On the frequency and amplitude variations of the delta Scuti star CD-24 7599 (=XX Pyx)

Handler, G.; Pamyatnykh, A. A.; Zima, W.; Sullivan, D. J.; Audard, N.; Nitta, A.

doi:10.1046/j.1365-8711.1998.t01-1-01208.x

Cited by 9 publications

(9 citation statements)

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“…Fitting only the three frequencies of highest amplitude ( f 1 , f 2 , f 3 ) to the 1998 and 1999 data separately (thus minimizing the risk of overfitting the 1999 data) results in the amplitude values collected in Table 4. Such rather large variations in amplitude have been observed before for XX Pyx (Handler et al 1998).…”

Section: Low‐frequency Variationssupporting

confidence: 82%

Low-frequency variability and binarity of theδScuti star XX Pyx

Arentoft

Sterken

Handler

2001

Monthly Notices of the Royal Astronomical Society

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We analyse 147 h of single‐site CCD time series photometry of the multiperiodic low‐amplitude δ Scuti star XX Pyx with the aim of investigating variability at low frequencies. Part of the data were obtained in the context of the 1998 multisite campaign on XX Pyx, the results of which were described by Handler et al. We find that periodic low‐frequency variations are present in the XX Pyx light curves, and we detect two frequencies at fA=0.8695 cycle d−1 and fB=1.7352 cycle d−1, respectively, with amplitudes of 4.5 and 5.4 mmag. The low‐frequency variability is intrinsic to XX Pyx, and cannot be attributed to instrumental or atmospheric effects. The near 2:1 ratio of the frequencies leads us to suggest that XX Pyx is a δ Scuti star in a binary system, with a possible binary period of 27.6 h. This is strongly supported by the detection of radial velocity variations from the re‐analysis of echelle spectra obtained by Handler et al. However, in the absence of a spectroscopic period, alternative explanations of the photometric variability involving pulsation are also possible; the variations occur close to possible combination frequencies of the short‐period (δ Scuti) variations, but high Q values of 0.57 and 0.28 d suggest that the variations are not a result of normal (p‐)modes. They could possibly be due to g‐modes excited to observable amplitudes as a result of resonance effects. Surface features (spots) are unlikely to be the cause of the variations. We searched for combination frequencies ( fi−fj), f being the normal δ Scuti frequencies detected by Handler et al., but failed to detect any.

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Section: Low‐frequency Variationssupporting

confidence: 82%

Low-frequency variability and binarity of theδScuti star XX Pyx

Arentoft

Sterken

Handler

2001

Monthly Notices of the Royal Astronomical Society

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“…Therefore, we cannot infer any significant amplitude variability of the detected terms over the 18.5-d baseline covered by the WIRE observations. It should be noted that some δ Scuti stars do display amplitude variability on this timescale (XX Pyx, Handler et al 1998).…”

Section: The Amplitude Variability Of Modesmentioning

confidence: 99%

Asteroseismology from space: The δ Scuti star θ² Tauri monitored by the WIRE satellite

Poretti

Buzasi

Laher

et al. 2002

A&A

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Abstract. The bright variable star θ2 Tau was monitored with the star camera on the Wide-Field Infrared Explorer satellite. Twelve independent frequencies were detected down to the 0.5 mmag amplitude level. Their reality was investigated by searching for them using two different algorithms and by some internal checks: both procedures strengthened our confidence in the results. All the frequencies are in the range 10.8-14.6 cd −1 . The histogram of the frequency spacings shows that 81% are below 1.8 cd −1 ; rotation may thus play a role in the mode excitation. The fundamental radial mode is not observed, although it is expected to occur in a region where the noise level is very low (55 µmag). The rms residual is about two times lower than that usually obtained from successful groundbased multisite campaigns. The comparison of the results of previous campaigns with the new ones establishes the amplitude variability of some modes.

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“…Significant variation in the amplitudes and frequencies of lowamplitude δ Scuti stars seems to be quite common (see e.g. Breger 1990a;Handler et al 1998;Rodríguez et al 1998). This phenomenon can be well explained by modulation of very closely spaced frequencies or by interaction of resonant modes.…”

Section: Amplitudesmentioning

confidence: 99%

Stability of pulsation of the double-mode high-amplitudeδScuti star AE Ursae Majoris

Pócs

Szeidl

2001

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Abstract. Stability of both the fundamental and first overtone oscillations of AE UMa was investigated by different methods which led to concordant results. The fundamental period of AE UMa has been essentially constant in the past 60 years consistent with the theoretical expectation (Breger & Pamyatnykh 1998). The reported fast period decrease (Hintz et al. 1997) is shown to be incorrect. The constancy of the fundamental period suggests that the star is in the post-main sequence evolutionary state as suggested by the evolutionary theories. The first overtone period is decreasing with a rate of (1/P1)(dP1/dt) = −7.3 10 −8 y −1 . The fact that the rate of period change for two modes is quite different indicates that non-evolutionary effects may also generate period changes. The changes in amplitude of the fundamental and first overtone were examined by comparing the least-squares amplitude solution for different segments of observations. Small long-term variations in the amplitudes have occurred in the past 25 years.

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On the frequency and amplitude variations of the delta Scuti star CD-24 7599 (=XX Pyx)

Cited by 9 publications

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Low-frequency variability and binarity of theδScuti star XX Pyx

Low-frequency variability and binarity of theδScuti star XX Pyx

Asteroseismology from space: The δ Scuti star θ² Tauri monitored by the WIRE satellite

Stability of pulsation of the double-mode high-amplitudeδScuti star AE Ursae Majoris

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On the frequency and amplitude variations of the delta Scuti star CD-24 7599 (=XX Pyx)

Cited by 9 publications

References 0 publications

Low-frequency variability and binarity of theδScuti star XX Pyx

Low-frequency variability and binarity of theδScuti star XX Pyx

Asteroseismology from space: The δ Scuti star θ2 Tauri monitored by the WIRE satellite

Stability of pulsation of the double-mode high-amplitudeδScuti star AE Ursae Majoris

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Asteroseismology from space: The δ Scuti star θ² Tauri monitored by the WIRE satellite