从190天高精度分光多点活动探测明亮红巨星$γ$ Psc和$θ^1$ Tau中的类太阳振荡
Detection of solar-like oscillations in the bright red giant stars $γ$ Psc and $θ^1$ Tau from a 190-day high-precision spectroscopic multisite campaign
摘要：
红巨星是演化的恒星，表现出类似太阳的振荡。虽然太空望远镜已经观测到了大量的恒星，但只有少数红巨星是光谱天文观测项目的目标。我们从地面光谱的时间序列中寻找两颗明亮的红巨星$γ$ Psc和$θ^1$ Tau的类太阳振荡，并确定了两颗恒星的振荡功率$ν_{max}$和平均大频率间隔$Δν$的过剩频率。分别监测$γ$ Psc和$θ^1$ Tau的径向速度120天和190天。获得了近9000个光谱。为了达到准确的径向速度，我们同时使用钍-氩和碘电池校准我们的光谱。除了光谱学，我们还获得了$γ$ Psc的VLTI观测，以独立估计半径。还分析了用MOST卫星对$θ^1$ Tau的22天观测。对$γ$ Psc径向速度数据的频率分析显示，在32 $μ$ Hz附近振荡功率过剩，频率间隔较大，为4.1 $\pm$ ± 0.1 $μ$ Hz。$θ^1$ Tau表现出约90 $μ$ Hz的振荡功率，具有6.9 $\pm$ ± 0.2 $μ$ Hz的大频率分离。标度关系表明，$γ$ Psc是一颗大约为$\sim$ 1 M $_\odot$和$\sim$ 10 R $_\odot$的恒星。$θ^1$ Tau似乎是一颗质量约为$\sim$ 2.7 M $_\odot$和$\sim$ 11 R $_\odot$的大质量恒星。这两颗恒星的径向速度被发现调制的时间尺度远长于振荡周期。虽然$θ^1$ Tau的质量与动力学松弛的结果一致，但我们发现$γ$ Psc的质量低于文献中给出的质量。长周期的变化与旋转调制的预期时间尺度一致。
英文摘要：
Red giants are evolved stars which exhibit solar-like oscillations. Although a multitude of stars have been observed with space telescopes, only a handful of red-giant stars were targets of spectroscopic asteroseismic observing projects. We search for solar-like oscillations in the two bright red-giant stars $γ$ Psc and $θ^1$ Tau from time series of ground-based spectroscopy and determine the frequency of the excess of oscillation power $ν_{max}$ and the mean large frequency separation $Δν$ for both stars. The radial velocities of $γ$ Psc and $θ^1$ Tau were monitored for 120 and 190 days, respectively. Nearly 9000 spectra were obtained. To reach the accurate radial velocities, we used simultaneous thorium-argon and iodine-cell calibration of our optical spectra. In addition to the spectroscopy, we acquired VLTI observations of $γ$ Psc for an independent estimate of the radius. Also 22 days of observations of $θ^1$ Tau with the MOST-satellite were analysed. The frequency analysis of the radial velocity data of $γ$ Psc revealed an excess of oscillation power around 32 $μ$Hz and a large frequency separation of 4.1$\pm$0.1$μ$Hz. $θ^1$ Tau exhibits oscillation power around 90 $μ$Hz, with a large frequency separation of 6.9$\pm$0.2$μ$Hz. Scaling relations indicate that $γ$ Psc is a star of about $\sim$1 M$_\odot$ and $\sim$10 R$_\odot$. $θ^1$ Tau appears to be a massive star of about $\sim$2.7 M$_\odot$ and $\sim$11 R$_\odot$. The radial velocities of both stars were found to be modulated on time scales much longer than the oscillation periods. While the mass of $θ^1$ Tau is in agreement with results from dynamical parallaxes, we find a lower mass for $γ$ Psc than what is given in the literature. The long periodic variability agrees with the expected time scales of rotational modulation.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
