J/A+A/659/A35 Spectra of IRAS 17449+2320 (Korcakova+, 2022)
The first detection of a magnetic field in low luminosity B[e] stars.
New scenarios for the nature and evolutionary stages of FS CMa stars.
Korcakova D., Sestito F., Manset N., Kroupa P., Votruba V., Slechta M.,
Danford S., Dvorakova N., Raj A., Chojnowski S.D., Singh H.P.
<Astron. Astrophys. 659, A35 (2022)>
=2022A&A...659A..35K 2022A&A...659A..35K (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, spectroscopic ; Magnetic fields ; Spectra, ultraviolet ;
Spectra, optical ; Spectra, infrared
Keywords: circumstellar matter - stars: emission line, Be - magnetic field -
stars: evolution - stars: magnetic field - stars: mass-loss
Abstract:
We report the first detection of the magnetic field in a star of FS
CMa type, a subgroup of objects characterized by the B[e] phenomenon.
The split of magnetically sensitive lines in IRAS 17449+2320
determines the magnetic field modulus of 6.2±0.2kG. Spectral lines
and their variability reveal the presence of a B-type spectrum and a
hot continuum source in the visible. The hot source confirms GALEX UV
photometry. Because there is a lack of spectral lines for the hot
source in the visible, the spectral fitting gives only the lower
temperature limit of the hot source, which is 50000K, and the upper
limit for the B-type star of 11100K. The V/R ratio of the Halpha line
shows quasiperiodic behavior on timescale of 800 days. We detected a
strong red-shifted absorption in the wings of Balmer and OI lines in
some of the spectra. The absorption lines of helium and other metals
show no, or very small, variations, indicating unusually stable
photospheric regions for FS CMa stars. We detected two events of
material infall, which were revealed to be discrete absorption
components of resonance lines.
The discovery of the strong magnetic field together with the Gaia
measurements of the proper motion show that the most probable nature
of this star is that of a post-merger object created after the leaving
the binary of the birth cluster. Another possible scenario is a
magnetic Ap star around Terminal-Age Main Sequence (TAMS). On the
other hand, the strong magnetic field defies the hypothesis that
IRAS 17449+2320 is an extreme classical Be star. Thus, IRAS 17449+2320
provides a pretext for exploring a new explanation of the nature of FS
CMa stars or, at least, a group of stars with very similar spectral
properties.
Description:
The catalogue consists of spectra of IRAS 17449+2320 from eight
observatories: Canada France Hawaii Telescope (CFHT), Apache Point
Observatory (APO), Himalayan Chandra Telescope (HCT), Observatorio
Nacional San Pedro Martir (SPM), Tien-Shan Astronomical Observatory
(TSAO), Ondrejov Observatory (OO), Three College Observatory (TCO) and
Bellavista Observatory L (BO). The observed spectra come from a time
period from 2005 to 2019. The Ondrejov spectra were reduced using
standard IRAF procedures and the program dcr (Pych,
2004PASP..116..148P 2004PASP..116..148P) was applied. Spectra from San Pedro Martir lack
flat field correction.
Objects:
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RA (2000) DE Designation(s)
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17 47 03.27 +23 19 45.4 IRAS 17449+2320 = EM* StHA 145
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb2.dat 166 79 List of observations
fits/* . 79 Individual fits spectra
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Byte-by-byte Description of file: tableb2.dat
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Bytes Format Units Label Explanations
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1- 32 A32 --- FileName Name of the spectrum file in subdirectory fits
34- 43 A10 "date" Obs.date Date of observation
45- 54 F10.2 d HJD ?=- Heliocentric Julian Date
56- 59 I4 0.1nm blambda Lower value of wavelength range of the spectrum
60 A1 --- --- [-]
61- 65 I5 0.1nm Blambda Upper value of wavelength range of the spectrum
67- 70 I4 s ExpTime ?=- Exposure time
72- 74 I3 --- S/N Signal to noise ratio
76-109 A34 --- Project Observer or project ID
111-160 A50 --- Obs Observatory
162-166 I5 --- R Resolving power
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History:
Daniela Korcakova, dvorakova.nela(at)seznam.cz
Acknowledgements:
We would like to thank A. Miroshnichenko, S. V. Zharikov, P. Zasche,
M. Wolf, P. Berardi, and P. Skoda for some spectra. The research of DK
is supported by grant GA 17-00871S of the Czech Science Foundation. PK
acknowledges support from the Grant Agency of the Czech Republic under
grant number 20-21855S and the DAAD Bonn-Prague exchange programme. A.
Raj acknowledges the Research Associate Fellowship with order
no.03(1428)/18/EMR-II under Council of Scientific and Industrial
Research (CSIR).
Based on data from Perek 2m telescope, Ondrejov, Czech Republic.
Based on observations obtained at the Canada-France-Hawaii Telescope
(CFHT) which is operated by the National Research Council of Canada,
the Institut National des Sciences de l'Univers of the Centre National
de la Recherche Scientique of France, and the University of Hawaii.
The observations at the Canada-France-Hawaii Telescope were performed
with care and respect from the summit of Maunakea which is a
significant cultural and historic site.
(End) Patricia Vannier [CDS] 22-Feb-2022