Abstract: Dr. Patrick Godon (Villanova University) writes: BZ Cam is a novalike cataclysmic variable system (type VY Sculptoris) found mostly in a state of high accretion rate when the accretion disk dominates the light (ultraviolet optical) system and from time to time (every 10 years or more) it goes into a low state when the mass accretion rate decreases and the luminosity of the disk drops significantly. Its luminosity exhibits orbital modulations as well other small amplitude variations on longer time-scales. It is the target of a multiwavelength campaign to be observed in X-ray (with Chandra), Ultraviolet (with HST), Optical, and Radio (with ground-based large telescopes). The aim is to study the accretion disk - it emits in the X-ray band where it “touches” the star, in the ultraviolet in the vicinity of the star, and in the optical further out. This is one of the only cataclysmic variable systems clearly showing a bow shock nebula, an indication that there is a strong outflow of matter.
Justification: In order to know exactly in which state BZ Cam is observed with HST and Chandra, and also to protect the ultraviolet detector of the COS instrument on HST from possible strong emission lines (though very unlikely), monitoring of the system is needed in the month preceding and during the HST (and Chandra) observation. The HST and Chandra observations are coordinated to be carried out the same week: between September 22 (2024) and September 27 (2024) - inclusive dates. Monitoring of BZ Cam is requested beginning now, with V/CV/TG observations about once a week, and once a day starting (September 15 - a week before the HST observation) through October 1st. After that monitoring can resume to be once a week for the month of October. A positive observation in V is required 24 hours before the HST observations are scheduled to take place for the HST team to make a go/nogo decision; V coverage for September 22 - 27 is crucial. The forum linked to this campaign will be updated when the exact date/time is known.