Recent discoveries of multiple long-period pulsars (periods ${sim}10,$s or larger) are starting to challenge the conventional notion that coherent radio emission cannot be produced by objects that are below the many theorised death lines. Many of the past pulsar surveys and software have been prone to selection effects that restricted their sensitivities towards long-period and sporadically emitting objects. Pulsar surveys using new-generation low-frequency facilities are starting to employ longer dwell times, which makes them significantly more sensitive in detecting long-period or nulling pulsars. There have also been software advancements to aid more sensitive searches towards long-period objects. Furthermore, recent discoveries suggest that nulling may be a key aspect of the long-period pulsar population. We simulate both long-period and nulling pulsar signals, using the Southern-sky MWA Rapid Two-meter (SMART) survey data as reference and explore the detection efficacy of popular search methods such as the fast Fourier transform (FFT), fast-folding algorithm (FFA) and single pulse search (SPS). For FFT-based search and SPS, we make use of the PRESTO implementation, and for FFA we use RIPTIDE. We find RIPTIDE’s FFA to be more sensitive; however, it is also the slowest algorithm. PRESTO’s FFT, although faster than others, also shows some unexpected inaccuracies in detection properties. SPS is highly sensitive to long-period and nulling signals, but only for pulses with high intrinsic signal-to-noise ratios. We use these findings to inform current and future pulsar surveys that aim to uncover a large population of long-period or nulling objects and comment on how to make optimal use of these methods in unison.
{"title":"Increasing the detectability of long-period and nulling pulsars in next-generation pulsar surveys","authors":"Garvit Grover, Ramesh Bhat, Samuel McSweeney","doi":"10.1017/pasa.2024.67","DOIUrl":"https://doi.org/10.1017/pasa.2024.67","url":null,"abstract":"<p>Recent discoveries of multiple long-period pulsars (periods <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240917131836263-0508:S1323358024000675:S1323358024000675_inline1.png\"><span data-mathjax-type=\"texmath\"><span>${sim}10,$</span></span></img></span></span>s or larger) are starting to challenge the conventional notion that coherent radio emission cannot be produced by objects that are below the many theorised death lines. Many of the past pulsar surveys and software have been prone to selection effects that restricted their sensitivities towards long-period and sporadically emitting objects. Pulsar surveys using new-generation low-frequency facilities are starting to employ longer dwell times, which makes them significantly more sensitive in detecting long-period or nulling pulsars. There have also been software advancements to aid more sensitive searches towards long-period objects. Furthermore, recent discoveries suggest that nulling may be a key aspect of the long-period pulsar population. We simulate both long-period and nulling pulsar signals, using the Southern-sky MWA Rapid Two-meter (SMART) survey data as reference and explore the detection efficacy of popular search methods such as the fast Fourier transform (FFT), fast-folding algorithm (FFA) and single pulse search (SPS). For FFT-based search and SPS, we make use of the PRESTO implementation, and for FFA we use RIPTIDE. We find RIPTIDE’s FFA to be more sensitive; however, it is also the slowest algorithm. PRESTO’s FFT, although faster than others, also shows some unexpected inaccuracies in detection properties. SPS is highly sensitive to long-period and nulling signals, but only for pulses with high intrinsic signal-to-noise ratios. We use these findings to inform current and future pulsar surveys that aim to uncover a large population of long-period or nulling objects and comment on how to make optimal use of these methods in unison.</p>","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"198 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267468","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}
This study presents an analysis of the optical variability of the blazar 1E 1458.8+2249 on diverse timescales using multi-band observations, including observations in the optical BVRI bands carried out with the T60 and T100 telescopes from 2020 to 2023 and ZTF gri data from 2018 to 2023. On seven nights, we searched for intraday variability using the power-enhanced F-test and the nested ANOVA test, but no significant variability was found. The long-term light curve shows a variability behaviour in the optical BVRI bands with amplitudes of $sim$ 100% and in the gri bands with amplitudes of $sim$ 120%, including short-term variability of up to $sim$ 1.1 mag. Correlation analysis revealed a strong correlation between the optical multi-band emissions without any time lag. From 62 nightly spectral energy distributions, we obtained spectral indices between 0.826 and 1.360, with an average of $1.128pm0.063$ . The relationships of both spectral indices and colour with respect to brightness indicate a mild BWB trend throughout the observation period, both intraday and long-term. We also performed a periodicity search using the weighted wavelet Z-transform and Lomb–Scargle methods. A recurrent optical emission pattern with a quasi-periodicity of $sim$ 340 days is detected in the combined V- and R-band light curves. The observational results indicate that the blazar 1E 1458.8+2249 has a complex variability, while emphasising the need for future observations to unravel its underlying mechanisms.
本研究利用多波段观测数据，包括2020年至2023年利用T60和T100望远镜进行的BVRI光学波段观测数据和2018年至2023年的ZTF gri数据，对1E 1458.8+2249这颗类星体在不同时间尺度上的光学变率进行了分析。在七个夜晚，我们使用幂增强 F 检验和嵌套方差分析检验寻找日内变率，但没有发现显著的变率。长期光曲线显示，BVRI光学波段的变率为100%，Gri波段的变率为120%，包括高达1.1等的短期变率。相关分析表明，光学多波段发射之间有很强的相关性，没有任何时滞。从 62 个夜间光谱能量分布中，我们得到了介于 0.826 和 1.360 之间的光谱指数，平均值为 1.128 /pm0.063$ 。光谱指数和颜色与亮度的关系表明，在整个观测期间，无论是白天还是长期，都有轻微的 BWB 趋势。我们还利用加权小波 Z 变换和 Lomb-Scargle 方法进行了周期性搜索。在组合的 V 波段和 R 波段光曲线中发现了一个准周期为 340 天的周期性光学发射模式。观测结果表明，1E 1458.8+2249 这颗类星体具有复杂的变异性，同时也强调了未来观测的必要性，以揭示其潜在的机制。
{"title":"Multi-band optical variability on diverse timescales of blazar 1E 1458.8+2249","authors":"Aykut Özdönmez, Murat Tekkeşinoğlu","doi":"10.1017/pasa.2024.59","DOIUrl":"https://doi.org/10.1017/pasa.2024.59","url":null,"abstract":"This study presents an analysis of the optical variability of the blazar 1E 1458.8+2249 on diverse timescales using multi-band observations, including observations in the optical BVRI bands carried out with the T60 and T100 telescopes from 2020 to 2023 and ZTF gri data from 2018 to 2023. On seven nights, we searched for intraday variability using the power-enhanced F-test and the nested ANOVA test, but no significant variability was found. The long-term light curve shows a variability behaviour in the optical BVRI bands with amplitudes of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000596_inline1.png\"/> <jats:tex-math> $sim$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>100% and in the gri bands with amplitudes of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000596_inline2.png\"/> <jats:tex-math> $sim$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>120%, including short-term variability of up to <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000596_inline3.png\"/> <jats:tex-math> $sim$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>1.1 mag. Correlation analysis revealed a strong correlation between the optical multi-band emissions without any time lag. From 62 nightly spectral energy distributions, we obtained spectral indices between 0.826 and 1.360, with an average of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000596_inline4.png\"/> <jats:tex-math> $1.128pm0.063$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>. The relationships of both spectral indices and colour with respect to brightness indicate a mild BWB trend throughout the observation period, both intraday and long-term. We also performed a periodicity search using the weighted wavelet Z-transform and Lomb–Scargle methods. A recurrent optical emission pattern with a quasi-periodicity of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000596_inline5.png\"/> <jats:tex-math> $sim$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>340 days is detected in the combined V- and <jats:italic>R</jats:italic>-band light curves. The observational results indicate that the blazar 1E 1458.8+2249 has a complex variability, while emphasising the need for future observations to unravel its underlying mechanisms.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"1 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267617","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}
Traditional pulsar surveys have primarily employed time-domain periodicity searches. However, these methods are susceptible to effects like scattering, eclipses, and orbital motion. At lower radio frequencies ( $lesssim$ 300 MHz), factors such as dispersion measure and pulse broadening become more prominent, reducing the detection sensitivity. On the other hand, image domain searches for pulsars are not limited by these effects and can extend the parameter space to regions inaccessible to traditional search techniques. Therefore, we have developed a pipeline to form 1-second full Stokes images from offline correlated high time-resolution data from the Murchison Widefield Array (MWA). This led to the development of image-based methodologies to identify new pulsar candidates. In this paper, we applied these methodologies to perform a low-frequency image-based pulsar census of the galactic plane (12 MWA observations, covering $sim$ 6 000 $textrm{deg}^textrm{2}$ sky). This work focuses on the detection of the known pulsar population which were present in the observed region of the sky using both image-based and beamformed methods. This resulted in the detection of 83 known pulsars, with 16 pulsars found only in Stokes I images but not in periodicity searches applied in beamformed data. Notably, for 14 pulsars these are the first reported low-frequency detections. This underscores the importance of image-based searches for pulsars that may be undetectable in time-series data, due to scattering and/or dispersive smearing at low frequencies. This highlights the importance of low-frequency flux density measurements in refining pulsar spectral models and investigating the spectral turnover of pulsars at low frequencies.
传统的脉冲星测量主要采用时域周期搜索。然而，这些方法容易受到散射、日食和轨道运动等效应的影响。在较低的射电频率（300 MHz）下，色散测量和脉冲展宽等因素变得更加突出，从而降低了探测灵敏度。另一方面，脉冲星的图像域搜索不受这些影响的限制，可以将参数空间扩展到传统搜索技术无法进入的区域。因此，我们开发了一个管道，从默奇森宽视场阵列（MWA）的离线相关高时间分辨率数据中形成 1 秒钟的全斯托克斯图像。由此，我们开发了基于图像的方法来识别新的候选脉冲星。在本文中，我们应用这些方法对银河面进行了一次基于图像的低频脉冲星普查（12 次 MWA 观测，覆盖 $sim$ 6 000 $textrm{deg}^textrm{2}$ 天空）。这项工作的重点是利用基于图像的方法和波束成形方法探测天空观测区域内存在的已知脉冲星群。结果探测到 83 颗已知脉冲星，其中有 16 颗脉冲星仅在斯托克斯 I 图像中被发现，但在波束成形数据中的周期搜索中却没有发现。值得注意的是，有 14 颗脉冲星是首次报告的低频探测结果。这凸显了基于图像搜索的重要性，这些脉冲星由于低频散射和/或色散涂抹，在时间序列数据中可能无法探测到。这突出了低频通量密度测量在完善脉冲星光谱模型和研究脉冲星低频光谱转换方面的重要性。
{"title":"Imaging pulsar census of the galactic plane using MWA VCS data","authors":"S. Sett, M. Sokolowski, E. Lenc, N.D.R. Bhat","doi":"10.1017/pasa.2024.62","DOIUrl":"https://doi.org/10.1017/pasa.2024.62","url":null,"abstract":"Traditional pulsar surveys have primarily employed time-domain periodicity searches. However, these methods are susceptible to effects like scattering, eclipses, and orbital motion. At lower radio frequencies (<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000626_inline1.png\"/> <jats:tex-math> $lesssim$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>300 MHz), factors such as dispersion measure and pulse broadening become more prominent, reducing the detection sensitivity. On the other hand, image domain searches for pulsars are not limited by these effects and can extend the parameter space to regions inaccessible to traditional search techniques. Therefore, we have developed a pipeline to form 1-second full Stokes images from offline correlated high time-resolution data from the Murchison Widefield Array (MWA). This led to the development of image-based methodologies to identify new pulsar candidates. In this paper, we applied these methodologies to perform a low-frequency image-based pulsar census of the galactic plane (12 MWA observations, covering <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000626_inline2.png\"/> <jats:tex-math> $sim$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>6 000 <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000626_inline3.png\"/> <jats:tex-math> $textrm{deg}^textrm{2}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> sky). This work focuses on the detection of the known pulsar population which were present in the observed region of the sky using both image-based and beamformed methods. This resulted in the detection of 83 known pulsars, with 16 pulsars found only in Stokes I images but not in periodicity searches applied in beamformed data. Notably, for 14 pulsars these are the first reported low-frequency detections. This underscores the importance of image-based searches for pulsars that may be undetectable in time-series data, due to scattering and/or dispersive smearing at low frequencies. This highlights the importance of low-frequency flux density measurements in refining pulsar spectral models and investigating the spectral turnover of pulsars at low frequencies.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"18 799 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267620","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}
Marcin Sokolowski, Gayatri Aniruddha, Cristian Di Pietrantonio, Chris Harris, Danny Price, Samuel McSweeney, Randall Bruce Wayth, Ramesh Bhat
Fast Radio Bursts (FRBs) are millisecond dispersed radio pulses of predominately extra-galactic origin. Although originally discovered at GHz frequencies, most FRBs have been detected between 400 and 800 MHz. Nevertheless, only a handful of FRBs were detected at radio frequencies $le$ 400 MHz. Searching for FRBs at low frequencies is computationally challenging due to increased dispersive delay that must be accounted for. Nevertheless, the wide field of view (FoV) of low-frequency telescopes – such as the the Murchison Widefield Array (MWA), and prototype stations of the low-frequency Square Kilometre Array (SKA-Low) – makes them promising instruments to open a low-frequency window on FRB event rates, and constrain FRB emission models. The standard approach, inherited from high-frequencies, is to form multiple tied-array beams to tessellate the entire FoV and perform the search on the resulting time series. This approach, however, may not be optimal for low-frequency interferometers due to their large FoVs and high spatial resolutions leading to a large number of beams. Consequently, there are regions of parameter space in terms of number of antennas and resolution elements (pixels) where interferometric imaging is computationally more efficient. Here we present a new high-time resolution imager BLINK implemented on modern graphical processing units (GPUs) and intended for radio astronomy data. The main goal for this imager is to become part of a fully GPU-accelerated FRB search pipeline. We describe the imager and present its verification on real and simulated data processed to form all-sky and widefield images from the MWA and prototype SKA-Low stations. We also present and compare benchmarks of the GPU and CPU code executed on laptops, desktop computers, and Australian supercomputers. The code is publicly available at https://github.com/PaCER-BLINK-Project/imager and can be applied to data from any radio telescope.
{"title":"High-time resolution GPU imager for FRB searches at low radio frequencies","authors":"Marcin Sokolowski, Gayatri Aniruddha, Cristian Di Pietrantonio, Chris Harris, Danny Price, Samuel McSweeney, Randall Bruce Wayth, Ramesh Bhat","doi":"10.1017/pasa.2024.46","DOIUrl":"https://doi.org/10.1017/pasa.2024.46","url":null,"abstract":"Fast Radio Bursts (FRBs) are millisecond dispersed radio pulses of predominately extra-galactic origin. Although originally discovered at GHz frequencies, most FRBs have been detected between 400 and 800 MHz. Nevertheless, only a handful of FRBs were detected at radio frequencies <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000468_inline1.png\"/> <jats:tex-math> $le$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>400 MHz. Searching for FRBs at low frequencies is computationally challenging due to increased dispersive delay that must be accounted for. Nevertheless, the wide field of view (FoV) of low-frequency telescopes – such as the the Murchison Widefield Array (MWA), and prototype stations of the low-frequency Square Kilometre Array (SKA-Low) – makes them promising instruments to open a low-frequency window on FRB event rates, and constrain FRB emission models. The standard approach, inherited from high-frequencies, is to form multiple tied-array beams to tessellate the entire FoV and perform the search on the resulting time series. This approach, however, may not be optimal for low-frequency interferometers due to their large FoVs and high spatial resolutions leading to a large number of beams. Consequently, there are regions of parameter space in terms of number of antennas and resolution elements (pixels) where interferometric imaging is computationally more efficient. Here we present a new high-time resolution imager <jats:italic>BLINK</jats:italic> implemented on modern graphical processing units (GPUs) and intended for radio astronomy data. The main goal for this imager is to become part of a fully GPU-accelerated FRB search pipeline. We describe the imager and present its verification on real and simulated data processed to form all-sky and widefield images from the MWA and prototype SKA-Low stations. We also present and compare benchmarks of the GPU and CPU code executed on laptops, desktop computers, and Australian supercomputers. The code is publicly available at <jats:uri xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"https://github.com/PaCER-BLINK-Project/imager\">https://github.com/PaCER-BLINK-Project/imager</jats:uri> and can be applied to data from any radio telescope.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"119 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267623","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}
Ashley Elliott, Tabetha Boyajian, Tyler Ellis, Kaspar von Braun, Andrew W. Mann, Gail Schaefer
In order to study exoplanets, a comprehensive characterisation of the fundamental properties of the host stars – such as angular diameter, temperature, luminosity, and age, is essential, as the formation and evolution of exoplanets are directly influenced by the host stars at various points in time. In this paper, we present interferometric observations taken of directly imaged planet host 51 Eridani at the CHARA Array. We measure the limb-darkened angular diameter of 51 Eridani to be <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358024000407_inline1.png"/> <jats:tex-math> $theta_mathrm{LD} = 0.450pm 0.006$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> mas and combining with the Gaia zero-point corrected parallax, we get a stellar radius of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358024000407_inline2.png"/> <jats:tex-math> $1.45 pm 0.02$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> R<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358024000407_inline3.png"/> <jats:tex-math> $_{odot}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>. We use the PARSEC isochrones to estimate an age of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358024000407_inline4.png"/> <jats:tex-math> $23.2^{+1.7}_{-2.0}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> Myr and a mass of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358024000407_inline5.png"/> <jats:tex-math> $1.550^{+0.006}_{-0.005}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> M<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358024000407_inline6.png"/> <jats:tex-math> $_{odot}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>. The age and mass agree well with values in the literature, determined through a variety of methods ranging from dynamical age trace-backs to lithium depletion boundary methods. We derive a mass of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358024000407_inline7.png"/> <jats:tex-math> $4.1pm0.4$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> M<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" mime-subtype="png" xlink:href="S1323358024000407_inline8.png"/> <jats:tex-math> $_mathrm{Jup}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> for 51 Eri b using the Sonora
为了研究系外行星，对宿主恒星的基本特性--如角直径、温度、光度和年龄--进行全面描述是至关重要的，因为系外行星的形成和演化在不同时间点上都会受到宿主恒星的直接影响。在本文中，我们介绍了在 CHARA 阵列上对直接成像的行星宿主 51 Eridani 进行的干涉测量观测。我们测量出51 Eridani的边缘暗角直径为$theta_mathrm{LD} = 0.450pm 0.006$ mas，结合盖亚零点校正视差，我们得到的恒星半径为$1.45 pm 0.02$ R $_{odot}$。我们利用PARSEC等时线估算出它的年龄为23.2^{+1.7}_{-2.0}$ Myr，质量为1.550^{+0.006}_{-0.005}$ M $_{odot}$。年龄和质量与文献中的数值非常吻合，这些数值是通过从动态年龄回溯法到锂耗竭边界法等多种方法确定的。我们利用索诺拉山猫模型推算出51 Eri b的质量为$4.1/pm0.4$ M $_mathrm{Jup}$，这进一步支持了51 Eri b在热启动形成模型或暖启动形成模型下形成的可能性。
{"title":"Measuring the stellar and planetary parameters of the 51 Eridani system","authors":"Ashley Elliott, Tabetha Boyajian, Tyler Ellis, Kaspar von Braun, Andrew W. Mann, Gail Schaefer","doi":"10.1017/pasa.2024.40","DOIUrl":"https://doi.org/10.1017/pasa.2024.40","url":null,"abstract":"In order to study exoplanets, a comprehensive characterisation of the fundamental properties of the host stars – such as angular diameter, temperature, luminosity, and age, is essential, as the formation and evolution of exoplanets are directly influenced by the host stars at various points in time. In this paper, we present interferometric observations taken of directly imaged planet host 51 Eridani at the CHARA Array. We measure the limb-darkened angular diameter of 51 Eridani to be <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline1.png\"/> <jats:tex-math> $theta_mathrm{LD} = 0.450pm 0.006$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> mas and combining with the Gaia zero-point corrected parallax, we get a stellar radius of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline2.png\"/> <jats:tex-math> $1.45 pm 0.02$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> R<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline3.png\"/> <jats:tex-math> $_{odot}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>. We use the PARSEC isochrones to estimate an age of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline4.png\"/> <jats:tex-math> $23.2^{+1.7}_{-2.0}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> Myr and a mass of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline5.png\"/> <jats:tex-math> $1.550^{+0.006}_{-0.005}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> M<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline6.png\"/> <jats:tex-math> $_{odot}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula>. The age and mass agree well with values in the literature, determined through a variety of methods ranging from dynamical age trace-backs to lithium depletion boundary methods. We derive a mass of <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline7.png\"/> <jats:tex-math> $4.1pm0.4$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> M<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000407_inline8.png\"/> <jats:tex-math> $_mathrm{Jup}$ </jats:tex-math> </jats:alternatives> </jats:inline-formula> for 51 Eri b using the Sonora ","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"8 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142267619","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}
In gamma-ray binaries neutron star is orbiting a companion that produces a strong stellar wind. We demonstrate that observed properties of ‘stellar wind’–‘pulsar wind’ interaction depend both on the overall wind thrust ratio, as well as more subtle geometrical factors: the relative direction of the pulsar’s spin, the plane of the orbit, the direction of motion, and the instantaneous line of sight. Using fully 3D relativistic magnetohydrodynamical simulations we find that the resulting intrinsic morphologies can be significantly orbital phase-dependent: a given system may change from tailward-open to tailward-closed shapes. As a result, the region of unshocked pulsar wind can change by an order of magnitude over a quarter of the orbit. We calculate radiation maps and synthetic light curves for synchrotron (X-ray) and inverse-Compton emission (GeV-TeV), taking into account $gamma $ – $gamma $ absorption. Our modelled light curves are in agreement with the phase-dependent observed light curves of LS5039.
{"title":"3D relativistic MHD simulations of the gamma-ray binaries","authors":"Maxim Barkov, Evgeniy Kalinin, Maxim Lyutikov","doi":"10.1017/pasa.2024.52","DOIUrl":"https://doi.org/10.1017/pasa.2024.52","url":null,"abstract":"In gamma-ray binaries neutron star is orbiting a companion that produces a strong stellar wind. We demonstrate that observed properties of ‘stellar wind’–‘pulsar wind’ interaction depend both on the overall wind thrust ratio, as well as more subtle geometrical factors: the relative direction of the pulsar’s spin, the plane of the orbit, the direction of motion, and the instantaneous line of sight. Using fully 3D relativistic magnetohydrodynamical simulations we find that the resulting intrinsic morphologies can be significantly orbital phase-dependent: a given system may change from tailward-open to tailward-closed shapes. As a result, the region of unshocked pulsar wind can change by an order of magnitude over a quarter of the orbit. We calculate radiation maps and synthetic light curves for synchrotron (X-ray) and inverse-Compton emission (GeV-TeV), taking into account <jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000523_inline1.png\"/> <jats:tex-math> $gamma $ </jats:tex-math> </jats:alternatives> </jats:inline-formula>–<jats:inline-formula> <jats:alternatives> <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000523_inline2.png\"/> <jats:tex-math> $gamma $ </jats:tex-math> </jats:alternatives> </jats:inline-formula> absorption. Our modelled light curves are in agreement with the phase-dependent observed light curves of LS5039.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"41 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269638","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}
The interaction between stellar winds and the partially ionized local interstellar medium (LISM) is quite common in astrophysics. However, the main difficulty in describing the neutral components lies in the fact that the mean free path of an interstellar atom, l, can be comparable to the characteristic size of an astrosphere, L (i.e., the Knudsen number, which is equal to l/L, is approximately equal to 1, as in the case of the heliosphere). In such cases, a single-fluid approximation becomes invalid, and a kinetic description must be used for the neutral component. In this study, we consider a general astrosphere and use a kinetic-gas dynamics model to investigate how the global structure of the astrosphere depends on the Knudsen number. We present numerical results covering an extremely wide range of Knudsen numbers (from 0.0001 to 100). Additionally, we explore the applicability of single-fluid approaches for modeling astrospheres of various sizes. We have excluded the influence of interstellar and stellar magnetic fields in our model to make parametric study of the kinetic effects feasible. The main conclusion of this work is that, for large astrospheres (with a distance to the bow shock greater than 600 AU) a heated rarefied plasma layer forms in the outer shock layer near the astropause. The formation of this layer is linked to localized heating of the plasma by atoms (specifically, ENAs) that undergo charge exchange again behind the astropause. This process significantly alters the flow structure in the outer shock layer and the location of the bow shock, and it cannot be described by a single-fluid model. Additionally, this paper discusses how atoms weaken the bow shocks at near-heliospheric conditions.
恒星风与部分电离的局部星际介质（LISM）之间的相互作用在天体物理学中十分常见。然而，描述中性成分的主要困难在于星际原子的平均自由路径 l 可能与天体球的特征尺寸 L 相当（即克努森数等于 l/L，近似等于 1，如日光层的情况）。在这种情况下，单流体近似变得无效，必须对中性成分使用动力学描述。在这项研究中，我们考虑了一个普通的天体，并使用动力学-气体动力学模型来研究天体的全局结构如何取决于克努森数。我们给出的数值结果涵盖了极宽的努森数范围（从 0.0001 到 100）。此外，我们还探索了单流体方法对各种尺寸天体的建模适用性。我们在模型中排除了星际磁场和恒星磁场的影响，以便对动力学效应进行可行的参数研究。这项工作的主要结论是，对于大型天体（与弓形冲击波的距离大于 600 AU），在靠近天体顶点的外部冲击层中会形成一个受热的稀薄等离子体层。该层的形成与原子（特别是ENAs）对等离子体的局部加热有关，这些原子在天体休止符后再次进行电荷交换。这一过程极大地改变了外部冲击层的流动结构和弓形冲击的位置，无法用单一流体模型来描述。此外，本文还讨论了原子如何在近对流层条件下削弱弓形冲击。
{"title":"The global structure of astrospheres: effect of Knudsen number","authors":"S.D. Korolkov, V.V. Izmodenov","doi":"10.1017/pasa.2024.44","DOIUrl":"https://doi.org/10.1017/pasa.2024.44","url":null,"abstract":"The interaction between stellar winds and the partially ionized local interstellar medium (LISM) is quite common in astrophysics. However, the main difficulty in describing the neutral components lies in the fact that the mean free path of an interstellar atom, l, can be comparable to the characteristic size of an astrosphere, L (i.e., the Knudsen number, which is equal to l/L, is approximately equal to 1, as in the case of the heliosphere). In such cases, a single-fluid approximation becomes invalid, and a kinetic description must be used for the neutral component. In this study, we consider a general astrosphere and use a kinetic-gas dynamics model to investigate how the global structure of the astrosphere depends on the Knudsen number. We present numerical results covering an extremely wide range of Knudsen numbers (from 0.0001 to 100). Additionally, we explore the applicability of single-fluid approaches for modeling astrospheres of various sizes. We have excluded the influence of interstellar and stellar magnetic fields in our model to make parametric study of the kinetic effects feasible. The main conclusion of this work is that, for large astrospheres (with a distance to the bow shock greater than 600 AU) a heated rarefied plasma layer forms in the outer shock layer near the astropause. The formation of this layer is linked to localized heating of the plasma by atoms (specifically, ENAs) that undergo charge exchange again behind the astropause. This process significantly alters the flow structure in the outer shock layer and the location of the bow shock, and it cannot be described by a single-fluid model. Additionally, this paper discusses how atoms weaken the bow shocks at near-heliospheric conditions.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"6 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141608428","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}
The baryon mass content (i.e. stellar and gas mass) of dark matter halos in the early Universe depends on both global factors - e.g. ionizing ultraviolet (UV) radiation background - and local factors - e.g. star formation efficiency and assembly history. We use a lightweight semi-analytical model to investigate how both local and global factors impact the halo baryon mass content at redshifts of z ≥ 5. Our model incorporates a time delay between when stars form and when they produce feedback of 0 ≤ td/Myr ≤ 30, which can drive bursts of star formation, and a mass and redshift dependent UV background, which captures the influence of cosmological reionization on gas accretion onto halos. We use statistically representative halo assembly histories and assume that the cosmological gas accretion rate is proportional to the halo mass accretion rate. Delayed (td>0) feedback leads to oscillations in gas mass with cosmic time, behaviour that cannot be captured with instantaneous feedback (td=0). Highly efficient star formation drives stronger oscillations, while strong feedback impacts when oscillations occur; in contrast, inefficient star formation and weak feedback produce similar long-term behaviour to that observed in instantaneous feedback models. If the delayed feedback timescale is too long, a halo retains its gas reservoir but the feedback suppresses star formation. Our model predicts that lower mass systems (halo masses mh ≤ 107M⊙) at z ≤ 10 should be strongly gas deficient (mg → 0), whereas higher mass systems retain their gas reservoirs because they are sufficiently massive to continue accreting gas through cosmological reionization. Interestingly, in higher mass halos, the median m⋆/(m⋆ + mg) ≃ 0.01 – 0.05, but is a factor of 3-5 smaller when feedback is delayed. Our model does not include seed supermassive black hole feedback, which is necessary to explain massive quenched galaxies in the early Universe.
{"title":"On bursty star formation during cosmological reionization - how does it influence the baryon mass content of dark matter halos?","authors":"Anand Menon, Chris Power","doi":"10.1017/pasa.2024.39","DOIUrl":"https://doi.org/10.1017/pasa.2024.39","url":null,"abstract":"The baryon mass content (i.e. stellar and gas mass) of dark matter halos in the early Universe depends on both global factors - e.g. ionizing ultraviolet (UV) radiation background - and local factors - e.g. star formation efficiency and assembly history. We use a lightweight semi-analytical model to investigate how both local and global factors impact the halo baryon mass content at redshifts of <jats:italic>z</jats:italic> ≥ 5. Our model incorporates a time delay between when stars form and when they produce feedback of 0 ≤ <jats:italic>t<jats:sup>d</jats:sup></jats:italic>/Myr ≤ 30, which can drive bursts of star formation, and a mass and redshift dependent UV background, which captures the influence of cosmological reionization on gas accretion onto halos. We use statistically representative halo assembly histories and assume that the cosmological gas accretion rate is proportional to the halo mass accretion rate. Delayed (<jats:italic>t<jats:sup>d</jats:sup></jats:italic>>0) feedback leads to oscillations in gas mass with cosmic time, behaviour that cannot be captured with instantaneous feedback (<jats:italic>t<jats:sup>d</jats:sup></jats:italic>=0). Highly efficient star formation drives stronger oscillations, while strong feedback impacts when oscillations occur; in contrast, inefficient star formation and weak feedback produce similar long-term behaviour to that observed in instantaneous feedback models. If the delayed feedback timescale is too long, a halo retains its gas reservoir but the feedback suppresses star formation. Our model predicts that lower mass systems (halo masses <jats:italic>m</jats:italic><jats:sub>h</jats:sub> ≤ 10<jats:sup>7</jats:sup>M<jats:sub>⊙</jats:sub>) at <jats:italic>z</jats:italic> ≤ 10 should be strongly gas deficient (<jats:italic>m</jats:italic>g → 0), whereas higher mass systems retain their gas reservoirs because they are sufficiently massive to continue accreting gas through cosmological reionization. Interestingly, in higher mass halos, the median <jats:italic>m</jats:italic><jats:sub>⋆</jats:sub>/(<jats:italic>m</jats:italic><jats:sub>⋆</jats:sub> + <jats:italic>m</jats:italic><jats:sub>g</jats:sub>) ≃ 0.01 – 0.05, but is a factor of 3-5 smaller when feedback is delayed. Our model does not include seed supermassive black hole feedback, which is necessary to explain massive quenched galaxies in the early Universe.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"136 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140940649","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}
Ravi Jaiswar, Anshu Gupta, Elisabete da Cunha, Cathryn M. Trott, Anishya Harshan, Andrew Battisti, Ben Forrest
The nature of the first galaxies that reionized the universe during the Epoch of Reionization (EoR) remains unclear. Attempts to directly determine spectral properties of these early galaxies are affected by both limited photometric constraints across the spectrum and by the opacity of the intergalactic medium (IGM) to the Lyman Continuum (LyC) at high redshift. We approach this by analysing properties of analogous extreme emission line galaxies (EELGs, [OIII]+Hbeta EW> 400) at 2.5 < z < 4 from the ZFOURGE survey using the Multi-wavelength Analysis of Galaxy Physical Properties (MAGPHYS) SED fitting code. We compare these to galaxies at z > 5.5 observed with the James Webb Space Telesope (JWST) with self-consistent spectral energy distribution fitting methodology. This work focuses on the comparison of their UV slopes (βP), ionizing photon production efficiencies ξion, star formation rates and dust properties to determine the effectiveness of this analogue selection technique. We report the median ionizing photon production efficiencies as for our ZFOURGE control, ZFOURGE EELG, JADES and CEERS samples respectively. ZFOURGE EELGs are 0.57 dex lower in stellar mass and have half the dust extinction, compared to their ZFOURGE control counterparts. They also have a similar specific star formation rates and βP to the z > 5.5 samples. We find that EELGs at low redshift (2.5 < z < 4) are analogous to EoR galaxies in their dust attenuation and specific star formation rates. Their extensive photometric coverage and the accessibility of their LyC region opens pathways to infer stellar population properties in the EoR.
在宇宙再电离纪元（EoR）期间，宇宙再电离的第一批星系的性质仍然不清楚。试图直接确定这些早期星系的光谱特性，受到了整个光谱中有限的测光约束和高红移时星系间介质（IGM）对莱曼连续（LyC）的不透明性的影响。我们利用星系物理特性多波长分析（MAGPHYS）SED拟合代码，分析了ZFOURGE巡天中2.5 < z < 4处的类似极端发射线星系（EELGs，[OIII]+Hbeta EW> 400）的特性。我们利用自洽光谱能量分布拟合方法，将这些星系与詹姆斯-韦伯太空望远镜（JWST）观测到的 z > 5.5 的星系进行了比较。这项工作的重点是比较它们的紫外斜率（βP）、电离光子产生效率ξion、恒星形成率和尘埃特性，以确定这种模拟选择技术的有效性。我们分别报告了 ZFOURGE 对照样本、ZFOURGE EELG 样本、JADES 样本和 CEERS 样本的电离光子产生效率中值。与 ZFOURGE 对照样本相比，ZFOURGE EELG 的恒星质量低 0.57 dex，尘埃消光也只有对照样本的一半。它们的特定恒星形成率和βP也与z > 5.5样本相似。我们发现，低红移（2.5 < z <4）的EELG在尘埃衰减和特定恒星形成率方面与EoR星系类似。它们广泛的光度覆盖范围和LyC区域的可及性，为推断EoR星系的恒星群特性开辟了道路。
{"title":"MOSEL survey: Unwrapping the Epoch of Reionization through mimic galaxies at Cosmic Noon","authors":"Ravi Jaiswar, Anshu Gupta, Elisabete da Cunha, Cathryn M. Trott, Anishya Harshan, Andrew Battisti, Ben Forrest","doi":"10.1017/pasa.2024.37","DOIUrl":"https://doi.org/10.1017/pasa.2024.37","url":null,"abstract":"The nature of the first galaxies that reionized the universe during the Epoch of Reionization (EoR) remains unclear. Attempts to directly determine spectral properties of these early galaxies are affected by both limited photometric constraints across the spectrum and by the opacity of the intergalactic medium (IGM) to the Lyman Continuum (LyC) at high redshift. We approach this by analysing properties of analogous extreme emission line galaxies (EELGs, [OIII]+Hbeta EW> 400) at 2.5 < <jats:italic>z</jats:italic> < 4 from the ZFOURGE survey using the Multi-wavelength Analysis of Galaxy Physical Properties (MAGPHYS) SED fitting code. We compare these to galaxies at <jats:italic>z</jats:italic> > 5.5 observed with the James Webb Space Telesope (JWST) with self-consistent spectral energy distribution fitting methodology. This work focuses on the comparison of their UV slopes (β<jats:italic>P</jats:italic>), ionizing photon production efficiencies ξ<jats:italic>ion</jats:italic>, star formation rates and dust properties to determine the effectiveness of this analogue selection technique. We report the median ionizing photon production efficiencies as <jats:inline-graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" mime-subtype=\"png\" xlink:href=\"S1323358024000377_inline1.png\"/> for our ZFOURGE control, ZFOURGE EELG, JADES and CEERS samples respectively. ZFOURGE EELGs are 0.57 dex lower in stellar mass and have half the dust extinction, compared to their ZFOURGE control counterparts. They also have a similar specific star formation rates and β<jats:italic>P</jats:italic> to the <jats:italic>z</jats:italic> > 5.5 samples. We find that EELGs at low redshift (2.5 < <jats:italic>z</jats:italic> < 4) are analogous to EoR galaxies in their dust attenuation and specific star formation rates. Their extensive photometric coverage and the accessibility of their LyC region opens pathways to infer stellar population properties in the EoR.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"25 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140940871","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}
In radio astronomy, the science output of a telescope is often limited by computational resources. This is especially true for transient and technosignature surveys that need to search high-resolution data across a large parameter space. The tremendous data volumes produced by modern radio array telescopes exacerbate these processing challenges. Here, we introduce a ‘reduced-resolution’ beamforming approach to alleviate downstream processing requirements. Our approach, based on post-correlation beamforming, allows sensitivity to be traded against the number of beams needed to cover a given survey area. Using the MeerKAT and Murchison Widefield Array telescopes as examples, we show that survey speed can be vastly increased, and downstream signal processing requirements vastly decreased, if a moderate sacrifice to sensitivity is allowed. We show the reduced-resolution beamforming technique is intimately related to standard techniques used in synthesis imaging. We suggest that reduced-resolution beamforming should be considered to ease data processing challenges in current and planned searches; further, reduced-resolution beamforming may provide a path to computationally-expensive search strategies previously considered infeasible.
{"title":"Reduced-resolution beamforming: lowering the computational cost for pulsar and technosignature surveys","authors":"D. C. Price","doi":"10.1017/pasa.2024.35","DOIUrl":"https://doi.org/10.1017/pasa.2024.35","url":null,"abstract":"In radio astronomy, the science output of a telescope is often limited by computational resources. This is especially true for transient and technosignature surveys that need to search high-resolution data across a large parameter space. The tremendous data volumes produced by modern radio array telescopes exacerbate these processing challenges. Here, we introduce a ‘reduced-resolution’ beamforming approach to alleviate downstream processing requirements. Our approach, based on post-correlation beamforming, allows sensitivity to be traded against the number of beams needed to cover a given survey area. Using the MeerKAT and Murchison Widefield Array telescopes as examples, we show that survey speed can be vastly increased, and downstream signal processing requirements vastly decreased, if a moderate sacrifice to sensitivity is allowed. We show the reduced-resolution beamforming technique is intimately related to standard techniques used in synthesis imaging. We suggest that reduced-resolution beamforming should be considered to ease data processing challenges in current and planned searches; further, reduced-resolution beamforming may provide a path to computationally-expensive search strategies previously considered infeasible.","PeriodicalId":20753,"journal":{"name":"Publications of the Astronomical Society of Australia","volume":"309 1","pages":""},"PeriodicalIF":6.3,"publicationDate":"2024-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140940849","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}
${sim}10,$s or larger) are starting to challenge the conventional notion that coherent radio emission cannot be produced by objects that are below the many theorised death lines. Many of the past pulsar surveys and software have been prone to selection effects that restricted their sensitivities towards long-period and sporadically emitting objects. Pulsar surveys using new-generation low-frequency facilities are starting to employ longer dwell times, which makes them significantly more sensitive in detecting long-period or nulling pulsars. There have also been software advancements to aid more sensitive searches towards long-period objects. Furthermore, recent discoveries suggest that nulling may be a key aspect of the long-period pulsar population. We simulate both long-period and nulling pulsar signals, using the Southern-sky MWA Rapid Two-meter (SMART) survey data as reference and explore the detection efficacy of popular search methods such as the fast Fourier transform (FFT), fast-folding algorithm (FFA) and single pulse search (SPS). For FFT-based search and SPS, we make use of the PRESTO implementation, and for FFA we use RIPTIDE. We find RIPTIDE’s FFA to be more sensitive; however, it is also the slowest algorithm. PRESTO’s FFT, although faster than others, also shows some unexpected inaccuracies in detection properties. SPS is highly sensitive to long-period and nulling signals, but only for pulses with high intrinsic signal-to-noise ratios. We use these findings to inform current and future pulsar surveys that aim to uncover a large population of long-period or nulling objects and comment on how to make optimal use of these methods in unison.
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