The roles of rotation and pulsation in the new B- and A-type - PowerPoint PPT Presentation

The roles of rotation and pulsation in the new B- and A-type periodic variables in NGC3766 Nami Mowlavi, + S. Saesen, T. Semaan, P. Eggenberger,F. Barblan, L. Eyer, S. Ekström, C. Georgy (University of Geneva, Switzerland) * New variable stars in NGC 3766 : Reminder → Mowlavi et al. (2013, Paper I) * VLT spectra : New insight → Mowlavi et al. (2016, submitted) N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 1

Stellar pulsation in the HR diagram 5.0 4.5 4.0 3.5 6 log T eff β Cep stars 0.1-0.6 d 4 SPB stars 0.5 - 5 d 2 log L/L ⊙ δ Sct stars 0.02-0.25 d γ Dor stars 0.3-1.7 d 0 Christensen-Dalsgaard (2004) N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 2

Stellar pulsation in the HR diagram 5.0 4.5 4.0 3.5 6 log T eff 4 2 log L/L ⊙ X No pulsation 0 Christensen-Dalsgaard (2004) N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 3

Open cluster NGC 3766 Photom. survey 2002-2009 (1.2m Euler telescope, La Silla) 14 - 30 My → 2545 images in V’ 430 images in B’ 376 images in U’ 1’ ESO Press Release 1326 (2013) N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 4

Open cluster NGC 3766 Photom. survey 2002-2009 (1.2m Euler telescope, La Silla) 14 - 30 My Mowlavi et al. (2013) Mowlavi et al. (2013) SPB 107 γ Dor new periodic δ Sct variables N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 5

Previously reported periodic variables in the gap ? Before Paper I (not exhaustive) * Maia stars (?) Struve (1955), ... , Scholz et al. (1998) * Individual stars Ex: Waelkens et al (1998), Aerts & Kolenberg (2005) * CoRoT Yes, pulsation proposed (Degroote et al. 2009) * Kepler Yes, spots proposed (Balona 2013) * NGC 7654 Yes, but not recognized as such (Luo et al 2012) Since 2013 (not exhaustive) - Lata et al. (2014) “Main-sequence variable stars in young open cluster NGC 1893” - Lata et al. (2016) “Variable stars in young open star cluster NGC 7380” - Balona et al. (2016) “The hot γ Doradus and Maia stars" N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 6

Properties of the new group Mowlavi et al. (2013) NGC 3766 10.0 Number of stars Shorter than SPBs Period 7.5 0.1 – ~0.5 d and 5.0 longer than δ Scts 2.5 0.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 Period (day) NGC 3766 Number of group 2 stars 12.5 Limited by Amplitude 10.0 photometric precision <1 – ~5 mmag 7.5 → extends below mmag 5.0 2.5 0.0 0 1 2 3 4 5 6 7 8 9 10 11 Amplitudes (mmag) N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 7

Origin of variability? ← multi-epoch V r Binary stars ? ← v*sin(i) Role of rotation ? N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 8

Origin of variability? ← multi-epoch V r Binary stars ? ← v*sin(i) Role of rotation ? Spectra taken with VLT/Girafe (LR02 mode) for - all new variables - SPB stars - Many non-periodic stars in same mag range Multi-epoch : for each star, several spectra each night during three consecutive nights N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 9

Result 1: New variables form 2 groups Rotation rates New variability class NGC 3766 12 10 P 1 >0.55 d P 1 <0.55 d Number of stars 8 6 Binaries 4 2 5 SPB 4 Hybrid 3 2 1 0 100 200 300 400 v sin i (km/s) Mowlavi et al. (2016) N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 10

Result 1: New variables form 2 groups Rotation rates Group 1 Group 2 P 1 > 0.55 d P 1 < 0.55 d small v*sin(i) Fast-rotators } } New variability class NGC 3766 12 10 P 1 >0.55 d P 1 <0.55 d Number of stars 8 6 Binaries 4 2 5 SPB 4 Hybrid 3 2 1 0 100 200 300 400 v sin i (km/s) Mowlavi et al. (2016) N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 11

Result 1: New variables form 2 groups Rotation rates Mowlavi et al. (2016) 350 107 5.00 NGC 3766 51 300 2.00 70 84 364 250 ● 1.00 SPB 154 ● ● v sin i (km/s) 58 ● ● 298 ● 278 P phot (d) 0.50 ● ● ● ● ● ● ● ● 200 ● ● ●● ● ● ● ● ● ● ● ● ●● ● ● ● ● ● ● ● γ Dor ● ● ● ● 0.20 ● ● ● ● ● ● ● 150 ● ● FaRPB 0.10 ● 100 0.05 δ Scuti 50 0.02 10 11 12 13 14 15 V' (mag) N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 12

Result 1: New variables form 2 groups Rotation rates Mowlavi et al. (2016) 350 107 5.00 NGC 3766 51 300 2.00 small v*sin(i) 70 84 364 250 ● 1.00 SPB 154 ● ● v sin i (km/s) 58 ● ● 298 ● 278 P phot (d) 0.50 ● ● ● ● ● ● ● ● 200 ● ● ●● ● ● ● ● ● ● ● ● ●● ● ● ● ● ● ● ● γ Dor ● ● ● ● 0.20 ● ● ● ● ● ● ● 150 ● ● } FaRPB FaRPB 0.10 Fa st ● R otating 100 0.05 δ Scuti P eriodic B -type 50 0.02 10 11 12 13 14 15 V' (mag) N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 13

V r → Binarity ? Identification of binaries Expected amplitude of RV variations de Cat (2002) SPBs β Ceps SPBs: A Vr <~ 7 km/s β Ceps: A Vr <~20 km/s → Binary if A Vr >~ 20km/s N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 14

Identification of binaries Binary stars Mowlavi et al. (2016) 350 60 ● 364 NGC 3766 300 50 278 ● 107 ● Binaries 250 v sin i (km/s) 40 Q RV (km/s) 200 154 30 ● 150 20 36 84 51 68 100 10 ● ● 175 ● ● ● ● ● ● ● ● ● ● ●● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●● 50 ● 0 1 2 5 10 A 1 (mmag) N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 15

Identification of binaries Binary stars 0 NGC3766 − 154: P phot = 0.80672 d [ P orb >> 3 d ] ● ● ● ● ● ● ● ● ● − 10 Mowlavi et al. (2016) RV (km/s) − 20 ● ● ● ● ● ● ● ● ● ● ● ● − 30 100 100 NGC3766 − 107: P phot = 4.536 d [ P orb = P phot ] ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● 40 50 50 NGC3766 − 278: P phot,1 = 0.62115 d, P phot,2 = 0.199088 d [ P orb = 2*P phot,1 ] ● ● RV (km/s) RV (km/s) ● ● ● ● ● ● ● ● ● ● ●● 20 ● ●● ● ● ● ● ● ● ● ● 0 0 ● ● ● ●● ● ● ●● RV (km/s) ● ● ● ● ● ● ● ● ● ●● ● ● ● ● ● ● ● ● ● ● ●● ● ● ● 0 ● ● ● ● ● ● ● ● − 50 − 50 ● ● ● ● ● ● ● ● ● ● ● − 20 ● ● ● ● ● ● ● − 100 − 100 ● − 40 ● ● ● ● ● ● ● ● 100 ● ● ● ● − 150 − 150 NGC3766 − 364: P phot = 0.91772 d [ P orb = 2*P phot ] 0.0 0.0 0.5 0.5 1.0 1.0 1.5 1.5 2.0 2.0 50 MJD − 56765 d MJD − 56765 d RV (km/s) 0 ● ● ● ● ●● − 50 ● ● − 100 ● ● 0.0 0.5 1.0 1.5 2.0 MJD − 56765 d N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 16

Result 1: New variables form 2 groups Rotation rates Mowlavi et al. (2016) 350 107 5.00 NGC 3766 51 300 2.00 70 84 364 250 ● 1.00 SPB 154 ● ● v sin i (km/s) 58 ● ● 298 ● 278 P phot (d) 0.50 ● ● ● ● ● ● ● ● 200 ● ● ●● ● ● ● ● ● ● ● ● ●● ● ● ● ● ● ● ● γ Dor ● ● ● ● 0.20 ● ● ● ● ● ● ● 150 ● ● FaRPB FaRPB 0.10 ● 100 0.05 δ Scuti 50 0.02 10 11 12 13 14 15 V' (mag) N. Mowlavi 15/09/2016 STARS 2016 The roles of rotation and pulsation in the new B- and A-type periodic variable stars in NGC3766 17