Exocomet signatures around the A-shell star φ Leonis?

¹ Dpto. Física Teórica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
e-mail: carlos.eiroa@uam.es
² CAB (CSIC-INTA), Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
³ STAR Institute, Université de Liège, F.R.S.-FNRS, 19c Allée du Six Août, 4000 Liège, Belgium
⁴ Max-Planck-Institut für Astronomie (MPIA), Königstuhl 17, 69117 Heidelberg, Germany
⁵ Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, 5030 Casilla, Valparaíso, Chile
⁶ Université de Toulouse, UPS-OMP, IRAP, 31400 Toulouse, France
⁷ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21212, USA
⁸ Steward Observatory, Department of Astronomy, University of Arizona, Tucson, AZ 85721, USA
⁹ INAF, Osservatorio Astronomico di Palermo, 90134 Palermo, Italy
¹⁰ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, PO Box 67, 1525 Budapest, Hungary
¹¹ Aurora Technology B.V. for ESA, ESA-ESAC, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
¹² Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, PO Box 43, 221 00 Lund, Sweden
¹³ ESA-ESAC, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
¹⁴ Exoplanets & Stellar Astrophysics Lab., NASA Goddard Space Flight Center, Code 667, Greenbelt, MD 20771, USA

Received: 11 August 2016
Accepted: 12 September 2016

Abstract

We present an intensive monitoring of high-resolution spectra of the Ca ii K line in the A7IV shell star φ Leo at very short (minutes, hours), short (night to night), and medium (weeks, months) timescales. The spectra show remarkable variable absorptions on timescales of hours, days, and months. The characteristics of these sporadic events are very similar to most that are observed toward the debris disk host star β Pic, which are commonly interpreted as signs of the evaporation of solid, comet-like bodies grazing or falling onto the star. Therefore, our results suggest the presence of solid bodies around φ Leo. To our knowledge, with the exception of β Pic, our monitoring has the best time resolution at the mentioned timescales for a star with events attributed to exocomets. Assuming the cometary scenario and considering the timescales of our monitoring, our results indicate that φ Leo presents the richest environment with comet-like events known to date, second only to β Pic.