1. July 12, 2004Pulsating PMS stars Pulsating Pre-Main Sequence Stars in Young Open Clusters K. Zwintz Institute of Astronomy, Univ. Vienna, Austria zwintz@astro.univie.ac.at M. Marconi (INAF Astr. Observatory of Capodimonte, Naples) T. Kallinger (Inst. of Astronomy, Univ. Vienna) W. W. Weiss (Inst. of Astronomy, Univ. Vienna)

2. July 12, 2004Pulsating PMS stars Pre-main Sequence Stars birthline  ZAMS high degree of activity – photometric & spectroscopic variabilities – interaction with stellar environment – strong IR and/or UV excess – emission lines part of activity due to pulsation: A-F stars – 24 PMS pulsators known – Periods: 18 min … 6 h – short time in instability strip ambiguous determination of evolutionary stage for field stars!

3. July 12, 2004Pulsating PMS stars PMS evolutionary stage 1.6, 2.0 and 2.5 Msun MS & post-MS evolution PMS tracks by D’Antona & Mazzitelli (1994) BE / BE F : blue edge for radial overtones / fundamental mode RE obs : empirical red edge (Breger & Pamyatnykh, 1998)  similar envelope properties  differences in interior log L/L sun log T eff

4. July 12, 2004Pulsating PMS stars Young Open Clusters Cluster Properties – same age and distance – age < few 10 7 yr – main sequence till ~ B9 – A-F members lie above ZAMS Observed Clusters – NGC 6383 new pulsators! – IC 4996 new pulsators! – NGC 2264 first detection of period changes

5. July 12, 2004Pulsating PMS stars 13.5’ NGC 6383 Observations – CTIO 0.9m telescope – Johnson B & V – CCD time series photometry – 9 nights

6. July 12, 2004Pulsating PMS stars NGC 6383 Observations – CTIO 0.9m telescope – Johnson B & V – CCD time series photometry – 9 nights NGC 6383 – Sgr OB1 association – age ~ 1.7 Myr – PMS A-F members – diameter = 20' 2 PMS pulsating cluster members: NGC 6383 170 & 198 (Zwintz et al., 2004) 170 198

7. July 12, 2004Pulsating PMS stars PMS Pulsators in NGC 6383 NGC 6383 170 – V = 12.61 mag – A5 IIIp (van den Ancker et al. 2000) – H  in emission – IR excess – 5 frequencies 8.3 … 19.4 c/d V filter NGC 6383 198 – V = 12.83 mag – no spectral type – f = 19.024 c/d P ~ 1.26 h V filter

8. July 12, 2004Pulsating PMS stars NGC 6383: Radial Pulsation Models 170  f 1 : 3 rd overtone & f 2 : 5 th overtone 198  3 rd overtone NGC 6383 170 NGC 6383 198 log T eff log L/L sun

9. July 12, 2004Pulsating PMS stars IC 4996 6'6' Observations – OSN 1.5m telescope – Johnson B & V – CCD time series photometry – 10 nights

10. July 12, 2004Pulsating PMS stars IC 4996 Observations – OSN 1.5m telescope – Johnson B & V – CCD time series photometry – 10 nights IC 4996 – Cygnus SFR – age ~ 7.5 Myr – PMS A-F members – diameter = 6' 2 PMS pulsating cluster members: IC 4996 37 & 40 37 40

11. July 12, 2004Pulsating PMS stars PMS Pulsators in IC 4996 IC 4996 40 – V = 15.03 mag – A4 (Delgado et al. 1999) – P ~ 42.9 min – 5 th radial overtone IC 4996 37 – V = 15.30 mag – A5 (Delgado et al. 1999) – P ~ 45.2 min – 4 th radial overtone V filter

12. July 12, 2004Pulsating PMS stars NGC 2264 – age ~ 8 Myr – known PMS pulsators: V588 Mon V589 Mon – multi-site campaign Detection of Period Changes – Breger (1972) – Peña et al. (2002) observations from 1986 (Kallinger, 2004, priv. comm.) frequency [c/d] Power [mmag 2 ]

13. July 12, 2004Pulsating PMS stars V589 Mon – Period Change predictions for PMS  Scuti stars (Breger & Pamyatnykh, 1998) – P-change = 75…100·10 -8 yr - 1 measurements for V589 Mon – P-change = 3625·10 -8 yr -1 more rapid evolution than expected ? Factor 35-40 higher (Pamyatnykh & Kallinger, 2004, priv. comm.) log T eff log g

14. July 12, 2004Pulsating PMS stars PMS Instability Strip total 24 stars RE PMS no stars ?

15. July 12, 2004Pulsating PMS stars Conclusion additional PMS pulsators needed – empirical definition of PMS instability strip – observed lack of stars near red edge poor number statistics ? evolutionary effect ? overlap with T Tauri stars ? period changes & stellar evolution radial and non-radial PMS pulsation models Organisation of PMS working group – contact: zwintz@astro.univie.ac.at