2004A&A...419..653G


Query : 2004A&A...419..653G

2004A&A...419..653G - Astronomy and Astrophysics, volume 419, 653-665 (2004/5-4)

Chandra observation of an unusually long and intense X-ray flare from a young solar-like star in M78.

GROSSO N., MONTMERLE T., FEIGELSON E.D. and FORBES T.G.

Abstract (from CDS):

objS{EM* LkHA 312}{LkHα312} has been observed serendipitously with the ACIS-I detector on board the Chandra X-ray Observatory with a 26h continuous exposure. This Hα emission line star belongs to M78 (NGC2068), one of the star-forming regions of the Orion B giant molecular cloud at a distance of 400pc. From the optical and the near-infrared (NIR) data, we show that LkHα312 is a pre-main sequence (PMS) low-mass star with a weak NIR excess. This genuine T Tauri star displayed an X-ray flare with an unusually long rise phase (∼8 h). The X-ray emission was nearly constant during the first 18h of the observation, and then increased by a factor of 13 during a fast rise phase (∼2h), and reached a factor of 16 above the quiescent X-ray level at the end of a gradual phase (∼6h) showing a slower rise. To our knowledge this flare, with ∼0.4-0.5 cts/s, has the highest count rate observed so far with Chandra from a PMS low-mass star. By chance, the source position, 8.2' off-axis, protected this observation from pile-up. We make a spectral analysis of the X-ray emission versus time, showing that the plasma temperature of the quiescent phase and the flare peak reaches 29MK and 88MK, respectively. The quiescent and flare luminosities in the energy range 0.5-8keV corrected from absorption (NH≃1.7x1021cm–2) are 6x1030erg/s and ∼1032erg/s, respectively. The ratio of the quiescent X-ray luminosity on the LkHα312 bolometric luminosity is very high with log(LX/Lbol)= -2.9, implying that the corona of LkHα312 reached the ``saturation'' level. The X-ray luminosity of the flare peak reaches ∼2% of the stellar bolometric luminosity. The different phases of this flare are finally discussed in the framework of solar flares, which leads to the magnetic loop height from 3.1x1010 to 1011cm (0.2-0.5R*, i.e., 0.5-1.3R).

Abstract Copyright:

Journal keyword(s): Galaxy: open clusters and associations: individual: M78 (NGC2068) - X-rays: stars - stars: individual: LkHα312 - stars: flare - stars: pre-main sequence - infrared: stars

Simbad objects: 19

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Number of rows : 19
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 V* V693 Per Or* 03 44 16.4222464872 +32 09 55.247809434   15.91     12.801 K0 39 0
2 IC 348 OpC 03 44 32 +32 09.5           ~ 1327 1
3 HD 283447 Or* 04 14 12.9261150912 +28 12 12.359055168 13.17 12.07 10.68 9.45 8.67 K3Ve 398 0
4 NAME Orion Nebula Cluster OpC 05 35.0 -05 29           ~ 2190 1
5 V* V1321 Ori Or* 05 35 04.3009445808 -05 08 12.737523192   11.94 10.538   9.117 K0III 99 0
6 V* MT Ori Or* 05 35 17.9482748184 -05 22 45.477710148 14.524 13.208 12.229   10.063 K2 100 0
7 2MASS J05352365-0523319 Y*O 05 35 23.6546045328 -05 23 31.933929984   13.3 16.326   13.604 K5 29 0
8 NAME Horsehead Nebula DNe 05 40 59.0 -02 27 30           ~ 490 0
9 NAME Flame Nebula HII 05 41 42.7 -01 54 44           ~ 698 1
10 NAME Ori B MoC 05 41 43.0 -01 54 44           ~ 1291 0
11 LDN 1630 DNe 05 45.5 -00 59           ~ 373 0
12 HD 38563 ** 05 46 44.658 +00 05 22.78 12.02 11.79 10.81 10.25   B2II-III 41 1
13 M 78 RNe 05 46 45.8 +00 04 45   8.0       ~ 366 0
14 EM* LkHA 309 TT* 05 47 06.9688378728 +00 00 47.643863076     14.7     K4.5 24 0
15 2MASS J05470868+0000140 TT* 05 47 08.6992836504 +00 00 13.945803012           M3 5 0
16 EM* LkHA 313 TT* 05 47 13.84752 +00 00 17.0532       14.70   M1 16 0
17 EM* LkHA 312 Y*O 05 47 14.0932945704 +00 00 15.668906436     15.1     ~ 19 0
18 NAME Ophiuchus Molecular Cloud SFR 16 28 06 -24 32.5           ~ 3416 1
19 EM* SR 13 Or* 16 28 45.2768168328 -24 28 18.905579112     13.60 12.40 10.9 M2e 127 0

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2022.11.28-09:15:26

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