J/MNRAS/511/4724 alpha Leo spectro-interferometric observation (Hadjara+, 2022)
Application limit of the photocentre displacement to fundamental stellar
parameters of fast rotators - illustration on the edge-on fast rotator Regulus.
Hadjara M., Petrov R.G., Jankov S., Cruzalebes P., Boskri A., Spang A.,
Lagarde S., He J., Chen X., Nitschelm C., de Almeida E.S.G, Pereira G.,
Michael E.A., Gao Q., Wang W., Reyes I., Arcos C., Araya I., Cure M.
<Mon. Not. R. Astron. Soc. 511, 4724 (2022)>
=2022MNRAS.511.4724H 2022MNRAS.511.4724H (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Interferometry
Keywords: methods: numerical - methods: observational -
techniques: high angular resolution - techniques: interferometric -
stars: rotation
Abstract:
Differential Interferometry allows to obtain the differential
visibility and phase, in addition to the spectrum. The differential
phase contains important information about the structure and motion of
stellar photosphere such as stellar spots and non-radial pulsations,
and particularly the rotation. Thus, this interferometric observable
strongly helps to constrain the stellar fundamental parameters of fast
rotators. The spectroastrometry mainly uses the photocentre
displacements, which is a first approximation of the differential
phase, and is applicable only for unresolved or marginally objects. We
study here the sensitivity of relevant stellar parameters to the
simulated photocentres using the scirocco code: a semi-analytical
algorithm dedicated to fast rotators, applied to two theoretical
modelling stars based on Achernar and Regulus, in order to classify
the importance of these parameters and their impact on the modelling.
We compare our simulations with published VLTI/AMBER data. This work
sets the limits of application of photocentre displacements to fast
rotators, and under which conditions we can use the photocentres
and/or the differential phase, through a pre-established physical
criterion. To validate our theoretical study, we apply our method of
analysis on observed data of the edge-on fast rotator Regulus. For
unresolved targets, with a visibility V∼1, the photocentre can
constrain the main stellar fundamental parameters of fast rotators,
whereas from marginally resolved objects (0.8≤V<1), mainly the
rotation axis position angle (PArot) can be directly deduced
from the vectorial photocentre displacement, which is very important
for young cluster studies.
Description:
VLTI/AMBER data of alf Leo obtained from 2.279 to 2.308 micron,
including the spectrocopically calibrated spectrum, visibilities and
differential phases measured at three baselines, and closure phase.
Objects:
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RA (2000) DE Designation(s)
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10 08 22.31 +11 58 01.95 alf Leo = HD 87901
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
alf_leo.dat 307 1014 Spectrocopically calibrated spectrum, visibilities
and differential phases measured at three
baselines, and closure phase
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Byte-by-byte Description of file: alf_leo.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Index [1/1014]+ Index
6- 13 F8.6 um WL Spectral channel index
19- 30 E12.7 --- Flux Normalized flux
32- 43 E12.7 --- e_Flux Error in Normalized flux
45- 56 E12.7 -- Vis1 Visibility measured at baseline 1
58- 69 E12.7 --- e_Vis1 Error in visibility at baseline 1
71- 83 E13.7 deg DP1 Differential phase measured at baseline 1
85- 96 E12.7 deg e_DP1 Error in differential phase at baseline 1
98-109 E12.7 --- Vis2 Visibility measured at baseline 2
111-122 E12.7 --- e_Vis2 Error in visibility at baseline 2
124-136 E13.7 deg DP2 Differential phase measured at baseline 2
138-149 E12.7 deg e_DP2 Error in differential phase at baseline 2
151-162 E12.7 --- Vis3 Visibility measured at baseline 3
164-175 E12.7 --- e_Vis3 Error in visibility at baseline 3
177-189 E13.7 deg DP3 Differential phase measured at baseline 3
191-202 E12.7 deg e_DP3 Error in differential phase at baseline 3
204-216 E13.7 deg CP Closure phase
218-229 E12.7 deg e_CP Error in closure phase
231-242 E12.7 m BP1 Projected baseline 1
244-255 E12.7 deg PA1 Position angle of baseline 1
257-268 E12.7 m BP2 Projected baseline 2
270-281 E12.7 deg PA2 Position angle of baseline 2
283-294 E12.7 m BP3 Projected baseline 3
296-307 E12.7 deg PA3 Position angle of baseline 3
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Acknowledgements:
Massinissa Hadjara, massinissa.hadjara(at)gmail.com
References:
(End) Massinissa Hadjara [CASSACA/UChile], Patricia Vannier [CDS] 15-Mar-2022