J/A+A/694/A152 Late-type RSG candidates from Gaia RVS spectra (Zhang+, 2025)
Searching for Galactic red supergiants with Gaia RVS spectra.
Zhang Z., Jiang B., Ren Y., Zhao H., Yang M.
<Astron. Astrophys. 694, A152 (2025)>
=2025A&A...694A.152Z 2025A&A...694A.152Z (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, supergiant ; Spectra, infrared
Keywords: stars: late-type - stars: massive - supergiants
Abstract:
Red supergiants (RSGs) are essential to understanding the evolution
and the contribution to the interstellar medium of massive stars.
However, the number of identified RSGs within the Milky Way is still
limited mainly due to the difficulty of measuring stellar extinction
and distance. The release of approximately one million RVS spectra in
Gaia DR3 presents new opportunity for identifying Galactic RSGs,
because the equivalent width of the calcium triplet lines (EW(CaT)) in
the spectra is an excellent indicator of stellar surface gravity. This
work uses the RVS spectra with signal-to-noise ratio (SNR) greater
than 100 to search for the Galactic RSGs. The dwarf stars and red
giants are removed and the RSG candidates are selected by the location
in the EW(CaT) vs. BP-RP diagram. The early-type RSG candidates
(K0-M2) are then identified by BP-RP>1.584 and EW(CaT)>1.1nm. To
identify late-type RSG candidates (after M2), the criteria of the
average equivalent widths of TiO in the XP spectra (EW(TiO)) > 10 nm,
the color index K-W3<0.5 and the period-amplitude sequence from Gaia
DR3 LPV catalog are further applied to reduce the contamination of
late-type red giants and asymptotic giant branch stars. This method
yields 30 early-type (K0-M2) and 6196 late-type (after M2) RSG
candidates, which is a significant increase to the present Galactic
RSG sample. The application of this approach to the spectra with
SNR>50 results in 48 early-type and 11491 late-type RSG candidates.
This preliminary analysis paves the way for more extensive research
with Gaia DR4 when larger spectral datasets are expected to
significantly enhance our understanding of Galactic RSG populations.
Description:
Basic parameters of the 6,196 late-type (later than M2) red supergiant
candidates identified using Gaia RVS spectra. The table includes the
following information: source_id, position, G, BP, and RP magnitudes,
as well as the signal-to-noise ratio (S/N) of the RVS spectra from the
Gaia main catalog; K-band magnitudes from 2MASS; W3-band magnitudes
from ALLWISE; the measured equivalent widths (and uncertainties) of
the Ca triplet lines; and the average equivalent widths of the TiO
bands derived from Gaia XP spectra. For details, please refer to the
main text of the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea2.dat 186 6196 The 6196 late-type RSG candidates from
Gaia RVS spectra
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- --- [Gaia DR3]
10- 28 I19 --- GaiaDR3 Destination in Gaia DR3 main catalog
30- 44 F15.11 deg RAdeg Right ascension (ICRS) at Ep=2016.0
46- 60 F15.11 deg DEdeg Declination (ICRS) at Ep=2016.0
62- 70 F9.6 mag Gmag G-band magnitude in Gaia
72- 80 F9.6 mag BPmag BP-band magnitude in Gaia
82- 90 F9.6 mag RPmag RP-band magnitude in Gaia
92-103 E12.6 --- RVSS/N Signal to noise ratio in RVS spectrum
105-113 F9.6 nm Ca8498 Equivalent width of CaII at 849.8nm
115-123 F9.6 nm Ca8542 Equivalent width of CaII at 854.2nm
125-133 F9.6 nm Ca8662 Equivalent width of CaII at 866.2nm
135-139 F5.3 mag Kmag K-band magnitude in 2MASS
141-146 F6.3 mag W3mag ?=- W3-band magnitude in ALLWISE
148-156 F9.6 nm TiO Equivalent width of TiO in XP spectra
158-166 F9.7 nm e_Ca8498 Error in CaII at 849.8nm measurement
168-176 F9.7 nm e_Ca8542 Error in CaII at 854.2nm measurement
178-186 F9.7 nm e_Ca8662 Error in CaII at 866.2nm measurement
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Acknowledgements:
Zehao Zhang, zhzhang(at)mail.bnu.edu.cn
(End) Zehao Zhang [Beijing Normal Univ.], Patricia Vannier [CDS] 25-Dec-2024