GALACTIC CEPHEIDS WITH SPITZER. I. LEAVITT LAW AND COLORS

Journal Article · Wed Jan 20 04:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/709/1/120· OSTI ID:21392348

Marengo, M ^[1]; Evans, N R; Barmby, P ^[2]; Bono, G ^[3]; Welch, D L ^[4]; Romaniello, M ^[5]

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1. Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)
2. Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States)
3. Department of Physics, Universita di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma (Italy)
4. Dept. of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada)
5. European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei Munchen (Germany)

Classical Cepheid variable stars have been important indicators of extragalactic distance and Galactic evolution for over a century. The Spitzer Space Telescope has opened the possibility of extending the study of Cepheids into the mid- and far-infrared, where interstellar extinction is reduced. We have obtained photometry from images of a sample of Galactic Cepheids with the Infrared Array Camera (IRAC) and Multiband Infrared Photometer for Spitzer instruments on Spitzer. Here we present the first mid-infrared period-luminosity relations for Classical Cepheids in the Galaxy, and the first ever Cepheid period-luminosity relations at 24 and 70 mum. We compare these relations with theoretical predictions, and with period-luminosity relations obtained in recent studies of the Large Magellanic Cloud. We find a significant period-color relation for the [3.6] - [8.0] IRAC color. Other mid-infrared colors for both Cepheids and non-variable supergiants are strongly affected by variable molecular spectral features, in particular deep CO absorption bands. We do not find strong evidence for mid-infrared excess caused by warm (approx500 K) circumstellar dust. We discuss the possibility that recent detections with near-infrared interferometers of circumstellar shells around delta Cep, l Car, Polaris, Y Oph, and RS Pup may be a signature of shocked gas emission in a dust-poor wind associated with pulsation-driven mass loss.

• OSTI ID: 21392348
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 709; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
CAMERAS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CEPHEIDS
CHALCOGENIDES
COLOR
DUSTS
EMISSION
EVOLUTION
GALACTIC EVOLUTION
GALAXIES
INDICATORS
INTERFEROMETERS
LUMINOSITY
MAGELLANIC CLOUDS
MEASURING INSTRUMENTS
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHOTOMETERS
PHOTOMETRY
PHYSICAL PROPERTIES
PULSATING VARIABLE STARS
PULSATIONS
SORPTION
STARS
TELESCOPES
VARIABLE STARS