Cataclysmic Variables in IPHAS

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Cataclysmic Variables in IPHAS

• Andrew Witham
• Christian Knigge
• IPHAS Consortium

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1 IntroductionWhy Search For New CVs With
IPHAS?

• Test theories of binary evolution and population
  synthesis models.
• There is a predicted population of short period
  CVs that are missing.
• These are expected to be strong Ha emitters.
• To establish the photometric properties and Ha
  emission line properties of CVs and look for
  correlations in these properties in an unbiased
  sample.
• To establish whether IPHAS is capable of
  discovering CVs up to its magnitude limits.

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2 A Feasibility StudyThe Known Population Of
CVs As Seen By IPHAS.

• IPHAS photometry was used to construct r Ha vs
  r i colour-colour plots.
• Objects with a significant Ha excess are
  established using fits of the main stellar locus.
• IPHAS observed 19 CVs in the galactic plane a
  further 52 have were observed outside the plane.
• The recovery rate of CVs as Ha emitters is 70
  (48/71).

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Known CVs On The IPHAS Colour-Colour Plane

• Ha emitters are red.
• Non-emitters are blue.
• Quality flagged objects are green.
• Interpolation was used to calculate EWs.
• Dwarf Novae show the greatest EWs.

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EW and Orbital Period

• The maximum EW decreases with increasing orbital
  period.

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The Period Distribution Of The Known CVs

• The period distribution of CVs detected as H
  emitters is shown in red superimposed on the
  period distribution of all the CVs observed.
• IPHAS is capable of detecting Ha emission from
  CVs irrespective of the orbital period.

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2 ID Spectroscopy Of Bright and Clear Ha
Emitters.

• CAFOS on the Calar Alto 2.2m 79 Objects
  (limited wavelength range)
• The Cassegrain Spectrograph on the CTIO 1.5m
  Telescope 10 Objects.
• The Cassegrain Spectrograph on the 1.72m DAO 30
  objects (limited wavelength range).
• FAST on the 1.5m Tillinghast Telescope 214
  objects.
• ALFOSC on the 2.5m NOT 70 objects
• Carelec On the OHP 1.93m 19 objects
• ISIS on the 4m WHT 31 analysed 20 unanalysed
  objects

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Results And Data Products

• 399 Objects have been analysed so far.
• The majority that have been classified are early
  type emission line stars.
• 6 CV Candidates
• 10 Young Stellar Objects e.g. T Tauri stars
• 20 late type stars, including some actual Ha
  emitters (active stars)
• 10 - 20 additional oddities.
• A webpage with spectra of the objects that dont
  appear to be early type stars is already setup
• A webpage with Photometry, Equivalent Width
  Measures, Classification and Spectra is coming
  soon.

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Sample Spectra
Early Type Late Type Active Late Type
Young Stellar Object CV ???
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Sample Spectra
Early Type Late Type Active Late Type
Young Stellar Object CV ???
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Sample Spectra
Early Type Late Type Active Late Type
Young Stellar Object CV ???
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Sample Spectra
Early Type Late Type Active Late Type
Young Stellar Object CV ???
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Sample Spectra
Early Type Late Type Active Late Type
Young Stellar Object CV ???
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Sample Spectra
Early Type Late Type Active Late Type
Young Stellar Object CV ???
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Conclusions I

• The bright and clear sample of H emitters from
  IPHAS is dominated by early type emission line
  objects.
• 1.5 of the objects are candidate CVs.
• Currently no technique is known for
  distinguishing the two populations with existing
  photometry.
• Further observations are warranted to confirm the
  CV nature of several objects.
• The faint and clear sample is beginning to be
  followed-up. We may see a different population
  of objects or pick up further early type emission
  line objects in a further spiral arm.

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3 Newly Discovered CVs!

• Spectroscopic follow-up of Ha emitters in the
  IPHAS survey has lead to the discovery of new
  CVs.
• In total 9 new candidate CVs have been found.
• 3 CVs have been observed further and their CV
  nature has been confirmed.
• These are
• IPHAS J013031.90622132.4 r 16.7
• IPHAS J051814.34294113.2 r 16.5
• IPHAS J062746.41014811.3 r 16.4

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Time Series Photometry of IPHAS J06270148

• The system is revealed to be eclipsing.
• From the times of eclipse minimum and the eclipse
  width over the three nights it appears the
  orbital period is just longer than 12 hours.

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Radial Velocity Analysis

• IPHAS J01306221
• IPHAS J05182941
• Average Spectra from one night of observing on
  the Calar Alto 2m

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Period Searches
IPHAS J0130 Orbital period of 3.12 hours.
IPHAS J0618 Orbital period of 5.71 hours.
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Conclusions II

• IPHAS is capable of detecting CVs at all Orbital
  Periods by virtue of their Ha emission.
• 9 new candidate CVs have been discovered so far
  from IPHAS follow-up.
• 3 bright CVs have been observed further and
  found to be long-period systems.
• Only by pushing fainter will we discover
  short-period systems.
• Recent empirical results and theory are
  beginning to suggest that a large population of
  short-period systems do not exist or are
  hidden.

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Hß EW and Absolute Magnitude

• Patterson (1984) shows empirically that fainter
  CVs produce greater Hß Equivalent Widths.
• This correlation should hold for Ha emission.

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Ha EW and Absolute Magnitude

• For CVs with known distances, absolute magnitude
  were calculated.
• For the Non-Magnetic CVs the Results agree
  qualitatively with Pattersons .

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Conclusions

• EWs of the Ha emission from CVs have been
  estimated using the IPHAS photometry.
• Short-period CVs are capable of the greatest EWs.
• Concurrently Non-magnetic faint CVs show large
  EWs.
• Therefore IPHAS has a good chance of detecting
  short period faint CVs.

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Future Possibilities

• These techniques can be used to test for Ha
  emission in CVs of an uncertain nature.
• The Equivalent Widths should be checked against
  measured EWs from spectroscopic observations.
• Absolute magnitudes of discs can be calculated to
  enable a better comparison with Pattersons work.
• It would be useful to compare the EWs and colours
  of CVs with other classes of objects such as
  X-Ray Binaries and Be Stars.

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The Pelican Nick Wright - UCL