Detection of X-ray emission from <i>β</i> Pictoris with XMM-Newton:  a cool corona, a boundary layer or what?

Hempel, M.; Robrade, J.; Ness, J. U.; Schmitt, J. H. M. M.

doi:10.1051/0004-6361:20042596

Cited by 24 publications

(32 citation statements)

References 34 publications

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“…Usually, mid-A to mid-B type stars are known to be X-ray dark but β Pic shows some weak X-ray emission that could be coming from the thermal emission of a cool corona or from some remnant accretion onto the star (Günther et al 2012). Hempel et al (2005) estimates that an accretion rate between 2 × 10 18 kg/yr and 2 × 10 20 kg/yr can explain the X-ray observation, which fits our model predictions.…”

Section: Elementsupporting

confidence: 82%

A self-consistent model for the evolution of the gas produced in the debris disc of β Pictoris

Kral¹,

Wyatt²,

Carswell³

et al. 2016

Mon. Not. R. Astron. Soc.

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This paper presents a self-consistent model for the evolution of gas produced in the debris disc of β Pictoris. Our model proposes that atomic carbon and oxygen are created from the photodissociation of CO, which is itself released from volatile-rich bodies in the debris disc due to grain-grain collisions or photodesorption. While the CO lasts less than one orbit, the atomic gas evolves by viscous spreading resulting in an accretion disc inside the parent belt and a decretion disc outside. The temperature, ionisation fraction and population levels of carbon and oxygen are followed with the photodissociation region model Cloudy, which is coupled to a dynamical viscous α model. We present new gas observations of β Pic, of C I observed with APEX and O I observed with Herschel, and show that these along with published C II and CO observations can all be explained with this new model. Our model requires a viscosity α > 0.1, similar to that found in sufficiently ionised discs of other astronomical objects; we propose that the magnetorotational instability is at play in this highly ionised and dilute medium. This new model can be tested from its predictions for high resolution ALMA observations of C I. We also constrain the water content of the planetesimals in β Pic. The scenario proposed here might be at play in all debris discs and this model could be used more generally on all discs with C, O or CO detections.

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Section: Elementsupporting

confidence: 82%

A self-consistent model for the evolution of the gas produced in the debris disc of β Pictoris

Kral¹,

Wyatt²,

Carswell³

et al. 2016

Mon. Not. R. Astron. Soc.

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“…The two objects with the faintest X-ray sources are the AV5 star β Pictoris (HD 39060) and the AV7 star δ Doradus (HD 39014). In the case of β Pictoris the recorded ROSAT HRI signal is completely consistent with being due to UV contamination (Hempel et al 2005), in the case of δ Doradus this is extremely likely. Berghöfer et al (1999) derived a relation between the U, B and V magnitudes and the HRI count rates.…”

Section: Detection Rate Vs Spectral Typementioning

confidence: 53%

X-ray emission from A-type stars

Schröder¹,

Schmitt²

2007

A&A

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Being fully radiative, stars of spectral type A are not expected to harbor magnetic dynamos and hence such stars are not expected to produce X-ray emission. Indeed, while the X-ray detection rate of such stars in X-ray surveys is low, it is not zero and some of the brighter A-type stars have been detected on different occasions and with different instruments. To study systematically the puzzle of the X-ray emitting A-type stars, we carried out an X-ray study of all A-type stars listed in the Bright Star Catalogue using the ROSAT public data archive. We found a total of 312 bright A-type stars positionally associated with ROSAT X-ray sources; we analyzed the X-ray light curves as well as searched for evidence of RV variations to identify possible late-type companions producing the X-ray emission. In this paper we present a list of X-ray active A-type stars, including the collected data about multiplicity, X-ray luminosity and spectral peculiarities.

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“…For this A0 V star, Pease et al (2006) obtained L X < 3 × 10 25 erg s −1 from Chandra observations, corresponding to a bolometric fraction limit of L X /L bol < 9×10 −11 (see also Ayres 2008). The spectral type limit earlier than which A-stars begin to be plausibly X-ray dark, appears to be about A5 (e.g., Robrade & Schmitt 2010;Günther et al 2012), corresponding to the spectral type of β Pictoris, from which Günther et al (2012) recently confirmed the very weak X-ray emission tentatively identified by Hempel et al (2005). Evidence is also building that the magnetic A and late B stars might maintain significant X-ray output (e.g., Drake 1998; Robrade & Schmitt 2011;Stelzer et al 2011).…”

Section: Introductionmentioning

confidence: 69%

“…A tentative detection of the O vii emission was subsequently made from XMM-Newton observations, indicating a plasma temperature of 6 × 10 5 K (Hempel et al 2005). It was speculated that β Pic either has a cool corona or a boundary layer between the photosphere and its remnant disk (Hempel et al 2005). A deep Chandra observation of β Pic by Günther et al (2012) has succeeded in detecting the star with L X = 1.3 × 10 27 erg s −1 in the 0.06-2 keV band.…”

Section: Confronting Theory and Observationsmentioning

confidence: 99%

Burn Out or Fade Away? On the X-Ray and Magnetic Death of Intermediate Mass Stars

Drake

Braithwaite²,

Kashyap

et al. 2014

ApJ

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The nature of the mechanisms apparently driving X-rays from intermediate mass stars lacking strong convection zones or massive winds remains poorly understood, and the possible role of hidden, lower mass close companions is still unclear. A 20 ks Chandra HRC-I observation of HR 4796A, an 8 Myr old main sequence A0 star devoid of close stellar companions, has been used to search for a signature or remnant of magnetic activity from the Herbig Ae phase. X-rays were not detected and the X-ray luminosity upper limit was L X 1.3 × 10 27 erg s −1 . The result is discussed in the context of various scenarios for generating magnetic activity, including rotational shear and subsurface convection. A dynamo driven by natal differential rotation is unlikely to produce observable X rays, chiefly because of the difficulty in getting the dissipated energy up to the surface of the star. A subsurface convection layer produced by the ionization of helium could host a dynamo that should be effective throughout the main sequence but can only produce X-ray luminosities of the order 10 25 erg s −1 . This luminosity lies only moderately below the current detection limit for Vega. Our study supports the idea that X-ray production in Herbig Ae/Be stars is linked largely to the accretion process rather than the properties of the underlying star, and that early A stars generally decline in X-ray luminosity at least 100,000 fold in only a few million years.

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Detection of X-ray emission from β Pictoris with XMM-Newton: a cool corona, a boundary layer or what?

Cited by 24 publications

References 34 publications

A self-consistent model for the evolution of the gas produced in the debris disc of β Pictoris

A self-consistent model for the evolution of the gas produced in the debris disc of β Pictoris

X-ray emission from A-type stars

Burn Out or Fade Away? On the X-Ray and Magnetic Death of Intermediate Mass Stars

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