AB Aurigea: an Herbig Ae star

This page present spectroscopic observations of the Ha and He I 5876 A lines in the pre-main sequence Herbig Ae star AB Aur. Stars of this type shows signs of strong stellar winds (P Cygni profile at Ha) and of extended chromospheric activity (click here for a star list). AB Aurigae (HD 31293) is the brightest Herbig Ae star of the northern hemisphere (V=7.1, AD=4 h 55.7, DEC=+30 33 (2000)). The rotation period of the star is near 34 hours. Line profiles aspect are rapidly variables, so time resolution is recommended (time sampling inferior to one hour if possible). Ideally, multi-site observations are also recommended for tracking activity region during the fast rotation period (between 1 to 2 days). But a long term studies of the star is also necessary for a better understand of the wind generation mechanism and of chromospheric heating. Claude Catala (Paris-Meudon observatory) suggest (1) to take 3 to 4 spectra per night during period sequences of 10-20 days, (2) to take one spectrum per week during period sequences of 5-6 months.

The instrument used is a 0.28 meter Schmidt-Cassegrain telescope, a LHIRES III spectrograph (1200 lines/mm grating configuration and 26 microns width entrance slit) and an Audine KAF402ME CCD camera (9-microns pixel size). The spectral inverse sampling is 0.34 A/pixel. The measured spectral power resolution on calibration emission lines (neon lamp) is about R=7300 at Ha. The observatory is suburban (Castanet-Tolosan near city of Toulouse, south of France). Click here for typical details about reduction procedure for LHIRES III spectra.

AB Aur star is the bright object in lower left of the center.
60 cm telescope at Pic du Midi in 1994 (Buil-Thouvenot Atlas).
The object is surrounded by Vdb 31 nebulosity.

29 November 2006

Typical Ha profile of AB Aur
Short-term spectral variability are noticed (interval time sampling near one-hour).
The exposure duration is of 5x300 s, 10x300 s and 8x300 seconds respectively
for mid-time observations 19:21 UT, 21:30 UT and 22:50 UT.
Telluric water vapour lines are removed.

He I 5876 A spectral region
Exposure : 12 x 300 seconds.

2D visualisation of the spectral profile near He I 5876 A line.
Notice the interstellar sodium (narrow lines) superimposed of faint AB Aur emission lines.

30 November 2006

Continuous 7 hours observation on the Ha profile
The exposure duration for each profile is of 5 x 300 seconds (30 minutes).
The seeing is not very favorable (near 6 arc-seconds)

Difference of the date profile and the mean profile for the night.
A (chromospheric) event is noticed at 2:30 UT

The mean spectrum (sum of the 7 hours data run)

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