The HARPS/HARPS-N Data Reduction Software (DRS) relies on the cross-correlation between the observed spectra and a suitable stellar mask to compute a cross-correlation function (CCF) to be used both for the radial velocity (RV) computation and as an indicator of stellar lines asymmetry, induced for example by the stellar activity. Unfortunately the M2 mask currently used by the HARPS/HARPS-N DRS for M-type stars results in heavily distorted CCFs. We created several new stellar masks in order to decrease the errors in the RVs and to improve the reliability of the activity indicators as the bisector’s span. We obtained very good results with a stellar mask created from the theoretical line list provided by the VALD3 database for an early M-type star (T eff = 3500 K and log g = 4.5 $\log {g}=4.5$ ). The CCF’s shape and relative activity indicators improved and the RV time-series allowed us to recover known exoplanets with periods and amplitudes compatible with the results obtained with HARPS-TERRA.

中文翻译：

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在 GAPS 计划中使用 HARPS-N 在 TNG 中观测到的 M 型恒星的恒星掩膜和平分线形状

HARPS/HARPS-N 数据缩减软件 (DRS) 依赖于观测光谱和合适的恒星掩模之间的互相关来计算互相关函数 (CCF)，该函数既用于径向速度 (RV) 计算，也用于作为恒星线不对称的指标，例如由恒星活动引起。不幸的是，目前 HARPS/HARPS-N DRS 对 M 型恒星使用的 M2 掩膜导致 CCF 严重失真。我们创建了几个新的恒星掩码，以减少 RV 中的误差并提高活动指标作为平分线跨度的​​可靠性。我们使用由 VALD3 数据库提供的理论线列表为早期 M 型恒星（T eff = 3500 K 和 log g = 4.5 $\log {g}=4.5$ ）创建的恒星掩模获得了非常好的结果。