2020A&A...641A..74H


C.D.S. - SIMBAD4 rel 1.7 - 2020.11.28CET21:52:41

2020A&A...641A..74H - Astronomy and Astrophysics, volume 641A, 74-74 (2020/9-1)

Pulsating chromosphere of classical Cepheids. Calcium infrared triplet and Hα profile variations.

HOCDE V., NARDETTO N., BORGNIET S., LAGADEC E., KERVELLA P., MERAND A., EVANS N., GILLET D., MATHIAS P., CHIAVASSA A., GALLENNE A., BREUVAL L. and JAVANMARDI B.

Abstract (from CDS):


Context. It has recently been shown that the infrared (IR) emission of Cepheids, constant over the pulsation cycle, might be due to a pulsating shell of ionized gas with a radius of about 15% of that of the star radius, which could be attributed to the chromospheric activity of Cepheids.
Aims. The aim of this paper is to investigate the dynamical structure of the chromosphere of Cepheids along the pulsation cycle and to quantify its size.
Methods. We present Hα and calcium near-infrared triplet (Ca IR) profile variations using high-resolution spectroscopy with the UVES spectrograph of a sample of 24 Cepheids with a good period coverage from ≃3 to 60 days. After a qualitative analysis of the spectral line profiles, we quantified the Van Hoof effect (velocity gradient between the Hα and Ca IR) as a function of the period of the Cepheids. We then used the Schwarzschild mechanism (a line doubling due to a shock wave) to quantify the size of the chromosphere.
Results. We find a significant Van Hoof effect for Cepheids with a period larger than P=10-days. In particular, Hα lines are delayed with a velocity gradient up to Δv≃30km/s compared to Ca IR. By studying the shocks, we find that the size of the chromosphere of long-period Cepheids is of at least ≃50% of the stellar radius, which is consistent at first order with the size of the shell made of ionized gas previously found from the analysis of IR excess. Last, for most of the long-period Cepheids in the sample, we report a motionless absorption feature in the Hα line that we attribute to a circumstellar envelope that surrounds the chromosphere.
Conclusions. Analyzing the Ca IR lines of Cepheids is of importance to potentially unbias the period-luminosity relation from their IR excess, particularly in the context of forthcoming observations of radial velocity measurements from the Radial Velocity Spectrometer on board Gaia, which could be sensitive to their chromosphere.

Abstract Copyright: © V. Hocdé et al. 2020

Journal keyword(s): shock waves - techniques: spectroscopic - stars: variables: Cepheids - stars: chromospheres

Simbad objects: 27

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Number of rows : 27

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 * bet Dor cC* 05 33 37.5125319201 -62 29 23.323100433 5.13 4.58 3.76 3.55 3.12 F8/G0Ib 349 0
2 V* T Mon cC* 06 25 12.9997562821 +07 05 08.561189768 8.24 7.20 5.98   4.996 G3Iabv+A0p 447 1
3 * 48 Aur cC* 06 28 34.0875086 +30 29 34.914168 6.73 6.23 5.55   4.777 F5.5-G0Ib 362 0
4 * zet Gem cC* 07 04 06.5307903 +20 34 13.073871 5.20 4.58 3.79   3.082 G1Ib 537 0
5 * y03 Pup cC* 07 38 18.2087613998 -48 36 05.159134325   6.314 5.658 6.94   F7Ib/II 106 0
6 V* VZ Pup cC* 07 38 35.2380584126 -28 29 58.597876520   9.73 8.98     F7.5 132 0
7 V* AH Vel cC* 08 11 59.9670207132 -46 38 39.656138625   6.35 5.76     F7Ib/II 163 0
8 V* RS Pup cC* 08 13 04.2157137938 -34 34 42.691837063 8.89 8.00 6.70   5.453 F8Iab 321 0
9 V* RZ Vel cC* 08 37 01.3029337589 -44 06 52.844429407   8.507 7.260     G1Ib 201 0
10 * l Car cC* 09 45 14.8112246 -62 30 28.451894   4.33 3.40     G5Iab/b 292 1
11 V* WZ Car cC* 10 55 18.7272542108 -60 56 23.951208594   10.40 9.37     F8 133 0
12 V* U Car cC* 10 57 48.1866898409 -59 43 55.880151632 8.31 7.21 6.11   5.073 G5/8Iab 214 0
13 V* S Mus cC* 12 12 47.0194644681 -70 09 06.436474127 7.58 8.80 8.33 7.39 5.196 F6Ib+B5V 239 0
14 * 35 Cru cC* 12 31 40.3301092383 -59 25 26.122369782 6.60 6.19 5.53     F7Ib/II 129 0
15 V* R Mus cC* 12 42 05.0256100705 -69 24 27.196561465 7.65 7.11 6.33   5.499 F7Ib 147 0
16 V* W Vir WV* 13 26 01.9928122042 -03 22 43.429880244   10.33 9.46 9.29 9.393 F2Ibe 284 0
17 V* AV Cir cC* 14 50 30.2962544130 -67 29 51.440008848   8.29 7.44   6.358 F7II 69 0
18 * 26 Cir cC* 14 52 35.2532439095 -63 48 35.417176347   6.66 5.96   4.993 F8II 128 0
19 V* S Nor cC* 16 18 51.8313333962 -57 53 59.253617873 8.15 7.49 6.49   5.427 F8/G0Ib 342 1
20 V* V636 Sco cC* 17 22 46.4807689518 -45 36 51.402120969   7.67 6.74   5.654 F7/8Ib/II 142 1
21 V* U Sgr cC* 18 31 53.3321808602 -19 07 30.262730218 8.50 7.81 6.68   5.413 G1Ib 434 0
22 V* EW Sct cC* 18 37 51.1111080562 -06 47 48.495390706   9.50 7.96     F8Ib/II 99 0
23 V* RU Sct cC* 18 41 56.3817508914 -04 06 38.375080426   10.17 8.82     G5 183 0
24 V* V1496 Aql cC* 18 54 59.5332015184 -00 04 36.365559834   12.2       ~ 15 0
25 V* TT Aql cC* 19 08 13.7497120770 +01 17 55.146226298 8.96 7.86 6.50   5.699 G0/2Ib 261 0
26 V* X Cyg cC* 20 43 24.1918662954 +35 35 16.075732392 8.69 7.70 6.47   5.241 F7Ib 441 0
27 * del Cep cC* 22 29 10.2650184 +58 24 54.713856 4.71 4.35 3.75   3.219 F5Iab:+B7-8 682 0

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2020.11.28-21:52:41

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