coatesg

Three HADS stars from the night of the 14th/15th - YZ UMi is well placed for not having to move the dome at all at +85 Dec!

V645 Ser, GSC2623-1174 and YZ UMi. All V filter on 350mm Newtonian. 

Indeed - I enjoyed it too (a welcome break from other stuff going on!) - thanks for putting it on! As a CCD observer, not two stars I'd often/ever observe as well 👍

Cheers! (More by luck after I nodded off, but probably got more data than I otherwise would have done 😆)

Currently in superoutburst (max light 16th April), V844 Her is an SU UMa type Cataclysmic Variable, and is displaying superhumps in the light curve with an amplitude of about 0.16mag.

Captured from W Oxon, 151 x 90s, 350mm newt, ST2000XM, V filter (most of it after I nodded off on the sofa - luckily it is well placed to stay in the "slot" of the dome for almost all the session...)

ER UMa is currently in superoutburst (it's fading from the max at about 12.5V and is currently about 13.4V). This is a peculiar sub-class of SU UMa type dwarf nova that has very frequent outbursts - somewhere around 43d between superoutbursts (see discovery paper: http://adsabs.harvard.edu/full/1995PASJ...47..163K). Last 2 nights I have managed to do some time resolved runs to try to record superhumps in the light curve. First evening wasn't great, and was affected by thin/passing cloud a bit. Last night was much better and allowed a much longer uninterrupted run

I omitted the error bars from the ER UMa points to try and more clearly show the shape of the curve.

13-14/04:

14-15/04:

... was one of the most impressive auroral displays of modern times. I saw a bright red sky from Southern London with bright white streamers. It was visible as far south as Southern France.

(I should fish out the prints from the loft! If you have photos please post them!)

Remember this well as it was my 20th birthday at the time...! Another 2 decades older now!

Managed to find a well timed minima of BS UMa to capture last night. This is catalogued as an EA type eclipsing binary with period 8.388237hrs, with almost exactly a 1hr rise/fall time. Looks like there's possibly some reflection effect from the "shoulders" in the curves.

Minima timed as HJD 2458940.4271 +/- 0.0001 (calculated using Minima27).

All images 30sec, V filter, ST2000XM, 350mm Newtonian.

Based on the ephemeris "2452500.248  + E x 0.3153620" from the Krakow database (J.M. Kreiner, 2004, Acta Astronomica, vol. 54, pp 207-210.), the predicted minimum for epoch 20409 is: HJD 2458936.47106 - so looks like: O-C=+0.0085 - appears to be a bit anomalous compared to this O-C plot...:

(EDIT; but appears to fit right in with Bob Nelson's OC data - no idea what's wrong here!) 

Managed to have a good 5 hour or so run on FV CVn last night - runs like this are going to become more inconvenient as the clocks change tonight and it gets darker later! Have an issue with tracking on the mount, which doesn't affect variable work so much, but there's an odd jump here or there in tracking - it may well be a balance issue (I'd tried to improve it and clearly made it worse!) - gladly for variables, it's not so critical as for astroimaging!

Minimum measured as JD 2458936.4752 +/- 0.0001. (HJD = 2458936.4796)

(All images were 60s, 350mm Newtonian, f4.6, ST2000XM, V filter)

7 hours ago, Dave Smith said:

Good work Graeme. Any idea why the second one is more noisy even though it is brighter?

Declination of -2 so higher airmass, and our row of terrace houses forms an artificial horizon due south of my dome! Heat from the houses, central heating, open fires... not great !! (Also, the scales are different on the graphs - the second one only seemed to vary by <0.2mag)

Quite a productive period at the moment third night on the trot! Another two HADS stars: 

V488 Gem and GSC 4935-0348 (ASAS J115229-0245.1). The latter looks quite symmetric for a HADS star - usually a much quicker rise than this.

V488 Gem is in quite a busy field:

Ah that's good - and the wrong way round compared to usual!

I tend to shoot for 10-20k ADU which gives good headroom and space to drop while still having decent snr...of course it can always go to pot! 

A nice evening last night - dark and transparent - was able to get quite good data with relatively short exposures - here V1209 Her is between mag 13.4 and 14.1 - I started out with 3min exposures, reduced it to 2, and then (through a bit of an error) finished up with 1 min exposures. Even then, the error bounds are very reasonable. 350mm newt + ST2000XM, V filter.

I did also obseerve V488 Gem - on the other side of the mount, and lower in the sky over the houses, the tracking and seeing was not so good. Still usable data - just need a sequence from the AAVSO at the scale I work at (26x19 arcmin)

Yeah - high cloud (or worse, passing cloud that affects the comparisons and the target unequally) will definitely give weird results like this. It's usually right at the end of the period as well! 

2 hours ago, Dave Smith said:

Well done Graeme, keep up the good work. This is the first HADS star I ever tried but at that time was unaware of the project.

I have spent two nights this week on V467 Dra which has a very long period but unfortunately the seeing/transparency must have been rubbish as the results after a short decent period were very scattered. I did submit them to Patrick but I guess he was unable to get the period as they haven't appeared on his chart.

 

Cheers! Sometimes Patrick does take a few days to put them on for me, but they generally appear eventually! 😉

Trying to keep some kind of sense of normality by doing some astronomy. Here is YZ Boo - a HADS star for the ongoing study (this month appears to have been very productive looking at the data already captured, so landed up going for something quite a way in the east).

V filter, 350mm Newtonian, 15 sec each exposure. Seeing and transparency not so good at times, esp early.

Stay well all. 

Well, that's pretty good - I got 2458911.4375 out of minima27 - estimated the error as +/- 0.0002. I think the polynomial struggles with the flat base to the eclipse (much like the Fourier fit). Doing the forwards/backwards graph would show a lack of overlap I think.

Thanks for putting the data through!

I've used a demo install of Peranso to determine a ToM yup. Try the guide here: https://www.variablestarssouth.org/wp-content/uploads/2017/06/SEB-Basic-Analysis-Procedure.pdf (section 3) 

Nice one - would be interested to see the differences in ToM that minima27 gives compared to Peranso! 

(I'm happy to share the data with the flat bottomed eclipse if you'd like to try that too and see what it spits out). 

KP Lyn is a repeat observation for me - I observed it last March - this is a HADS with catalogue period = 109.34486 min

OJ287 is something altogether different! It's a well studied BL Lac object - it lies at ~3.5 billion ly distance in Cancer (as we look at it), and is thought to be a binary pair of super-massive black holes. One is "only" 100M solar masses, the other is thought to be a monumental 17 Billion solar masses. Interestingly, as the black holes orbit, the smaller one passes through the accretion disc of the larger one, resulting in a double peak in brightness at those times.

Here's one of the frames I took (I got 4 before clouded out) - this view is unreduced: 5min exposure, V filter, ST2000XM, 350mm Newtonian. OJ287 highlighted on image. The galaxy at bottom is IC2423.

I measured it as (middle of exposure):

03/03/2020 21:54:15 - 15.076V +/- 0.016
03/03/2020 21:59:52 - 15.077V +/- 0.013
03/03/2020 22:05:18 - 15.073V +/- 0.013
03/03/2020 22:10:37 - 15.094V +/- 0.019

I suspect the last reading might have had a bit of cloud interference, though it does vary about a bit.

And yes - using their quadratic formula for the calculated minima, I get the O-C to be -0.00287d (-4m8s) for epoch 14980. Without going through the error calcs for the quadratic terms I'd be very surprised if this was outside of the error bounds!

17 minutes ago, Whirlwind said:

There's already a paper on this.  The changing period does appear to be known about.  Might be worth comparing.

https://iopscience.iop.org/article/10.1088/0004-6256/141/5/151

Oddly I've just been reading that very paper yes!  

Churning them out well Dave! Curves all looking very nice indeed.

So I used the "Minima" software by Bob Nelson - available from https://www.variablestarssouth.org/software-by-bob-nelson/. 

It has several different ways of calculating the minimum - I think there's a little care in the usage here given the "flat bottom" to the minimum (esp when using Fourier methods), but it's reasonably straightforward to use - you just need to sense check the output (and the errors!)

Agree - the O-C looks like a curve - there will likely be mass transfer taking place here, and probably tidal changes, so there would need to be a lot more data over time to try and pin down exactly what it is doing. 

Last night I observed a minimum of the EW type star XY LMi, which is an EW type eclipsing binary with catalogue period 10.48535 h. 

The time of minimum appears to be -0.0542d different to the predicted minimum from the Lichtenknecker Database value - this star has a last observed minimum in that database on 11/03/2017 where the ToM was -0.0395d different to the predicted value - the O-C curve plotted with my own timing point seems to show that the curve in O-C (B-R here) appears to be carrying on in the same manner as before, but obviously with no intervening data!

 325 x 15sec exposures through a Astrodon V filter to get the following plot.