Arturo Iván Gómez Ruiz

In 2026, the Event Horizon Telescope (EHT) carried out the first time-lapse monitoring campaign comprising a series of 18 observations of the 6.1 6 − 0.57 + 0.71 × 1 0 9 M ⊙ black hole at the center of M87 with a cadence of approximately twice per week over a few months, matched to the expected dynamical timescale. Here we present a first-look image from the campaign, reconstructed from a single four-minute scan obtained on 2026 April 3. The resulting image displays the now-familiar asymmetric ring morphology first revealed by the 2017 EHT observations and subsequently confirmed by observations obtained in 2018 and 2021. While representing only a very small subset of the full program, this image demonstrates a significant advance in the operational capabilities of the EHT. Through improvements in array operations, data transport and processing, the collaboration has reduced the interval between observation and imaging to only a few months, establishing the EHT as a facility capable of routinely undertaking time-domain studies of the dynamic universe at extremely high resolutions of ∼20 μ as.

Context. The L1157 outflow is a prototype of chemically active outflows in which to look for molecular species linked to complex chemistry. Aims. With the aim of imaging the large (parsec) scale structure of key prebiotic molecules, we aim to map the whole blue lobe of the L1157 outflow with the Large Millimeter Telescope (LMT), proving the potential of this facility to detect weak and extended molecular emission. Methods. Isocyanic acid (HNCO), an important precursor of complex chemistry, was chosen to be observed in its (4 _0,4 –3 _0,3 ) transition at 87.925 GHz with the SEQUOIA focal-plane array, covering an area of 3×3 arcmin ² centered at the position of the main shock L1157-B1, which included a large portion of the vicinity of the protostellar region. Results. The HNCO emission was detected not only from the outflow, it was also found tracing a structure of about 0.3 pc in length, corresponding to the filament from which the protostellar system was born. Conclusions. The HNCO molecule was found to be a tracer of the densest part of filaments in molecular clouds, and given its importance in the formation of more complex molecules, its presence in the cold, quiescent filamentary gas indicates that the building blocks of complex chemistry are already well established in stages prior to protostellar warming or shocks. By allowing the detection of structures related to the filament, these observations proved the LMT’s potential to map weak and extended components in molecular clouds.

Archaeoastronomy studies in Mesoamerica have focused above all on the architectural alignments of pre-Hispanic cultures, with few investigations that have extended to New Spain religious architecture. This work presents an investigation on the astronomical alignment of 44 New Spain temples in the Mayan area corresponding to the current states of Campeche and Yucatan. In the first instance, the global results obtained through the use of remote sensing techniques are shown, to later focus on a more detailed discussion on four of these churches in which in situ measurements could be carried out. As a global result, it was obtained that two thirds of the sample presented a solar orientation, with at least half of the cases possibly associated with orientations of pre-Hispanic inspiration, while in only three an equinoctial alignment consistent with the Catholic tradition of the sun of justice could be inferred. In the case studies, pre-Hispanic persistence was also dominant.

Event Horizon Telescope (EHT) images of the supermassive black hole M87* depict an asymmetric ring of emission. General relativistic magnetohydrodynamic (GRMHD) models of M87* and its accretion disk predict that the amplitude and location of the ring’s peak brightness asymmetry should fluctuate due to turbulence in the source plasma. We compare the observed distribution of brightness asymmetry amplitudes to the simulated distribution in GRMHD models, across varying black hole spin a _* . We show that, for strongly magnetized (MAD) models, three epochs of EHT data marginally disfavor ∣ a _* ∣ ≲ 0.2. This is consistent with the Blandford–Znajek model for M87’s jet, which predicts that M87* should have nonzero spin. We show quantitatively how future observations could improve spin constraints and discuss how improved spin constraints could distinguish between differing jet-launching mechanisms and black hole growth scenarios.

In Very-Long Baseline Interferometric arrays, nearly co-located stations probe the largest scales and typically cannot resolve the observed source. In the absence of large-scale structure, closure phases constructed with these stations are zero and, since they are independent of station-based errors, they can be used to probe data issues. Here, we show with an expansion about co-located stations, how these trivial closure phases become non-zero with brightness distribution on smaller scales than their short baseline would suggest. When applied to sources that are made up of a bright compact and large-scale diffuse component, the trivial closure phases directly measure the centroid relative to the compact source and higher-order image moments. We present a technique to measure these image moments with minimal model assumptions and validate it on synthetic Event Horizon Telescope (EHT) data. We then apply this technique to 2017 and 2018 EHT observations of M87* and find a weak preference for extended emission in the direction of the large-scale jet. We also apply it to 2021 EHT data and measure the source centroid about 1 mas northwest of the compact ring, consistent with the jet observed at lower frequencies.

We report three epochs of polarized images of M87* at 230 GHz using data from the Event Horizon Telescope (EHT) taken in 2017, 2018, and 2021. The baseline coverage of the 2021 observations is significantly improved through the addition of two new EHT stations: the 12 m Kitt Peak Telescope and the Northern Extended Millimetre Array (NOEMA). All observations result in images dominated by a bright, asymmetric ring with a persistent diameter of 43.9 ± 0.6 μas, consistent with expectations for lensed synchrotron emission encircling the apparent shadow of a supermassive black hole. We find that the total intensity and linear polarization of M87* vary significantly across the three epochs. Specifically, the azimuthal brightness distribution of the total intensity images varies from year to year, as expected for a stochastic accretion flow. However, despite a gamma-ray flare erupting in M87 quasi-contemporaneously to the 2018 observations, the 2018 and 2021 images look remarkably similar. The resolved linear polarization fractions in 2018 and 2021 peak at ∼5%, compared to ∼15% in 2017. The spiral polarization pattern on the ring also varies from year to year, including a change in the electric vector position angle helicity in 2021 that could reflect changes in the magnetized accretion flow or an external Faraday screen. The improved 2021 coverage also provides the first EHT constraints on jet emission outside the ring, on scales of ≲1 mas. Overall, these observations provide strong proof of the reliability of the EHT images and probe the dynamic properties of the horizon-scale accretion flow surrounding M87*.

We report on the results of the on-sky test and science demonstration conducted with the 2 mm receiver system, B4R, on the 50 m Large Millimeter Telescope (LMT), located at an altitude of 4600 m in Mexico. The B4R receiver was developed based on the dual-polarization sideband-separating mixer technology of the Atacama Large Millimeter/submillimeter Array and is equipped with a fast Fourier transform digital spectrometer, XFFTS. The primary science objective is the spectroscopic redshift identification of high-redshift dusty star-forming galaxies, complementing the existing 3 mm Redshift Search Receiver by enabling the detection of multiple carbon monoxide lines. Additionally, the B4R receiver broadens the range of science cases possible with the LMT, including astrochemistry, as the 2 mm band encompasses unique molecular lines such as deuterated molecules and shock tracers. During on-site commissioning in 2018 and 2019, we successfully demonstrated on-the-fly mapping and position-switching observations toward the Orion Molecular Cloud 1 and bright high-redshift dusty star-forming galaxies, respectively. We confirmed that the installed B4R system largely met its basic performance specifications. Furthermore, we measured the LMT’s aperture efficiencies across the entire B4R frequency range (130–160 GHz), finding them to be roughly consistent with expectations based on a surface accuracy of 100 μ m and the receiver optics design. These results with the B4R will enable the most sensitive single-dish spectroscopic observations at 2 mm using the LMT.