AAVSO “Alert Notice 753: Monitoring requested for seven intermediate polars” – DO Dra (also known as YY Dra) is on the list, it’s circumpolar and easy from here.
“Photometry (V, CV) of the targets in the table below is requested. DSLR green and visual observations are welcome to supplement the light curves. The cadence requested is every other night, as weather permits, and “about one hour of coverage per night (enough to catch a few spin cycles of the white dwarf). If a source is found to be in a low state, then we request longer coverage and nightly cadence. SNR>>10 is ideal…”
Photometry (V, CV) of the targets in the table below is requested. DSLR green and visual observations are welcome to supplement the light curves. The cadence requested is every other night, as weather permits, and “about one hour of coverage per night (enough to catch a few spin cycles of the white dwarf). If a source is found to be in a low state, then we request longer coverage and nightly cadence. SNR>>10 is ideal…”
Covington adds: “These systems show periodic variability on the spin period of the WD, usually on order of ~10 minutes. So, shorter exposure times are needed so the spin variability isn’t washed out. Previous AAVSO observations of these sources have had exposure times <60s, which is ideal. Also, accurate time tagging of the observations is required, so we can measure periodicities!”
Thought I’d give it a go for 1 hour. Uploaded to AAVSO and BAA databases.
| Object ID | DO Dra Typical/high state mag. 15.0 – 15.5 V Range: 10.0 – 17.2 V |
| Details | 23:00 – 23:59 UT |
| Telescope | 250mm f4.8 Newtonian |
| Camera | Atik 460ex @-10°C |
| Filters | V photometric |
| Exposure(s) | 70 x 60s dfb |
| Capture | NINA |
| Processing | ASTAP |
An Intermediate Polar (also called a DQ Herculis Star) is a type of cataclysmic variable binary star system with a white dwarf and a cool main-sequence secondary star. In most cataclysmic variables, matter from the companion star is gravitationally stripped by the compact star and forms an accretion disk around it. In intermediate polar systems, the same general scenario applies except that the inner disk is disrupted by the magnetic field of the white dwarf.
The name “intermediate polar” is derived from the strength of the white dwarf’s magnetic field, which is between that of non-magnetic cataclysmic variable systems and strongly magnetic systems. Non-magnetic systems exhibit full accretion disks, while strongly magnetic systems (called polars or AM Herculis systems) exhibit only accretion streams which directly impact the white dwarf’s magnetosphere.
