J/A+A/694/A273 VELOCE modulation zoo. II. (Netzel+, 2025)
The VELOCE modulation zoo. II.
Humps and splitting patterns in spectral lines of classical Cepheids.
Netzel H., Anderson R. I., Viviani G
<Astron. Astrophys. 694, A273 (2025)>
=2025A&A...694A.273N 2025A&A...694A.273N (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Radial velocities ; Optical
Keywords: techniques: radial velocities - stars: oscillations -
stars: variables: Cepheids
Abstract:
Line splitting in spectral lines is observed in various types of stars
due to phenomena such as shocks, spectroscopic binaries, magnetic
fields, spots, and non-radial modes. In pulsating stars, line
splitting is often attributed to pulsation-induced shocks. However,
this is rarely observed in classical Cepheids, with only a few
reports, including X Sagittarii and BG Crucis, where it has been
linked to atmospheric shocks.
We investigate line splitting in X Sgr and BG Cru using spectroscopic
time series, and search for similar phenomena in other classical
Cepheids.
High signal-to-noise cross-correlation function (CCF) time series from
the VELOcities of CEpheids (VELOCE) project are analyzed. This dataset
spans several years, allowing us to study the periodicities and
evolution of CCF features. For X Sgr and BG Cru, we perform a detailed
analysis of the individual components of the split CCFs. Additionally,
we search for periodicities in CCF variations and examine other
classical Cepheids for distortions resembling unresolved line
splitting.
We confirm line splitting in X Sgr and BG Cru, trace the features over
time, and uncover the periodicity behind them. Several other Cepheids
also exhibit CCF humps, suggesting unresolved or marginally resolved
line splitting. We discuss the incidence and characteristics of these
stars.
The periodicity of line splitting in X Sgr and BG Cru differs
significantly from the dominant pulsation period, ruling out
pulsation-induced shocks. The periodicities are too short for
rotation-related phenomena, suggesting non-radial modes as the most
likely explanation, though their exact nature remains unknown. We also
identify humps in six additional stars, indicating an incidence rate
of 3% in the VELOCE sample.
Description:
Analyzed RV, FWHM, BIS, contrast, and EW data for X Sgr, BG Cru, and
SZ Car, are collected in table 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 30 3 Studied stars
table2.dat 74 508 Analyzed data
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See also:
J/A+A/687/A118 : VELOCE modulation zoo. I. (Netzel+, 2024)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Name Star name
8- 9 I2 h RAh Simbad right ascension (J2000)
11- 12 I2 min RAm Simbad right ascension (J2000)
14- 18 F5.2 s RAs Simbad right ascension (J2000)
20 A1 --- DE- Simbad declination sign (J2000)
21- 22 I2 deg DEd Simbad declination (J2000)
24- 25 I2 arcmin DEm Simbad declination (J2000)
27- 30 F4.1 arcsec DEs Simbad declination (J2000)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 6 A6 --- Name Star name
12- 22 F11.5 d Date Observation date (BJD-2400000)
24- 32 F9.5 km/s RV Radial velocity
34- 38 F5.3 km/s e_RV Radial velocity error
40- 47 F8.5 km/s FWHM Full width at half maximum
48- 56 F9.5 km/s BIS ? Bisector inverse span
58- 65 F8.5 --- Contrast ? Relative depth
68- 74 F7.5 --- EW Equivalent width
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Acknowledgements:
Henryka Netzel, henia(at)netzel.pl
References:
Netzel et al., Paper I 2024A&A...687A.118N 2024A&A...687A.118N, Cat. J/A+A/687/A118
(End) Patricia Vannier [CDS] 17-Jan-2025