Hint of an exocomet transit in the CHEOPS lightcurve of HD 172555
Creators: name: Kiefer, F.
name: Van Grootel, V.
name: Etangs, A. Lecavelier des
name: Szabó, Gy. M.
name: Brandeker, A.
name: Broeg, C.
name: Cameron, A. Collier
name: Deline, A.
name: Olofsson, G.
name: Wilson, T. G.
name: Sousa, S. G.
name: Gandolfi, D.
name: Hébrard, G.
name: Alibert, Y.
name: Alonso, R.
name: Anglada, G.
name: Bárczy, T.
name: Barrado, D.
name: Barros, S. C. C.
name: Baumjohann, W.
name: Beck, M.
name: Beck, T.
name: Benz, W.
name: Billot, N.
name: Bonfils, X.
name: Cabrera, J.
name: Charnoz, S.
name: Csizmadia, Sz.
name: Davies, M. B.
name: Deleuil, M.
name: Delrez, L.
name: Demangeon, O. D. S.
name: Demory, B. -O.
name: Ehrenreich, D.
name: Erikson, A.
name: Fortier, A.
name: Fossati, L.
name: Fridlund, M.
name: Gillon, M.
name: Güdel, M.
name: Heng, K.
name: Hoyer, S.
name: Isaak, K. G.
name: Kiss, L. L.
name: Laskar, J.
name: Lendl, M.
name: Lovis, C.
name: Magrin, D.
name: Maxted, P. F. L.
name: Munari, M.
name: Nascimbeni, V.
name: Ottensamer, R.
name: Pagano, I.
name: Pallé, E.
name: Peter, G.
name: Piazza, D.
name: Piotto, G.
name: Pollacco, D.
name: Queloz, D.
name: Ragazzoni, R.
name: Rando, N.
name: Ratti, F.
name: Rauer, H.
name: Reimers, C.
name: Ribas, I.
name: Santos, N. C.
name: Scandariato, G.
name: Ségransan, D.
name: Simon, A. E.
name: Smith, A. M. S.
name: Steller, M.
name: Thomas, N.
name: Udry, S.
name: Walter, I.
name: Walton, N. A.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: HD$\,$172555 is a young ($\sim$20$\,$Myr) A7V star surrounded by a 10$\,$au wide debris disk suspected to be replenished partly by collisions between large planetesimals. Small evaporating transiting bodies, exocomets, have also been detected in this system by spectroscopy. After $β\,$Pictoris, this is another example of a system possibly witnessing a phase of heavy bombardment of planetesimals. In such system, small bodies trace dynamical evolution processes. We aim at constraining their dust content by using transit photometry. We performed a 2-day-long photometric monitoring of HD$\,$172555 with the CHEOPS space telescope in order to detect shallow transits of exocomets with a typical expected duration of a few hours. The large oscillations in the lightcurve indicate that HD$\,$172555 is a $δ\,$Scuti pulsating star. Once removing those dominating oscillations, we find a hint for a transient absorption. If fitted with an exocomet transit model, it corresponds to an evaporating body passing near the star at a distance of $6.8\pm1.4\,$R$_\star$ (or $0.05\pm 0.01\,$au) with a radius of 2.5 km. These properties are comparable to those of the exocomets already found in this system using spectroscopy, as well as those found in the $β\,$Pic system. The nuclei of solar system's Jupiter family comets, with radii of 2-6$\,$km, are also comparable in size. This is the first evidence for an exocomet photometric transit detection in the young system of HD$\,$172555.
description: 12 pages, 10 figures, 5 tables, accepted for publication in A&amp;A