Properties and nature of Be stars

Božić, H.; Harmanec, P.; Yang, S.; Ziznovsky, J.; Percy, John R.; Ruždjak, Domagoj; Sudar, D.; Šlechta, M.; Škoda, Petr; Krpata, J.; Buil, C.

doi:10.1051/0004-6361:20031732

Cited by 6 publications

(17 citation statements)

References 14 publications

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“…Many stars are known to exhibit this positive correlation: κ Dra (B6IIIpe; Saad et al 2004;Juza et al 1994), 60 Cyg (B1Ve; Koubsky et al 2000), OT Gem (B2Ve; Božić et al 1999), V442 And (B2IVe; Božić et al 2004), EW Lac (B3IVe; Floquet et al 2000), π Aqr (B1Ve; Nordh & Olofsson 1977), QR Vul (B3Ve; Pavlovski et al 1983), µ Cen (B2Vnpe; Dachs et al 1992), φ Per (B2Ve; Božić et al 1995), γ Cas (B0IVe; Doazon et al 1983), 28 Tau (B8IVev;Hirata et al 2000;Tanaka et al 2007), and ω CMa (B2IVe; .…”

Section: Observed Hα and Ubv Correlationsmentioning

confidence: 97%

THE CORRELATION BETWEEN Hα EMISSION AND VISUAL MAGNITUDE DURING LONG-TERM VARIATIONS IN CLASSICAL Be STARS

Sigut

Patel

2013

ApJ

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Hα equivalent widths and UBV magnitudes are calculated for Be star disk models that grow in size and/or density with time. We show that these simple models are consistent with the known Be star classes of positive and inverse correlations between long-term variations in Hα and V magnitude as identified by Harmanec. We support the conclusion of Harmanec that the distinction is controlled by the inclination of the disk to the line of sight. We demonstrate that the strength of these correlations, particularly those of an inverse correlation where the system becomes fainter as the Hα emission strength grows, is strongly influenced by the scale height of the inner Be star disk and the extent of the gravitational darkening of the central B star due to rapid rotation. This dependence may allow coordinated spectroscopic and photometric observations to better constrain these poorly known Be star parameters.

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Section: Observed Hα and Ubv Correlationsmentioning

confidence: 97%

THE CORRELATION BETWEEN Hα EMISSION AND VISUAL MAGNITUDE DURING LONG-TERM VARIATIONS IN CLASSICAL Be STARS

Sigut

Patel

2013

ApJ

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“…The outbursts differed from one cycle to another, but a time-series of the times of maximum light hinted at quasi-regular outbursts for the system. In the year 2000, H emission was detected that verified the Be nature of the system, indicating an outburst period of ∼ 600 d (Božić et al 2004). During most of this photometric cycle, the star was observed in a low-state with little variability followed by outbursts of variable duration and amplitude.…”

Section: Introductionmentioning

confidence: 74%

“…During most of this photometric cycle, the star was observed in a low-state with little variability followed by outbursts of variable duration and amplitude. Božić et al (2004) also analyzed a collection of 35 spectra of HD 6226 taken over a span of ∼ 6 years to further constrain the nature of the variability. The emission profile for H was typically doublepeaked during the outbursts, although the strength varied greatly.…”

Section: Introductionmentioning

confidence: 99%

“…★ E-mail: noel.richardson@erau.edu However, Gandet (2019) showed a blue spectrum obtained shortly after the end of the data analyzed by Božić et al (2004), taken during a time period where there should be no emission with their derived 600-d period, and this spectrum shows clear H emission from a disk. Similarly, Šlechta & Škoda (2005) found H emission at a time when it was predicted to be absent by Božić et al (2004).…”

Section: Introductionmentioning

confidence: 99%

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Outbursts and stellar properties of the classical Be star HD 6226

Richardson,

Thizy,

Bjorkman

et al. 2021

Preprint

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The bright and understudied classical Be star HD 6226 has exhibited multiple outbursts in the last several years during which the star grew a viscous decretion disk. We analyze 659 optical spectra of the system collected from 2017-2020, along with a UV spectrum from the Hubble Space Telescope and high cadence photometry from both TESS and the KELT survey. We find that the star has a spectral type of B2.5IIIe, with a rotation rate of 74% of critical. The star is nearly pole-on with an inclination of 13. • 4. We confirm the spectroscopic pulsational properties previously reported, and report on three photometric oscillations from KELT photometry. The outbursting behavior is studied with equivalent width measurements of H and H , and the variations in both of these can be quantitatively explained with two frequencies through a Fourier analysis. One of the frequencies for the emission outbursts is equal to the difference between two photometric oscillations, linking these pulsation modes to the mass ejection mechanism for some outbursts. During the TESS observation time period of 2019 October 7 to 2019 November 2, the star was building a disk. With a large dataset of H and H spectroscopy, we are able to determine the timescales of dissipation in both of these lines, similar to past work on Be stars that has been done with optical photometry. HD 6226 is an ideal target with which to study the Be disk-evolution given its apparent periodic nature, allowing for targeted observations with other facilities in the future.

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“…HD 6226 is the first star where the spectroscopic variations were predicted from photometric measurements (Božič and Harmanec, 1998). They supposed that the long-term spectroscopic variability should be correlated with the photometric one, having a 481.3 d period (in case it is really a periodic process).…”

Section: Physical Nature Of Hd 6226mentioning

confidence: 99%

An Outburst Detected in the Spectrum of Hd 6226

Šlechta

Škoda

2005

Astrophys Space Sci

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HD 6226 is a bright binary Be star at visual magnitude 6.81 (Hipparcos database). The emission and absorption phases occur in cycles, which are probably not periodic. The suspected period of about 630 days (derived from photometric measurements) is not confirmed by our spectroscopic survey. The latest emission phase developed in the beginning of 2003, then the emission strength systematically decreased and disappeared between July 21, 2003 and August 4, 2003. The last (absorption) spectrum was exposed on August 25, 2003. Unexpected very strong emission appeared in a spectrum exposed on October 28, 2003. A short-term photometric brightening followed this "outburst".Long-term spectroscopic RV studies revealed a 2.615 d period modulated by a 29.7 d period (in the He I 6678 line), which perhaps may be interpreted as orbital period of a binary. Nevertheless, the physical nature of the dominant short 2.615 d period is not yet clear.The last detected emission episode has changed considerably our view of the interesting object HD 6226. We hope this study will reveal more details of the physical properties of the Be phenomenon.

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Properties and nature of Be stars

Cited by 6 publications

References 14 publications

THE CORRELATION BETWEEN Hα EMISSION AND VISUAL MAGNITUDE DURING LONG-TERM VARIATIONS IN CLASSICAL Be STARS

THE CORRELATION BETWEEN Hα EMISSION AND VISUAL MAGNITUDE DURING LONG-TERM VARIATIONS IN CLASSICAL Be STARS

Outbursts and stellar properties of the classical Be star HD 6226

An Outburst Detected in the Spectrum of Hd 6226

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