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Alert Notice 529: Observing campaign on 5 variables in Cygnus

October 1, 2015:  Dr. George Wallerstein (University of Washington) has requested AAVSO assistance in monitoring 5 variable stars in Cygnus now through December 2015. He is working to complete the radial velocity curves for these stars, and needs optical light curves for correlation with the spectra he will be obtaining.

Dr. Wallerstein writes: "I need to know the time of max or min so I can assign a phase to each spectrum. Most classical cepheids are quite regular so once a time of max or min can be established I can derive the phase of each observation even if my obs are several cycles away from the established max or min. MZ Cyg is a type II cepheid and they are less regular than their type I cousins." SZ Cyg, X Cyg, VX Cyg, and TX Cyg are all classical Cepheids.

The target list is given below.

Star R.A. and Dec (2000.0) Range (V) Period (d)
SZ Cyg 20 32 54.29 +46 36 04.6 8.92-9.84 15.10965
X Cyg 20 43 24.19 +35 35 16.1  5.85-6.91 16.386332
VX Cyg 20 57 20.83 +40 10 39.0 9.54-10.55 20.133407
TX Cyg 21 00 06.38 +42 35 51.2 8.59-10.02 14.7098
MZ Cyg 21 21 54.73 +37 27 33.1 10.76-12.68 21.4*

*MZ Cyg is in the fuzzy area between Type II Cepheids and RV Tauri stars. 21.4 d is the period for CWA classification, 42.8 d for RVA (revised by S. Otero October 2015.

All targets will be observed by Dr. Wallerstein on the following dates:

0100-0300 UT 2015 October 2, 4
0200-0400 UT 2015 November 3, 4, 30
0200-0400 UT 2015 December 2, 30, 31

V and visual observations are requested. These are long-period Cepheids, so nightly observations are sufficient; many observations made over one night are not necessary.

All observations made during this campaign will be important in determining the times of maxima and minima of these stars.

Charts with comparison star sequences for these objects may be created using the AAVSO's Variable Star Plotter (VSP, https://www.aavso.org/vsp).

Please submit observations to the AAVSO International Database using the names shown in the table.

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

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