2019A&A...627A.128S


Query : 2019A&A...627A.128S

2019A&A...627A.128S - Astronomy and Astrophysics, volume 627A, 128-128 (2019/7-1)

Classification of low-luminosity stellar X-ray sources in the field of the Draco dwarf spheroidal galaxy.

SAEEDI S., SASAKI M., STELZER B. and DUCCI L.

Abstract (from CDS):

Aims. A previous study of the X-ray luminosity function of the X-ray sources in the Draco dwarf spheroidal (dSph) galaxy field indicates the presence of a population of unknown X-ray sources in the soft energy range of 0.5-2keV. In 2015, there were twenty-six further deep XMM-Newton observations of Draco dSph, providing an opportunity for a new study of the as yet unclassified sources. Methods. We applied the classification criteria presented in our previous multi-wavelength study of the X-ray sources of the Draco dSph to the sources detected in the combined 2009 and 2015 XMM-Newton data set. These criteria are based on X-ray studies and properties of the optical, near-infrared, and mid-infrared counterparts and allows us to distinguish background active galactic nuclei (AGNs) and galaxies from other types of X-ray sources. In this work we performed X-ray spectral and timing analyses for fifteen sources in the field of Draco dSph with stellar counterparts. Results. We present the classification of X-ray sources, for which the counterpart is identified as a stellar object based on our criteria from multi-wavelength data. We identify three new symbiotic stars in the Draco dSph with X-ray luminosities between ∼3.5x1034erg/s and 5.5x1034erg/s. The X-ray spectral analysis shows that two of the classified symbiotic stars are β-type. This is the first identification of this class of symbiotic stars in a nearby galaxy. Eight sources are classified as Galactic M dwarfs in the field of the Draco dSph. These M dwarfs are between ∼140 and 800pc distant, with X-ray luminosities are between 1028 and 1029erg/s and logarithmic ratios of X-ray to bolometric luminosity, log(LX/Lbol), between -3.4 and -2.1. The multiple observations allowed us to investigate flare activity of the M dwarfs. For 5 M dwarfs flare(s) are observed with a significance of >3σ level of confidence. Moreover, we classified three foreground sources, located at distances of the order of ∼1-3kpc in the field of the Draco dSph. Based on both the X-ray luminosities of these foreground sources (>1030erg/s) and their optical counterparts (late type G or K stars), these X-ray sources are classified as candidates of contact binary systems. Conclusions. Our study of X-ray sources of the Draco dSph shows that accreting white dwarfs are the most promising X-ray population of dSphs, which is in line with theoretical expectations. The number of Galactic M dwarfs detected at our X-ray sensitivity limit is consistent with the expectation based on the space density of M dwarfs.

Abstract Copyright: © ESO 2019

Journal keyword(s): galaxies: dwarf - X-rays: galaxies - X-rays: binaries - X-rays: stars - binaries: symbiotic - stars: mass-loss

Simbad objects: 21

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Number of rows : 21
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 CD-28 3719 Sy* 07 01 09.1555114272 -29 06 25.046471988   12.10 10.59     S6,8e 22 0
2 WRAY 15-619 Sy* 10 39 08.6786794704 -51 24 12.651866460     12.26     M7 22 0
3 * 4 Dra SB* 12 30 06.6619965864 +69 12 03.974236920 8.38 6.57 4.95     M3+IIIa 126 0
4 V* RT Cru Sy* 12 34 53.7361211904 -64 33 56.099018448   12.20 11.35 12.09   M4/5e 82 0
5 V* T CrB Sy* 15 59 30.1622265912 +25 55 12.613382940   11.516 10.247 9.70   M3IIIe_sh 674 0
6 2MASS J17191999+5759430 * 17 19 19.9943172120 +57 59 43.111532364   19.042 18.412 17.731 17.148 ~ 9 0
7 2MASS J17192058+5751203 * 17 19 20.6024376192 +57 51 20.227227912     16.379   15.544 ~ 2 0
8 [BFO2002] Dra 50105 V* 17 19 27.2562092568 +58 00 34.494497352     18.961   16.700 M2 3 0
9 3XMM J171943.6+574207 X 17 19 43.67 +57 42 07.2           ~ 1 0
10 [ALS82] C1 Sy* 17 19 57.6571766280 +57 50 05.483985972   18.43 17.15   15.66 C,1e 58 0
11 3XMM J172005.6+575759 X 17 20 05.62 +57 57 59.2           ~ 1 0
12 XMMU J172010.2+574823 X 17 20 09.99192 +57 48 22.2300           M4 1 0
13 [BS61] 522 RG* 17 20 13.3866478248 +57 50 51.678992976   19.13 18.182   16.939 ~ 9 0
14 NAME Dra dSph G 17 20 14.335 +57 55 16.39   12.40 10.6     ~ 1246 1
15 [BS61] 526 * 17 20 18.0233579664 +57 51 05.289183936     18.672   16.219 ~ 6 0
16 3XMM J172054.1+580038 X 17 20 54.20 +58 00 38.8           ~ 1 0
17 3XMM J172104.8+575333 X 17 21 04.83 +57 53 33.3           ~ 2 0
18 [BFO2002] Dra 30394 * 17 21 13.5113985216 +58 06 09.701936892     19.358   16.607 M: 3 0
19 [BFO2002] Dra 30692 * 17 21 31.2129998328 +58 04 48.940227984     20.599   18.136 ~ 2 0
20 XMMU J172139.6+575506 X 17 21 39.6364042080 +57 55 09.306360912           ~ 1 0
21 XMMU J172151.4+575700 X 17 21 51.4582185744 +57 57 01.667698164           ~ 1 0

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2022.05.28-22:49:59

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