BD+24 719 : New RR Lyr-type star ?
The object was found to be variable (7.2-8.3) by K.A.A. and Yu.V.B. on 171 photovisual plates of the Sky Patrol of the Odessa State University (JD 2439418-49014). Co-ordinates (1950): R.A.=4h55m49s, Dec=+24o25'14". The photovisual brightness of the comparison stars is
BD+23 756 6.68 23 750 7.89 23 767 8.93 23 766 8.45 23 782 8.46 24 722 7.61
The periodogram analysis was made by I.L.A. by using the methods of Lafler and Kinman (1965) and Deeming (1970). Two daily-biased frequencies f=2.444653 (P=0.4087387d) and 1.443822 (P=0.6926062d) cycles/day correspond to best one-wave light curves. The object was most bright at HJD 2445264.5604 (initial epoch). The observations obtained at JD 2439418-44256 show no variations (except two fadings), thus it is possible that the variations started after this date. This may explain why the variability of such bright object was not discovered earlier.
New observations are needed to determine the correct period and to check whether the star become variable only after JD 2444256.
Please inform us about Your findings on this object
References: Deeming T.J.: 1970 M.N.R.A.S., 147, 365. Lafler J., Kinman T.D.: 1965, Ap.J.Suppl., 11, 216. K.A.Antoniuk Yu.V.Beletskij I.L.Andronov Department of Astronomy Odessa State University T.G.Shevchenko Park Odessa 270014 Ukraine
Dear VSNET members;
In the VSNET 863 issue, Prof. Andronov have drawn our attention to the interesting new variable BD+24 719.
In his report, he reported that this star did not show variations during JD 2459418-44256, and after that it seems to start its variation. Because observation of the starting pulsation is important but very rare, I would like to inform you here on the present status of the observations on starting and stopping of variations due to stellar pulsation, which may call more attention of you all to this interesting new RR Lyrae candicate.
Observations of starting and stopping of the stellar pulsation is very important, because it will fix the blue and red edges of the instability strip, and will bring us information to check our understandings of the stellar interior.
However, for observing the START of the pulsation, we need to monitor a non-pulsating, hence non-variable star, and need to wait until it evolves and enters into the instability strip. For this situation, we have only very poor information on this subject. We only have a tip of evidence by Barlai (cited in Waelkens 1995: Unfortunately, I could not attend the IAU Colloq. 155 and missed a chance to see her presentation). Regrettably, we have obtained no convincing observation of the start of the pulsation at all.
When we turn to the observation of STOPPING pulsation, we have interesting observations on a beta Cephei star alpha Vir (Spica), and observations of the decreasing of the pulsation amplitudes of two classical Cepheids, Polaris, and Y Oph. However, latter two stars may not indicate the position of the red edge, because colors of the Polaris and Y Oph seems to indicate that both of the two star is in the middle of the Cepheid strip.
The observations reported by Prof. Andronov may indicate that we've got finally a chance to observe this very rare phenomenon. As well as new observations to confirm variation and clearify period of this star, checking your plate and CCD flames to confirm non-variablity will also be invaluable data.
Hoping fruitfull observations to you all.
References: Brown and Bochonko, 1994, PASP 106, 964 Fernie, et al. 1993, ApJ 416, 820 Fernie 1990 PASP 102, 905 Odell and Pesnell, 1995, in "Stellar Evolution: What should be done", 32nd Liege International Astrophysical Colloq. p417-422. Shobbrook, et al. 1972, MN 156, 165. Waelkens, 1995, in "Astrophysical Applications of Stellar Pulsation" (ASP Conf. Ser. 83), p24-30. (and references there in) -- % Toshihito ISHIDA, Ph. D., Astrophysicist % % Nishi-Harima Astronomical Observatory, Sayo-cho, Hyogo 679-53, JAPAN % % Tel: +81-790-82-3886 ext. 142 Telefax: +81-790-82-3514 % % e-mail: email@example.com (usual) HQA01560@niftyserve.or.jp (off time) %
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