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.
DO Dra Typical/high state mag. 15.0 – 15.5 V Range: 10.0 – 17.2 V
23:00 – 23:59 UT
250mm f4.8 Newtonian
Atik 460ex @-10°C
70 x 60s dfb
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.
I’ve been continuing to gather HOYS data as normal and particularly focusing on this star as it’s a bit too low for most people in the evening, but high enough even when below the Pole Star from here in Edinburgh. A lot of the last few weeks data points are mine. Going back to the CCD camera and using real V and R photometric filters has increased accuracy to 0.02 – 0.04 as well.
The star has just undergone a new outburst and is starting to decline again.
The HOYS project reached another recent milestone of 60,00 images in the database. Unfortunately this means the database is now very slow to extract data for lightcurves for. Needs some funding for a developer to work on the database indexing.
2022hrs (= ATLAS22mip), TNS discovered 2022/04/16.619 by Koichi Itagaki Found in NGC 4647 at R.A. = 12h43m34s.350, Decl. = +11°34’36”.00 Located 30″.0 east and 18″.7 south of the center of NGC 4647 Galaxy is about mag. 12.5, supernova about mag. 14.1 R using photometry with ASTAP.
2022ewj (= ATLAS22jhw), TNS discovered 2022/03/19.544 by Koichi Itagaki Found in NGC 3367 at R.A. = 10h46m34s.630, Decl. = +13°45’16”.98 Galaxy is about mag. 12, supernova about mag. 16.3 R using photometry with ASTAP.
2021agpf (= ATLAS21bnoc), TNS discovered 2021/12/26.624 by ATLAS Found in NGC 5732 at R.A. = 14h40m37s.708, Decl. = +38°37’56”.31 Galaxy is about mag. 14, supernova about mag. 17.3 using photometry with ASTAP.
Second submission to GOSA project. This was marked as a “Hot target”. There was a close almost-grazing-occultation with the fainter star nearby. Looked like it was going to be very close but I suspect missed in the end.
A large main belt asteroid, discovered by Austrian astronomer Johann Palisa in 1879. Thought I’d try the same technique as for an eclipsing binary. One extra step in AstroImageJ to track the asteroid between frames. Didn’t get enough data to determine a period and comparison stars were impossible to find in this particular field so relative flux only.