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Cataclysmic variables (CV's)  

Novae, dwarf novae and closely related objects that undergo outbursts that are typically capable of repetition. They are normally interacting binaries comprising a cool stars usually near the main sequence , which fills its Roche lobe and loses matter in the direction of a white dwarf companion, usually forming and accretion disk. Most CV's show outbursts, typically repeated, which may be due to the burning of hydrogen to helium in a thermonuclear runaway on the surface of the white dwarf (novae), or to the pulsed release, in the form of light and heat, of gravitational energy from material falling towards the white dwarf (dwarf novae).

AM Herculis stars (Type AM)

AM Her type variables; close binary systems consisting of a dK-dM type dwarf and of a compact object with strong magnetic field, characterized by variable linear and circular polarization of light. The total range of light variations may reach 4-5 mag V.

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Novae (Type N)

Novae. Close binary systems with orbital periods from 0.05 to 230 days. One of the components of these systems is a hot dwarf star that suddenly, during a time interval from one to several dozen or several hundred days, increases its brightness by 7-19 mag in V, then returns gradually to its former brightness over several months, years, or decades. Small changes at minimum light may be present. Cool components may be giants, subgiants, or dwarfs of K-M type. The spectra of novae near maximum light resemble A-F absorption spectra of luminous stars at first. Then broad emission lines (bands) of hydrogen, helium, and other elements with absorption components indicating the presence of a rapidly expanding envelope appear in the spectrum. As the light decreases, the composite spectrum begins to show forbidden lines characteristic of the spectra of gas nebulae excited by hot stars. At minimum light, the spectra of novae are generally continuous or resemble the spectra of Wolf-Rayet stars. Only spectra of the most massive systems show traces of cool components. Some novae reveal pulsations of hot components with periods of approximately 100 s and amplitudes of about 0.05 mag in V after an outburst. Some novae eventually turn out to be eclipsing systems. According to the features of their light variations, novae are subdivided into fast (NA), slow (NB), very slow (NC), and recurrent (NR) categories. 

NA 
Fast novae displaying rapid light increases and then, having achieved maximum light, fading by 3 mag in 100 or fewer days (GK Per); 

NB 
Slow novae that fade after maximum light by 3 mag in >= 150 days (RR Pic). Here the presence of the well-known "dip" in the light curves of novae similar to T Aur and DQ Her is not taken into account: The rate of fading is estimated on the basis of a smooth curve, its parts before and after the "dip" being a direct continuation of one another; 

NC 
Novae with a very slow development and remaining at maximum light for more than a decade, then fading very slowly. Before an outburst these objects may show long-period light changes with amplitudes of 1-2 mag in V (RR Tel); cool components of these systems are probably giants or supergiants, sometimes semiregular variables, and even Mira variables. Outburst amplitudes may reach 10 mag. High excitation emission spectra resemble those of planetary nebulae, Wolf-Rayet stars, and symbiotic variables. The possibility that these objects are planetary nebulae in the process of formation is not excluded; 

NL 
Novalike variables, which are insufficiently studied objects resembling novae by the characteristics of their light changes or by spectral features. This type includes, in addition to variables showing novalike outbursts, objects with no bursts ever observed; the spectra of novalike variables resemble those of old novae, and small light changes resemble those typical for old novae at minimum light. However, quite often a detailed investigation makes it possible to reclassify some representatives of this highly inhomogeneous group of objects into other types; 

NR 
Recurrent novae, which differ from typical novae by the fact that two or more outbursts (instead of a single one) separated by 10-80 years have been observed (T CrB).

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V2491 Cyg - nova

V2491 Cyg (Cygnus)  Nova 'V2491 Cyg' was discovered in Cygnus by  Koichi Nishiyama, Kurume, Fukuoka-ken, Japan, and Fujio Kabashima, Miyaki-cho, Saga-ken, Japan,  on unfiltered CCD images taken 2008-04-10.728 UT  at magnitude 7.7 (IAU Circular No. 8934) (AAVSO Special Notice #103) Image below (2008-04-14.98 UT) was taken 4.25 days above discovery. Estimated magnitude +8.5 (C)
Annotated CCD Image  20s exposure, 2x2 binning, C Filter  2008-04-14 23:30hUT (#281142)
Sequence of CCD images of V2491 Cyg taken at varying dates after discovery
4.25 days (mag +8.5)		Pre-Nova (DSS image)
3x20s exposure (average combine),  2x2 binning, C Filter  2008-04-14 23:48hUT (#281164-66)		DSS image Same field of view as image to left  [ image from  http://archive.stsci.edu/cgi-bin/dss_form ]
22.3 days (mag +10.8)		59.3 days (mag +14.0)
3 x 120s exposure (average combine),  2x2 binning, C Filter  2008-05-03 00:56hUT (#285129-31)		3 x 120s exposure (average combine),  2x2 binning, C Filter  2008-06-08 23:56hUT (#290054-56)
71.3 days (mag +14.4)		83.3 days (mag +14.8)
3 x 120s exposure (average combine),  2x2 binning, C Filter  2008-06-20 23:47hUT (#291042-44)		3 x 120s exposure (average combine),  2x2 binning, C Filter  2008-07-02 23:54hUT (#293040-42)
V2491 Cyg - Light Curves  showing decline from discovery (+7.7) down to final measurement (+14.8)
V2491 Cyg - Reference Stars
Annotated CCD Image  15s exposure, 2x2 binning, V Filter  2008-04-14 23:51hUT (#281171)
Identification of precursor star to V2491 Cyg Nova
V2491 Cyg  59.3 days after discovery		Pre-Nova (DSS image)
3 x 120s exposure (average combine),  2x2 binning, C Filter  2008-06-08 23:56hUT (#290054-56)		DSS image Same field of view as image to left  [ image from  http://archive.stsci.edu/cgi-bin/dss_form ]

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Supernovae (Type SN)

Supernovae (B Cas, CM Tau). Stars that increase, as a result of an outburst, their brightnesses by 20 mag and more, then fade slowly. The spectrum during an outburst is characterized by the presence of very broad emission bands, their widths being several times greater than those of the bright bands observed in the spectra of novae. The expansion velocities of SN envelopes are in the thousands of km/s. The structure of a star after outburst alters completely. An expanding emission nebula results and a (not always observable) pulsar remains at the position of the original star. According to the light curve shape and the spectral features, supernovae are subdivided into types I and II. 

SNI 
Type I supernovae. Absorption lines of Ca II, Si, etc., but no hydrogen lines are present in the spectra. The expanding envelope almost lacks hydrogen. During 20-30 days following maximum light, the brightness decreases by approximately 0.1 mag per day, then the rate of fading slows and reaches a constant value of 0.014/day; 

SNII 
Type II supernovae. Lines of hydrogen and other elements are apparent in their spectra. The expanding envelope consists mainly of H and He. Light curves show greater diversity than those of type I supernovae. Usually after 40-100 days since maximum light, the rate of fading is 0.1 mag per day.

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SN 2006x - Type 1a Supernova

SN 2006x in M100 (Ursa Major)   2006x was discovered 2006/02/04  by Shoji Suzuki; M. Migliardi (CROSS) (Rochester Supernova site | Discovery Image | Discovery Image 2 | Reference Image) Image below (2006-02-20.9708) was taken 16 days after discovery.  Estimated magnitude of 2006x  is  +13.7 (C filter).   This is possibly at around peak brightness, magnitude at discovery was +17 (C)
Annotated CCD Image 5 x 2 min exposure (average combine), 2x2 binning, C Filter  2006-02-20 23:17h UT (#115064-68)
		M100 Reference Image, 2004 Pre-SN 2006x CCD Image (200% size) 5 x 1 min exposure (average combine),  2x2 binning, C Filter  2004-03-29 01:02h UT (#64207-11)
		SN 2006x, 2006-02-20 16 days after discovery SN Est. Mag +13.7 (C Filter) CCD Image (200% size) 5 x 2 min exposure (average combine),  2x2 binning, C Filter  2006-02-20 23:17h UT (#115064-68)
		SN 2006x, 2006-04-23 78 days after discovery SN Est. Mag +15.7 (C Filter) CCD Image (200% size) 5 x 2 min exposure (average combine),  2x2 binning, C Filter  2006-04-23 22:26h UT (#116082-86)

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SN 2008ax - Type II Supernova

SN 2008ax in NGC 4490  (Canes Venatici) 2008ax (Type II) was discovered 2008/03/03.45 by LOSS; Koichi Itagaki Magnitude at discovery +16.1 (C) (Rochester Supernova site | LOSS Discovery Image  | Itagaki Discovery Image | Reference Image) Image below (2008-03-08.03) was taken 4.6 days after discovery. Estimated Magnitude +15.2 (C)
NGC 4490 before SN2008ax (Feb 2008)		NGC 4490 with SN 2008ax  (Mar 2008)
Annotated CCD Image 7 x 120s exposure (average combine),  2x2 binning, C Filter  2008-02-14 04:00 hUT (#263704-10		Annotated CCD Image 7 x 120s exposure (average combine),  2x2 binning, C Filter  2008-03-08 00:48 hUT (#273136-42)

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Dwarf Novae (Type DG)

Dwarf Nova, sometimes call U Geminorum stars,  but is a term also for used for types UGSS and UGSU only, and not UGZ. Close binary systems consisting of a dwarf or subgiant K-M star fillings its inner Roche lobe, and a white dwarf surrounded by an accretion disk. Orbital periods range from 0.05 - 0.5 days. From time to time the brightness of the system increases rapidly by several magnitudes, and after days or weeks it returns to its original state.  The pauses between two consecutive outbursts for a given star may vary over a wide range , but every star is characterised by a certain mean value of the cycle length.  Longer cycles tend to be followed by outbursts of greater amplitude.  Some systems are eclipsing and the primary minimum appears to be due to the eclipse of a hot spot on the accretion disk, where matter falls in a gaseous stream from the donor star.

U Gem variables may be subdivided into three types:

SS Cyg (Type UGSS)
SU UMa (Type UGSU)
Z Cam (Type UGZ)

SS Cygni stars (Type UGSS)

Dwarf Nova in which visual brightness increases by 2 - 6 mag in 1 - 2 days, and the star returns to its original brightness over several days. Cycle lengths range from 10 to several thousand days.  Examples SS Cyg, U Gem.

SS Cyg (UGSS )

Measurements being made in B, V, R & I filters as part of ongoing study.

SS Cyg (Cygnus)
Annotated CCD Image 20s exposure, 2x2 binning, C Filter  2006-05-24 23:48 hUT (#127066)
SS Cyg - Reference Stars
SS Cyg variation
SS Cyg variation by colour band (QC Plots)
Animated CCD Sequence (V Band) showing +3.5 mag brightening of SS Cyg
Animated CCD Image  3 frames (3 x 30s,median combine), V filter 2006-06-15 (#128034-36), V mag +13.0 2006-06-25 (#129134-36), V Mag +  9.0 2006-07-17 (#130025-27), V Mag  +13.2
SS Cyg - Light Variation - December 2006  Dataset comprising 15 nights of observations
SS Cyg - Light Variation - August/September 2007  Dataset comprising 11 nights of observations
SS Cyg - Light Variation (Aug 2007-Jan 2008) Regular photometric measurements of SS Cyg seem to indicate that  Jan 2008 cataclysmic eruption is noticeably less bright than normal eruptions
SS Cyg - Magnitude and Colour Variation between 2006-05-24 and 2007-09-15
SS Cyg (Cygnus)
Approximate Colour CCD Image (LRGB) Luminance : 2 x 20s exposure (average combine, C Filter), Red : 3 x 30s exposure (average combine, R Filter), Green : 3 x 30s exposure (average combine, V Filter), Blue : 3 x 60s exposure (average combine, B Filter) 2 x 2 binning 2006-05-24 23:52 hUT (#127066-76)
Plots of 2006 Data
SS Cyg variation by colour band (QC Plots)

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U Gem - Dwarf Nova

U Gem (Gemini)  U Gem is a dwarf nova which erupts every  ~100 days, rising from 14th to 9th magnitude

U Gem at Mag +13.5

CCD Image  3 x 20s exposure (average combine), 2x2 binning, C filter,   2007-02-04 20:47h UT (#174176-86)

U Gem - Approximate Colour

Approximate Colour CCD Image (LRGB) Luminance: av 3 x 20s (C Filter),  Red: av 3 x 20s (R Filter) Green : av 3 x 30s (V Filter), Blue : av 3 x 60s (B Filter) 2007-02-04 20:47h UT (#174176-89)

U Gem - Baseline Image U Gem : Estimated V Mag +13.65 [ using reference Star : GSC 1375:804  V Mag 11.27 from UCAC 2.0 ]

CCD Image  3 x 30s (average combine), 2x2 binning, V Filter  2007-02-04 20:47h UT (#174178-88)

U Gem variation

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RU Peg - Dwarf Nova (Type UGSS)

RU Peg (Pegasus)

CCD Image  30s exposure, 2x2 binning, C Filter 2006-11-16 21:52h UT (#152216)

RU Peg outburst (2002) - north down

RU Peg - Photometry Results

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SU Ursae Majoris stars (Type UGSU)

Dwarf Nova characterised by the presence of two types of outburst: normal ones and supermaxima. Normal outbursts are similar to those of UGSS stars. Supermaxima are typically brighter than normal ones by 2 mag., more than five times longer and at least three times less frequent than normal maxima. During supermaxima the light curves show superimposed periodic oscillations (superhumps), whose period is close to the orbital one and whose visual amplitude is about 0.2 - 0.3 mag. The orbital periods are shorter than 0.1 day.  Examples SU UMa.

SU UMa - Cataclysmic variable star  

SU UMa (Ursa Major)

Annnotated CCD Image  3 x 60s exposure (average combine), 2x2 binning, C filter,   2007-03-12 23:59h UT (#182288-92)

SU UMa reference stars

Annotated CCD Image  120s exposure, 2x2 binning, V filter,   2007-03-12 23:57h UT (#182289)

SU UMa Variation (2007)

Animation sequence of images showing variation in SU UMa  (images from 5 separate nights between Apr 2007 & Oct 2007)

Animated CCD Images 180 sec exposure, 2x2 binning, V Filter 2007-04-28 (#192248), 2007-08-08 (#203184), 2007-08-22 (#206056) 2007-08-25 (#207032), 2007-10-17 (#221109)

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RZ LMi - (Type UGSU / ER UMa)

RZ LMi (Leo Minor)  RZ LMi is an ER UMa type star. These stars typically spend a third  of their time in superoutburst with a supercycle of 20-50 days. Outside of superoutburst  they typically pack in a rapid succession of normal outbursts, showing one every ~ 4 days RZ LMi is the star with the shortest known supercycle, spending  half its time in superoutburst and has time for only two normal outbursts in between. Estimated magnitude of RZ LMi in following image is +16.5 which indicates a brightness lying between outbursts)

CCD Image  3 x 60s exposure (average combine), 2x2 binning, C filter,   2007-02-04 22:37h UT (#174319-25)

Annotated CCD Image  180s exposure, 2x2 binning, C filter,   2007-03-12 22:46h UT (#182245)

RZ LMi Light Curves

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ER UMa (Type UGSU / ER UMa)

ER UMa (Ursa Major)  ER UMa is the prototype ER UMa type star. These stars typically spend a third  of their time in superoutburst with a supercycle of 20-50 days. Outside of superoutburst  they typically pack in a rapid succession of normal outbursts, showing one every ~ 4 days

CCD Image  60s exposure, 2x2 binning, C filter,   2007-02-04 23:31h UT (#174370)

ER UMa - Reference Stars

CCD Image  180s exposure, 2x2 binning, V filter,   2007-03-12 23:33h UT (#182273)

ER UMa Variation (2007)

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WZ Sge stars (UGWZ)

Dwarf Nova.  Examples WZ Sge

Z Camelopardalis stars (Type UGZ)

UGZ stars show cyclic outbursts but differ from UGSS stars in that sometimes after outburst they do not return to their original brightness but remain at an intermediate magnitude for the duration of several cycles. The cycle lengths are from 10 to 40 days, an dthe visual amplitudes are from 2 to 5 mag. Examples Z Cam, TT Ari

RX And [UGZ]

RX And (Andromeda) Variable Type UGZ

Annotated CCD Image 3 x 30 sec exposure (average combine), 2x2 binning, C Filter 2007-10-23 00:01hUT (#224288-94)

RX And - Reference Stars

Annotated CCD Image 45 sec exposure, 2x2 binning, V Filter 2007-10-22 23:59hUT (#224289)

Earlier Images of RX And from 2002 showing light variation (animated frames)

Animated CCD Image  (from 2002-10-03 to 2002-11-24)

RX And Photometry Results

NSV 389 Photometry Results

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TT Ari  (Type UGZ)

TT Ari (Aries)

Annotated CCD Image 3 x 30 sec exposure (average combine), 2x2 binning, C Filter 2007-10-22 23:33hUT (#224259-65)

TT Ari with several distant galaxies (PGC catalog mags +16.0 to +17.3)

Annotated CCD Image (Image details as above)

TT Ari - Reference Stars

Annotated CD Image 45 sec exposure, 2x2 binning, V Filter 2007-10-22 23:31hUT (#224260)

TT Ari Photometry Results

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SY Cnc (Type UGZ)

SY Cnc (Cancer)

Annotated CCD Image  3 x 60s exposure (average combine), 2x2 binning, C filter,   2007-03-12 21:48h UT (#182198-202)

SY Cnc - reference stars

Annotated CCD Image  120s exposure, 2x2 binning, V filter,   2007-03-12 21:47h UT (#182199)

SY Cnc Variation (2007)

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Z Andromedae stars, or symbiotic stars (Type ZAND)

Close binaries consisting of a hot star, a star of late spectral type and an extended envelope excited by the hot star's radiation. The combined brightness varies irregularly with a visual amplitude up to 4 mag. This is a very inhomogeneous class of objects.  Examples Z And.

Z And (ZAND)

Z And  (Andromeda)
CCD Image
Photometry  V & B  Bands
Further observations will be made during future sessions  in order to further refine the light / colour variation.
Z And - Colour Variation

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Other/Mixed Types

RR Tau -   - INSA

RR Tau (Taurus)

Annotated CCD Image  3 x 60s exposure (average combine), 2x2 binning, C filter,   2007-03-12 21:17h UT (#182157-69)

RR Tau - reference stars

Annotated CCD Image  120s exposure, 2x2 binning, V filter,   2007-03-12 21:10h UT (#182159)

RR Tau - colour

Approximate Colour CCD Image  Blue : 3 x 120s (B) , Green : 3x60s (V),  Red : 3x30s(R)  2x2 binning 2007-03-12 21:14h UT (#182158-68)

RR Tau Variation (2007)

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UX - novalike variable (UX UMa subtype)

UX UMa (Type EA/WD+NL) 

UX UMa (Ursa Major)

Annotated CCD Image  3 x 60s exposure (average combine), 2x2 binning, C filter,   2007-03-12 23:47h UT (#182279-832)

UX UMa - reference stars

Annotated CCD Image  120s exposure, 2x2 binning, V filter,   2007-03-12 23:49h UT (#182282)

UX UMa Variation (2007)

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VY - novalike variable (VY Scl subtype)

KR Aur  (Type VY)

KR Aur (Auriga)

Annotated CCD Image  3 x 60s exposure (average combine), 2x2 binning, C filter,   2007-03-12 22:00h UT (#182206-10)

KR Aur - reference stars

Annotated CCD Image  120s exposure, 2x2 binning, V filter,   2007-03-12 22:02h UT (#182209)

KR Aur Variation (2007)

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IBWD - interacting binary white dwarf

AM CVn  (Type IBWD) 

AM CVn (Canes Venatici)

Annotated CCD Image  3 x 60s exposure (average combine), 2x2 binning, C filter,   2007-03-12 22:25h UT (#182222-24)

AM CVn - reference stars

Annotated CCD Image  120s exposure, 2x2 binning, V filter,   2007-03-12 22:31h UT (#182229)

AM CVn Variation (2007)

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