Steve Heathcote

Blue large-amplitude pulsators (BLAPs) are rare, hot, short-period pulsating stars whose rapid oscillations provide a unique probe of stellar interiors and atmospheres. In this paper, we study two short-period BLAPs in the Galactic bulge, Optical Gravitational Lensing Experiment (OGLE)-BLAP-142 ( P ≈ 6.6 minutes) and OGLE-BLAP-148 ( P ≈ 7.5 minutes), by combining light curves from the OGLE, KMTNet, and DREAMS surveys, spanning 17 yr with cadences ranging from minutes to hours to days. We perform generalized Lomb–Scargle periodogram analyses of their light curves and identify, for each BLAP, three closely spaced pulsation modes separated by ∼1%. The dominant mode can switch within timescales of order a year, accompanied by a likely blueward color shift (∼0.1–0.2 mag). The yearly period excursions of the resolved mode families imply apparent ∣ P ̇ / P ∣ values of order 10 ⁻⁶ –10 ⁻⁴ yr ⁻¹ , large enough to mimic or exceed smooth evolutionary period changes. One mode family in OGLE-BLAP-148 shows a coherent decade-long drift at the ∼10 ⁻⁵ yr ⁻¹ level, but its failure to extrapolate to the earliest and latest epochs suggests a transient mode-family drift rather than secular evolution. Such close-spaced multiple pulsations and mode switching may be common among BLAPs with periods shorter than 10 minutes, and their physical origin remains unclear.

We present the analysis of the microlensing event KMT-2026-BLG-0083, which was independently detected by the KMTNet, OGLE, and PRIME surveys and also monitored by the DREAMS survey. The combined data provide dense coverage of two distinct short-duration anomalies in the light curve that cannot be reproduced by a standard binary-lens model. Independent analyses of the two anomalies indicate that each is produced by a planetary companion to the lens, motivating a triple-lens interpretation. The modeling yields two pairs of degenerate solutions arising from the well-known inner–outer degeneracy, with each pair exhibiting two local solutions depending on whether the source passes above or below the distant planetary companion. The preferred model indicates two giant planets with mass ratios q ₂ = (5.25 ± 0.08) × 10 ⁻³ and q ₃ = (3.04 ± 0.24) × 10 ⁻³ orbiting a common host. Bayesian analysis indicates that the host is an M-dwarf star with a mass of 0.4 8 − 0.28 + 0.36 M ⊙ , hosting two giant planets with masses of 2.6 5 − 1.55 + 1.96 M J and 1.5 4 − 0.90 + 1.14 M J . The projected planet–host separations are 10 . 6 − 2.2 + 1.7 au and 1 . 7 − 0.3 + 0.3 au, placing the inner planet near the host’s snow line and the outer planet at a substantially larger separation. Thus, KMT-2026-BLG-0083L becomes the seventh confirmed multiple-planet system discovered through gravitational microlensing, providing another example of a cold giant planetary system orbiting a subsolar-mass star.

The DECam Rogue Earths and Mars Survey (DREAMS), a NOIRLab survey program, has been conducting a 3 yr survey covering a 5 deg ² area in the Galactic bulge (roughly spanning − 1 . ° 2 ≲ ℓ ≲ + 2 . ° 1 and − 2 . ° 8 ≲ b ≲ − 0 . ° 6 ) since 2025 June. Its primary science goal is to detect low-mass free-floating planets through microlensing, while its minute-level cadence (20–40 hr ⁻¹ in the z band and 4–8 hr ⁻¹ in the r band) also enables the detection and characterization of rapid phenomena on timescales of minutes to hours such as stellar flares and pulsating stars. The survey reaches a single-exposure depth of z _AB ∼ 22 mag, about 2 mag deeper than previous bulge time-domain surveys. We present the data reduction and calibration of the DREAMS observations obtained in 2025 and introduce the first DREAMS data release (DR1; https://astro.westlake.edu.cn/dreams/ ). DR1 includes 1856 z -band observations and 325 r -band observations for 59,372,789 stars. The DREAMS DR1 catalog contains about twice as many stars as any previous catalog covering the same 5 deg ² area. We present DREAMS light curves for a known blue large-amplitude pulsator and a known low-amplitude transiting system to demonstrate the survey’s capabilities. We also perform a pilot search for short-duration variables over about 0.4% of the DR1 sample, identifying one new short microlensing event, two stellar flares, and 24 new short variables. This suggests that DREAMS DR1 may contain hundreds of stellar flares and thousands of previously unknown short variables.

We present observations and analysis of the bound planetary microlensing event KMT-2025-BLG-1616. The planetary signal was captured by the Korea Microlensing Telescope Network and the Dark Energy Camera Rogue Earths and Mars Survey (DREAMS). DREAMS’s minute-cadence observations break the central/resonant degeneracy in the binary-lens models. The color of the faint source star ( I = 22) is measured from the DREAMS’s r − z color. The planetary system has a planet-host mass ratio of q ∼ 5 × 10 ⁻⁴ . A Bayesian analysis yields a host-star mass of ∼0.3 M _⊙ , a planetary mass of ∼40 M _⊕ , a projected planet-host separation of ∼1.6 au, and a lens distance of ∼7.5 kpc. Based on the photometric precision achieved by DREAMS for this event, we simulate free-floating planet (FFP) detections and find that DREAMS is sensitive to Mars-mass FFPs in the Galactic bulge and Moon-mass FFPs in the Galactic disk.

GRB 250702B was the longest gamma-ray burst ever detected, with a duration that challenges standard collapsar models and suggests an exotic progenitor. We collected a rich set of optical and infrared follow-up observations of its rapidly fading afterglow using a suite of telescopes including the W. M. Keck Observatory, the Gemini telescopes, the Magellan Baade Telescope, the Victor M. Blanco 4 m telescope, and the Fraunhofer Telescope at Wendelstein Observatory. Our analysis reveals that the afterglow emission is well described by forward shock emission from a highly obscured relativistic jet. Deep photometric observations of the host galaxy reveal a massive (10 ^10.66 M _⊙ ), dusty, and extremely asymmetric system that is consistent with two galaxies undergoing a major merger. The galactocentric offset, host galaxy properties, and jet characteristics disfavor a jetted tidal disruption event (TDE) around a supermassive black hole but do not definitively distinguish between competing progenitor scenarios. We find that the afterglow and host are consistent with a range of progenitors, including an atypical collapsar, a merger between a helium star and a stellar-mass black hole, the disruption of a star by a stellar-mass compact object (micro-TDE), and the tidal disruption of a star by an off-nuclear intermediate-mass black hole.

SPIE Digital Library Proceedings

We report the discovery of a new Herbig–Haro jet, HH 1165, in SOAR narrow-band imaging of the vicinity of the σ Orionis cluster. HH 1165 shows a spectacular extended and collimated spatial structure, with a projected length of 0.26 pc, a bent C-shaped morphology, multiple knots, and fragmented bow shocks at the apparent ends of the flow. The Hα image shows a bright halo with a clumpy distribution of material seen around the driving source, and curved reflection nebulosity tracing the outflow cavities. The driving source of HH 1165 is a Class I proto-brown dwarf, Mayrit 1701117 (M1701117), with a total (dust+gas) mass of ∼36 M _Jup and a bolometric luminosity of ∼0.1 L _⊙. High-resolution VLT/UVES spectra of M1701117 show a wealth of emission lines indicative of strong outflow and accretion activity. SOAR/Goodman low-resolution spectra along the jet axis show an asymmetrical morphology for HH 1165. We find a puzzling picture wherein the northwest part exhibits a classical HH jet running into a pre-dominantly neutral medium, while the southern part resembles an externally irradiated jet. The C-shaped bending in HH 1165 may be produced by the combined effects from the massive stars in the ionization front to the east, the σ Orionis core to the west, and the close proximity to the B2-type star HR 1950. HH 1165 shows all of the signatures to be considered as a scaled-down version of parsec-length HH jets, and can be termed as the first sub-stellar analog of a protostellar HH jet system.