Pub Date : 2023-12-21DOI: 10.1088/1538-3873/ad0977
E. O. Ofek, Y. Shvartzvald, A. Sharon, C. Tishler, D. Elhanati, N. Segev, S. Ben-Ami, G. Nir, E. Segre, Y. Sofer-Rimalt, A. Blumenzweig, N. L. Strotjohann, D. Polishook, A. Krassilchtchikov, A. Zenin, V. Fallah Ramazani, S. Weimann, S. Garrappa, Y. Shanni, P. Chen, E. Zimmerman
The Large Array Survey Telescope (LAST) is a wide-field telescope designed to explore the variable and transient sky with a high cadence and to be a test-bed for cost-effective telescope design. A LAST node is composed of 48 (32 already deployed), 28 cm f/2.2 telescopes. A single telescope has a 7.4 deg2 field of view and reaches a 5σ limiting magnitude of 19.6 (21.0) in 20 (20 × 20) s (filter-less), while the entire system provides a 355 deg2 field of view. The basic strategy of LAST is to obtain multiple 20 s consecutive exposures of each field (a visit). Each telescope carries a 61 Mpix camera, and the system produces, on average, about 2.2 Gbit s−1. This high data rate is analyzed in near real-time at the observatory site, using limited computing resources (about 700 cores). Given this high data rate, we have developed a new, efficient data reduction and analysis pipeline. The LAST data pipeline includes two major parts: (i) Processing and calibration of single images, followed by a coaddition of the visit’s exposures. (ii) Building the reference images and performing image subtraction and transient detection. Here we describe in detail the first part of the pipeline. Among the products of this pipeline are photometrically and astrometrically calibrated single and coadded images, 32 bit mask images marking a wide variety of problems and states of each pixel, source catalogs built from individual and coadded images, Point-Spread Function photometry, merged source catalogs, proper motion and variability indicators, minor planets detection, calibrated light curves, and matching with external catalogs. The entire pipeline code is made public. Finally, we demonstrate the pipeline performance on real data taken by LAST.
{"title":"The Large Array Survey Telescope—Pipeline. I. Basic Image Reduction and Visit Coaddition","authors":"E. O. Ofek, Y. Shvartzvald, A. Sharon, C. Tishler, D. Elhanati, N. Segev, S. Ben-Ami, G. Nir, E. Segre, Y. Sofer-Rimalt, A. Blumenzweig, N. L. Strotjohann, D. Polishook, A. Krassilchtchikov, A. Zenin, V. Fallah Ramazani, S. Weimann, S. Garrappa, Y. Shanni, P. Chen, E. Zimmerman","doi":"10.1088/1538-3873/ad0977","DOIUrl":"https://doi.org/10.1088/1538-3873/ad0977","url":null,"abstract":"The Large Array Survey Telescope (LAST) is a wide-field telescope designed to explore the variable and transient sky with a high cadence and to be a test-bed for cost-effective telescope design. A LAST node is composed of 48 (32 already deployed), 28 cm <italic toggle=\"yes\">f</italic>/2.2 telescopes. A single telescope has a 7.4 deg<sup>2</sup> field of view and reaches a 5<italic toggle=\"yes\">σ</italic> limiting magnitude of 19.6 (21.0) in 20 (20 × 20) s (filter-less), while the entire system provides a 355 deg<sup>2</sup> field of view. The basic strategy of LAST is to obtain multiple 20 s consecutive exposures of each field (a visit). Each telescope carries a 61 Mpix camera, and the system produces, on average, about 2.2 Gbit s<sup>−1</sup>. This high data rate is analyzed in near real-time at the observatory site, using limited computing resources (about 700 cores). Given this high data rate, we have developed a new, efficient data reduction and analysis pipeline. The LAST data pipeline includes two major parts: (i) Processing and calibration of single images, followed by a coaddition of the visit’s exposures. (ii) Building the reference images and performing image subtraction and transient detection. Here we describe in detail the first part of the pipeline. Among the products of this pipeline are photometrically and astrometrically calibrated single and coadded images, 32 bit mask images marking a wide variety of problems and states of each pixel, source catalogs built from individual and coadded images, Point-Spread Function photometry, merged source catalogs, proper motion and variability indicators, minor planets detection, calibrated light curves, and matching with external catalogs. The entire pipeline code is made public. Finally, we demonstrate the pipeline performance on real data taken by LAST.","PeriodicalId":20820,"journal":{"name":"Publications of the Astronomical Society of the Pacific","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139053845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-12DOI: 10.1088/1538-3873/ad0e7e
Shichao Wu, Yingbo Liu, Lei Yang, Xiaoying Liu, Xingxu Li, Yongyuan Xiang, Yunyu Gong
Rapid and proficient data retrieval is an essential component of modern astronomical research. In this paper, we address the challenge of retrieving astronomical image content by leveraging state-of-the-art deep learning techniques. We have designed a retrieval model, HybridVR, that integrates the capabilities of the deep learning models ResNet50 and VGG16 and have used it to extract key features of solar activity and solar environmental characteristics from observed images. This model enables efficient image matching and allows for content-based image retrieval (CBIR). Experimental results demonstrate that the model can achieve up to 98% similarity during CBIR while exhibiting adaptability and scalability. Our work has implications for astronomical research, data management, and education, and it can contribute to optimizing the utilization of astronomical image data. It also serves as a useful example of the application of deep learning technology in the field of astronomy.
{"title":"AstroSer: Leveraging Deep Learning for Efficient Content-based Retrieval in Massive Solar-observation Images","authors":"Shichao Wu, Yingbo Liu, Lei Yang, Xiaoying Liu, Xingxu Li, Yongyuan Xiang, Yunyu Gong","doi":"10.1088/1538-3873/ad0e7e","DOIUrl":"https://doi.org/10.1088/1538-3873/ad0e7e","url":null,"abstract":"Rapid and proficient data retrieval is an essential component of modern astronomical research. In this paper, we address the challenge of retrieving astronomical image content by leveraging state-of-the-art deep learning techniques. We have designed a retrieval model, HybridVR, that integrates the capabilities of the deep learning models ResNet50 and VGG16 and have used it to extract key features of solar activity and solar environmental characteristics from observed images. This model enables efficient image matching and allows for content-based image retrieval (CBIR). Experimental results demonstrate that the model can achieve up to 98% similarity during CBIR while exhibiting adaptability and scalability. Our work has implications for astronomical research, data management, and education, and it can contribute to optimizing the utilization of astronomical image data. It also serves as a useful example of the application of deep learning technology in the field of astronomy.","PeriodicalId":20820,"journal":{"name":"Publications of the Astronomical Society of the Pacific","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138684285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-08DOI: 10.1088/1538-3873/ad0f9a
A. Farkas-Takács, Csaba Kiss
Kuiper Belt objects are thought to be formed at least a few million years after the formation of calcium–aluminum-rich inclusions (CAIs), at a time when the 26Al isotope—the major source of radiogenic heat in the early solar system—had significantly depleted. The internal structure of these objects is highly dependent on any additional source that can produce extra heat in addition to that produced by the remaining, long-lasting radioactive isotopes. In this paper, we explore how serpentinization, the hydration of silicate minerals, can contribute to the heat budget and to what extent it can modify the internal structure of large Kuiper Belt objects. We find that the extent of restructuring depends very strongly on the start time of the formation process, the size of the object, and the starting ice-to-rock ratio. Serpentinization is able to restructure most of the interior of all objects in the whole size range (400–1200 km) and ice-to-rock ratio range investigated if the process starts early, ∼3 Myr after CAI formation, potentially leading to a predominantly serpentine core much earlier than previously thought (≤5 Myr versus several tens of million years). While the ratio of serpentinized material gradually decreases with the increasing formation time, the increasing ice-to-rock ratio, and the increasing start time of planetesimal formation in the outer solar system, in the case of the largest objects a significant part of the interior will be serpentinized even if the formation starts relatively late, ∼5 Myr after CAI formation. Therefore it is feasible that the interior of planetesimals may have contained a significant amount of serpentine, and in some cases, it could have been a dominant constituent, at the time of satellite-forming impacts.
{"title":"The Impact of Serpentinization on the Initial Conditions of Satellite Forming Collisions of Large Kuiper Belt Objects","authors":"A. Farkas-Takács, Csaba Kiss","doi":"10.1088/1538-3873/ad0f9a","DOIUrl":"https://doi.org/10.1088/1538-3873/ad0f9a","url":null,"abstract":"Kuiper Belt objects are thought to be formed at least a few million years after the formation of calcium–aluminum-rich inclusions (CAIs), at a time when the 26Al isotope—the major source of radiogenic heat in the early solar system—had significantly depleted. The internal structure of these objects is highly dependent on any additional source that can produce extra heat in addition to that produced by the remaining, long-lasting radioactive isotopes. In this paper, we explore how serpentinization, the hydration of silicate minerals, can contribute to the heat budget and to what extent it can modify the internal structure of large Kuiper Belt objects. We find that the extent of restructuring depends very strongly on the start time of the formation process, the size of the object, and the starting ice-to-rock ratio. Serpentinization is able to restructure most of the interior of all objects in the whole size range (400–1200 km) and ice-to-rock ratio range investigated if the process starts early, ∼3 Myr after CAI formation, potentially leading to a predominantly serpentine core much earlier than previously thought (≤5 Myr versus several tens of million years). While the ratio of serpentinized material gradually decreases with the increasing formation time, the increasing ice-to-rock ratio, and the increasing start time of planetesimal formation in the outer solar system, in the case of the largest objects a significant part of the interior will be serpentinized even if the formation starts relatively late, ∼5 Myr after CAI formation. Therefore it is feasible that the interior of planetesimals may have contained a significant amount of serpentine, and in some cases, it could have been a dominant constituent, at the time of satellite-forming impacts.","PeriodicalId":20820,"journal":{"name":"Publications of the Astronomical Society of the Pacific","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138588727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-04DOI: 10.1088/1538-3873/ad0b30
Ryan A. Rubenzahl, Samuel Halverson, Josh Walawender, Grant M. Hill, Andrew W. Howard, Matthew Brown, Evan Ida, Jerez Tehero, Benjamin J. Fulton, Steven R. Gibson, Marc Kassis, Brett Smith, Truman Wold, Joel Payne
Extreme precision radial velocity (EPRV) measurements contend with internal noise (instrumental systematics) and external noise (intrinsic stellar variability) on the road to 10 cm s−1 “exo-Earth” sensitivity. Both of these noise sources are well-probed using “Sun-as-a-star” RVs and cross-instrument comparisons. We built the Solar Calibrator (SoCal), an autonomous system that feeds stable, disk-integrated sunlight to the recently commissioned Keck Planet Finder (KPF) at the W. M. Keck Observatory. With SoCal, KPF acquires signal-to-noise ratio (S/N) ∼ 1200, R = 98,000 optical (445–870 nm) spectra of the Sun in 5 s exposures at unprecedented cadence for an EPRV facility using KPF’s fast readout mode (<16 s between exposures). Daily autonomous operation is achieved by defining an operations loop using state machine logic. Data affected by clouds are automatically flagged using a reliable quality control metric derived from simultaneous irradiance measurements. Comparing solar data across the growing global network of EPRV spectrographs with solar feeds will allow EPRV teams to disentangle internal and external noise sources and benchmark spectrograph performance. To facilitate this, all SoCal data products are immediately available to the public on the Keck Observatory Archive. We compared SoCal RVs to contemporaneous RVs from NEID, the only other immediately public EPRV solar data set. We find agreement at the 30–40 cm s−1 level on timescales of several hours, which is comparable to the combined photon-limited precision. Data from SoCal were also used to assess a detector problem and wavelength calibration inaccuracies associated with KPF during early operations. Long-term SoCal operations will collect upwards of 1000 solar spectra per six-hour day using KPF’s fast readout mode, enabling stellar activity studies at high S/N on our nearest solar-type star.
极精密径向速度（EPRV）测量在通往 10 cm s-1 "外地球 "灵敏度的道路上要与内部噪声（仪器系统性）和外部噪声（恒星内在变异性）作斗争。利用 "太阳即恒星 "的 RV 和跨仪器比较可以很好地探测这两种噪声源。我们建造了太阳校准器（SoCal），它是一个自主系统，向 W. M. 凯克天文台最近投入使用的凯克行星探测器（KPF）提供稳定的磁盘积分太阳光。利用SoCal，KPF以5秒的曝光时间获取信噪比（S/N）∼1200，R = 98,000的太阳光学（445-870 nm）光谱，对于使用KPF的快速读出模式（曝光间隔16秒）的EPRV设备来说，这种速度是前所未有的。通过使用状态机逻辑定义操作循环，实现了每日自主运行。利用同步辐照度测量得出的可靠质量控制指标，受云层影响的数据会被自动标记。在不断扩大的 EPRV 光谱仪全球网络中，通过太阳馈源对太阳数据进行比较，将使 EPRV 团队能够区分内部和外部噪声源，并对光谱仪的性能进行基准测试。为了便于进行这项工作，所有 SoCal 数据产品都可以立即在凯克天文台档案库中向公众提供。我们将 SoCal RV 与 NEID 的同期 RV 进行了比较，后者是唯一一个立即公开的 EPRV 太阳数据集。我们发现在 30-40 cm s-1 的水平上，两者在几个小时的时间尺度上是一致的，这与光子限制的综合精度相当。来自 SoCal 的数据还被用来评估早期运行期间与 KPF 有关的探测器问题和波长校准误差。SoCal 的长期运行将利用 KPF 的快速读出模式，每天 6 小时收集多达 1000 多条太阳光谱，从而能够对离我们最近的太阳型恒星进行高信噪比的恒星活动研究。
{"title":"Staring at the Sun with the Keck Planet Finder: An Autonomous Solar Calibrator for High Signal-to-noise Sun-as-a-star Spectra","authors":"Ryan A. Rubenzahl, Samuel Halverson, Josh Walawender, Grant M. Hill, Andrew W. Howard, Matthew Brown, Evan Ida, Jerez Tehero, Benjamin J. Fulton, Steven R. Gibson, Marc Kassis, Brett Smith, Truman Wold, Joel Payne","doi":"10.1088/1538-3873/ad0b30","DOIUrl":"https://doi.org/10.1088/1538-3873/ad0b30","url":null,"abstract":"Extreme precision radial velocity (EPRV) measurements contend with internal noise (instrumental systematics) and external noise (intrinsic stellar variability) on the road to 10 cm s<sup>−1</sup> “exo-Earth” sensitivity. Both of these noise sources are well-probed using “Sun-as-a-star” RVs and cross-instrument comparisons. We built the Solar Calibrator (SoCal), an autonomous system that feeds stable, disk-integrated sunlight to the recently commissioned Keck Planet Finder (KPF) at the W. M. Keck Observatory. With SoCal, KPF acquires signal-to-noise ratio (S/N) ∼ 1200, <italic toggle=\"yes\">R</italic> = 98,000 optical (445–870 nm) spectra of the Sun in 5 s exposures at unprecedented cadence for an EPRV facility using KPF’s fast readout mode (<16 s between exposures). Daily autonomous operation is achieved by defining an operations loop using state machine logic. Data affected by clouds are automatically flagged using a reliable quality control metric derived from simultaneous irradiance measurements. Comparing solar data across the growing global network of EPRV spectrographs with solar feeds will allow EPRV teams to disentangle internal and external noise sources and benchmark spectrograph performance. To facilitate this, all SoCal data products are immediately available to the public on the Keck Observatory Archive. We compared SoCal RVs to contemporaneous RVs from NEID, the only other immediately public EPRV solar data set. We find agreement at the 30–40 cm s<sup>−1</sup> level on timescales of several hours, which is comparable to the combined photon-limited precision. Data from SoCal were also used to assess a detector problem and wavelength calibration inaccuracies associated with KPF during early operations. Long-term SoCal operations will collect upwards of 1000 solar spectra per six-hour day using KPF’s fast readout mode, enabling stellar activity studies at high S/N on our nearest solar-type star.","PeriodicalId":20820,"journal":{"name":"Publications of the Astronomical Society of the Pacific","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138684481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.1088/1538-3873/ad1118
H. Abt, J. Guzik, J. Jackiewicz
Paddock’s 1927–1935 radial velocities of α Cygni (Deneb) show semi-regular pulsations with a dominant period of about 12 days. Lucy found many periods of lesser amplitude. In Paddock’s data and subsequent 1956 data from Abt, after the large-amplitude pulsations seemed to damp down, abruptly new sets of pulsations started within a fraction of a day. Five of those resumptions occurred with intervals averaging 72.4 ± 0.3 days. These resumptions seem to start at any phase during the pulsations. We are unaware of this behavior in any other star. We also find evidence of this behavior in the 1977–1982 radial velocity data of Parthasarathy & Lambert and the 1997–2001 photometry/radial velocity data of Richardson et al., as well as in photometric data from the NASA Transiting Exoplanet Survey Satellite (TESS) spacecraft and ground-based visual observations in the AAVSO International Database. The ground-based data have too infrequent sampling intervals to confirm the ∼70-day resumption intervals or to pinpoint the day and phase of abrupt amplitude increase. The TESS data, with 2-minute cadence, shows one instance of pulsation resumption, but does not have a long enough time series to confirm a 70-day interval. Without any evidence for duplicity, we cannot explain this behavior as being due to a companion in a highly eccentric orbit. α Cygni is one of the Luminous Blue Variables (supergiants) and these resumptions may be related to the microvariations produced in convective layers below their atmospheres, pulsation-driven shocks and rarefactions, or pulsation-convection interactions. We encourage further observations by ground-based observers and using the TESS spacecraft to confirm the ∼70-day resumption interval and lack of correlation with pulsation phase in both radial velocity and light curve data.
{"title":"The Abrupt Resumptions of Pulsations in α Cygni (Deneb)","authors":"H. Abt, J. Guzik, J. Jackiewicz","doi":"10.1088/1538-3873/ad1118","DOIUrl":"https://doi.org/10.1088/1538-3873/ad1118","url":null,"abstract":"Paddock’s 1927–1935 radial velocities of α Cygni (Deneb) show semi-regular pulsations with a dominant period of about 12 days. Lucy found many periods of lesser amplitude. In Paddock’s data and subsequent 1956 data from Abt, after the large-amplitude pulsations seemed to damp down, abruptly new sets of pulsations started within a fraction of a day. Five of those resumptions occurred with intervals averaging 72.4 ± 0.3 days. These resumptions seem to start at any phase during the pulsations. We are unaware of this behavior in any other star. We also find evidence of this behavior in the 1977–1982 radial velocity data of Parthasarathy & Lambert and the 1997–2001 photometry/radial velocity data of Richardson et al., as well as in photometric data from the NASA Transiting Exoplanet Survey Satellite (TESS) spacecraft and ground-based visual observations in the AAVSO International Database. The ground-based data have too infrequent sampling intervals to confirm the ∼70-day resumption intervals or to pinpoint the day and phase of abrupt amplitude increase. The TESS data, with 2-minute cadence, shows one instance of pulsation resumption, but does not have a long enough time series to confirm a 70-day interval. Without any evidence for duplicity, we cannot explain this behavior as being due to a companion in a highly eccentric orbit. α Cygni is one of the Luminous Blue Variables (supergiants) and these resumptions may be related to the microvariations produced in convective layers below their atmospheres, pulsation-driven shocks and rarefactions, or pulsation-convection interactions. We encourage further observations by ground-based observers and using the TESS spacecraft to confirm the ∼70-day resumption interval and lack of correlation with pulsation phase in both radial velocity and light curve data.","PeriodicalId":20820,"journal":{"name":"Publications of the Astronomical Society of the Pacific","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138993791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.1088/1538-3873/ad0789
D. Monasterio, Sebastian Jorquera, F. Curotto, Camilo Espinoza, R. Finger, L. Bronfman
In this work we present a novel digital technique, that allows local oscillator (LO) noise cancellation using a digital power combiner in a balanced mixer receiver architecture. A theoretical analysis of the noise cancellation using the proposed technique is derived and a proof of concept experiment is made for the Ku-Band. This experiment includes the design and construction of a custom balanced mixer and an artificial noise source. Experimental results show a consistent noise temperature reduction in comparison with a full analog mixer, and in some cases reaching noise temperature levels similar to the receiver operating without the artificial LO noise.
{"title":"A Proof of Concept Balanced Mixer with the use of a Digital IF Power Combiner to Improve LO Noise Rejection","authors":"D. Monasterio, Sebastian Jorquera, F. Curotto, Camilo Espinoza, R. Finger, L. Bronfman","doi":"10.1088/1538-3873/ad0789","DOIUrl":"https://doi.org/10.1088/1538-3873/ad0789","url":null,"abstract":"In this work we present a novel digital technique, that allows local oscillator (LO) noise cancellation using a digital power combiner in a balanced mixer receiver architecture. A theoretical analysis of the noise cancellation using the proposed technique is derived and a proof of concept experiment is made for the Ku-Band. This experiment includes the design and construction of a custom balanced mixer and an artificial noise source. Experimental results show a consistent noise temperature reduction in comparison with a full analog mixer, and in some cases reaching noise temperature levels similar to the receiver operating without the artificial LO noise.","PeriodicalId":20820,"journal":{"name":"Publications of the Astronomical Society of the Pacific","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138615499","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.1088/1538-3873/ad0a73
Johnny H. Esteves, Yousuke Utsumi, Adam Snyder, Theo Schutt, Alex Broughton, Bahrudin Trbalic, Sidney Mau, Andrew Rasmussen, Andrés A. Plazas Malagón, Andrew Bradshaw, Stuart Marshall, Seth Digel, James Chiang, Eli Rykoff, Chris Waters, Marcelle Soares-Santos, Aaron Roodman
The Vera C. Rubin Observatory’s LSST Camera (LSSTCam) pixel response has been characterized using laboratory measurements with a grid of artificial stars. We quantify the contributions to photometry, centroid, point-spread function size, and shape measurement errors due to small anomalies in the LSSTCam CCDs. The main sources of those anomalies are quantum efficiency variations and pixel area variations induced by the amplifier segmentation boundaries and “tree-rings”—circular variations in silicon doping concentration. This laboratory study using artificial stars projected on the sensors shows overall small effects. The residual effects on point-spread function (PSF) size and shape are below 0.1%, meeting the ten-year LSST survey science requirements. However, the CCD mid-line presents distortions that can have a moderate impact on PSF measurements. This feature can be avoided by masking the affected regions. Effects of tree-rings are observed on centroids and PSFs of the artificial stars and the nature of the effect is confirmed by a study of the flat-field response. Nevertheless, further studies of the full-focal plane with stellar data should more completely probe variations and might reveal new features, e.g., wavelength-dependent effects. The results of this study can be used as a guide for the on-sky operation of LSSTCam.
Vera C. Rubin天文台的LSST相机（LSSTCam）的像素响应是通过实验室测量人造恒星网格来确定的。我们量化了 LSSTCam CCD 的微小异常对光度、中心点、点散布函数大小和形状测量误差的影响。这些异常的主要来源是放大器分割边界和 "树环"（硅掺杂浓度的圆形变化）引起的量子效率变化和像素面积变化。这项使用投射到传感器上的人造星进行的实验室研究显示，总体影响较小。对点散射函数（PSF）大小和形状的残余影响低于 0.1%，符合 LSST 十年巡天科学要求。不过，CCD 中线的扭曲会对 PSF 测量产生一定影响。可以通过遮挡受影响区域来避免这一问题。在人造星的中心点和 PSF 上观测到了树环效应，对平场响应的研究证实了这种效应的性质。不过，利用恒星数据对全焦面的进一步研究应该能更全面地探查各种变化，并可能揭示出新的特征，例如与波长有关的效应。本研究的结果可作为 LSSTCam 在天空中运行的指导。
{"title":"Photometry, Centroid and Point-spread Function Measurements in the LSST Camera Focal Plane Using Artificial Stars","authors":"Johnny H. Esteves, Yousuke Utsumi, Adam Snyder, Theo Schutt, Alex Broughton, Bahrudin Trbalic, Sidney Mau, Andrew Rasmussen, Andrés A. Plazas Malagón, Andrew Bradshaw, Stuart Marshall, Seth Digel, James Chiang, Eli Rykoff, Chris Waters, Marcelle Soares-Santos, Aaron Roodman","doi":"10.1088/1538-3873/ad0a73","DOIUrl":"https://doi.org/10.1088/1538-3873/ad0a73","url":null,"abstract":"The Vera C. Rubin Observatory’s LSST Camera (LSSTCam) pixel response has been characterized using laboratory measurements with a grid of artificial stars. We quantify the contributions to photometry, centroid, point-spread function size, and shape measurement errors due to small anomalies in the LSSTCam CCDs. The main sources of those anomalies are quantum efficiency variations and pixel area variations induced by the amplifier segmentation boundaries and “tree-rings”—circular variations in silicon doping concentration. This laboratory study using artificial stars projected on the sensors shows overall small effects. The residual effects on point-spread function (PSF) size and shape are below 0.1%, meeting the ten-year LSST survey science requirements. However, the CCD mid-line presents distortions that can have a moderate impact on PSF measurements. This feature can be avoided by masking the affected regions. Effects of tree-rings are observed on centroids and PSFs of the artificial stars and the nature of the effect is confirmed by a study of the flat-field response. Nevertheless, further studies of the full-focal plane with stellar data should more completely probe variations and might reveal new features, e.g., wavelength-dependent effects. The results of this study can be used as a guide for the on-sky operation of LSSTCam.","PeriodicalId":20820,"journal":{"name":"Publications of the Astronomical Society of the Pacific","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138684133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.1088/1538-3873/ad0b31
R. Szakáts, Csaba Kiss
The largest bodies—or dwarf planets—constitute a different class among Kuiper Belt objects and are characterized by bright surfaces and volatile compositions remarkably different from that of smaller trans-Neptunian objects. These compositional differences are also reflected in the visible and near-infrared colors, and variegations across the surface can cause broadband colors to vary with rotational phase. Here we present near-infrared J and H-band observations of the dwarf planet (136199) Eris obtained with the GuideDog camera of the Infrared Telescope Facility. These measurements show that—as suspected from previous J − H measurements—the J − H color of Eris indeed varies with rotational phase. This suggests notable surface heterogenity in chemical composition and/or other material properties despite the otherwise quite homogeneous, high albedo surface, characterized by a very low amplitude visible range light curve. While variations in the grain size of the dominant CH4 may in general be responsible for notable changes in the J − H color, in the current observing geometry of the system it can only partially explain the observed J − H variation.
{"title":"Rotational Phase Dependent J − H Colour of the Dwarf Planet Eris","authors":"R. Szakáts, Csaba Kiss","doi":"10.1088/1538-3873/ad0b31","DOIUrl":"https://doi.org/10.1088/1538-3873/ad0b31","url":null,"abstract":"The largest bodies—or dwarf planets—constitute a different class among Kuiper Belt objects and are characterized by bright surfaces and volatile compositions remarkably different from that of smaller trans-Neptunian objects. These compositional differences are also reflected in the visible and near-infrared colors, and variegations across the surface can cause broadband colors to vary with rotational phase. Here we present near-infrared J and H-band observations of the dwarf planet (136199) Eris obtained with the GuideDog camera of the Infrared Telescope Facility. These measurements show that—as suspected from previous J − H measurements—the J − H color of Eris indeed varies with rotational phase. This suggests notable surface heterogenity in chemical composition and/or other material properties despite the otherwise quite homogeneous, high albedo surface, characterized by a very low amplitude visible range light curve. While variations in the grain size of the dominant CH4 may in general be responsible for notable changes in the J − H color, in the current observing geometry of the system it can only partially explain the observed J − H variation.","PeriodicalId":20820,"journal":{"name":"Publications of the Astronomical Society of the Pacific","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138610794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.1088/1538-3873/ad0a72
Ramya M Anche, Ewan Douglas, Kian Milani, Jaren Ashcraft, Maxwell A. Millar-Blanchaer, John H Debes, Julien Milli, Justin Hom
The Nancy Grace Roman Space Telescope Coronagraph Instrument will enable the polarimetric imaging of debris disks and inner dust belts in the optical and near-infrared wavelengths, in addition to the high-contrast polarimetric imaging and spectroscopy of exoplanets. The Coronagraph uses two Wollaston prisms to produce four orthogonally polarized images and is expected to measure the polarization fraction with measurement errors <3% per spatial resolution element. To simulate the polarization observations through the Hybrid Lyot Coronagraph (HLC) and Shaped Pupil Coronagraph (SPC), we model disk scattering, the coronagraphic point-response function, detector noise, speckles, jitter, and instrumental polarization and calculate the Stokes parameters. To illustrate the potential for discovery and a better understanding of known systems with both the HLC and SPC modes, we model the debris disks around Epsilon Eridani and HR 4796A, respectively. For Epsilon Eridani, using astrosilicates with 0.37 ± 0.01 as the peak input polarization fraction in one resolution element, we recover the peak disk polarization fraction of 0.33 ± 0.01. Similarly, for HR 4796A, for a peak input polarization fraction of 0.92 ± 0.01, we obtain the peak output polarization fraction as 0.80 ± 0.03. The Coronagraph design meets the required precision, and forward modeling is needed to accurately estimate the polarization fraction.
{"title":"Simulation of High-contrast Polarimetric Observations of Debris Disks with the Roman Coronagraph Instrument","authors":"Ramya M Anche, Ewan Douglas, Kian Milani, Jaren Ashcraft, Maxwell A. Millar-Blanchaer, John H Debes, Julien Milli, Justin Hom","doi":"10.1088/1538-3873/ad0a72","DOIUrl":"https://doi.org/10.1088/1538-3873/ad0a72","url":null,"abstract":"The Nancy Grace Roman Space Telescope Coronagraph Instrument will enable the polarimetric imaging of debris disks and inner dust belts in the optical and near-infrared wavelengths, in addition to the high-contrast polarimetric imaging and spectroscopy of exoplanets. The Coronagraph uses two Wollaston prisms to produce four orthogonally polarized images and is expected to measure the polarization fraction with measurement errors <3% per spatial resolution element. To simulate the polarization observations through the Hybrid Lyot Coronagraph (HLC) and Shaped Pupil Coronagraph (SPC), we model disk scattering, the coronagraphic point-response function, detector noise, speckles, jitter, and instrumental polarization and calculate the Stokes parameters. To illustrate the potential for discovery and a better understanding of known systems with both the HLC and SPC modes, we model the debris disks around Epsilon Eridani and HR 4796A, respectively. For Epsilon Eridani, using astrosilicates with 0.37 ± 0.01 as the peak input polarization fraction in one resolution element, we recover the peak disk polarization fraction of 0.33 ± 0.01. Similarly, for HR 4796A, for a peak input polarization fraction of 0.92 ± 0.01, we obtain the peak output polarization fraction as 0.80 ± 0.03. The Coronagraph design meets the required precision, and forward modeling is needed to accurately estimate the polarization fraction.","PeriodicalId":20820,"journal":{"name":"Publications of the Astronomical Society of the Pacific","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138684292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-29DOI: 10.1088/1538-3873/ad0a04
Ma Long, Du Jiangbin, Zhao Jiayao, Wang Xuhao, Peng Yangfan
The existing astronomical image restoration and superresolution reconstruction methods have problems such as low efficiency and poor results when dealing with images possessing large fields of view. Furthermore, these methods typically only handle fixed-size images and require step-by-step processing, which is inconvenient. In this paper, a neural network called Res&RecNet is proposed for the restoration and superresolution reconstruction of astronomical images with large fields of view for direct imaging instruments. This network performs feature extraction, feature correction, and progressive generation to achieve image restoration and superresolution reconstruction. The network is constructed using fully convolutional layers, allowing it to handle images of any size. The network can be trained using small samples and can perform image restoration and superresolution reconstruction in an end-to-end manner, resulting in high efficiency. Experimental results show that the network is highly effective in terms of processing astronomical images with complex scenes, generating image restoration results that improve the peak signal-to-noise ratio (PSNR) and structural similarity index measure (SSIM) by 4.69 (dB)/0.073 and superresolution reconstruction results that improve the PSNR and SSIM by 1.97 (dB)/0.077 over those of the best existing algorithms, respectively.
{"title":"Large-field Astronomical Image Restoration and Superresolution Reconstruction using Deep Learning","authors":"Ma Long, Du Jiangbin, Zhao Jiayao, Wang Xuhao, Peng Yangfan","doi":"10.1088/1538-3873/ad0a04","DOIUrl":"https://doi.org/10.1088/1538-3873/ad0a04","url":null,"abstract":"The existing astronomical image restoration and superresolution reconstruction methods have problems such as low efficiency and poor results when dealing with images possessing large fields of view. Furthermore, these methods typically only handle fixed-size images and require step-by-step processing, which is inconvenient. In this paper, a neural network called Res&RecNet is proposed for the restoration and superresolution reconstruction of astronomical images with large fields of view for direct imaging instruments. This network performs feature extraction, feature correction, and progressive generation to achieve image restoration and superresolution reconstruction. The network is constructed using fully convolutional layers, allowing it to handle images of any size. The network can be trained using small samples and can perform image restoration and superresolution reconstruction in an end-to-end manner, resulting in high efficiency. Experimental results show that the network is highly effective in terms of processing astronomical images with complex scenes, generating image restoration results that improve the peak signal-to-noise ratio (PSNR) and structural similarity index measure (SSIM) by 4.69 (dB)/0.073 and superresolution reconstruction results that improve the PSNR and SSIM by 1.97 (dB)/0.077 over those of the best existing algorithms, respectively.","PeriodicalId":20820,"journal":{"name":"Publications of the Astronomical Society of the Pacific","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138684131","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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