16 research outputs found
SCExAO/MEC and CHARIS Discovery of a Low Mass, 6 AU-Separation Companion to HIP 109427 using Stochastic Speckle Discrimination and High-Contrast Spectroscopy
We report the direct imaging discovery of a low-mass companion to the nearby
accelerating A star, HIP 109427, with the Subaru Coronagraphic Extreme Adaptive
Optics (SCExAO) instrument coupled with the MKID Exoplanet Camera (MEC) and
CHARIS integral field spectrograph. CHARIS data reduced with reference star PSF
subtraction yield 1.1-2.4 m spectra. MEC reveals the companion in and
band at a comparable signal-to-noise ratio using stochastic speckle
discrimination, with no PSF subtraction techniques. Combined with complementary
follow-up photometry from Keck/NIRC2, the SCExAO data favors a
spectral type, effective temperature, and luminosity of M4-M5.5, 3000-3200 ,
and , respectively.
Relative astrometry of HIP 109427 B from SCExAO/CHARIS and Keck/NIRC2, and
complementary Gaia-Hipparcos absolute astrometry of the primary favor a
semimajor axis of au, an eccentricity of
, an inclination of degrees, and a
dynamical mass of . This work shows the
potential for extreme AO systems to utilize speckle statistics in addition to
widely-used post-processing methods to directly image faint companions to
nearby stars near the telescope diffraction limit.Comment: 13 pages, 7 figures, 3 table
MKID digital readout tuning with deep learning
Microwave Kinetic Inductance Detector (MKID) devices offer inherent spectral resolution, simultaneous read out of thousands of pixels, and photon-limited sensitivity at optical wavelengths. Before taking observations the readout power and frequency of each pixel must be individually tuned, and if the equilibrium state of the pixels change, then the readout must be retuned. This process has previously been performed through manual inspection, and typically takes one hour per 500 resonators (20 h for a ten-kilo-pixel array). We present an algorithm based on a deep convolution neural network (CNN) architecture to determine the optimal bias power for each resonator. The bias point classifications from this CNN model, and those from alternative automated methods, are compared to those from human decisions, and the accuracy of each method is assessed. On a test feed-line dataset, the CNN achieves an accuracy of 90% within 1 dB of the designated optimal value, which is equivalent accuracy to a randomly selected human operator, and superior to the highest scoring alternative automated method by 10%. On a full ten-kilopixel array, the CNN performs the characterization in a matter of minutes — paving the way for future mega-pixel MKID arrays
The ARCONS Pipeline: Data Reduction for MKID Arrays
The Array Camera for Optical to Near-IR Spectrophotometry, or ARCONS, is a
camera based on Microwave Kinetic Inductance Detectors (MKIDs), a new
technology that has the potential for broad application in astronomy. Using an
array of MKIDs, the instrument is able to produce time-resolved imaging and
low-resolution spectroscopy constructed from detections of individual photons.
The arrival time and energy of each photon are recorded in a manner similar to
X-ray calorimetry, but at higher photon fluxes. The technique works over a very
large wavelength range, is free from fundamental read noise and dark-current
limitations, and provides microsecond-level timing resolution. Since the
instrument reads out all pixels continuously while exposing, there is no loss
of active exposure time to readout. The technology requires a different
approach to data reduction compared to conventional CCDs. We outline here the
prototype data reduction pipeline developed for ARCONS, though many of the
principles are also more broadly applicable to energy-resolved photon counting
arrays (e.g., transition edge sensors, superconducting tunnel junctions). We
describe the pipeline's current status, and the algorithms and techniques
employed in taking data from the arrival of photons at the MKID array to the
production of images, spectra, and time-resolved light curves.Comment: 16 pages, 19 figures, pdflatex, accepted for ApJ
ARCONS: A 2024 Pixel Optical through Near-IR Cryogenic Imaging Spectrophotometer
We present the design, construction, and commissioning results of ARCONS, the
Array Camera for Optical to Near-IR Spectrophotometry. ARCONS is the first
ground-based instrument in the optical through near-IR wavelength range based
on Microwave Kinetic Inductance Detectors (MKIDs). MKIDs are revolutionary
cryogenic detectors, capable of detecting single photons and measuring their
energy without filters or gratings, similar to an X-ray microcalorimeter. MKIDs
are nearly ideal, noiseless photon detectors, as they do not suffer from read
noise or dark current and have nearly perfect cosmic ray rejection. ARCONS is
an Integral Field Spectrograph (IFS) containing a lens-coupled 2024 pixel MKID
array yielding a 20"x20" field of view, and has been deployed on the Palomar
200" and Lick 120" telescopes for 24 nights of observing. We present initial
results showing that ARCONS and its MKID arrays are now a fully operational and
powerful tool for astronomical observations.Comment: 12 pages, 16 figures, submitted to PAS
Direct detection of SDSS J0926+3624 orbital expansion with ARCONS
AM Canum Venaticorum (AM CVn) stars belong to a class of ultracompact, short-period binaries with spectra dominated largely by helium. SDSS J0926+3624 is of particular interest as it is the first observed eclipsing AM CVn system. We observed SDSS J0926+3624 with the Array Camera for Optical to Near-IR Spectrophotometry (ARCONS) at the Palomar 200″ telescope. ARCONS uses a relatively new type of energy-resolved photon counters called Microwave Kinetic Inductance Detectors. ARCONS, sensitive to radiation from 350 to 1100 nm, has a time resolution of several microseconds and can measure the energy of a photon to ∼10 per cent. We present the light curves for these observations and examine changes in orbital period from prior observations. Using a quadratic ephemeris model, we measure a period rate of change Ṗ = (3.07 ± 0.56) × 10−13. In addition, we use the high timing resolution of ARCONS to examine the system's high-frequency variations and search for possible quasi-periodic oscillations (QPOs). Finally, we use the instrument's spectral resolution to examine the light curves in various wavelength bands. We do not find any high-frequency QPOs or significant spectral variability throughout an eclipse
Excess Optical Enhancement Observed with ARCONS for Early Crab Giant Pulses
We observe an extraordinary link in the Crab pulsar between the enhancement
of an optical pulse and the timing of the corresponding giant radio pulse. At
optical through infrared wavelengths, our observations use the high time
resolution of ARCONS, a unique superconducting energy-resolving photon-counting
array at the Palomar 200-inch telescope. At radio wavelengths, we observe with
the Robert C. Byrd Green Bank Telescope and the GUPPI backend. We see an
increase in peak optical flux for pulses that have an
accompanying giant radio pulse arriving near the peak of the optical main
pulse, in contrast to a increase when an accompanying giant radio
pulse arrives soon after the optical peak. We also observe that the peak of the
optical main pulse is enhanced when there is a giant radio pulse
accompanying the optical interpulse. We observe no statistically significant
spectral differences between optical pulses accompanied by and not accompanied
by giant radio pulses. Our results extend previous observations of
optical-radio correlation to the time and spectral domains. Our refined
temporal correlation suggests that optical and radio emission are indeed
causally linked, and the lack of spectral differences suggests that the same
mechanism is responsible for all optical emission.Comment: 5 pages, 5 figures. Updated to match revised version, accepted to
ApJL Nov 7, 2013. Several additions and improved DM in timing solutio