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Alert Notice 700: EE Cep observing campaign 2020-2021

Note: The eclipse of EE Cep began earlier than predicted. Dariusz Kubicki reported on 2020 February 28 that "there is no doubt the eclipse has begun; my observations confirm" reports from observers. Please continue to monitor EE Cep as described below.  -  Elizabeth O. Waagen, 2020 March 2

February 24, 2020

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
- Campaigns and Observation Reports: https://www.aavso.org/ee-cep-observing-campaign-2020-2021
- Eclipsing Binaries: https://www.aavso.org/ee-cep-observing-campaign-2020-2021-01
- Spectroscopy: https://www.aavso.org/ee-cep-observing-campaign-2020-2021-02

Dariusz Kubicki (Nicolaus Copernicus University) has requested AAVSO observers' assistance beginning now in monitoring the long-period (5.61 years) eclipsing binary EE Cep for a campaign that he has underway. This campaign is in two parts, first for the eclipse itself occurring over the coming months, and second for follow-up to begin in December 2020.

The next eclipse (Epoch E = 12) is scheduled for 2020. Kubicki writes: "The beginning of the ingress will take place around the 7th of March (JD 2458916), the mid-eclipse is predicted on the 3rd of April (JD 2458943.2), [and] the end of the egress is expected on the 21st of April (JD 2458960). It is recommended to start observing at least two months before the mid-eclipse and continue at least two months after the mid-eclipse. All photometric optical (UBVRI) and especially infrared (JHK etc.) data and spectra will be useful.

"Before the ingress one or two measurements during the night will be useful, whereas during the eclipse we count on the highest possible time resolution of observations.

"Special attention should be paid also about one year later, around ϕ = 0.2 of the orbital phase, i.e. 20th of May 2021 (JD 2459354). In the previous epochs at this point of the orbital period, an increase of the near-infrared IC flux was observed (Pieńkowski et al. 2020). We recommend to carry out the observations between December 2020 and November 2021. Observing in Johnson-Cousins RCIC system with accuracy of 0.01 magnitude or higher is advised. Near-infrared J, H, K photometry would be particularly useful." Visual observations are also welcome.

Kubicki has a website for this campaign (https://sites.google.com/site/eecep2020campaign/). On it he includes figures showing photometry from previous eclipse campaigns. He also includes a finder chart to be used to observe EE Cep. The comparison/check stars on this finder chart are summarized in the table below.

Kubicki requests that BD+55 2690 (star 'a' on his finder chart) be used for comparison. This star is the 104 in the AAVSO sequence for EE Cep. He also says that "Observing stars 'b' GSC 3973:2150, 'c' BD+55 2691, and 'd' GSC-3973:1261 is also advised as the check stars to verify the variability of these stars." GSC 3973:2150 and BD+55 2691 are NSV 25842 and NSV 25843, respectively, but they are both Constant (CST) (see table).

A finder chart may also be created using the AAVSO Variable Star Plotter (VSP). However, please be sure to use the comparison stars on Kubicki's chart.

label Name (finder chart) Name (other) RA (2000) Dec (2000) Mag
a BD+55 2690 104 in AAVSO seq for EE Cep 22 09 08.032 +55 47 15.49 10.397V*
b GSC 3973:2150 NSV 25842 (type CST) 22 09 01.696 +55 45 31.06 11.25V
c BD+55 2691 NSV 25843 (type CST) 22 09 15.466 +55 44 48.43 11.25V
d GSC 3973:1261   22 09 23.3592 +55 42 14.148 11.88(0.32)P

* 10.397V is Kubicki's magnitude; 10.399V is AAVSO magnitude

EE Cep has a range of 10.72 - 12.15 V.

"Spectroscopic observations with high resolution (R~10000 or higher) are also recommended. Observing Hα, Hβ and Hγ lines and ion Na I doublet for analysis of line profiles will be useful. In the case of spectrographs with low-resolution flux calibration will be essential to make them useful in analyses.

"Please send the reduced data to Dariusz Kubicki (kubickid@gmail.com). Please attach information about your institution and photometry or spectroscopy systems."

Spectroscopy reports should also be submitted to the AAVSO Spectroscopic Database (https://www.aavso.org/apps/avspec/).

Photometric observations should be submitted to the AAVSO International Database using the name EE CEP.

Coordinates for EE Cep (2000): R.A. 22 09 22.75  Dec. +55 45 24.2

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen using material provided by Dariusz Kubicki.
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