Abstract
We present the current status of Hα high-contrast imaging observations with Subaru/Subaru Coronagraphic Extreme Adaptive Optics + VAMPIRES. Our adaptive optics correction at optical wavelengths in combination with (double) spectral differential imaging (SDI) and angular differential imaging (ADI) was capable of resolving a ring feature around omi Cet and detect the Hα counterpart of jet around RY Tau. We tested the post-processing by changing the order of ADI and SDI and both of the contrast limits achieved ∼10 − 3 to 5 × 10 − 4 at 0.3″, which is comparable to other Hα high-contrast imaging instruments in the Southern Hemisphere such as very large telescope (VLT)/spectro-polarimetric high-contrast exoplanet research, VLT/MUSE, and Magellan AO. Current wavefront sensing and adaptive optics correction at optical wavelengths empirically depend on airmass, and Subaru/VAMPIRES provide great opportunities for Hα high-contrast imaging for Northern Hemisphere targets.
Highlights
Observing hydrogen lines provides fruitful opportunities to investigate mass accretion, shocks, jets, atmospheres, and other astrophysical phenomena
The smaller number of KL modes subtracts the starlight less efficiently and leaves a lot of residuals. Both of the reduction approaches resulted in almost the same outputs and detected omicron Ceti (omi Cet) B with SNRs >5000, but with the angular differential imaging (ADI) + dSDI reduction [Fig. 7(b)], there still remains some stellar halo at the inner working angle
We present high-contrast Hα observations with Subaru/Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) + VAMPIRES
Summary
Observing hydrogen lines provides fruitful opportunities to investigate mass accretion, shocks, jets, atmospheres, and other astrophysical phenomena. Further improvements in instrumentation have made it possible to operate AO correction at optical wavelengths [e.g., very large telescope (VLT)/multi unit spectroscopic explorer (MUSE),[3] VLT/spectro-polarimetric high-contrast exoplanet research (SPHERE),[4] Magellan AO (MagAO),[5] and Subaru/Subaru Coronagraphic Extreme Adaptive Optics (SCExAO)6] and have kicked off a new era of high-contrast imaging at Hα (λ 1⁄4 656.28 nm). We have installed a new observing mode of The Visible Aperture Masking Polarimetric Imager for Resolved Exoplanetary Structures (VAMPIRES) at Subaru Telescope,[15] which is the only instrument capable of Hα imaging fed by AO in the Northern Hemisphere at the moment. VAMPIRES is capable of performing diffraction limited, polarimetric imaging at visible wavelengths (600 to 800 nm) It uses two electron-multiplying CCD (EMCCD) cameras that in normal operation each record an orthogonal polarisation, which in combination with a ferroelectric liquid crystal modulator and half-waveplate allow precise polarimetric differential imaging (PDI). The splitting of the light before encountering the filters is performed via a non-polarizing beamsplitter, to minimize mixing of polarization effects with spectral differential imaging (SDI; see Sec. 3)[20] signal
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