Non-radial-pulsations in delta Sco

[Ernst Pollmann]

Observation of non-radial pulsation and line-profile variabilities in δ Sco

Time-series spectroscopic observations of the Si III absorption lines 4553Å & 4567Å of δ Sco were obtained with the LIHRES III spectrograph (2400 L/mm grating, R=14000) and a C14 SC telescope by Carl Sawicki at his observatory in Alpine (Texas). 35 single spectra were obtained during the nights 6/17/20 May 2013 with 15 min exposure for each one. The spectra have been calibrated with an Argon gas tube in front of the telescope aperture. This way of calibration leads to an accuracy of ± 2km/s.

The attached animation (gif-folder) is showing an example of profile variations during the May-17 observations (compare Pollmann´s observation: 14/15 April 2013, compared with spectra series of Myron Smith 1984/85; http://www.astrospectroscopy.de/nrp_deltasco.pdf)

For the evaluation of temporal variations, we selected the measurement of the EW instead of the radial velocity, because it was not clear what line feature during the profile variations we should use. The attached files “overview_4552 & 4567” are showing in the upper plot the EW-time series, the middle plot the period analysis (phase dispersed minimization) and the lower plot the phase itself with analysis data.

First question: how convincing is the determined period of 5.04 hr (0.21 d)?

Here we want to quote M. Smith in ApJ 304, 728-738, 1986, where comparable spectra series (February 1984/85) have been taken:
Feb. 1984: … there is a low-degree, stable mode with a period of 6.8 ± 0.5 hr. 0.5 Feb. 1985: … there are significant line-width variations present on practically every night with a period of 6.8 ± 0.06 hr.
Two identifications are possible for this mode: -m=l=4 (or) –m=l=2

Second question: Did a period decrease take place until now?

Third question: Is the EW a suitable tool for observation of NRP's? (it did work for the Be star ζ Oph; http://www.astrospectroscopy.de/IBVS_6034.pdf)

Comments are welcome!

Carl Sawicki & Ernst Pollmann