High Resolution Spectroscopy in the Non-thermal Infrared: Use of an Existing Coud\`e System

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Session 51 -- Instrumentation
Display presentation, Wednesday, 9:20-6:30, Pauley Room

[51.04] High Resolution Spectroscopy in the Non-thermal Infrared: Use of an Existing Coud\`e System

Gibor Basri (UC Berkeley), Geoffrey W. Marcy (San Francisco State Univ., UC Berkeley)

We describe a recent effort to use a NICMOS 3 chip as the detector on the 160" coud\'e spectrograph camera at Lick Observatory. This new instrument (IRCS) has a useful spectral range of 1-2$\mu$ with spectral coverage in one exposure of about 25\AA, and resolutions up to 75000. We have successfully obtained astronomical observations with essentially no modification of the (uncooled) spectrograph, using an existing grating blazed at 1.22$\mu$, and a dewar without optics (but containing a filter) easily mounted at the position of the old photographic plates. The throughput of the system is very high. Its sensitivity is primarily limited by the background from the warm spectrograph. Using filters with 0.1$\mu$ bandwidth, the expected background is negligible below 1.5$\mu$, but limits exposures to one minute near 2$\mu$. With an optimized dewar, one can remain photon (rather than background) limited down to 10th magnitude even at 2$\mu$.

Our current system (using a test dewar and engineering grade chip) has been tested at 1.6$\mu$. We have operated with and without an image slicer. We show spectra and discuss the current successes and problems. Our first application is to study the Zeeman--sensitive line at 1.56$\mu$ at high resolution. We expect to be able to achieve S/N of 200:1 in 10 minutes on 6th magnitude stars now, and eventually 100:1 in one hour on 10th magnitude stars using the 3-m telescope. This opens the possibility of measuring magnetic fields for large numbers of RS CVN and dM(e) stars (in addition to many G,K dwarfs), and even perhaps a few pre-main sequence stars. There is a lot of potential for science in the 1-2$\mu$ range at high resolution, which cannot be done as easily with any other type of instrument. This includes: (1) molecular lines in giants and winds, (2) lines from the ISM for abundances and kinematics, (3) detailed atmospheric analysis of embedded stars (and disks?).

Wednesday program listing