Variable Stars

Hoffmeister, Cuno; Richter, G. A.; Wenzel, Wolfgang

doi:10.1007/978-3-642-82269-8

Cited by 61 publications

(47 citation statements)

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“…The observed total amplitude is ΔB = 0.0105 (± 0.0005) mag, and the corresponding ephemeris is min(B) = 2 455 311.140(±0.002)+0.33265(±0.00005) × E. (1) Such a low-amplitude variability, its sinusoidal light curve, and the length of the period are typical of β Cep stars. According to the catalog of β Cep stars of Stankov & Handler (2005, hereafter ST05), their spectral type range from B0 to B3 and the luminosity class from I to V, with two thirds of the total being composed by B1 and B2 stars of luminosity classes III, IV, and V. Their variability is due to pulsations driven by the κ-mechanism (Maeder 2009;Dziembowski & Pamyatnykh 1993;Sterken & Jerzykiewicz 1993;Moskalik & Dziembowski 1992), and the general aspect of their light curves is similar to a sinusoid (Hoffmeister 1985;Sterken & Jaschek 1996). They are rare objects, since the ST05 catalog listing only 93 validated β Cep stars.…”

Section: β Cep Pulsationmentioning

confidence: 99%

Asiago eclipsing binaries program IV. SZ Camelopardalis, aβ Cephei pulsator in a quadruple, eclipsing system

Tamajo

Munari

Siviero

et al. 2012

A&A

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We present a spectroscopic and photometric analysis of the multiple system and early-type eclipsing binary SZ Cam (O9 IV + B0.5 V), which consists of an eclipsing SB2 pair of orbital period P = 2.7 days in a long orbit (∼55 yrs) around a non-eclipsing SB1 pair of orbital period P = 2.8 days. We have reconstructed the spectra of the individual components of SZ Cam from the observed composite spectra using the technique of spectral disentangling. We used them together with extensive and accurate BV I C CCD photometry to obtain an orbital solution. Our photometry revealed the presence of a β Cep variable in the SZ Cam hierarchical system, probably located within the non-eclipsing SB1 pair. The pulsation period is (0.33265 ± 0.00005) days and the observed total amplitude in the B band is (0.0105 ± 0.0005) mag. NLTE analysis of the disentangled spectra provided atmospheric parameters for all three components, consistent with those derived from orbital solution.

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Section: β Cep Pulsationmentioning

confidence: 99%

Asiago eclipsing binaries program IV. SZ Camelopardalis, aβ Cephei pulsator in a quadruple, eclipsing system

Tamajo

Munari

Siviero

et al. 2012

A&A

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“…(Ho †meister, Richter, & Wenzel 1985), where R is the EarthÏs radius vector (^1), L is the longitude of the Sun on the date of the observation, and j, b are the ecliptic coordinates of the system. The ecliptic coordinates were calculated from the right ascension (a), declination (d), and obliquity of the ecliptic using the following formulae :…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Morphologies of Hα Accretion Regions in Algol Binaries

Richards

Albright

1999

ASTROPHYS J SUPPL S

109

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We have investigated a group of 18 Algol-type binaries to determine the general morphologies and physical properties of the accretion regions in these systems. The systems studied were V505 Sgr, RZ Cas, AI Dra, TV Cas, TW Cas, d Lib, RW Tau, TW Dra, b Per, TX UMa, U Sge, S Equ, U CrB, RS Vul, SW Cyg, CX Dra, TT Hya, and AU Mon, in order of increasing orbital period P \ 1.18È11.11 days. In addition, the RS CVn-type binary HR 1099 (V711 Tau) was observed to illustrate the appearance of chromospheric Ha emission. Nearly 2200 time-resolved Ha spectra were collected from 1992 March to 1994 December with the McMath-Pierce Solar Telescope at NSO and mostly with the Coude Feed Telescope at KPNO. The spectra were obtained at phases around the entire orbit of each binary and were closely spaced to permit the detection of transitions in the proÐles. Moreover, the spectra were obtained typically within three orbital cycles to reduce the inÑuence of secular variations. Di †erence proÐles were calculated by subtracting a composite theoretical photospheric spectrum from the observed spectrum.The analysis of the Ha di †erence proÐles demonstrates that the accretion structures in Algol binaries have four basic morphological types : (1) double-peaked emission systems in which the accretion structure is a transient or classical accretion disk ; (2) single-peaked emission systems in which the accreted gas was found along the trajectory of the gas stream and also between the two stars in an accretion annulus ; (3) alternating single-and double-peaked emission systems, which can change between a single-peaked and a double-peaked type within an orbital cycle ; and (4) weak spectrum systems in which there was little evidence of any accretion structure since the di †erence spectra are weak at all phases. The Ðrst two types are the dominant morphologies. The Ðrst type can be interpreted physically as a disklike distribution, while the second is a gas streamÈlike distribution.The most common type in short-period Algols with 2.7 days \ P \ 4.5 days is a predominantly singlepeaked emission feature in the Ha di †erence proÐles (Type 2). This feature is redshifted during the phase interval / D 0.15È0.45 and blueshifted from / D 0.55È0.85. This single-peaked emission is often composed of two closely spaced emission peaks where one peak is at the Ha rest wavelength. The other peak is blueshifted at / D 0.65, where the line of sight is along the length of the approaching gas stream. Systems which display this morphology include RZ Cas, RW Tau, TW Dra, b Per, TX UMa, S Equ, and RS Vul. The orbital variation of the Ha observed proÐles of HR 1099 was similar to that seen in the di †erence spectra of this group and suggests that chromospheric emission may play a signiÐcant role in these binaries. A less common morphological type in the group of short-period Algols was a widely separated double-peaked disk-like distribution (Type 1) where the gas is in a transient or classical accretion disk. All of the long-period systems (P [ 6 days) were f...

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“…Both the period and the time-varying function that represents brightness are of direct scientific interest, for example as an aid to classifying stars into different categories depending on magnitude, period, and light curve shape, for making inferences about stellar evolution, and for determining astronomical distances (Hoffmeister et al, 1985). It is clear that if observations are made at regularly spaced points in time then identification of the brightness function without a structural model may not be possible.…”

Section: Introductionmentioning

confidence: 99%

Nonparametric estimation of a periodic function

Hall¹,

Reimann²,

Rice³

2000

Biometrika

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ABSTRACT. Motivated by applications to brightness data on periodic variable stars, we study nonparametric methods for estimating both the period and the amplitude function from noisy observations of a periodic function made at irregularly spaced times. It is shown that nonparametric estimators of period converge at parametric rates and attain a semiparametric lower bound which is the same if the shape of the periodic function is unknown as if it were known. Also, first-order properties of nonparametric estimators of the amplitude function are identical to those that would obtain if the period were known. Numerical simulations and applications to real data show the method to work well in practice.KEY WORDS AND PHRASES. frequency estimation, nonparametric regression, semiparametric estimation, Nadaraya-Watson estimator, MACHO project, variable star data.

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Variable Stars

Cited by 61 publications

References 0 publications

Asiago eclipsing binaries program IV. SZ Camelopardalis, aβ Cephei pulsator in a quadruple, eclipsing system

Asiago eclipsing binaries program IV. SZ Camelopardalis, aβ Cephei pulsator in a quadruple, eclipsing system

Morphologies of Hα Accretion Regions in Algol Binaries

Nonparametric estimation of a periodic function

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