We measure rotational broadening in spectra taken by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey to characterise the relationship between stellar multiplicity and ...rotation. We create a sample of 2786 giants and 24 496 dwarfs with stellar parameters and multiple radial velocities from the APOGEE pipeline, projected rotation speeds \vsini\ determined from our own pipeline, and distances, masses, and ages measured by Sanders \& Das. We use the statistical distribution of the maximum shift in the radial velocities, \drvm, as a proxy for the close binary fraction to explore the interplay between stellar evolution, rotation, and multiplicity. Assuming that the minimum orbital period allowed is the critical period for Roche Lobe overflow and rotational synchronization, we calculate theoretical upper limits on expected \vsini\ and \drvm\ values. These expectations agree with the positive correlation between the maximum \drvm\ and \vsini\ values observed in our sample as a function of \logg. We find that the fast rotators in our sample have a high occurrence of short-period (\(\log(P/\text{d})\lesssim 4\)) companions. We also find that old, rapidly-rotating main sequence stars have larger completeness-corrected close binary fractions than their younger peers. Furthermore, rapidly-rotating stars with large \drvm\ consistently show differences of 1-10 Gyr between the predicted gyrochronological and measured isochronal ages. These results point towards a link between rapid rotation and close binarity through tidal interactions. We conclude that stellar rotation is strongly correlated with stellar multiplicity in the field, and caution should be taken in the application of gyrochronology relations to cool stars.
The eighteenth data release of the Sloan Digital Sky Surveys (SDSS) is the first one for SDSS-V, the fifth generation of the survey. SDSS-V comprises three primary scientific programs, or "Mappers": ...Milky Way Mapper (MWM), Black Hole Mapper (BHM), and Local Volume Mapper (LVM). This data release contains extensive targeting information for the two multi-object spectroscopy programs (MWM and BHM), including input catalogs and selection functions for their numerous scientific objectives. We describe the production of the targeting databases and their calibration- and scientifically-focused components. DR18 also includes ~25,000 new SDSS spectra and supplemental information for X-ray sources identified by eROSITA in its eFEDS field. We present updates to some of the SDSS software pipelines and preview changes anticipated for DR19. We also describe three value-added catalogs (VACs) based on SDSS-IV data that have been published since DR17, and one VAC based on the SDSS-V data in the eFEDS field.
Draco C1 is a known symbiotic binary star system composed of a carbon red giant and a hot, compact companion -- likely a white dwarf -- belonging to the Draco dwarf spheroidal galaxy. From ...near-infrared spectroscopic observations taken by the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2), part of Sloan Digital Sky Survey IV, we provide updated stellar parameters for the cool, giant component, and constrain the temperature and mass of the hot, compact companion. Prior measurements of the periodicity of the system, based on only a few epochs of radial velocity data or relatively short baseline photometric observations, were sufficient only to place lower limits on the orbital period (\(P > 300\) days). For the first time, we report precise orbital parameters for the binary system: With 43 radial velocity measurements from APOGEE spanning an observational baseline of more than 3 years, we definitively derive the period of the system to be \(1220.0^{+3.7}_{-3.5}\) days. Based on the newly derived orbital period and separation of the system, together with estimates of the radius of the red giant star, we find that the hot companion must be accreting matter from the dense wind of its evolved companion.
We use observations from the APOGEE survey to explore the relationship
between stellar parameters and multiplicity. We combine high-resolution repeat
spectroscopy for 41,363 dwarf and subgiant stars ...with abundance measurements
from the APOGEE pipeline and distances and stellar parameters derived using
\textit{Gaia} DR2 parallaxes from \cite{Sanders2018} to identify and
characterise stellar multiples with periods below 30 years, corresponding to
\drvm$\gtrsim$ 3 \kms, where \drvm\ is the maximum APOGEE-detected shift in the
radial velocities. Chemical composition is responsible for most of the
variation in the close binary fraction in our sample, with stellar parameters
like mass and age playing a secondary role. In addition to the previously
identified strong anti-correlation between the close binary fraction and \feh\,
we find that high abundances of $\alpha$ elements also suppress multiplicity at
most values of \feh\ sampled by APOGEE. The anti-correlation between $\alpha$
abundances and multiplicity is substantially steeper than that observed for Fe,
suggesting C, O, and Si in the form of dust and ices dominate the opacity of
primordial protostellar disks and their propensity for fragmentation via
gravitational stability. Near \feh{} = 0 dex, the bias-corrected close binary
fraction ($a<10$ au) decreases from $\approx$ 100 per cent at \alh{} = $-$0.2
dex to $\approx$ 15 per cent near \alh{} = 0.08 dex, with a suggestive turn-up
to $\approx$20 per cent near \alh{} = 0.2. We conclude that the relationship
between stellar multiplicity and chemical composition for sun-like dwarf stars
in the field of the Milky Way is complex, and that this complexity should be
accounted for in future studies of interacting binaries.
Many problems in contemporary astrophysics---from understanding the formation of black holes to untangling the chemical evolution of galaxies---rely on knowledge about binary stars. This, in turn, ...depends on discovery and characterization of binary companions for large numbers of different kinds of stars in different chemical and dynamical environments. Current stellar spectroscopic surveys observe hundreds of thousands to millions of stars with (typically) few observational epochs, which allows binary discovery but makes orbital characterization challenging. We use a custom Monte Carlo sampler (The Joker) to perform discovery and characterization of binary systems through radial-velocities, in the regime of sparse, noisy, and poorly sampled multi-epoch data. We use it to generate posterior samplings in Keplerian parameters for 232,531 sources released in APOGEE Data Release 16. Our final catalog contains 19,635 high-confidence close-binary (P < few years, a < few AU) systems that show interesting relationships between binary occurrence rate and location in the color-magnitude diagram. We find notable faint companions at high masses (black-hole candidates), at low masses (substellar candidates), and at very close separations (mass-transfer candidates). We also use the posterior samplings in a (toy) hierarchical inference to measure the long-period binary-star eccentricity distribution. We release the full set of posterior samplings for the entire parent sample of 232,531 stars. This set of samplings involves no heuristic "discovery" threshold and therefore can be used for myriad statistical purposes, including hierarchical inferences about binary-star populations and sub-threshold searches.
Multi-epoch radial velocity measurements of stars can be used to identify stellar, sub-stellar, and planetary-mass companions. Even a small number of observation epochs can be informative about ...companions, though there can be multiple qualitatively different orbital solutions that fit the data. We have custom-built a Monte Carlo sampler (The Joker) that delivers reliable (and often highly multi-modal) posterior samplings for companion orbital parameters given sparse radial-velocity data. Here we use The Joker to perform a search for companions to 96,231 red-giant stars observed in the APOGEE survey (DR14) with \(\geq 3\) spectroscopic epochs. We select stars with probable companions by making a cut on our posterior belief about the amplitude of the stellar radial-velocity variation induced by the orbit. We provide (1) a catalog of 320 companions for which the stellar companion properties can be confidently determined, (2) a catalog of 4,898 stars that likely have companions, but would require more observations to uniquely determine the orbital properties, and (3) posterior samplings for the full orbital parameters for all stars in the parent sample. We show the characteristics of systems with confidently determined companion properties and highlight interesting systems with candidate compact object companions.
This paper documents the sixteenth data release (DR16) from the Sloan Digital Sky Surveys; the fourth and penultimate from the fourth phase (SDSS-IV). This is the first release of data from the ...southern hemisphere survey of the Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2); new data from APOGEE-2 North are also included. DR16 is also notable as the final data release for the main cosmological program of the Extended Baryon Oscillation Spectroscopic Survey (eBOSS), and all raw and reduced spectra from that project are released here. DR16 also includes all the data from the Time Domain Spectroscopic Survey (TDSS) and new data from the SPectroscopic IDentification of ERosita Survey (SPIDERS) programs, both of which were co-observed on eBOSS plates. DR16 has no new data from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey (or the MaNGA Stellar Library "MaStar"). We also preview future SDSS-V operations (due to start in 2020), and summarize plans for the final SDSS-IV data release (DR17).
Data and analysis methodology used for the SDSS/APOGEE Data Releases 13 and 14 are described, highlighting differences from the DR12 analysis presented in Holtzman (2015). Some improvement in the ...handling of telluric absorption and persistence is demonstrated. The derivation and calibration of stellar parameters, chemical abundances, and respective uncertainties are described, along with the ranges over which calibration was performed. Some known issues with the public data related to the calibration of the effective temperatures (DR13), surface gravity (DR13 and DR14), and C and N abundances for dwarfs (DR13 and DR14) are highlighted. We discuss how results from a data-driven technique, The Cannon (Casey 2016), are included in DR14, and compare those with results from the APOGEE Stellar Parameters and Chemical Abundances Pipeline (ASPCAP). We describe how using The Cannon in a mode that restricts the abundance analysis of each element to regions of the spectrum with known features from that element leads to Cannon abundances can lead to significantly different results for some elements than when all regions of the spectrum are used to derive abundances.
We use the multi-epoch radial velocities acquired by the APOGEE survey to perform a large scale statistical study of stellar multiplicity for field stars in the Milky Way, spanning the evolutionary ...phases between the main sequence and the red clump. We show that the distribution of maximum radial velocity shifts (\drvm) for APOGEE targets is a strong function of \logg, with main sequence stars showing \drvm\ as high as \(\sim\)300 \kms, and steadily dropping down to \(\sim\)30 \kms\ for \logg\(\sim\)0, as stars climb up the Red Giant Branch (RGB). Red clump stars show a distribution of \drvm\ values comparable to that of stars at the tip of the RGB, implying they have similar multiplicity characteristics. The observed attrition of high \drvm\ systems in the RGB is consistent with a lognormal period distribution in the main sequence and a multiplicity fraction of 0.35, which is truncated at an increasing period as stars become physically larger and undergo mass transfer after Roche Lobe Overflow during H shell burning. The \drvm\ distributions also show that the multiplicity characteristics of field stars are metallicity dependent, with metal-poor (Fe/H\(\lesssim-0.5\)) stars having a multiplicity fraction a factor 2-3 higher than metal-rich (Fe/H\(\gtrsim0.0\)) stars. This has profound implications for the formation rates of interacting binaries observed by astronomical transient surveys and gravitational wave detectors, as well as the habitability of circumbinary planets.
The Apache Point Observatory Galactic Evolution Experiment (APOGEE) has observed \(\sim\)600 transiting exoplanets and exoplanet candidates from \textit{Kepler} (Kepler Objects of Interest, KOIs), ...most with \(\geq\)18 epochs. The combined multi-epoch spectra are of high signal-to-noise (typically \(\geq\)100) and yield precise stellar parameters and chemical abundances. We first confirm the ability of the APOGEE abundance pipeline, ASPCAP, to derive reliable Fe/H and effective temperatures for FGK dwarf stars -- the primary \textit{Kepler} host stellar type -- by comparing the ASPCAP-derived stellar parameters to those from independent high-resolution spectroscopic characterizations for 221 dwarf stars in the literature. With a sample of 282 close-in (\(P<100\) days) KOIs observed in the APOGEE KOI goal program, we find a correlation between orbital period and host star Fe/H characterized by a critical period, \(P_\mathrm{crit}\)= \(8.3^{+0.1}_{-4.1}\) days, below which small exoplanets orbit statistically more metal-enriched host stars. This effect may trace a metallicity dependence of the protoplanetary disk inner-radius at the time of planet formation or may be a result of rocky planet ingestion driven by inward planetary migration. We also consider that this may trace a metallicity dependence of the dust sublimation radius, but find no statistically significant correlation with host \(T_\mathrm{eff}\) and orbital period to support such a claim.
