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

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!

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

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

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

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 & 198 (Zwintz et al., 2004)

July 12, 2004Pulsating PMS stars PMS Pulsators in NGC 6383 NGC – V = 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 – V = mag – no spectral type – f = c/d P ~ 1.26 h V filter

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 NGC log T eff log L/L sun

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

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 &

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

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 ]

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 higher (Pamyatnykh & Kallinger, 2004, priv. comm.) log T eff log g

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

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: