17 research outputs found
Photometric calibration of the Stellar Abundance and Galactic Evolution Survey (SAGES): Nanshan One-meter Wide-field Telescope g, r, and i band imaging data
In this paper, a total of approximately 2.6 million dwarfs were constructed
as standard stars, with an accuracy of about 0.01-0.02 mag for each band, by
combining spectroscopic data from the Large Sky Area Multi-Object Fiber
Spectroscopic Telescope Data Release 7, photometric data from the corrected
Gaia Early Data Release 3, and photometric metallicities. Using the
spectroscopy based stellar color regression method (SCR method) and the
photometric-based SCR method (SCR' method), we performed the relative
calibration of the Nanshan One-meter Wide-field Telescope imaging data. Based
on the corrected Pan-STARRS DR1 photometry, the absolute calibration was also
performed. In the photometric calibration process, we analyzed the dependence
of the calibration zero points on different images (observation time),
different gates of the CCD detector, and different CCD positions. We found that
the stellar flat and the relative gain between different gates depend on time.
The amplitude of gain variation in three channels is approximately 0.5%-0.7%
relative to the other channel, with a maximum value of 4%. In addition,
significant spatial variations of the stellar flat fitting residual are found
and corrected. Using repeated sources in the adjacent images, we checked and
discovered internal consistency of about 1-2 mmag in all the filters. Using the
PS1 magnitudes synthesized by Gaia DR3 BP/RP spectra by the synthetic
photometry method, we found that the photometric calibration uniformity is
about 1-2 mmag for all the bands, at a spatial resolution of 1.3 degree. A
detailed comparison between the spectroscopy-based SCR and photometric-based
SCR method magnitude offsets was performed, and we achieved an internal
consistency precision of about 2 mmag or better with resolutions of 1.3 degree
for all the filters. Which is mainly from the position-dependent errors of the
E(B-V) used in SCR' method.Comment: 15 pages in Chinese language, 8 figures, Chinese Science Bulletin
accepted and published online
(https://www.sciengine.com/CSB/doi/10.1360/TB-2023-0052), see main results in
Figures 6, 7 and
Phase II of the LAMOST-Kepler/K2 survey. I. Time series of medium-resolution spectroscopic observations
Phase \RNum{2} of the LAMOST-{\sl Kepler/K}2 survey (LK-MRS), initiated in
2018, aims at collecting medium-resolution spectra (; hereafter
MRS) for more than stars with multiple visits ( epochs) over a
period of 5 years (2018 September to 2023 June). We selected 20 footprints
distributed across the {\sl Kepler} field and six {\sl K}2 campaigns, with each
plate containing a number of stars ranging from to .
During the first year of observations, the LK-MRS has already collected
and high-quality spectra in the blue and red
wavelength range, respectively. The atmospheric parameters and radial
velocities for spectra of targets were successfully
calculated by the LASP pipeline. The internal uncertainties for the effective
temperature, surface gravity, metallicity, and radial velocity are found to be
\,K, \,dex, \,dex, and \,km\,s, respectively. We
found , , and stars in common with the targets from the
LAMOST low-resolution survey (LRS), GAIA and APOGEE, respectively,
corresponding to a fraction of , and . In
general, the parameters derived from LK-MRS spectra are consistent with those
obtained from the LRS and APOGEE spectra, but the scatter increases as the
surface gravity decreases when comparing with the measurements from APOGEE. A
large discrepancy is found with the GAIA values of the effective temperature.
The comparisons of radial velocities of LK-MRS to GAIA and LK-MRS to APOGEE
nearly follow an Gaussian distribution with a mean and
\,km\,s, respectively.Comment: 24 pages, 15 figures, 4 tables, ApJS, accepte
KIC 3440495: A Rapidly Rotating δ Scuti-γ Doradus Hybrid Pulsator in a Binary System
International audienceIn this paper, we study the pulsation properties of KIC 3440495 using Kepler and TESS data. A Fourier analysis of the light curve reveals 24 pulsation modes as well as 29 frequencies associated with rotation. The rotation frequency is derived to be f rot = 2.322909(2) day-1, and the rotational modulation is determined to be caused by starspots. A large frequency separation of Δν = 54.5 μHz is found by using a Fourier transform, the autocorrelation function, a histogram of frequency differences, and an échelle diagram. We use the large separation to estimate the refined stellar parameters of the star to be v = [239, 279] km s-1, M = [1.5, 1.65] M ⊙, R equator = [2.03, 2.30] R ⊙, R polar = [1.72, 1.78] R ⊙, and ω = [0.61, 0.77]. The phase modulations of the pulsating frequencies show a long-term trend which may be attributed to an orbital effect of a binary system; hence, the star may be a fast rotating pulsator in a binary system. KIC 3440495 has an amplitude spectrum similar to Altair, and is identified as a potential sister of Altair. Based on studies of Altair, KIC 3330495 is presumably a young star at a similar evolutionary stage