Nebula around R Corona Borealis

Understand

The star R Corona Borealis (R CrB) shows forbidden lines of [O II], [N II], and [S II] during the deep minimum when the star is fainter by about 8 to 9 magnitudes from normal brightness, suggesting the presence of nebular material around it.

• We present low and high spectral resolution observations of these lines during the ongoing deep minimum of R CrB, which started in July 2007.
• These emission lines show double peaks with a separation of about 170 km/s.
• The line ratios of [S II] and [O II] suggest an electron density of about 100 cm$^{-3}$.