Stellar X‐ray surveys and Galaxy structure

Micela, G.

doi:10.1002/asna.200310020

Cited by 3 publications

(6 citation statements)

References 16 publications

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“…In contrast, the analysis of the Chandra Deep Field-North (CDF-N, Brandt et al 2001) shows a lack of F, G, and K dwarfs compared to the predictions (Feigelson et al 2004). The number of dM stars agrees very well with what is predicted by the model, but there is an excess of dF, dG, and dK stars in the predictions (Micela 2003;Feigelson et al 2004). The observed lack of yellow stars is in the opposite direction of the discrepancy obtained with the EMSS, although it must be noticed that the CDF-N is dominated by old-disk stars, while young (PMS and ZAMS) stars are dominant in the EMSS.…”

Section: Introductionsupporting

confidence: 81%

“…An excess of yellow stars is also observed in other shallow surveys (Favata et al 1988;Micela 2003), which cannot be reproduced by Galactic models using smooth shapes of the SFR. In particular, Favata et al (1993) and Sciortino et al (1995) confirm the excess of yellow stars in the Extended Medium Sensitivity Survey of Einstein (EMSS, Gioia et al 1990) as being due to young stars.…”

Section: Xcount Model Resultsmentioning

confidence: 71%

“…Guillout et al 1996;Haywood et al 1997) would account for the lack of old sources in medium and deep surveys. In this context, Chandra and XMM-Newton surveys could be able to discriminate between these two possible scenarios, thanks to their high sensitivity (Micela 2003).…”

Section: Introductionmentioning

confidence: 99%

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The stellar content of the XMM-Newton bright serendipitous survey

López‐Santiago¹,

Micela²,

Sciortino³

et al. 2006

A&A

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Context. The comparison of observed counts in a given sky direction with predictions by Galactic models yields constraints on the spatial distribution and the stellar birthrate of young stellar populations. The XMM-Newton Bright Serendipitous Survey (XBSS) is an unbiased survey that includes a total of 58 stellar sources selected in the 0.5-4.5 keV energy band, having a limiting sensitivity of 10 −2 cnt s −1 and covering an area of 28.10 sq deg. Aims. We present the results of analysing the stellar content of the XBSS so as to understand the recent star formation history of the Galaxy in the vicinity of the Sun. Methods. We compared the observations with the predictions obtained with XCOUNT, a model of the stellar X-ray content of the Galaxy. The model predicts the number and properties of the stars to be observed in terms of magnitude, colour, population and f x / f v ratio distributions of the coronal sources detected with a given instrument and sensitivity in a specific sky direction. Results. As in other shallow surveys, we observe an excess of stars not predicted by our Galaxy model. Comparing the colours of the identified infrared counterparts with the model predictions, we observe that this excess is produced by yellow (G+K) stars. The study of the X-ray spectrum of each source reveals a main population of stars with the coronal temperature stratification typical of intermediate-age stars. As no assumptions have been made for the selection of the sample, our results must be representative of the entire solar neighbourhood. Some stars show infrared excess due to circumstellar absorption, which is indicative of youth.

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Section: Introductionsupporting

confidence: 81%

Section: Xcount Model Resultsmentioning

confidence: 71%

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The stellar content of the XMM-Newton bright serendipitous survey

López‐Santiago¹,

Micela²,

Sciortino³

et al. 2006

A&A

Self Cite

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“…This is not the case, and on the contrary, the observed dM stars appear to be in "perfect" agreement with the model in most of the X-ray surveys (see e.g. Micela 2003) and the discrepancy is always concentrated among yellow stars, with an observed excess in shallow surveys and a lack in deep surveys (Feigelson et al 2003).…”

Section: Comparison With the Observationsmentioning

confidence: 94%

“…The EMSS (and most of the RASS) is quite shallow and, as discussed above, detected preferentially young stars, while Chandra and XMM/Newton surveys, being very sensitive, will be dominated by old stars (Micela 2003). The NEP survey with its moderately deep sensitivity, (fluxes ∼10 −14 erg cm −2 s −1 ) is able to sample the intermediateage (10 8 -10 9 years) population.…”

Section: Introductionmentioning

confidence: 98%

The stellar population of the Rosat North Ecliptic Pole survey

Micela

Affer

Favata

et al. 2006

A&A

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Context. X-ray surveys are a very efficient mean of detecting young stars and therefore allow us to study the young stellar population in the solar neighborhood and the local star formation history in the last billion of years. Aims. We want to study the young stellar population in the solar neighborhood, to constrain its spatial density and scale height as well as the recent local star formation history. Methods. We analyze the stellar content of the ROSAT North Ecliptic Pole survey, and compare the observations with the predictions derived from stellar galactic model. Since the ROSAT NEP survey is sensitive at intermediate fluxes is able to sample both the youngest stars and the intermediate age stars (younger than 10 9 years), linking the shallow and deep flux surveys already published in the literature. Results. We confirm the existence of an excess of yellow stars in our neighborhood previously seen in shallow survey, which is likely due to a young star population not accounted for in the model. However the excellent agreement between observations and predictions of dM stars casts some doubt on the real nature of this active population.

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WFXT studies of the stellar populations in the Galaxy

Sciortino¹

2010

Preprint

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Stellar X‐ray surveys and Galaxy structure

Cited by 3 publications

References 16 publications

The stellar content of the XMM-Newton bright serendipitous survey

The stellar content of the XMM-Newton bright serendipitous survey

The stellar population of the Rosat North Ecliptic Pole survey

WFXT studies of the stellar populations in the Galaxy

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