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THE ASTRONOMER Electronic Circular No 3698      2022 Apr 20 14.12UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.ORG.UK             Backup: guy_hurst@hotmail.com
WORLD WIDE WEB                         http://www.theastronomer.org
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RS OPH: BRIGHTENING and OPTICAL FLICKERING

Further to TA E-Circular 3693 of unusual activity in RS OPH Filipp Romanov
updates on #15339:

Last year there was another eruption of the recurrent nova RS Oph. According
to my visual brightness estimate with the unaided eye, it was 4.6 mag at
2021-08-09.63889, near the peak of its brightness. 

I observed RS Oph remotely using 0.61-m f/6.5 corrected Dall-Kirkham robotic
telescope (Lane, 2018, RTSRE, 1, 119) of Burke-Gaffney Observatory (Saint
Mary's University in Halifax, Nova Scotia, Canada). Part of multicolour
photometric data (dates are in UTC and correspond to the middle of the
exposures) is presented below: 


2022-02-01.41702 V = 12.09 +/- 0.04
2022-03-05.38507 V = 11.87 +/- 0.03
2022-03-14.31071 V = 12.03 +/- 0.02
2022-03-30.25550 V = 11.78 +/- 0.02
2022-03-31.29944 V = 11.80 +/- 0.05
2022-04-03.29402 V = 11.81 +/- 0.03
2022-04-06.28729 V = 11.79 +/- 0.02
2022-04-07.27955 V = 11.58 +/- 0.01
2022-04-12.26568 V = 11.40 +/- 0.02
2022-04-13.31289 V = 11.28 +/- 0.01
2022-04-16.32398 V = 11.25 +/- 0.04 

According to these data, rapid brightening started after 2022-04-06, with
the largest amplitude in the B band. After the prediction in ATel #15296
that the flickering should appear in the next 30 days, I regularly requested
one-hour time series observations with 60 seconds exposure time using
photometric Johnson B filter. 

I did not detect the flickering (present on 14 April 2022 as reported in
ATel #15330) during observations from 2022-03-30.25646 to 2022-03-30.29991
UTC, the mean magnitude was 13.14 B +/- 0.05 and magnitude errors were
similar to those of comparison stars. A day later, due to cloudiness, errors
increased during the time series, which made it possible to measure only the
mean magnitude: 13.14 B +/- 0.1. 

On April 2022, from 03.24608 to 03.29498 UTC, I detected apparent magnitude
variations with a peak-to-peak amplitude of 0.13 mag in B band,
significantly larger than magnitude errors of comparison stars, and this is
the first detection of optical flickering of RS Ophiuchi in these data.
According to the observations from April 06.23469 to 06.28825 UTC, the
magnitude variation is less than 0.1 mag and slightly differs from the
magnitude errors of comparison stars. 

From April 07.23120 to 07.28051 UTC, magnitude has changed from 12.96 to
12.79 B +/- 0.01, and this is the second reliable detection of flickering.
As a result, I conclude that the flickering appeared between March 30 and
April 3, 2022. 

Guy M Hurst

