Short period pulsating star DY Her spectroscopy and photometry (Remco Kemperman)

Short period pulsating star DY Her spectroscopy and photometry

DY Hercules, a short period pulsating star. Photometry and spectoscopy.

DY Her is a star that pulsates in 3.56 hours. This type is similar to the well known Cepheid variables which are known for their period/luminosity relation.

The star expands in a short time from small and hotter (blue) to bigger and cooler (red). In addition, it also becomes brighter, between magnitude 10.15 and 10.66.

Although it is smaller when it is hotter (bluer), the star is brighter. This is due to the fact that hotter material radiates exponentially more heat. (depending on the temperature to the 4th power.

If the star is hotter at its maximum, it is a type A7iii star. in minimium it is an F4iii star. Type A stars are have deeper hydrogen absorption lines than F stars, which is also shown in the spectra.

I took spectra last night and then ran them through a photometric analysis to see which images are at the minima and the maxima (see circled measuring points in graph). I stacked those to get a better signal. All individual spectra are 5 minute recordings.

The last chart is from a week earlier when i did photometry on the same star with 60 second exposures all night long. Ther also happened to be an eclising binary star in the field of view, V1379 Her.

Those photometry measurements will be submitted to the AAVSO later on.

The images where taken with a QHY294 camera and 6" F/5 Newtonian. R-spec astro for the spectral analysis and AstroImageJ for the photometric analysis.

Original
Final
B

B

Description: I have tried a different way of presenting the variability of the pulsation of DY Her.
This time I integrated 3 exposures at a time to get a reasonable SNR and processed those stacks individually as spectra.
An animation of 2:25 hours as a result, from minimum tot maximum and back to minimum.
The full period of DY Her is 3:21.

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