Cataclysmic Variables and Symbiotic
Stars – Challenging Targets for
Small Telescopes
Laurits Leedjärv
Tartu Observatory, Estonia
[email protected]
Observing Techniques, Instrumentation and Science
for Metre-Class Telescopes
September 23–26, 2013
Tatranská Lomnica
• Brief overview of CVs and SSs
• Some examples of light curves – what others hav
done
• Some examples of spectroscopic variations of SS
– own work
• What can be studied with small telescopes, what
not we know?
• Small optical telescopes are important, but …
Cataclysmic Variables (CV)
Close binary systems containing
an accreting white dwarf (WD) primary and
Roche-lobe-filling secondary (main sequence star
or brown dwarf)
Orbital periods of CVs mostly between ~70 minutes
and 7–8 hours, with a gap between 2–3 hours
Catalogue of Cataclysmic Binaries, Low-Mass X-Ray
Binaries and Related Objects Ritter & Kolb 2003,
A&A, 404, 301; update RKcat7.20, 1 July 2013
contains 1094 CVs, 104 LMXBs, and 483 related obj
Downes et al. 2001 (PASP, 113, 764), edition 2006 li
1600 CVs.
Recent sky surveys have revealed new CVs,
for example:
SDSS – about 290 CVs (Szkody et al. 2011, AJ, 142: 181 an
references therein;
http://www.astro.washington.edu/users/szkody/cvs/index.htm
CRTS (Catalina Real-Time Transient Survey) –
> 1000 CVs (including those discovered by SDSS)
(Drake et al. 2009, ApJ, 696, 780; http://crts.caltech.edu)
CVs are classified into different types according to
their variability and outburst characteristics:
Non-magnetic CVs
- classical novae
- recurrent novae (with a dwarf or giant
secondary)
- dwarf novae (U Gem, Z Cam, SU UMa, SS Cyg
type)
- nova-like CVs
VY Scl stars
AM CVn stars
SW Sex stars
Magnetic CVs
Symbiotic Stars (SS)
Interacting binary systems containing a white dwar
(usually accreting from stellar wind, sometimes via
and a red giant, in general not filling its Roche lobe
Both stars are embedded into gaseous nebula, part
ionized by the hot component.
≥230 symbiotic stars known
A Catalogue of Symbiotic Stars Belczyński et al. 20
A&ASS, 146, 407
Corradi et al. 2010, A&A, 509, A41
Miszalski et al. 2013, MNRAS, 432, 3186
Classification to S and D types
S (Stellar): normal M giant, orbital periods 200–200
(5700) days
D (Dusty): Mira type cool component, orbital period
in tens of years
Yellow (S – without dust, and D’ – dusty): F, G or K type
giant, orbital periods like in S-type
Carbon
Classification of SS based on the nature and variab
of the hot component:
Classical (Z And type) SS
- about 2–3 mag eruptions at irregular intervals (a few ye
Symbiotic novae
- one about 6–10 mag outburst recorded
Symbiotic recurrent novae
- repeating outbursts (~2–10 mag) at ~10–100 years inter
Quiescent SS
- no outburst related brightness variations
Some examples of CV light curves
Flickering of the peculiar VY Scl type CV MV Lyr
The eclipsing polar HU Aqr – CV with two planets!
Examples of SS light curves
The prototype Z And
AG Dra
The peculiar SS CH Cyg
The eclipsing SS AR Pav
The symbiotic nova V1016 Cyg
Parimucha et al. 2002, A&A, 391, 999
Some examples of monitoring symbiotic stars at
Tartu Observatory
1.5-metre telescope, Cassegrain spectrograph
CH Cyg – non-typical symbiotic star
Burmeister & Leedjärv 2009, A&A, 504, 171
Yellow symbiotic star AG Dra
Leedjärv et al. 2004, A&A, 415, 273; Leedjärv & Burmeister 2
Baltic Astr, 21, 131; Leedjärv et al. in preparation
Hβ and He II λ4686
AG Dra – relations between the U magnitude and strength of
the emission lines
Z And – discovery of bipolar jets from the optical spe
Skopal & Pribulla 2006, ATel, 930; Skopal, Pribulla, Budaj et al
2009, ApJ, 690, 1222; Burmeister & Leedjärv 2007, A&A, 461, L
Disappearance of high-excitati
emission lines during the
outburst of Z And in 2006
Astrophysical phenomena to be studied in CVs and
- Accretion disks (viscosity, angular momentum loss, disk
instability, …)
- Physics of boundary layer
- Accretion from stellar wind
- Role of magnetic fields (accretion streams, columns et
- Thermonuclear burning on WD surface (thermonucl
runaways, nova and recurrent nova outbursts, “flashes” of
symbiotic stars, …)
- Forming and accelerating bipolar jets
- Raman scattering on HI atoms
- Accretion induced collapse of WD → SN Ia
… … …
Different time scales involved:
Seconds to (tens of) minutes – flickering in CVs and
(only a few) SSs: accretion disk ↔ boundary layer
Tens of minutes to hours – orbital motion in CVs,
superhumps
Days to (tens of) years – recurrence of dwarf nova
outbursts, superoutbursts, magnetic phenomena in
magnetic CVs; spectral variations of SSs
Hundreds of days to years – orbital motion in S-typ
Years to decades – outbursts of classical SSs
Decades – recurrent nova outbursts; orbital motion
in D-type SSs
Hundreds to thousands of years (?) – symbiotic nov
outbursts
Thousands to tens of thousands of years – recurren
classical nova outbursts
The brightest SSs have V ~ 7 mag, CVs ~10 mag
Variability on “human” time scales
⇓
Ideal targets for metre-class telescopes,
for long-term monitoring as well as for case studie
(e.g. Doppler tomography, eclipse mapping)
Small telescopes can contribute into solving some
open questions related to CVs and SSs:
• Where are the “period bouncers” – CVs after reac
the period minimum at ~70 minutes, presumably
evolving back to longer periods?
• Interplay of magnetic braking and gravitational
radiation, causing the period gap?
• What is the physics of viscosity in accretion disks
• What causes the low states of polars as well as
novalike systems with orbital periods between
3 and 4 hours?
• What is the actual number density and distributi
of CVs in the Galaxy?
• What is the nature and mechanism of ~2 – 3 mag
outbursts of classical symbiotic stars?
• What is the role of RLOF and ellipsoidal variation
in the mass transfer mechanism of symbiotic sta
• Which symbiotic stars and under which condition
do emit collimated bipolar jets?
• Are symbiotic stars precursors of SN Ia?
• What is the total number of symbiotic stars in th
Galaxy?
Some examples of organizations and campaigns
contributing to CV and SS research with small telesc
AAVSO
American Association of Variable Star Observers
www.aavso.org
WET
www.wholeearthtelescope.org
VSNET
Variable Star Network
www.kusastro.kyoto-u.ac.jp/vsnet (in hibernation?)
ANS Collaboration
ANS Collaboration
Asiago Novae and Symbiotic Stars Collaboration
www.ans-collaboration.org
Novae(?)
Accretion disk
Red giant in SSs
H burning WD
MS star or brownGaseous envelope
Boundary layer
of SSs
Hot spot and accretion columns dwarf in CVs
Radio jets in SSs
Colliding winds in SSs
and CVs
Summary
Cataclysmic Variables and Symbiotic Stars deserve
continuous monitoring.
Telescopes of 1–2 metre size with proper
instrumentation are big enough for many purposes
However, nature and behaviour of CVs and SSs can
fully understood only if information across the who
electromagnetic spectrum is taken into account.
Thank you for attention!