2007
DOI: 10.1086/510776
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AChandraSearch for Coronal X‐Rays from the Cool White Dwarf GD 356

Abstract: We report observations with the Chandra X-ray Observatory of the single, cool, magnetic white dwarf GD 356. For consistent comparison with other X-ray observations of single white dwarfs, we also re-analyzed archival ROSAT data for GD 356 (GJ 1205), G99-47 (GR 290 = V1201 Ori), GD 90, G195-19 (EG 250 = GJ 339.1), and WD 2316+123, and archival Chandra data for LHS 1038 (GJ 1004) and GD 358 (V777 Her). Our Chandra observation detected no X-rays from GD 356, setting the most restrictive upper limit to the X-ray l… Show more

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Cited by 108 publications
(113 citation statements)
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“…In order to estimate detection significance ( C ) or false detection probability ( P r = 1 − C ) independently of the source search routines, we employ a Bayesian approach by Weisskopf et al () and Kashyap et al (), which provide a more rigorous treatment of discrete Poisson distributions than simple‐minded approaches using signal‐to‐noise ratio (SNR). In Appendix , we describe a simplified version of the Bayesian approach used for calculating the detection significance and compare it with the SNR‐based analysis.…”
Section: Resultsmentioning
confidence: 99%
“…In order to estimate detection significance ( C ) or false detection probability ( P r = 1 − C ) independently of the source search routines, we employ a Bayesian approach by Weisskopf et al () and Kashyap et al (), which provide a more rigorous treatment of discrete Poisson distributions than simple‐minded approaches using signal‐to‐noise ratio (SNR). In Appendix , we describe a simplified version of the Bayesian approach used for calculating the detection significance and compare it with the SNR‐based analysis.…”
Section: Resultsmentioning
confidence: 99%
“…P B is proportional to the probability that a source is spurious due to a background fluctuation (see Appendix A2 of Weisskopf et al 2007).…”
Section: Chandra Acis Imaging Observationsmentioning
confidence: 99%
“…In each energy band, we then calculated the S/N of the photometric measurements from the probability that the source could be generated by a noise fluctuation of the local background using the following equation from Weisskopf et al (2007): . Using this probability, we defined the S/N as the equivalent Gaussian significance in units of the standard deviation (e.g., = P 0.0013 corresponds to S/N=3σ).…”
Section: Net Counts and Source Significancementioning
confidence: 99%
“…These photon flux measurements assume a quantum efficiency of 1; this is a decent approximation for the NuSTAR CdZnTe detectors, which have a quantum efficiency of 0.98 over the vast majority of the NuSTAR energy range (Bhalerao 2012). If the significance of a source in a particular observation was s <1 , then we calculated a 90% confidence upper limit to its photon flux by converting the probability distribution of true source counts (from Equation (A21) in Weisskopf et al 2007) to a photon flux distribution using the source region effective area.…”
Section: Photon and Energy Fluxesmentioning
confidence: 99%
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