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Campaign on b Per eclipse - Alert Notice 688

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weo
weo's picture
Campaign on b Per eclipse - Alert Notice 688

AAVSO Alert Notice 688 announces an observing campaign on the very bright, triple-star eclipsing system b Per beginning in early January. Please see the notice for details and observing instructions.

Many thanks, and Good observing,

Elizabeth O. Waagen, AAVSO HQ

weo
weo's picture
URL for b Per campaign fixed

The URL for this forum thread has been fixed. My apologies for the error!

Best wishes, and Good observing,

Elizabeth

cdk
Good data

I am very pleased to see the good data on b Persei coming in to the AAVSO to help establish the good ellipsoidal baseline in anticipation for the upcoming primary eclipse.  It is also good to see new observers to the campaign!

Let me emphasize that at this stage it is important to obtain several nights of runs of several hours a night to establish a good ellipsoidal light curve before and/or after the eclipse. 

I also wish everyone good weather during the 4 days centered on the eclipse (UT Jan 17.5 and UT Jan 21.5 = N. American nights of Jan 16 to Jan 20).  If we experience "partly cloudy" conditions on those nights, I encourage observing "between the clouds" to salvage any clear windows of observations.

I will soon post a predicted light curve for the primary eclipse as I had done for the last eclipse of November 2018.

Good observing!

Don (CDK)

weo
weo's picture
b Per is NOT beta Per

Hi Everyone,

Just a reminder that b Per, the target of this campaign (AN 688), is NOT beta Per (Algol). There has been some confusion, so I thought I would clarify.

Thanks, and Good observing,

Elizabeth

cdk
b Persei predicted Light Curve for Jan 2020

Hello Observers,

I recently finished calculating the expected light curve for this month's primary eclipse of the close-orbiting A and B components of b Persei by its third star, the C component.  We owe many thanks to AAVSO observers who contributed to the previous five highly time-resolved eclipses and to those observers who observed the first ever eclipse of this fascinating system in 2013.  By extrapolating the ephemeri (for both the C star's orbit and the inner A-B close orbiting stars) I have fairly successfully predicted the light curve that we verified by observing the November 2018 secondary eclipse.  I've now "stuck my neck out" and predicted the upcoming eclipse shown in the accompanying figure.  The timings may be in error by as much as 0.1 day.  The first dip is shown to begin at JD 2458866.5 (Jan 18.0 UT).  That is "prime time" for European and N. American observers.  This expected dip is a partial occultation of the fainter B star by the third star.  The simulation then shows the ingress occultation of the brighter (and larger A star) by the third star that shows a much deeper dip in the light curve.  The simulated light curve shows the results for the C star fully ingressed over the approximate center of the brighter, larger A star.  The curve continues as the C star passes the CM of the AB pair and re-ingresses the A star on the other side of the A star's orbit.  The large major dip is then followed by a moderate dip as the C star almost fully covers the B star (the C and B stars are assumed the same size and brightness in this model.  Finally there is an expected grazing occultation at JD 2458869.5 (Jan.21.0 UT) which will be a challenge to detect.

A word of caution: These simulations are only a guess as to the solutions of the b Persei system.  My model only has concentrated on the timings, the angle of intersection of the AB orbit with the sky, and the dates of mid-eclipse.  The model has not experimented with the sizes and luminosities of the three stars involved so the depths of the occultations may be sizeably different.  At each eclipse we learn more about the b Persei system.  Many thanks to all of you for participating!

I look forward to another successful observing campaign.  Clear skies, everyone.

Don (CDK)

 

perdiguero
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Ready... with permission of the clouds.

Hi, all,

telescope and CCD ready for V-photometry (and B if you want) in South Europe. This next week I will run some observations pre-eclipse. But forecast at this moment seems compromised, after some weeks of good weather. Hope this prediction will change to better...

Greetings,

Fran

cdk
Glad you're ready

Fran, Glad you're ready if the clouds break.  I am doing B as well, and so are some others.  B would be good also, but the primary mission is V.  Thanks,

Don

cdk
Visual Observations

I am pleased to see a number of visual observers participating in the b Persei campaign.  The quickness of making visual observations should help tremendously in the presence of frequent clouds.  The maximum depth of the upcoming eclipse is expected to be on the order of half a magnitude, well within the sensitivity of the human eye - especially if each visual observer observe as much as possible throughout the nights. 

Good observing!

Don (CDK)

cdk
Expect eclipse to begin tomorrow

Hi Observers, Our long-awaited primary eclipse of bPer is expected to begin tomorrow night (Jan 17-18 local times - about Jan 18.0 UT) with a "small" dip as the third star is expected to eclipse the faint B component.  The brighter A star of the A-B pair is expected to be transited the next night.  Shoot between the clouds....

We've been pretty clouded out in the southeast US this past week.  I shot between the clouds last night and posted my results.  Pretty poor, but consistent enough to discern that no eclipse was happening.

Good observing, everyone.  Keep the data coming, were getting pretty good European and N. American coverage.

Don (CDK)

perdiguero
perdiguero's picture
Hi,

Hi,

as soon as the night has begun, I started to do B and V photometry. The star is a bit dim... Maybe I'm observing the small dip. Today the sky is clear but for very few time: the forecast is terrible for the next seven days, so I'm afraid that only today I will be able to provide data.

Greetings,

Fran

chrismlt
Hi all,

Hi all,

 

It's raining cats and dogs this evening over south-east of France.

Tomorrow should be better, but the weather prospect is still uncertain, and the quality of the data - if any - won't be at the best, probably.

Sorry,

w&s

Christophe

cdk
Cloudy in North Carolina - southeast US

I got good data for last night (JD 865) but tonight (JD 866) it looks hopeless for the expected small dip that is expected.  Take any clear sky - even if only for 10 minutes.

Good luck everyone!

Don

Bikeman
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Hopeless near my spot in

Hopeless near my spot in Germany...rain even...

CS

HB

 

WGR
WGR's picture
Potential Eclipse 20200104?

Hello All

I found a potential eclipse, but on the night of 0104.  I know that is too early.  Thought I would post anyway to pass the word.  Others may look back at their "ingress" more carefully as a result and get corroborating data.  The data on AID is the raw data, 2 sec exposures in V, 20 inch, defocussed 3000 microns, Sierra Remote Obs.  The attached plot is binned x10 to take out scintillation.  The error bars are STOM for the Target and the Comp Star--should be conservative.  No images were edited out.  By editing out a few images, I can see that the error bars could be reduced.  The night in question is the binned result of 50 images.  The plot is for 5 nights.  Other nights were clouded out.  Your Thoughts?  Questions welcome.

cdk
Potential eclipse?

Gary, the time-axis on your figure you sent is confusing.  The time-axis title ("20191230-20200115") looks like calendar days.  The numbers along the time axis are 0 .. 45.  These numbers don't make sense with your date of suggested eclipse of "0104" which I interpret with Jan 04.  Can you please explain?  - Thanks.

Does the "SDOM M + C Quad" your notation for Stdard Deviation of Magnitude = the std dev of object and comparison added in quadrature?

By any chance, were these were last night's data (night of Jan 17-18)?

Don

perdiguero
perdiguero's picture
Hi,

Hi,

here are the results of the last night. The eclipse began as scheduled, but clouds appeared at 1:30 UT. Well, that's not very bad because the star was already quite low. These points are 120" exposures but I tried also to promediate every 3 points in order to reduce dispersion. I have also photometry in Johnson V (similar results).

Don, in order to upload the photometry, please tell me if you want the single points or you prefer the 3 points average.

Greetings,

Fran

cdk
Ingress detected by Fran Campos!

Fran's 4 hour light curve in B clearly shows the ingress to the eclipse that we attribute to the C star beginning to transit across the orbiting B star.  The time of the beginning of the dip in brightness of Fran's light curve is JD 2458866.48.  That is about 0.08 d (~ 2 hr) before the calculated date in the predicted curve I recently posted.  Congratulations to Fran for being the first to report the onset of the predicted transit!

Further support for detection of ingress is the fact that at the time of the beginning of the drop in brightness corresponds to close to the minimum light of the ellipsoidal light curve where the normal light curve would begin to increase in brightness.

Congratulations on these data just before impending clouds!

Don

perdiguero
perdiguero's picture
Towards a second minimum

Hi,

this night the sky is cloudy. Before this I captured some images: the star is faint (mag. 4.8) and fading (19h UT), so we are going to a second minimum. Damm weather! Now the time has come for the US people. Good luck!

Fran

chrismlt
All,

All,

I'm on the target since 17h30 UT. I begun acquiring data only one hour after sunset in a still blue sky.

Now the night is cristal clear. Unexpected, but useful.

Data tomorrow.

 

W&s

Christophe

chrismlt
The star, that was easily

The star, that was easily seen to the naked eye after sunset, is now somewhat difficult to see in direct vision, maybe around mag 5.0 (I'm not a specialist of visual estimation).

Well, I would say your timing is pretty good, Don. Well done !

Cheers.

 

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