考系的两个数据集。所需的参考系原点坐标和速度偏移与Ghez等人（2008年）给出的不确定性一致。如此组合的数据集允许适度改善Sgr A* 的质量和到Sgr A* 的距离的统计误差，但是这些数字的总体精度由系统误差和参考系的长期校准支配。我们得到R 0 = 8.28 +- 0.15（stat）+- 0.29（sys）kpc和M（MBH）= 4.30 +- 0.20（stat）+- 0.30（sys）x 10^6 Msun作为多星拟合的最佳估计值。
Parameter study for hot spot trajectories around Sgr$A*$
本研究开发了广义相对论辐射转移代码，通过参数研究 Sgr$A*$ 附近热点运动，发现不同热点轨迹模型对轨道频率的偏好，并指出远观测者难以区分 Schwarzschild 与 Kerr 黑洞及不同观测角度的正面轨道。
Empirically determining the averaged variations of the orbital parameters of the stars orbiting the Supermassive Black Hole (SBH) hosted by the Galactic Centre (GC) in Sgr A* is, in principle, a valuable tool to put on the test the General Theory of Relativity (GTR), in regimes far stronger than those tested so far, and certain key predictions of it like the no-hair theorems. We analytically work out the long-term variations of all the six osculating Keplerian orbital elements of a test particle orbiting a non-spherical, rotating body with quadrupole moment Q_2 and angular momentum S for a gen…
An unusual object, G2, had its pericenter passage around Sgr A*, the $4\times10^6$ M$_\odot$ supermassive black hole in the Galactic Centre, in Summer 2014. Several research teams have reported evidence that following G2's pericenter encounter the rate of Sgr A*'s bright X-ray flares increased significantly. Our analysis carefully treats varying flux contamination from a nearby magnetic neutron star and is free from complications induced by using data from multiple X-ray observatories with different spatial resolutions. We test the scenario of an increased bright X-ray flaring rate using a mas…
We trace several dusty infrared sources on their orbit around the supermassive black hole (SMBH) SgrA* in the center of our galaxy. We give an overview of known and unknown sources in the direct vicinity of our SMBH in a radius of around 0.04pc. For that, we are using NACO (K- and L'-band) and SINFONI (H+K-band) data (VLT, Chile/Paranal) between 2002 and 2018. Our spectroscopic analysis reveals a Doppler-shifted line emission of Br_gamma and HeI. Additionally, we report the detection of [FeIII] lines that are found exclusively in the investigated dusty sources west of SgrA*. We speculate, that…
Flaring up of the Compact Cloud G2 during the Close Encounter with Sgr A*
一个致密的气体云G2预计将到达其围绕我们银河系人马座A*（Sgr A*）的超大质量黑洞（SMBH）轨道的近心。这一事件将给我们一个难得的机会来观察SMBH和周围气体的相互作用。我们报告的结果的全三维模拟G2的演变过程中的第一近心通过。强引潮力使云团沿轨道伸展，并在垂直方向上强烈压缩，导致云团升温和燃烧。热光度将达到最大值$\sim100 L_{\odot}$。这种耀斑应该很容易在近红外线观察到。
Atacama Large Millimeter/Submillimeter Array (ALMA) is promising to be a powerful tool for precision astrometry of the area around Sagittarius A$^\ast$ (Sgr A$^\ast$) because it has the high angular resolution, high sensitivity, and wide field of view. We have observed the area including the Nuclear Star Cluster at 230 GHz with ALMA in October 2017. The angular resolution is ~0.03". We determined the relative positions to Sgr A$^\ast$ of 65 compact objects in the area with the accuracy of 0.001". We also analyzed the similar ALMA archival data obtained in June 2019 and determined the 64 relati…
In a recent paper (Leibowitz 2017) I have shown that the 39 large X-ray flares of Sgr A* that were recorded by Chandra observatory in the year 2012, are concentrated preferably around tick marks of an equi-distance grid on the time axis. The period of this grid as found in L1 is 0.1033 days. In this work I show that the effect can be found among all the large X-ray flares recoded by Chandra and XMM-Newton along 15 years. The midpoints of all the 71 large flares recorded between the years 2000 and 2014 are also tightly grouped around tick marks of a grid with this period, or more likely, 0.1032…
Radio Synchrotron Emission from a Bow Shock around the Gas Cloud G2 Heading toward the Galactic Center
最近，科学家们发现一个致密的电离气体云正直接向银河系中心的超大质量黑洞Sgr A* 移动。2013年6月，在其高偏心轨道的近心处，该云将距离黑洞约3100史瓦西半径，并将以v_p ~ 5400 km/s的速度以超音速方式穿过周围的热气体。弓形激波很可能在云的前面形成，并可能将电子加速到相对论能量。我们估计通过粒子在细胞模拟的能量分布的加速电子，并表明，从这些电子的非热同步辐射可能超过静止的无线电发射从Sgr A* 的几个因素。增强的无线电发射应该在近心通过的时间和随后的几个月内在GHz和更高的频率上被检测到。弓形激波发射预计将从Sgr A* 的静态射电发射中位移约33质量。干涉测量观测可以分辨Sgr A* 射电图像中波长小于6厘米的潜在变化。
The chemical differentiation of seven COMs in the extended region around Sgr B2 has been observed: CH$_2$OHCHO, CH$_3$OCHO, t-HCOOH, C$_2$H$_5$OH, and CH$_3$NH$_2$ were detected both in the extended region and near the hot cores Sgr B2(N) and Sgr B2(M), while CH$_3$OCH$_3$ and C$_2$H$_5$CN were only detected near the hot cores. The density and temperature in the extended region are relatively low. Different desorption mechanisms have been proposed to explain the observed COMs in cold regions but fail to explain the deficiency of CH$_3$OCH$_3$ and C$_2$H$_5$CN. We explored under what physical c…
No Microwave Flare of Sagittarius A* around the G2 Periastron Passing
为了探讨G2云的临近对大气的影响，我们利用日本VLBI观测网的子阵对2013年2月至2014年8月22 GHz的Sgr A* 进行了观测。观测期包括预期的近星点日期。观察期为283天。在整个观测期间，我们没有观察到Sgr A* 的显著微波增强。这一时期的平均通量密度为$S=1.23+/-0.33$ Jy。该平均值与22 GHz时通常观察到的Sgr A* 通量密度范围一致。
In an intensive observational campaign in the 9 month duration of Chandra X-ray Visionary Project that was conducted in the year 2012, 39 large X-ray flares of Sgr A* were recorded. An analysis of the times of the observed flares reveals that the 39 flares are separated in time by intervals that are grouped around integer numbers times 0.10333 days. This time interval is thus the period of a uniform grid of equally spaced points on the time axis. The grouping of the flares around tic marks of this grid is derived from the data with at least a 3.2 σ level of statistical significance. No signal …
Spectral imaging of the Central Molecular Zone in multiple 7-mm molecular lines
我们已经在银河系中心周围的中央分子区（CMZ）中成像了24条谱线，范围为42至50 GHz。谱线包括CS、CH 3OH、HC 3 N、SiO、HNCO、HOCO+、NH 2CHO、OCS、HCS+、CCS、C34 S、13 CS、29 SiO、H13 CCCN、HCC 13 CN和HC 5 N分子的发射，以及三条氢复合谱线。覆盖的区域是银河经度-0.7至1.8度。以及纬度-0.3至0.2度，包括Sgr A、Sgr B 2、Sgr C和G1.6-0.025附近的亮核。这项工作使用了澳大利亚的22米Mopra射电望远镜，获得了~ 1.8公里/秒的光谱分辨率和~ 65角秒的空间分辨率。我们提出了这项研究的峰值图像，并进行了主成分分析的综合发射最亮的10条线，研究线分布的相似性和差异。我们研究了集成线强度和线比率在选定的光圈周围的明亮的核心，以及完整的映射区域的CMZ。我们比较这些7毫米线在3毫米波段的相应的线，为5个分子，研究的激发。在CMZ上，3 mm与7 mm的线比率存在变化，在Sgr B2和Sgr A周围的中心具有相对较高的比率。我们发现这些谱线是亚热激发的，并且通过RADEX建模发现非LTE条件适用，密度为10^4 cm^{-3}量级。
The Galactic Center IRS 13E cluster is a very intriguing IR object located at $\sim0.13$ pc from Sagittarius A$^\ast$ (Sgr A$^\ast$) in projection distance. There are both arguments for and against the hypothesis that a dark mass like an intermediate mass black hole (IMBH) exists in the cluster. Recently we have detected the rotating ionized gas ring around IRS 13E3, which belongs to the cluster, in the H30$α$ recombination line using ALMA. The enclosed mass is derived to be $M_{\mathrm{encl.}}\simeq2\times10^4$ $M_\odot$, which agrees with an IMBH and is barely less than the astrometric upper…
Constraining the Cosmological Constant from Stellar Orbits Around Sgr A* Using Physics-Informed Neural Networks
本文利用物理信息神经网络分析Sgr A*周围S2等恒星的轨道进动，分离宇宙学常数Λ的贡献，得到比先前方法紧约两个数量级的上限Λ≤5.67×10^-40 m^-2，展示了PINN从稀疏天文数据中提取物理约束的潜力。
HOCN and HNCO abundance ratio in molecular gas can tell us the information of their formation mechanism. We performed high-sensitivity mapping observations of HOCN, HNCO, and HNC$^{18}$O lines around Sagittarius B2 (Sgr B2) with IRAM 30m telescope at 3-mm wavelength. HNCO 4$_{04}$-3$_{03}$ and HOCN 4$_{04}$-3$_{03}$ are used to obtain the abundance ratio of HNCO to HOCN. The ratio of HNCO 4$_{04}$-3$_{03}$ to HNC$^{18}$O 4$_{04}$-3$_{03}$ is used to calculate the optical depth of HNCO 4$_{04}$-3$_{03}$. The abundance ratio of HOCN and HNCO is observed to range from 0.4% to 0.7% toward most pos…
We report sub-arcsecond ALMA observations between 272 - 375 GHz towards Sgr A*'s Circumnuclear disk (CND). Our data comprises 8 individual pointings, with significant SiO (8(7) - 7(6)) and SO (7 - 6) emission detected towards 98 positions within these pointings. Additionally, we identify H2CS (9(1,9) - 8(1,8)), OCS (25 - 24) and CH3OH (2(1,1) - 2(0,2)) towards a smaller subset of positions. By using the observed peak line flux density together with a Bayesian Inference technique informed by radiative transfer models, we systematically recover the physical gas conditions towards each of these p…
Kozai-driven mass loss of the circumbinary disk in D9 in orbit around the supermassive black hole Sgr A*
研究Sgr A*与D9双星相互作用下circumbinary盘的演化，发现盘质量损失受von Zeipel-Lidov-Kozai机制驱动，盘质量每周期损失约7%，预计盘将在约4Myr后只剩1%质量。
Because of its particular orientation around the Galaxy - i.e., in a plane nearly perpendicular to the Galactic plane and containing both the Sun and Galactic center - the Sagittarius (Sgr) stream provides a powerful means by which to measure the solar reflex velocity, and thereby infer the velocity of the Local Standard of Rest (LSR), in a way that is independent of assumptions about the solar Galactocentric distance. Moreover, the solar reflex velocity with respect to the stream is projected almost entirely into the proper motion component of Sgr stream stars perpendicular to the Sgr plane, …
The S2 star as a probe of the accretion disk of Sgr A*
银河系中心的大质量黑洞和其他高度亚爱丁顿吸积物周围的吸积过程如何进行，仍然知之甚少。银河系中心S2恒星的轨道穿过大质量黑洞的吸积盘，任何来自这种相互作用的观测信号都可以用作吸积探测器。由于其早期的恒星类型，S2预计将拥有相当强大的风。我们在这里表明，吸积盘的冲压压力冲击相当接近恒星的恒星风。冲击流体达到~ 1 keV的温度，并通过光学薄的热韧致辐射有效地冷却。来自激波的辐射峰值出现在恒星近心点附近，其光度可能与从Sgr A* 探测到的静态发射相当。对激波辐射的探测可以将吸积盘的密度限制在距离黑洞几千个引力半径的地方。
We performed high-sensitivity mapping observations of several complex organic molecules around Sagittarius B2 with ARO 12m telescope at 3-mm wavelength. Based on their spatial distribution, molecules can be classified as either "extended" that detected not only in Sgr B2(N) and Sgr B2(M), or "compact" that only detected toward or near to Sgr B2(N) and Sgr B2(M). The "extended" molecules including glycolaldehyde (CH2OHCHO), methyl formate (CH3OCHO), formic acid (t-HCOOH), ethanol (C2H5OH) and methyl amine (CH3NH2), while the "compact" molecules including dimethyl ether (CH3OCH3), ethyl cyanide …
Prospects for Probing the Spacetime of Sgr A* with Pulsars
在围绕Sgr A* 的紧凑轨道上发现射电双星将允许对超大质量黑洞的时空进行前所未有的详细调查。本文表明，脉冲星计时，包括一个单一的脉冲星，有可能提供新的测试广义相对论，特别是它的宇宙审查猜想和无毛定理旋转黑洞。这些实验可以通过100微秒精度的定时观测来进行，对于频率高于15 GHz的正常脉冲星，可以使用平方公里阵列来实现。基于标准的脉冲星计时技术，我们开发了一种方法，可以确定的质量，自旋和四极矩的Sgr A*，并提供了一致的协方差分析的测量误差。此外，我们测试这种方法在详细的模拟数据模拟。似乎只有在轨道周期低于0.3年时，才有可能出现可忽略不计的外部扰动。对于这样的轨道，如果Sgr A* 在快速旋转，我们预计在5年内会有约10^-3的标架拖曳检验和约10^-2的无毛定理检验。我们的方法也能够识别由Sgr A* 周围的分布质量引起的扰动，从而在这些重力测试中提供高置信度。我们的分析不受我们对银河系中心R 0距离的不确定性的影响。将脉冲星计时与恒星轨道的天体测量结果相结合，将大大提高R 0的测量精度。
After becoming ionized, low-density astrophysical plasmas will begin a process of slow recombination. Models for this still have significant uncertainties. The recombination cannot normally be observed in isolation, because the ionization follows the evolutionary time scale of the ionizing source. Laboratory experiments are unable to reach the appropriate conditions because of the required very long time scales. The extended nebula around the very late helium flash (VLTP) star V4334 Sgr provides a unique laboratory for this kind of study. The sudden loss of the ionizing UV radiation after the …
We present an analysis of the evolution of circumstellar dust and molecules in the environment of the very late thermal pulse object V4334 Sgr (Sakurai's Object) over a $\sim20$-year period, drawing on ground-, airborne- and space-based infrared photometry and spectroscopy. The dust emission, which started in 1997, resembles a blackbody that cooled from $\sim1200$K in 1998 August to $\sim180$K in 2016 July. The dust mass, assuming amorphous carbon, was $\sim5\times10^{-10}$M$_\odot$ in 1998 August, and we estimate that the total dust mass was $\sim2\times10^{-5}$M$_\odot$ by $\sim2016$. The ap…
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