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We present a study of two newly discovered heliocentric hyperbolic objects --2017 U7 and 2018 C2. Both are possibly thermally evolved comets. Observationsof the latter in 2018 March from Xingming Observatory revealed that it has acolor similar to those of the long-period comets, Trojans, and D-typeasteroids: $m_B - m_V = 0.75 \pm 0.03$, $m_V - m_R = 0.41 \pm 0.02$, and $m_R -m_I = 0.37 \pm 0.03$. A possible extremely faint coma of $\sim$9$"$ across wasobserved. The radial profile of 2018 C2 in comparison with those of the fieldstars helps confirm its cometary nature. Based on our convolution model, itsmass-loss rate is estimated to be $0.7 \pm 0.2$ kg s$^{-1}$. Assuming geometricalbedo $p_R = 0.04$, its effective radius is $4.4 \pm 0.5$ km, which means thatthe fraction of active area is merely $\sim$10$^{-5}$-10$^{-4}$. Our N-bodydynamical simulations show that both objects are most likely dynamically oldmembers from the Oort cloud. 2017 U7 has a $\sim$60% chance to escape the solarsystem in the 1.5 Myr following its current perihelion passage due to amoderate close encounter with Jupiter in 2020 May. On the condition that nodisintegration occurs, 2018 C2 will revisit the inner solar system 0.13-0.14Myr later, with perihelion distance $\sim$2 AU.

Two Hyperbolic Baldheads in the Solar System: 2017 U7 and 2018 C2