[論文レビュー] GBD-DART-II: 175 MHz Polarimetric Observation of Pulsars from Gauribidanur and a New Pulsar Signal Processing Pipeline

Arul Pandian B, Joydeep Bagchi+3 more|arXiv (Cornell University)|Jan 31, 2026

Radio Astronomy Observations and Technology被引用数 0

ひとこと要約

新しいパルサー信号処理パイプラインをGBD-DARTアレイ（175 MHz、全極性機能、リアルタイムデータ処理、5つの明るいパルサーのRM/単一パルス結果とともに）で紹介。

ABSTRACT

A new pulsar signal-processing pipeline has been developed for observing pulsars with the Diamond Array Radio Telescope at the Gauribidanur radio observatory. The array consists of 32 off-axis dual-polarised LPDAs, with a nominal gain of 22 dBi between 130 and 350 MHz and a 15-degree HPBW at 175 MHz for transit observations on pulsars. Custom-built receivers and real-time data-capture and analysis tools have been developed and used. Receiver output voltages from a transient buffer, as well as full-polar spectral data at both high and low resolutions, suitable for transient searches and pulsar studies. Additionally, full-polar folded profile archives are generated for known pulsars in subintegrations and both coherent and incoherent dedispersion. Custom-developed Python routines, FFT libraries, DSPSR, PSRCHIVE, and Presto modules have been used to build the pipeline. The functionalities of the pipeline were validated with artificially generated pulsar signals and strong celestial sources before it was released for routine observations. Presently, the pipeline is configured to observe pulsars between 170 and 196 MHz, with a daily cadence. Recorded data are reduced in-line immediately following each observation, nearly matching the observation time at a 1:1 ratio. An Intel i9 server captures the data, and an AMD R9 CPU does the primary data reduction. The archives are routinely backed up to a remote system via the internet. The paper presents the architecture of the signal processing pipeline developed, its validation, and initial polarimetric results observing five bright pulsars at 175 MHz. Results also include RM estimates and single-pulse study results for B0953+08, B0531+21, and B1133+16, as well as from monitoring the spin-down of the Crab pulsar over 200 days of observation. Finally, it presents a discussion on the potential improvements for the array.

研究の動機と目的

• GBD-DART用の175 MHzで全偏光を備えた新しいパルサー観測パイプラインを開発・展開する。
• コヒーレントおよび非コヒーレントデディスペリングを含むリアルタイムデータ取得、処理、アーカイブを実装する。
• 人工信号およびシミュレートされた偏光信号でパイプラインを検証する。
• 複数の明るいパルサーの偏光結果（RM、単一パルス）を実証し、Crabパルサの回転減速を監視する。
• ビームステアリング、広帯域観測、データ処理の将来の改良の基盤を提供する。

提案手法

• 32 off-axis dual-polarised LPDAs forming a diamond-shaped 64-element array with ~22 dBi gain at 200 MHz.
• Analog front-end (LNA, BALUN, Tubular Receiver) delivering ~51 dB gain over 120–350 MHz and two polarisations.
• Portable dual receiver (PDR): two-channel, 16-MHz-wideband heterodyne receiver with 33 MSPS ADCs and GPS-synced timing.
• Data capture with UDP/PCAP workflow and transient buffering (GULP) enabling 1-minute-level archival and 5-minute raw buffer triggering.
• Online processing using Python scripts plus DSPSR, DIGIFITS, PRESTO, and PSRCHIVE tools for coherent/incoherent dedispersion, folding, and RFI mitigation.
• RFI mitigation via Iterative Cleaner; data archived in DADA/PSRFITS formats; timing and polarization calibration using pac/PSRCHIVE.

Figure 1: GBD-DART Signal Chain, data flow, and testing provisions of the pipeline.

実験結果

リサーチクエスチョン

• RQ1 175 MHz偏光パイプラインで全Stokesパラメータをほぼリアルタイムで観測できるか？
• RQ2 このパイプラインで5つの明るいパルサーが示すRM値と偏光特性は何か？
• RQ3 データスループット、処理時間、トリガーイベントによるバッファリングの観点でパイプラインはどうか？
• RQ4 175 MHzでの単一パルス検索およびジ Giantパルス検出の能力はどの程度か？

主な発見

• 全Stokesモードで5つの明るいパルサーを偏光対応プロファイルとともに観測。
• 観測期間中のRM推定にはJ0953+0755: 3.08 ± 1.14 rad/m^2 および J0534+2200: -39.4 ± 1.8 rad/m^2 が含まれる。
• Crabパルサのスピンダウンを約200日間監視し、長期タイミング能力を検証。
• J0953+0755から40分のデータでSNR 5を超える約3978個の単一パルスを検出。
• J0534+2200の巨パルスを約1分に1回の頻度で検出（11.3時間にわたり18日間の期間）; 複数パルスの偏光データが顕著。

Figure 2: Differential signals from the LPDA are fed to the Low Noise Amplifier via a BALUN. The amplifier inputs are fitted with a high-pass filter to reject frequencies below 130 MHz. The low noise amplifier module has a gain of 20 dB and a noise figure of 1.35 dB.