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Pulsating Pre-Main Sequence Stars in Young Open Clusters

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)

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Pulsating Pre-Main Sequence Stars in Young Open Clusters

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  1. 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) Pulsating PMS stars

  2. 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! Pulsating PMS stars

  3. log L/Lsun log Teff PMS evolutionary stage (Breger & Pamyatnykh, 1998) • 1.6, 2.0 and 2.5 Msun • MS & post-MS evolution • PMS tracks by D’Antona & Mazzitelli (1994) • BE / BEF: blue edge for radial overtones / fundamental mode • REobs: empirical red edge • similar envelope properties  differences in interior Pulsating PMS stars

  4. Young Open Clusters • Cluster Properties • same age and distance • age < few 107 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 Pulsating PMS stars

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

  6. 2 PMS pulsating cluster members: NGC 6383 170 & 198 NGC 6383 (Zwintz et al., 2004) • 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' 170 198 Pulsating PMS stars

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

  8. NGC 6383: Radial Pulsation Models • NGC 6383 170 log L/Lsun • NGC 6383 198 log Teff 170 f1: 3rd overtone & f2: 5th overtone 198 3rd overtone Pulsating PMS stars

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

  10. 40 37 2 PMS pulsating cluster members: IC 4996 37 & 40 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' Pulsating PMS stars

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

  12. Power [mmag2] frequency [c/d] NGC 2264 • 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.) Pulsating PMS stars

  13. log g Factor 35-40 higher log Teff V589 Mon – Period Change • predictions for PMS d 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 ? (Pamyatnykh & Kallinger, 2004, priv. comm.) Pulsating PMS stars

  14. PMS Instability Strip REPMS total 24 stars no stars ? Pulsating PMS stars

  15. 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 Pulsating PMS stars

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