Photometry of BZ Camelopardalis in support of HST, Chandra multiwavelength observing campaign
Active Dates: Aug. 26, 2024 – Oct. 31, 2024
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.
Requested Data Types:
Photometry
Targets
| Name | Magnitude | Variability Type | Photometry Notes | Spectroscopy Notes |
|---|---|---|---|---|
| BZ Cam | 11.40 | NL/VY |
Cadence: Custom Precision: 100 |
Not Requested |
Spectroscopy Lines:
No spectroscopy lines provided
Photometry Filters:
V (Johnson), Other (Please Specify)
Comparison Stars:
Finder charts with comparison stars are available via the AAVSO Variable Star Plotter (VSP, https://apps.aavso.org/vsp/).
Co-Authorship
Observers are not eligible for co-authorship.
Additional Observer Input:
Photometry filters: Visual; Johnson: V, B; unfiltered V zeropoint; tri-color green. These filters have been used by AAVSO observers in the last 20 years for BZ Cam (from the actual AAVSO light curve). Cadence: about once a week starting now, and a cadence of once a night starting mid-September (Sept 15) though October 1st. After that, back to a cadence of once a week. BZ Cam has a magnitude around 13.0, but has been observed as bright as 11.5 and as faint as 14.5. Comparison stars provided by the AAVSO - finder charts with comparison stars for BZ Cam may be created using the AAVSO Variable Star Plotter (https://www.aavso.org/vsp). Submit observations to the AAVSO as soon as possible after making them using WebObs and the name BZ CAM.
Additional Submission Location:
none
Notes:
Though it is not expected, the HST observation date may change at the last moment, which will require updating the dates and cadence for the AAVSO monitoring of BZ Cam. Updates will be made in the forum linked to this campaign.