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The JWST Discovery of the Triply Imaged Type Ia "Supernova H0pe" and Observations of the Galaxy Cluster PLCK G165.7+67.0
Get PDFA Type Ia supernova (SN) at z = 1.78 was discovered in James Webb Space Telescope Near Infrared Camera imaging of the galaxy cluster PLCK G165.7+67.0 (G165; z = 0.35). The SN is situated 1.5–2 kpc from the host-galaxy nucleus and appears in three different locations as a result of gravitational lensing by G165. These data can yield a value for Hubble's constant using time delays from this multiply imaged SN Ia that we call "SN H0pe." Over the cluster, we identified 21 image multiplicities, confirmed five of them using the Near-Infrared Spectrograph, and constructed a new lens model that gives a total mass within 600 kpc of (2.6 ± 0.3) × 1014 M ⊙. The photometry uncovered a galaxy overdensity coincident with the SN host galaxy. NIRSpec confirmed six member galaxies, four of which surround the SN host galaxy with relative velocity ≲900 km s‑1 and projected physical extent ≲33 kpc. This compact galaxy group is dominated by the SN host galaxy, which has a stellar mass of (5.0 ± 0.1) × 1011 M ⊙. The group members have specific star formation rates of 2–260 Gyr‑1 derived from the Hα-line fluxes corrected for stellar absorption, dust extinction, and slit losses. Another group centered on a strongly lensed dusty star-forming galaxy is at z = 2.24. The total (unobscured and obscured) SFR of this second galaxy group is estimated to be (≳ 100 M ⊙ yr‑1), which translates to a supernova rate of ∼1 SNe yr‑1, suggesting that regular monitoring of this cluster may yield additional SNe...
Highly luminous supernovae associated with gamma-ray bursts II. The luminous blue bump in the afterglow of GRB 140506A
Get PDFThe supernovae (SNe) associated with gamma-ray bursts (GRBs) are generally
seen as a homogenous population, but at least one exception exists, both in
terms of luminosity as well as Spectral Energy Distribution (SED). However,
this event, SN 2011kl, was associated with an ultra-long GRB 111209A. Do such
outliers also exist for more typical GRBs? Within the context of a systematic
analysis of photometric signatures of GRB-associated SNe, we found an anomalous
bump in the late-time transient following GRB 140506A. We hereby aim to show
this bump is significantly more luminous and blue than usual SNe following
GRBs. We compile all available data from the literature, and add a full
analysis of the Swift UVOT data, which allows us to trace the light curve from
the first minutes all the way to the host galaxy, as well as construct a broad
SED of the afterglow that extends the previous SED analysis based on
ground-based spectroscopy. We find robust evidence for a late-time bump/plateau
following the afterglow which shows evidence for a strong colour change, with
the spectral slope becoming flatter in the blue region of the spectrum. This
bump can be interpreted as a luminous SN bump which is spectrally dissimilar to
typical GRB-SNe. Correcting it for the large line-of-sight extinction results
in extreme values which make the SN associated with GRB 140506A the most
luminous detected so far. Even so, it would be in agreement with a
luminosity-duration relation of GRB-SNe. While not supported by spectroscopic
evidence, it is likely the blue bump following GRB 140506A is the signature of
a SN which is spectrally dissimilar to classical GRB-SNe and more similar to SN
2011kl -- while being associated with an average GRB, indicating the GRB-SN
population is more diverse than thought so far, and can reach luminosities
comparable to those of superluminous SNe
Radio jets in NGC 1068 with e-MERLIN and VLA: structure and morphology
Get PDFWe present new high-sensitivity e-MERLIN and Very Large Array (VLA) radio images of the prototypical Seyfert 2 galaxy NGC 1068 at 5, 10, and 21 GHz. We image the radio jet, from the compact components north-east (NE), C, S1, and S2 to the faint double-lobed jet structure of the NE and south-west (SW) jet lobes. We map the jet between 15 kλ and 3300 kλ spatial scales by combining enhanced-Multi Element Radio Linked Interferometer Network (e-MERLIN) and VLA data for the first time. Components NE, C, and S2 have steep spectra indicative of optically thin non-Thermal emission domination between 5 and 21 GHz. Component S1, which is where the active galactic nucleus resides, has a flat radio spectrum. We report a new component, S2a, a part of the southern jet. We compare these new data with the MERLIN and VLA data observed in 1983, 1992, and 1995 and report a flux decrease by a factor of 2 in component C, suggesting variability of this jet component. With the high angular resolution e-MERLIN maps, we detect the bow shocks in the NE jet lobe that coincide with the molecular gas outflows observed with ALMA. The NE jet lobe has a jet power of 6.7 × 1042 erg s-1 and is considered to be responsible for driving out the dense molecular gas observed with ALMA around the same region
A new catalog of magnetically active solar-like oscillators
Get PDFWe present a new catalog of stars for which detected solar-like oscillations and magnetic activity measurements from chromospheric spectroscopic observations are both available. Our results were obtained by exploiting NASA TESS mission light curves for active stars observed within the Mount Wilson Observatory HK project and the HK survey of the Hamburg Robotic Telescope TIGRE. We analyzed the light curves for a total of 191 stars by adopting recent techniques based on Bayesian analysis and model comparison to assess the detection of a power excess originating from solar-like oscillations. We characterized the oscillations in a total of 34 targets, for which we provide estimates for the global asteroseismic parameters of νmax (the frequency of maximum oscillation power), δν (the large frequency separation), and for the amplitude of the solar-like oscillation envelope Amax. We provide strong statistical evidence for the detection of solar-like oscillations in 15 stars of our sample, identify six further stars where a detection is likely, and 13 stars for which oscillations cannot be ruled out. The key parameters extracted in this work will be exploited for a detailed stellar modeling of the targets and to calibrate relations that connect the level of the measured magnetic activity to the suppression induced on the global oscillation amplitudes. This opens the possibility of shedding light on the interplay between magnetic fields and oscillations. Because of their relatively high brightness, the targets may also be of interest for future dedicated follow-up observations using both photometry and spectropolarimetry
Eighteen new fast radio bursts in the High Time Resolution Universe survey
Get PDFContext. Current observational evidence reveals that fast radio bursts (FRBs) exhibit bandwidths ranging from a few dozen MHz to several GHz. Traditional FRB searches primarily employ matched filter methods on time series collapsed across the entire observational bandwidth. However, with modern ultrawideband receivers featuring gigahertz-scale observational bandwidths, this approach may overlook a significant number of events. Aims. We investigate the efficacy of sub-banded searches for FRBs, whereby we look for bursts within limited portions of the bandwidth. The aim of these searches is to enhance the significance of FRB detections by mitigating the impact of noise outside the targeted frequency range, thereby improving signal-To-noise ratios. Methods. We conducted a series of Monte Carlo simulations for the 400-MHz bandwidth Parkes 21-cm multi-beam (PMB) receiver system and the Parkes Ultra-Wideband Low (UWL) receiver, simulating bursts down to frequency widths of about 100 MHz. Additionally, we performed a complete reprocessing of the high-latitude segment of the High Time Resolution Universe South survey (HTRU-S) of the Parkes-Murriyang telescope using sub-banded search techniques. Results. Simulations reveal that a sub-banded search can enhance the burst search efficiency by 6742+133% for the PMB system and 1433126+143% for the UWL receiver. Furthermore, the reprocessing of HTRU led to the confident detection of 18 new bursts, nearly tripling the count of FRBs found in this survey. Conclusions. These results underscore the importance of employing sub-banded search methodologies to effectively address the often modest spectral occupancy of these signals
Ariel stellar characterisation II. Chemical abundances of carbon, nitrogen, and oxygen for 181 planet-host FGK dwarf stars
Get PDFOne of the ultimate goals of the ESA Ariel space mission is to shed light on
the formation pathways and evolution of planetary systems in the Solar
neighbourhood. Such an endeavour is only possible by performing a large
chemical survey of not only the planets, but also their host stars, inasmuch as
stellar elemental abundances are the cipher key to decode the planetary
compositional signatures. This work aims at providing homogeneous abundances of
C, N, and O of a sample of 181 stars belonging to the Tier 1 of the Ariel
Mission Candidate Sample. We applied the spectral synthesis and the equivalent
width methods to a variety of atomic and molecular indicators (C I lines at
5052 and 5380.3 A, [O I] forbidden line at 6300.3 A, C_2 bands at 5128 and 5165
A, and CN band at 4215 A) using high-resolution and high S/N spectra collected
with several spectrographs. We provide carbon abundances for 180 stars,
nitrogen abundances for 105 stars, and oxygen abundances for 89 stars. We
analyse the results in the light of the Galactic chemical evolution, and in
terms of the planetary companions properties. Our sample basically follows the
typical trends with metallicity expected for the [C/Fe], [N/Fe], and [O/Fe]
abundance ratios. The fraction between C and O abundances, both yields of
primary production, is consistent with a constant ratio as [O/H] increases,
whereas the abundance of N tends to increase with the increasing of the O
abundance, supporting the theoretical assumption of a secondary production of
nitrogen. The [C/N], [C/O], and [N/O] ratios are also correlated with [Fe/H],
which might introduce biases in the interpretation of the planetary
compositions and formation histories if host stars of different metallicity are
compared. We provide relations that can be used to qualitatively estimate
whether the atmospheric composition of planets is enriched or not with respect
to the host stars
Observation of the Southern Polar cap during MY34-36 with ExoMars-TGO NOMAD LNO
Get PDFMainly designed to study minor atmospheric species in the Martian atmosphere, the Nadir and Occultation for MArs Discovery (NOMAD) instrument suite onboard the 2016 ExoMars Trace Gas Orbiter (TGO) can also be exploited for surface ice detection. In this work, we investigate the nadir observations of the NOMAD infrared channel from the Martian Years 34 to 36 (Mars 2018 to December 2022), especially for CO2 ice detection. Based on Oliva et al. (2022), we present an updated method taking advantage of the 2.7 μm absorption band for surface ice detection by selecting the diffraction orders 190, 169, 168 and 167. We focus the analysis on the Southern polar cap and define its boundaries during its sublimation phase in MY34–36. Globally, seasonal changes seem repeatable for MY34–36. Moreover, we show the potential of the 2.29 μm absorption band for surface CO2 ice identification through the diffraction order 193. We define a pseudo-band depth as a good proxy for CO2 ice detection. Following a semi-qualitative approach, we attempt to reproduce such spectra by using the Planetary Spectrum Generator (PSG) model in order to estimate CO2 ice equivalent grain size. For the selected periods, the estimations are in the order of centimetres, which is in agreement with previous studies using spectral observations of OMEGA, CRISM and TES instruments
CO2 in the atmosphere of Mars depleted in 13C
Get PDFWe present here vertically resolved measurements of the carbon isotopic composition of CO2 in the Martian atmosphere between the surface and 50 km of altitude. The results are based on data taken by the ExoMars Trace Gas Orbiter with the NOMAD instrument and have been aggregated to derive an average vertical profile of 13C/12C. We find no seasonal or spatial trends with variabilities beyond the sensitivity of the measurements. For the analysis, we developed a method that allows us to estimate whether the observed variability of isotopic measurements is beyond their intrinsic accuracy, by exploiting ab-initio spectroscopy and the radiometric noise of the instrument. Applying this method to our data, we find that atmospheric CO2 is depleted in 13C compared to the Earth standard by 30‰ to 45‰, in line with previous ground-based measurements values of the atmosphere and in contrast with the average value obtained by Curiosity at the surface (46 ± 4‰). These differences in isotopic signatures of CO2 as measured across the atmosphere and near-surface pose new questions when inferring the evolution and history of carbon on Mars, and suggest that processes such as a strong atmosphere-surface interactions may be fractionating the carbon reservoirs on the planet
The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation
Get PDFWEAVE, the new wide-field, massively multiplexed spectroscopic survey facility for the William Herschel Telescope, saw first light in late 2022. WEAVE comprises a new 2-deg field-of-view prime-focus corrector system, a nearly 1000-multiplex fibre positioner, 20 individually deployable 'mini' integral field units (IFUs), and a single large IFU. These fibre systems feed a dual-beam spectrograph covering the wavelength range 366-959 nm at R ~ 5000, or two shorter ranges at . After summarizing the design and implementation of WEAVE and its data systems, we present the organization, science drivers, and design of a five- to seven-year programme of eight individual surveys to: (i) study our Galaxy's origins by completing Gaia's phase-space information, providing metallicities to its limiting magnitude for ~3 million stars and detailed abundances for ~1.5 million brighter field and open-cluster stars; (ii) survey ~0.4 million Galactic-plane OBA stars, young stellar objects, and nearby gas to understand the evolution of young stars and their environments; (iii) perform an extensive spectral survey of white dwarfs; (iv) survey ~400 neutral-hydrogen-selected galaxies with the IFUs; (v) study properties and kinematics of stellar populations and ionized gas in z 1 million spectra of LOFAR-selected radio sources; and (viii) trace structures using intergalactic/circumgalactic gas at z > 2. Finally, we describe the WEAVE Operational Rehearsals using the WEAVE Simulator
ANDES, the high-resolution spectrograph for the ELT: project management for the preliminary design phase
No full textThe ESO/ELT ANDES (ArmazoNes high Dispersion Echelle Spectrograph) project successfully completed the system architecture review and is currently finalizing its preliminary design phase. ANDES is the high-resolution spectrograph for the ELT (ESO Extremely Large Telescope) capable of reaching a resolution of R~100,000 simultaneously, in a wavelength range between 0.35-2.4 µm (goals included), characterized by high-precision and extreme calibration accuracy suitable to address a variety of flagship scientific cases across a wide range of astronomical domains. To fulfill the required specifications the proposed design adopts a modular approach where the instrument is split in four individual spectrographs, each fiber-fed, and thermally and vacuum stabilized. A dedicated front-end which hosts a single conjugated adaptive optics module, collects either the light from the telescope or from a calibration unit feeding in turn the individual spectrographs. To master the described complexity the same modularity is reflected also at the project management level: each of the 9 subsystems (counting also the software as a standalone subsystem) is under direct responsibility of different teams coordinated by the ANDES project office. The high distribution and the large community involvement, consisting of 24 institutes from 13 countries, represent certainly a challenge from the project management point of view. In this paper we present the project management approach we envisaged to master successfully all the ANDES project phases from the finalization of the preliminary design up to commissioning on-sky; in particular we will describe in detail the risk management and PA/QA activities we have foreseen to assure appropriate risk mitigation and an overall high-quality standard required for the ANDES project