ROSAT X-ray sources embedded in the rho Ophiuchi cloud core

Casanova, S.; Montmerle, T.; Feigelson, E. D.; André, P.

doi:10.1086/175214

Cited by 145 publications

(178 citation statements)

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“…/L bol D 10~4 quiescent phases of class II]IIIs (Feigelson et al 1993 ;Casanova et al 1995 ;. Class on I]I c s, the other hand, show signiÐcantly lower values in L X /L bol both the Ñare and quiescent phases than those of class II]IIIs.…”

Section: X-rays From Brown Dwarfsmentioning

confidence: 91%

“…i See Table 3. We also search for counterparts in the previous X-ray surveys with ROSAT PSPC (Casanova et al 1995), ROSAT HRI Grosso 2001), and ASCA (Kamata et al 1997 ;Tsuboi et al 2000) and Ðnd only 22 sources in these surveys (cols.…”

Section: Source Classiðcationmentioning

confidence: 99%

“…X-rays from class I sources (the late phase of protostars) have been reported in deep ASCA and ROSAT images of the o Ophiuchi cloud (Koyama et al 1994 ;Casanova et al 1995 ;Kamata et al 1997 ;Grosso et al 1997Carkner, Kozak, & Feigelson 1998 ;Tsuboi 1999 ;Tsuboi et al 2000 ;Grosso 2001). However, possible contamination from nearby TTSs (or others) would not be removed with the limited spatial resolution of ASCA.…”

Section: Introductionmentioning

confidence: 99%

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ChandraObservation of the ρ Ophiuchi Cloud

Imanishi

Koyama

Tsuboi

2001

ApJ

193

285

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We observed a 17@ ] 17@ region of the o Oph molecular cloud, using the ACIS-I array on board the Chandra X-Ray Observatory. A 100 ks exposure observation revealed D100 X-ray sources above the detection limit of D1028 ergs s~1. About two-thirds of the X-ray sources are identiÐed with an optical and/or IR counterpart, including signiÐcant numbers of class I, II, and III sources and a few brown dwarfs. The X-ray detection rate of class I sources is a surprisingly high 70%. Many X-ray Ñares, possibly because of the magnetic activity, are found from all of the classes. We make systematic spectral studies of the quiescent and Ñare X-rays for all the X-ray sources. The X-ray temperatures and absorptions of class I sources are generally larger than those of class II and III sources. In addition, X-ray Ñares from class I sources show slightly higher duty ratio, temperature, and luminosity than those of more evolved classes. We further give brief results on brown dwarfs, sources in a younger phase than class I, unclassiÐed, and unidentiÐed sources. Details for several selected young stellar objects, including the Ðrst detection of a neutral iron line (6.4 keV) from a class I source (YLW 16A), are separately addressed.

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Section: X-rays From Brown Dwarfsmentioning

confidence: 91%

Section: Source Classiðcationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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ChandraObservation of the ρ Ophiuchi Cloud

Imanishi

Koyama

Tsuboi

2001

ApJ

193

285

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“…X-rays also heat the upper disk layers and thus induce photoevaporative flows eventually leading to disk dispersal and quenching of planet formation. The importance of stellar X-rays was recognized when X-ray surveys of star-forming regions systematically indicated high X-ray luminosities in T Tauri stars, and partly rather hard spectral energy distributions (Casanova et al 1995). We discuss ionization, heating and chemical driving separately although all processes occur together and are strongly interlinked, as discussed in the sections above.…”

Section: Applications To Protoplanetary Disksmentioning

confidence: 97%

Ionization and heating by X-rays and cosmic rays

Güdel

2015

EPJ Web of Conferences

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Abstract. High-energy radiation from the central T Tauri and protostars plays an important role in shaping protoplanetary disks and influences their evolution. Such radiation, in particular X-rays and extreme-ultraviolet (EUV) radiation, is predominantly generated in unstable stellar magnetic fields (e.g., the stellar corona), but also in accretion hot spots. Even jets may produce X-ray emission. Cosmic rays, i.e., high-energy particles either from the interstellar space or from the star itself, are of crucial importance. Both highenergy photons and particles ionize disk gas and lead to heating. Ionization and heating subsequently drive chemical networks, and the products of these processes are accessible through observations of molecular line emission. Furthermore, ionization supports the magnetorotational instability and therefore drives disk accretion, while heating of the disk surface layers induces photoevaporative flows. Both processes are crucial for the dispersal of protoplanetary disks and therefore critical for the time scales of planet formation. This chapter introduces the basic physics of ionization and heating starting from a quantum mechanical viewpoint, then discusses relevant processes in astrophysical gases and their applications to protoplanetary disks, and finally summarizes some properties of the most important high-energy sources for protoplanetary disks.

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“…Surface density Σ(r, z) is determined by integration of hydrostatic density profile (28) from z to z 0 ≫ z. We vary X-rays luminosities in the range L XR = 10 29 − 10 32 erg s −1 according to observations (Casanova et al 1995). We use following ionization parameters as a fiducial: a d = 0.1 µm, ξ 0 = 10 −17 s −1 , L XR = 10 30 erg s −1 .…”

Section: Ionization Fractionmentioning

confidence: 99%

Fossil magnetic field of accretion disks of young stars

Dudorov

Khaibrakhmanov

2014

Astrophys Space Sci

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We elaborate the model of accretion disks of young stars with the fossil large-scale magnetic field in the frame of Shakura and Sunyaev approximation. Equations of the MHD model include Shakura and Sunyaev equations, induction equation and equations of ionization balance. Magnetic field is determined taking into account ohmic diffusion, magnetic ambipolar diffusion and buoyancy. Ionization fraction is calculated considering ionization by cosmic rays and X-rays, thermal ionization, radiative recombinations and recombinations on the dust grains.Analytical solution and numerical investigations show that the magnetic field is coupled to the gas in the case of radiative recombinations. Magnetic field is quasi-azimuthal close to accretion disk inner boundary and quasi-radial in the outer regions.Magnetic field is quasi-poloidal in the dusty "dead" zones with low ionization degree, where ohmic diffusion is efficient. Magnetic ambipolar diffusion reduces vertical magnetic field in 10 times comparing to the frozenin field in this region. Magnetic field is quasi-azimuthal close to the outer boundary of accretion disks for standard ionization rates and dust grain size a d = 0.1 µm. In the case of large dust grains (a d > 0.1 µm) or enhanced ionization rates, the magnetic field is quasiradial in the outer regions.It is shown that the inner boundary of dusty "dead" zone is placed at r = (0.1 − 0.6) AU for accretion disks of stars with M = (0.5 − 2) M ⊙ . Outer boundary of "dead" zone is placed at r = (3 − 21) AU and it is determined by magnetic ambipolar diffusion. Mass of solid material in the "dead" zone is more than 3 M ⊕ for stars with M ≥ 1 M ⊙ .

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ROSAT X-ray sources embedded in the rho Ophiuchi cloud core

Cited by 145 publications

References 0 publications

ChandraObservation of the ρ Ophiuchi Cloud

ChandraObservation of the ρ Ophiuchi Cloud

Ionization and heating by X-rays and cosmic rays

Fossil magnetic field of accretion disks of young stars

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