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Cloudy here but I grabbed a frame off an all sky camera (University of Hertfordshire http://observatory.herts.ac.uk/allsky/ ) and compared it with the same date and time a year ago. See attached. A crude comparison but the relative brightness of Megrez looks roughly the same to the camera at least
Cheers
Robin
I just had a look at the last 6 months data of a similar magnitude star with variability that I am familiar with and which has good photometric data in the AAVSO database.
Here is KWS
and here is AAVSO with the same Y scale range
I looks like KWS is unreliable at least with bright stars in V
Robin
B,V Ic correspond to the band in which the brightness was measured. (The survey instrument uses a CCD camera and wide field lens). V corresponds roughly to what the eye sees Ic is the near infrared. There are small long term average trends from season to season but the variation from day to day/week to week of up to 0.5 magnitudes seen in the V data would be obvious by eye if real. The very tight error bars on the points would suggest they are real but I am somewhat sceptical.
Interesting that the variability in I is much less than in V. Reminiscent of the recent Betelgeuse fading
I was taking spectra last night and the signal from the target suddenly disappeared. I went outside to check and as far as I could tell the sky was completely clear. I went back inside and watched as the signal came back up. Half an hour later the same thing happened but this time I looked outside to find it was foggy, putting an end to observations
I Iooked at this but their claim that the extinction is grey is not the case here if one looks at the photometry in the IR where there was no reduction in H J bands and a smaller drop in R compared with B,V which is also seen in spectra. Perhaps this can be explained by the large grained dust model but I am surprised they have not considered the available photometry data
Christian Buil has just posted some high (R ~ 38,000) resolution spectra which confirm the reduction and narrowing of the H alpha line seen in my medium resolution spectra. He also detects a small (4.5km/s) shift in the line.
http://www.spectro-aras.com/forum/viewtopic.php?f=38&t=2433&p=13796#p13792
These observations may be consistent with the partial obscuration of the star as suggested from the VLT images. The speed of rotation of the star is of the right order as can be seen in this reference and the axis of rotation is given there
https://www.obspm.fr/the-slow-rotation-of-the-red.html?lang=eng
As far as I can see, the orientation of the VLT image is not given though unfortunately.
Jeremy, are you still in contact with Prof. Constantino Sigismondi? I wonder if these observations might be of interest
Cheers
Robin
Yes slightly as seen in the increased depth of the molecular absorption bands (perhaps 1 subdivision eg M2i to M3i?)
https://britastro.org/comment/7649#comment-7649
https://britastro.org/comment/7861#comment-7861
Interestingly there has also been a reduction in H alpha absorption since the start of the year
In this case since it is a particular campaign with specific goals I would probably look to the PI for guidance.
In general though the processing (including combining) of data for submission to databases where the end use is unknown (and in this case potentially may not be known until all of us are long gone) is an ever present dilemma. I faced this in real life for example concerning databases storing vast quantities of process control and quality time series data from a continuous process (a paper machine) where (similar to astronomy) variations over several orders of timescale (from milliseconds to years in that case) are potentially of relevance. Ultimately, storing the data from every exposure and letting the final user make the decision would be ideal (aided perhaps by tools in the database to allow the casual user interrogating the database to view the filtered data). Andy (like our paper mill IT manager at the time) might baulk at every exposure being measured and stored individually indefinitely though! An alternative approach could perhaps be based on examining the data prior to submission to look at what point when combining data the variation if any becomes significant compared to the uncertainty, thus preserving the maximum information while storing the minimum of data.
Cheers
Robin
From the AAVSO light curve it looks like it reached maximum (~12.3 CV) on 25/26th Jan.
No chance to observe here for 2 weeks straight now (Even the odd clear spell has been bracketed by rain showers) but James Foster managed to get a few spectra and added them to our database.
https://twitter.com/planet4589/status/1222667505505722369
looks like they missed or at least no head on crash !
“Nonetheless, I am willing to tolerate pedants who think otherwise.”
🙂
There is indeed no point swimming against the tide on this one but don’t you find a decade lasting 9 years even a little unsettling 😉
01-01-21. Same as with the new millenium. Since the first day of the Common Era was 1st Jan 0001 the 3rd millenium began 1st Jan 2001 but you probably will not convince the billions who celebrated the year before or similarly convince them that the new decade starts next year
Here is the latest Atel on the subject
http://www.astronomerstelegram.org/?read=13410
“The recent changes defined by our V-band/Wing photometry seem best explained from changes in the envelop-outer convection atmosphere of this pulsating, unstable supergiant. If these recent light changes are due to an extra-large amplitude light pulse on the ~420-day period, then the next mid-light minimum is expected during late January/early February, 2020. If Betelgeuse continues to dim after that time then other possibilities will have to be considered. The unusual behavior of Betelgeuse should be closely watched.”
I am now picking up some evolution in my spectra since the start of the year. The relative flux around 7500A has been increasing compared with that at 5500A. This is consistent with the brightness in V dropping more than in the IR
