2011A&A...533A..25I


C.D.S. - SIMBAD4 rel 1.7 - 2019.12.11CET17:55:51

2011A&A...533A..25I - Astronomy and Astrophysics, volume 533A, 25-25 (2011/9-1)

VLT/X-shooter observations of the low-metallicity blue compact dwarf galaxy PHL 293B including a luminous blue variable star.

IZOTOV Y.I., GUSEVA N.G., FRICKE K.J. and HENKEL C.

Abstract (from CDS):

We present VLT/X-shooter spectroscopic observations in the wavelength range λλ3000-23000Å of the extremely metal-deficient blue compact dwarf (BCD) galaxy PHL 293B containing a luminous blue variable (LBV) star and compare them with previous data. This BCD is one of the two lowest-metallicity galaxies where LBV stars were detected, allowing us to study the LBV phenomenon in the extremely low metallicity regime. We determine abundances of nitrogen, oxygen, neon, sulfur, argon, and iron by analyzing the fluxes of narrow components of the emission lines using empirical methods and study the properties of the LBV from the fluxes and widths of broad emission lines. We derive an interstellar oxygen abundance of 12+logO/H=7.71±0.02, which is in agreement with previous determinations. The observed fluxes of narrow Balmer, Paschen and Brackett hydrogen lines correspond to the theoretical recombination values after correction for extinction with a single value C(Hβ)=0.225. This implies that the star-forming region observed in the optical range is the only source of ionisation and there is no additional source of ionisation that is seen in the NIR range but is hidden in the optical range. We detect three v=1-0 vibrational lines of molecular hydrogen. Their flux ratios and non-detection of v=2-1 and 3-1 emission lines suggest that collisional excitation is the main source producing H2 lines. For the LBV star in PHL 293B we find broad emission with P Cygni profiles in several Balmer hydrogen emission lines and for the first time in several Paschen hydrogen lines and in several He i emission lines, implying temporal evolution of the LBV on a time scale of 8 years. The Hα luminosity of the LBV star is by one order of magnitude higher than the one obtained for the LBV star in NGC 2363=Mrk 71 which has a slightly higher metallicity 12+logO/H=7.87. The terminal velocity of the stellar wind in the low-metallicity LBV of PHL293B is high, ∼800km/s, and is comparable to that seen in spectra of some extragalactic LBVs during outbursts. We find that the averaged terminal velocities derived from the Paschen and HeI emission lines are by some ∼40-60km/s lower than those derived from the Balmer emission lines. This probably indicates the presence of the wind accelerating outward.

Abstract Copyright:

Journal keyword(s): galaxies: starburst - galaxies: ISM - galaxies: abundances - stars: activity

VizieR on-line data: <Available at CDS (J/A+A/533/A25): fig1.dat fig2.dat>

Simbad objects: 16

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Number of rows : 16

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 NAME SMC G 00 52 38.0 -72 48 01   2.79 2.2     ~ 9137 1
2 QSO B0125-0635 QSO 01 27 35.5241670251 -06 19 35.428005150 14.75 15.05 14.48 14.06 13.70 ~ 86 0
3 HD 20572 * 03 18 19.7830064697 -09 43 53.624020618   7.87 7.87     A0V 12 0
4 SBSG 0335-052B G 03 37 44.04 -05 02 40.2   16.77 16.65   16.79 ~ 140 1
5 UGCA 116 H2G 05 55 42.645 +03 23 32.23 10.74 11.68 11.46   11.82 ~ 492 0
6 NGC 2363 G 07 28 29.83 +69 11 32.8   15.5       ~ 245 1
7 NGC 2363A HII 07 28 42.8 +69 11 21           ~ 536 3
8 NGC 2366 H2G 07 28 51.85 +69 12 31.1 12.25 11.86 11.39 11.33   ~ 687 0
9 Mrk 116 PaG 09 34 02.1 +55 14 25           ~ 978 1
10 UGC 5340 G 09 56 46.047 +28 49 43.77 14.82 14.74 14.59 14.55   ~ 170 1
11 * eta Car Em* 10 45 03.5455050 -59 41 03.951060 6.37 7.034 6.21 4.90 4.41 OBepec 2157 0
12 Mrk 59 AGN 12 59 00.288 +34 50 42.45           ~ 309 2
13 * alf Lyr dS* 18 36 56.33635 +38 47 01.2802 0.03 0.03 0.03 0.07 0.10 A0Va 2475 0
14 NAME Kinman Dwarf bCG 22 30 36.7959900449 -00 06 36.893332535 16.85 17.35 16.87   16.65 ~ 45 1
15 Feige 110 HS* 23 19 58.3995050606 -05 09 56.170282845 10.360 11.45 11.50 11.970 12.145 sdO8VIIIHe5 539 1
16 Mrk 930 AGN 23 31 58.630 +28 56 50.51 14.27 15.04 14.63 14.56 14.46 ~ 120 0

    Equat.    Gal    SGal    Ecl

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2019.12.11-17:55:51

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