Surveying the 217.5 nm extinction feature with a small satellite
- Paper number
IAC-15,A7,2,3,x28610
- Author
Mr. Avigdor Blasberger, TECHNION - Israel Institute of Technology, Israel
- Year
2015
- Abstract
The 217.5 nm extinction feature in the ultraviolet (UV) was identified by Stecher (1965). A broader investigation was conducted with IUE in 1979, however this feature was never explored systematically. The WSO/UV telescope planned to launch in 2019 is promising, but UV extinction is not included in its primary mission. We propose here a small and relatively inexpensive mission that will enable a deeper study and provide physical insights into the nature of the 217.5 nm extinction. Results obtained until now show that the central wavelength of the feature is stable at 217.44±1.7 nm (Fitzpatrick & Massa 1988) and its profile can be described as a Drude profile of A/Av vs. 1/ for different Rv’s (Cardelli, Clayton & Mathis 1989) Establishing the existence of the feature, as well as studying its strength and distribution, can be done using two bore-sighted UV cameras, one with a narrow-band filter and one with a broad-band filter, both centered around 217.5 nm. The ratio of the fluxes collected by the two cameras will provide a definitive measurement of the absorption strength. Assuming one year of space operation, we will be able to investigate tens of thousands of stars, starting from a complete Gould Belt survey, which will include hundreds of O and B stars. A periodic calibration of the instrument will be conducted using UV standard stars (e.g., Holberg & Bergeron 2006) This mission can be performed for a reasonable cost with a small satellite equipped with two UV cameras. The narrow band filter camera shall have a ~ 10 cm wide aperture, while the wider band filter camera shall have a ~4 cm aperture. To minimize power consumption as well as for simplicity of design, we propose to use CMOS detectors on both cameras. We will present details of the proposed experiment as well as a preliminary layout of the satellite. References Fitzpatrick, E.-L. & Massa, D. 1985, ApJ 307, 286 Holberg, J.B. & Bergeron, P. 2006, AJ 132, 1221 Stecher, T.P. 1965, ApJ 142, 1683 J.A. Cardelli G. C. Clayton & J.S. Mathis 1989 ApJ 345,245
- Abstract document
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