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High Contrast Stellar Observations within the Diffraction Limit at the Palomar Hale Telescope

Mennesson, B. and Hanot, C. and Serabyn, E. and Martin, S. R. and Liewer, K. and Loya, F. and Mawet, D. (2010) High Contrast Stellar Observations within the Diffraction Limit at the Palomar Hale Telescope. In: Ground-based and Airborne Instrumentation for Astronomy Ill. Proceedings of SPIE. No.7735. Society of Photo-Optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 773511. ISBN 978-0-81948-225-9.

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We report on high-accuracy, high-resolution (< 20mas) stellar measurements obtained in the near infrared (≃ 2.2 microns) at the Palomar 200 inch telescope using two elliptical (3m x 1.5m) sub-apertures located 3.4m apart. Our interferometric coronagraph, known as the "Palomar Fiber Nuller" (PFN), is located downstream of the Palomar adaptive optics (AO) system and recombines the two separate beams into a common singlemode fiber. The AO system acts as a "fringe tracker", maintaining the optical path difference (OPD) between the beams around an adjustable value, which is set to the central dark interference fringe. AO correction ensures high efficiency and stable injection of the beams into the single-mode fiber. A chopper wheel and a fast photometer are used to record short (< 50ms per beam) interleaved sequences of background, individual beam and interferometric signals. In order to analyze these chopped null data sequences, we developed a new statistical method, baptized "Null Self-Calibration" (NSC), which provides astrophysical null measurements at the 0.001 level, with 1 σ uncertainties as low as 0.0003. Such accuracy translates into a dynamic range greater than 1000:1 within the diffraction limit, demonstrating that the approach effectively bridges the traditional gap between regular coronagraphs, limited in angular resolution, and long baseline visibility interferometers, whose dynamic range is restricted to ≃ 100:1. As our measurements are extremely sensitive to the brightness distribution very close to the optical axis, we were able to constrain the stellar diameters and amounts of circumstellar emission for a sample of very bright stars. With the improvement expected when the PALM-3000 extreme AO system comes on-line at Palomar, the same instrument now equipped with a state of the art low noise fast read-out near IR camera, will yield 10^(-4) to 10^(-3) contrast as close as 30 mas for stars with K magnitude brighter than 6. Such a system will provide a unique and ideal tool for the detection of young (<100 Myr) self-luminous planets and hot debris disks in the immediate vicinity (0.1 to a few AUs) of nearby (< 50pc) stars.

Item Type:Book Section
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Mennesson, B.0000-0003-4205-4800
Mawet, D.0000-0002-8895-4735
Additional Information:© 2010 Society of Photo-Optical Instrumentation Engineers (SPIE). July 14, 2010. This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. We wish to thank the Palomar Observatory staff for their assistance in mount ing the PFN and conducting the observations at the Hale telescope.
Funding AgencyGrant Number
Subject Keywords:infrared: stars - instrumentation: coronagraphs, interferometers - stars: circumstellar matter - stars: individual (α Boo, Vega, ρ Per)
Series Name:Proceedings of SPIE
Issue or Number:7735
Record Number:CaltechAUTHORS:20150526-123956248
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Official Citation:B. Mennesson ; C. Hanot ; E. Serabyn ; S. R. Martin ; K. Liewer, et al. "High contrast stellar observations within the diffraction limit at the Palomar Hale telescope", Proc. SPIE 7735, Ground-based and Airborne Instrumentation for Astronomy III, 773511 (July 14, 2010); doi:10.1117/12.857633
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57810
Deposited On:26 May 2015 20:42
Last Modified:10 Nov 2021 21:55

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