Star AB Aur Research Articles

The well-known Herbig AE star AB Aur. I. Investigation of variability of the emission lines in the region 0.37?0.88 ?m

The variability of the profiles, equivalent widths (EW/sub /lambda//), and relative intensities of of the emission lines in the spectrum of AB Aur has been investigated with a photoelectric scanner. During a 20-day period of observations, EW/sub /lambda//H/sub /alpha// varied from 23.20 to 35.35 /angstrom/. The mean value was EW/sub /lambda//H/sub /alpha// = 27.25 /angstrom/, the rms fluctuation 3.60 /plus minus/ 0.07 /angstrom/. The shortest variability time was 1 h. The chromospheric lines of the infrared Ca II triplet, K Ca II, the emission lines H/beta/-H13, P12-P20, OI 8446.5 /angstrom/ and others were investigated using spectra obtained photographically or with an image tube. The intensities of these lines vary by factors 2-4 during a time from one hour to several years. The nature of the variability of the emission lines of AB Aur suggests that the deep chromosphere is not a centrally symmetric or axisymmetric formation but rather a conglomerate of gas condensations of different densities and velocities.

Short-term spectral variability in AB Aurigae: Clues for activity in Herbig AE stars. II - The CA II K line

view Abstract Citations (63) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Short-Term Spectral Variability in AB Aurigae: Clues for Activity in Herbig AE Stars. II. The CA II K Line Catala, C. ; Felenbok, P. ; Czarny, J. ; Talavera, A. ; Boesgaard, A. M. Abstract The Herbig Ae star AB Aur (A0ep) was monitored with the CFH 3.6 m and the Observatoire de Haute-Provence 1.52 m telescopes in the Ca II K line, for six nights in 1982 October. Some of the 39 recorded spectra were simultaneous with ultraviolet spectra obtained with IUE. The Ca II K line is variable and modulated with a period of 32±4 hours, corresponding to the estimated rotation period of the star. The difference between the 45 hour period found in the Mg II data (Paper I) and the 32 hour period in the Ca II data is assumed as due to a differential rotation in the envelope of the star. This differential rotation allows an estimate of upper limits for the magnetic field and the Alfvén radius in the envelope of AB Aur, as well as for the rate of angular-momentum loss. Publication: The Astrophysical Journal Pub Date: September 1986 DOI: 10.1086/164551 Bibcode: 1986ApJ...308..791C Keywords: A Stars; Abundance; B Stars; Line Spectra; Stellar Spectra; Stellar Spectrophotometry; Calcium; Emission Spectra; K Lines; Red Shift; Stellar Rotation; Astrophysics; STARS: EMISSION-LINE; STARS: INDIVIDUAL CONSTELLATION NAME: AB AURIGAE; STARS: ROTATION; STARS: SPECTRUM VARIABLES full text sources ADS | data products SIMBAD (1) Related Materials (1) Part 1: 1986ApJ...303..311P

Short-term spectral variability in AB Aurigae - Clues for activity in Herbig AE stars. I - The ultraviolet lines of MG II and Fe II

IUE satellite monitoring of the Herbig Ae star AB Aur in 1982 and 1984, with attention to the variability of both the Mg II 2795 A wind profile and a number of Fe II UV lines, has indicated temporal variations in the Mg II blue wing velocity by 30-50 percent at both epochs. By contrast, the Fe II spectrum was constant in 1982, but variable in 1984. There is no evidence of photometric variability in AB Aur during either period. An analysis of the Mg II blue wing velocity vs time shows that the variability can be fitted with a sine curve of period 45 + or - 6 yr, which is interpreted to be the stellar rotation period. The observed rotational modulation of the blue wing velocity of Mg II 2795 A in AB Aur's wind is the first direct evidence of a nonaxisymmetric wind in an A-type premain sequence object.