On the night of Jun 10/11, 2025, under very poor conditions -- lots of clouds -- I acquired images of the recurrent nova T CrB. This star undergoes outbursts at long intervals of 80 years or so. Its next outburst is predicted to occur soon (but then again, it was also predicted to occur during 2024), and so I've joined the crowd who are monitoring it.
These data are not very good, except for the few measurements early in the night when the skies were clear, but they do show that T CrB did not explode.
This recurrent nova brightens from by about 8 magnitudes (!), from V = 10 to about V = 2, around every 80 years. Will we see another outburst THIS summer?
These observations involved:
Notes from the night:
The picture below shows a cropped image of the field of T CrB from Jun 14/15, 2024. The field of view is about 20 arcminutes across.
I've marked the location of several comparison stars, with magnitudes and names taken from the AAVSO's table X40237AAS. Note that the magnitudes listed for stars "A" and "B" have changed from the ones I listed in last year's notes.
star name B V
------------------------------------------------------
A 000-BJS-901 11.096 10.554
B 000-BBW-805 11.779 11.166
C 000-BPC-198 13.049 12.336
--------------------------------------------------------------------------
When the target is centered, the finder TV shows this field:
Here's the sky background over the course of the run. Thick clouds ruined most of the pictures; only about 38 measurements out of 197 images.
The FWHM had huge scatter due to clouds.
The graph below shows changes in the photometric zeropoint of an ensemble solution of the instrumental magnitudes over the course of the run. The range of over 1.5 mags is awful, but I accepted all these images in order to achieve a few measurements.
Using aperture photometry with a radius of 7 pixels in V filter (binned 4x4, each pixel is 1.036 arcsec, so a radius of 7.3 arcsec), and 7 pixels in B filter (binned 4x4, each pixel is 1.036 arcsec, so a radius of 7.3 arcsec), I measured the instrumental magnitudes of a number of reference stars and the target. Following the procedures outlined by Kent Honeycutt's article on inhomogeneous ensemble photometry, I used all stars available in each image to define a reference frame, and measured each star against this frame.
Sigma-vs-mag plots show that the floor in V-band was about 0.030 mag, which is about 6 times larger than usual! In B-band, it was 0.015 mag, also awful.
The measurements show that the target is still quiescent.
I've submitted these measurements to the AAVSO.