Abstract
The aim of this work is to evaluate the performance of photometric metallicity Fe/H, determined based on
V
-band light curves photometrically transformed from the
gr
-band light curves. We ...tested this by using a set of homogeneous samples of fundamental mode RR Lyrae located in the Kepler field. It was found that the color term is necessary in such photometric transformation. We demonstrated that when including the color term the determined photometric Fe/H are in good agreement with the spectroscopic Fe/H, either based on the calibrated or the transformed
V
-band light curves. We also tested the impact of Blazhko RR Lyrae in determining the photometric Fe/H, and found that Blazhko RR Lyrae can give consistent photometric Fe/H. Finally, we derived independent
gVr
-band Fe/H–
ϕ
31
–
P
relations (where
ϕ
31
and
P
are the Fourier parameter and pulsation period, respectively) using our light curves. The
V
-band relation is in good agreement with the most recent determination given in the literature.
Abstract
Multiband light curves of two RR Lyrae variables in Segue II and Ursa Major II ultrafaint dwarf galaxies were collected from near simultaneous observations using the Lulin One-meter ...Telescope in
Vgri
bands. Together with Gaia
G
-band light curves, we determined photometric metallicities using empirical relations involving pulsation period and Fourier parameter as dependent parameters. We demonstrated that the RR Lyrae photometric metallicity can be determined accurately when these empirical relations were employed at multiple wavelengths, which can potentially improve the distance determination based on RR Lyrae stars. The photometric metallicities based on our approach were found to be −2.27 ± 0.13 dex and −1.87 ± 0.16 dex for the RR Lyrae in Segue II and Ursa Major II UFD, respectively, with corresponding distance moduli of 17.69 ± 0.15 mag and 17.58 ± 0.15 mag, in agreement with previous literature determinations. This approach of photometric metallicity of RR Lyrae based on multiband optical light curves will be particularly relevant for distance measurements in the era of the Vera C Rubin’s Legacy Survey of Space and Time.
The Zwicky Transient Facility: Surveys and Scheduler Bellm, Eric C.; Kulkarni, Shrinivas R.; Barlow, Tom ...
Publications of the Astronomical Society of the Pacific,
06/2019, Letnik:
131, Številka:
1000
Journal Article
Recenzirano
Odprti dostop
We present a novel algorithm for scheduling the observations of time-domain imaging surveys. Our integer linear programming approach optimizes an observing plan for an entire night by assigning ...targets to temporal blocks, enabling strict control of the number of exposures obtained per field and minimizing filter changes. A subsequent optimization step minimizes slew times between each observation. Our optimization metric self-consistently weights contributions from time-varying airmass, seeing, and sky brightness to maximize the transient discovery rate. We describe the implementation of this algorithm on the surveys of the Zwicky Transient Facility and present its on-sky performance.
Abstract Virgo III is a newly discovered ultra-faint-dwarf (UFD) candidate, and finding RR Lyrae associated with this galaxy is important to constrain its distance. In this work, we present a search ...of RR Lyrae in the vicinity of Virgo III based on the time-series r -band images taken from the Lulin One-meter Telescope (LOT). We have identified three RR Lyrae from our LOT data, including two fundamental mode (ab-type) and a first-overtone (c-type) RR Lyrae. Assuming these three RR Lyrae are members of Virgo III, we derived the distance to this UFD as 154 ± 25 kpc, fully consistent with the independent measurements given in the literature. We have also revisited the relation between absolute V -band magnitude ( M V ) and the number of RR Lyrae (of all types, N RRL ) found in local galaxies, demonstrating that the M V - N RRL relation is better described with the specific RR Lyrae frequency.
Abstract RRd stars are a subclass of RR Lyrae stars that pulsate simultaneously in the fundamental and the first-overtone radial modes. We report the analysis of 10 RRd stars discovered in the Sloan ...Digital Sky Survey (SDSS) Stripe 82 region of the Galactic halo using SDSS and Zwicky Transient Facility data. By combining the two data sets, we constructed ∼23 yr long lightcurves in gri bands, and conclude that out of 10, 9 were the classical RRd stars and 1 was the anomalous RRd star. We also observed the long-term variation, the Blazhko effect, in 3 classical RRd stars out of 10 stars, giving an incidence rate of 30%. The shortest Blazhko period observed was 226.4 ± 0.8 days and the longest was 2799 ± 75 days.
Current time domain facilities are finding several hundreds of transient astronomical events a year. The discovery rate is expected to increase in the future as soon as new surveys such as the Zwicky ...Transient Facility (ZTF) and the Large Synoptic Sky Survey (LSST) come online. Presently, the rate at which transients are classified is approximately one order or magnitude lower than the discovery rate, leading to an increasing "follow-up drought". Existing telescopes with moderate aperture can help address this deficit when equipped with spectrographs optimized for spectral classification. Here, we provide an overview of the design, operations and first results of the Spectral Energy Distribution Machine (SEDM), operating on the Palomar 60-inch telescope (P60). The instrument is optimized for classification and high observing efficiency. It combines a low-resolution (R ∼ 100) integral field unit (IFU) spectrograph with "Rainbow Camera" (RC), a multi-band field acquisition camera which also serves as multi-band (ugri) photometer. The SEDM was commissioned during the operation of the intermediate Palomar Transient Factory (iPTF) and has already lived up to its promise. The success of the SEDM demonstrates the value of spectrographs optimized for spectral classification.
Abstract
Mira variables are asymptotic giant-branch pulsating stars with long pulsation periods and large amplitudes in optical bands. By applying the random forest algorithm to the
I
-band light ...curves for the Miras in the Magellanic Clouds, we have classified these Miras into regular Miras and nonregular Miras. Nonregular Miras exhibit a long-term variation in addition to their primary pulsation periods. Our results confirm that the period–luminosity relation for maximum light has a small dispersion, but only occurs on the regular oxygen-rich Miras, which we recommend to be applied in future distance-scale work. We have also collected multiband photometry for these Miras to perform a spectral energy distribution fitting with stellar and dust components, showing that a significant fraction of dust is present around the nonregular Miras. According to our results, we believe that the periodic long-term variations seen in the nonregular Miras might be due to the presence of dust.
We present observational details and first results of a near-infrared (JHKs) synoptic survey of the central region of the Large Magellanic Cloud (LMC) using the CPAPIR camera at the CTIO 1.5 m ...telescope. We covered 18 square degrees to a depth of K sub(s)~16.5 mag and obtained an average of 16 epochs in each band at any given location. Our catalog contains more than 3.5 x 10 super(6) sources, including 1417 Cepheid variables previously studied at optical wavelengths by the OGLE survey. Our sample of fundamental-mode pulsators represents a nine-fold increase in the number of these variables with time-resolved, multi-band near-infrared photometry. We combine our large Cepheid sample and a recent precise determination of the distance to the LMC to derive a robust absolute calibration of the near-infrared Leavitt Law for fundamental-mode and first-overtone Cepheids with 10x better constraints on the slopes relative to previous work. We also obtain calibrations for the tip of the red giant branch and the red clump based on our ensemble photometry which are in good agreement with previous determinations.
Abstract
We present new near-infrared,
JHK
s
, period–luminosity relations (PLRs) for RR Lyrae variables in the Messier 53 (M53 or NGC 5024) globular cluster. Multi-epoch
JHK
s
observations, obtained ...with the WIRCam instrument on the 3.6 m Canada–France–Hawaii Telescope, are used for the first time to estimate precise mean magnitudes for 63 RR Lyrae stars in M53 including 29 fundamental-mode (RRab) and 34 first-overtone mode (RRc) variables. The
JHK
s
-band PLRs for RR Lyrae stars are best constrained for RRab types with a minimal scatter of 22, 23, and 19 mmag, respectively. The combined sample of RR Lyrae is used to derive the
K
s
-band PLR,
K
s
=
−
2.303
(
0.063
)
log
P
+
15.212
(
0.016
)
, exhibiting a 1
σ
dispersion of only 0.027 mag. Theoretical period–luminosity–metallicity (PLZ) relations are used to predict parallaxes for 400 Galactic RR Lyrae, resulting in a median parallax zero-point offset of −7 ± 3
μ
as in Gaia Early Data Release 3 (EDR3), which increases to 22 ± 2
μ
as if the parallax corrections are applied. We also estimate a robust distance modulus,
μ
M53
= 16.403 ± 0.024 (statistical) ± 0.033 (systematic) mag, to M53 based on theoretical calibrations. Homogeneous and precise mean magnitudes for RR Lyrae in M53 together with similar literature data for M3, M4, M5, and
ω
Cen are used to empirically calibrate a new RR Lyrae
PLZ
K
s
relation,
K
s
=
−
0.848
(
0.007
)
−
2.320
(
0.006
)
log
P
+
0.166
(
0.011
)
Fe
/
H
, anchored with Gaia EDR3 distances and theoretically predicted relations, and to simultaneously estimate precise RR Lyrae-based distances to these globular clusters.
In this paper, we explore the possibility of using the Wesenheit function to derive individual distances to Galactic Cepheids, as the dispersion of the reddening-free Wesenheit function is smaller ...than the optical period -luminosity (P-L) relation. When compared to the distances from various methods, the averaged differences between our results and published distances range from -0.061 to 0.009, suggesting that the Wesenheit function can be used to derive individual Cepheid distances. We have also constructed Galactic P-L relations and selected Wesenheit functions based on the derived distances. A by-product from this work is the derivation of Large Magellanic Cloud distance modulus when calibrating the Wesenheit function. It is found to be 18.531 + or - 0.043 mag.
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