SCYON Abstract

Received on February 23 2012

Alessi 95 and the Short Period Cepheid SU Cassiopeiae

AuthorsD.G. Turner (1,9), D.J. Majaess (1,2,9), D.J. Lane (1,2), D.D. Balam (3), W.P. Gieren (4), J. Storm (5), D.W. Forbes (6), R.J. Havlen (7,10), and B. Alessi (8)
Affiliation(1) Department of Astronomy and Physics, Saint Mary's University, Halifax, NS B3H 3C3, Canada
(2) The Abbey Ridge Observatory, Stillwater Lake, NS, Canada
(3) Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC, V6A 3K7, Canada
(4) Departamento de Astronomía, Universidad de Concepción, Casilla 160-C, CL Concepción, Chile
(5) Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
(6) Department of Physics, Sir Wilfred Grenfell College, Memorial University, Corner Brook, Newfoundland A2H 6P9, Canada
(7) 307 Big Horn Ridge, NE, Albuquerque, NM, 87122, U.S.A.
(8) Departamento de Astronomia, Universidade de Sao Paulo, CP 3386, Sao Paulo 01060-970, Brazil
(9) Guest Investigator, Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council of Canada
(10) Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under cooperative agreement with the National Science Foundation
Accepted byMonthly Notices of the Royal Astronomical Society
Links Alessi 95


The parameters for the newly-discovered open cluster Alessi 95 are established on the basis of available photometric and spectroscopic data, in conjunction with new observations. Colour excesses for spectroscopically-observed B and A-type stars near SU Cas follow a reddening relation described by EU-B/EB-V=0.83+0.02EB-V, implying a value of R=AV/EB-V≅2.8 for the associated dust. Alessi 95 has a mean reddening of EB-V(B0)=0.35±0.02 s.e., an intrinsic distance modulus of V0-MV=8.16±0.04 s.e. (±0.21 s.d.), d=429±8 pc, and an estimated age of 108.2 yr, from ZAMS fitting of available UBV}, CCD BV, NOMAD, and 2MASS JHKs observations of cluster stars. SU Cas is a likely cluster member, with an inferred space reddening of EB-V=0.335±0.02 and a luminosity of ‹MV›=-3.15±0.07 s.e., consistent with overtone pulsation, as also implied by the Cepheid's light curve parameters, rate of period increase, and Hipparcos parallaxes for cluster stars. There is excellent agreement of the distance estimates for SU Cas inferred from cluster ZAMS fitting, the infrared surface brightness technique, and Hipparcos parallaxes, which all agree to within a few percent.