Publications of the Astronomical Society of the Pacific

Cuevas-Otahola, B.; Mayya, Y. D.; Puerari, I.; Rosa-González, D.

doi: 10.1088/1538-3873/ac477apmid: N/A

The surface brightness profiles (SBPs) of star clusters hold invaluable information on the dynamical state of clusters. The observed SBPs of star clusters, especially that of globular clusters, are in good agreement with the SBPs expected for isothermal spheres containing stars of reduced kinetic energies. However, the SBPs of configurations that satisfy these theoretical criteria cannot be uniquely expressed by analytical formulae, which had hindered the analysis of dynamical state of observed clusters in external galaxies. To counter this shortcoming, it has become a practice to use empirical fitting formulae that best represent the core and halo characteristics of theoretical models. We here present a general purpose code, named nProFit, that allows fitting of the surface brightness profiles of extragalactic star clusters to theoretical star clusters, defined by dynamical models of King and Wilson. In addition, we also incorporated theoretical models that result in power-law surface brightness profiles represented by Elson et al. The code returns the basic size parameters such as core radius, half-light radius and tidal radius, as well as dynamically relevant parameters, such as the volume and surface density profiles, velocity dispersion profile, total mass and the binding energy for a user-fixed mass-to-light ratio. The usefulness of the code in the dynamical study of extragalactic clusters has been already illustrated in Cuevas-Otahola et al. The code, which is python-based at the user end, but makes calls to advanced routines in Pyraf and Fortran, is now available for public use. We provide example scripts and mock clusters in the installation package as guide to users.

Christy, C. T.; Jayasinghe, T.; Stanek, K. Z.; Kochanek, C. S.; Way, Z.; Prieto, J. L.; Shappee, B. J.; Holoien, T. W.-S.; Thompson, T. A.; Schneider, A.

doi: 10.1088/1538-3873/ac44f0pmid: N/A

We present the first results from Citizen ASAS-SN, a citizen science project for the All-Sky Automated Survey for Supernovae (ASAS-SN) hosted on the Zooniverse platform. Citizen ASAS-SN utilizes the newer, deeper, higher cadence ASAS-SN g-band data and tasks volunteers to classify periodic variable star candidates based on their phased light curves. We started from 40,640 new variable candidates from an input list of ∼7.4 million stars with δ < −60° and the volunteers identified 10,420 new discoveries which they classified as 4234 pulsating variables, 3132 rotational variables, 2923 eclipsing binaries, and 131 variables flagged as Unknown. They classified known variable stars with an accuracy of 89% for pulsating variables, 81% for eclipsing binaries, and 49% for rotational variables. We examine user performance, agreement between users, and compare the citizen science classifications with our machine learning classifier updated for the g-band light curves. In general, user activity correlates with higher classification accuracy and higher user agreement. We used the user’s “Junk” classifications to develop an effective machine learning classifier to separate real from false variables, and there is a clear path for using this “Junk” training set to significantly improve our primary machine learning classifier. We also illustrate the value of Citizen ASAS-SN for identifying unusual variables with several examples.

Zhou, Zengxiang; Liang, Jiadong; Duan, Shipeng; Cai, Zeyu; Hu, Hongzhuan; Wang, Jianping; Liu, Zhigang; Cui, Xiangqun; Zhang, Yong; Zhang, Haotong

doi: 10.1088/1538-3873/ac4e1epmid: N/A

In the closed-loop detection system of the LAMOST, the lens of the fiber view camera system must focus the end of the optical fiber to accurately acquire the fiber position. It is difficult to evaluate the fibers image with a very small proportion of the image with the traditional autofocus algorithm, whether it is recognition of the front illuminated by the fiber ceramic ferrules, or the light-emitting spot of the fibers in the black background, that is, the recognition of the back illumination of the fibers. In this paper, we propose an autofocus determination method for the LAMOST closed-loop control under front and back illumination conditions. Under the condition of front illumination, to greatly reduce the calculation time, the system first pre-recognizes the focusing target through the Faster R-CNN and then uses an optimized contrast algorithm to evaluate the image definition of the corrected focusing target ROI. Then, the algorithm is compared with Tenengrad gradient and Laplacian gradient calculations using the Sobel operator and Laplacian operator in OpenCV. The results show that this method takes only one-ninth of the time required by the other methods to obtain the same accuracy. Under the condition of back illumination, we use the average number and average brightness of spot pixels as the evaluation basis of image sharpness. This method can complete the evaluation of image sharpness in the process of spot recognition and provide initial data for the subsequent detection for closed-loop control. The focus accuracy of the camera is of great significance for thousand-fiber metrology, which will have an important influence on the accuracy of astronomical observations. These focusing methods not only play an important role in the closed-loop control of the LAMOST but also apply to the focusing of closed-loop detection systems of other multi-target optical fiber spectral astronomical telescopes.

Yang, Fan; Wei, Xing

doi: 10.1088/1538-3873/ac495apmid: N/A

Observed transit timing variation (TTV) potentially reveals the period decay caused by star-planet tidal interaction which can explain the orbital migration of hot Jupiters. We report the TTV of XO-3b, using TESS observed timings and archival timings. We generate a photometric pipeline to produce light curves from raw TESS images and find the difference between our pipeline and TESS PDC is negligible for timing analysis. TESS timing presents a shift of 17.6 minutes (80σ), earlier than the prediction from the previous ephemeris. The best linear fit for all timings available gives a Bayesian Information Criterion (BIC) value of 439. A quadratic function is a better model with a BIC of 56. The period derivative obtained from a quadratic function is −6.2 × 10−9 ± 2.9 × 10−10 per orbit, indicating an orbital decay timescale 1.4 Myr. We find that the orbital period decay can be well explained by tidal interaction. The “modified tidal quality factor” Qp′would be 1.8 × 104 ± 8 × 102 if we assume the decay is due to the tide in the planet; whereas Q*′would be 1.5 × 105 ± 6 × 103 if tidal dissipation is predominantly in the star. The precession model is another possible origin to explain the observed TTVs. We note that the follow-up observations of occultation timing and radial velocity monitoring are needed for fully discriminating the different models.

Jiang, Ping; Liu, Chengzhi; Yang, Wenbo; Kang, Zhe; Li, Zhenwei

doi: 10.1088/1538-3873/ac4c9dpmid: N/A

Space target detection is the core technology of space surveillance system. The large field of view telescope has strong space detection capabilities, and its realization also faces many challenges. We propose an automatic extraction algorithm for space debris, aiming to automatically extract information about space targets. Our method is mainly divided into three parts. In the first stage, image denoising processing is carried out for various noise interference in the image. The proposed wavelet transform and total variational hybrid filtering algorithm are applied to eliminate noise, which reduces the impact of noise on target detection and greatly retains target information. In the second stage, we propose an improved morphological operator to eliminate uneven background. The third stage uses Hough transform to obtain candidate debris targets. These images were taken during an observation campaign, the observatory is located in Jilin. Experimental results show that the target detection algorithm proposed in this paper can effectively extract space target information and solve the problem of space target detection for large-field telescopes.

Freeze, Brent; Greason, Jeff; Nader, Ronnie; Febres, Jaime Jaramillo; Chaves-Jiminez, Adolfo; Lamontagne, Michel; Thomas, Stephanie; Cassibry, Jason; Fuller, John; Davis, Eric; Conway, Darrel; ,

Douglas, Ewan S.; Debes, John; Mennesson, Bertrand; Nemati, Bijan; Ashcraft, Jaren; Ren, Bin; R. Stapelfeldt, Karl; Savransky, Dmitry; Lewis, Nikole K.; Macintosh, Bruce

doi: 10.1088/1538-3873/ac3f7bpmid: N/A

Exozodiacal dust, warm debris from comets and asteroids in and near the habitable zone of stellar systems, reveals the physical processes that shape planetary systems. Scattered light from this dust is also a source of background flux which must be overcome by future missions to image Earthlike planets. This study quantifies the sensitivity of the Nancy Grace Roman Space Telescope Coronagraph to light scattered by exozodi, the zodiacal dust around other stars. Using a sample of 149 nearby stars, previously selected for optimum detection of habitable exoplanets by space observatories, we find the maximum number of exozodiacal disks with observable inner habitable zone boundaries is six and the number of observable outer habitable boundaries is 74. One zodi was defined as the visible-light surface brightness of 22 mV arcsec−2 around a solar-mass star, approximating the scattered light brightness in visible light at the Earth-equivalent insolation. In the speckle limited case, where the signal-to-noise ratio is limited by speckle temporal stability rather than shot noise, the median 5σ sensitivity to habitable zone exozodi is 12 zodi per resolution element. This estimate is calculated at the inner-working angle of the coronagraph, for the current best estimate performance, neglecting margins on the uncertainty in instrument performance and including a post-processing speckle suppression factor. For an log-norm distribution of exozodi levels with a median exozodi of 3× the solar zodi, we find that the Roman Coronagraph would be able to make 5σ detections of exozodiacal disks in scattered light from 13 systems with a 95% confidence interval spanning 7–20 systems. This sensitivity allows Roman Coronagraph to complement ground-based measurements of exozodiacal thermal emission and constrain dust albedos. Optimized post-processing and detection of extended sources in multiple resolution elements is expected to further improve this unprecedented sensitivity to light scattered by exozodiacal dust.

Kim, Y.-L.; Rigault, M.; Neill, J. D.; Briday, M.; Copin, Y.; Lezmy, J.; Nicolas, N.; Riddle, R.; Sharma, Y.; Smith, M.; Sollerman, J.; Walters, R.

doi: 10.1088/1538-3873/ac50a0pmid: N/A

Currently time-domain astronomy can scan the entire sky on a daily basis, discovering thousands of interesting transients every night. Classifying the ever-increasing number of new transients is one of the main challenges for the astronomical community. One solution that addresses this issue is the robotically controlled Spectral Energy Distribution Machine (SEDM) which supports the Zwicky Transient Facility (ZTF). SEDM with its pipeline pysedm demonstrates that real-time robotic spectroscopic classification is feasible. In an effort to improve the quality of the current SEDM data, we present here two new modules, byecr and contsep. The first removes contamination from cosmic rays, and the second removes contamination from non-target light. These new modules are part of the automated pysedm pipeline and fully integrated with the whole process. Employing byecr and contsep modules together automatically extracts more spectra than the current pysedm pipeline. Using SNID classification results, the new modules show an improvement in the classification rate and accuracy of 2.8% and 1.7%, respectively, while the strength of the cross-correlation remains the same. Improvements to the SEDM astrometry would further boost the improvement of the contsep module. This kind of robotic follow-up with a fully automated pipeline has the potential to provide the spectroscopic classifications for the transients discovered by ZTF and also by the Rubin Observatory’s Legacy Survey of Space and Time.

Kwitter, Karen B.; Henry, R. B. C.

doi: 10.1088/1538-3873/ac32b1pmid: N/A

In this review/tutorial we explore planetary nebulae as a stage in the evolution of low-to-intermediate-mass stars, as major contributors to the mass and chemical enrichment of the interstellar medium, and as astrophysical laboratories. We discuss many observed properties of planetary nebulae, placing particular emphasis on element abundance determinations and comparisons with theoretical predictions. Dust and molecules associated with planetary nebulae are considered as well. We then examine distances, binarity, and planetary nebula morphology and evolution. We end with mention of some of the advances that will be enabled by future observing capabilities.

Willott, Chris J.; Doyon, René; Albert, Loic; Brammer, Gabriel B.; Dixon, William V.; Muzic, Koraljka; Ravindranath, Swara; Scholz, Aleks; Abraham, Roberto; Artigau, Étienne; Bradač, Maruša; Goudfrooij, Paul; Hutchings, John B.; Iyer, Kartheik G.; Jayawardhana, Ray; LaMassa, Stephanie; Martis, Nicholas; Meyer, Michael R.; Morishita, Takahiro;