AI 中文总结
研究WISPIT 2这颗年轻主序前恒星，通过HFOSC获取其中心恒星光谱，推导大气参数等。分析得出其吸积率低，宿主与行星吸积率比低，两个双原行星宿主恒星吸积均受抑制，为研究多原行星过渡盘提供了新数据。
AI 中文摘要
WISPIT 2是一颗年轻的主序前恒星，拥有多环过渡盘和两颗直接成像的原行星，包括正在吸积的WISPIT 2b，是已知最接近PDS 70的天体。我们展示了用2米喜马拉雅钱德拉望远镜上的HFOSC获得的其中心恒星的首张光谱，推导了大气参数，测试了其年轻程度并限制了吸积状态。我们用iSpec分析低分辨率光谱，并针对盖亚FGK基准星和K型主序前模板在HFOSC分辨率下验证了该管道。我们测量了有效温度Teff = 4551 +/- 150 K，表面重力log g = 4.32 +/- 0.18，以及低分辨率、依赖模型的整体金属丰度[M/H] = -0.17 +/- 0.16。表面重力和锂I等效宽度支持宿主的主序前性质。H-alpha仍处于净吸收状态，但仅在1.5 - 2.0西格玛处被微弱发射部分填充，比预期的色球层噪声水平低约1.1 dex，因此与色球层活动一致而非可探测的吸积。我们对恒星吸积率设定了95%的上限，每年为3.6 x 10^-11太阳质量，低于PDS 70的最低监测值，意味着宿主与行星的吸积率比低于约18。因此，两个已知的双原行星宿主都显示出强烈抑制或不可探测的恒星吸积。需要更大的光谱样本量来确定这在多原行星过渡盘中是否常见。
英文摘要
WISPIT 2 is a young pre-main-sequence star hosting a multi-ringed transition disk and two directly imaged protoplanets, including the accreting WISPIT 2b, making it the closest known analogue to PDS 70. We present the first optical spectrum of its central star, obtained with HFOSC on the 2-m Himalayan Chandra Telescope, and derive its atmospheric parameters, test its youth, and constrain its accretion state. We analyse low-resolution spectra with iSpec and validate the pipeline at HFOSC resolution against Gaia FGK Benchmark Stars and K-type pre-main-sequence templates. We measure T_eff = 4551 +/- 150 K, log g = 4.32 +/- 0.18, and a low-resolution, model-dependent global metallicity [M/H] = -0.17 +/- 0.16. The surface gravity and Li I equivalent width support the pre-main-sequence nature of the host. H-alpha remains in net absorption but is partially filled by weak emission at only 1.5-2.0 sigma, approximately 1.1 dex below the expected chromospheric-noise level and therefore consistent with chromospheric activity rather than detectable accretion. We place a 95% upper limit on the stellar accretion rate of 3.6 x 10^-11 solar masses per year, below even the lowest monitored value for PDS 70 and implying a host-to-planet accretion-rate ratio below approximately 18. Both known double-protoplanet hosts therefore show strongly suppressed or undetectable stellar accretion. Larger spectroscopic samples are needed to determine whether this is common in multi-protoplanet transition disks.
CommentsAccepted for Publication in A&A letters
DOI：10.1051/0004-6361/202661622
