Betelgeuse Fainting

[Superluminal]

Betelgeuse seems closer in magnitude to Aldebaran, .8 mag., than it did last week. May be a lot of dust swirling in the area.

[Roger E. Moore]

Two different views on what caused the Great Dimming of Betelgeuse, 2019-2020.

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https://arxiv.org/abs/2011.05982

The Photospheric Temperatures of Betelgeuse during the Great Dimming of 2019/2020: No New Dust Required

Graham M Harper (1), Edward F Guinan (2)Richard Wasatonic (2), Nils Ryde (3) ((1) University of Colorado Boulder, (2) Villanova University, (3) Lund University)

The processes that shape the extended atmospheres of red supergiants (RSGs), heat their chromospheres, create molecular reservoirs, drive mass loss, and create dust remain poorly understood. Betelgeuse's V-band "Great Dimming" event of 2019 September /2020 February and its subsequent rapid brightening provides a rare opportunity to study these phenomena. Two different explanations have emerged to explain the dimming; new dust appeared in our line of sight attenuating the photospheric light, or a large portion of the photosphere had cooled. Here we present five years of Wing three-filter (A, B, and C band) TiO and near-IR photometry obtained at the Wasatonic Observatory. These reveal that parts of the photosphere had a mean effective temperature (Teff) significantly lower than that found by (Levesque & Massey 2020). Synthetic photometry from MARCS -model photospheres and spectra reveal that the V band, TiO index, and C-band photometry, and previously reported 4000-6800 Angstrom spectra can be quantitatively reproduced if there are multiple photospheric components, as hinted at by VLT-SPHERE images (Montarges et al. 2020). If the cooler component has ΔTeff ≥ 250K cooler than 3650 K, then no new dust is required to explain the available empirical constraints. A coincidence of the dominant short- (∼430 day) and long-period (∼5.8 yr) V-band variations occurred near the time of deep minimum (Guinan et al. 2019). This is in tandem with the strong correlation of V mag and photospheric radial velocities, recently reported by Dupree et al. (2020b). These suggest that the cooling of a large fraction of the visible star has a dynamic origin related to the photospheric motions, perhaps arising from pulsation or large-scale convective motions.

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https://arxiv.org/abs/2010.04243

Betelgeuse scope: Single-mode-fibers-assisted optical interferometer design for dedicated stellar activity monitoring

Narsireddy Anugu, Katie M. Morzinski, Josh Eisner, Ewan Douglas, Dan Marrone, Steve Ertel, Sebastiaan Haffert, Oscar Montoya, Jordan Stone, Stefan Kraus, John Monnier, Jean-Baptiste Lebouquin, Jean-Philippe Berger, Julien Woillez, Miguel Montargès

Betelgeuse has gone through a sudden shift in its brightness and dimmed mysteriously. This is likely caused by a hot blob of plasma ejected from Betelgeuse and then cooled to obscuring dust. If true, it is a remarkable opportunity to directly witness the formation of dust around a red supergiant star. Today's optical telescope facilities are not optimized for time-evolution monitoring of the Betelgeuse surface, so in this work, we propose a low-cost optical interferometer. The facility will consist of 12 × 4 inch optical telescopes mounted on the surface of a large radio dish for interferometric imaging; polarization-maintaining single-mode fibers will carry the coherent beams from the individual optical telescopes to an all-in-one beam combiner. A fast steering mirror assisted fiber injection system guides the flux into fibers. A metrology system senses vibration-induced piston errors in optical fibers, and these errors are corrected using fast-steering delay lines. We will present the design.

[Superluminal]

Tonight, Betelgeuse looks as if it is 0.1 magnitude fainter than Aldebaran.

[SagittariusAStar]

Feature story about Betelgeuse in Science News by Lisa Grossman: link

[CJSF]

Over on Twitter, Betelbot has been reporting brightness fluctuations between ~80% and 95% over the last couple of weeks, some times near that range night-to-night! I don't know if that sort of variation is historically "normal" or if the fainting event has really "gunked up" the system.

CJSF

[Superluminal]

Over on Twitter, Betelbot has been reporting brightness fluctuations between ~80% and 95% over the last couple of weeks, some times near that range night-to-night! I don't know if that sort of variation is historically "normal" or if the fainting event has really "gunked up" the system.

CJSF

I've noticed the same thing. Some nights it's very close to Aldebarans magnitude. Other nights it's 0.1 or 0.2 magnitudes brighter.

[Roger E. Moore]

Study of supergiant star Betelgeuse unveils the cause of its pulsations.

https://phys.org/news/2021-02-superg...ulsations.html

[cannongray]

Thanks to Hubble it became clear that the real reason for such behavior is a dust cloud that blocked almost a quarter of Betelgeuse's surface for an observer on Earth.

[Superluminal]

Betelgeuse seems to be holding steady at its normal 0.7 magnitude, if not a couple of tenths brighter.
https://app.aavso.org/webobs/results...um_results=200
I haven't seen it in several days due to clouds. But I estimate it at 0.5.

[Roger E. Moore]

Hubble solves mystery of monster star's dimming. The red hypergiant VY Canis Majoris—which is far larger, more massive, and more violent than Betelgeuse—experiences much longer, dimmer periods that last for years. New findings from NASA's Hubble Space Telescope suggest the same processes that occurred on Betelgeuse are happening in this hypergiant, but on a much grander scale.

https://phys.org/news/2021-03-hubble...r-dimming.html

[Superluminal]

Betelgeuse and Aldebaran photographed to night through a C-8 with Orion Starshoot planetary camera. Aldebaran is magnitude 0.86.

[Superluminal]

Images of Betelgeuse and comparison star, Aldebaran.

[CJSF]

On Twitter, Betelbot continues to report day-to-day changes in brightness bewteen ~85 and over 100% of its "average brightness".

CJSF

[Superluminal]

On AAVSO, magnitudes run from +0.8 to +0.3. The difference is a bit subtle. Some nights it appears equal to Aldebaran, +0.86. Other nights it appears +0.5, to my eyes.

[CJSF]

https://twitter.com/betelbot/status/1370089840348340226

Now at 78% of my usual brightness!

CJSF

[Superluminal]

Betelgeuse and comparison star Aldebaran 0.8 magnitude, tonight. Windy, difficult to get good images. Stars appear to be nearly equal in magnitude. AAVSO indicates Betelgeuse may be fainting again.
https://app.aavso.org/webobs/results...um_results=200

[kpatz]

Here's my insane Thursday-morning-after-work-has-thoroughly-fried-my-brain thought:

Obervation: Betelgeuse fainted in late 2019-early 2020, presumably because it ejected a cloud of dust. Then the pandemic happened.

Conclusion: Betelgeuse sneezed, and made us all sick.

[Superluminal]

Betelgeuse, left, and comparison star Aldebaran, right. Betelgeuse actually appears fainter than Aldebaran. To the unaided eye they are very nearly equal. Taken through a C-8 Schmidt-Cassegrain.

[CJSF]

Betelbot as been reporting brightnesses consistently around 80-85% of average all week.

CJSF

[Superluminal]

Betelbot as been reporting brightnesses consistently around 80-85% of average all week.

CJSF

I've noticed the same thing. Betelgeuse is approximately equal to Aldebaran, 0.86 magnitude. Be interesting to watch, is this its normal dip, or another deep fainting.

[Superluminal]

Betelgeuse is still approximately equal to Aldebaran in magnitude. A few on AAVSO are listing it as slightly brighter than Betelgeuse. My 62 year old eyes can't tell the difference. The other night I was able to do a little experiment. A friend was at the house, someone who knows almost nothing about astronomy. Just after dark, the sky was moonless and about as clear as it gets here. I pointed out the two stars and asked her which one is brighter. With little hesitation she pointed at Aldebaran and said, "That one." Interesting, because I go back and forth with binoculars or my C-8 before deciding on a magnitude difference. Am I trying to hard or should I go with my first impression?