Extreme Contrast Ratio Imaging of Sirius with a Charge Injection Device

Abstract

The next fundamental steps forward in understanding our place in the universe could be a result of advances in extreme contrast ratio (ECR) imaging and point spread function (PSF) suppression. For example, blinded by quasar light we have yet to fully understand the processes of galaxy and star formation and evolution, and there is an ongoing race to obtain a direct image of an exoearth lost in the glare of its host star. To fully explore the features of these systems we must perform observations in which contrast ratios of at least one billion can be regularly achieved with sub 0.′′ 1 inner working angles. Here we present the details of a latest generation 32-bit charge injection device (CID) that could conceivably achieve contrast ratios on the order of one billion. We also demonstrate some of its ECR imaging abilities for astronomical imaging. At a separation of two arc minutes, we report a direct contrast ratio of ∆m v = 18.3, log (CR) = 7.3, or 1 part in 20 million, from observations of the Sirius field. The atmospheric conditions present during the collection of this data prevented less modest results, and we expect to be able to achieve higher contrast ratios, with improved inner working angles, simply by operating a CID at a world-class observing site. However, CIDs do not directly provide any PSF suppression. Therefore, combining CID imaging with a simple PSF suppression technique like angular differential imaging, could provide a cheap and easy alternative to the complex ECR techniques currently being employed.

Imaging Extrasolar Giant Planets

“…GJ504 and κAnd are recent examples of young field stars with faint companions that were initially thought to have planetary masses (Carson et al 2013;Kuzuhara et al 2013) but which follow-up studies showed are probably older (Hinkley et al 2013;Bonnefoy et al 2014a;Fuhrmann & Chini 2015;Jones et al 2016), implying the companions are likely more massive and reside in the brown dwarf regime. Sirius is another example of a young massive field star extensively targeted with high-contrast imaging (Kuchner & Brown 2000;Bonnet-Bidaud & Pantin 2008;Skemer & Close 2011;Thalmann et al 2011;Vigan et al 2015;Batcheldor et al 2016). This system is particularly noteworthy for possible periodic astrometric perturbations to the orbit of its white dwarf companion Sirius B that may be caused by an still-hidden giant planet or brown dwarf (Benest & Duvent 1995).…”

Charge Injection Device Performance in Low-Earth Orbit

“…Ninkov et al (1994) initially demonstrated the viability of CIDs for astronomical imaging. Batcheldor et al (2016) furthered these observations with a CID820. The CID820 used was a 2048×2048 12 μmpixel detector with linear response up to 268k e − and a full well of 305k e − .…”

“…This is one reason why CCDs were originally the preferred devices for astronomical applications. However, modern CIDs produce read noise levels comparable to CCDs because they include a pre-amplifier per pixel architecture, random access decoders, and a non-destructive read out (NDRO) approach (Eid 1995;Kimble et al 1995;Batcheldor et al 2016).…”

“…The CID820 used by Batcheldor et al (2016) required liquid cooling and bench mounted support hardware, and was installed on a 0.8 m ground-based telescope in Florida. Despite these limitations the CID820 achieved…”

Prospects for Life on Temperate Planets around Brown Dwarfs

“…The primary obstacle, however, is that the small orbital radius of the planet, which increases the contrast as seen above, also leads to an angular separation between the planet and star that is lower than the inner working angle of current coronographs and starshades as well as charge injection devices (Batcheldor et al 2016). Finally, we wish to highlight some other crucial issues that merit further study.…”