July 12, 2004 Pulsating PMS stars

Pulsating Pre-Main Sequence Stars in Young Open Clusters

K. ZwintzInstitute 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)

July 12, 2004 Pulsating PMS stars

Pre-main Sequence Starsbirthline ZAMShigh 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 stripambiguous determination of evolutionary stage for field stars!

July 12, 2004 Pulsating PMS stars

PMS evolutionary stage

1.6, 2.0 and 2.5 MsunMS & post-MS evolutionPMS tracks by D’Antona & Mazzitelli (1994)BE / BEF: blue edge for radial overtones / fundamental modeREobs: empirical red edge

(Breger & Pamyatnykh, 1998)

similar envelope properties differences in interior

log

L/L s

un

log Teff

July 12, 2004 Pulsating PMS stars

Young Open ClustersCluster 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

July 12, 2004 Pulsating PMS stars

13.5’NGC 6383

Observations– CTIO 0.9m telescope– Johnson B & V– CCD time series

photometry– 9 nights

July 12, 2004 Pulsating PMS stars

NGC 6383Observations– 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)

170198

July 12, 2004 Pulsating PMS stars

PMS Pulsators in NGC 6383NGC 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

July 12, 2004 Pulsating PMS stars

NGC 6383: Radial Pulsation Models

freq amp (V) amp (B) phase diff.[c/d] [m mag] [m m ag]14.376 13.8 17.6 -0.24319.436 11.6 14.9 -0.09213.766 9.8 12.5 0.4748.295 8.6 11.4 0.03517.653 7.7 9.7 -0.050

170 f1: 3rd overtone & f2: 5th overtone198 3rd overtone

NGC 6383 170

NGC 6383 198freq amp (V) amp (B) phase diff.[c/d] [mmag] [m mag]19.024 20.8 26.4 0.114 log Teff

log

L/L s

un

July 12, 2004 Pulsating PMS stars

IC 49966'Observations

– OSN 1.5m telescope– Johnson B & V– CCD time series

photometry– 10 nights

July 12, 2004 Pulsating PMS stars

IC 4996Observations– 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

3740

July 12, 2004 Pulsating PMS stars

PMS Pulsators in IC 4996IC 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

July 12, 2004 Pulsating PMS stars

NGC 2264NGC 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]

Pow

er [

mm

ag2 ]

July 12, 2004 Pulsating 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 Teff

log

g

July 12, 2004 Pulsating PMS stars

PMS Instability Strip

total 24 stars

REPMS

no stars ?

July 12, 2004 Pulsating PMS stars

Conclusionadditional 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 evolutionradial and non-radial PMS pulsation models Organisation of PMS working group– contact: zwintz@astro.univie.ac.at