Affiliation
American Association of Variable Star Observers (AAVSO)
Fri, 07/21/2017 - 21:02
AAVSO Alert Notice 588 announces a campaign on the ER UMa-type cataclysmic variable DDE 48 (located in Vul). Please see the notice for details and observing instructions.
Many thanks, and Good observing,
Elizabeth Waagen, AAVSO HQ
Many thanks to Elizabeth for publishing the campaign so quickly! Though DDE 48 itself is still oscillating between normal outbursts, its neighbor (MASTER OT) went into bright outburst immediately after the call for observatoins!
MASTER OT J204627.96 242218.0
2017-07-20.9865 19.77 ART
2017-07-22.1218 15.71 ART Outburst!
I am adding the links to both variables in AAVSO VSX. Please be careful not to confuse them, since their AUIDs differ by only one digit.
DDE 48 (000-BLZ-464): https://www.aavso.org/vsx/index.php?view=detail.top&oid=473984
MASTER OT J204627.96+242218.0 (000-BLZ-444): https://www.aavso.org/vsx/index.php?view=detail.top&oid=473979
I am attaching the animation of ART images from July 18/19, 20/21 and 21/22 showing the outburst of MASTER OT. Both CVs are marked with arrows, and the recommended comparison and reference stars are marked.
If somebody starts to run long time series, please notify us in this topic, so that other observers in your longitude would not be duplicating the efforts. Good observing!
Denis (DDE)
Hi,
I'm currently monitoring DDE 48. My last value is: 2457957.40174 V=16.727 (CV), so it seems that the outburst has already begun.
My set-up does not allow to obtain high-cadency photometry: with 300" exposures I have only S/N=15 (my telescope is only 8"). I will continue monitoring the star if you consider the photometry will be useful.
I attach a fresh image of DDR 48 and MASTER OT J204627.96 242218.0, easily visible.
Greetings
Fran
Realicé una pequeña serie de mediciones con relación S/R 34 y tiempos de integración de 80 egundos, anoche 22 de Julio; he mandado los datos a la web.
No me reconoce esta cabecera de estrella; para enviar los datos vía Web. Tengo que añaidir algo?
El nombre está incompleto. Debes poner MASTER OT J204627.96+242218.0
Saludos
Fran
Thanks to observations by Francisco Campos, Teofilo Arranz, Nikolay Mishevskiy and Dirk Cornelis we have followed the peak of the normal outburst of DDE 48 on July 22/23. Snapshot with ART from July 23/24 shows the star fading by 0.6m, to 16.8. This is temporary fading. We are entering the most interesting phase of the light curve when the next superoutburst will occur. Please continue the observations! I expect DDE 48 will fade to 17.5-18m on July 24/25, and then go to main outburst (15.3-15.4m) on July 25/26. The supercycle length is 36 days, and there are 4 normal outbursts between the superoutbursts.
Meanwhile the long run by Dirk Cornelis shows the growing superhumps in MASTER OT J204627.96+242218.0 with an amplitude about 0.1-0.15m. More data are needed to determine the period.
You might have noticed the current outburst is brighter than previous normal ones, but still the whole magnitude fainter than the superoutburst. I will explain what's going on with DDE 48 during the supercycle using the rocket engine analogy. During the supercycle, the red dwarf is fueling the accretion disk around the white dwarf. Normal outbursts are like "fuel dumps" occuring every 3 days. Let's imagine the "fueling" rate to be 0.1 critical mass per day. After the superoutburst the disk is exhausted. Assume it's 0% fueled. In 3 days we get +30% of full load, and then first normal outburst (NO1) "dumps" 10%, down to 20% of critical mass. By the Day 6 we have 50% of full load, and then second normal outburst (NO2) occurs, taking away 10% (down to 40%). By Day 9 we have 70%, then NO3 occurs (down to 60%). By Day 12 we have 90% of critical mass which is almost enough to trigger the superoutburst. That is why the 4th normal outburst (NO4) is brighter than NO1-NO3! Day 12 in the current supercycle occured on July 22/23.
Now the exact date of the superoutburst (SO) depends on the amount of "fuel" left in the accretion disk after NO4. If it is 70% of critical mass, the star will reach the maximum in 3 days (Day 15 of supercycle, which is July 25). But if the "fuel tank" is 75% or 80% full, it will explode earlier, just in two days. And we cannot know for sure if it's 70, 75 or 80 per cent! That's why I'm saying we are in the most interesting phase of the light curve right now.
Denis, thank you for your very interesting explanations. We will carry on the monitoring every night, with permission of the clouds.
At this very moment, DDE 48 shines of mag. 18.0 CV ( JD 2457959.3863), very faint, in the limit of detection (S/N=3).
Greetings
Fran
La V/C MASTER OT J204627.96 sigue muy brillante; he obtenido una curva de lus de 2 horas de duración, con un posible hums.
La DDE 48 está en 17.90-18.03ª
Las seguiré el rastro.
Teófilo
La V/C MASTER OT J204627.96 sigue muy brillante; he obtenido una curva de lus de 2 horas de duración, con un posible hums.
La DDE 48 está en 17.90-18.03ª
Las seguiré el rastro.
Teófilo
I'm following both variables in photometric V and pretty picture Lum (since I don't know what "unfiltered" means). I was able to send my V reports via VPHOT and WebObs but even though the Lum subs are being accepted by VPHOT, naturally and predictably it won't create observation reports for LUM science images.
Do you guys want/need the LUM science images, if so I can place them on a dropbox link. Also there's no way that I can get an SNR of 50 in 90 seconds with the Johnson/Cousins V for DDE 48 so I have been uploading to VPHOT and stacking 3 subs at a time to get an snr of 23. Do you guys want me to continue monitoring DDE 48 at a cadence of 90 seconds max or do you want me to go to 300 seconds where I can really get some great snr?
Hello Pablo!
Please upload Luminance images to Dropbox and post a link here. I will download and process them.
As to exposure time, please keep it at 90 seconds. MASTER OT is currently at 15.1-15.3m, and long run by Dirk Cornelis shows the superhump period of 0.0629(1) d. DDE 48 will brighten to 15.3-15.4m in superoutburst, too. It should have a short orbital period as well (about 90 minutes), so 5-min exposures will be too long. It is better to have 30-40 points per period than just 15.
Thank you, and Clear Skies!
Here you go Denis, these are 90 seconds subs, calibrated BDF with Astroimage J and plate solved with Pinpoint. I will keep gathering data on this star for the next few days.
glad to be of help!
Best!
https://www.dropbox.com/sh/079itatgcb624d7/AABxaayU4lRYItjlGRTqThiHa?dl…
I will reduce and submit the V filter to WebObs, here are the LUM in case you still need them.
https://www.dropbox.com/sh/vnfgt2oxkyyjhmd/AAC5_FvotXFUQRw-qnYynjkVa?dl…
Tonight will be the 4th night in a row to image DDE-48 and the Master OT. Using my 40cm f4.5, a red filter and a FLI6303e and keeping the subs at 120 seconds. The telescope is only active since a good month at E-Eye in fregenal de la sierra but it is generating data at a nice rate. While I do like people making beautifull images, I do not even have RGB in the filterwheel, currently Ha, O3, Red, CLEAR(UV and IR pass) and an SA200 grating to make primitive spectral observations.
Hi,
today the sky is clear. At this moment DDE 48 is brighter: 16,4 CV (JD 2457961.37831). I'm taking 150" exposures with a S/N close to 20, unfiltered....
Greetings
Fran
Currently also running exposures, doing 120s with Red filter on the 40cm f4.5 in Fregenal De La Sierra.
Currently sending my data from last night a mostly complete run of 120s R images. A few 180s in the beginning but then noticed DDE48 had brightened and switched back to 120.
Looking forward to you measurements and conclusions, the peak came about the time you predicted.
D.
Thanks a lot Dirk! I got all the images. It takes hours to process them all. In parallel with analysis of two CVs I am preparing the details of eight new variables from your data for submitting to VSX. One of them had a crazy light curve (bump right in the middle of two eclipses), but that turned out to be the effect of two different hot pixels in two nights...
As to DDE 48, it has not yet reached the maximum! The superoutbursts should be 15.3-15.4m, and the star is currently at 16.3m - the whole magnitude fainter than the peak brightness. So far, MASTER OT is stealing the show with very nice, large-amplitude (~0.25m) superhumps.
I uploaded last night's MASTER OT and DDE to Web Obs just now. DDE 48 is getting brighter at 16.1 to 16.2 and MASTER OT at 15.6 to 15.7
Best!
Got a snapshot from iTelescope T30 in Australia at 13:35 UT (23:35 local time). DDE 48 was at 33 deg elevation from Siding Spring. Here are the latest magnitudes from my data (unfiltered with V zero point):
DDE 48
2017-07-25.222 18.07 ART (Tenerife)
2017-07-26.411 17.58 T21 (Mayhill)
2017-07-27.007 16.31 ART (Tenerife)
2017-07-27.567 16.28 T30 (Siding Spring)
The star was rising at a rate of 2.0 mag/day, then it suddenly stopped at 16.3m! What's that? - I don't know. Might be a plato before the superoutburst, or might be *another* normal outburst. Those CVs are sometimes unpredictable and fail to conform to our expectations. I will be disappointed, but not surprised, if it goes back to minimum the next night!
Hi Denis, last nights data is on its way to you!
Looking forward to info and positions on the other variables.
Kind regards
Dirk
Hi,
I am sorry, but I don't have good news. At this moment DDE 48 is close to the minimum: 17.9 at JD 2457963.37761
Maybe the next night...
Greetings
Fran
Indeed Francisco, I could barely detect it without zooming in to my data, I continue the campaing so Denis can get more data on master OT next to it. For me this is a serious learning experience. I need an automated tool to get to analyse more of my own data.
I'm seeing about V=15.9 from data on JD 2457965.816, measurement SNR is about 100. MASTER OT is about 15.85.
DDE 48 maybe is going into superoutburst. At this moment, CV=15.8 on JD 2457970.358.
Unfortunately, there is near Full Moon. The S/N and cadence are low. I will continue observing the next hours but tomorrow I'm going to holiday, so the next week I won't be observing at all. Sorry, I will upload the data after coming back holidays (7-8 days).
Greetings
Fran
I can take over from Frenegal!
DDE48 bright! and master OT barely registering at 120s with the 40cm in red. Fli-6303e cam.
Dirk.
Before I'm going into holiday, I upload the observations of the last night. Interesting the strong oscillations during this supermaximum. I hope they will be useful.
Greetings
Fran
Hooray! We've got a superoutburst after all!!! Your perseverance has finally persuaded the star to go to supermaximum! :-)
Your graph is obviously showing the superhumps, and the period is close to 0.066 d (about 1.6 hour).
Thanks a lot for following the star going up and down and up again! And for fighting the Moon as well! Great job you've done!
Have a nice holiday, and come back soon!
Denis
Dear all,
As you see, Francisco Campos and Dirk Cornelis have caught the star in the brightest state since the beginning of campaign (actually, since June 25)! Superhumps are clearly visible, and amplitude is large enough.
My first estimates of the supercycle length were premature. Now we can say the interval between superoutbursts is 45 days rather than 36, and there are SIX normal outbursts between the successive super ones, not four. 45 days is consistent with the long-term light curve by ASAS-SN which is only detecting the superoutbursts (some to 15.2m, some to 15.4-15.5m).
Also, thanks to rather dense coverage in last two weeks, we have a very good pattern of normal outbursts. If you look at AAVSO Light Curve Generator, you will see peaks getting higher and higher with every next normal outburst (NO). The star is "pumping up" by ~0.2m with every outburst, until it goes to the superoutburst (SO). Peaks of NO2 and NO3 were missed (they had occured on July 16 and 19, before the campaign was announced), but we can guess their magnitudes by interpolation. It looks like this:
NO1: 17.0m NO2: 16.7m NO3: 16.4m NO4: 16.2m NO5: 16.0m NO6: 15.8m
What's next? The continued time series are especially needed now. The goal is to follow the evolution of superhumps through the superoutburst. There are good data about ER UMa itself from 2011-2012 campaign, but every star has its own peculiarities. It will be most interesting to see how the period and amplitude of superhumps is changing with time, and how the behavior of DDE 48 compares to that of ER UMa.
Please continue the observations, and switch to all-night-long time series, if you haven't started them yet.
Thanks, and Clear Skies!
Denis
Hi denis, I sent again some data from last night, need to send you second part of the 9th.
Tonight hopefully another good long run, DDE48 keeps to be reasonably bright.
I lost 2 nights in the beginning of the week due to weather.
Kind Regards