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AAVSO Alert Notice 617

Multiwavelength observations of YZ Cnc, SU UMa, and CR Boo outbursts

5 March 2018

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 general theory of 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.

"With your help we look forward to seeing the first well-sampled multi-color observations of CR Boo, SU UMa, and YZ Cnc in outburst."


Name R.A. (2000.0) Dec (2000.0)
YZ Cnc 08 10 56.65 +28 08 33.2
SU UMa 08 12 28.28 +62 36 22.3
CR Boo 13 48 55.22 +07 57 35.7

Charts with comparison star sequences for YZ Cnc, SU UMa, and CR Boo may be plotted using the AAVSO Variable Star Plotter (VSP).

Please submit observations to the AAVSO International Database using the names YZ CNC, SU UMA, and CR BOO.

This observing campaign is being followed on the AAVSO Campaigns and Observing Reports online forum at

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.

It’s all about the  standstills, those episodes where the star gets stuck at a mid-point between maximum and minimum. If it doesn’t exhibit standstills it isn’t a Z Cam star.

Data from Catalina Real Time Survey 

Drake et al. 2009, ApJ, 696, 87

Northern CVs brighter than 17th magnitude here.

Southern CV's brighter than 17th magnitude here.


Last updated 02:16 UT on 21 June 2018

New outbursts and unusual activity reported in the last 72 hours


UU Aql
SY Cap
CS Ind
V893 Sco
CC Scl
VW Tuc

DT Aps
FO Aql
V725 Aql (UGSU, superoutburst!)
V1233 Aql
WX Hyi
TU Ind
HP Nor
BE Oct (superoutburst)
DT Oct (superoutburst)
V729 Sgr
V4140 Sgr (UGER:, superoutburst? – eclipsing, Porb= 0.061430 d)
FL TrA (superoutburst)
V383 Vel
ASASSN-14fz (superoutburst)

Current superoutbursts (since ...)
BE Oct (20180618)
DT Oct (20180618)
FL TrA (20180618)
ASASSN-14fz (20180618)
V2051 Oph : (20180616; eclipsingPorb= 0.06242786 d)
ASASSN-14gb (20180616, precursor outburst 20180612–14?)
V725 Aql (20180614)
ASASSN-18mp # (20180613; eclipsing, Porb= 0.06236 ± 0.00001 d; precursor on 20180608?)
CSS J221822.9+344511 (20180613)
V1047 Aql (20180612)
CSS J221822.9+344511 (20180612)
EF Peg # (20180610)
VW CrB (20180609)
RX Vol (20180609)
VW Hyi (20180605)
V503 Cyg (20180531)
ASASSN-18lc (20180524; superhump period 0.06092(4) d)
SDSS J141118.31+481257.6 # (20180519; WZ Sge-type helium dwarf nova)

Z Cam-type dwarf novae at standstill
NY Ser # (since about 20180529; UGSU; spectroscopy is required)
HL CMa (since 20180514)
AT Cnc (20180202–20180508)
TZ Per (since 20171226)
HL CMa (20171221–20180426) 
IW And (since about 20171219)
NY Ser # (~20180120–20180317, ~56 days; UGSU)
Z Cam (20170405–20171207, 246 days)
IW And (20170812–20170831, 19 days)
OQ Car (20160415–20170826, 498 days)

# indicates a noteworthy or unusual outburst
:  indicates confirmation required
'Activity At A Glance' is gleaned from observations reported to AAVSO MyNewsFlash, BAAVSS-Alert, CVnet-Outburst, VSObs-share and VSNET-outburst. We sincerely thank all the observers who contribute timely observations and reports of activity to these email lists.


Updated 21 May 2018

For new papers on CV's see astro-ph

M. J. Darnley, S. Starrfield

Mariko Kimura, Keisuke Isogai, Taichi Kato, Kenta Taguchi, Yasuyuki Wakamatsu, Franz-Josef Hambsch, Berto Monard, Gordon Myers, Shawn Dvorak, Peter Starr, Stephen M. Brincat, Enrique de Miguel, Joseph Ulowetz, Hiroshi Itoh, Geoff Stone, Daisaku Nogami

Joseph Patterson et al.

Paula Szkody, Mark E. Everett, Zhibin Dai, Donald Serna-Grey

John R. Thorstensen, Frederick A. Ringwald, Cynthia J. Taylor, Holly A. Sheets, Christopher S. Peters, Julie N. Skinner, Erek H. Alper, Kathryn E. Weil

Mariko Kato (Keio Univ.), Izumi Hachisu (Univ. of Tokyo), Hideyuki Saio (Tohoku Univ.)

E. Aydi, K. L. Page, N. P. M. Kuin, M. J. Darnley, F. M. Walter, P. Mróz, D. Buckley, S. Mohamed, P. Whitelock, P. Woudt, S. C. Williams, M. Orio, R. E. Williams, A. P. Beardmore, J. P. Osborne, A. Kniazev, V. A. R. M. Ribeiro, A. Udalski, J. Strader, L. Chomiuk

Michael M. Shara, Trisha F. Doyle, Ashley Pagnotta, James T. Garland, Tod R. Lauer, David Zurek, Edward A. Baltz, Ariel Goerl, Attay Kovetz, Tamara Machac, Juan Madrid, Joanna Mikolajewska, J. D. Neill, Dina Prialnik, Doug L. Welch, Ofer Yaron

J.M Hameury & J.P Lasota

V. V. Lukin, K. L. Malanchev, N. I. Shakura, K. A. Postnov, V. M. Chechetkin, V. P. Utrobin

Authors: A. F. Pala, B. T. Gänsicke, D. Townsley, D. Boyd, M. J. Cook, D. De Martino, P. Godon, J. B. Haislip, A. A. Henden, I. Hubeny, K. M. Ivarsen, S. Kafka, C. Knigge, A. P. LaCluyze, K. S. Long, T. R. Marsh, B. Monard, J. P. Moore, G. Myers, P. Nelson, D. Nogami, R. Pickard, G. Poyner, D. E. Reichart, D. Rodriguez Perez, M. R. Schreiber, J. Shears, E. M. Sion, R. Stubbings, P. Szkody, M. Zorotovic

Liam K Hardy, Martin J McAllister, Vik S Dhillon, Stuart P Littlefair, Madelon C P Bours, Elme Breedt, Tim Butterley, Anurak Chakpor, Puji Irawati, Paul Kerry, Tom R Marsh, Steven G Parsons, Chris D J Savoury, Richard W Wilson, Patrick A Woudt