C.D.S. - SIMBAD4 rel 1.7 - 2021.03.03CET00:48:25

2007A&A...473..229R - Astronomy and Astrophysics, volume 473, 229-238 (2007/10-1)

X-rays from RU Lupi: accretion and winds in classical T Tauri stars.


Abstract (from CDS):

Low-mass stars are known to exhibit strong X-ray emission during their early evolutionary stages. This also applies to classical T Tauri stars (CTTS), whose X-ray emission differs from that of main-sequence stars in a number of aspects. We study the specific case of RU Lup, a well known accreting and wind-driving CTTS. In comparison with other bright CTTS we study possible signatures of accretion and winds in their X-ray emission. Using three XMM-Newton observations of RU Lup, we investigate its X-ray properties and their generating mechanisms. High-resolution X-ray spectra of RU Lup and other CTTS are compared to main-sequence stars. We examine the presence of a cool plasma excess and enhanced plasma density in relation to X-rays from accretion shocks and investigate anomalous strong X-ray absorption and its connection to winds or circumstellar material. We find three distinguishable levels of activity among the observations of RU Lup. While no large flares are present, this variability is clearly of magnetic origin due to the corresponding plasma temperatures of around 30MK; in contrast the cool plasma component at 2-3MK is quite stable over a month, resulting in a drop of average plasma temperature from 35MK down to 10MK. Density analysis with the OVII triplet indicates high densities in the cool plasma, suggesting accretion shocks to be a significant contributor to the soft X-ray emission. No strong overall metal depletion is observed, with Ne being more abundant than Fe, that is at solar value, and especially O. Excess emission at 6.4keV during the more active phase suggest the presence of iron fluorescence. Additionally RU Lup exhibits an extraordinary strong X-ray absorption, incompatible with estimates obtained at optical and UV wavelengths. Comparing spectra from a sample of main-sequence stars with those of accreting stars we find an excess of cool plasma as evidenced by lower OVIII/OVII line ratios in all accreting stars. High density plasma appears to be only present in low-mass CTTS, while accreting stars with intermediate masses (>2M) have lower densities. In all investigated CTTS the characteristics of the cooler X-ray emitting plasma are influenced by the accretion process. We suspect different accretion rates and amounts of funnelling, possibly linked to stellar mass and radius, to be mainly responsible for the different properties of their cool plasma component. The exceptional X-ray absorption in RU Lup and other CTTS is probably related to the accretion flows and an optically transparent wind emanating from the star or the disk.

Abstract Copyright:

Journal keyword(s): stars: individual: RU Lupi - stars: pre-main sequence - stars: activity - stars: coronae - X-rays: stars

Simbad objects: 9

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Number of rows : 9

N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 V* BP Tau Or* 04 19 15.8342975037 +29 06 26.929456808   13.13 12.12 11.89   K5/7Ve 613 0
2 V* T Tau TT* 04 21 59.4323326335 +19 32 06.439974179   11.22 10.12 9.80   K0IV/Ve 1336 1
3 V* DG Tau Or* 04 27 04.6913654419 +26 06 16.041555299 13.57 13.97 10.50 12.28   K6Ve 947 1
4 V* AB Aur Ae* 04 55 45.8459978418 +30 33 04.293281305 7.20 7.16 7.05 6.96 6.70 A0Ve 951 2
5 Hen 3-545 Or* 10 59 06.9712894449 -77 01 40.309036535   12.91 11.136   9.596 K4Ve 193 0
6 V* TW Hya TT* 11 01 51.9054298616 -34 42 17.031550898   11.94 10.50 10.626 9.18 K6Ve 1596 1
7 CPD-68 1894 TT* 13 22 07.5420267499 -69 38 12.216304202   11.38 10.393   9.117 K1Ve 133 0
8 V* RU Lup Or* 15 56 42.3109948086 -37 49 15.473469159 9.27 10.07 9.60     K7/M0e 399 0
9 HD 319139 LM* 18 14 10.4818974563 -32 47 34.516106830   11.47 10.68   9.11 K5+K7 306 0

    Equat.    Gal    SGal    Ecl

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