Study of Cepheid Variables as a Joint Near IR Spectroscopy Project Thomas C. Smith (Dark Ridge...

Study of Cepheid Variables as a Joint Near IR Spectroscopy

Project

Thomas C. Smith (Dark Ridge Observatory)

Kenneth E. Kissell (Kissell Consultants)

Briefing Outline

A brief history of spectroscopy of pulsating variables

The present knowledge of pulsating variables Earlier Work Present Activities Future Work How You Can Help Q & A



A brief history of spectroscopy of pulsating variables cont. The H-R Diagram - Refresher



A brief history of spectroscopy of pulsating variables cont. Early Oxygen I Studies

a) ε Aur Ia

b) α Leo Ib

c) ζ Leo III

d) γ Vir V

ApJ, 111, 1, 1-10 (1950)



A brief history of spectroscopy of pulsating variables cont.

Partially Resolved O I Triplet in a Supergiant Ia Star



A brief history of spectroscopy of pulsating variables Variables defined mostly from brightness Cycles. Pulsating variables cycle also in temperature /

spectral type. An O I triplet feature noted by Merrill (1934) and

Keenan and Hynek (1950) as unusually strong and dependent on temp/spectral type and luminosity class.

Cepheids and RR Lyrae are in the zones of interest. Keenan suggested study of O I triplet (λ7771-7775) in

testing of S-1 image tubes in 1962. Osmer and Parsons explore detection of A-F

supergiants and Cepheids in nearby galaxies with λ7774 features (1964-1972).



A brief history of spectroscopy of pulsating variables (cont.)

O I Luminosity Effects - Epoch (1950)W




Early 1N film and S-1 image tube data (1960s)


O I Energy Levels Producing λ7774 Triplet




Cosmological Occurrence of Pulsation Instability Zones




Cepheid and RR Lyrae Pulsation Zones




Changes of the Oxygen Triplet Vs. Temperature/Spectral Type



The present knowledge of pulsating variables

Pulsation parameters Brightness Vs. phase Temperature Vs. phase Radial velocity Vs. phase Stellar radius Vs. phase

Yet-to-be established parameters O I Triplet strength Vs. phase Spectral-type Vs. phase



Earlier Work



Present Activities

1960 – 1980 Film and Image Tube work required use of 1.5 – 3.5 meter telescopes to exploit the λ7774 feature. This required good justifications for durations of telescope time needed.

21st century – CCD detectors – most sensitive of these wavelengths will allow use of advanced amateur facilities.

2006 – Began augmentations of Dark Ridge Observatory equipped with an SBIG SGS spectrograph for detailed study of bright Cepheids.

2007 – Initial spectra collected at Dark Ridge Observatory, California site, prior to relocation to New Mexico.



Present Activities (Cont.)

Luminosity Effects Using Different MeasuresW




Current: initial complications are being worked to resolve best resolution and wavelength calibration issues.

2007 through 2008: Seek to define temperature/feature strength trajectories on HR diagram.

Seek to add O I Triplet feature-strength plot (W versus phase) to existing Cepheid pulsation plots.




Early SGS Activation/Testing



Future Work (Part 1)

Luminosity Effects: Standard + Variables

Cep

T Mon

Aqlζ Gem

FF Aql




Enhanced Cepheid pulsation plots

0 0.5 1.0

O I

Eq

. W




O I Triplet Velocity Vs. Photosphere Velocity

A new challenge that must be explored.

Should permit atmospheric pulsation models to identify the height in the stellar atmosphere of the Oxygen that is producing the triplet.

It is unknown if amateur equipment and capabilities are capable of providing the required data. This requires the ability to measure the Doppler shift of the O I Triplet.



Dark Ridge Observatory (DRO)



DRO Cont.



How You Can Help

Contribute spectral observations if equipped with high-resolution grating system

( Cephei and others)

Monitor V, Rc, Ic photometry to assure the zero point of the phase.

Contribute spectral observations at lower resolutions along with standard star spectra to determine spectral-types during the cycle.



Target List

TABLE I. Cepheid Characteristics for Candidate Program StarsMagnitude

TABLE I. Cepheid Characteristics for Candidate Program Stars

Name Right Ascension Declination Magnitude Epoch Period Spectral Type h m s ° ‘ “ max min (2400000+) d======= ============= =========== ========= ========== ====== =============T Mon 06 25 37.3 +07 04 52 5.58 6.62 43784.615 27.025 F7Iab-KIIabRT Aur 06 29 03.0 +30 29 16 5.00 5.82 42361.155 3.728 F4Ib-G1I Gem 07 04 33.2 +20 33 31 3.62 4.18 43805.927 10.151 F7Ib-G3Ib-G1IbX Sgr 17 48 02.0 -29 49 59 4.20 4.90 40741.70 7.013 F5-G2IIW Sgr 18 05 30.0 -29 34 45 4.29 5.14 43374.77 7.595 F4-G2IbY Sgr 18 21 49.5 -18 51 22 5.25 6.24 40762.38 5.773 F5-G0Ib -IIFF Aql 18 58 34.8 +17 22 17 5.18 5.68 41576.428 4.471 F5Ia-F8Ia Aql 19 52 51.3 +01 01 31 3.48 4.39 36084.656 7.177 F6Ib-G4IbS Sge 19 56 21.7 +16 39 18 5.24 6.04 42678.792 8.382 F6Ib-G5IbX Cyg 20 43 41.8 +35 36 54 5.85 6.91 43830.387 16.386 F7Ib-G8IbT Vul 20 51 47.4 +28 16 44 5.41 6.09 41705.121 4.435 F5Ib-G0IbCep 22 29 27.1 +58 27 13 3.48 4.37 36075.445 5.366 F5Ib-G1Ib

======= ============= ========== ========= ========== ====== =============RR Lyr 19 25 42.3 +42 47 57 7.06 8.12 50238.499 0.567 A5.0-F7.0



Q & A

Don’t Be Shy!

For information regarding how you can assist in this rediscovered project:

http://www.darkridgeobservatory.org



Study of Cepheid Variables as a Joint Near IR Spectroscopy Project Thomas C. Smith (Dark Ridge...

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