2014A&A...571A..93G


C.D.S. - SIMBAD4 rel 1.7 - 2019.10.16CEST01:07:19

2014A&A...571A..93G - Astronomy and Astrophysics, volume 571A, 93-93 (2014/11-1)

The Cocoon nebula and its ionizing star: do stellar and nebular abundances agree?

GARCIA-ROJAS J., SIMON-DIAZ S. and ESTEBAN C.

Abstract (from CDS):

Main-sequence massive stars embedded in an HII region should have the same chemical abundances as the surrounding nebular gas+dust. The Cocoon nebula (IC 5146), a close-by Galactic HII region ionized by a narrow line B0.5 V single star (BD+46 3474), is an ideal target to compare nebular and stellar abundances in detail in the same Galactic region. We investigate the chemical content of oxygen and other elements in the Cocoon nebula from two different points of view: an empirical analysis of the nebular spectrum, and a detailed spectroscopic analysis of the associated early B-type star using state-of-the-art stellar atmosphere modeling. By comparing the stellar and nebular abundances, we aim to indirectly address the long-standing problem of the discrepancy found between abundances obtained from collisionally excited lines and optical recombination lines in photoionized nebulae. We collected long-slit spatially resolved spectroscopy of the Cocoon nebula and a high-resolution optical spectrum of the ionizing star. Standard nebular techniques along with updated atomic data were used to compute the physical conditions and gaseous abundances of O, N, and S in eight apertures extracted across a semidiameter of the nebula. We performed a self-consistent spectroscopic abundance analysis of BD+46 3474 based on the atmosphere code FASTWIND to determine the stellar parameters and Si, O, and N abundances. The Cocoon nebula and its ionizing star, located at a distance of 800±80pc, have a chemical composition very similar to the Orion nebula and other B-type stars in the solar vicinity. This result agrees with the high degree of homogeneity of the present-day composition of the solar neighborhood (up to 1.5Kpc from the Sun) as derived from the study of the local cold-gas interstellar medium. The comparison of stellar and nebular collisionally excited line abundances in the Cocoon nebula indicates that O and N gas+dust nebular values agree better with stellar values assuming small temperature fluctuations on the order of those found in the Orion nebula (t2=0.022). For S, the behaviour is somewhat puzzling, and different conclusions can be reached depending on the atomic data set used.

Abstract Copyright:

Journal keyword(s): H II regions - ISM: individual objects: IC 5146 - ISM: abundances - stars: abundances - stars: early-type - stars: individual: BD+46 3474

CDS comments: Standard star BD+45 4655 is a probable misprint, not in SIMBAD.

Simbad objects: 13

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Number of rows : 13

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2019
#notes
1 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 10560 1
2 NGC 300 GiG 00 54 53.4460065856 -37 41 03.182962667 8.83 8.69 8.13 7.46   ~ 1263 2
3 M 33 GiG 01 33 50.904 +30 39 35.79 6.17 6.27 5.72     ~ 5019 1
4 NAME Orion Nebula Cluster OpC 05 35.0 -05 29           ~ 1906 1
5 M 42 HII 05 35 17.3 -05 23 28           ~ 3657 0
6 M 43 HII 05 35 31 -05 16.2           ~ 155 0
7 NAME Ori I As* 05 38 -02.8           ~ 543 0
8 NGC 3372 HII 10 44 19.0 -59 53 21           ~ 865 2
9 M 16 OpC 18 18 48 -13 48.4   6.58 6.0     ~ 920 2
10 NGC 7009 PN 21 04 10.8153350719 -11 21 48.581808296   12.48 12.07     ~ 951 1
11 IC 5146 SFR 21 53 24 +47 16.0   7.82 7.2     ~ 374 2
12 BD+46 3474 * 21 53 28.8503 +47 15 59.846 10.27 10.43 9.74     B1V 47 0
13 SH 2-125 HII 21 53 30 +47 21.2           ~ 38 1

    Equat.    Gal    SGal    Ecl

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2019.10.16-01:07:19

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