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<jats:title>Abstract</jats:title> <jats:p>We present archival Giant Metrewave Radio Telescope (GMRT) observations of two exoplanetary systems, <jats:italic>τ</jats:italic> Boötis, and 55 Cancri, at 610 MHz and 150 MHz, respectively. Theoretical models predict these systems to have some of the highest expected flux densities at radio wavelengths. Both <jats:italic>τ</jats:italic> Boötis and 55 Cancri have been previously observed at low frequency (∼30 MHz) with Low-Frequency Array. <jats:italic>τ</jats:italic> Boötis shows tentative signatures of circularly polarized emission at 30 MHz, while no emission was detected from 55 Cancri. We do not detect radio emission from both the systems, but the GMRT observations set 3<jats:italic>σ</jats:italic> upper limits of 0.6 mJy at 610 MHz for <jats:italic>τ</jats:italic> Boötis and 4.6 mJy at 150 MHz for 55 Cancri. The sensitivity achieved at 610 MHz in these observations is comparable to some of the deepest images of an exoplanet field.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Suggestions are offered as to which globular clusters of the Milky Way presented the most favorable conditions for development of an extraterrestrial civilization. Of these NGC 6553 is emphasized.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the possible discovery of a new stellar system (YMCA-1), identified during a search for small scale overdensities in the photometric data of the YMCA survey. The object’s projected position lies on the periphery of the Large Magellanic Cloud about 13° apart from its center. The most likely interpretation of its color–magnitude diagram, as well as of its integrated properties, is that YMCA-1 may be an old and remote star cluster of the Milky Way at a distance of 100 kpc from the Galactic center. If this scenario could be confirmed, then the cluster would be significantly fainter and more compact than most of the known star clusters residing in the extreme outskirts of the Galactic halo, but quite similar to Laevens 3. However, much deeper photometry is needed to firmly establish the actual nature of the cluster, and the distance to the system.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report high-cadence photometry of the ultra-fast (<jats:italic>t</jats:italic> <jats:sub>2</jats:sub> ∼ 1.2 days) nova V1674 Her during its rise to maximum light (<jats:italic>V</jats:italic> ∼ 6.3) and the beginning of its subsequent decline. These observations from Evryscope and the Mount Laguna Observatory All-Sky Camera reveal a plateau in the pre-maximum light curve at <jats:italic>g</jats:italic> ∼ 14 (∼8 mag below peak) that lasted for at least three hours. Similar features (so-called pre-maximum halts) have been observed in some novae near maximum light, but to our knowledge the detection of a plateau in the light curve ∼8 mag below peak is unprecedented.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The recent discovery of a hundred-kilometer-scale comet, C/2014 UN271 (Bernardinelli-Bernstein), has provoked interest in the activity displayed by such a large body inbound from the Oort cloud. We examine the serendipitous observation of UN271 in long-cadence imaging by the TESS satellite in 2018 and 2020, while Bernardinelli-Bernstein was at 23.8 and 21.3 au, for any notable periodicity. Bernardinelli-Bernstein does not display detectable rotational variability above the noise level in these data.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A planet’s orbit encodes information about its formation and history. However, exoplanets detected via direct-imaging are often only observed over a small fraction of their periods. Several problems arise from such unconstraining data, like slow convergence of standard orbit-fitting algorithms and significant biases in the estimation of orbital parameters. One possible way of overcoming some of these problems is performing orbit-fits in orbital bases distinct from the usual Keplerian elements. We explore this approach by fitting orbits in Cartesian coordinates, that is, estimating the position and velocity vectors for a planet at a given epoch. We saw a significant improvement in the MCMC convergence time compared to the Keplerian elements, and different posterior shapes were observed with different priors. In particular, setting Gaussian priors in the line-of-sight components (<jats:italic>z</jats:italic> and <jats:inline-formula> <jats:tex-math> <?CDATA $\dot{z}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>˙</mml:mo> </mml:mrow> </mml:mover> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="rnaasac151dieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) produced posteriors more similar to the ones obtained via the Keplerian basis compared to uniform priors on them.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The comparison of four consecutive high signal-to-noise FEROS spectra of Maia, the fourth brightest member of the Pleiades open cluster, taken over 10 minutes, reveals no real line variations. The analysis of four consecutive I NARVAL profiles of Maia taken over 18 minutes does not show variations either. In particular, the five lines of He <jats:sc>i</jats:sc> at 4471.48 Å are constant over this timescale in both sets of data. The He <jats:sc>i</jats:sc> line at 3926.54 Å is very broad and diffuse compared to other photospheric lines of Maia.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Unlike the Sun, most observed stars are part of a multiple star system, but the formation of such systems is still not well understood. To study this problem, we utilize a run from the STARFORGE simulation suite that simulates the evolution of star-forming Giant Molecular Clouds (GMCs). The run starts with a GMC of an initial mass of 2 × 10<jats:sup>4</jats:sup>  <jats:italic>M</jats:italic> <jats:sub>⊙</jats:sub> and takes gravity, magneto-hydrodynamics and non-isothermal thermodynamics into account. The simulation also includes stellar feedback in the forms of radiation and protostellar jets, where the radiation field is explicitly evolved. In this note, we discuss the orbital period, semimajor axis, multiplicity fraction, and multiplicity frequency distributions, and compare these with observations. We find good agreement with the observed multiplicity fractions but also find a deficit of mass ratios close to unity and close companions, which we attribute to the lack of resolved disks in our simulation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Faraday rotation (FR) of MESSENGER spacecraft <jats:italic>X</jats:italic>-band transcoronal radio transmissions were studied to evaluate the mid-coronal magnetic field strength, with the line-of-sight closest solar approach at heliocentric altitudes ranging 1.647–1.817 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub>. A Community Coordinated Modeling Center (CCMC) CORHEL-MAS 3D coronal field map revealed this region to contain closed magnetic fields. By FR analysis we found a field strength of 118,000 nT at <jats:italic>r</jats:italic> = 1.647 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub>, with fall-off to 40,000 nT by <jats:italic>r</jats:italic> = 1.817 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub>. These values straddle estimates provided by the CCMC model. The mean value of 79,000 nT at <jats:italic>r</jats:italic> = 1.732 <jats:italic>R</jats:italic> <jats:sub>⊙</jats:sub> is comparable to the value provided by an established empirical model for average coronal magnetic field strength. FR can be used to evaluate middle coronal magnetic fields, but improved methods to constrain concurrent electron column density will be needed to produce the most accurate results.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We report the non-detection of dispersed bursts between 4 and 8 GHz from 2.5 hr of observations of FRB 20200120E at 6 GHz using the Robert C. Byrd Green Bank Telescope. Our fluence limits are several times lower than the average burst fluences reported at 600 and 1400 MHz. We conclude that these non-detections are either due to high-frequency bursts being weaker and/or scintillation-induced modulated. It is also likely that our observations were non-concurrent with any activity window of FRB 20200120E.</jats:p>