Einstein X-ray survey of the Pleiades - The dependence of X-ray emission on stellar age

Micela, G.; Sciortino, S.; Serio, S.; Vaiana, G. S.; Bookbinder, Jay A.; Golub, L.; Harnden, F. R.; Rosner, R.

doi:10.1086/163143

Cited by 107 publications

(64 citation statements)

References 7 publications

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“…4, right panel) shows a dynamical range of three orders of magnitude. The cluster members are distributed in a sequence of values that goes from ρ Ophiuchi A+B and ρ Ophiuchi C (L X /L bol = 2×10 −6 and 4×10 −5 , respectively) to cooler objects which ratios peak at around 10 −3 , a value found among the most active and young coronae (Caillault & Helfand 1985;Micela et al 1985;Stauffer et al 1994). The origin of this value is debated but it could be a limit to the efficiency in the production of X-rays in dynamo driven coronae of active stars (Charbonneau & MacGregor 1992) or a breaking of magnetic loops in fast rotating stars (Jardine & Unruh 1999).…”

Section: X-ray Luminositiesmentioning

confidence: 99%

First stars of theρOphiuchi dark cloud

Pillitteri

Wolk

Chen

et al. 2016

A&A

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Star formation in molecular clouds can be triggered by the dynamical action of winds from massive stars. Furthermore, X-ray and UV fluxes from massive stars can influence the life time of surrounding circumstellar disks. We present the results of a 53 ks XMMNewton observation centered on the ρ Ophiuchi A+B binary system. ρ Ophiuchi lies in the center of a ring of dust, likely formed by the action of its winds. This region is different from the dense core of the cloud (L1688 Core F) where star formation is at work. X-rays are detected from ρ Ophiuchi as well as a group of surrounding X-ray sources. We detected 89 X-ray sources, 47 of them have at least one counterpart in 2MASS+All-WISE catalogs. Based on IR and X-ray properties, we can distinguish between young stellar objects (YSOs) belonging to the cloud and background objects. Among the cloud members, we detect three debris-disk objects and 22 disk-less − Class III young stars. We show that these stars have ages in 5−10 Myr, and are significantly older than the YSOs in L1688. We speculate that they are the result of an early burst of star formation in the cloud. An X-ray energy of ≥5 × 10 44 erg has been injected into the surrounding medium over the past 5 Myr, we discuss the effects of such energy budget in relation to the cloud properties and dynamics.

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Section: X-ray Luminositiesmentioning

confidence: 99%

First stars of theρOphiuchi dark cloud

Pillitteri

Wolk

Chen

et al. 2016

A&A

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“…The average L x decreases from ∼10 30 erg s −1 to ∼10 27 erg s −1 during the life of normal late-type stars (Micela et al 1985(Micela et al , 1988Guedel et al 1997;Feigelson & Montmerle 1999). This decrease mostly occurs between the zero-age main sequence (ZAMS) and the solar age, while it is nearly negligible during the pre-main sequence (PMS) phase.…”

Section: Introductionmentioning

confidence: 99%

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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“…Observed relations between coronal activity and rotation period in low-mass stars (Pallavicini et al 1981;Noyes et al 1984;Vilhu 1984;Micela et al 1985;Randich 2000;Montesinos et al 2001;Wright et al 2011;Vidotto et al 2014;Reiners et al 2014) have challenged theorists. A measure of activity is the total X-ray luminosity LX , expressed as…”

Section: Introductionmentioning

confidence: 99%

Explaining the observed relation between stellar activity and rotation

Blackman

Thomas

2014

Monthly Notices of the Royal Astronomical Society: Letters

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Observations of late-type main-sequence stars have revealed empirical scalings of coronal activity versus rotation period or Rossby number Ro (a ratio of rotation period to convective turnover time) which has hitherto lacked explanation. For Ro >> 1, the activity observed as X-ray to bolometric flux varies as Ro −q with 2 ≤ q ≤ 3, whilst |q| < 0.12 for Ro << 1. Here we explain the transition between these two regimes and the power law in the Ro >> 1 regime by constructing an expression for the coronal luminosity based on dynamo magnetic field generation and magnetic buoyancy. We explain the Ro << 1 behavior from the inference that observed rotation is correlated with internal differential rotation and argue that once the shear time scale is shorter than the convective turnover time, eddies will be shredded on the shear time scale and so the eddy correlation time actually becomes the shear time and the convection time drops out of the equations. We explain the Ro >> 1 behavior using a dynamo saturation theory based on magnetic helicity buildup and buoyant loss.

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Einstein X-ray survey of the Pleiades - The dependence of X-ray emission on stellar age

Cited by 107 publications

References 7 publications

First stars of theρOphiuchi dark cloud

First stars of theρOphiuchi dark cloud

The stellar content of the XMM-Newton bright serendipitous survey

Explaining the observed relation between stellar activity and rotation

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