2018A&A...610A..70B


Query : 2018A&A...610A..70B

2018A&A...610A..70B - Astronomy and Astrophysics, volume 610A, 70-70 (2018/2-1)

Short-term variability and mass loss in Be stars. III. BRITE and SMEI satellite photometry of 28 Cygni.

BAADE D., PIGULSKI A., RIVINIUS T., CARCIOFI A.C., PANOGLOU D., GHOREYSHI M.R., HANDLER G., KUSCHNIG R., MOFFAT A.F.J., PABLO H., POPOWICZ A., WADE G.A., WEISS W.W. and ZWINTZ K.

Abstract (from CDS):

Context. Be stars are important reference laboratories for the investigation of viscous Keplerian discs. In some cases, the disc feeder mechanism involves a combination of non-radial pulsation (NRP) modes.
Aims. We seek to understand whether high-cadence photometry can shed further light on the role of NRP modes in facilitating rotation-supported mass loss.
Methods. The BRITE-Constellation of nanosatellites obtained mmag photometry of 28 Cygni for 11 months in 2014-2016. We added observations with the Solar Mass Ejection Imager (SMEI) in 2003-2010 and 118 Hα line profiles, half of which were from 2016.
Results. For decades, 28 Cyg has exhibited four large-amplitude frequencies: two closely spaced frequencies of spectroscopically confirmed g modes near 1.5c/d, one slightly lower exophotospheric (Stefl) frequency, and at 0.05c/d the difference (Δ) frequency between the two g modes. This top-level framework is indistinguishable from η Cen (Paper I, Baade et al., 2016A&A...588A..56B)), which is also very similar in spectral type, rotation rate, and viewing angle. The circumstellar (Stefl) frequency alone does not seem to be affected by the Δ frequency. The amplitude of the Δ frequency undergoes large variations; around maximum the amount of near-circumstellar matter is increased and the amplitude of the Stefl frequency grows by a factor of a few. During such brightenings dozens of transient spikes appear in the frequency spectrum; these spikes are concentrated into three groups. Only 11 frequencies were common to all years of BRITE observations.
Conclusions. Be stars seem to be controlled by several coupled clocks, most of which are not very regular on timescales of weeks to months but function for decades. The combination of g modes to the slow Δ variability and/or the atmospheric response to it appears significantly non-linear. As in η Cen, the Δ variability seems to be mainly responsible for the modulation of the star-to-disc mass transfer in 28 Cyg. A hierarchical set of Δ frequencies may reach the longest known timescales of the Be phenomenon.

Abstract Copyright: © ESO 2018

Journal keyword(s): circumstellar matter - stars: emission-line, Be - stars: mass-loss - stars: oscillations - stars: individual: 28 Cygni

VizieR on-line data: <Available at CDS (J/A+A/610/A70): btr15.dat btr16.dat smei.dat>

Simbad objects: 21

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Number of rows : 21
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 * alf Eri Be* 01 37 42.84548 -57 14 12.3101 -0.36 0.30 0.46 0.49 0.60 B6Vpe 464 0
2 M 77 GiP 02 42 40.7091669408 -00 00 47.859690204 9.70 9.61 8.87 10.1 9.9 ~ 4425 2
3 * psi Per Be* 03 36 29.3798227 +48 11 33.478941 3.60 4.17 4.23     B5Ve 406 0
4 * psi01 Ori Be* 05 24 44.8273848312 +01 50 47.201915688 3.83 4.76 4.96 5.04 5.26 B1Vn 344 0
5 * 10 CMa Be* 06 44 28.4671043496 -31 04 13.892357820 4.18 5.08 5.17 5.15 5.17 B2V 140 0
6 * kap CMa Be* 06 49 50.4593263 -32 30 30.522482 2.73 3.68 3.89 3.91 4.05 B1.5Ve 280 0
7 * 27 CMa Be* 07 14 15.2119175 -26 21 09.031206 3.76 4.45 4.65 4.64 4.73 B4Ve_sh 225 0
8 * ome CMa Be* 07 14 48.6538664 -26 46 21.609714 2.90 3.64 3.82 3.80 3.90 B2.5Ve 345 0
9 * zet Pup BY* 08 03 35.04754 -40 00 11.3321 0.89 1.98 2.25 2.36 2.58 O4I(n)fp 1139 1
10 NGC 4725 Sy2 12 50 26.5716367992 +25 30 02.733090588   13.45 12.44     ~ 662 2
11 * mu. Cen Be* 13 49 36.9886294 -42 28 25.429594 2.37 3.27 3.43 3.41 3.50 B2Vnpe 427 0
12 NAME Circinus Galaxy Sy2 14 13 09.906 -65 20 20.47   10.89 9.84 10.6 10.0 ~ 1127 2
13 * eta Cen Be* 14 35 30.4241610 -42 09 28.170782 1.30 2.12 2.31 2.41 2.59 B2Ve 334 0
14 * zet Oph Be* 16 37 09.5390545 -10 34 01.529471 1.73 2.58 2.56 2.46 2.50 O9.2IVnn 1806 2
15 VSX J200906.4+365552 V* 20 09 06.42 +36 55 52.7           ~ 1 0
16 * b02 Cyg Be* 20 09 25.6190611128 +36 50 22.633958400 4.03 4.80 4.93     B2.5Ve 259 0
17 IRAS 20081+3642 V* 20 10 00.6351580656 +36 51 11.575002024       14.339   ~ 2 0
18 HD 192685 ** 20 15 15.8960557510 +25 35 31.062881681   4.58 4.75     B3V 137 0
19 * lam Cyg ** 20 47 24.53766 +36 29 26.5737 3.93 4.43 4.54 4.58 4.69 B5V 298 0
20 * nu. Cyg ** 20 57 10.4190684 +41 10 01.699109 3.96 3.96 3.94 3.89 3.89 A0IIIn 155 0
21 HD 201433 ** 21 08 38.88977 +30 12 20.2935           ~ 94 0

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2023.01.31-07:29:39

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