More Like this

1. LISA Galactic binaries in the Roman Galactic Bulge Time-Domain Survey

   https://doi.org/10.1093/mnras/stad2290  

   Digman, Matthew C; Hirata, Christopher M (August 2023, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Short-period Galactic white dwarf binaries detectable by Laser Interferometer Space Antenna are the only guaranteed persistent sources for multimessenger gravitational-wave astronomy. Large-scale surveys in the 2020s present an opportunity to conduct preparatory science campaigns to maximize the science yield from future multimessenger targets. The Nancy Grace Roman Space Telescope Galactic Bulge Time-Domain Survey will (in its Reference Survey design) image seven fields in the Galactic Bulge approximately 40 000 times each. Although the Reference Survey cadence is optimized for detecting exoplanets via microlensing, it is also capable of detecting short-period white dwarf binaries. In this paper, we present forecasts for the number of detached short-period binaries the Roman Galactic Bulge Time-Domain Survey will discover and the implications for the design of electromagnetic surveys. Although population models are highly uncertain, we find a high probability that the baseline survey will detect of the order of ∼5 detached white dwarf binaries. The Reference Survey would also have a $${\gtrsim} 20\,{\rm per\,cent}$$ chance of detecting several known benchmark white dwarf binaries at the distance of the Galactic Bulge. 

   more » « less
2. The La Silla Schmidt Southern Survey

   https://doi.org/10.1088/1538-3873/ae02c5  

   Miller, Adam A; Abrams, Natasha S; Aldering, Greg; Anand, Shreya; Angus, Charlotte R; Arcavi, Iair; Baltay, Charles; Bauer, Franz E; Brethauer, Daniel; Bloom, Joshua S; et al (September 2025, Publications of the Astronomical Society of the Pacific)

   Abstract We present the La Silla Schmidt Southern Survey (LS4), a new wide-field, time-domain survey to be conducted with the 1 m ESO Schmidt telescope. The 268 megapixel LS4 camera mosaics 32 2k × 4k fully depleted CCDs, providing a ∼20 deg²field of view with 1^″pixel⁻¹resolution. The LS4 camera will have excellent performance at longer wavelengths: in a standard 45 s exposure the expected 5σlimiting magnitudes ing,i,zare ∼21.5, ∼20.9, and ∼20.3 mag (AB), respectively. The telescope design requires a novel filter holder that fixes different bandpasses over each quadrant of the detector. Two quadrants will haveiband, while the other two will begandzband with color information obtained by dithering targets across the different quadrants. The majority (90%) of the observing time will be used to conduct a public survey that monitors the extragalactic sky at both moderate (3 days) and high (1 day) cadence, as well as focused observations within the Galactic plane and bulge. Alerts from the public survey will be broadcast to the community via established alert brokers. LS4 will run concurrently with the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST). The combination of LS4+LSST will enable detailed holistic monitoring of many nearby transients: high-cadence LS4 observations will resolve the initial rise and peak of the light curve while less-frequent but deeper observations by LSST will characterize the years before and after explosion. Here, we summarize the primary science objectives of LS4 including microlensing events in the Galaxy, extragalactic transients powered by massive black holes or stellar explosions, the search for electromagnetic counterparts to multi-messenger events, and supernova cosmology. 

   more » « less
3. Cosmology with the Roman Space Telescope : synergies with the Rubin Observatory Legacy Survey of Space and Time

   https://doi.org/10.1093/mnras/stab533  

   Eifler, Tim; Simet, Melanie; Krause, Elisabeth; Hirata, Christopher; Huang, Hung-Jin; Fang, Xiao; Miranda, Vivian; Mandelbaum, Rachel; Doux, Cyrille; Heinrich, Chen; et al (August 2021, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We explore synergies between the Nancy Grace Roman Space Telescope and the Vera Rubin Observatory’s Legacy Survey of Space and Time (LSST). Specifically, we consider scenarios where the currently envisioned survey strategy for the Roman Space Telescope’s High Latitude Survey (HLS reference), i.e. 2000 deg2 in four narrow photometric bands is altered in favour of a strategy of rapid coverage of the LSST area (to full LSST depth) in one band. We find that in only five months, a survey in the W-band can cover the full LSST survey area providing high-resolution imaging for >95 per cent of the LSST Year 10 gold galaxy sample. We explore a second, more ambitious scenario where the Roman Space Telescope spends 1.5 yr covering the LSST area. For this second scenario, we quantify the constraining power on dark energy equation-of-state parameters from a joint weak lensing and galaxy clustering analysis. Our survey simulations are based on the Roman Space Telescope exposure-time calculator and redshift distributions from the CANDELS catalogue. Our statistical uncertainties account for higher order correlations of the density field, and we include a wide range of systematic effects, such as uncertainties in shape and redshift measurements, and modelling uncertainties of astrophysical systematics, such as galaxy bias, intrinsic galaxy alignment, and baryonic physics. We find a significant increase in constraining power for the joint LSST + HLS wide survey compared to LSST Y10 (FoMHLSwide = 2.4 FoMLSST) and compared to LSST + HLS (FoMHLSwide = 5.5 FoMHLSref). 

   more » « less
4. 60 Microlensing Events from the Three Years of Zwicky Transient Facility Phase One

   https://doi.org/10.3847/1538-4357/acba8f  

   Medford, Michael S.; Abrams, Natasha S.; Lu, Jessica R.; Nugent, Peter; Lam, Casey Y. (April 2023, The Astrophysical Journal)

   Abstract Microlensing events have historically been discovered throughout the Galactic bulge and plane by surveys designed solely for that purpose. We conduct the first multiyear search for microlensing events on the Zwicky Transient Facility (ZTF), an all-sky optical synoptic survey that observes the entire visible northern sky every few nights. We discover 60 high-quality microlensing events in the 3 yr of ZTF-I using the bulk lightcurves in the ZTF Public Data Release 5.19 of our events are found outside of the Galactic plane (∣ b ∣ ≥ 10°), nearly doubling the number of previously discovered events in the stellar halo from surveys pointed toward the Magellanic Clouds and the Andromeda galaxy. We also record 1558 ongoing candidate events as potential microlensing that can continue to be observed by ZTF-II for identification. The scalable and computationally efficient methods developed in this work can be applied to future synoptic surveys, such as the Vera C. Rubin Observatory’s Legacy Survey of Space and Time and the Nancy Grace Roman Space Telescope, as they attempt to find microlensing events in even larger and deeper data sets. 

   more » « less
5. The PRime-focus Infrared Microlensing Experiment (PRIME): First Results

   https://doi.org/10.3847/1538-3881/ae14f5  

   Sumi, Takahiro; Buckley, David_A H; Kutyrev, Alexander S; Tamura, Motohide; Bennett, David P; Bond, Ian A; Cataldo, Giuseppe; Durbak, Joseph M; Cenko, S Bradley; Fixsen, Dale; et al (November 2025, The Astronomical Journal)

   Abstract We present the description of the instruments and the first results of the PRime-focus Infrared Microlensing Experiment (PRIME). PRIME is the first dedicated near-infrared (NIR) microlensing survey telescope, and is located at the South African Astronomical Observatory in Sutherland, South Africa. Among its class, it offers one of the widest fields of view in the NIR regime. PRIME’s main goals are (1) to study planetary formation by measuring the frequency and mass function of planets. In particular, we compare results from the central Galactic bulge (GB), accessible only in the NIR by PRIME, with those from the outer GB by optical surveys. (2) To conduct concurrent observations with NASA’s Nancy Grace Roman Space Telescope. Due to the different lines of sight between the ground and space, we detect slight variations in light curves, known as “space-based parallax.” This effect allows us to measure the mass of lens systems and their distance from the Earth. It is the only method to measure the mass of free-floating planets down to Earth mass. We began the GB survey in 2024 February and analyzed images through 2025 June 1, identifying 486 microlensing candidates and over a thousand variable stars, including Mira variables, which are useful for studying the Galactic structure. We issue real-time alerts for follow-up observations, supporting exoplanet searches and the chemical evolution studies in the GB. During the off-bulge season, we conduct an all-sky grid survey and target-of-opportunity observations of transients, including gravitational-wave events,γ-ray bursts, and other science. 

   more » « less