Deep L' and M-band Imaging for Planets Around Vega and epsilon Eridani

TL;DR

This study used deep adaptive optics imaging at L' and M bands to search for planets around Vega and epsilon Eridani, providing new sensitivity limits and demonstrating the potential for ground-based detection of known exoplanets.

Contribution

First to utilize L' and M band AO imaging for these stars, showing improved sensitivity and potential for detecting epsilon Eri b with existing instruments.

Findings

No planets detected around Vega or epsilon Eri.

M band imaging offers superior sensitivity for close-in planets.

Potential to detect epsilon Eri b at its 2010 apastron with current AO technology.

Abstract

We have obtained deep Adaptive Optics (AO) images of Vega and epsilon Eri to search for planetary-mass companions. We observed at the MMT in the L' (3.8 micron) and M (4.8 micron) bands using Clio, a recently commissioned imager optimized for these wavelengths. Observing at these long wavelengths represents a departure from the H band (1.65 microns) more commonly used for AO imaging searches for extrasolar planets. The long wavelengths offer better predicted planet/star flux ratios and cleaner (higher Strehl) AO images, at the cost of lower diffraction limited resolution and higher sky background. We have not detected any planets or planet candidates around Vega or epsilon Eri. We report the sensitivities obtained around both stars, which correspond to upper limits on any planetary companions which may exist. The sensitivities of our L' and M band observations are comparable to those of the best H-regime observations of these stars. For epsilon Eri our M band observations deliver considerably better sensitivity to close-in planets than any previously published results, and we show that the M band is by far the best wavelength choice for attempts at ground-based AO imaging of the known planet epsilon Eri b. The Clio camera itself with MMTAO may be capable of detecting epsilon Eri b at its 2010 apastron, given a multi-night observing campaign. Clio appears to be the only currently existing AO imager that has a realistic possibility of detecting epsilon Eri b.