2017A&A...599A..47O


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.13CEST00:41:43

2017A&A...599A..47O - Astronomy and Astrophysics, volume 599A, 47-47 (2017/3-1)

Detection of thermal radio emission from a single coronal giant.

O'GORMAN E., HARPER G.M. and VLEMMINGS W.

Abstract (from CDS):

We report the detection of thermal continuum radio emission from the K0 III coronal giant Pollux (β Gem) with the Karl G. Jansky Very Large Array (VLA). The star was detected at 21 and 9GHz with flux density values of 150±21 and 43±8µJy, respectively. We also place a 3σrms upper limit of 23µJy for the flux density at 3GHz. We find the stellar disk-averaged brightness temperatures to be approximately 9500, 15000, and <71000K, at 21, 9, and 3GHz, respectively, which are consistent with the values of the quiet Sun. The emission is most likely dominated by optically thick thermal emission from an upper chromosphere at 21 and 9GHz. We discuss other possible additional sources of emission at all frequencies and show that there may also be a small contribution from gyroresonance emission above active regions, coronal free-free emission and free-free emission from an optically thin stellar wind, particularly at the lower frequencies. We constrain the maximum mass-loss rate from Pollux to be less than 3.7x10–11M/yr (assuming a wind terminal velocity of 215km/s), which is about an order of magnitude smaller than previous constraints for coronal giants and is in agreement with existing predictions for the mass-loss rate of Pollux. These are the first detections of thermal radio emission from a single (i.e., non-binary) coronal giant and demonstrate that low activity coronal giants like Pollux have atmospheres at radio frequencies akin to the quiet Sun.

Abstract Copyright: © ESO, 2017

Journal keyword(s): stars: atmospheres - radio continuum: stars - stars: chromospheres - stars: coronae - stars: evolution - stars: mass-loss - stars: mass-loss

Simbad objects: 8

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Number of rows : 8

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 * eta Cas PM* 00 49 06.2907161 +57 48 54.675740 4.04 4.02 3.44 2.94 2.58 F9V+M0-V 598 0
2 * tau Cet PM* 01 44 04.0834226 -15 56 14.926552 4.43 4.22 3.50 2.88 2.41 G8V 1091 1
3 * omi02 Eri Fl* 04 15 16.3197260 -07 39 10.338087 5.69 5.25 4.43 3.74 3.29 K0V 742 0
4 * alf Aur SB* 05 16 41.35871 +45 59 52.7693 1.33 0.88 0.08 -0.52 -0.96 G3III: 1137 0
5 * alf CMi SB* 07 39 18.11950 +05 13 29.9552 0.82 0.79 0.37 -0.05 -0.28 F5IV-V+DQZ 1758 0
6 ICRF J074110.7+311200 Sy1 07 41 10.7033434 +31 12 00.231016   17.02 16.89 16.322   ~ 410 1
7 * bet Gem PM* 07 45 18.94987 +28 01 34.3160 3.00 2.14 1.14 0.39 -0.11 K0IIIb 1046 1
8 3C 286 Sy1 13 31 08.2885060664 +30 30 32.960825108   17.51 17.25     ~ 3716 1

    Equat.    Gal    SGal    Ecl

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2020.07.13-00:41:43

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