Alert Notice 820: Photometry and spectroscopy of R Aqr requested for upcoming HST observations

April 19, 2023                  

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Dr. Margarita Karovska (Center for Astrophysics|Harvard & Smithsonian) requests the assistance of AAVSO observers in monitoring the symbiotic binary (Mira + white dwarf) R Aqr in support of upcoming observations with HST scheduled for the week of May 5-8, 2023. When the exact date/time is known, it will be posted in the forum threads above.

R Aqr is just emerging from its seasonal gap, and coverage is essential as soon as it is possible to pick it up in the dawn twilight from your location. It is critical to have some nights of positive observations prior to the satellite observations, and then follow up during May, June, and the first half of July 2023.

Starting now, Dr. Karovska requests photometry, primarily V and B photometry, and then UIRH, and if at all possible mid-IR photometry. High-speed UB photometry and spectroscopy are also requested. Visual observations will be very valuable and are strongly encouraged.

The cadence requested for photometry is twice a week, then nightly May 1-15, then twice a week for two months after the satellite observations, through July 15. For high speed UB photometry, a cadence of a few minutes is requested.

For spectroscopists, Dr. Karovska requests resolution as high as possible, wavelength range 3500-8000A, a good enough S/N so that lines can be detected and analyzed, and if full coverage is not possible, to give priority to Hbeta, Halpha, [OIII]5008A, [OII]3730A, [SII]6730A. The cadence requested is daily during the observing window, then twice a week or weekly through July 15.

R Aqr is presently undergoing the eclipse that occurs about every 40 or so years. Dr. Karovska reports that "the effects of the periastron are still visible including dimming of the light curve, absorbing the emission from the Mira and perhaps the binary itself by material that has been recently ejected."

R Aqr has a V range of 5.2-12.4. It had been behind the Sun since 2023 February, and the most recent observation from the AAVSO International Database shows it at V magnitude 12.182 +/- 0.018 on 2023 Apr. 18.418727 UT (J.-F. Hambsch, Mol, Belgium, remotely from Atacama, Chile).

Coordinates (J2000): R.A. 23 43 49.46  Dec. -15 17 04.2  (from VSX page for R Aqr)

Charts with comparison stars for R Aqr may be created using the AAVSO Variable Star Plotter (VSP).

Please report all photometry observations to the AAVSO International Database using the name R AQR. Spectroscopy reports should be submitted to the AAVSO Spectroscopy Database (AVSpec) and to Dr. Karovska (

This request from Dr. Karovska regarding R Aqr reflects her ongoing research on this very interesting symbiotic system. Earlier related Alert Notices include 792, 738, 696, 689, 665, 600, and 589.

This Alert Notice was compiled by Elizabeth O. Waagen using material provided by Dr. Karovska.


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