Affiliation
American Association of Variable Star Observers (AAVSO)
Tue, 08/19/2014 - 12:49
Hello
I Got another run on EE Cep last night/this morning. Its still fading. In fact, it took a sudden increase in slope two days ago. Its now fading faster than at any time during the Campaign. The TOM (Time of Minimum) is predicted for JD 6890.83--late Wednesday night or early Thursday morning. I plan to capture it, weather permitting.
Gary
Hi Gary,
I'm setup to capture four sets of BVRI images throughout the night from iT21, best I can do based on other scheduled runs. Hopefully they will help to time the minimum.
Thanks,
Brian
Hello Brian
Thats good news. We need full weather and longitudinal coverage. I realize that TOM will be computed based on the light curve other than at TOM, but its just kind of a challenge to see it.
Gary
Hello
I should mention that Cezary Galan's web site uses a different Ephemerites which give the TOM on JD 6893.44. Thats Friday night, EST in Lay Time.
Gary
Just posted BVRI data from a run earlier tonihgt. EE Cep appears to be still fading.
Michael
Hello Michael
I ran until 5 am this morning. Still no sign of a turn around. TOM may be tonight?
Gary
Hello
I have been studying the light curves for EE Cep. Lots of good data there. If I plot 50 Days on the X-axis and 11-12th mag on the Y axis and look at B, it almost looks like 3 pronounced slopes, rather than a curve.
1. First from JD 6790 to JD 6872 is a gentle Slope, Call it Slope1
2. There is a break at JD 6872 fading faster to JD 6886, quite pronounced Slope2
3. There is another break at JD6886, fading to JD6888, call it Slope3.
4. There is also a hint of a break between JD 6888 and 6889. Could it be bottoming out? Tonight should tell.
Surprised at the quasi-linear plot of the brightness. This holds up in the other colors, when plotted with similar range on the Y axis. Could it be several disks? or a single disk with sharp changes in opacity/optical depth? More to come. Keep up the observing. Any explanations?
Gary
A few minutes ago I could take some images of EE Cep: 2456890.46404 = 11.434 V. Added to the AAVSO database.
Regards,
Juan-Luis
Hello
Got EE Cep at 11.45 average by eye last night. Still fading, but its clearly turned the corner at the bottom. Not sure if it has gone thru the Min yet. Tonights data (JD6892) will tell us for sure.
In fact, my B and I time series show a slight brightening, but that is not supported by the V and R light curves. This may just be residual extinction or other local condition, as all data is Transformed.
Gary
Hi,
Yesterday my last series (6891.50854) was at 11.433 , tonight (6892.38032) I got 11.448
Observation ended due to clouds, not sure tomorrow will be possible.
A very poor summer this year here in western Europe !
Clear Skies !
Roger
Afew minutes ago I took CCD V images. It seems stable tonight with respect yesterday. Is the TOM?
Regards,
Juan-Luis
I got these (non-transformed) data for the 22-Aug-14 and 23-Aug-14 (UT) nights:
2456891.8936921298,11.493,0.003,V,
2456892.9228703706,11.523,0.012,V
Last night was not so good as I got clouds. Will upload BRI when I get back from work.
James
Measurement of tonight (CCD V): 2456893.48934 11.4994V 0.0105
Regards,
Juan-Luis
Same here, mag increase of about 0.03 from yesterday, it seems the slope gets even more pronunced !
I was nor expecting observation tonight, sky was 100% cloudy, but near 2 am clouds suddenly went and left a nice dark sky !
Clear Skies !
Roger
Watching this with facination..
We only get clear nights from time to time but I got another look last night with my 14 inch dob.
It has faded even to me as an amateur observer...
Definitely fainter than those two mag 11.2/11.3 stars and more like that 11.9 one nearby.
I put my observation on here at 11.8.
I am normally a galaxy man but this is an interesting diversion.
I gather it brightens more quickly than it fades looking at the last curve!
Regards
Mark Stuart
Just did another run. In 24 hours it went from Vmag 11.482 to 11.512 +/- 0.004. I did BVRI and posted in WebObs.
Michael
Hi,
Just looking more carefully at the 69, 75 and 2003 light curves I just got the following ephemeris:
12794.545455 - 2050.272728 x E (from 2003)
and a forecast of TOM on 6895.09091 that's just today afternoon (here) or 2014/8/25 14:11 UT
What do you think about that ?
I would probably not be able to check: a lot of clouds here tonight !
Clear Skies !
Roger
Everyone is Soooo anxious about this! This is not like two stellar disks occulting each other. But, a diffuse dust cloud. We have a good crew watching it. It will happen!! And probably soon?
Ken
Hello
It looks like EE Cep has gone thru TOM. I have had 4 days in a row from dusk to dawn. Reducing the data for TOM. We will need the brightening leg of the curve to do a proper TOM, as I understand the method--thou I have never done one myself. Perhaps a Epsilon Aurigae or other Binary observer can comment. This data should also allow the search for modulation near minimum. I am at my remote observatory, and while I have internet access, cannot log on to AAVSO web site. Will has been working the issue. Two computers do the same thing. These same two computers work fine when I get back to home. Very Strange. All other sites work. I can do my online banking, etc. Any Suggestions?
So I cannot post my data until the end of the week, and I cannot post reply's on the Forum. I am currently coming to you from the local public library.
So keep those observations coming. The second half of the eclipse is just as important as the first half. Thanks everyone for observing for this campaign.
Gary
EE Cep seems to have gone through TOM (time-of-minimum) sometime late 24-Aug-14 to early 25-Aug-14 UT date. Here's what our data (15-Aug-14 thru 27-Aug-14) seem to indicate:
<<
By 15-Sep-14, EE Cep's eclipsing event should be over and the TOM can be determined with higher precision. Happy EE Cep eclipse and labor day!
James
I use 112 113 117 119 as my ensemble since the beginning of the campaign. Until yesterday night they looked very stable and having a very good fitting with the chart values, within a few mmag ! A very good ensemble... 112 and 113 have been suspected variable but show very stable (104 seems less stable).
Tonight surprise: large error ! The obvious reason was 117, it has dimmed by 0.120 mag. It was ok within mmag yesterday night. The 0.120 dimming has been stable from 6903.38636 to 6903.44686 . Got back to 0.051 by 6903.50773.
My software surveys about 50 stars of that EE Cep field, nothing unusual in those data.
Clear Skies !
Roger (PROC)
Hi Roger,
It turned out to be variable indeed.
It is a B8V star and there is a period of 0.961 d. present. It might be a SPB star or it could be a periodic Be star. It looks too red for an SPB and there is some suggestion that the color gets redder when it is bright (The GCPD lists a measure V= 11.56 with B-V= 0.27). But there are not enough observations to be sure.
The recorded range is 11.57 (or 11.56 if we count the above measure) - 11.69 V from APASS but if it is a Be star then the range could be larger.
We should delete it from the sequence.
It is now in VSX as TYC 3973-2396-1
Cheers,
Sebastian
Hi Sebastian,
thanks for your answer.
Yesterday I ended the observation near 4 am, and 117 got back to normal ( within 5 mmag) on 6903.57033.
My impression is the light curve looks like a transit one, with a flat top and a fast transient to normal. I will show it tomorrow (too late now, sleepy !) Is it compatible with an SPB or a periodic Be ?
No way for another observation tonight, a lot of clouds...
Clear Skies !
Roger (PROC)
I have been following EE Cep with iT 7 in spain and getting fantastic results. I went back and examined star 117, or TYC 3973-2396-1, over the period of the past few weeks. I get the same dip in brightness reported above on Sept 2 around midnight when I took photos through VBR filters. The B and R filters show a 0.06 mag dip, and the V filter shows a 0.08 mag dip. The previous day and next day show normal magnatudes. I have been trying to find an error and could not, then I saw the above and decided it might not be an error.
Frank
Hi Frank and Roger,
What you say doesn't seem to fit in in a picture of an SPB or periodic Be star.
The NSVS light curve doesn't suggest the presence of eclipses though (which is what your observations seem to imply).
It would be interesting to follow it as long as you can.
All the observers can now submit their data to the AID since the star is in VSX.
Having all data in one place would make further analysis possible.
The NSVS light curve shows variability in the short-term not only eclipsing-like events superposed to a constant magnitude, that is the weird part, but after Patrick Wils' suggestion that the period could be spurious I looked at other nearby stars and it seems that this field shows too large scatter in NSVS. There are other stars showing 0.2 mag. "variations".
However, the literature shows brighter magnitudes (not fainter ones) so something might be going on with this star.
I though about the HAeBe possibility, with the star showing some irregular dips from time to time due to moving clouds, but the J-K color is not consistent with that.
So it might be that the NSVS data are showing scatter and it is an eclipsing binary.
Only lots of observations will allow us to know for sure so sublit all the data you have from this campaing to the AID!
Cheers,
Sebastian
I uploaded my 30 images (V). Looks like I caught two minima in July.
I submitted more data on the 117 star today, from July, that shows a recovery from dimming. I still have a few nights data from July to process.
John Centala, CQJ
On 6907.31205 I got a new dimming at start of my observations, it was already at +0.106, I don't have the ingress. Then the dimming remained stable at +0.110 and started brightening on 6907.34597 ( +0.093). I have not been able to continue to observe after that point.
I have a lot of images, about 1600 since July, and a good set remains to be processed, I hop I will be able to report it all within a day or two. I have seen something that could be some transient point in July, 6855.38567 in a single series. Another one in August (6889.34727 ) looks like the end of a dimming, I got it at start of my observation, at 6889.3977 it was near to normal.
Clear Skies !
Roger (PROC)
Hi all,
very interesting.
Please submit all your data when you can.
Patrick Wils already analyzed what was available a couple of days ago and found a period so this is very likely a small amplitude eclipsing binary. The scatter in all sources might be only intrumental then.
Your data will tell.
I would wait a couple of weeks to have more eclipses so a better period can be determined.
Cheers,
Sebastian
I have also used the star 117 as one of the comparison stars. When transforming some observations made in September, I have removed it from the set of compstars, because with it and without it the uncertainty of B and V is quite different: ~0.05 0.05 -> 0.008 0.010 or so.
At the same time, in the end of July and most of the August, star 117 was fine (or other 3 compstars changed in opposite direction ;-) ).
I have a most of my transformed images still available in VPHOT in case something has to be changed. So I could also help to sort the issue with 117 out.
Edit: added graph of my observations of that star.
Hello
I looked for the 117 comp, and it seems to be visible on a "D" chart I believe, and not on a "F" chart. Can you confirm about how far the 117 you are talking about is from the target--just eyeball distance.
Thanks
Gary
The 117 comp star is about 8.3 arc-minutes south of EE Cephei.
John Centala
Gary, also note that the 117 is no longer identified. Since it appears to be variable, it was removed from the chart. It should be pretty obvious which of the southern stars it is when you check its V magnitude on your images.
It is TYC 3973-2396-1 in VSX, with coordinates 22 09 40.86 +55 37 27.4 with V=11.6 and (B-V) = 0.17 and is to the SE of EE Cep. It will be identified if you turn on the mark all variables option in VSP.
Arne
I just tried to fold my data, using previously proposed period of 0.96138 days (taken from VSX) to create a phase diagram. It doesn't seem to be very close to the actual one, at least not something resembling an eclipsing (or pulsating) variable star lightcurve.
Unfortunately when I tried to use PDM on existing AAVSO data + my own data, it was not enough to find anything conclusive.
Just looking at the data, the period of the 117 star appears to be about 3.87 days. I'm sure someone could do a rigorous analysis to refute or verify and refine this.
John Centala
Hi John,
From my observations the period should be 1.2846 d . 3.87 d is just a multiple of it, very interesting ! We are on the same path. The next days occurences should be:
6912.4504 6913.735 6915.0196 6916.3042
I am on trip until monday, I can't observe. My next here in Burgundy should be 6916.3042, not sure the sky would be ok...
Clear Skies !
Roger
[quote=CQJ]
Just looking at the data, the period of the 117 star appears to be about 3.87 days. I'm sure someone could do a rigorous analysis to refute or verify and refine this.
[/quote]
The best estimates I got were also somewhere between 3.83 - 3.85 days.
When I tried the period 1.2846 d, it did not fold all the AAVSO data... Seems that we need two well defined TOM :-)
Tõnis
Using all the published data I get an ephemeris of
HJD_MinI = 242456357.13(2) + 3.8745(1) x E
The minimum is well defined by a dozen or so points but there are some discrepant points at other phases which may lead people astray if they are just looking at the faint points. There is no sign of a seconday eclipse at this period. Half the period does not work, but of course twice ths period does, giving two practical eclipses. If any difference between alternate eclipses can be found then that would argue for the double period. As more observations become available then this may become clearer and time series data around the minima would help.
Regards,
Chris Lloyd
I have now had a first look at the B data which although it is much noisier than the V data confirms the period. Times of minima over the next couple of weeks are...
HJD_MinI = 2456357.127 + 3.87452 x E .........................just the one 24...this time
JD Year Mon dd hh:mm UT I/II Cycle
2456915.0585 2014 Sep 14 13:24 14.5585 I 144
2456918.9330 2014 Sep 18 10:23 18.4330 I 145
2456922.8075 2014 Sep 22 07:22 22.3075 I 146
2456926.6821 2014 Sep 26 04:22 26.1821 I 147
2456930.5566 2014 Sep 30 01:21 30.0566 I 148
Christopher,
Thanks for the ephemeris. Weather permitting, I will try to observe the start of the next eclipse on the morning of Sept. 18.
John Centala
The transit shows a long flat bottom, about 4 hours from my long series on JD 6903. I am missing the true ingress, then fitting the data with published observations I got some confirmation of that estimate, but I can't exclude it's even longer !
Due to such flat bottom the folding of a few observations of single or a few points per transit results in a large uncertainty. I did a fitting of the partial shapes of various observations to my long series and I got the following estimate:
JD: 6895.6768 + 3.865 x E (starting from the first observation that I can fit)
We need at least a full coverage of the transit to better understand it, not easy as the total transit spent at least 8 hours.
Clear Skies !
Roger
Integrating more data from John (CQJ), in particular four points of the roll-off of the transit that just fit my full roll-off on 6903, I got a much more accurate period: 3.8684. The details are in the attachement. The blue curve is a fifth order fitting of the data, it has been used to determine the mid-transit and width. The periode has been adjusted to minimize the RMS error of the fitting.
No new observation here, the clouds are back !
Clear Skies !
Roger (PROC)
I propose to move that discussion to a new topic:
" TYC 3976-2396-1 Transit LC "
It should be a better match as this topic here was originaly dedicated to the EE Cep dimming.
Roger