A5031231517- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Galaxies: Formation, Evolution, Phenomena
- Astrophysical Phenomena and Observations
- Geophysics and Gravity Measurements
- Solar and Space Plasma Dynamics
- Spacecraft and Cryogenic Technologies
- Astrophysics and Cosmic Phenomena
- Semiconductor Lasers and Optical Devices
- High-pressure geophysics and materials
- History and Developments in Astronomy
- Mitochondrial Function and Pathology
- Planetary Science and Exploration
- Advanced Frequency and Time Standards
- Inertial Sensor and Navigation
- Methane Hydrates and Related Phenomena
- Adaptive optics and wavefront sensing
- Advanced Vision and Imaging
- Isotope Analysis in Ecology
- Communication in Education and Healthcare
- Pulsars and Gravitational Waves Research
Florida Atlantic University
2018-2023
Iowa State University
2014-2018
University of Florida
2018
Ithaca College
2014
We present a new and independent determination of the local value Hubble constant based on calibration Tip Red Giant Branch (TRGB) applied to Type Ia supernovae (SNeIa). find Ho = 69.8 +/- 0.8 (+/-1.1\% stat) 1.7 (+/-2.4\% sys) km/sec/Mpc. The TRGB method is both precise accurate, parallel to, but Cepheid distance scale. Our sits midway in range defined by current tension. It agrees at 1.2-sigma level with that Planck 2018 estimate, 1.7-sigma SHoES measurement distances have been measured...
Abstract The tip of the red giant branch (TRGB) method provides one most accurate and precise means measuring distances to nearby galaxies. Here we present a multi-wavelength, VIJHK absolute calibration TRGB based on observations stars in Large Magellanic Cloud (LMC), grounded geometric distance, determined by detached eclipsing binaries (DEBs). This paper presents more detailed description first presented Freedman et al. for corrections total line-of-sight extinction reddening LMC. In this...
We present optical and near-infrared UBVRIJHK photometry of stars in the Galactic globular cluster M4 (NGC 6121) based upon a large corpus observations obtained mainly from public astronomical archives. concentrate on RR Lyrae variable cluster, make particular effort to accurately reidentify previously discovered variables. have also two new probable variables field: one them by its position sky photometric properties is member second background (bulge?) object. provide accurate equatorial...
Abstract We performed the largest and most homogeneous spectroscopic survey of field RR Lyraes (RRLs). secured ≈6300 high-resolution (HR, R ∼ 35,000) spectra for 143 RRLs (111 fundamental, RRab; 32 first-overtone, RRc). The atmospheric parameters were estimated by using traditional approach iron abundances measured an LTE line analysis. resulting distribution shows a well-defined metal-rich tail approaching solar abundance. This suggests that experienced complex chemical enrichment in early...
We present new distance determinations to the nearby globular M4 (NGC 6121) based on accurate optical and near-infrared (NIR) mean magnitudes for fundamental (FU) first overtone (FO) RR Lyrae variables (RRLs), empirical NIR period–luminosity (PL) period–Wesenheit (PW) relations. have found that optical–NIR PL PW relations are affected by smaller standard deviations than The difference is consequence of a steady decrease in intrinsic spread cluster RRL apparent at fixed period as longer...
ABSTRACT RR Lyrae stars have long been popular standard candles, but significant advances in methodology and technology made recent years to increase their precision as distance indicators. We present multiwavelength (optical UBVRcIc 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 Program parallaxes second data release for 55 Galactic field...
We present newly-calibrated period-$\phi_{31}$-[Fe/H] relations for fundamental mode RR Lyrae stars in the optical and, first time, mid-infrared. This work's calibration dataset provides largest and most comprehensive span of parameter space to date with homogeneous metallicities from $-3<\textrm{[Fe/H]}<0.4$ accurate Fourier parameters derived 1980 ASAS-SN ($V$-band) 1083 WISE (NEOWISE extension, $W1$ $W2$ bands) well-sampled light curves. compare our those available literature demonstrate...
We present a new complete Near-Infrared (NIR, $JHK_s$) census of RR Lyrae stars (RRLs) in the globular $\omega$ Cen (NGC 5139). collected 15,472 $JHK_s$ images with 4-8m class telescopes over 15 years (2000-2015) covering sky area around cluster center 60x34 arcmin$^2$. These provided calibrated photometry for 182 out 198 RRL candidates ten to sixty measurements per band. also provide homogeneous estimates photometric amplitude 180 ($J$), 176 ($H$) and 174 ($K_s$) RRLs. data were...
New mid-infrared period-luminosity (PL) relations are presented for \rrl{} variables in the globular cluster M4 (NGC 6121). Accurate photometry was obtained 37 using observations from Infrared Array Camera onboard Spitzer Space Telescope. The dispersion of M4's PL is 0.056, and uncertainty slope 0.11 mag. Additionally, weestablished calibrated at 3.6 4.5~\micron{} published Hubble Telescopegeometric parallaxes five Galactic stars. resulting band-averaged distance modulus $ \mu = 11.399 \pm...
Abstract The primary goal of the Carnegie Chicago Hubble Program (CCHP) is to calibrate zero-point Type Ia supernova (SN Ia) Diagram through use Population II standard candles. So far, CCHP has measured direct distances 11 SNe Ia, and here we increase that number 15 with two new Tip Red Giant Branch (TRGB) NGC 5643 1404. We present resolved, point-source photometry from Space Telescope imaging these galaxies in F814W F606W bandpasses. From each galaxy’s stellar halo, construct an F814W-band...
Abstract We provide the largest and most homogeneous sample of α -element (Mg, Ca, Ti) iron abundances for field RR Lyrae (RRLs; 162 variables) by using high-resolution spectra. The current measurements were complemented with similar available in literature 46 RRLs brought to our metallicity scale. ended up a old ( t ≥ 10 Gyr), low-mass stellar tracers (208 RRLs: 169 fundamental, 38 first overtone, 1 mixed mode) covering 3 dex abundance (−3.00 ≤ [Fe/H] 0.24). found that are ∼0.3 more poor...
New accurate and homogeneous optical UBVRI photometry has been obtained for variable stars in the Galactic globular $\omega$ Cen (NGC 5139). We secured 8202 CCD images covering a time interval of 24 years sky area 84x48 arcmin. The current data were complemented with available literature provided new, pulsation parameters (mean magnitudes, luminosity amplitudes,periods) 187 candidate RR Lyrae (RRLs). Among them we have 101 RRc (first overtone), 85 RRab (fundamental) single RRd (double-mode)...
We present new theoretical period-luminosity-metallicity (PLZ) relations for RR Lyrae stars (RRL) at Spitzer and WISE wavelengths. The PLZ were derived using nonlinear, time-dependent convective hydrodynamical models a broad range in metal abundances (Z=0.0001 to 0.0198). In deriving the light curves, we tested two sets of atmospheric (Brott & Hauschildt 2005, Castelli Kurucz 2003) found no significant difference between resulting mean magnitudes. also compare our empirical from RRL both...
We discuss the largest and most homogeneous spectroscopic dataset of field RR Lyrae variables (RRLs) available to date. estimated abundances using both high-resolution low-resolution ({\Delta S} method) spectra for fundamental (RRab) first overtone (RRc) RRLs. The iron 7,941 RRLs were supplemented with similar literature estimates available, ending up 9,015 (6,150 RRab, 2,865 RRc). metallicity distribution shows a mean value <[Fe/H]> = -1.51\pm0.01, {\sigma}(standard deviation)= 0.41 dex...
We developed a new approach to provide accurate estimates of metal content, reddening and true distance modulus RR Lyrae stars (RRLs). The method is based on homogeneous optical ($BVI$) near-infrared ($JHK$) mean magnitudes predicted period--luminosity--metallicity relations ($IJHK$) absolute magnitude--metallicity ($BV$). obtained solutions for three different RRL samples in $\omega$ Cen: first overtone (RRc,~90), fundamental (RRab,~80) global (RRc+RRab) which the period overtones were...
ABSTRACT Accurate metallicities of RR Lyrae are extremely important in constraining period–luminosity–metallicity (PLZ) relationships, particularly the near-infrared. We analyse 69 high-resolution spectra Galactic stars from Southern African Large Telescope. measure 58 these with typical uncertainties 0.15 dex. All but one this sample has accurate ($\sigma _{\varpi }\lesssim 10{{\ \rm per\ cent}}$) parallax Gaia. Combining new spectroscopic abundances similar determinations literature for 93...
We present new period-$ϕ_{31}$-[Fe/H] relations for first overtone RRL stars (RRc), calibrated over a broad range of metallicities ($-2.5 < \textrm{[Fe/H]}< 0.0$) utilizing the largest currently available set Galactic halo field with homogeneous spectroscopic metallicities. Our are defined in optical (ASAS-SN $V$-band) and, inaugurally, infrared (WISE $W1$ and $W2$ bands). $V$-band relation can reproduce individual RRc dispersion 0.30 dex entire metallicity our calibrator sample (an...
We present a detailed spectroscopic analysis of horizontal branch stars in the globular cluster NGC 3201. collected optical (4580-5330 A), high resolution (~34,000), signal-to-noise ratio (~200) spectra for eleven RR Lyrae and one red star with multifiber spectrograph M2FS at 6.5m Magellan telescope Las Campanas Observatory. From measured equivalent widths we derived atmospheric parameters abundance ratios {\alpha} (Mg, Ca, Ti), iron peak (Sc, Cr, Ni, Zn) s-process (Y) elements. found that...
We present a detailed spectroscopic analysis of RR Lyrae (RRL) variables in the globular cluster NGC 5139 (omega Cen). collected optical (4580-5330 A), high resolution (R = 34,000), signal-to-noise ratio (200) spectra for 113 RRLs with multi-fiber spectrograph M2FS at Magellan/Clay Telescope Las Campanas Observatory. also analysed 26,000) 122 FLAMES/GIRAFFE VLT, available ESO archive. The current sample doubles literature abundances and field Milky Way based on spectra. Equivalent width...
We provide homogeneous optical (UBVRI) and near-infrared (JHK) time series photometry for 254 cluster (omega Cen, M4) field RR Lyrae (RRL) variables. ended up with more than 551,000 measurements. For 94 fundamental (RRab) 51 first overtones (RRc) we a complete optical/NIR characterization (mean magnitudes, luminosity amplitudes, epoch of the anchor point). The NIR light curves these variables were adopted to new accurate light-curve templates both RRc (single period bin) RRab (three bins) J...
We determine the distances to Type Ia Supernova host galaxies M66 (NGC 3627) and M96 3368) of Leo I Group using Tip Red Giant Branch (TRGB) method. target stellar halos these Hubble Space Telescope ACS/WFC in F606W F814W bandpasses. By pointing we sample RGB stars predominantly Population II, minimize host-galaxy reddening, significantly reduce effects source crowding. Our absolute calibration I-band TRGB is based on a recent detached eclipsing binary distance Large Magellanic Cloud. With...
Stellar tidal streams provide an opportunity to study the motion and structure of disrupting galaxy as well gravitational potential its host. Streams around Milky Way are especially promising phase space positions individual stars will be measured by ongoing or upcoming surveys. Nevertheless, it remains a challenge accurately assess distances farther than 10 kpc from Sun, where we have poorest knowledge Galaxy's mass distribution. To address this present observations 32 candidate RR Lyrae in...
Abstract We collected the largest spectroscopic catalog of RR Lyrae (RRLs) including ≈20,000 high-, medium-, and low-resolution spectra for ≈10,000 RRLs. provide analytical forms radial velocity curve (RVC) templates. These were built using 36 RRLs (31 fundamental—split into three period bins—and five first-overtone pulsators) with well-sampled RVCs based on groups metallic lines (Fe, Mg, Na) four Balmer (H α , H β γ δ ). tackled long-standing problem reference epoch to anchor light-curve...