The eROSITA Final Equatorial-Depth Survey (eFEDS)

Boller, Th.; Schmitt, J. H. M. M.; Buchner, Johannes; Freyberg, M. J.; Georgakakis, A.; Liu, T.; Robrade, J.; Merloni, A.; Nandra, K.; Malyali, A.; Krumpe, M.; Salvato, M.; Dwelly, T.

doi:10.1051/0004-6361/202141155

Cited by 13 publications

(12 citation statements)

References 29 publications

(30 reference statements)

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“…A systematic analysis of the variability of all sources detected in the eFEDS field is presented by Boller et al (2022). This variability study refers to all objects in the official eFEDS source catalog, which comprises our 14 detected M dwarfs.…”

Section: Light-curve Analysismentioning

confidence: 99%

“…This variability study refers to all objects in the official eFEDS source catalog, which comprises our 14 detected M dwarfs. We extracted the variability metrics for these 14 stars from the catalog of Boller et al (2022). Specifically, this catalog provides the normalized excess variance (NEV) as defined by Boller et al (2016) and its uncertainty.…”

Section: Light-curve Analysismentioning

confidence: 99%

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First eROSITA study of nearby M dwarfs and the rotation-activity relation in combination with TESS

Magaudda

Stelzer

Raetz

et al. 2022

A&A

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We present the first results with the ROentgen Survey with an Imaging Telescope Array (eROSITA) on board the Russian Spektrum-Roentgen-Gamma mission, and we combine the new X-ray data with observations with the Transiting Exoplanet Survey Satellite (TESS). We used the SUPERBLINK proper motion catalog of nearby M dwarfs as input sample to search for eROSITA and TESS data. We extracted Gaia DR2 data for the full M dwarf catalog, which comprises ~9000 stars, and we calculated the stellar parameters from empirical relations with optical/IR colors. Then we cross-matched this catalog with the eROSITA Final Equatorial Depth Survey (eFEDS) and the first eROSITA all-sky survey (eRASS1). After a meticulous source identification in which we associated the closest Gaia source with the eROSITA X-ray detections, our sample of M dwarfs is defined by 687 stars with SpT = K5..M7 (673 from eRASS1 and 14 from eFEDS). While for eRASSl we used the data from the source catalog provided by the eROSITA_DE consortium, for the much smaller eFEDS sample, we performed the data extraction, and we analyzed the X-ray spectra and light curves. This unprecedented data base for X-ray emitting M dwarfs allowed us to place a quantitative constraint on the mass dependence of the X-ray luminosity, and to determine the change in the activity level with respect to pre-main-sequence stars. TESS observations are available for 489 of 687 X-ray detected M dwarfs. By applying standard period search methods, we were able to determine the rotation period for 180 X-ray detected M dwarfs. This is about one-forth of the X-ray sample. With the joint eROSITA and TESS sample, and combining it with our compilation of historical X-ray and rotation data for M dwarfs, we examined the mass dependence of the saturated regime of the rotation-activity relation. A first comparison of eROSITA hardness ratios and spectra shows that 65% of the X-ray detected M dwarfs have coronal temperatures of ~0.5 keV. We performed a statistical investigation of the long-term X-ray variability of M dwarfs by comparing the eROSITA measurements to those obtained ~30 yr earlier during the ROSAT all-sky survey (RASS). Evidence for X-ray flares is found in various parts of our analysis: directly from an inspection of the eFEDS light curves, in the relation between RASS and eRASSl X-ray luminosities, and in a subset of stars that displays hotter X-ray emission than the bulk of the sample according to the hardness ratios. Finally, we point out the need to obtain X-ray spectroscopy for more M dwarfs to study the coronal temperature-luminosity relation, which is not well constrained by our eFEDS results.

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Section: Light-curve Analysismentioning

confidence: 99%

Section: Light-curve Analysismentioning

confidence: 99%

First eROSITA study of nearby M dwarfs and the rotation-activity relation in combination with TESS

Magaudda

Stelzer

Raetz

et al. 2022

A&A

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“…13 to the intrinsic flux variability of AGN. This effect is discussed further in Boller et al (2022).…”

Section: Aperture Photometry and Number Countsmentioning

confidence: 90%

“…The calculation of fluxes for the eFEDS and XMM-ATLAS fields was based on aperture photometry and used the Bayesian method described by Laird et al (2009) and Georgakakis & Nandra (2011). A description of the basic flux-estimation algorithm is also provided in Boller et al (2022). The fluxes in both samples are estimated in the 0.5-2 keV spectral band assuming a power-law spectral model with Γ = 1.4 that is absorbed by a Galactic column density of log N H /cm −2 = 20.3.…”

Section: Aperture Photometry and Number Countsmentioning

confidence: 99%

“…In a series of accompanying papers, we will present the identification of the multiwavelength counterparts of point-like (Salvato et al 2022;Schneider et al 2022) and extended (Klein et al 2022) X-ray sources; the resulting clean catalogues of clusters of galaxies (Liu et al 2022a;Bulbul et al 2022), active galactic nuclei (AGN) (Liu et al 2022b;Nandra et al, in prep. ) and stars (Schneider et al 2022); the X-ray variability properties of the detected sources (Boller et al 2022;Buchner et al 2022); the X-ray spectral analysis of the point sources (Liu et al 2022b); the X-ray morphological analysis of the clusters (Ghirardini et al 2022); the optical and lensing analysis of the X-ray clusters (Ramos-Ceja et al 2022;Chiu et al 2022;Bahar et al 2022, Ota et al, in prep. ); the properties of non-active galaxies detected by eROSITA (Vulic et al 2022), and the discovery of some extreme AGN (Toba et al 2022;Brusa et al 2022).…”

Section: Introductionmentioning

confidence: 99%

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The eROSITA Final Equatorial Depth Survey (eFEDS)

Brunner

Liu

Lamer

et al. 2022

A&A

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219

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Context. The eROSITA X-ray telescope on board the Spectrum-Poentgen-Gamma (SPG) observatory combines a large field of view and a large collecting area in the energy range between ~0.2 and ~8.0 keV. This gives the telescope the capability to perform uniform scanning observations of large sky areas. Aims. SRG/eROSITA performed scanning observations of the ~140 square degree eROSITA Final Equatorial Depth Survey field (the eFEDS field) as part of its performance verification phase ahead of the planned four year of all-sky scanning operations. The observing time of eFEDS was chosen to slightly exceed the depth expected in an equatorial field after the completion of the all-sky survey. While verifying the capability of eROSITA to perform large-area uniform surveys and saving as a test and training dataset to establish calibration and data analysis procedures, the eFEDS survey also constitutes the largest contiguous soft X-ray survey at this depth to date, supporting a range of early eROSITA survey science investigations. Here we (i) present a catalogue of detected X-ray sources in the eFEDS field providing information about source positions and extent, as well as fluxes in multiple energy bands, and (ii) document the suite of tools and procedures developed for eROSITA data processing and analysis, which were validated and optimised by the eFEDS work. Methods. The data were fed through a standard data processing pipeline, which appltes X-ray event calibration and provides a set of standard calibrated data products. A mutiti-stage source detection procedure, building in part on experience from XMM-Newton, was optimised and calibrated by performing realistic simulations of the eROSITA eFEDS observations. Source fluxes were computed in multiple standard energy bands by forced point source fitting and aperture photometry. We cross-matched the eROSITA eFEDS source catalogue with previous XMM-ATLAS observations, which confirmed the excellentt agreement of the eROSITA and XMM-ATLAS source fluxes. Astrometric corrections were performed by cross-matching the eROSITA source positions with an optical reference catalogue of quasars. Results. We present a primary catalogue of 27 910 X-ray sources (542 of which are significantly spatially extended) detected in the 0.2–2.3 keV energy range with detection likelihoods ≥6, corresponding to a (point source) flux limit of 6.5 × 10–15 erg cm–2 s–1 in the 0.5–2.0 keV energy band (80% completeness). A supplementary catalogue contains 4774 low-significance source candidates with detection likelihoods between 5 and 6. In addition, a hard-band sample of 246 sources detected in the energy range 22.3–5.0 keV above a detection likelihood of 10 is provided. In an appendix, we finally describe the dedicated data analysis software package, the eROSITA calibration database, and the standard calibrated data products.

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Systematic evaluation of variability detection methods for eROSITA

Buchner

Böller

Bogensberger

et al. 2022

A&A

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The reliability of detecting source variability in sparsely and irregularly sampled X-ray light curves is investigated. This is motivated by the unprecedented survey capabilities of eROSITA on board the Spektrum-Roentgen-Gamma (SRG) observatory, providing light curves for many thousand sources in its nal-depth equatorial deep-eld survey. Four methods for detecting variability are evaluated: excess variance, amplitude maximum deviations, Bayesian blocks, and a new Bayesian formulation of the excess variance. We judge the false-detection rate of variability based on simulated Poisson light curves of constant sources, and calibrate signicance thresholds. Simulations in which ares are injected favour the amplitude maximum deviation as most sensitive at low false detections. Simulations with white and red stochastic source variability favour Bayesian methods. The results are applicable also for the million sources expected in the eROSITA all-sky survey.

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The eROSITA Final Equatorial-Depth Survey (eFEDS)

Cited by 13 publications

References 29 publications

First eROSITA study of nearby M dwarfs and the rotation-activity relation in combination with TESS

First eROSITA study of nearby M dwarfs and the rotation-activity relation in combination with TESS

The eROSITA Final Equatorial Depth Survey (eFEDS)

Systematic evaluation of variability detection methods for eROSITA

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