HST UV spectra were obtained to study whether the φ Leo system has one or more stellar companions, as shown for the A-star dwarf, HR10, stellar pulsation, or transiting exocomets. During five partial HST observation sets spread over 13 months, redshifted gas with radial velocities up to +245 km s⁻¹ was observed on one occasion, with lower velocity infalling material seen twice. Blueshifted gas features with velocities as high as −150 km s⁻¹ with up to three features in two spectra were also seen. Low-mass stellar companions to late A stars are coronal sources. Assuming an age of 450 Myr, G-K companions to φ Leo, and multiple M-star companions would have been detected in the ROSAT All-Sky Survey data, but are not seen. Further, the star shows only 1 major pulsation component, suggesting it is single, excluding an A- or early F-star companion. Low covering factor absorption features with ∣v∣ ≤ 200 km s⁻¹ have been reported in optical spectra with variation on timescales consistent with nonradial pulsation. However, the highest velocity infall feature has a broader, continuous absorption profile extending from the stellar velocity to +245 km s⁻¹, with a covering factor of ∼25% which is more consistent with a transit by a body on a star-grazing orbit.

获得了 HST 紫外光谱以研究φ Leo 系统是否有一个或多个恒星伴星，如 A 星矮星、HR10、恒星脉动或凌日系外彗星所示。在分布于 13 个月的五个部分 HST 观测组中，一次观测到径向速度高达 +245 km s ^{-1 的}红移气体，两次观测到速度较低的物质。还观察到速度高达 -150 km s ^{-1 的}蓝移气体特征，在两个光谱中具有多达三个特征。A晚期恒星的低质量伴星是日冕源。假设年龄为 450 Myr，GK 伴随φ在 ROSAT 全天巡天数据中会检测到 Leo 和多个 M 星伴星，但没有看到。此外，这颗恒星仅显示 1 个主要脉动分量，表明它是单一的，不包括 A 星或早期 F 星伴星。∣ v ∣ ≤ 200 km s ^{-1 的}低覆盖因子吸收特征已在光谱中报告，其时间尺度变化与非径向脉动一致。然而，最高速度下降特征具有更宽的、连续的吸收分布，从恒星速度延伸到 +245 km s ^-1，覆盖因子约为25%，这更符合天体掠过恒星的过境轨道。