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  • The TANDEM Project as a Pilot Case for Wide-field Telescope Arrays
    We give here an account of the Telescope Array eNabling DEbris Monitoring (TANDEM) project, an innovative concept aimed at flanking, on a shared piggyback mount, the main G. D. Cassini 152 cm f/8 telescope at the INAF-OAS observing premises in Loiano, Italy. The system is especially intended for space situational awareness activities related to the study of asteroids and comets and on the astrodynamical characterization of circumterrestrial space debris and artificial satellites. TANDEM consists of a combination of four customized and independently steerable 35 cm f/3 Newtonian telescopes, each equipped with a Moravian C4-16000 camera, observing through the BVRcIc filters of the Johnson–Cousins system. The camera carries on board a GSense 4040 (4096 × 4096 pixels) monochrome CMOS detector with an electronic shutter and a 9 μm pixel size. A corrected field of view of 2° × 2° is offered by each telescope, though quite special pointing capabilities and observing modes are available for the telescope array, such as to cover up to 16 deg2 across sparse celestial fields, each up to 20° in separation. While especially conceived for observing activities in the framework of the European Consortium for Space Surveillance and Tracking, TANDEM may also find additional applications in a more direct astronomical context, as we briefly outline along this review.

  • BARBIE. Bayesian Analysis for Remote Biosignature Identification on exoEarths. III. Introducing the KEN
    We deploy a newly generated set of geometric albedo spectral grids to examine the detectability of methane (CH4) in the reflected-light spectrum of an Earth-like exoplanet at visible and near-infrared (NIR) wavelengths with a future exoplanet imaging mission. By quantifying the detectability as a function of signal-to-noise ratio (SNR) and molecular abundance, we can constrain the best methods of detection with the high-contrast space-based coronagraphy slated for the next-generation telescopes such as the Habitable Worlds Observatory. We used 25 bandpasses between 0.8 and 1.5 μm. The abundances range from a modern-Earth level to an Archean-Earth level, driven by abundances found in available literature. We constrain the optimal 20%, 30%, and 40% bandpasses based on the effective SNR of the data, and investigate the impact of spectral confusion between CH4 and H2O on the detectability of each one. We find that a modern-Earth level of CH4 is not detectable, while an Archean-Earth level of CH4 would be detectable at all SNRs and bandpass widths. Crucially, we find that CH4 detectability is inversely correlated with H2O abundance, with the required SNR increasing as H2O abundance increases, while H2O detectability depends on CH4 abundance and the selected observational wavelength, implying that any science requirements for the characterization of Earth-like planet atmospheres in the visible–NIR should consider the abundances of both species in tandem.

  • DECaPS and SMA Discovery of a Highly Inclined Class I Young Stellar Object with an Outflow: IRAS 08235–4316
    We present images of IRAS 08235–4316 with the Dark Energy Camera Plane Survey (DECaPS; spanning 0.398–1.034 μm, at ∼1″ resolution) and the Submillimeter Array (SMA; at 1.38 mm (217 GHz) and ∼1 9 × 1 2 resolution), a young stellar object (YSO) located in the Vela constellation near to the Puppis boundary, detected in a systematic search for new large/extended emission sources. The DECaPS data show an asymmetric bipolar morphology with a large angular extent of ∼7 1 separated by a dark lane, characteristic of highly inclined protoplanetary disks and less-evolved YSOs with outflows. The SMA data show an extended continuum structure along the optical dark lane with a smaller angular extent of ∼4 6. The detected 12CO J = 2–1 emission tentatively shows a velocity gradient along the position angle of the dark lane/millimeter continuum, which may trace rotating gas. Additional 12CO emission is present, which could trace infalling/outflowing gas and/or a nearby gas cloud. We estimate a distance to IRAS 08235–4316 of at least ∼191 pc. Supported by additional spectral energy distribution modelling, we infer IRAS 08235–4316 to be a newly discovered Class I YSO with an outflow, host to an embedded protoplanetary disk, with a large millimeter radius of ∼440 au and dust mass ≳ 11 M⊕.

  • Resolving the Young 2 Cygni Runaway Star into a Binary Using iLocater
    Precision radial velocity spectrographs that use adaptive optics (AO) show promise to advance telescope observing capabilities beyond those of seeing-limited designs. We are building a spectrograph for the Large Binocular Telescope (LBT) named iLocater that uses AO to inject starlight directly into single mode fibers. iLocater's first acquisition camera system (the SX camera), which receives light from one of the 8.4 m diameter primary mirrors of the LBT, was initially installed in summer 2019 and has since been used for several commissioning runs. We present results from first-light observations that include on-sky measurements as part of commissioning activities. Imaging measurements of the bright B3IV star 2 Cygni (V = 4.98) resulted in the direct detection of a candidate companion star at an angular separation of only θ = 70 mas. Follow-up AO measurements using Keck/NIRC2 recover the candidate companion in multiple filters. An R ≈ 1500 miniature spectrograph recently installed at the LBT named Lili provides spatially resolved spectra of each binary component, indicating similar spectral types and strengthening the case for companionship. Studying the multiplicity of young runaway star systems like 2 Cygni (36.6 ± 0.5 Myr) can help to understand formation mechanisms for stars that exhibit anomalous velocities through the Galaxy. This on-sky demonstration illustrates the spatial resolution of the iLocater SX acquisition camera working in tandem with the LBT AO system; it further derisks a number of technical hurdles involved in combining AO with Doppler spectroscopy.

  • Characterizing Superflares in HR 1099 Using Temporal and Spectral Analysis of XMM-Newton Observations
    In the present paper, we analyze three energetic X-ray flares from the active RS CVn binary HR 1099 using data obtained from XMM-Newton. The flare duration ranges from 2.8 to 4.1 hr, with e-folding rise and decay times in the range of 27–38 minutes and 1.3–2.4 hr, respectively, indicating rapid rise and slower decay phases. The flare frequency for HR 1099 is one flare per rotation period. Time-resolved spectroscopy reveals peak flare temperatures of 39.44, 35.96, and 32.48 MK, emission measures of 7 × 1053–8 × 1054 cm−3, global abundances of 0.250, 0.299, and 0.362 Z⊙, and peak X-ray luminosities of 1031.21−32.29 erg s−1. The quiescent state is modeled with a three-temperature plasma maintained at 3.02, 6.96, and 12.53 MK. Elemental abundances during quiescent and flaring states exhibit the inverse-first ionization potential (i-FIP) effect. We have conducted a comparative analysis of coronal abundances with previous studies and found evidence supporting the i-FIP effect. The derived flare semi-loop lengths of 6–8.9 × 1010 cm were found to be comparable to the other flares detected on HR 1099; however, they are significantly larger than typical solar flare loops. The estimated flare energies, ranging from 1035.83−37.03 erg, classify these flares as super-flares. The magnetic field strengths of the loops are found to be in the range of 350–450 G. We diagnose the physical conditions of the flaring corona in HR 1099 through the observations of superflares and provide inference on the plasma processes.