Cataclysmic Variables in the AAVSO Observing Program

Janet A. MatteiKerriann H. Malatesta

AAVSO

Second HEA WorkshopJuly 4-5, 2002, Waikoloa Beach, Hawaii

Cataclysmic VariablesCataclysmic Variables

• Compact close binary systems

• Red dwarf-type (Sun-like) star – secondary-and a white dwarf -primary

• Due to evolution, the red star is losing matter to the white dwarf star via an accretion diskArtwork by K. Smale

The Many Faces of The Many Faces of Cataclysmic VariablesCataclysmic Variables

Other Types of Variables

82%

Cataclysmic Variables

18%

Cataclysmic Variables in the Cataclysmic Variables in the AAVSO Observing ProgramAAVSO Observing Program

Dwarf NovaeDwarf Novae

• Also known as U Geminorum stars, named for the first dwarf nova

• Close binary system• Changes in magnitude

result of processes in the disk

• Several subtypes: SS Cygni, SU Ursae Majoris, and Z Camelopardalis

Artwork by M. Garlick

SS Cygni StarsSS Cygni Stars

• Vary by 2-6 magnitudes, lasting 1-2 weeks

• Outbursts on a timescale of 10-1000 days

• Rise to maximum is fast generally <1 day

• Decline is longer, typically 2-15 days

Photographs of SS Cygni by AAVSO Chartmaker Charles Scovil

SS Cygni Long-Term Light CurveSS Cygni Long-Term Light Curve

and a closer look at SS Cyg

Wide Outburst

Narrow Outburst

SU Ursae Majoris StarsSU Ursae Majoris Stars

• Narrow outbursts of about 1-2 days

• Brighter superoutbursts of an additional 2 magnitudes lasting about 10-20 days

• Superhumps seen during superoutbursts

• Subtype:WZ Sagittae

Artwork by M. Garlick

SU UMa and SuperoutburstsSU UMa and Superoutbursts

Superoutbursts

SU UMa Subtype: WZ Sge

WZ Sge is an SU UMa star with an extremely long supercycle

An Example of SuperhumpsAn Example of Superhumps

Superhump activity of the 2001 outburst, as recorded by AAVSO observer Lew Cook (COO)

Past Outbursts of WZ SgePast Outbursts of WZ Sge

Z Camelopardalis StarsZ Camelopardalis Stars

• Similar to the SS Cygni stars, but cyclic variations interrupted by intervals of constant brightness, known as standstills

• Standstills occur approximately one-third of the way from maximum to minimum

Artwork by M. Garlick

Z Camelopardalis Long-Term Z Camelopardalis Long-Term Light CurveLight Curve

Standstill

Standstill

Z Cam and StandstillsZ Cam and Standstills

Standstill

NovaeNovae• Undergo one large

outburst due to thermo-nuclear runaway

• Amplitude may change by 8-15 magnitudes

• Rise-time to maximum and decline to minimum vary

• Subtypes: fast nova (Na), slow nova (Nb), and very slow nova (Nc)

WIYN Telescope image of the nova GK Per

Nova Light CurvesNova Light Curves

GK Persei Long-Term Light CurveGK Persei Long-Term Light Curve

Nova Outburst

Dwarf Nova-Type Outbursts

Recurrent NovaeRecurrent Novae

• Photometric and spectroscopically similar to novae

• Rapid rise to maximum• Brighten by 4-9

magnitudes• Decline faster than that

of novae• Recur every 10-100

years

HST image of the recurrent nova T Pyxidis

RS Ophiuchi Long-Term Light CurveRS Ophiuchi Long-Term Light Curve

Recurrent Nova Outburst

Nova-likeNova-like

• Similar to novae in terms of light changes and spectral features

• Subtypes: V Sagittae, UX Ursae Majoris, and VY Sculptoris

WIYN Telescope image of the nova-like variable BZ Cam

Polars (AM Her stars)Polars (AM Her stars)• White dwarf star has

magnetic field of 10-100 mega Gauss

• Accretion columns, instead of an accretion disk

• Synchronous rotation (Pspin = Porb)

• Source of hard X-ray, extreme UV, UV, as well as optical wavelengths

Artwork by R. Kightley

Anatomy of a PolarAnatomy of a Polar

Image from HEASARC

Light Curve of AM HerculisLight Curve of AM Herculis

Intermediate Polars (DQ Her Intermediate Polars (DQ Her stars)stars)

• White dwarf has magnetic field of 1-10 mega Gauss

• Accretion disk yields to accretion column near white dwarf

• Rotation not synchronous

• Source of hard X-ray, UV, as well as optical wavelengths

Artwork by R. Kightley

AAVSO Variable Star ChartsAAVSO Variable Star Charts

Old favorites

New additions

Cataclysmic Variables in the Cataclysmic Variables in the AAVSO Observing ProgramAAVSO Observing Program

0

50

100

150

200

250

Type

Novae

UG

UGSS

Nova-like

CV

UZ

UGSU

Polars

Recurrent Novae

When Good Stars MisbehaveWhen Good Stars Misbehave

SU UMa takes a superoutburst

hiatus

U Gem has a double-wide

outburst

SS Aur lacks

amplitude

Alert Notice 292

THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS 25 Birch Street, Cambridge, MA 02138 USA

INTERNET: aavso@aavso.org Tel. 617-354-0484 Fax 617-354-0665

AAVSO ALERT NOTICE 292 (January 10, 2002)

0659-03 PECULIAR VARIABLE IN MONOCEROS (VAR MON 02)

We have been informed by the Central Bureau for Astronomical Telegrams (IAU Circular 7785) that Nicholas J. Brown, Quinns Rocks, W. Australia, has photographically discovered a possible nova in Monoceros on January 6.6 UT at about magnitude 10 on a T-Max 400 film. He confirmed it visually on January 7.6 UT at magnitude 10.0. Confirming observations reported via the AAVSO were: Jan. 8.094 UT, 10.1 CCDV, Charles Scovil, Stamford, CT; 9.513, 9.3 CCD, Peter Nelson, Ellinbank, Victoria, Australia; 9.815, 9.5 CCD, Arto Oksanen and Juha Solonen, Nyrola Observatory, Finland. Brown reported that nothing was visible at the location of the object down to magnitude 12 on a photograph taken 2001 December 22.

More at: http://www.aavso.org/alerts/alert292/alert292text.stm

Light Curve of V838 MonLight Curve of V838 Mon

V838 Mon’s Light EchoV838 Mon’s Light Echo

Image combining HST/ACS images by AAVSO observer and professional astronomer Peter Garnavich

37% of the requests for variable star data in 2000/2001 were for dwarf novae, novae, and nova-like stars

EB & RR Lyr1%

Semiregular2%

Novae & Nova-like9%

Dwarf Novae28%

Mira49%

RV Tau2%

Misc.4%

R CrB2%

X-Ray3%

2000/2001 AAVSO Data Requests2000/2001 AAVSO Data Requests

2000/2001 AAVSO Data Requests2000/2001 AAVSO Data Requests

Elem. - Undergrad. Students

10%

Educators2%

Amateur Astronomers

13%

Professional Astronomers

68%

Graduate Students

6%Press1%

Professional astronomers most commonly request AAVSO data

IUE

Kitt Peak

HST

Cerro Tololo

Chandra

Amateur Astronomers Contributed Data for the Amateur Astronomers Contributed Data for the Following SatellitesFollowing Satellites

(satellites in chronological order)

Apollo-Soyuz * Extreme UV

ANS * X-ray

Ariel V * X-ray

HEAO-1/2 * X-ray

IRAS * IR

IUE * UV

Voyager * Far UV

ASTRO-1 * UV

ASTRO-2 * UV

EXOSAT * X-ray

ROSAT * X-ray

HST * Multiwavelength

Hipparcos * Astrometry

ISO * IR

GINGA * X-ray

EUVE * Extreme UV

ORFEUS * UV

BeppoSAX * X-ray

ASCA * X-ray

CGRO * Gamma ray

RXTE * X-ray

FUSE * Far UV

Chandra * X-ray

XMM-Newton * X-ray

Seeing CVs in a Different LightSeeing CVs in a Different Light

EXOSAT Light

Curve of U Gem

EXOSAT Light

Curve of AM Her

ASCA Light

Curve of AO Psc

EXOSAT Light

Curve of QQ Vul

Amateur and Professional Astronomers Team Up for Chandra Observations of SS Cygni

September 14, 2000 - Triggered by alerts from amateur astronomers worldwide NASA's Chandra X-Ray Observatory is observing the outburst of the brightest northern dwarf nova SS Cygni. The amateur stargazers provided Chandra scientists with a crucial early-warning of this outburst by calling-in their visual observations of SS Cygni as soon as they saw the star brightening. With the cooperation of hundreds of amateur astronomers, the Chandra observatory is monitoring SS Cygni's X-ray emission during its maximum brightness. Chandra X-ray Observatory

The amateur's observations of this star are done with backyard optical telescopes. The data they provide about the star's optical brightening, combined with the X-ray spectra gathered by the Chandra satellite, will reveal the nature of the flow of gas from a small red star onto its shrunken, dying companion.

Dr. Janet A. Mattei, Director of the American Association of Variable Star Observers (AAVSO)--a non-profit organization made up of mostly amateur astronomers -- and her technical staff are coordinating the collection of optical observations of SS Cygni and communicating them to Dr. Chistopher Mauche at Lawrence Livermore National Observatory, CA who is the Principal Investigator of Chandra observations.

More at: http://chandra.harvard.edu/chronicle/0300/aavso.html

Sometimes the little things in life count the most, especially when it comes to backyard stargazers making major contributions to the field of professional astronomy.

Dr. Janet A. Mattei, director of the American Association of Variable Star Observers (AAVSO), discusses some of the unique partnerships formed in the area of variable stars (stars that change in brightness) between professional and amateur astronomers at the American Astronomical Society meeting today in Rochester, N.Y.

Press Release

Calling All Amateur Stargazers: NASA Needs You

THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS25 Birch Street, Cambridge, MA 02138 USA

Tel. 617-354-0484     Fax 617-354-0665http://www.aavso.org

Contact:Janet A. MatteiAAVSO(617) 354 0484jmattei@aavso.org

PRESS RELEASE:Monday, June 5, 10:00 a.m

More at: http://www.aavso.org/meetings/press1.stm

RXTEGOF RXTE Observes Dwarf Nova Outbursts RXTEFAQ

In October 1996 the brightest dwarf nova in the sky - SS Cygni - went into outburst, and was observed for the next twelve days by RXTE (P.I. Peter Wheatley), EUVE (P.I. Chris Mauche), and the American Association of Variable Star Observers (AAVSO) (headed by Janet Mattei). The three light curves are shown in Figure 1. SS Cygni has historically been considered by the AAVSO to be their highest priority object because of its interesting behavior and brightness. It has been observed for over 100 years, and recently has often been the target of coordinated campaigns employing several satellites. SS Cyg has an orbital period of 6.6 hrs and goes into outburst about once every 50 days, during which time its optical flux increases by ~3.5 magnitudes. The durations of the outbursts in SS Cyg show a bimodal distribution: they last either ~7 days or ~14 days, and usually these alternate. (The Oct 1996 outburst was a short one.)

More at: http://heasarc.gsfc.nasa.gov/docs/xte/Greatest_Hits/wheatley.html

SS Cyg and U GemSS Cyg and U Gemin Three Wavelengthsin Three Wavelengths

The light curve in three wavelengths of an SS Cyg (right) and U Gem (left) outburst.

More at: http://heasarc.gsfc.nasa.gov/docs/xte/Greatest_Hits/wheatley.html

EUVE ObservationsEUVE Observations

Mauche, C.W., Mattei, J.A., & Bateson, F. 2001, in Evolution of Binary and Multiple Star Systems

VW Hyi: Normal OutburstVW Hyi: Normal Outburst

Mauche, C.W., Mattei, J.A., & Bateson, F. 2001, in Evolution of Binary and Multiple Star Systems

In VW Hyi, the optical-EUV delay is about 0.75 day; the optical-Voyager FUV delay (triangles) is about 0.5 day.

VW Hyi: SuperoutburstsVW Hyi: Superoutbursts

There is a dramatic decline in the EUV flux of VW Hyi just before the optical flux returns to quiescent value (left). The subsequent

rebound of the EUV flux coincides with the return of hard “thermal brems” component of the boundary layer spectrum (right).

Mauche, C.W., Mattei, J.A., & Bateson, F. 2001, in Evolution of Binary and Multiple Star Systems

OY Car: SuperoutburstsOY Car: Superoutbursts

The optical and EUV light curves of OY Car in superoutburst suggest that we are seeing in the EUV the decay of a normal outburst and the subsequent

rise of a long outburst which “add” to produce the superoutbust.

Mauche, C.W., Mattei, J.A., & Bateson, F. 2001, in Evolution of Binary and Multiple Star Systems

U Gem’s Anomalous OutburstU Gem’s Anomalous Outburst

Frequency histogram distribution of all outburst

durations in U Gem, compiled from the long-

term AAVSO light curve.The two straight lines with slopes of

26 d mag-1 and 1.4 d mag-1, respectively.Cannizzo, J.K., Gehrels, N., & Mattei, J.A. 2002, ApJ, submitted

U Gem’s Anomalous OutburstU Gem’s Anomalous Outburst

The apparent visual

magnitude

The disk mass

The rate of accretion onto

the WD

Cannizzo, J.K., Gehrels, N., & Mattei, J.A. 2002, ApJ, submitted

Amateur astronomers worldwide have helped:

• In discovering novae

• To obtain the first detection of X-ray emission from members of each CV category

• To obtain the first detection of soft X-ray pulsations from dwarf novae

• To obtain the first multi-wavelength spectra of dwarf novae

• To obtain multi-color photometry and spectroscopy at all stages of outburst of CVs

Contributions of Amateur Astronomers Contributions of Amateur Astronomers to Cataclysmic Variable Researchto Cataclysmic Variable Research

• In the discovery that mass loss occurs in the form of winds during outburst in some CVs

• In the discovery of coherent and quasi-coherent oscillations during outbursts of dwarf novae

• In the discovery that there is a delay between optical, ultraviolet, far ultraviolet, and extreme ultraviolet brightening in some novae

• In the discovery that the EUV and soft X-ray fluxes rise and the hard X-ray flux falls during the rise to optical outburst

• In the discovery that EUV soft X-ray fluxes initially track the optical flux, but falls more quickly during the decline from outburst

• In the discovery that the hard X-ray flux remains suppressed throughout the outburst, but recovers suddenly at the end of the optical outburst

• In the discovery of radio emission from some dwarf novae

• In providing a continuous record of behavior of CVs so that both multi-wavelength observations and theory can be correlated with optical data

• In furthering our understanding of compact binaries in terms of accretion disks, the nature and origin of the outbursts, the nature of the white dwarf, and the nature of the secondary

• In the discovery that 70% of CVs emit X-rays without being phase dependent (information vital in testing theories for high energy emission in compact systems)

A special thanks to observers worldwide

for their many decades of

observations. We gratefully

acknowledge the NASA grants to the AAVSO that enabled the collaboration of

amateur and professional astronomers!