A survey for Fe 6.4 keV emission in young stellar objects   in
 $\mathsf{\rho}$ Oph: The strong fluorescence from Elias 29

Favata, F.; Micela, G.; Silva, B.; Sciortino, S.; Tsujimoto, Masahiro

doi:10.1051/0004-6361:20042019

Cited by 31 publications

(35 citation statements)

References 17 publications

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“…In this case, for favourable disk inclination angles (near face-on, i = 0 • -30 • ), W 6.4 keV varies approximately between 120 and 200 eV for an incident spectrum spectral index Γ = 2.3 to 1.3. This interpretation of the origin of the fluorescent Fe K emission was also proposed by Favata et al (2005b) for Elias 29, whose accretion disk was shown to be in a relatively face-on orientation (i < 60 • ) by Boogert et al (2002). This interpretation cannot, however, easily explain the current set of data.…”

Section: Discussionsupporting

confidence: 64%

“…Given that the thermal spectrum of stellar sources is generally steeper than a power-law spectrum with Γ ∼ 2.0 (e.g. Favata et al 2005b;Giardino et al 2007), photospheric emission can hardly explain the observed equivalent widths. George & Fabian (1991) show that higher equivalent widths for the fluorescent Fe K line can be obtained if the cold material is distributed in a centrally illuminated disk.…”

Section: Discussionmentioning

confidence: 99%

“…The typical equivalent width of the 6.4 keV emission line in the studies mentioned above is of the order of 150 eV and is too large to be explained with fluorescent emission in the stellar photosphere or in diffuse circumstellar material (e.g. Tsujimoto et al 2005;Favata et al 2005b). This scenario implies that the disk is "bathed" in high-energy X-rays emitted by the star, with significant astrophysical implications; for instance, X-rays, in addition to cosmic rays, would play an important role in photoionising the circumstellar material around young star and thus in coupling the gas to the ambient magnetic field (as suggested by e.g.…”

Section: Introductionmentioning

confidence: 94%

“…Tsujimoto et al (2005) has identified seven sources with an excess emission at 6.4 keV among 127 observations of YSOs within the COUP observation of Orion; Favata et al (2005b) report 6.4 keV fluorescent emission in Elias 29 in ρ-Oph both during quiescent and flaring emission, unlike all other reported detection of Fe fluorescent emission in YSOs that were made during intense flaring; Giardino et al (2007) have detected Fe 6.4 keV emission from a low-mass young star in Serpens, during an intense, long-duration flare. Recently, Czesla & Schmitt (2007) have reported intense Fe fluorescent emission in the spectrum of V 1486 Ori during a strong flare, when the plasma reached a temperature in excess of 10 keV.…”

Section: Introductionmentioning

confidence: 99%

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Results from Droxo

Giardino¹,

Favata

Pillitteri

et al. 2007

A&A

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Aims. We study the variability of the Fe 6.4 keV emission line from the Class I young stellar object Elias 29 in the ρ Oph cloud. Methods. We analysed the data from Elias 29 collected by XMM-Newton during a nine-day, nearly continuous observation of the ρ Oph star-forming region (the Deep Rho-Oph X-ray Observation, named droxo). The data were subdivided into six homogeneous time intervals, and the six resulting spectra were individually analysed. Results. We detect significant variability in the equivalent width of the Fe 6.4 keV emission line from Elias 29. The 6.4 keV line is absent during the first time interval of observation and appears at its maximum strength during the second time interval (90 ks after Elias 29 undergoes a strong flare). The X-ray thermal emission is unchanged between the two observation segments, while line variability is present at a 99.9% confidence level. Given the significant line variability in the absence of variations in the X-ray ionising continuum and the weakness of the photoionising continuum from the star's thermal X-ray emission, we suggest that the fluorescence may be induced by collisional ionisation from an (unseen) population of non-thermal electrons. We speculate on the possibility that the electrons are accelerated in a reconnection event of a magnetically confined accretion loop, connecting the young star to its circumstellar disk.

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Section: Discussionsupporting

confidence: 64%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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Results from Droxo

Giardino¹,

Favata

Pillitteri

et al. 2007

A&A

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“…A meaningful sample of CTTS fluorescent signatures is available , with several unexpected features deserving further study. Specifically, strong fluorescence in the Class I protostar Elias 29 (in the ρ Oph region) appears to be quasi-steady rather than related to strong X-ray flares (Favata et al 2005); even more perplexing, the 6.4 keV line is modulated on time scales of days regardless of the nearly constant stellar X-ray emission; it also does not react to the occurrence of appreciable X-ray flares in the light curve (Giardino et al 2007). The latter authors suggested that here we see 6.4 keV emission due to non-thermal electron impact in relatively dense, accreting magnetic loops.…”

Section: X-ray Fluorescencementioning

confidence: 98%

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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Results and perspectives of young stellar object long look programs

Sciortino¹

2008

Astron Nachr

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Both Chandra and XMM-Newton have performed long look programs for studying the YSO physics. I will discuss recent results on the controversial issue of Class 0 YSO X-ray emission, the observational evidence of magnetic funnels interconnecting the YSO with its circumstellar disk and the Fe 6.4 keV fluorescent line emission and its origin. While recent results of the XMM-Newton DROXO program challenge the "standard" interpretation of the Fe 6.4 kev line origin as due to photoionized fluorescing disk material, the discovery of X-ray excited Ne 12.81 µm line is a clear evidence of the interaction between X-rays and disk material. Future long look observations with XMM-Newton are required to clarify the X-ray effects on YSO disk.

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A survey for Fe 6.4 keV emission in young stellar objects in $\mathsf{\rho}$ Oph: The strong fluorescence from Elias 29

Cited by 31 publications

References 17 publications

Results from Droxo

Results from Droxo

Ionization and heating by X-rays and cosmic rays

Results and perspectives of young stellar object long look programs

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