Key Projects

The discovery of the first gravitational-wave signal from a neutron-star merger together with the first kilonova in 2017, initiated the era of gravitational-wave - electromagnetic-wave multi-messenger astronomy. Using LCO, we obtained some of the earliest and best-sampled optical to near-infrared observations of the rapidly-evolving kilonova (not possible with almost any other facility). This discovery provided a wealth of insights into many open issues in astrophysics, including the neutron-star equation of state, the source of heavy elements in the Universe, and the first "standard-siren" constraints on the Hubble constant. Yet many open questions remain, most of which can be tied to the nature of the early optical emission. Competing models can be distinguished only with very early observations for a sample of events. We propose a key project to obtain such observations for ~15 new kilonovae to be discovered during the next gravitational-wave observing run (O4), and perhaps also the first observations of an optical counterpart to a neutron-star - black-hole merger. Our proposal for automatic ultra-rapid triggering of a galaxy-targeted search in the localization region following gravitational-wave events, and high-cadence follow-up of counterpart candidates, is based on a strategy that was highly successful for the 2017 event. While the ongoing observing run (O3) is solidifying the rate of NS mergers, O4, with its increased sensitivity and four detectors, will present us with the first opportunity to go from a single source to a sample of joint gravitational - electromagnetic wave events. LCO's unique robotic, global, and rapid-response capabilities are ideal for significantly advancing this exciting new field.

A new generation of wide-field photometric surveys offer us the opportunity to discover microlensing events across the entire sky. This unlocks the possibility to deliver new constraints on the mass functions of intrinsically faint objects in a range of different stellar environments across the Milky Way. Indeed, since the technique does not depend on light from the lens, microlensing is currently our best tool to detect the population of cold-planets, brown dwarfs and isolated stellar remnants at large distances from the Earth. However, the cadences of many wide-area surveys are insufficient to verify the lensing nature of the events and to accurately derive the physical properties of the lens system. We therefore propose to conduct photometric and spectroscopic follow-up of microlensing candidates detected in wide-area surveys. The unique capabilities of the Las Cumbres Observatory network to observe continuously with complementary apertures and instruments will ensure unique constraints on the lenses properties, especially their masses and distances.This project will start a systematic mapping of the faintest object in the entire Milky Way.

This LCO monitoring program is part of an ongoing effort to measure H_0 to 1% using the time delays in 40 strongly lensed quasars. This single-step technique needs no complex calibration and provides robust constraints on H_0. A 1% measurement of H_0 will both clarify the current discrepancy in H_0 between CMB and local distance ladder measurements and improve the Figure of Merit of any stage-IV survey by 40%. Our goal with LCO is to measure time delays in 15 Northern quasar lens systems from top-notch optical light curves obtained with daily cadence and high-SNR. Each time delay will be measured to 2-5% in one full visibility period of any specific lensed quasar. This will make the LCO the main Northern telescope of the TDCOSMO collaboration, working towards the goal of measuring H_0 to 1% in the next 3-4 years. The LCO monitoring will complement our current monitoring with the MPIA 2.2m telescope at ESO La Silla Observatory and allow US astronomers to fully participate in the premier world-wide consortium doing time-delay cosmography. With the same LCO data, we will build the line-of-sight mass distribution for each field, which is important to obtain an unbiased estimate of H_0. Together with existing HST imaging data and AO imaging data from the Keck observatory, the LCO time delays and line-of-sight mass distribution will add 15 new systems to the current TDCOSMO sample of 7 analyzed systems.

We propose a Key Project to investigate transient dimming of young stars by occulting circumstellar dust. Dimming can be up to several tens of percent and is detectable from the ground, but the diversity of this phenomenon has only been recently revealed by Kepler/K2. These stars, colloquially and collectively termed ``dipper'' stars, usually host circumstellar disks, and our investigation will probe of the structure, dynamics, and composition of material in the inner regions (<1 AU) of these disks in the range of separations where planets are found around older stars. Our studies will complement observations by interferometers such as ALMA, which cannot resolve the inner disks of stars even in the nearest star-forming regions. Occulting dust could be from asymmetric accretion onto the star, vertical structures produced by instabilities in highly inclined inner disks, clumpy dusty disk winds, gravitationally-bound planetesimal swarms, or evaporating planetesimals or ``exocomets''. The objectives of our Key Project are to determine the relative importance of each of these scenarios, detect any correlation with the properties of the stars and the evolutionary state of their disks, and obtain information about the composition of material that could be the building blocks of, or debris from planets. We will use LCO telescopes and obtain time-series photometry and spectroscopy of dimming events to achieve these objectives, i.e. by measuring the grain-size distribution of the dust, detecting any gas or volatilized elements associated with dust clouds, constraining the inclination of the motion of clouds with respect to stellar equators, and inferring the presence of massive sources on Keplerian orbits as potential sources of dust. Our Key Project will be organized into four campaigns: (1) multi-band monitoring of an ensemble of dipper stars, (2) triggered observations of individual dimming events using alerts from the Zwicky Transient Facility, Gaia, and the All-Sky Automated Survey for Supernovae; (3) time-critical observations of predicted quasi-periodic dimming events; and (4) observations with non-LCO telescopes to characterize the stars and disks studied by the other three campaigns. Our project exploits the unparalleled characteristics of the LCO telescope network: global longitudinal coverage to achieve near-continuous monitoring; access to the entire sky to study all of the nearest star-forming regions and young moving groups; automated, triggered scheduling of observations to study dimming events as they happen; and the NRES spectrograph network to make continuous measurements of the predicted Rossiter-McLaughlin effect due to the partial occultation of rapidly rotating young stars by dust. We have already obtained preliminary data demonstrating the feasibility of some parts of this project. Observations will be organized and scheduled using a Telescope Observing Management Systems (TOMS) that we will develop using the LCO TOMS Toolkit. Our international team is well positioned to conduct this project, with significant experience with the LCO telescope network, access to substantial non-LCO observing resources in both hemispheres to conduct necessary follow-up observations, and critical theoretical expertise to interpret these data and shed light on this mysterious phenomenon.

We propose to continue our highly-successful LCO AGN Intensive accretion Disk Reverberation Mapping (IDRM) program for another 3 years. Our previous LCO Key Projects have led to important advances in our picture of AGN central engines. This includes establishing for the first time that AGN interband continuum lags increase smoothly with wavelength throughout the optical/UV, consistent with τ ∝ λ^(4/3) as predicted by standard thin accretion disk theory, and discovery of excess lags especially around the Balmer jump, apparently due to diffuse continuum emission from the broad-line region. However the disk sizes appear too large and there is no simple relation between optical and X-ray variations, causing severe problems for the standard reprocessing model and forcing development of new models of AGN central engines. Here we propose IDRM monitoring of an additional six targets (and repeat/continued monitoring of two previously-observed ones), almost doubling the sample of AGN with high-quality IDRM monitoring, with special emphasis on targets with extreme Eddington ratios. Among our science goals are: i) measuring interband lags and flux changes in each band to estimate the size and structure (run of temperature with radius) of the disk, providing key tests of and constraints on the standard model; ii) quantifying the contribution of diffuse emission from the broad-line region to the delay spectrum; and iii) resolving the velocity field of the broad-line region to identify inflows and/or outflows. We will also establish the AGN Variability Archive (AVA), a legacy open-access database of reduced LCO (and other telescope) light curves and time-resolved spectra for all IDRM targets studied throughout our Key Projects, in order to enable the community to efficiently use these data to test their models.

We propose a continuation of the Global Supernova Project, a worldwide collaboration of more than 200 astronomers who have studied more than 750 supernovae and published approximately 100 papers over the last 6 years. We will observe 500 supernovae with LCO resources, and a subset with 36+ facilities and instruments, spanning X-ray to radio wavelengths. We will especially focus on preparing for the LSST era, creating filters for Alert Brokers (which will include our data) that enable us to pick particularly interesting, early, or fast-evolving targets from the ZTF and other data streams. This will allow us to study an emerging class of mysterious fast transients for the first time in detail, and expand on our pioneering work revealing the progenitors of SNe Ia, SNe II, and stripped envelope supernovae from observations taken just after explosion. We will also work to resolve the tension in the Hubble Constant by pairing our optical observations with IR data from SIRAH. With large samples of both common and exotic SNe we will break new ground studying luminosity functions, splitting SNe into subsamples by metallicity and other properties, simulating them, and finding outliers that reveal new physics.

We are interested in determining the frequency and nature of outbursts on small bodies across the Solar System. The LCO Outbursting Objects Key (LOOK) Project has two main objectives: 1) We will use the telescopes of the LCO Network to systematically monitor a sample of Dynamically New Comets (from the Oort cloud) over the whole sky. By studying this population's brightness and morphology changes as they pass through the inner Solar System, we can assess their evolutionary state (primitive vs. processed), identify targets for immediate or future follow-up (e.g., outburst vs. ambient coma composition), and, ultimately, better understand the behavior of these distant members as remnants of the early formation of the Solar System. It will also allow us to optimize the science return of the ESA Comet Interceptor mission and other future missions and gain a greater understanding of the interstellar objects that are just beginning to be discovered. 2) We will use the alerts and other data from the existing sky surveys such as ZTF, PanSTARRS1 & 2, Catalina and ATLAS to search for outburst activity in small bodies (comets, asteroids, centaurs) and rapidly respond to these outbursts with the telescopes of the LCO Network. This will enable us to better understand the nature of the outburst process, their frequency and magnitude distribution, and its evolution with time. Moreover, this will allow us to gain a better understanding of the physics of activity and outbursts on small bodies and the distribution of volatiles across the Solar System. This program exploits the synergy between current and future wide field surveys such as ZTF, PanSTARRS and LSST and rapid-response telescope networks such as LCO. Techniques, data reduction and analysis software developed during this Key Project and implemented on the ZTF survey and previous LCO programs will be an excellent “scale model” and testbed for what will be needed for the much larger number of objects coming from LSST.

The magnetic activity of the Sun varies roughly with a period of 11 years. However within this regularity, some differences from one cycle to the other can be noticed in terms of strength and length. On the stellar side, decades of spectroscopic observations from Mount Wilson and Lowell revealed that other stars also show regular activity cycles. In particular, this led to two distinct relationships between the length of the cycle and the rotation rate of the star. The position of the Sun compared to other solar-like stars have been questioned for some time. Is the Sun a peculiar star? Recently, it was suggested that the Sun is in that transition phase where magnetic braking stops, leading to higher surface rotation rates, and where magnetic activity cycles become longer. With this proposal, we aim at studying temporal evolution of stellar variability due to the magnetic activity of solar-like stars (from the main-sequence to subgiants). We propose to do a long-term monitoring of CaII H and K emission for a sample of 88 solar-like stars for which magnetic cycles have either been detected with other spectroscopic surveys or for which we expect shorter cycles or some magnetic activity. This will allow us to study cycle-to-cycle variations, secular trends in variability, and look for flat to variable transitions.

This 3-year Key Project is focused on transiting exoplanet science. We will use LCO observing facilities to observe transiting planet candidates detected by the TESS mission. Our primary goal is the study of small planets. Over the course of 3 years our photometric and spectroscopic observations will lead to the discovery of at least 100 small planets orbiting bright stars. This goal is well aligned with the TESS mission science goal and will result in some of the small planets most suitable for detailed characterization, including measurement of the planet mass and atmospheric characteristics. Our secondary science goal is the study of large gas-giant planets on relatively long orbital periods, longer than about 10 days. The number of such planets is still small while a large sample of these planets with measured radius, mass, and orbital eccentricity will shed light on principle questions about gas-giant planet formation and orbital evolution. We will also utilize the transit timing variation method to measure planets mass and orbital eccentricity in multi-planet systems. We expect to detect about 60 such gas-giant planets in this Key Project. As a whole this Key Project will establish LCO as a leader in the transiting exoplanets field.

We propose to measure the structure and emission profile of accretion disks around a diverse set of quasars, using intensive multi-band monitoring observations from the LCO network. Our program uses reverberation mapping to measure the light echoes and relative sizes of emission associated with different temperature regions across accretion disks. The quasar targets span 2.5 orders of magnitude in mass and accretion luminosity, such that our program will be the first to measure accretion disk structure as a function of diverse quasar properties. Critically, our targets also have reliable masses from the SDSS-RM program to enable the first measurements of the expected dependence of disk size on black hole mass. The broad redshift range (0<z<3) spans 3/4 of cosmic time and includes the peak of cosmic black hole mass assembly, and means that our observations effectively measure a broad range of the rest-frame disk emission. We use comprehensive simulations to validate that our observing design (0.5-day cadence, 100-day duration for each quasar) will reliably measure a broad range of disk reverberation lags. This program represents a unique application of intensive monitoring to a diverse set of quasars, and is only possible as an LCO Key Project.