Building a Comprehensive Picture of Stellar Evolution Natalie M. - - PowerPoint PPT Presentation
Building a Comprehensive Picture of Stellar Evolution Natalie M. Gosnell Assistant Professor, Colorado College September 28, 2018 St. Olaf College Physics Colloquium AIDA: R. Chromik What am I going to talk about today? A large fraction of
Assistant Professor, Colorado College
September 28, 2018
Physics Colloquium
AIDA: R. Chromik
APOD
Jewel Box Cluster (NGC 4755)
VLT Telescopes, ESO/Y. Beletsky
NGC 6819
DSS APOD
NGC 290
www.robgendlerastropics.com
NGC 188
M67
Xanadu Observatory VLT Telescopes, ESO/Y. Beletsky
Created by A. Geller, Northwestern University
Hot (blue) Cool (red)
Movie credit: NASA, ESA, J. Anderson, & R. van der Marel (annotations mine)
Hot (blue) Cool (red)
faint (small)
Movie credit: NASA, ESA, J. Anderson, & R. van der Marel (annotations mine)
Main Sequence faint (small)
Hot (blue) Cool (red)
Subgiants Giant Branch Horizontal Branch
Movie credit: NASA, ESA, J. Anderson, & R. van der Marel (annotations mine)
White Dwarf Sequence
Main Sequence Over time faint (small)
Hot (blue) Cool (red)
Movie credit: NASA, ESA, J. Anderson, & R. van der Marel (annotations mine)
Main Sequence Subgiants Giant Branch faint (small)
Hot (blue) Cool (red)
White Dwarf Sequence Horizontal Branch
Movie credit: NASA, ESA, J. Anderson, & R. van der Marel (annotations mine)
Main Sequence Subgiants Giant Branch faint (small)
Hot (blue) Cool (red)
White Dwarf Sequence
We have reliable models for how a single star will evolve
Horizontal Branch
Movie credit: NASA, ESA, J. Anderson, & R. van der Marel (annotations mine)
APOD
Jewel Box Cluster (NGC 4755)
NGC 188:
0.4 0.6 0.8 1.0 1.2 1.4 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 B - V 16 15 14 13 12 11 V
Stellar color
Bright Faint
Magnitude
1498 stars in the region of the cluster Group of hundreds to thousands of stars
material
Hot Cool
Gosnell 2014, adapted from Geller et al. 2008
Group of hundreds to thousands of stars
material
0.4 0.6 0.8 1.0 1.2 1.4 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 B - V 16 15 14 13 12 11 V
Stellar color
Bright Faint
Magnitude
NGC 188:
1498 stars in the region of the cluster
Hot Cool
Gosnell 2014, adapted from Geller et al. 2008
20 40 RV (km/s) 20 40 60 80 100 120 140 Number of Objects
RV Distribution Cluster Member Distribution Field Population Figure 5. Histogram of the RV distribution of single stars, 4, with
Milliman et al. 2014
Proper motions
Compare modern images with photographic plates from 50–70 years ago
Radial velocities
Requires at least 3 spectra of every star, and years of coverage to obtain binary memberships
Platais & Gosnell et al. 2013
Proper motion movement (x) Proper motion movement (y) Radial velocity (km/s) Number of stars
Stars in cluster Stars in field of galaxy Stars in cluster
Group of hundreds to thousands of stars
material
0.4 0.6 0.8 1.0 1.2 1.4 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 B - V 16 15 14 13 12 11 V
Stellar color
Bright Faint
Magnitude
NGC 188:
1498 stars in the region of the cluster
Hot Cool
Gosnell 2014, adapted from Geller et al. 2008
Group of hundreds to thousands of stars
material
Bright Faint
0.4 0.6 0.8 1.0 1.2 1.4 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 B - V 16 15 14 13 12 11 V
Stellar color Magnitude
NGC 188:
1498 stars in the region of the cluster
Hot Cool
Gosnell 2014, adapted from Geller et al. 2008
0.4 0.6 0.8 1.0 1.2 1.4 1.6 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 1.6 B - V 16 15 14 13 12 11 V 0.4 0.6 0.8 1.0 1.2 1.4 1.6 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 1.6 B - V 16 15 14 13 12 11 V 0.4 0.6 0.8 1.0 1.2 1.4 1.6 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 1.6 B - V 16 15 14 13 12 11 V
V
single star model
Bright Faint
Stellar color
Main Sequence Subgiant Branch Giant Branch small, cool small, hot
large, hot large, cool
Magnitude
Gosnell 2014, adapted from Geller et al. 2008
James Lombardi NASA/AEI/ZIB/M. Koppitz and L. Rezzolla David A. Hardy & PPARC Casey Reed
0.4 0.6 0.8 1.0 1.2 1.4 1.6 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 1.6 B - V 16 15 14 13 12 11 V 0.4 0.6 0.8 1.0 1.2 1.4 1.6 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 1.6 B - V 16 15 14 13 12 11 V 0.4 0.6 0.8 1.0 1.2 1.4 1.6 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 1.6 B - V 16 15 14 13 12 11 V
V
single star model
Bright Faint
Stellar color
Main Sequence Subgiant Branch Giant Branch small, cool small, hot
large, hot large, cool
Magnitude
Gosnell 2014, adapted from Geller et al. 2008
equal-mass binary model
0.4 0.6 0.8 1.0 1.2 1.4 1.6 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 1.6 B - V 16 15 14 13 12 11 V 0.4 0.6 0.8 1.0 1.2 1.4 1.6 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 1.6 B - V 16 15 14 13 12 11 V 0.4 0.6 0.8 1.0 1.2 1.4 1.6 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 1.6 B - V 16 15 14 13 12 11 V 0.4 0.6 0.8 1.0 1.2 1.4 1.6 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 1.6 B - V 16 15 14 13 12 11 V 0.4 0.6 0.8 1.0 1.2 1.4 1.6 16 15 14 13 12 11 0.4 0.6 0.8 1.0 1.2 1.4 1.6 B - V 16 15 14 13 12 11 V
V
Blue stragglers Yellow giants Sub-subgiants Contact binaries X-ray sources
NGC 188
Bright Faint
Stellar color
small, cool small, hot
large, hot large, cool
Magnitude
Gosnell 2014, adapted from Geller et al. 2008
(blue stragglers, yellow giants, sub-subgiants, W UMa)
Stellar products excluded from stellar evolution studies for many years
(blue stragglers, yellow giants, sub-subgiants, W UMa)
Stellar products are numerous and form a key subpopulation of evolved stars!!
(blue stragglers, yellow giants, sub-subgiants, W UMa)
My work focuses on this 25% of stars in order to build a more comprehensive picture of stellar evolution
(blue stragglers, yellow giants, sub-subgiants, W UMa)
Use synergy of observations and theoretical models to determine the formation
Once we know how they formed, we can model future evolution Add new insights into stellar population models
Ferraro et al. 1999
Globular Clusters
Hurley et al. 2001
Open Clusters
M67 Momany 2014
Dwarf Galaxies
Stellar color Stellar color Stellar color Magnitude Magnitude Magnitude
Add mass, but how?
Astronomy Magazine: Roen Kelly
Mass Transfer Collision
Astronomy Magazine: Roen Kelly
Mass Transfer Collision
Created by A. Geller, Northwestern University
Courtesy of Aaron Geller
triple system binary system
0.8 solar masses 0.7 solar masses
James Lombardi
Astronomy Magazine: Roen Kelly
Mass Transfer Collision
Main sequence companion
These stars have similar masses, but the slightly more massive one evolves faster and becomes a red giant Main sequence primary Red Giant primary (to approximate scale)
Red Giant primary White dwarf Blue straggler The red giant transfers its envelope to the companion, which gains mass (to approximate scale) The companion becomes a blue straggler, and the red giant leaves behind a white dwarf Main sequence companion
Blondin, Richards, & Malinowski
NASA
HST sensitive in the ultraviolet where white dwarf companions will be brighter than the blue straggler Awarded a total of 53 orbits,
Discovered white dwarf companions of blue stragglers (Gosnell et al. 2014) Majority of open cluster blue stragglers form through mass transfer (Gosnell et al. 2015)
2011, 2012, Gosnell et al. 2014, 2015) Digitized Sky Survey
NASA/ESA, A. Feild (STScI)
Red Giant Accreting Main Sequence companion Blue Straggler White Dwarf
1400 1600 1800 2000 24 22 20 18 1400 1600 1800 2000 Wavelength 24 22 20 18 STMAG
BS: 6,500 K BS: 6,000 K WD: 18,000 K WD: 12,000 K
140N 150N 165LP
less massive blue stragglers
far-ultraviolet excess (not possible in younger open clusters)
140 160 180 200 Wavelength (nm) log (Detected Flux)
1 2 3 4 24 23 22 21 20 19 1 2 3 4 F150N - F165LP 24 23 22 21 20 19 F150N
9 9 . 7 3 % 99.73% 99.73% 95.45% 95.45% 68%
Expected blue straggler emission
Gosnell et al. 2014, 2015
Bright Faint
Magnitude Stellar color
(warm) (hot)
1 2 3 4 24 23 22 21 20 19 1 2 3 4 F150N - F165LP 24 23 22 21 20 19 F150N
9 9 . 7 3 % 99.73% 99.73% 95.45% 95.45% 68%
11000 12750 14500 16250 18000 White Dwarf Temperature (K)
Expected blue straggler emission cool white dwarf hot white dwarf
Gosnell et al. 2014, 2015
Bright
Stellar color
Faint
Magnitude
(warm) (hot)
1 2 3 4 24 23 22 21 20 19 1 2 3 4 F150N - F165LP 24 23 22 21 20 19 F150N
9 9 . 7 3 % 99.73% 99.73% 95.45% 95.45% 68%
11000 12750 14500 16250 18000 White Dwarf Temperature (K)
cool white dwarf hot white dwarf Expected blue straggler emission
Gosnell et al. 2014, 2015
Bright
Magnitude Stellar color
Faint
(warm) (hot)
Gosnell et al. 2015
0.4 0.6 0.8 1.0 1.2 16 15 14 13 12 0.4 0.6 0.8 1.0 1.2 B - V 16 15 14 13 12 V
18,500 16,000 13,500 11,000 Temperature of WD companion (K)
1888 2679 4230 4348 4540 5350 5379
B – V V
Non-velocity variable Single-lined binaries Double-lined binaries
Stellar color Magnitude
Bright Faint
Gosnell et al. 2015
0.4 0.6 0.8 1.0 1.2 16 15 14 13 12 0.4 0.6 0.8 1.0 1.2 B - V 16 15 14 13 12 V
18,500 16,000 13,500 11,000 Temperature of WD companion (K)
1888 2679 4230 4348 4540 5350 5379
B – V V
Non-velocity variable Single-lined binaries Double-lined binaries
Stellar color Magnitude
Bright Faint
Each white dwarf will set the mass transfer timeline
Based on models by P . Bergeron
Time since WD formed (billions of years) 2 4 6 8 20,000 15,000 10,000 5,000 Temperature of WD (Kelvin)
Teff = 12,000 K time = 0.4 Gyr Teff = 8,000 K time = 2.5 Gyr Teff = 6,000 K time = 4.8 Gyr
White dwarfs cool over time, like coals after a fire goes out
Based on models by P . Bergeron
Time since WD formed (billions of years) 2 4 6 8 20,000 15,000 10,000 5,000 Temperature of WD (Kelvin)
Geocoronal lines from the glow of Earth’s atmosphere
Teff = 17,300 ± 200 K MWD = 0.52 ± 0.01 M⊙
HST spectrum of white dwarf companion
Gosnell et al. 2017 (in prep)
Time since WD formed (billions of years) 2 4 6 8 20,000 15,000 10,000 5,000 This white dwarf formed only 100 million years ago! ➔ mass transfer ended 100 Myr ago Temperature of WD (Kelvin)
Based on models by P . Bergeron
Mass of primary star: 1.2 M⊙ Mass of secondary star: 1.0 M⊙ Mass of WD: 0.5 M⊙ Mass of blue straggler: 1.3 M⊙ Amount of mass transferred: 0.3 M
⊙
Binary period: 1600 days Binary period: 1100 days
NASA/ESA, A. Feild (STScI)
We know starting and ending points, now we need to fix the mass transfer physics in the middle
NASA/ESA, A. Feild (STScI)
We know starting and ending points, now we need to fix the mass transfer physics in the middle, using MESA (Paxton et al. 2010) Mass of primary star: 1.2 M⊙ Mass of secondary star: 1.0 M⊙ Mass of WD: 0.52 M⊙ Mass of blue straggler: 1.3 M⊙ Amount of mass transferred: 0.3 M
⊙
Binary period: 1600 days Binary period: 1100 days
Use synergy of observations and theoretical models to determine the formation
Once we know how they formed, we can model future evolution Add new insights into stellar population models
25% of evolved stars follow alternative pathways in stellar evolution Current understanding of stellar evolution is incomplete, so we need observations to improve
Blue straggler stars provide the largest handle on this population of stellar products Constraints from white dwarf companions outline the formation history of blue stragglers and will improve stellar population models in the future