New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR.
New methods to constrain the radio transient rate: results from a survey of four fields with LOFAR.
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限制无线电瞬变率的新方法：使用 LOFAR 对四个区域进行调查的结果。
DOI：
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发表时间：
2014
影响因子：
4.8
通讯作者：
P. Zarka
中科院分区：
文献类型：
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作者：
D. Carbone;A. V. D. Horst;R. Wijers;J. Swinbank;A. Rowlinson;J. Broderick;Y. Cendes;A. Stewart;M. Bell;R. Breton;S. Corbel;J. Eislöffel;R. Fender;J. Grießmeier;J. Hessels;P. Jonker;M. Kramer;C. Law;J. Miller;M. Piętka;L. Scheers;B. Stappers;J. V. Leeuwen;R. Wijnands;M. Wise;P. Zarka
我们报告的结果搜索无线电瞬变115和190 MHz之间的低频阵列（LOFAR）。四个领域已被监测的节奏之间的15分钟和几个月。共获得151幅图像，总勘测面积为2275 deg 2。我们使用标准LOFAR工具分析了我们的数据，并使用LOFAR瞬态管道搜索无线电瞬态。没有可靠的无线电瞬变候选人已被检测到，但是，我们能够设定上限的无线电瞬变源在低无线电频率的表面密度。我们还表明，低频无线电调查是更敏感的陡谱相干瞬态源比GHz的无线电调查。我们使用了两种新的统计方法来确定瞬态表面密度的上限。一个是免费的假设上的源的通量分布，而另一个假设幂律分布的通量和设置更严格的约束瞬态表面密度。这两种方法提供了更好的约束比以前的作品中使用的方法。我们可以为瞬态表面密度设置的上限的最佳值，使用假设幂律通量分布的方法，对于时间尺度为15 min，频率为150 MHz，亮度超过0.3 Jy的瞬态，为1.3 × 10-3 deg-2。我们还首次计算了不同时间尺度的瞬态表面密度的上限。我们发现，结果可以从以前报道的，简化的估计不同的数量级。
We report on the results of a search for radio transients between 115 and 190 MHz with the LOw-Frequency ARray (LOFAR). Four fields have been monitored with cadences between 15 min and several months. A total of 151 images were obtained, giving a total survey area of 2275 deg2. We analysed our data using standard LOFAR tools and searched for radio transients using the LOFAR Transients Pipeline. No credible radio transient candidate has been detected; however, we are able to set upper limits on the surface density of radio transient sources at low radio frequencies. We also show that low-frequency radio surveys are more sensitive to steep-spectrum coherent transient sources than GHz radio surveys. We used two new statistical methods to determine the upper limits on the transient surface density. One is free of assumptions on the flux distribution of the sources, while the other assumes a power-law distribution in flux and sets more stringent constraints on the transient surface density. Both of these methods provide better constraints than the approach used in previous works. The best value for the upper limit we can set for the transient surface density, using the method assuming a power-law flux distribution, is 1.3 × 10-3 deg-2 for transients brighter than 0.3 Jy with a time-scale of 15 min, at a frequency of 150 MHz. We also calculated for the first time upper limits for the transient surface density for transients of different time-scales. We find that the results can differ by orders of magnitude from previously reported, simplified estimates.
影响因子：
6.5
作者：
van Haarlem, M. P.;Wise, M. W.;van Zwieten, J.
通讯作者：
van Zwieten, J.