2016AJ....151..149P


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.05CET18:27:45

2016AJ....151..149P - Astron. J., 151, 149-149 (2016/June-0)

GR 290 (Romano's Star). II. Light history and evolutionary state.

POLCARO V.F., MARYEVA O., NESCI R., CALABRESI M., CHIEFFI A., GALLETI S., GUALANDI R., HAVER R., MILLS O.F., OSBORN W.H., PASQUALI A., ROSSI C., VASILYEVA T. and VIOTTI R.F.

Abstract (from CDS):

We have investigated the past light history of the luminous variable star GR 290 (M33/V532, Romano's Star) in the M33 galaxy, and collected new spectrophotometric observations in order to analyze links between this object, the LBV category, and the Wolf-Rayet stars of the nitrogen sequence. We have built the historical light curve of GR 290 back to 1901, from old observations of the star found in several archival plates of M33. These old recordings together with published and new data on the star allowed us to infer that for at least half a century the star was in a low luminosity state, with B ≃ 18-19, most likely without brighter luminosity phases. After 1960, five large variability cycles of visual luminosity were recorded. The amplitude of the oscillations was seen increasing toward the 1992-1994 maximum, then decreasing during the last maxima. The recent light curve indicates that the photometric variations have been quite similar in all the bands and that the B - V color index has been constant within ±0.1m despite the 1.5m change of the visual luminosity. The spectrum of GR 290 at the large maximum of 1992-94 was equivalent to late-B-type, while, during 2002-2014, it varied between WN10h-11h near the visual maxima to WN8h-9h at the luminosity minima. We have detected, during this same period, a clear anti-correlation between the visual luminosity, the strength of the He ii 4686 Å emission line, the strength of the 4600-4700 Å lines' blend, and the spectral type. From a model analysis of the spectra collected during the whole 2002-2014 period, we find that the Rosseland radius R2/3, changed between the minimum and maximum luminosity phases by a factor of three while Teff varied between about 33,000 and 23,000 K. We confirm that the bolometric luminosity of the star has not been constant, but has increased by a factor of ∼1.5 between minimum and maximum luminosity, in phase with the apparent luminosity variations. Presently, GR 290 falls in the H-R diagram close to WN8h stars and is probably younger than them. In the light of current evolutionary models of very massive stars, we find that GR 290 has evolved from an ∼60 M progenitor star and should have an age of about four million years. From its physical charcteristics, we argue that GR 290 has left the LBV stage and is presently moving from the LBV stage to a Wolf-Rayet stage of a late nitrogen spectral type.

Abstract Copyright: © 2016. The American Astronomical Society. All rights reserved.

Journal keyword(s): galaxies: individual: M33 - stars: evolution - stars: individual: (GR 290, M33 V0532) - stars: variables: general - stars: Wolf-Rayet

Simbad objects: 15

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Number of rows : 15

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 M 31 G 00 42 44.330 +41 16 07.50 4.86 4.36 3.44     ~ 11217 1
2 [HS80] B5 WR* 01 32 37.72 +30 40 05.6 16.445 17.498 17.627 17.447 17.473 Ofpe/WN9 26 0
3 FSZ 35 WR* 01 33 00.1615240595 +30 30 15.042971536 17.660 18.696 18.785 18.706 18.674 WN8 11 0
4 M 33 GiG 01 33 50.904 +30 39 35.79 6.17 6.27 5.72     ~ 5253 1
5 NAME Romano Star WR* 01 35 09.7011265200 +30 41 57.173367187   16.5 18.04     Ofpe/WN9 47 1
6 V* S Dor sg* 05 18 14.3572490675 -69 15 01.148131817 9.08 10.39 10.25 9.74 9.14 A5Iaeq 352 0
7 HD 86161 WR* 09 54 52.9034376427 -57 43 38.273623332 7.94 8.65 8.36 8.93   WN8h 206 0
8 HD 90177 s*b 10 22 53.8426931454 -59 37 28.361118869 9.16 9.66 8 8.15   LBV 308 0
9 * eta Car Em* 10 45 03.5455050 -59 41 03.951060 6.37 7.034 6.21 4.90 4.41 OBepec 2255 0
10 V* AG Car WR* 10 56 11.5779283438 -60 27 12.809532379 7.00 7.57 6.96 7.73   WN11h 598 0
11 HD 96548 WR* 11 06 17.2033098417 -65 30 35.237611013 7.10 7.80 7.70 8.49   WN8h 395 0
12 HD 326823 WR* 17 06 53.9048235954 -42 36 39.705015741 9.68 9.87 9.03 9.51   WNpec 73 1
13 Hen 2-427 WR* 19 11 30.8750511254 +16 51 38.199008052   12.19 11.50     WN8h 322 0
14 * P Cyg s*b 20 17 47.2020844 +38 01 58.552724 4.66 5.24 4.82 4.28 4.02 B1-2Ia-0ep 1140 1
15 MR 119 WR* 23 00 10.1254033879 +60 55 38.409749646 11.85 12.18 11.01     WN8h 92 0

    Equat.    Gal    SGal    Ecl

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