FG Sagittae: New observations in the R CrB photometric phase

Архипова, В. П.; Иконникова, Н. П.; Комиссарова, Г. В.; Noskova, R. I.; Shugarov, S. Yu.; Есипов, В. Ф.

doi:10.1134/1.1624462

Cited by 23 publications

(39 citation statements)

References 11 publications

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“…Figure 1 presents the evolution of the color indices of these two stars in the dereddened 3 (U − B, B − V) diagram. This evolution is very similar to the one of classical symbiotic stars (see e.g., Arkhipova & Noskova 1985). Table 1 lists the individual photometric measurements in the Geneva system, which are too sparse to derive a meaningful lightcurve.…”

Section: Binary S Stars Among the Henize Samplementioning

confidence: 70%

The Henize sample of S stars

Eck

Jorissen

2002

A&A

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Abstract. The properties of the few symbiotic stars detected among the 66 binary S stars from the Henize sample are discussed. Two stars (Hen 18 and Hen 121) exhibit both a strong blue-violet continuum and strong H α emission (FWHM of 70 km s −1 ), whereas Hen 134 and 137 exhibit weak H α emission. The H α profiles are typical of non-dusty symbiotic stars belonging to class S-3 as defined by Van Winckel et al. (1993, A&AS 102, 401). In that class as in the Henize symbiotic S stars, He I, [N II] or [S II] emission lines are absent, suggesting that the nebular density is high but the excitation rather low. The radial velocity of the centre of the H α emission is identical to that of the companion star (at least for Hen 121 where this can be checked from the available orbital elements), thus suggesting that the H α emission originates in gas moving with the companion star. For Hen 121, this is further confirmed by the disappearance of the ultraviolet Balmer continuum when the companion is eclipsed by the S star. Hen 121 is thus the second eclipsing binary star discovered among extrinsic S stars (the first one is HD 35155). A comparison of the available data on orbital periods and H α emission leads to the conclusion that H α emission in S stars seems to be restricted to binary systems with periods in the range 600-1000 d, in agreement with the situation prevailing for red symbiotic stars (excluding symbiotic novae). Symbiotic S stars are found among the most evolved extrinsic S stars.

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Section: Binary S Stars Among the Henize Samplementioning

confidence: 70%

The Henize sample of S stars

Eck

Jorissen

2002

A&A

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“…These include, for example, SAO 244567 Arkhipova et al 2013a) and IRAS 18062+2410 (Arkhipova et al 1999). …”

Section: Introductionmentioning

confidence: 99%

Variability and possible rapid evolution of the hot post-AGB stars Hen 3-1347, Hen 3-1428, and LSS 4634

Архипова¹,

Бурлак²,

Есипов³

et al. 2014

Astron. Lett.

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We present the results of spectroscopic and photometric observations for three hot southernhemisphere post-AGB objects, Hen 3-1347 = IRAS 17074-1845, Hen 3-1428 = IRAS 17311-4924, and LSS 4634 = IRAS 18023-3409. In the spectrograms taken with the 1.9-m telescope of the South African Astronomical Observatory (SAAO) in 2012, we have measured the equivalent widths of the most prominent spectral lines. Comparison of the new data with those published previously points to a change in the spectra of Hen 3-1428 and LSS 4634 in the last 20 years. Based on ASAS data, we have detected rapid photometric variability in all three stars with an amplitude up to 0.3 mag, 0.4 mag in the V band. A similarity between the patterns of variability for the sample stars and other hot protoplanetary nebulae is pointed out. We present the results of U BV observations for Hen 3-1347, according to which the star undergoes rapid irregular brightness variations with maximum amplitudes ∆V =0.25 mag, ∆B=0.25 mag, and ∆U =0.30 mag and shows color-magnitude correlations. Based on archival data, we have traced the photometric history of the stars over more than 100 years. Hen 3-1347 and LSS 4634 have exhibited a significant fading on a long time scale. The revealed brightness and spectrum variations in the stars, along with evidence for their enhanced mass, may be indicative of their rapid post-AGB evolution.Keywords: post-AGB stars, planetary nebulae, photometric and spectroscopic observations, photometric variability. * E-mail: ikonnikova@gmail.com 2 INTRODUCTIONThe post-asymptotic giant branch (post-AGB) phase of evolution of intermediate-mass stars (M ZAMS = 0.8 − 8M ⊙ ) is the transition period from the asymptotic giant branch (AGB) to planetary nebula nuclei.Protoplanetary nebulae are stars of spectral types from late G to early B with extended atmospheres surrounded by dust envelopes formed through intense mass loss at previous evolutionary phases. The dust envelopes gradually dissipate, which is reflected in the visibility of the stars at optical wavelengths.The studies of post-AGB stars were begun in the mid-1980s after the appearance of the IRAS survey. These objects were initially suspected and subsequently revealed among the supergiant stars with dust envelopes detected in this survey (Parthasarathy and Pottasch 1986;van der Veen et al. 1989;Hrivnak et al. 1989).An important feature of post-AGB stars is their photometric variability. The type of variability depends on the star's effective temperature, i.e., on its position on the horizontal evolutionary track. In particular, F-G supergiants with infrared excesses exhibit semiregular brightness variations with time scales from 40 to 130 days caused by their pulsational instability (Hrivnak and Lu 2000;Kiss et al. 2007;Arkhipova et al. 2010;Hrivnak et al. 2010). Hotter stars, early B supergiants with infrared excesses, exhibit photometric variability without any distinct periodicity with amplitudes from 0 m .2 to 0 m .4 in the V band on time scales from one day to several days (Hrivnak a...

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“…The 488 days suggested by Arkhipova & Noskova (1988) is definitively ruled out by our data, while the 478.2 days indicated by Arkhipova et al (1995) performs only marginally better with a high dispersion affecting the folded lightcurve.…”

Section: Lt Delmentioning

confidence: 61%

“…Fig. 3), with mean values B = 14.41 and B−V = +1.32 identical to those of Arkhipova et al (1995) for LT Del in quiescence. A period search revealed a strong periodicity at 465.…”

Section: Lt Delmentioning

confidence: 81%

“…The quiescent lightcurve of LT Del displays a strong reflection/heating effect with amplitudes ∆U = +1.7, ∆B = 0.5 and ∆V = 0.2 mag, that Arkhipova & Noskova (1988) reported to follow the ephemeris Min = 2445910 + 488 × E, later revised to Min = 2445910 + 478.2 × E by Arkhipova et al (1995). The latter listed B = 14.4 and B −V = +1.3 as mean values for quiescence.…”

Section: Lt Delmentioning

confidence: 99%

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Symbiotic stars on Asiago archive plates. II

Munari

Jurdana-Šepić

2002

A&A

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Abstract. The Asiago photographic archive has been searched for plates containing the symbiotic stars Hen 2-468, QW Sge, LT Del, V407 Cyg, K 3-9, V335 Vul, FG Ser and Draco C-1. A total of 635 plates imaging the program stars have been found and the brightness estimated using the Henden & Munari (2000) UBV(RI)C photometric sequences. These historical data have allowed for the first time the determination of the orbital periods of Hen 2-468 (774 days) and QW Sge (390.5 days), a significant improvement in the orbital period of LT Del (465.6 days) and for V407 Cyg an evaluation of the Mira's pulsation period and complex lightcurve shape in the red (R and I bands). Some previously unknown outbursts have been discovered too.

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FG Sagittae: New observations in the R CrB photometric phase

Cited by 23 publications

References 11 publications

The Henize sample of S stars

The Henize sample of S stars

Variability and possible rapid evolution of the hot post-AGB stars Hen 3-1347, Hen 3-1428, and LSS 4634

Symbiotic stars on Asiago archive plates. II

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