AM Canum Venaticorum AM CVn

• White dwarf + White dwarf

• White dwarf + He Star

• Orbital Period: 5-70 minutes

• Rare: 70 Galactic field

AM CVns

•  Helium Rich and (some) known to go into outbursts

Disk AM CVns

High state (high Ṁ)

• Hot ionized disk

~20

~10

~40-60 (?)

Low state (low Ṁ)

• Cold stable disk

Caltech

• Porb 20 to ~ 60 minutes (?)

• Superoutburts (SO) and "Normal" outbursts (NO)

• Disk instability model (DIM)

  •  Constant Mass transfer rate

  • Tidal-thermal disk instability model

    • SO: Superhumps (periodic brightness variation )

Outbursting Systems

Caltech

• Porb 20 to ~ 60 minutes (?)

• Superoutburts (SO) and "Normal" outbursts (NO)

• Disk instability model (DIM)

  •  Constant Mass transfer rate

  • Tidal-thermal disk instability model

    • SO: Superhumps (periodic brightness variation )

Outbursting Systems

Place Constraints

Caltech

• Porb 20 to ~ 60 minutes (?)

• Superoutburts (SO) and "Normal" outbursts (NO)

• Disk instability model (DIM)

  •  Constant Mass transfer rate

  • Tidal-thermal disk instability model

    • SO: Superhumps (periodic brightness variation )

Outbursting Systems

Better LC → Better Constraints

Place Constraints

Empirical Relationships

1. T_rec ∝ P_orb^7.35
2. T_dur ∝ P_orb^4.54
3. Δ mag ∝ P_orb
4. Ground-Based:
   1. PTF/CRTS
   2. ZTF
   3. LINEAR

Levitan et al. 2015

See also Duffy et al. 2021

Empirical Relationships

1. T_rec ∝ P_orb^7.35
2. T_dur ∝ P_orb^4.54
3. Δ mag ∝ P_orb
4. Ground-Based:
   1. PTF/CRTS
   2. ZTF
   3. LINEAR

Levitan et al. 2015

See also Duffy et al. 2021

Need detailed short-term variability

Empirical Relationships

1. T_rec ∝ P_orb^7.35
2. T_dur ∝ P_orb^4.54
3. Δ mag ∝ P_orb
4. Ground-Based:
   1. PTF/CRTS
   2. ZTF
   3. 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)

Type of Super Outbursts

Osaki et al. (2005)

High Mass Ratio

DIM

Cataclysmic Variables

• Evolution Superhump

Pichardo Marcano et al. (2021)

ASASSN-14cc

Pichardo Marcano et al. (2021)

9–18 d

kato et al. (2015)

• 2 Super Outbursts:
  • No precursor
  • Variable in length
    • Compare Kato+'15 and Duffy+'21
• Superhump period
  • 10 minute cadence

• Precursor
  • TESS (Duffy et al. 2021)
• Echo Outbursts
• DIM with Enhanced Mass Transfer  (e.g. Hameury & Lasota 2021)

PTF1 J0719+4858

Pichardo Marcano et al. (2021)

ZTF

TESS

Color Evolution

PTF1 J0719+4858

SS Cyg

Cataclysmic Variable

• Similar to Dwarf Novae

  • Hameury et al. (2020)

• Similar SDSS J1411+4812
  • Rivera Sandoval et al. (2021)
• Compare to SDSS 1137/SDSS 0807
  • Rivera Sandoval et al. (2021)

Pichardo Marcano et al. (2021)

Color Evolution

PTF1 J0719+4858

SDSS J113732+405458

 Enhanced mass transfer

• Similar to Dwarf Novae

  • Hameury et al. (2020)

• Similar SDSS J1411+4812
  • Rivera Sandoval et al. (2021)
• Compare to SDSS 1137/SDSS 0807
  • Rivera Sandoval et al. (2021)

Pichardo Marcano et al. (2021)

Rivera Sandoval et al. (2021)

• Precursor
  • TESS (Duffy et al. 2021)
• Echo Outbursts
• DIM with Enhanced Mass Transfer  (e.g. Hameury & Lasota 2021)

SDSS J1043+5632

Pichardo Marcano et al. (2021)

ZTF

TESS

Type of Echo Outbursts

SDSS J1043+5632

• WZ Sge like ?
  • Precursors
  • EMT (Hameury+'20)
  • Massive WD?

• Compare to TCP J21040470+4631129
  • EMT (Hameury+'20)
• Helium "SU UMa"
  • EMT+TTI (Kotko+'12)

SDSSJ1043+5632

• Similar to Dwarf Novae:
  • Hameury et al. (2020)
  • Rivera Sandoval et al. (2021)

Color Evolution

Pichardo Marcano et al. (2021)

Long-term monitoring

Pichardo Marcano et al. (2021)

• Orbital Periods:
  • 2-minute cadence
• Limits on Recurrence Time
• "Normal Outburts"

Normal Outburts

PTF1 J2219+3135

V803 Cen

• V803 Cen
  • "Cycle"
  • Low Ṁ?
• Timing Normal Outbursts:
  • Permanent Superhumper?

Superoutburst duration vs P_orb

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

• Follow-up eROSITA transient:

• TESS time series analysis

• • Atel: Pichardo Marcano (2020)

  • Paper: Schwope, [...], Pichardo Marcano, et al. (2021)

Caltech

PTF1 J0719+4858:

• Similar to Dwarf Novae:
  • Hameury et al. (2020)
  • Rivera Sandoval et al. (2021)

Color Evolution

Pichardo Marcano et al. (2021)

Normal Outbursts

V803 Cen

• WZ Sge like ?
  • Precursors
  • EMT (Hameury+'20)
  • Massive WD?

• Compare to TCP J21040470+4631129
  • EMT (Hameury+'20)
• Helium "SU UMa"
  • EMT+TTI (Kotko+'12)