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CE Tau Observations Requested to Supplement BRITE-Constellation

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bpablo
CE Tau Observations Requested to Supplement BRITE-Constellation

Hey Everyone,

This post is in reference to Alert Notice 602.

My name is Bert Pablo and I'm the new staff astronomer at the AAVSO. While many have probably heard my name here or there I haven't had much of a chance to interact with you as a group. I'm active in a lot of different projects, but one of my main collaborations before joining the AAVSO (and even now) is the BRITE-constellation project. This is a network of 5 nanosatellites (3 with a red filter and 2 with a blue filter) designed to look continuously (~ 6 months) at the brightest stars (V< 6) in the sky. While it may seem a bit counter-intuitive these stars often have very poor photometric coverage because they are so bright that they saturate very quickly on even small telescopes. As such BRITE has already given us unique insights on several stars that we thought we understood (like this shameless plug for my own research: https://phys.org/news/2017-03-iota-orionis-pulsating-beacon-constellatio...). 

BRITE does a lot of things well, but it has limitations. For one it was not designed for long term monitoring. It can observe for 6 months at a time, but save for a handful of stars, the observations are not repeated regularly. Additionally, while it observes stably, timescales longer than about a month are tough to disentangle from instrumental variability. These are areas where the AAVSO and it's community of observers excels and as such a collaboration can be very beneficial for the right targets. 

A perfect place to start is the red supergiant CE Tau. This star has a V mag of ~4.3 and is known to have long scale variations from AAVSO data of ~165 days which is roughly the extent of the BRITE observation and therefore hard for it to track. What's more this object is already a PEP target and has a good time base over the last couple of years already built up, so we are starting from a place of strength. Plus, as the variations in this target are significant (~0.5 magnitude), it is not limited to PEP observers. It is also a superb long term monitoring object for CCD and especially DSLR observers. Since BRITE is handling any short term variability, the goal for the AAVSO community is to get a better picture of the long term variability so 1 observation per night or even every few nights will be more than adequate. 

It's important to point out that while the project is well defined, the end result is impossible to know. We are embarking on an adventure here, studying an object from a class that is short-lived (from an astronomical standpoint) and not well understood. We are looking at a tiny but crucial snapshot in the life of one of the most massive stars in existence and are hoping to understand just a little bit better what makes it tick, and how it will evolve from this point forward. Instead of calling this a campaign, it may be more apt to call it an expedition as much of this remains a mystery.

BONUS!!!

If you are taking DSLR photometry (or just have a very wide field of view) you are in luck as this particular project takes full advantage of your capabilities. Not too far away (~20 arcminutes) lies another BRITE target V960 Tau. This star is a mystery. It's a Be star that has significant variability that was noted in Hipparcos and ASAS, but little else has ever been done with this. Currently, it has exactly 8 observations in the AID that also don't tell us much. It likely has low level pulsations which BRITE will likely catch, but BE stars can do very strange things some times, and vary wildly in unpredictable ways. This is less likely to be well understood with BRITE as it will be hard to uniquely disentangle. Having multicolor photometry should be quite enlightening. Plus, it will literally be in the same field for DSLR observers and roughly the same magnitude, so getting photometry on this star will just require extracting two stars instead of one. Since there is little idea what to expect it will be a fun adventure to follow. 

Mark Blackford
Mark Blackford's picture
CE Tau

Hi Bert,

I've just submitted my first DSLR observations of CE Tau. The field of view is about 2.5 by 1.6 degrees with my Canon 600D and ED80 f6 refractor. By placing CE Tau off center I could include the 67 and 68 stars. I chose 68 as the Comp star as its B-V is closer to that of CE Tau, I used 67 as the Check star.

My TB, TG and TR magnitudes are sigificantly different from those of Artyom Novichonok recorded just a few days before mine. He used an ensemble of Comp stars whereas I used a single Comp. It will be difficult to combine such disparate observations into a coherent light curve. Cheers,

Mark

ulissequadri
ulissequadri's picture
CE Tau and V960 Tau

Hi Bert,

I just submitted my first observations of CE Tau in the AAVSO database. The observations were made with  CCD  and filters B, V, Rc, Ic.
This is the first test in a very bad photometrical night.
Clear skies
Ulisse

bpablo
CE Tau and V960 Tau

Hey Mark and Ulisse,

Thanks for your observations. Sorry, I have been traveling pretty much non-stop for the last couple of weeks. I will take a look at the light curves. We will have to see how things are going, but we can refine moving forward. Thanks, for your observations.

Clear Skies,

Bert

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