Observing Campaigns #875: Monitoring T CrB

View Campaign: Details for Monitoring T CrB

Abstract: The AAVSO and multiple astronomers request ongoing monitoring of the recurrent nova T CrB 1) to alert the astronomical community as soon as T CrB begins its eruption, and 2) to continue to build its multicolor light curve prior to, during, and after the anticipated eruption. Observations with all filters, as well as visual observations, are requested. Spectroscopy is also requested. Observations should be reported to the AAVSO International Database (AID) or AAVSO Spectroscopy Database (AVSpec) as soon as possible after making them. Discussion re T CrB has been moved from the old (now archived) AAVSO forum to the AAVSO forum created in October 2024 for this observing campaign.

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Please carry out conversations about T CrB in this forum. Links to updated instructions for photometry, visual observations, and spectroscopy; an excellent and important blog post on how to observe T CrB now and when it erupts; links to pre-made and custom finder charts with comparison stars; and other information may be found at the campaign linked to this forum (no. 875). If the link to the campaign above this post is not working, you may go directly here: Details for Monitoring T CrB

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I’m amazed that there seems to be no activity in this campaign. Never the less, I have been doing spectroscopy (R=3000 18in Newt, Maryland). Mag 10 is about the lowest brightness I can do, but I have been seeing H emission lines changes in the red and blue spectra. I have difficulty submitting spectra to AAVSO, but meanwhile will be glad to send spectra to anyone interested. John Menke MJLE

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T CrB V-Ic and B-V values have increased recently, over the last 20 days or so. V-Rc mostly unchanged. Something is different!

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Here is a summary of my spectroscopy over the past few months. I also see variances in the continuum spectral shapes in the red and blue. John at menkescientific.com

image

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I have been taking time series data of T CrB all year, but my last data for now was last week because the star is now too low in the evening sky for me to reach it any more. I don’t expect to be able to see it again until the end of November in the morning sky.
-Joe U.

Hi:
How does one subscribe to an Alert or Campaign? What’s the difference between the two. Its nearly impossible for a new observer to figure out how to find an alert and then how to subscribe so you can find it again.
thanks for any help
Gary

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Best to use the search using good search terms perhaps…
Also on the left side menu categories, observing click that and you will find observing campaigns. Latest or Top may be selected which appear at the top of the page.

Here is the “campaigns” new web page.

Campaigns

I was out last night visually observing T CrB with 33x120 Bino’s and a 6" APO Refractor. T CrB is fainter than 9.4 and with the light pollution in my sky to the west, I could not see 9.8 mag visually in the telescope.
Now it would be nice if T CrB waits a couple months before going nova!

I received an email from Mark Bottorff (an astronomer at Southwestern University in Texas):
“I had a look at TCrB this morning 11/14/24 at 6:12 AM CDT. In the pre-dawn skies I could make out CrB with 10X 50 binoculars. I think T CrB is in outburst. It’s slightly brighter than epsilon.”

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Greetings,

For reference, 2024-11-14 06:12 CST is 2024-11-14 12:12 UTC. An BVRI sequence by OAR at 2024-11-14 15:39:30 UTC puts it at V~10.09. Other bands reported by OAR are at a similar magnitude to the previous day.

Therefore, I think this is a false alarm.

I’ve asked HQA to undertake a daytime observation to double check.

Brian

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Greetings,

The claim above that T CrB is brighter than epsilon CrB would put it at V < 4.1.

Observer HQA provided me with the images below at 2024-11-14 04:21 UTC. They are of Theta CrB (V~4.1) and T CrB. T CrB is undetectable whereas Theta CrB is clearly visible. Thus, it seems unlikely that T CrB is in outburst as claimed.

Theta CrB:
thetcrbi

T CrB
tcrbi

Brian

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We’ve also received a separate report from Arto Oksanen who also indicates T CrB is NOT in eruption.

Thank you to both Arne and Arto for their rapid responses!

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So the plausible report of eruption by Bottorff is a false alarm of some unknown type. But false alarms are honorable and inevitable. For T CrB especially, the world is operating on a hair-trigger, required by its very-fast risetime (likely 1-5 hours), its short time at peak (it fades by ~2 mag in the first day), and the modest response time for many telescope (one day or more). For the science, it is much better to have false alarms that are speedily checked, rather than to miss hours in the first-alert. There have been 8 false alarms for T CrB, including three by observers who are amongst the best in the world. I am proud for our observers who checked speedily, with Arto Oksanen checking and replying within 4 minutes that T CrB was not in eruption, and with Arne Henden having the ability to check T CrB during the daytime. So I can offer a heartfelt thank-you for the impressive work of Bottorff, Oksanen, Henden, and Kloppenborg.

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For others that might like to try daylight observing (easy if you are looking for a 2nd magnitude outburst), here is a picture of my setup. Gary Walker and I are working on XPASS, a bright-star extension of APASS, and this is the prototype system. It is a 30cm f/4 corrected Newtonian with an ASI-6200mm camera in one of his excellent enclosures. For daylight observing, Gary found some cake pans on-line, blackened the inside and punched a ~2" hole in one. This is oriented to miss the secondary spyder. Another cake pan covers the mirror end of the telescope to reduce scattered light. This is the ONLY time that I am happy that there are tall pine trees to my south, allowing about an hour/day when the enclosure is shaded. I can do about 5th magnitude easily, and expect to reach T CrB’s 10th magnitude after my software is written and tested.

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Arne, are Gary’s enclosures automated or manually opened and closed? I think I’m seeing a wired mechanism in the photo but was curious to know more.
Thank you,
Gary

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Gary, if you look to the left of the telescope, you will see one of the two linear actuators. These push/pull the roof, rotating about a pivot point, to open or close the roof. These are in turn controlled with a MaxDome board. The wires on the left of the telescope are just the normal USB and power cables for the camera/filterwheel/focuser. The one thing about daytime observing is that you have to be REALLY careful that the telescope does not point towards the Sun. In this case, the L-350 mount points reliably and never points the telescope that far south. Gary has made versions of this enclosure from a 3-foot one that is used for BSM_Hamren, to a 4-foot one for BSM_NH, to this 6-foot one that works for XPASS.

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so, what’s going on today - Spaceweather.com shows 0.0mag and a visual report here on the TCrB page of of 6.0 ???

T CrB is near conjunction with the Sun, and observations are very difficult. I don’t believe either 0.0mag or 6.0mag. My daytime observation today, around UTC 15:26, gave T CrB fainter than mag4.5

Hope springs eternal… I wonder what he really saw?

Anyone communicated with him since the first report?