- This topic has 90 replies, 21 voices, and was last updated 4 weeks, 1 day ago by
.
-
Posts
-
Hi Ian,
Here’s a link to using the drift-scan technique for occultation events
https://www.asteroidoccultation.com/observations/DriftScan/Index.htm
I’ve no experience of using it, and the Betelgeuse event was gradual.
All observers who attempted to observe the Betelgeuse occultation are requested to submit a report form and their raw data to the pro-am campaign team in Paris. This is discussed in Josselin Desmars’ presentation
(PDF in this link)
https://share.obspm.fr/s/aYzPBYByoEL2xZY(video at this link – talk begins at 1hr 51m)
https://astrotube.obspm.fr/w/isuxhMSJZ5FNNPKeT3AZbbCreate an account on the Occultation Portal
https://occultation.tug.tubitak.gov.tr/then upload your report file and data (see other methods if files are very large). The Paris team will analyse your data.
Alex (back in ‘sunny’ Leeds)
An MNRAS submission on “Images of Betelgeuse with VLTI/MATISSE across the Great Dimming” appears on ArXiv today: https://arxiv.org/abs/2401.12404
The authors present mid-infrared long-baseline spectro-interferometric measurements of Betelgeuse taken with the VLTI/MATISSE instrument before (Dec. 2018), during (Feb. 2020), and after (Dec. 2020) the Global Dimming Event. This supports the theory that the dimming was due to dust (especially SiO) being blown off by the red supergiant.
Thanks Jeremy.
Miguel Montarges is the lead scientist of the Leona-Betelgeuse pro-am campaign and he has just e-mailed the group to mention that they’ve received over 100 observations, and 75 of the light curves are almost not – or not at all – affected by clouds. Recordings were obtained using various filters, so they should be able to measure Betelgeuse’s diameter at a range of wavelengths.
As a very provisional example, Dave Herald measured a light curve obtained in Ha by Alfonso Noschese, and after applying a large limb darkening coefficient it gave a diameter of 60 mas.
https://ukoccultations.groups.io/g/main/message/3036
The campaign team also hopes that the dataset will detect the huge convection cells in Betelgeuse’s photosphere.
Cheers,
Alex.
It will certainly be interesting to see what new insights emerge from analysis of the occultation, Alex!
Costantino Sigismondi reports Betelgeuse is dimming and is now as faint as it has been for two years:
https://www.astronomerstelegram.org/?read=16501whilst nothing like as faint as it got during the great dimming of a few years ago, it’s worth keeping an eye on as Orion dips towards the west.
A paper on ‘Single-photon gig in Betelgeuse’s occultation’ is available on ArXiv
https://doi.org/10.48550/arXiv.2406.14704
(Thanks to Oliver Klös IOTA/ES for bringing this to our attention)
The authors describe recording the 2023 Dec 12 Leona-Betelgeuse occultation using a Single-Photon Avalanche Diode (SPAD) array, and they give their measures of the light drop and Betelgeuse’s angular diameter in the SDSS g-band.
(We await the paper(s) from the Leona-Betelgeuse pro-am campaign).
Alex.
Fascinating technology that SPAD array. I don’t understand though why the SNR for the SPAD array shown in fig 4 is so much lower than for the CMOS camera. They say it is 50x lower and attribute it to the low 3.5% fill factor but by my calculation, that alone should only give an ~5x reduction of SNR, not 50x ie sqrt(1/0.035)
Cheers
RobinHi Robin,
The lead author gives their e-mail address, so you could contact them for clarification.
Fig. 4 shows interesting disparities in the ‘g’ and ‘r’ light curves during the ingress phase. These are the kind of features that the Leona-Betelgeuse analysts will be investigating.
Cheers,
Alex.
Hi Alex,
The lead author gives their e-mail address, so you could contact them for clarification.
Yes I have done. We’ll see what comes back. Fig 4 has error bars which are clearly nowhere near 50x wider for the SPAD data which if the 50 fold figure is correct, implies the uncertainty is determined by factors other than the SNR. At 50ms sample rate I would expect scintillation to be a significant factor in the uncertainty, though there seems to be perhaps some interesting correlation in the fine detail between the two measurements during egress which cannot be due to scintillation.
Cheers
RobinHi Robin,
The paper and SPAD vs CMOS sensor performance are now being discussed on the IOTAoccultations forum
https://groups.io/g/IOTAoccultations/topic/recent_article_on_use_of/106850984
Cheers,
Alex.
- You must be logged in to reply to this topic.