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Observation by Stewart Bean: Superhumps from IX Dra

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Stewart John Bean


Stewart Bean


2019 Sep 13 - 12:05


2020 Oct 06 - 12:20

  • TESS satellite, JD2458740
  • Lightkurve
  • in a Python environment

2 min cadence, 100 mm obj, 600-1000nm filter.


Somewhere between Earth and Moon

Target name

IX Dra


Superhumps from IX Dra

About this image

I have downloaded TESS data from the MAST site ( where most variable stars will have some TESS light curves) and plotted the superoutburst from Sept 2019. TESS stares continuously at a fixed point for about 27 days recording red light from about 20,000 targets. Stars round the ecliptic poles receive almost continuous coverage for a whole 12 months campaign so those in Draconis are well favoured.

The plot shows the first part of a superoutburst  with well defined superhumps. The Y axis is in raw flux and not in magnitude.

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Paul Leyland
Paul Leyland, 2020 Oct 19 - 19:03 UTC

Have you analyzed the period of the superhumps?

A light curve folded on that period should be well worth posting.

Stewart John Bean
Stewart John Bean, 2020 Oct 20 - 15:11 UTC

"Lightkurve" and its periodogram give the following results for the superhump period.

Each TESS Sector is ~27 days of data  at 2 min cadence with a gap of one day in the middle to download the results.

0.06705 TESS sector 16

0.06702 TESS Sector 18

0.06703 TESS Sector 25

With no superhumps in the data set:

0.06474 TESS Sector 15

0.06747  TESS Sector 24 . This data set does not sure a strong peak in the periodogram.

0.06479 TESS Sector 26

VSX gives the orbital period as 0.0648 day.  So we have a superhump period that is 3.4% longer than P(orb).



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