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![down quark down quark](https://i.stack.imgur.com/bWzur.png)
The obtained values of the tidal deformability at 1.4 solar masses and the average tidal deformability are all in good compatibility with the experimental constraints of GW170817. Then, we study the related gravitational-wave probe of the tidal deformability in binary star mergers, including the u d QS − u d QS and u d QS − HS cases. Quarks also have a property called color that refers to the strong force that attracts quarks togetherand while there is no actual color at. So protons are positive because there are two ups and one down quark, giving a net positive charge: ((+2/3) + (+2/3) + (-1/3) +3/3 or +1). We show that the requirements of A min ≳ 300 and the most massive compact star observed being a u d QS together may put stringent constraints on the allowed parameter space of u d QSs. Down, strange, and bottom quarks have a negative 1/3 charge. Distinct signatures are discussed compared to the conventional study regarding strange quark stars (SQSs). In this paper, we explore u d quark stars ( u d QSs) that are composed of u d QM, in the context of the two-families scenario in which u d QSs and hadronic stars (HSs) can coexist. Due to the strong force, quarks cannot exist in isolation. Baryons consist of three quarks, and mesons consist of a quark-antiquark pair. These particles are fermions with half-integral spin and fractional charge. With beta minus decay one of the down quarks changes into an up quark. A neutron is made from two downs and an up giving it a charge of 0. A proton is made of two ups and a down, giving it a charge of +1. A down quark has an electric charge of -1/3. Recently, it was shown that quark matter with only u and d quarks ( u d QM) can be the ground state of matter for baryon numbers A > A min with A min ≳ 300. Six known quarks exist: up ( u ), down ( d ), charm ( c ), strange ( s ), top ( t ), and bottom ( b ). An up quark has an electric charge of +2/3.