Variability of Accreting White Dwarf Binaries and Other Compact Objects
Manuel Pichardo Marcano (Texas Tech University)
Advisors: Liliana Rivera Sandoval & Thomas J. Maccarone
White Dwarfs
Mass ~ 1 M☉
Radius ~ 1 R🜨
Radius ~ 1 R🜨
ESA/NASA
Compact Objects
Mass ~ 1 M☉
Radius ~ 1 R🜨
Mass ~ 1 M☉
Radius ~ 10 Km
White Dwarf
Neutron Star
ESA/NASA
Life Cycles of Stars
-
White Dwarfs:
-
The fate of most stars
-
Stars < 8 M☉
-
-
Lower Left HR diagram
- Blue and Faint
ESO
Accreting White Dwarf Binaries
Cataclysmic Variables
AM CVn
- Main Sequence Star
- Porb ~ 80 min - 10 hours
- Outbursts:
- 2-20 days
- Disk instability model+ (DIM)
- >1000 in the galactic field
- Predicted large # in old Star Clusters
- White Dwarf/Helium Star
- Porb ~ 5 - 70 min
- Outburts:
- weeks?
- DIM?
- ~70 in the galactic field
Mark A. Garlick
Caltech
Accreting WD Binaries Surveys
1- SCOVaS: Survey for Compact Objects and Variables
Pichardo Marcano et al. (2021a)
Pichardo Marcano et al. (in prep.)
2- TACOS: TESS AM CVn Outbursts Survey
Pichardo Marcano et al. (2021b)
Cataclysmic Variables
R. Hynes
X-ray
Looking of CVs in GCs
NASA, ESA, H. Richer and J. Heyl (University of British Columbia), and J. Anderson and J. Kalirai (STScI)
Finding CVs in GCs
HST Optical (3' x 2')
NASA, T. Brown and S. Casertano (STScI)
HST NUV (2.7' x 2.7')
Dieball et. al (2016)
Chandra (3.65 ' x 3.65')
NASA/CXC
1. X-rays and 2. (F)UV excess
Color-Magnitude Diagram
Lugger et. al (2017)
-
CMDs:
- Identify blue objects
- Hα excess
-
Variability:
- Flickering
- Ellipsoidal modulations
- Outbursts
Hα Excess
NGC 6752
Hα deficiency
Bright CVs
Faint CVs
Finding CVs in X-rays
-
Advantage of X-ray Searches:
- Avoid crowding
-
Disadvantage:
- Lx ≥ 1029 ergs/s
Significant X-ray bias
X-ray: NASA/CXC/CfA/J.Grindlay & C.Heinke; Optical: ESO/Danish 1.54-m/W.Keel et al.
What do we know from theory and simulations?
- Most Lx < 1029 ergs/s
- > 90% are period bouncers
- Old systems
- Dearth of dwarf novae:
- Low Accretors -> Rare Outburts
- Population beyond half-light radius
Simulation results
Belloni et al. (2016, 2017a, 2017b)
Simulation results
Predicted "Hidden" CV Population
Summary CVs in GCs
-
Few of CVs per cluster
-
~ 100s predicted
-
-
X-ray biased sample:
-
Lx > 1029ergs/s
-
-
Period distribution?
-
16 known periods
-
We need more detections, classification and periods
All Magnetics ?
- HST Archive
- 7 Globular Clusters
- Many Exposures
- Different properties
- Metallicity
- Core-collapsed
- Non core-collapsed
SCOVaS: Survey for Compact Objects and Variables
SCOVaS: Survey for Studying Compact Objects and Variables
- Focus: Cataclysmic Variables (CVs) with HST
- First Survey for CVs in GCs Unbiased in the X-ray
- X-ray faint CVs
- Orbital Periods
- Spatial Distribution:
- Looking at the dense Core of Clusters
- Next: Search in the Outskirts
- Optical Counterpart X-ray/Radio Sources in GCs
Preliminary Results
NGC 6397
- Closest Core Collapse
- Second Closest
- 2.4 kpc
- 15 CV candidates
- 2 Pulsars
Preliminary Results
NGC 6397
- WFPC-2
- March-April 2005:
- 126 orbits
- F814W, F606W and F336W
- Exp time: 500-700 s
Preliminary Results
NGC 6397
- WFPC-2
- March-April 2005:
- 126 orbits
- F814W, F606W and F336W
- Exp time: 500-700 s
Redback Pulsar
A new candidate Redback Pulsar
HUGS catalogue. (Piotto et al. 2015, Nardiello et al. 2018)
Pichardo Marcano et al. (2021a)
X-ray
HST F336W
Radio
Zhao et al.(2020)
Zhao et al. , including Pichardo Marcano (2020)
A new candidate Redback MSP
Pichardo Marcano et. al (2021a)
- Porb 1.96 days
- Longest Porb for Redback in GCs
- Missed MSP in Pulsar Searchers
Blue Variables
- Periodicity Search:
- Lomb-Scargle
- Phase Dispersion Minimization
- False Alarm Probability < 10-8
Light Curves of Known CV Candidates
High and Low state?
Nova-like Candidate
Pichardo Marcano et. al (in prep)
U19
U21
Nova-like Candidate
First Magnetic He WD Candidate
Pichardo Marcano et. al (in prep)
Hα Excess
Hα deficiency
Magnetic He WD
- Vrad > 100 km/s (MUSE)
- Not Detected in X-rays
- Rotation Period
-
18.4 hours
-
Pichardo Marcano et. al (in prep)
Pre-Cataclysmic Variable
Pichardo Marcano et. al (in prep)
Hα Excess
Hα deficiency
Detached White Dwarf-Red Dwarf
- Not Detected in X-rays
- Potential Porb
-
5.21 hours
-
Pichardo Marcano et. al (in prep)
Detached White Dwarf-Red Dwarf
NGC 6397
- Pipeline to find interesting objects:
- CMD Position and Periodicity/Variability Searches
- We were able to recover all known CV Candidates
- Found Orbital Period Redback Pulsar
- Detached White Dwarf-Red Dwarf
- First Magnetic He Core WD in GCs
- Many more variables to analyze...
Where are all the CVs?
Compact Binaries Surveys
1- SCOVaS: Survey for Compact Objects and Variables
Pichardo Marcano et al. (2021a)
Pichardo Marcano et al. (in prep.)
2- TACOS: TESS AM CVn Outbursts Survey
Pichardo Marcano et al. (2021b)
Compact Binaries Surveys
AM Canum Venaticorum AM CVn
-
White dwarf + White dwarf
-
White dwarf + He Star
-
Orbital Period: 5-70 minutes
Caltech
Caltech
-
Porb 20 to ~ 60 minutes (?)
-
Superoutburts (SO) and "Normal" outbursts (NO)
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SO: Superhumps (periodic brightness variation )
-
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Disk instability model (DIM)
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Constant Mass transfer rate
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Tidal-thermal disk instability model
-
Outbursting Systems
Empirical Relationships
- Trec ∝ Porb7.35
- Tdur ∝ Porb4.54
- Δ mag ∝ Porb
- Ground-Based:
- PTF/CRTS
- ZTF
- LINEAR
Levitan et al. 2015
See also Duffy et al. 2021
Empirical Relationships
- Trec ∝ Porb7.35
- Tdur ∝ Porb4.54
- Δ mag ∝ Porb
- Ground-Based:
- PTF/CRTS
- ZTF
- LINEAR
Levitan et al. 2015
See also Duffy et al. 2021
Better LC → Better Constraints
Transiting Exoplanet Survey Satellite (TESS)
Outbursts
Pichardo Marcano et al. (2021)
-
Precursor
- TESS (Duffy et al. 2021)
- Echo Outbursts
- DIM with Enhanced Mass Transfer (e.g. Hameury & Lasota 2021)
TESS AM CVn Outbursts Survey
Pichardo Marcano et al. (2021)
ZTF
TESS
Long-term monitoring
Pichardo Marcano et al. (2021)
- Orbital Periods:
- 2-minute cadence
- Limits on Recurrence Time
- "Normal Outburts"
Superoutburst duration vs Porb
Pichardo Marcano et al. (2021)
TACOS Summary
-
Precursors and "Normal" Outbursts:
- Relatively Common
- Short Duration (missed by ground-based)
-
Echo Outbursts:
- Different morphology
- Enhanced Mass Transfer
- Superoutburst durations overestimated
- Two new candidate orbital periods
- Color Evolution
Other work with Accreting WDs
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Follow-up eROSITA transient:
- TESS time series analysis
-
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Atel: Pichardo Marcano (2020)
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Paper: Schwope, [...], Pichardo Marcano, et al. (2021)
-
Caltech
M 92
- Non-Core Collapse
- Very Metal-Poor
- 8.4 kpc
- 4-5 CV candidates
- 1 Pulsar
Preliminary Results
M 92
- WFPC-2
- 2008-01-25 to 2008-01-30:
- 76 Exposures
- F555W
- Exp time: 10 s
New Variables in the Core
HST vs Ground-based
Yepez et al. (2020)
Ground-based Data
HST Data
New Variables in the Core
SX Phe
- Good Distance indicator:
- Strong P-L relation
- Less common than RR Lyrae
-
Blue Straggler
- Product of Binary evolution
P = 1.38 hr
Pichardo Marcano et. al (in prep)
Future Work
NGC 6397
M 92
Spectroscopy (MUSE)
AO Gemini IR
Blue Straggler
Subramaniam et. al (2020) (Image credits: Snehalata Sahu)
New Variables in the Core
- Pulsating Stars:
- RR Lyrae
- SX Phe
- Active Binaries
- Transients?
- Dwarf Novae?
Extra
Formation of CVs
Ivanova et. al (2012)
- Main sequence binary
- Roche lobe overflow
- Common Envelope
- Detached binary
- Cataclysmic Variable
Evolution of the CV
- Magnetic Braking
- Porb > 3 hr
- Period Gap
- Fully convective donor
- Gravitational Wave Rad
- Porb < 2 hr
- Period Minimum
- Brown dwarf
- Period Bouncers
- Increase Porb
Abril et. al (2019)
CV Population in the field
Pala et. al (2019)
- Dwarf Novae (59 %):
- Transients/Outbursts:
- U Gem
- SU UMa
- WZ Sge
- Transients/Outbursts:
- Novalike:
- Persistently Bright
- Most Lx < 1029 ergs/s
- ~100 L☉ of the Sun
- > 90% are period bouncers
- Old systems
- Dearth of dwarf novae:
- Low Accretors -> Rare Outburts
- Population beyond half-light radius
Simulation results
Belloni et al. (2016, 2017a, 2017b)
Simulation results
Predicted "Hidden" CV Population
Evolution of the CV
- Magnetic Braking
- Porb > 3 hr
- Period Gap
- Fully convective donor
- Gravitational Wave Rad
- Porb < 2 hr
- Period Minimum
- Brown dwarf
- Period Bouncers
- Increase Porb
Knigge (2006)
PTF1 J0719+4858:
-
Similar to Dwarf Novae:
- Hameury et al. (2020)
- Rivera Sandoval et al. (2021)
Color Evolution
Pichardo Marcano et al. (2021)
Ramsay Gaia
CVs in GCs
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Few of CVs per cluster
-
X-ray biased sample:
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Lx > 1029ergs/s
-
-
Dearth of DNe:
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Only 17 confirmed
-
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Core-collapsed:
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Bimodal population
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Non core-collapsed:
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1 faint population
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Period distribution?
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16 know periods
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| GC | # CV candidates |
|---|---|
| 47 Tuc | 43 |
| Omega Cen | 27 |
| NGC 6397 (CC) | 15 |
| NGC 6752 (CC) | 16 |
| ... | ... |
Need more detections. Need more Periods
Cataclysmic Variable
- Magnetic and No
Magnitude
JD - 2458636
Szkody et. al (2020)
Mroz et. al (2016) Image: (J. Skowron, K. Ulaczyk / Warsaw University Observatory)
- Dearth of dwarf novae:
- Small duty cycle (< 6%)
- > 90% are period bouncers
- Old systems
- Most Lx < 1029 ergs/s
- Bright CVs dynamically formed
- Population beyond half-light radius
Simulation results
Belloni et. al (2019)
AM CVns
- Helium Rich and Know to go into outburts
Kupfer et. al (2013)
Duffy et. al (2021)
A new candidate Redback MSP
-
Porb of 1.96 day
Zhao et. al (2020)
- Chandra X-ray
- MAVERIC Survey
Chandra and Radio follow-up
Zhao et. al (2020)
Unbiased X-ray search
7 Globular Clusters in the core and outskirts