A Carbon Rich Mira Variable In a Globular Cluster: A Stellar Merger
-
Upload
zephania-lynn -
Category
Documents
-
view
24 -
download
0
description
Transcript of A Carbon Rich Mira Variable In a Globular Cluster: A Stellar Merger
1
A Carbon Rich Mira VariableIn a Globular Cluster:
A Stellar Merger
MW Feast JW Menzies PA WhitelockSAAO and UCT
Published onlineMNRAS Letters
29 Oct 2012
2
N Matsunga (Thesis: Tokyo) 2006Intensive survey of globular clusters
with the IRSFfor variables
Lynga 7 V1
Mira variablePeriod = 551 days
Amplitude ΔK = 1.22 magJ-K
s =4.1 mag
3
Mira variables are;Large amplitude, pulsating AGB stars.
Useful properties;1. They obey
a period- bolometric magnitude relation.2. Their initial (and probably final)
Mass increases with period.3. Their age decrease with period.
551 day Mira expected to be intermediateage objects
4
Next SurpriseSPITZER spectra show
Lynga V1 is a carbon star
Carbon Miras with ~500 day periodAnd very red colours (due to dust shells)Are found in intermediate age clusters
Not globular clustersAnd have initial masses of ~1.5 solar masses
An ages of ~1-2 Gyr
5
6
7
Cluster velocity (Saviane et al. 2012) +22±3 km/s V1 +27±5 km/s
Predicted velocity if in field –81 km/s
Bolometric Mag. from PL –5.2 magBolometric Mag. If cluster member –5.0 mag
8
Thus~ 1.5 solar mass~ 1.5 Gyr oldMira variable
in a~ 13 Gyr old globular cluster
9
FR Ferraro et al. Nature 462, 1028-1031 (2009) doi:10.1038/nature08607
Comparison with collisional and binary-evolution models.
10
Which sequence is most likelyFor the Lynga 7 Mira?
If matter transferred has changes composition(H/He)
It will affect later evolution
Possibly direct collision most likely?
11
Are merged stars important in other contexts?
Does Galactic Bulge contain youngAnd intermediate age stars?
12
13
FR Ferraro et al. Nature 462, 1028-1031 (2009) doi:10.1038/nature08607
The two blue straggler sequences of M30.