pulsating pre-main sequence stars in young open clusters
DESCRIPTION
Pulsating Pre-Main Sequence Stars in Young Open Clusters. K. Zwintz Institute of Astronomy, Univ. Vienna, Austria [email protected]. M. Marconi ( INAF Astr. Observatory of Capodimonte, Naples) T. Kallinger (Inst. of Astronomy, Univ. Vienna) - PowerPoint PPT PresentationTRANSCRIPT
July 12, 2004 Pulsating PMS stars
Pulsating Pre-Main Sequence Stars in Young Open Clusters
K. ZwintzInstitute 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, 2004 Pulsating PMS stars
Pre-main Sequence Stars
birthline 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 strip
ambiguous 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
su
n
log Teff
July 12, 2004 Pulsating PMS stars
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
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 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
July 12, 2004 Pulsating 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
July 12, 2004 Pulsating PMS stars
NGC 6383: Radial Pulsation Models
freq am p (V) am p (B) phase diff.[c/d] [m m ag] [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] [mmag]19.024 20.8 26.4 0.114 log Teff
log
L/L
su
n
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 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
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 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.)
frequency [c/d]
Pow
er
[mm
ag
2]
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
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 evolutionradial and non-radial PMS pulsation models Organisation of PMS working group– contact: [email protected]