YZ Cnc Type: SU Ursae Majoris AAVSO lightcurve (2020 ) AAVSO lightcurve (index) SU Ursae Majoris-type variables are characterized by the presence of two types of outbursts called "normal" and "super-outbursts". Normal, short outbursts are similar to those of UGSS stars, while super-outbursts are brighter by 2 magnitudes, are more than five times longer (wider), and occur several times less frequently. During super- outbursts the light curves show superposed periodic oscillations (super-humps), their periods being close to the orbital ones and amplitudes being about 0.2- 0.3 magnitudes in V. Orbital periods are shorter than 0.1 days; companions are of dM spectral type. AAVSO Legacy Cataclysmic Variable Programme and two AAVSO Alerts (see below) AAVSO Alert Notice 617, 5 March 2018 Multiwavelength observations of YZ Cnc, SU UMa, and CR Boo outbursts Bob Jacobs (Ph.D. candidate, Radboud University) and Drs. Samaya Nissanke (Radboud University), Jennifer Barnes (Columbia University), and Deanne Coppejans (Northwestern University) have requested AAVSO observers' assistance in monitoring the cataclysmic variables YZ Cnc, SU UMa, and CR Boo. The goal is to build good multicolor light curves of two outbursts of CR Boo and two superoutbursts each of YZ Cnc and SU UMa. Nightly observations of these stars in any Johnson-Cousins band are requested. When an appropriate outburst occurs, observers should switch to multiple observations per night in 3 or more (more preferred) Johnson-Cousins bands (U,B,V,R,I,J,H,K) spread across the spectrum if possible. It is essential to switch to the higher cadence and multiple bands as soon as possible after the outburst begins. Continue until the star returns to minimum, then resume nightly observations. Visual observations are welcome and are encouraged. The astronomers want to catch the target outbursts as early as possible. If you see an outburst beginning, please notify the AAVSO immediately via the forum thread for this campaign, and submit your observation(s) as soon as possible. The astronomers provide the following background information: "Last year's Nobel Prize in Physics went to three researchers in the field of gravitational waves. Two weeks later gravitational wave astronomers announced the discovery of a gravitational wave signal from a merger of two neutron stars. This system also emitted optical light right after the merger and it was observed by many telescopes on the southern hemisphere. The new type of transient was called a "kilonova" or "macronova". When two neutron stars merge, they emit large amounts of matter in ejecta (on the order of 1/100th-1/10th the mass of the Sun). These ejecta are neutron rich. Atoms in the ejecta will capture these neutrons and become much heavier than the atoms created in supernovae. They subsequently decay to stable elements like gold and platinum, heating up the ejecta and making it emit optical and infrared light. Kilonovae could account for all of the gold and platinum in the universe. That's why we would like to observe more kilonovae and test this hypothesis (plus many more). Kilonova observations will also put tighter constraints on gravitational waveforms and therefore the theory of General Relativity. Because kilonovae last for only ~10 days, it's important to catch them as early as possible, which requires good observing strategies. "In order to observe more kilonovae the Radboud University, KU Leuven and NOVA are building the optical telescope BlackGEM in Chile. Upon an alert from the gravitational wave observatories, BlackGEM, together with other observatories, will try to discover the kilonova as quickly as possible. In order to find optimal observing strategies to find the kilonova as quickly as possible, we are trying to simulate how many transients of each type (e.g. Supernovae, dwarf novae, AM CVNs etc.) one would see in what parts of the sky with BlackGEM in each of its color-bands. These transients could be false-positives in the search for the kilonova: they may be indistinguishable from kilonovae. We want to have as few false-positives and as many correctly identified kilonovae as possible. The simulator will also be applicable in other fields of astronomy where estimates are needed for the variability of the night sky. "For our simulation we use photometry from telescopes to model the temporal evolution of transients. Thanks to the AAVSO community we already have excellent multi-color light curves for SS Cyg and Z Cam type cataclysmic variable outbursts (U Gem and RX And). Unfortunately there aren't yet any light curves available for SU UMa or AM CVn type outbursts with sufficient multi- color coverage to use in our models. AAVSO Alert Notice 565: December 19, 2016 Dr. Christian Knigge (University of Southampton) and colleagues have requested AAVSO coverage of the SU UMa-type dwarf nova YZ Cnc in support of Chandra X-ray observations to be carried out via a Target of Opportunity (TOO) triggering when the system is in a suitable outburst. YZ Cnc has normal outbursts about every 7-10 days, and superoutbursts about every 100-110 days. The astronomers are planning to use a superoutburst to trigger the TOO observations. The last well-documented superoutburst occurred in March 2016, and a possible superoutburst was observed in June 2016. No superoutburst was seen in September, but YZ Cnc was just emerging from conjunction so there were very few observations. The next superoutburst of YZ Cnc, expected in late December-early January, may or may not be well placed for Chandra's schedule, so monitoring may need to continue through more than one superoutburst before the TOO observations can be triggered. Once the TOO observations have been triggered, coverage will need to continue through at least one normal outburst after the Chandra observations have been completed. Good coverage of YZ Cnc from AAVSO observers this season is essential; your observations will be used to decide when to trigger the TOO observations. An AAVSO Special Notice with further instructions will be issued when the Chandra observations are triggered, so please be sure to subscribe to the Special Notices. Subscription to Special Notices (free) is via the Email Settings tab on your My Account page on the AAVSO website. Please observe YZ Cnc beginning now (one to a few times, widely spaced, per night), continuing until the Chandra observations have been carried out and the end of the campaign is announced. Visual and V or CV band observations are requested; other bands are welcome but are not essential. Please report your observations to the AAVSO via WebObs as soon after you make them as possible, especially if you see YZ Cnc at visual magnitude 13.8 or brighter. Typical normal outbursts reach visual magnitude ~12.0, and superoutbursts ~11.0-11.3. In recent years at minimum YZ Cnc has been ~14.6-14.8. AAVSO Alert 539: March 1, 2016 Ms. Deanne Coppejans (PhD candidate, Radboud University Nijmegen (Netherlands) and University of Cape Town) and colleagues have requested AAVSO observer assistance in monitoring several northern dwarf novae in support of their campaign to observe them with the Very Large Array (VLA) in their ongoing radio jet research. Their research on radio jets in dwarf novae has been discussed in AAVSO Alert Notice 505 (https://www.aavso.org/aavso-alert-notice-505). Nightly observations are sufficient to determine whether the source is in outburst or quiescence when a VLA observation is taken. In this campaign, the VLA observations are not triggered by the PI, so there is no way to predict when the VLA will observe the sources. Observers will be notified whenever VLA observations are obtained, but no modification of observing instructions is expected. Nightly visual or V observations are requested beginning now and continuing through June 2016