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arXiv 2501.03409astro-ph.HEastro-ph.GA
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毫秒脉冲星磁制动经验建模以测量局域暗物质密度及伴生卫星星系的影响

Empirical Modeling of Magnetic Braking in Millisecond Pulsars to Measure the Local Dark Matter Density and Effects of Orbiting Satellite Galaxies

Thomas Donlon, Sukanya Chakrabarti, Sophia Vanderwaal, Lawrence M. Widrow, Scott Ransom, Enrico Ramirez-Ruiz

AI总结:

提出仅用自转周期及其导数估算毫秒脉冲星加速度的新方法,将测量样本翻倍至53颗,首次实现>3σ局域暗物质密度直接测量,并解释加速度不对称性。

摘要:

我们提出了一种新颖的方法,仅利用毫秒脉冲星(MSP)的自转周期及其时间导数即可估算其加速度。对于我们的双星毫秒脉冲星样本,我们展示了可以仅依赖观测量获得磁制动项的经验校准。我们发现,这种磁制动模型仅对表面磁场强度较小(<3×10^8 G)且特征年龄较大(>5 Gyr)的毫秒脉冲星有效。利用该方法,我们能够将具有视线加速度测量的脉冲星数量有效翻倍,从27颗增加到53颗。这一扩充的数据集带来了对银道面中平面总密度的更新测量,我们测得ρ₀ = 0.108 ± 0.008(统计误差)± 0.011(系统误差)M☉/pc³,以及首次通过直接加速度测量得到的>3σ局域暗物质密度测量值,我们计算得ρ₀,DM = 0.0098 ± 0.0025(统计误差)± 0.0003(系统误差)M☉/pc³(0.37 ± 0.10 GeV/cm³)。这一更新的ρ₀,DM值与基于运动学估计的文献值吻合良好。脉冲星加速度在银道面上方和下方非常不对称;我们表明,这种不对称的形状和大小可以在很大程度上由银盘恒星计数的南北不对称以及大麦哲伦云导致的银盘和银晕质心偏移来解释。

英文摘要:

We present a novel method that enables us to estimate the acceleration of individual millisecond pulsars (MSPs) using only their spin period and its time derivative. For our binary MSP sample, we show that one can obtain an empirical calibration of the magnetic braking term that relies only on observed quantities. We find that such a model for magnetic braking is only valid for MSPs with small surface magnetic field strengths ($<3\times10^8$ G) and large characteristic ages ($>$ 5 Gyr). With this method we are able to effectively double the number of pulsars with line-of-sight acceleration measurements, from 27 to 53 sources. This expanded dataset leads to an updated measurement of the total density in the midplane, which we find to be $ρ_0$ = 0.108 $\pm$ 0.008 \textit{stat}. $\pm$ 0.011 \textit{sys} M$_\odot$/pc$^3$, and the first $>3σ$ measurement of the local dark matter density from direct acceleration measurements, which we calculate to be $ρ_{0,\mathrm{DM}}$ = 0.0098 $\pm$ 0.0025 \textit{stat.} $\pm$ 0.0003 \textit{sys}. M$_\odot$/pc$^3$ (0.37 $\pm$ 0.10 GeV/cm$^3$). This updated value for $ρ_{0,\mathrm{DM}}$ is in good agreement with literature values derived from kinematic estimates. The pulsar accelerations are very asymmetric above and below the disk; we show that the shape and size of this asymmetry can be largely explained by the north-south asymmetry of disk star counts and the offset in the Milky Way disk and halo centers of mass due to the Large Magellanic Cloud.

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