Abstract
We present newly calibrated period–
ϕ
31
–Fe/H relations for fundamental-mode RR Lyrae stars in the optical and, for the first time, mid-infrared. This work’s calibration data set provides ...the largest and most comprehensive span of parameter space to date, with homogeneous metallicities from −3 ≲ Fe/H ≲ 0.4 and accurate Fourier parameters derived from 1980 ASAS-SN (
V
band) and 1083 WISE (NEOWISE extension,
W
1 and
W
2 bands) RR Lyrae stars with well-sampled light curves. We compare our optical period–
ϕ
31
–Fe/H relation with those available in the literature and demonstrate that our relation minimizes systematic trends in the lower and higher metallicity range. Moreover, a direct comparison shows that our optical photometric metallicities are consistent with both those from high-resolution spectroscopy and globular clusters, supporting the good performance of our relation. We found an intrinsic scatter in the photometric metallicities (0.41 dex in the
V
band and 0.50 dex in the infrared) by utilizing large calibration data sets covering a broad metallicity range. This scatter becomes smaller when optical and infrared bands are used together (0.37 dex). Overall, the relations derived in this work have many potential applications, including large-area photometric surveys with James Webb Space Telescope in the infrared and LSST in the optical.
ABSTRACT
RR Lyrae stars have long been popular standard candles, but significant advances in methodology and technology have been made in recent years to increase their precision as distance ...indicators. We present multiwavelength (optical UBVRcIc and Gaia G, BP, RP; near-infrared JHKs; mid-infrared 3.6, 4.5) period–luminosity–metallicity (PLZ), period–Wesenheit–metallicity (PWZ) relations, calibrated using photometry obtained from the Carnegie RR Lyrae Program and parallaxes from the Gaia second data release for 55 Galactic field RR Lyrae stars. The metallicity slope, which has long been predicted by theoretical relations, can now be measured in all passbands. The scatter in the PLZ relations is on the order of 0.2 mag, and is still dominated by uncertainties in the parallaxes. As a consistency check of our PLZ relations, we also measure the distance modulus to the globular cluster M4, the Large Magellanic Cloud and the Small Magellanic Cloud, and our results are in excellent agreement with estimates from previous studies.
We present new theoretical period-luminosity-metallicity (PLZ) relations for RR Lyræ stars (RRLs) at Spitzer and WISE wavelengths. The PLZ relations were derived using nonlinear, time-dependent ...convective hydrodynamical models for a broad range of metal abundances (Z = 0.0001-0.0198). In deriving the light curves, we tested two sets of atmospheric models and found no significant difference between the resulting mean magnitudes. We also compare our theoretical relations to empirical relations derived from RRLs in both the field and in the globular cluster M4. Our theoretical PLZ relations were combined with multi-wavelength observations to simultaneously fit the distance modulus, 0, and extinction, AV, of both the individual Galactic RRL and of the cluster M4. The results for the Galactic RRL are consistent with trigonometric parallax measurements from Gaia's first data release. For M4, we find a distance modulus of 0 = 11.257 0.035 mag with AV = 1.45 0.12 mag, which is consistent with measurements from other distance indicators. This analysis has shown that, when considering a sample covering a range of iron abundances, the metallicity spread introduces a dispersion in the PL relation on the order of 0.13 mag. However, if this metallicity component is accounted for in a PLZ relation, the dispersion is reduced to ∼0.02 mag at mid-infrared wavelengths.
Abstract
We present new empirical infrared period–luminosity–metallicity (PLZ) and period–Wesenheit–metallicity (PWZ) relations for RR Lyae based on the latest Gaia Early Data Release 3 (EDR3) ...parallaxes. The relations are provided in the Wide-field Infrared Survey Explorer (WISE) W1 and W2 bands, as well as in the W(W1,
V
− W1) and W(W2,
V
− W2) Wesenheit magnitudes. The relations are calibrated using a very large sample of Galactic halo field RR Lyrae stars with homogeneous spectroscopic Fe/H abundances (over 1000 stars in the W1 band), covering a broad range of metallicities (−2.5 ≲ Fe/H ≲ 0.0). We test the performance of our PLZ and PWZ relations by determining the distance moduli of both galactic and extragalactic stellar associations: the Sculptor dwarf spheroidal galaxy in the Local Group (finding
μ
¯
0
=
19.47
±
0.06
), the Galactic globular clusters M4 (
μ
¯
0
=
11.16
±
0.05
), and the Reticulum globular cluster in the Large Magellanic Cloud (
μ
¯
0
=
18.23
±
0.06
). The distance moduli determined through all our relations are internally self-consistent (within ≲0.05 mag) but are systematically smaller (by ∼2–3
σ
) than previous literature measurements taken from a variety of methods/anchors. However, a comparison with similar recent RR Lyrae empirical relations anchored with EDR3 likewise shows, to varying extents, a systematically smaller distance modulus for PLZ/PWZ RR Lyrae relations.
1I/'Oumuamua is the first confirmed interstellar body in our solar system. Here we report on observations of 'Oumuamua made with the Spitzer Space Telescope on 2017 November 21-22 (UT). We integrated ...for 30.2 hr at 4.5 m (IRAC channel 2). We did not detect the object and place an upper limit on the flux of 0.3 Jy (3 ). This implies an effective spherical diameter less than 98, 140, 440 m and albedo greater than 0.2, 0.1, 0.01 under the assumption of low, middle, or high thermal beaming parameter , respectively. With an aspect ratio for 'Oumuamua of 6:1, these results correspond to dimensions of 240:40, 341:57, 1080:180 m, respectively. We place upper limits on the amount of dust, CO, and CO2 coming from this object that are lower than previous results; we are unable to constrain the production of other gas species. Both our size and outgassing limits are important because 'Oumuamua's trajectory shows non-gravitational accelerations that are sensitive to size and mass and presumably caused by gas emission. We suggest that 'Oumuamua may have experienced low-level post-perihelion volatile emission that produced a fresh, bright, icy mantle. This model is consistent with the expected value and implied high-albedo value for this solution, but, given our strict limits on CO and CO2, requires another gas species-probably H2O-to explain the observed non-gravitational acceleration. Our results extend the mystery of 'Oumuamua's origin and evolution.
Abstract The giant spiral galaxy M101 is host to the nearest recent Type Ia supernova (SN 2011fe) and thus has been extensively monitored in the near-infrared to study the late-time light curve of ...the SN. Leveraging this existing baseline of observations, we derive the first Mira-based distance to M101 by discovering and classifying a sample of 211 Miras with periods ranging from 240–400 days in the SN field. Combined with new Hubble Space Telescope (HST) WFC3/IR channel observations, our data set totals 11 epochs of F110W (HST YJ ) and 13 epochs of F160W (HST H ) data spanning ∼2900 days. We adopt absolute calibrations of the Mira period–luminosity relation based on geometric distances to the Large Magellanic Cloud and the water megamaser host galaxy NGC 4258, and find μ M101 = 29.10 ± 0.06 mag. This distance is in 1 σ agreement with most other recent Cepheid and tip of the red giant branch distance measurements to M101. Including the previous Mira SN Ia host, NGC 1559, and SN 2005df, we determine the fiducial SN Ia peak luminosity, M B 0 = − 19.27 ± 0.09 mag. With the Hubble diagram of supernovae Ia, we derive H 0 = 72.37 ± 2.97 km s −1 Mpc −1 , a 4.1% measurement of H 0 using Miras. We find excellent agreement with recent Cepheid distance ladder measurements of H 0 and confirm previous indications that the local universe value of H 0 is higher than the early universe value at ∼95% confidence. Currently, the Mira-based H 0 measurement is still dominated by the statistical uncertainty in the SN Ia peak magnitude.
Abstract
We have examined internight variability of K2-discovered “dippers” that are not close to being viewed edge-on, as determined from previously reported ALMA images, using the SpeX spectrograph ...on NASA’s Infrared Telescope Facility. The three objects observed were EPIC 203850058, EPIC 205151387, and EPIC 204638512 (=2MASS J16042165-2130284). Using the ratio of the fluxes between two successive nights, we find that for EPIC 204638512 and EPIC 205151387, we find that the properties of the dust differ from that seen in the diffuse interstellar medium and denser molecular clouds. However, the grain properties needed to explain the extinction does resemble those used to model the disks of many young stellar objects. The wavelength-dependent extinction models of both EPIC 204638512 and EPIC 205151387 includes grains at least 500
μ
m in size, but lacks grains smaller than 0.25
μ
m. The change in extinction during the dips, and the timescale for these variations to occur, imply obscuration by the surface layers of the inner disks. The recent discovery of a highly misinclined inner disk in EPIC 204638512 is suggests that the variations in this disk system may point to due to rapid changes in obscuration by the surface layers of its inner disk, and that other “face-on” dippers might have similar geometries. The He
i
line at 1.083
μ
m in EPIC 205151387 and EPIC 20463851 were seen to change from night to night, suggesting that we are seeing He
i
gas mixed in with the surface dust.
We present our project to calibrate the RR Lyræ period-luminosity-metallicity relation using a sample of Galactic calibrators in the halo and globular clusters.
ABSTRACT We analyzed the warm Spitzer/IRAC data of KIC 8462852. We found no evidence of infrared excess at 3.6 m and a small excess of 0.43 0.18 mJy at 4.5 m below the 3 threshold necessary to claim ...a detection. The lack of strong infrared excess 2 years after the events responsible for the unusual light curve observed by Kepler further disfavors the scenarios involving a catastrophic collision in a KIC 8462852 asteroid belt, a giant impact disrupting a planet in the system or a population of dust-enshrouded planetesimals. The scenario invoking the fragmentation of a family of comets on a highly elliptical orbit is instead consistent with the lack of strong infrared excess found by our analysis.
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