Alert Notice 816: KR Aur observations needed tonight for HST check

March 9, 2023

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Further to AAVSO Alert Notice 754, Drs. Anna Francesca Pala (European Space Agency, ESAC, Spain) and Thomas Kupfer (Texas Tech University) request AAVSO observers' assistance in observing the novalike cataclysmic variable KR Aur beginning immediately - MOST IMPORTANT IS TONIGHT (MARCH 9/10) - in support of HST observations scheduled for March 11, 2023 UT.

Dr. Pala writes: "A few weeks ago we have triggered the ToO HST observations for KR Aur, since it entered a low state at the end of January. The HST observations have finally been scheduled for March 11th, 05:56 UT. At the current brightness (V~15.3), KR Aur is still safe for HST and there is the opportunity to get the ultraviolet data even if the system is coming out of the low state.

"Tonight's observations would be the most important since we need to obtain a positive detection [in V] to confirm that the target it is safe to be observed with COS. It would be very helpful if you could obtain as many measurements as possible, and as late as possible within the visibility period of the target. Ideally as late as 7 or 8 UT (or even later, according to your location).

"Thanks for your support and good luck with the observations!"

Please see AAVSO Alert Notice 754 for instructions re filters (V preferred, CV also useful) and cadence, and for instructions re spectroscopy. Continue observing KR Aur until further notice - information on when to return to one snapshot per night will be posted in the forum threads given above.

Observations submitted to the AAVSO International Database show that from its usual high state magnitude of 14-15 V, KR Aur began fading in January 2023 and was at magnitude 18.859 V +/-0.1 on 2023 Feb. 19.23302 UT (S. Bolzoni, Santhia, Italy). The most recent observations in the AID show it at 15.701 V +/- 0.079 on Mar. 6.77243 UT (J. Prieto Gallego, Madrid, Spain) and 15.263 CV +/- 0.04 on Mar. 8.006 UT (G. Poyner, Birmingham, UK).

Coordinates (2000.0):  R.A. 06 15 43.92   Dec.  +28 35 08.6  (from VSX page for KR Aur)

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

Please submit observations to the AAVSO International Database using the name KR AUR.

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


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