HD 172468, whereas almost constant for most of the time, suddenly started to drop in brightness to such a low level to become undetectable. We suspect that such an abrupt event may be an "obscurational" minimum, that is typical of eruptive RCB stars, or may be due to the variable extinction by circumstellar dust in a young Orion type object. |
HD172468 = NSV24534 (RA = 18h37m41s, Dec = +51d56'45") According to Astron. Astrophys. 364, 706 (2000), Messima et al. reports that the 7-th mag star HD172468 showed temporary 1-4 mag fadings, and sometimes undetectable by their APT observations. T. Kato reported that the object is not (very) hydrogen-deficient, and looks different from a classical R CrB-type star. The GSC magnitude 11.16 is more than three magnitudes fainter than usual. However, Hipparcos didn't pick up this star as a variable star (vsnet-campaign 886). |
Farbaufnahme von HD172468 (anhand von POSS-II-Platten, Feld: 10'x10') |
Abstract aus Astron. Astrophys. 364, 706-711 (2000) Serendipitous discovery of an irregular and a semi-regular type variable in the field of BY Draconis S. Messina, G. Marino, M. Rodonò, and G. Cutispoto Abstract We present new evidence of the optical variability of two red giant stars: HD 172468 and HK Dra, based on photometric and spectroscopic observations. These stars had been included as check stars in our photometric monitoring program of BY Dra and turned out to be variable. HD 172468, whereas almost constant for most of the time, suddenly started to drop in brightness to such a low level to become undetectable. We suspect that such an abrupt event may be an "obscurational" minimum, that is typical of eruptive RCB stars, or may be due to the variable extinction by circumstellar dust in a young Orion type object. HK Dra, already known as an irregular variable, is characterised by periodic flux modulation with season-to-season changes of the photometric period, as inferred from a periodogram analysis. It also shows changes of the light curve peak-to-peak amplitude and shape. Such a behaviour in giant stars is commonly found among semi-regular giants (SR) at the Asymptotic Giant Branch (AGB). Our radial velocity measurements rule out that HK Dra may be a close binary system. |
Daten der Vergleichssterne
Stern Name V B-V mv Spektrum A Hip91346 6,92 0,432 7,0 F2 B HD172268 7,89 1,256 8,1 K5 C HD171567 8,17 0,786 8,3 K0 var HD172468 7,52 1,247 7,8 K2 |