Fast variability of the outflow in the Z CMa system

Abstract

High‐resolution, time‐resolved spectroscopic observations of Z CMa carried out on 1997 January 14–17 are presented. Large night‐to‐night and hour‐to‐hour variations in Hα, Hβ and Na i D P Cygni absorptions, as well as an Hβ emission peak, were observed. Variations in the red wings of the hydrogen emission lines were also detected. The high‐velocity wide‐emission component on the blue side of Hα appeared on January 17. The observations are discussed in the framework of current wind models.

The stellar composition of the star formation region CMa R1 - III. A new outburst of the Be star component in Z CMa

“…The EW of the Hα emission has increased slightly with respect to that of 1991. However, Chochol et al (1998) have found that the daily variations of the Hα emission can be considerable so that small changes over long periods do not permit us to draw any conclusions. We also note here that the Paschen emission lines are not detected in the 1996 spectrum, so that the Ca ii (2) lines do not have to be corrected for the contribution by the Paschen lines. The ESO profiles of the Ca ii (2) lines at 8498 and 8542 Å are very similar to those of the WHT spectrum of December 26.…”

“…The EW of the Hα emission has increased slightly with respect to that of 1991. However, Chochol et al (1998) have found that the daily variations of the Hα emission can be considerable so that small changes over long periods do not permit us to draw any conclusions.…”

“…There exist at least six recent profiles of the [O i ] 6300.3 Å emission in Z CMa: the profile of 2002 March 31, a profile obtained on 1998 January 23 (Garcia et al 1999), one profile from the WHT spectrum of 1996 December, four profiles from 1997 January 14–17 (Chochol et al 1998), two profiles from 1991 December 20 and 21 and one profile from 1987 February 12 (Hessman et al 1991). Fig.…”

“…1). Parts of similar spectra, taken in 1996 January and 1997 January have been published by Teodorani et al (1997) and Chochol et al (1998), respectively. Our low-resolution spectra of 1992 December also correspond to this brightness.…”

Photometric variability in FU Ori and Z CMa as observed by MOST★

“…3, right panel) containing many incoherent variations down to time scales of about 0.3 day. At least a part of these oscillations may have their origin in the night-to-night and hour-to-hour variations of Hα, H β , Na I D P Cygni absorptions and in the H β emission peak (Chochol et al 1998). Also, from speckle observations obtained in the infrared H&K filters Hass et al (1993) reported that both components of the close visual double were varying independently by ∼ 0.5 mag.…”