Transit Depth Budgets Across Spectral Types From M Dwarfs to F Stars

This study computes a detection budget for a clearly bounded question: How deep is the transit of a given planet as a function of the spectral type of its host, and what photometric precision does a single-transit detection therefore demand from F stars down to mid-M dwarfs? An Earth transit is 84 ppm deep on a G2 star, 131 ppm on K2, 414 ppm on M2 and 2095 ppm on M5. On an F5 star the same planet gives only 43 ppm, the shallowest terrestrial case in the grid. A Neptune gives 1251 ppm on a solar twin and 31287 ppm on an M5 dwarf. All values are computed from published anchor values and stated assumptions by a deposited script; the study is simulated and computed throughout, not measured. Host-star radius converts into transit depth quadratically, giving M-dwarf terrestrial transits one to two orders of magnitude more signal than solar-type equivalents.