Cepheids and Gaia's second data release

Transcription

1 The CHARA Array Science Meeting 208 Cepheids and Gaia's second data release Pierre Kervella LESIA, Paris Observatory A. Mérand, A. Gallenne, B. Trahin, S. Borgniet, N. Nardetto, V. Hocdé, R. I. Anderson, W. Gieren, G. Pietrzynski Cepheids and Gaia's second data release

2 THE DISTANCE SCALE Galactic Cepheids Riess et al. 206, ApJ, 826, 56

3 PARALLAX OF PULSATION Radial velocity Expansion Angular diameter Max radius Contraction DU (mas) θ min Min radius θ max Phase

4 6 4 Radius variation (Rsun) DU (mas).75 Angular diameter (milliarcseconds) Variation de Rayon (Rsoleil) Spectroscopy -6 0,0 0, 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9,0 Phase Interferometry / Surface brightness Phase The distance d is given by the relation: d = 2 R(T ) (T ) = 2 kp R T 0 v rad(t) dt UD (T ) UD (0) p = projection factor k = limb darkening correction

5 THE P-FACTOR Pulsational velocity Disk-integrated radial velocity Radial velocity Pure geometry =.5 Limb darkening component < Atmosphere dynamics =? Nardetto et al. (2009, A&A, 502, 95) Main limitation for PoP Cepheid distances

6 Teff Radial velocity (spectroscopy) p=.29 ± 0.02 ± 0.05 Photometry Angular size (interferometry) Fig. 3. Cep data fit. Various panels show pulsation and radial velocities with spline model and residuals (panel a)); angular diameters and residuals, with the baseline color-coded for the data and CSE-biased model as a dash line, based on the model shown in Fig. 2 (panel b)); Mérand et al. 205, A&A, 584, A80

7 RS Puppis Long-period Cepheid P = 4.5 days π = ± mas (4.2%) from its light echoes Kervella et al. (204, A&A, 572, A7)

8 Teff Radial velocity Photometry p=.25 ± 0.06 Angular size (interferometry) Kervella et al. 207, A&A, 600, A27

9 HR-SPIPS Measurement of p-factor through comparison of observed cross-correlation functions to synthetic CCF profiles Post-doc of Simon Borgniet (LESIA) Borgniet et al. 208, A&A, in prep.

10 Interferometric observations of Cepheids 20 More than 000 individual epochs PIONIER % VLTI, 39% CHARA, 9% others 9 4% 3%3% %0% 5% 7% 8% 8% 6% 27% 8% CHARA CLASSIC CHARA FLUOR AMBER SUSI VINCI CHARA MIRC PTI NPOI CHARA VEGA GI2T VEGA GRAVITY alf UMi v* L Car eta Aql bet Dor Y Oph zet Gem del Cep X Sgr W Sgr RS Pup T Mon X Cyg FF Aql Y Sgr U Aql SV Vul V0636 Cas U Car AX Cir U Vul S Vul U Sgr S Sge RZ Vel S Mus BG Cru TT Aql V0440 Per SU Cas MY Pup AW Per RX Cam V0636 Sco T Vul AH Vel CHARA FLUOR CHARA CLASSIC CHARA MIRC CHARA VEGA PTI NPOI SUSI GI2T VEGA VINCI PIONIER AMBER GRAVITY

11 Galactic Cepheids with Gaia Full sample Selected sample ~500 stars 225 stars ~35 stars with optical interferometry (full SPIPS) > PhD thesis of Boris Trahin (supervisors Pierre Kervella & Antoine Mérand) ~200 stars with radial velocities (SBC) ~500 stars with Gaia (+other) photometry + limited RV

12 Binarity: V334 Cyg 203 Orbital velocity (ground) Pulsation velocity (ground) MIRC visual orbit Gallenne et al. (203, A&A, 552, A2) Fig. 6. Left: fitted Pulsation (solid line) period and measured = 3.3 (bluedays dots) orbital velocity. Middle: fitted (solid line) and measured (blue dots) pulsation velocity. Right: orbit of V334 Cyg Ab. The data points are the MIRC results from Table 4. Orbital period = 5.3 years (2009). The final elements derived from our combined fit are Table 5. Fitted orbital and pulsation parameters of V334 Cyg

13 Circumstellar envelopes PhD student Vincent Hocdé (Nice) supervised by Nicolas Nardetto Gallenne et al. (203, A&A, 558, A40) T Mon Tab Detection of CSEs in the visible with VEGA A&A 593, A45 (206) ẟ Cep VEGA data with φ = VEGA data with φ = UD pulsating disk without CSE (SPIPS) UD pulsating disk + CSE UD pulsating disk + CSE (twice fainter) UD pulsating disk + CSE (twice brighter) UD pulsating disk + background 0.8 EE2 squared visibilities SS2 No det Sec 0.2 Included in SPIPS modeling a) UD pulsating disk without CSE (SPIPS) Nardetto et al. 206, A&A, 593, A45 Th X CS in