Infrared Photometry of Eta Aql

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Infrared Photometry of Eta Aql

• Fall 2005 AAVSO Conference
• By Doug West, Doug Hodgson, and Ken Luedeke

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AAVSO IR Photometry Group

• Five SSP-4 photometers on loan to membership
• Group started observing in 2003
• Over 600 J and H band observations have been
  submitted to the AAVSO from the IR Group
• Variable stars under active observation Mira, R
  Leo, Algol, Eta Aql, Beta Lyr, delta Sco, S Vir,
  W Ori, Rho Cas, Eta Gem,
• More information about the group can be found on
  the AAVSO web page http//www.aavso.org/observing/
  programs/pep/ir.shtml

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SSP-4 Photometer Mounted on a Meade 10 LX200
Telescope
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Outline of the SSP-4 Photometer
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InGaAs Detector Response

• Highest response in H
• Band (1.65 micron)
• Lower response than
• Typical visible band silicon
• Detector
• Typically cooled to -40 C

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MKO J and H Band Filter Response
MKO Mauna Kea Observatories Endorsed by the
IAU Narrower filters to avoid H20
Contamination J is 1.25 micron, 0.2 micron
fwhm H is 1.65 micron, 0.3 micron fwhm
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Eta Aql Facts

• Classical Cepheid Variable delta Cep type
• Spectral type F6Iab
• V magnitude varies from 3.48 to 4.39 with a
  period of 7.1766 days
• AAVSO star 194700

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Eta Aql Phase Plot Over Two Periods with Error
Bars
Error bars are derived from the standard
deviation of individual measurements. P7.1766d.
H
J
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Averaged Phase Plot
Averaged in phase and magnitude with adjacent
points. Note the bump at approximately 0.4
phase. P7.1766d.
H
J
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Visual, J Band, and H Band Light Curves
Phase lag for the IR bands when compared to the
visual band.
J
H
AAVSO visual
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AAVSO Visual Light Curve
Visual Magnitude
Phase
Acknowledgment This phase curve was prepared by
Grant Foster
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Summary of Photometry Results

• Comparison star HD 188512, J2.19 and H1.72
• Check star HD 182640, J2.70 and H2.55
• Average J magnitude 2.42, range 0.3 mag
• Average H magnitude 2.05, range 0.2 mag
• J and H photometry lags visual observations by
  0.2 cycle
• There is a bump in both the visual and IR light
  curves at approximately phase 0.35 to 0.4.
• P 7.176641 days Epoch 36084.656 (GCVS V4.2) ,
  visual
• P7.1760 /- 0.0037 days Epoch 2453097.9167 (this
  study) J,H
• P7.1763 days (AAVSO, Grant Foster) Visual

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References

• Welch, D.L., Wieland, F., McAlary, C.W.,
  McGonegal, R., Madore, B.F., McLaren, R.A., and
  Neugebauer, G., JHK Observations of Classical
  Cepheids, The Astrophysical Journal Supplement
  Series, 54547-579, 1984 April.
• Hindsley, R.B., and Bell, R.A., The Cepheid
  Infrared Period-Luminosity Relations, The
  Astrophysical Journal, 348 673-681, 1990 January
  10.
• Barnes III, T.G., Fernley, J.A., Frueh, M.L.,
  Navas, J.G., Moffett, T.J., and Skillen, I.,
  BVRIJHK Photometry of Cepheid Variables,
  Publications of the Astronomical Society of the
  Pacific, 109 645-658, 1997 June.
• West, D., Single Channel Infrared Photometry with
  a Small Telescope, WestSkies Observatory,
  Mulvane, Kansas, USA. Invited talk at the 1st
  Virtual Meeting on Amateur Astronomy. 2004.
• Kukarkin, B.V., Kholopov, P.N., Pskovsky, Y.P.,
  Efremov, Y.N., Kukarkina, N.P., Kurochkin, N.E.,
  and Medvedeva, G.I. General Catalogue of
  Variable Stars, 3rd ed., 1971.