Chan-Kao Chang
A5050946080- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Planetary Science and Exploration
- Astronomical Observations and Instrumentation
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Astrophysics and Star Formation Studies
- Isotope Analysis in Ecology
- Geomagnetism and Paleomagnetism Studies
- Adaptive optics and wavefront sensing
- High-pressure geophysics and materials
- Pulsars and Gravitational Waves Research
- Geophysics and Gravity Measurements
- Nuclear Physics and Applications
- Space Exploration and Technology
- Solar and Space Plasma Dynamics
- Space Satellite Systems and Control
- Geological and Geochemical Analysis
- Optical Systems and Laser Technology
- Nuclear physics research studies
- Solar Radiation and Photovoltaics
- Integrated Circuits and Semiconductor Failure Analysis
- Industrial Vision Systems and Defect Detection
- Particle Accelerators and Free-Electron Lasers
- Geophysics and Sensor Technology
ATA Engineering (United States)
2024
Institute of Astronomy and Astrophysics, Academia Sinica
2021-2023
National Central University
2012-2022
The Zwicky Transient Facility (ZTF) is a new optical time-domain survey that uses the Palomar 48 inch Schmidt telescope. A custom-built wide-field camera provides 47 deg2 field of view and 8 s readout time, yielding more than an order magnitude improvement in speed relative to its predecessor survey, Factory. We describe design implementation observing system. ZTF data system at Infrared Processing Analysis Center near-real-time reduction identify moving varying objects. outline analysis...
The Zwicky Transient Facility (ZTF), a public-private enterprise, is new time domain survey employing dedicated camera on the Palomar 48-inch Schmidt telescope with 47 deg$^2$ field of view and 8 second readout time. It well positioned in development astronomy, offering operations at 10% scale style Large Synoptic Survey Telescope (LSST) single 1-m class telescope. public surveys will cover observable northern sky every three nights g r filters visible Galactic plane night r. Alerts...
The Zwicky Transient Facility is a large optical survey in multiple filters producing hundreds of thousands transient alerts per night. We describe here various machine learning (ML) implementations and plans to make the maximal use data set by taking advantage temporal nature data, further combining it with other sets. start initial steps separating bogus candidates from real ones, stars galaxies, go on classification objects into classes. Besides usual methods (e.g., based features...
Abstract We present visible and near-infrared (NIR) photometric spectroscopic observations of interstellar object (ISO) 2I/Borisov taken from 2019 September 10 to December 20 using the GROWTH, Apache Point Observatory Astrophysical Research Consortium 3.5 m, NASA Infrared Telescope Facility 3.0 m combined with pre- postdiscovery 2I obtained by Zwicky Transient March 17 May 5. Comparison imaging distant solar system comets shows an very similar mildly active outgassing rate ∼10 27 mol s −1 ....
Abstract We present time-resolved visible spectrophotometry of 2020 CD 3 , the second known minimoon. The was taken with Keck I/Low Resolution Imaging Spectrometer between wavelengths 434 and 912 nm in B g V R I RG850 filters as it leaving Earth–Moon system on March 23 UTC. spectrum resembles V-type asteroids some lunar rock samples a 434–761 reddish slope ∼18%/100 ( – r = 0.62 ± 0.08 i 0.21 0.06) an absorption band at ∼900 corresponding to z −0.54 0.10. Combining our measured H 31.9 0.1...
Abstract We present visible and mid-infrared imagery photometry of temporary Jovian co-orbital comet P/2019 LD 2 taken with Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3), Spitzer Telescope/Infrared Array (Spitzer/IRAC), the GROWTH telescope network, spectroscopy from Keck/Low-Resolution Imaging Spectrometer (LRIS), archival Zwicky Transient Facility observations between 2019 April 2020 August. Our indicate that nucleus has a radius 0.2 1.8 km assuming 0.08 albedo coma dominated by...
A new asteroid rotation period survey have been carried out by using the Palomar Transient Factory (PTF). Twelve consecutive PTF fields, which covered an area of 87 deg$^2$ in ecliptic plane, were observed $R$ band with a cadence $\sim$20 min during February 15--18, 2013. We detected 2500 known asteroids diameter range 0.5 km $\leq D \leq$ 200 km. Of these, 313 objects had highly reliable periods and exhibited "spin barrier" at $\sim2$ hours. In contrast to flat spin rate distribution 3 15...
We describe ZStreak, a semi-real-time pipeline specialized in detecting small, fast-moving, near-Earth asteroids (NEAs), which is currently operating on the data from newly commissioned Zwicky Transient Facility (ZTF) survey. Based prototype originally developed by Waszczak et al. (2017) for Palomar Factory (PTF), predecessor of ZTF, ZStreak features an improved machine-learning model that can cope with 10× rate increment between PTF and ZTF. Since its first discovery 2018 February 5 (2018...
Abstract We observed the episodically active asteroid (6478) Gault in 2020 with multiple telescopes Asia and North America found that it is no longer after its recent outbursts at end of 2018 start 2019. The inactivity during this apparition allowed us to measure absolute magnitude H r = 14.63 ± 0.02, G 0.21 0.02 from our secular phase-curve observations. In addition, we were able constrain Gault’s rotation period using time-series photometric lightcurves taken over 17 hr on days August,...
Asteroids of size larger than 150 m generally do not have rotation periods smaller 2.2 hr. This spin cutoff is believed to be due the gravitationally bound rubble-pile structures asteroids. Rotation with exceeding this critical value will cause asteroid breakup. Up until now, only one object, 2001 OE84, has been found an exception cutoff. We report discovery a new super-fast rotator, (335433) 2005 UW163, spinning period 1.290 hr and light curve variation r' ∼ 0.8 mag from observations made...
In order to look for large super-fast rotators, five dedicated surveys covering ~ 188 square degree in the ecliptic plane have been carried out R-band with ~10 min cadence using intermediate Palomar Transient Factory late 2014 and early 2015. Among 1029 reliable rotation periods obtained from surveys, we discovered one new rotator, (40511) 1999 RE88, other 18 candidates. RE88 is an S-type inner main-belt asteroid a diameter of D = 1.9 +- 0.3 km, which has period P 1.96 0.01 hr lightcurve...
ABSTRACT The wide-field synoptic sky surveys, known as the Palomar Transient Factory (PTF) and intermediate (iPTF), will accumulate a large number of new RR Lyrae. These Lyrae are good tracers to study substructure Galactic halo if their distance, metallicity, galactocentric velocity can be measured. Candidates identified from distance metallicity before requesting spectroscopic observations for confirmation. This is because both quantities obtained via photometric light curves, absolute V...
Abstract Rotation periods of 53 small (diameters 2 km < D 40 km) Jupiter Trojans (JTs) were derived using the high-cadence lightcurves obtained by FOSSIL phase I survey, a Subaru/Hyper Suprime-Cam intensive program. These are first reported measured for JTs with 10 km. We found lower limit rotation period near 4 hr, instead previously published result 5 hr larger JTs. Assuming rubble-pile structure JTs, bulk density ≈0.9 g cm −3 is required to withstand this spin rate limit, consistent...
(144977) 2005 EC127 is an V-/A-type inner-main-belt asteroid with a diameter of 0.6 +- 0.1 km. Asteroids this size are believed to have rubble-pile structure, and, therefore, cannot rotation period shorter than 2.2 hours. However, our measurements show that completes one in 1.65 0.01 hours peak-to-peak light-curve variation ~0.5 mag. Therefore, identified as large super-fast rotator. Either bulk density ~6 g cm^-3 or internal cohesion 47 30 Pa can explain EC127. the scenario high very...
Abstract A class of asteroids, called large super-fast rotators (large SFRs), have rotation periods shorter than 2 hr and diameters larger ∼0.3 km. They pose challenges to the usual interior rubble-pile structure unless a relatively high bulk density is assumed. So far, only six SFRs been found. Therefore, we present survey asteroid using Panoramic Survey Telescope Rapid Response System (Pan-STARRS) 1 telescope during 2016 October 26–31 search for more study their properties. total 876...
This paper presents an innovative transformer deep learning-based outlier detection approach aimed at efficiently reducing Defective Parts Per Million (DPPM) while maintaining competitive testing costs. By leveraging learning techniques, key parameters are predicted. Outlier ICs identified through a comparison of predicted and measured values. The comparative analysis performed on our proposed approach, along with traditional methodologies such as dynamic part average (D-PAT) nearest...
Eight campaigns to survey asteroid rotation periods have been carried out using the intermediate Palomar Transient Factory in past 3 years. 2780 reliable were obtained, from which we identified two new super-fast rotators (SFRs), (335433) 2005 UW163 and (40511) 1999 RE88, 23 candidate SFRs. Along with other three known rotators, there are five SFRs so far. Contrary case of rubble-pile asteroids (i.e., bounded aggregations by gravity only), an internal cohesion, ranging 100 1000 Pa, is...
The intra-night trajectories of asteroids can be approximated by straight lines, and so are their detections. Therefore, the Hough transform, a line detecting algorithm, used to connect line-up detections find asteroids. We applied this algorithm high-cadence Pan-STARRS 1 (PS1) observation, which was originally designed collect asteroid light curves for rotation period measurements (Chang et al., 2019). recovered most known in observing fields and, moreover, discovered 3574 new with...
We initiated the bilateral collaboration between Lulin Observatory and Purple Mountain to collect asteroid lightcurves using Chinese Near-Earth Object Survey Telescope at Xuyi Observation Station. The primary goal of this was discover super-fast rotators (SFRs) study their physical properties. Two campaigns have been conducted: (a) a survey ∼45 deg2 8 minute cadence during 2017 February 26–March 2, (b) ∼60 10 2018 March 9–12. Our samples are mainly main-belt asteroids some Hildas Jupiter...
We report the discovery of two new Be stars, and re-identify one known star in open cluster NGC 6830. Eleven Hα emitters were discovered using imaging photometry Palomar Transient Factory Survey. Stellar membership candidates was verified with photometric kinematic information 2MASS data proper motions. The spectroscopic confirmation carried out by Shane 3 m telescope at Lick observatory. Based on their spectral types, three confirmed as stars equivalent widths greater than −10 Å. Two...
Neutron star-helium white dwarf (NS+He WD) binaries are important evolutionary products of close-orbit binary star systems. They often observed as millisecond pulsars and may continue evolving into ultra-compact X-ray (UCXBs) continuous gravitational wave (GW) sources that will be detected by space-borne GW observatories, such LISA, TianQin Taiji. Nevertheless, the stability NS+He WD undergoing mass transfer is not well studied still under debate. In this paper, we model evolution with...
We observed near-Sun comet 323P/SOHO for the first time using ground and space telescopes. In late December 2020, object was recovered at Subaru showing no cometary features on its way to perihelion. However, in our postperihelion observations it developed a long narrow tail mimicking disintegrated comet. The ejecta, comprised of least mm-sized dust with power-law size distribution index $3.2 \pm 0.2$, impulsively produced shortly after perihelion passage, during which $\gtrsim$0.1-10%...
Rotation period clustering in prograde/retrograde rotators might indicate the preliminary indication of Slivan state Koronis family as a result YORP effect. We follow general scenario dispersion semimajor axis asteroid members to separate prograde and retrograde family. From available rotation periods obtained from PTF/iPTF, we can not found objects with H grater than 12 mag This could be intermittent collisional process small asteroids (D less ~20 km) which leads astray Yarkovsky drifting....