Southern Astrophysical Research Research Articles

First Detection of Outflowing Gas in the Outskirts of the Broad-line Region in 1H 0707−495* *Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia e Inovações do Brasil (MCTI/LNA), the US National Science Foundation's NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State

We use near-infrared spectroscopy covering simultaneously the zJHK bands to look for outflowing gas from the nuclear environment of 1H 0707−495 taking advantage that this region is dominated by low-ionization broad-line region lines, most of them isolated. We detect broad components in H i, Fe ii, and O i, at rest to the systemic velocity, displaying FWHM values of ∼500 km s−1, consistent with its classification as a narrow-line Seyfert 1 active galactic nucleus. Moreover, most lines display a conspicuous blue-asymmetric profile, modeled using a blueshifted component, whose velocity shift reaches up to ∼826 km s−1. This last feature can be interpreted in terms of outflowing gas already observed in X-ray and UV lines in 1H 0707−495 but not detected before in the low-ionization lines. We discuss the relevance of our findings within the framework of the wind scenario already proposed for this source and suggest that the wind extends well into the narrow-line region owing to the observation of a blueshifted component in the forbidden line of [S iii] λ9531.

Characterization and Optimization of Skipper CCDs for the SOAR Integral Field Spectrograph

We present results from the characterization and optimization of Skipper charge-coupled devices (CCDs) for use in a focal plane prototype for the Southern Astrophysical Research Integral Field Spectrograph (SIFS). We tested eight Skipper CCDs and selected six for SIFS based on performance results. The Skipper CCDs are 6k × 1k, 15 μm pixels, thick, fully depleted, p-channel devices that have been thinned to ∼250 μm, backside processed, and treated with an anti-reflective coating. We demonstrate a single-sample readout noise of <4.3 e− rms pixel−1 in all amplifiers. We optimize the readout sequence timing to achieve a readout noise of 0.5 e− rms pixel−1 after 74 non-destructive measurements, which can be accomplished in a region covering 5% of the detector area in a readout time of <4 minutes. We demonstrate single-photon-counting in all 24 amplifiers (four amplifiers per detector) with a readnoise of σ N ∼ 0.18 e− rms pixel−1 after N samp = 400 samples, and we constrain the degree of nonlinearity to be ≲1% at low signal levels (0 e− to 50 e−). Clock-induced charge (CIC) remains an important issue when the Skipper CCD is configured to provide a large full-well capacity. We achieve a CIC rate of <1.45 × 10−3 e− pixel−1 frame−1 for a full-well capacity of ∼900 e−, which increases to a CIC rate of ∼3 e− pixel−1 frame−1 for full-well capacities ∼40,000–65,000 e−. We also perform conventional CCD characterization measurements such as charge transfer inefficiency (3.44 × 10−7 on average), dark current (∼2 × 10−4 e− pixel−1 s−1), photon transfer curves, cosmetic defects (<0.45% “bad” pixels), and charge diffusion (point-spread function < 7.5 μm) to verify that these properties are consistent with expectations from conventional p-channel CCDs used for astronomy. Furthermore, we provide the first measurements of the brighter-fatter effect and absolute quantum efficiency (≳80% between 450 and 980 nm; ≳90% between 600 and 900 nm) using Skipper CCDs.

Powerful Radio Sources in the Southern Sky. III. First Results of the Optical Spectroscopic Campaign

We recently built the G4Jy-3CRE catalog of extragalactic radio sources. This catalog lists 264 powerful radio sources selected with similar criteria to those of the revised Third Cambridge Catalog, but visible from the Southern Hemisphere. A literature search revealed that 119 sources in the G4Jy-3CRE catalog (i.e., 45%) lack a firm spectroscopic redshift measurement. Here, we present a campaign aimed at acquiring optical spectra of G4Jy-3CRE sources and measuring their redshifts. We used single-slit observations obtained with the Víctor Blanco Telescope, the New Technology Telescope, the Southern Astrophysical Research Telescope, and the 2.1 m telescope of the Observatorio Astronómico Nacional at San Pedro Mártir, Mexico. In addition, we analyzed Very Large Telescope/MUSE archival observations. From these observations, we report the spectra and redshifts of 93 sources, 42 of which are the first optical spectra and redshift determinations for the respective sources. With our new data, approximately 71% of the sources in the G4Jy-3CRE catalog now have firm spectroscopic redshift measurements. This data set will be the basis of our future analysis of the optical properties of the G4Jy-3CRE catalog.

XQz5: a new ultraluminous z ∼ 5 quasar legacy sample

ABSTRACT Bright quasar samples at high redshift are useful for investigating active galactic nuclei evolution. In this study, we describe XQz5, a sample of 83 ultraluminous quasars in the redshift range 4.5 &amp;lt; z &amp;lt; 5.3 with optical and near-infrared spectroscopic observations, with unprecedented completeness at the bright end of the quasar luminosity function. The sample is observed with the Southern Astrophysical Research Telescope, the Very Large Telescope, and the Australian National University 2.3 m Telescope, resulting in a high-quality, moderate-resolution spectral atlas of the brightest known quasars within the redshift range. We use established virial mass relations to derive the black hole masses by measuring the observed Mg ii λ2799 Å emission line and we estimate the bolometric luminosity with bolometric corrections to the ultraviolet continuum. Comparisons to literature samples show that XQz5 bridges the redshift gap between other X-shooter quasar samples, XQ-100 and XQR-30, and is a brighter sample than both. Luminosity-matched lower redshift samples host more massive black holes, which indicate that quasars at high redshift are more active than their counterparts at lower redshift, in concordance with recent literature.

Mass Ratio of Single-line Spectroscopic Binaries with Visual Orbits Using Bayesian Inference and Suitable Priors* *Based in part on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovaçãoes (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at

We present orbital elements for 22 single-line binaries, nine of them studied for the first time, determined from a joint spectroscopic and astrometric solution. The astrometry is based on interferometric measurements obtained with the HRCam Speckle camera on the SOAR 4.1 m telescope at Cerro Pachon, Chile, supplemented with historical data. The spectroscopic observations were secured using Echelle spectrographs (FEROS, FIDEOS, and HARPS) at La Silla, Chile. A comparison of our orbital elements and systemic velocities with previous studies, including Gaia radial velocities, shows the robustness of our estimations. By adopting suitable priors of the trigonometric parallax and spectral type of the primary component, and using a Bayesian inference methodology developed by our group, we were able to estimate mass ratios for these binaries. Combining the present results with a previous study of other single-line binaries from our team, we present a pseudo mass-to-luminosity relationship based on 23 systems (46 stars) in the mass range 0.6 ≤ M ⊙ ≤ 2.5. We find a reasonable correspondence with a fiducial mass-to-luminosity relationship. We conclude that our methodology does allow us to derive tentative mass ratios for these types of binaries.

The ‘small’ asteroid population: a spectroscopic survey

ABSTRACT The study of near-Earth objects (NEOs) allow us to obtain information on the Solar system smallest bodies due to their closeness to Earth. In this work, we present the results of visible spectroscopic observations of 43 small and newly discovered NEOs, obtained during eighteen observing runs between October 2020 and December 2021, using the Goodman High Throughput Spectrograph at the 4.1-m Southern Astrophysical Research telescope (Cerro Pachón, Chile). We found a taxonomic distribution dominated by S-type asteroids but with an overabundance of A- and D-types. This result is in agreement with recent works on NEOs’ characterization and has implications for possible differences in the taxonomic distribution of ‘large’ and ‘small’ objects and emphasizes the idea of a non-homogeneous NEO population.

Speckle Interferometry at SOAR in 2022

Results of the speckle-interferometry observations at the 4.1 m SOuthern Astrophysical Research Telescope obtained during 2022 are presented: 2508 measurements of 1925 resolved pairs or subsystems and 785 nonresolutions of 611 targets; 26 pairs are resolved here for the first time. This work continues our long-term effort to monitor orbital motion in close binaries and hierarchical systems. A large number of orbits have been updated using these measurements.

Benefits of Intelligent Fuzzy Controllers in Comparison to Classical Methods for Adaptive Optics

Adaptive Optics (AO) systems have been developed throughout recent decades as a strategy to compensate for the effects of atmospheric turbulence, primarily caused by poor astronomical seeing. These systems reduce the wavefront distortions using deformable mirrors. Several AO simulation tools have been developed, such as the Object-Oriented, MATLAB, and Adaptive Optics Toolbox (OOMAO), to assist in the project of AO. However, the main AO simulators focus on AO models, not prioritizing the different control techniques. Moreover, the commonly applied control strategies in ground-based telescopes are based on Integral (I) or Proportional-Integral (PI) controllers. This work proposes the integration of OOMAO models to Simulink to support the development of advanced controllers and compares traditional controllers with intelligent systems based on fuzzy logic. The controllers were compared in three scenarios of different turbulence and atmosphere conditions. The simulations were performed using the characteristics/parameters of the Southern Astrophysical Research (SOAR) telescope and assessed with the Full Width at Half Maximum (FWHM), Half Light Radius (HLR), and Strehl ratio metrics to compare the performance of the controllers. The results demonstrate that adaptive optics can be satisfactorily simulated in OOMAO adapted to Simulink and thus further increase the number of control strategies available to OOMAO. The comparative results between the MATLAB script and the Simulink blocks designed showed a maximum relative error of 3% in the Strehl ratio and 1.59% in the FWHM measurement. In the assessment of the control algorithms, the fuzzy PI controller reported a 25% increase in the FWHM metrics in the critical scenario when compared with open-loop metrics. Furthermore, the fuzzy PI controller outperformed the results when compared with the I and PI controllers. The findings underscore the constraints of conventional control methods, whereas the implementation of fuzzy-based controllers showcases the promise of intelligent approaches in enhancing control performance under challenging atmospheric conditions.

Detection of TiO and VO in the Atmosphere of WASP-121b and Evidence For its Temporal Variation

We report the transit observations of the ultra-hot Jupiter WASP-121b using the Goodman High Throughput Spectrograph at the 4 m ground-based Southern Astrophysical Research Telescope, covering the wavelength range 502–900 nm. By dividing the target and reference star into 19 spectroscopic passbands and applying differential spectrophotometry, we derive spectroscopic transit light curves and fit them using a Gaussian process framework to determine transit depths for every passband. The obtained optical transmission spectrum shows a steep increased slope toward the blue wavelength, which seems to be too steep to be accounted for by Rayleigh scattering alone. We note that the transmission spectrum from this work and other works differ obviously from each other, which was pointed out previously by Wilson et al. as evidence for temporal atmospheric variation. We perform a free chemistry retrieval analysis on the optical transmission spectra from this work and the literature HST/WFC3 NIR spectrum. We determine TiO, VO and H2O with abundances of dex, dex and dex, respectively. We compare the abundances of all three of these molecules derived from this work and previous works, and find that they are not consistent with each other, indicating the chemical compositions of the terminator region may change over long timescales. Future multi-epoch and high-precision transit observations are required to further confirm this phenomenon. We note that when combining the transmission spectra in the optical and in NIR in retrieval analysis, the abundances of V and VO, the NIR-to-optical offset and the cloud deck pressure may be coupled with each other.

Discovery of a substellar companion in the TESS light curve of the δ Scuti/γ Doradus hybrid pulsator HD 31221

Context. Close-in, sub-stellar companions to δ Scuti type stars present a highly suitable testbed for examining how planetary-mass objects can influence stellar pulsations. Aims. We aim to constrain the mass of HD 31221 b, probe its atmosphere, and demonstrate how it affects the pulsational pattern of its host, HD 31221. Methods. We made use of the available data from the short-cadence Transiting Exoplanet Survey Satellite (TESS). We modeled the nine observed transits and the out-of-phase variations, including Doppler beaming, ellipsoidal variations, and the reflection effect. We also incorporated ground-based photometry from the MuSCAT2 imager installed at the 1.52 m Telescopio Carlos Sanchez in the Teide Observatory, Spain, as well as speckle interferometry from the Southern Astrophysical Research telescope. Results. We found HD 31221 b to have an orbital period of 4.66631 ± 0.00011 days, with a radius of 1.32 ± 0.14 RJ and a mass of 11.5 ± 10.3 MJ (from the ellipsoidal effect), making it consistent with either a brown dwarf or a giant planet. As HD 31221 is a rapid rotator (v sin I⋆ = 175.31 ± 1.74 km s−1), we deduced the spin-orbit misalignment to be λ = −121.6 ± 14.4° and I⋆ = 55.9 ± 11.3°. The phase curve is dominated by the reflection effect, with a geometric albedo of 1.58 ± 0.50. We also found evidence that HD 31221 is a δ Scuti/γ Doradus hybrid pulsator. There are three cases for which the 3rd, 85th, and 221st orbital harmonics almost exactly coincide with peaks in the Fourier spectrum of the star, hinting at tidally perturbed stellar oscillations. Conclusions. HD 31221 b is the third substellar object that is found to be disrupting the pulsations of its host, following HAT-P-2 and WASP-33. Additional photometric observations by CHEOPS and/or PLATO can be used to further constrain its mass and provide a more in-depth analysis of its atmosphere.

Validation of TOI-1221 b: A Warm Sub-Neptune Exhibiting Transit Timing Variations around a Sun-like Star

We present a validation of a long-period ( days) transiting sub-Neptune planet, TOI-1221 b (TIC 349095149.01), around a Sun-like (m V = 10.5) star. This is one of the few known exoplanets with a period >50 days, and belongs to the even smaller subset of which have bright enough hosts for detailed spectroscopic follow-up. We combine Transiting Exoplanet Survey Satellite light curves and ground-based time-series photometry from the Perth Exoplanet Survey Telescope (0.3 m) and Las Cumbres Observatory global telescope network (1.0 m) to analyze the transit signals and rule out nearby stars as potential false-positive sources. High-contrast imaging from the Southern Astrophysical Research Telescope and Gemini/Zorro rule out nearby stellar contaminants. Reconnaissance spectroscopy from CHIRON sets a planetary scale upper mass limit on the transiting object (1.1 and 3.5 M Jup at 1σ and 3σ, respectively) and shows no sign of a spectroscopic binary companion. We determine a planetary radius of , placing it in the sub-Neptune regime. With a stellar insolation of , we calculate a moderate equilibrium temperature of T eq = 440 K, assuming no albedo and perfect heat redistribution. We find a false-positive probability from the TRICERATOPS tool of FPP = 0.0014 ± 0.0003 as well as other qualitative and quantitative evidence to support the statistical validation of TOI-1221 b. We find significant evidence (>5σ) of oscillatory transit timing variations, likely indicative of an additional nontransiting planet.

Exploring Thousands of Nearby Hierarchical Systems with Gaia and Speckle Interferometry

There should be about 10,000 stellar hierarchical systems within 100 pc with primary stars more massive than 0.5 M ⊙, and a similar amount of less-massive hierarchies. A list of 8000 candidate multiples is derived from wide binaries found in the Gaia Catalog of Nearby Stars where one or both components have excessive astrometric noise or other indicators of inner subsystems. A subset of 1243 southern candidates were observed with high angular resolution at the 4.1 m Southern Astrophysical Research Telescope, and 503 new pairs with separations from 0.″03 to 1″ were resolved. These data allow estimation of the inner mass ratios and periods, and help to quantify the ability of Gaia to detect close pairs. Another 621 hierarchies with known inner periods come from the Gaia catalog of astrometric and spectroscopic orbits. These two nonoverlapping groups, combined with existing ground-based data, bring the total number of known nearby hierarchies to 2754, reaching a completeness of ∼22% for stars above 0.5 M ⊙. Distributions of their periods and mass ratios are briefly discussed, and the prospects of further observations are outlined.

Tentative detection of titanium oxide in the atmosphere of WASP-69 b with a 4m ground-based telescope

ABSTRACT Transiting planets provide unique opportunities for the atmospheric characterization of exoplanets as they can reveal composition and the temperature structures at the day–night terminator regions in planetary atmospheres, and help understand the atmospheric process and formation environments of exoplanets. Here, we present the optical transmission spectroscopic study of an inflated Saturn-mass planet WASP-69 b, obtained by the 4m ground-based telescope Southern Astrophysical Research Telescope (SOAR). We obtain spectroscopic transit light curves in 20 passbands from 502 to 890 nm, and fit them using Gaussian processes and an analytical transit model to obtain independent transit depths for each. The derived transmission spectrum of WASP-69 b shows a slope with absorption depth increasing towards blue wavelengths, indicating a Rayleigh scattering in the atmosphere consistent with previous works. The retrieval analysis yields a tentative detection of TiO absorption feature in the transmission spectrum. We present the first results from the SOAR telescope to characterize exoplanetary atmospheres proving its capability and precision for hot Jupiters around bright stars in an area dominated by results from large ground-based telescopes or space telescopes.

Optimal Observational Scheduling Framework for Binary and Multiple Stellar Systems* *Based in part on observations obtained at the international Gemini Observatory, a program of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini Observatory partnership: the National Science Foundation (United

The optimal instant of observation of astrophysical phenomena for objects that vary on human timescales is an important problem, as it bears on the cost-effective use of usually scarce observational facilities. In this paper, we address this problem in the case of tight visual binary systems through a Bayesian framework based on the maximum entropy sampling principle. Our proposed information-driven methodology exploits the periodic structure of binary systems to provide a computationally efficient estimation of the probability distribution of the optimal observation time. We show the optimality of the proposed sampling methodology in the Bayes sense and its effectiveness through direct numerical experiments. We successfully apply our scheme to the study of two visual-spectroscopic binaries and one purely astrometric triple hierarchical system. We note that our methodology can be applied to any time-evolving phenomena, a particularly interesting application in the era of dedicated surveys, where a definition of the cadence of observations can have a crucial impact on achieving the science goals.

Gaia white dwarfs within 40 pc – III. Spectroscopic observations of new candidates in the Southern hemisphere

Abstract We present a spectroscopic survey of 248 white dwarf candidates within 40 pc of the Sun; of these 244 are in the Southern hemisphere. Observations were performed mostly with the Very Large Telescope (X-Shooter) and Southern Astrophysical Research Telescope. Almost all candidates were selected from Gaia Data Release 3 (DR3). We find a total of 246 confirmed white dwarfs, 209 of which had no previously published spectra, and two main-sequence star contaminants. Of these, 100 white dwarfs display hydrogen Balmer lines, 69 have featureless spectra, and two show only neutral helium lines. Additionally, 14 white dwarfs display traces of carbon, while 37 have traces of other elements that are heavier than helium. We observe 35 magnetic white dwarfs through the detection of Zeeman splitting of their hydrogen Balmer or metal spectral lines. High spectroscopic completeness (&amp;gt; 97 per cent) has now been reached, such that we have 1058 confirmed Gaia DR3 white dwarfs out of 1083 candidates within 40 pc of the Sun at all declinations.

The strongest cool core in REXCESS: Missing X-ray cavities in RXC J2014.8–2430

We present a broad, multi-wavelength study of RXC J2014.8−2430, the most extreme cool-core cluster in the Representative XMM-Newton Cluster Structure Survey (REXCESS), using Chandra X-ray, Southern Astrophysical Research (SOAR) Telescope spectroscopic and narrow-band imaging, Atacama Large Millimeter/submillimeter Array (ALMA), Very Large Array, and Giant Metrewave Radio Telescope observations. While feedback from an active galactic nucleus (AGN) is thought to be the dominant mechanism by which a cooling flow is suppressed, the Chandra imaging observations surprisingly do not reveal the bi-lateral X-ray cavities one might expect to see in the intracluster medium (ICM) of an extreme cool core hosting a powerful radio source, though cavities commonly appear in many similar sources. We discuss the limits on the properties of putative radio bubbles associated with any undetected X-ray cavities. We place upper limits on any significant X-ray AGN in the brightest cluster galaxy (BCG) and show that the X-ray peak is offset from the central radio source, which exhibits a steep low-frequency radio spectrum indicative of electron ageing. The imaging and spectroscopy provided by SOAR reveal an extended, luminous optical emission-line source. From our narrow-band Hα imaging of the BCG, the central Hα peak is coincident with the radio observations, yet offset from the X-ray peak, consistent with sloshing found previously in this cluster. ALMA observations of the CO(1−0) emission reveal a large reservoir of molecular gas that traces the extended Hα emission in the direction of the cool core. We conclude either that the radio source and its cavities in the X-ray gas are nearly aligned along the line of sight, or that ram pressure induced by sloshing has significantly displaced the cool molecular gas feeding it, perhaps preempting the AGN feedback cycle. We argue that the sloshing near the core is likely subsonic, as expected, given the co-location of the Hα, CO(1−0), radio continuum, and stellar emission peaks and their proximity to the X-ray peak. Further, the X-ray emission from the core is strongly concentrated, as is the distribution of metals, indicating the cool core remains largely intact. Deeper Chandra observations will be crucial for definitively establishing the presence or lack of X-ray cavities, while X-ray micro-calorimetric observations from Athena could establish if the motion of the cold and warm gas is dominated by large-scale motions of the surrounding ICM.

Near-infrared Accretion Signatures from the Circumbinary Planetary-mass Companion Delorme 1 (AB)b* * Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia e Inovações (MCTI/LNA) do Brasil, the US National Science Foundation's NOIRLab, the University of North Carolina at Chapel Hill (UNC), and Michigan State University (MSU).

Accretion signatures from bound brown dwarf and protoplanetary companions provide evidence for ongoing planet formation, and accreting substellar objects have enabled new avenues to study the astrophysical mechanisms controlling the formation and accretion processes. Delorme 1 (AB)b, a ∼30–45 Myr circumbinary planetary-mass companion, was recently discovered to exhibit strong Hα emission. This suggests ongoing accretion from a circumplanetary disk, somewhat surprising given canonical gas disk dispersal timescales of 5–10 Myr. Here, we present the first NIR detection of accretion from the companion in Paβ, Paγ, and Brγ emission lines from SOAR/TripleSpec 4.1, confirming and further informing its accreting nature. The companion shows strong line emission, with L line ≈ 1–6 × 10−8 L ⊙ across lines and epochs, while the binary host system shows no NIR hydrogen line emission (L line < 0.32–11 × 10−7 L ⊙). Observed NIR hydrogen line ratios are more consistent with a planetary accretion shock than with local line excitation models commonly used to interpret stellar magnetospheric accretion. Using planetary accretion shock models, we derive mass accretion rate estimates of –4 × 10−8 M J yr−1, somewhat higher than expected under the standard star formation paradigm. Delorme 1 (AB)b’s high accretion rate is perhaps more consistent with formation via disk fragmentation. Delorme 1 (AB)b is the first protoplanet candidate with clear (signal-to-noise ratio ∼5) NIR hydrogen line emission.

Speckle Interferometry at SOAR in 2021

The speckle interferometry program at the the 4.1 m Southern Astrophysical Research Telescope (SOAR), which started in 2008, now has accumulated over 30,300 individual observations of 12,700 distinct targets. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and low-mass dwarfs in the solar neighborhood. The results from 2021 are published here, totaling 2623 measurements of 2123 resolved pairs and nonresolutions of 763 targets. The median measured separation is 0.″21, and 75 pairs were closer than 30 mas. The calibration of scale and orientation is based on the observations of 103 wide pairs with well-modeled motion. These calibrators are compared to the latest Gaia data release, and minor (0.5%) systematic errors were rectified, resulting in accurate relative positions with typical errors on the order of 1 mas. Using these new measurements, orbits of 282 binaries are determined here (54 first determinations and 228 corrections). We resolved for the first time 50 new pairs, including subsystems in known binaries. A list of 94 likely spurious pairs unresolved at SOAR (mostly close Hipparcos binaries) is also given.

SOAR/Goodman Spectroscopic Assessment of Candidate Counterparts of the LIGO/Virgo Event GW190814* *Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, Inovações e Comunicações (MCTIC) do Brasil, the US National Science Foundations National Optical–Infrared Astronomy Research Laboratory (NOIRLab), the University of North Carolina at Chapel Hill (UNC), and

On 2019 August 14 at 21:10:39 UTC, the LIGO/Virgo Collaboration (LVC) detected a possible neutron star–black hole merger (NSBH), the first ever identified. An extensive search for an optical counterpart of this event, designated GW190814, was undertaken using the Dark Energy Camera on the 4 m Victor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory. Target of Opportunity interrupts were issued on eight separate nights to observe 11 candidates using the 4.1 m Southern Astrophysical Research (SOAR) telescope’s Goodman High Throughput Spectrograph in order to assess whether any of these transients was likely to be an optical counterpart of the possible NSBH merger. Here, we describe the process of observing with SOAR, the analysis of our spectra, our spectroscopic typing methodology, and our resultant conclusion that none of the candidates corresponded to the gravitational wave merger event but were all instead other transients. Finally, we describe the lessons learned from this effort. Application of these lessons will be critical for a successful community spectroscopic follow-up program for LVC observing run 4 (O4) and beyond.

The Solar Neighborhood. XLIX. New Discoveries and Orbits of M-dwarf Multiples with Speckle Interferometry at SOAR

Abstract We present the first results of a multiyear program to map the orbits of M-dwarf multiples within 25 pc. The observations were conducted primarily during 2019–2020 using speckle interferometry at the Southern Astrophysical Research Telescope in Chile, using the High-Resolution Camera mounted on the adaptive optics module (HRCam+SAM). The sample of nearby M dwarfs is drawn from three sources: multiples from the RECONS long-term astrometric monitoring program at the SMARTS 0.9 m; known multiples, for which these new observations will enable or improve orbit fits; and candidate multiples flagged by their astrometric fits in Gaia Data Release 2 (DR2). We surveyed 333 of our 338 M dwarfs via 830 speckle observations, detecting companions for 63% of the stars. Most notably, this includes new companions for 76% of the subset selected from Gaia DR2. In all, we report the first direct detections of 97 new stellar companions to the observed M dwarfs. Here we present the properties of those detections, the limits of each nondetection, and five orbits with periods 0.67–29 yr already observed as part of this program. Companions detected have projected separations of 0.″024–2.″0 (0.25–66 au) from their primaries and have ΔI ≲ 5.0 mag. This multiyear campaign will ultimately map complete orbits for nearby M dwarfs with periods up to 3 yr, and provide key epochs to stretch orbital determinations for binaries to 30 yr.