Giono, Gabriel, Roth, Lorenz ORCID: 0000-0003-0554-4691, Ivchenko, Nickolay ORCID: 0000-0003-2422-5426, Saur, Joachim ORCID: 0000-0003-1413-1231, Retherford, Kurt ORCID: 0000-0001-9470-150X, Schlegel, Stephan, Ackland, Marcus and Strobel, Darrell (2020). An Analysis of the Statistics and Systematics of Limb Anomaly Detections in HST/STIS Transit Images of Europa. Astron. J., 159 (4). BRISTOL: IOP PUBLISHING LTD. ISSN 1538-3881

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Abstract

Several recent studies derived the existence of plumes on Jupiter's moon Europa. The only technique that provided multiple detections is the far-ultraviolet imaging observations of Europa in transit of Jupiter taken by the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST). In this study, we reanalyze the three HST/STIS transit images in which Sparks et al. identified limb anomalies as evidence for Europa's plume activity. After reproducing the results of Sparks et al., we find that positive outliers are similarly present in the images as the negative outliers that were attributed to plume absorption. A physical explanation for the positive outliers is missing. We then investigate the systematic uncertainties and statistics in the images and identify two factors that are crucial when searching for anomalies around the limb. One factor is the alignment between the actual and assumed locations of Europa on the detector. A misalignment introduces distorted statistics, most strongly affecting the limb above the darker trailing hemisphere where the plumes were detected. The second factor is a discrepancy between the observation and the model used for comparison, adding uncertainty in the statistics. When accounting for these two factors, the limb minima (and maxima) are consistent with random statistical occurrence in a sample size given by the number of pixels in the analyzed limb region. The plume candidate features in the three analyzed images can be explained by purely statistical fluctuations and do not provide evidence for absorption by plumes.

Item Type: Journal Article
Creators:
CreatorsEmailORCIDORCID Put Code
Giono, GabrielUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Roth, LorenzUNSPECIFIEDorcid.org/0000-0003-0554-4691UNSPECIFIED
Ivchenko, NickolayUNSPECIFIEDorcid.org/0000-0003-2422-5426UNSPECIFIED
Saur, JoachimUNSPECIFIEDorcid.org/0000-0003-1413-1231UNSPECIFIED
Retherford, KurtUNSPECIFIEDorcid.org/0000-0001-9470-150XUNSPECIFIED
Schlegel, StephanUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Ackland, MarcusUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Strobel, DarrellUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
URN: urn:nbn:de:hbz:38-339558
DOI: 10.3847/1538-3881/ab7454
Journal or Publication Title: Astron. J.
Volume: 159
Number: 4
Date: 2020
Publisher: IOP PUBLISHING LTD
Place of Publication: BRISTOL
ISSN: 1538-3881
Language: English
Faculty: Unspecified
Divisions: Unspecified
Subjects: no entry
Uncontrolled Keywords:
KeywordsLanguage
WATER-VAPOR; SUBSURFACE OCEANS; GAS TORUS; ENCELADUS; ATMOSPHERE; ORIGIN; SATURN; PLUMEMultiple languages
Astronomy & AstrophysicsMultiple languages
URI: http://kups.ub.uni-koeln.de/id/eprint/33955

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