Stellar ejecta from falling comet-like bodies: young stars

Abstract

High-resolution spectral observations of young stars with dense protoplanetary discs like Beta Pictoris led to the discovery of variable emission lines of metal atoms, Na, Fe etc., that indicate the presence of fluxes of comet-like evaporating bodies falling onto the stars, FEBs. Assuming the presence of stellar atmospheres similar to the solar one, we show that passages of the FEBs through the stellar chromosphere and photosphere with velocities around 600 km/s will be accompanied by aerodynamic crushing of the nuclei, transverse expansion of the crushed matter, “explosion” of the flattened nuclei in a relatively very thin sub-photosphere layer due to sharp deceleration, and impulse production of a hot plasma. The impulsive rise of the layer's temperature and density lead to the generation of a strong “blast” shock wave and shock wave-induced ejection/eruption of hot plasma into space above the chromosphere. Observations of such impact-induced high-temperature phenomena are of interest for the physics/prognosis of stellar/solar flares as well as physics of comets.

Massive stars: flare activity due to infalls of comet-like bodies

“…Using (2.1) with ρ n = 0.5 g/cm 3 , R n = 10 5 cm, V * = V 0 , A = 20, z = 5, x 1 = 3 we have Δh e = 140 km, E e = 7 · 10 29 erg, T 0 = 7 · 10 6 K. Hence, "superflares" may be due to impacts with comets like comet Hale-Bopp 1995 OI (cf. Ibadov et al 1999;Grigoryan et al 2000;Ibadov et al 2009;Eichler & Mordecai 2012;Ibodov & Ibadov 2014).…”

“…This indicates the possibility of high energy processes in comets (cf. Ibadov 1990Ibadov , 1996Ibadov et al 2009;Ibodov et al 2010;Ibodov & Ibadov 2011, 2014. Impulse release of a large energy, up to 10 32 erg, is possible due to the magnetic reconnection in the active Sun (cf.…”

Explosive evolution of small bodies in planetary atmospheres

“…Hence, sudden thermalization of the kinetic energy of bodies will be accompanied by explosive high-temperature phenomena (cf. Ibadov 1987Ibadov , 1990Ibadov , 1996Ibadov , 2012Ibodov & Ibadov 2014).…”