Multi-band Photometry Research Articles

The First Catalog of Candidate White Dwarf–Main-sequence Binaries in Open Star Clusters: A New Window into Common Envelope Evolution

Close binary systems are the progenitors to both Type Ia supernovae and the compact object mergers that can be detected via gravitational waves. To achieve a binary with a small radial separation, it is believed that the system likely undergoes common envelope (CE) evolution. Despite its importance, CE evolution may be one of the largest uncertainties in binary evolution due to a combination of computational challenges and a lack of observed benchmarks where both the post-CE and pre-CE conditions are known. Identifying post-CE systems in star clusters can partially circumvent this second issue by providing an independent age constraint on the system. For the first time, we conduct a systematic search for white dwarf and main-sequence binary systems in 299 Milky Way open star clusters. Coupling Gaia DR3 photometry and kinematics with multiband photometry from Pan-STARRS1 and the Two Micron All Sky Survey, we apply a machine learning-based approach and find 52 high-probability candidates in 38 open clusters. For a subset of our systems, we present follow-up spectroscopy from the Gemini and Lick Observatories and archival light curves from the Transiting Exoplanet Survey Satellite, Kepler/K2, and the Zwicky Transient Facility. Examples of M dwarfs with hot companions are spectroscopically observed, along with regular system variability. While the kinematics of our candidates are consistent with their host clusters, some systems have spatial positions offset relative to their hosts, potentially indicative of natal kicks. Ultimately, this catalog is a first step to obtaining a set of observational benchmarks to better link post-CE systems to their pre-CE progenitors.

ASTRODEEP-JWST: NIRCam-HST multi-band photometry and redshifts for half a million sources in six extragalactic deep fields

Aims. We present a set of photometric catalogues primarily aimed at providing the community with a comprehensive database for the study of galaxy populations in the high-redshift Universe. The set gathers data from eight JWST NIRCam observational programs, targeting the Abell 2744 (GLASS-JWST, UNCOVER, DDT2756, and GO3990), EGS (CEERS), COSMOS and UDS (PRIMER), and the GOODS North and South (JADES and NGDEEP) deep fields. This dataset covers a total area of ≃0.2 sq. degrees. Methods. We obtained photometric estimates by means of well-established techniques, including tailored improvements designed to enhance the performance on the specific dataset. We also included new measurements from HST archival data, spanning 16 bands from 0.44 to 4.44 µm. Results. A grand total of ~530 thousand sources were detected on stacks of NIRCam 3.56 and 4.44 µm mosaics. We assessed the photometric accuracy by comparing fluxes and colours against archival catalogues. We also provide photometric redshift estimates, statistically validated against a large set of robust spectroscopic data. Conclusions. The catalogues are publicly available on the ASTRODEEP website.

Twins in diversity: understanding circumstellar disc evolution in the twin clusters of W5 complex

ABSTRACT Young star-forming regions in massive environments are ideal test beds to study the influence of surroundings on the evolution of discs around low-mass stars. We explore two distant young clusters, IC 1848-East and West located in the massive W5 complex. These clusters are unique due to their similar (distance, age and extinction) yet distinct (stellar density and far-ultraviolet radiation fields) physical properties. We use deep multiband photometry in optical, near-infrared and mid-infrared wavelengths complete down to the substellar limit in at least five bands. We trace the spectral energy distribution of the sources to identify the young pre-main sequence members in the region and derive their physical parameters. The disc fraction for the East and West clusters down to 0.1 M$_\odot$ was found to be $\sim 27\,\pm$ 2 per cent (N$_\mathrm{disc}$ = 184, N$_\mathrm{discless}$ = 492) and $\sim 17\,\pm$ 1 per cent (N$_\mathrm{disc}$ = 173, N$_\mathrm{discless}$ = 814), respectively. While no spatial variation in the disc fraction is observed, these values are lower than those in other nearby young clusters. Investigating the cause of this decrease, we find a correlation with the intense feedback from massive stars throughout the cluster area. We also identified the disc sources undergoing accretion and observed the mass accretion rates to exhibit a positive linear relationship with the stellar host mass and an inverse relationship with stellar age. Our findings suggest that the environment significantly influences the dissipation of discs in both clusters. These distant clusters, characterized by their unique attributes, can serve as templates for future studies in outer galaxy regions, offering insights into the influence of feedback mechanisms on star and planetary formation.

X-ray and optical observations of the millisecond pulsar binary PSR J1431–4715

We present the first X-ray observation of the energetic millisecond pulsar binary PSR J1431−4715, performed with XMM-Newton and complemented with fast optical multi-band photometry acquired with the ULTRACAM instrument at ESO-NTT. It is found as a faint X-ray source without a significant orbital modulation. This contrasts with the majority of systems that instead display substantial X-ray orbital variability. The X-ray spectrum is dominated by non-thermal emission and, due to the lack of orbital modulation, does not favour an origin in an intrabinary shock between the pulsar and companion star wind. While thermal emission from the neutron star polar cap cannot be excluded in the soft X-rays, the dominance of synchrotron emission favours an origin in the pulsar magnetosphere that we describe at both X-ray and gamma-ray energies with a synchro-curvature model. The optical multi-colour light curve folded at the 10.8 h orbital period is double-humped and dominated by ellipsoidal effects, but also affected by irradiation. The ULTRACAM light curves are fit with several models encompassing direct heating and a cold spot, or heat redistribution after irradiation either through convection or convection plus diffusion. Despite the inability to constrain the best irradiation models, the fits provide consistent system parameters, giving an orbital inclination of 59 ± 6° and a distance of 3.1 ± 0.3 kpc. The companion is found to be an F-type star, underfilling its Roche lobe (fRL = 73 ± 4%) with a mass of 0.20 ± 0.04 M⊙, confirming the redback status, but hotter than the majority of redbacks. The stellar dayside and nightside temperatures of 7500 K and 7400 K, respectively, indicate a weak irradiation effect on the companion, likely due to its high intrinsic luminosity. Although the pulsar mass cannot be precisely derived, a heavy (1.8−2.2 M⊙) neutron star is favoured.

The tight correlation between PAH and CO emission from z ∼ 0 to 4

Aims. The cold molecular gas mass is one of the crucial, yet challenging, parameters in galaxy evolution studies. Here, we introduce a new calibration and a method for estimating molecular gas masses using mid-infrared (MIR) photometry. This topic is timely as the James Webb Space Telescope (JWST) now allows us to detect the MIR emission of typical main-sequence galaxies across a wide range of masses and star formation rates with modest time investments. Additionally, this Letter highlights the strong synergy between ALMA and JWST for studies of dust and gas at cosmic noon. Methods. We combined a sample of 14 main-sequence galaxies at z = 1 − 3 with robust CO detections and multi-band MIR photometry, along with a literature sample at z = 0 − 4 with CO and polycyclic aromatic hydrocarbon (PAH) spectroscopy, to study the relationship between PAH, CO(1–0), and total IR luminosities. PAH luminosities are derived by modelling a wealth of rest-frame UV to sub-millimetre data. The new z = 1 − 3 sample extends previous high-z studies to PAH and CO luminosities that are about an order of magnitude lower, into the regime of local starbursts, for the first time. Results. The PAH-to-CO luminosity ratio remains constant across a wide range of luminosities, for various galaxy types, and throughout the explored redshift range. In contrast, the PAH-to-IR and CO-to-IR luminosity ratios deviate from a constant value at high IR luminosities. The intrinsic scatter in the L(PAH)–L′(CO) relation is 0.21 dex, with a median of 1.40 and a power-law slope of 1.07 ± 0.04. Both the PAH–IR and CO–IR relations are sub-linear. Given the tight and uniform PAH–CO relation over ∼3 orders of magnitude, we provide a recipe for estimating the cold molecular gas mass of galaxies from PAH luminosities, with a PAH-to-molecular gas conversion factor of αPAH7.7 = (3.08 ± 1.08)(4.3/αCO) M⊙/L⊙. This method opens a new window to explore the gas content of galaxies beyond the local Universe using multi-wavelength JWST/MIRI imaging.

Two black widow pulsars in the optical and X-rays

Context. Two millisecond pulsars, PSR J1513−2550 and PSR J2017−1614, with spin periods of about 2.1 and 2.3 ms were recently discovered in the radio and γ-rays and classified as black widow pulsars in tight binary stellar systems with orbital periods of about 4.3 and 2.3 h. Aims. Our goals are to reveal the fundamental parameters of both systems and their binary components using multi-wavelength observations. Methods. We carried out the first time-series multi-band optical photometry of the objects with the 2.1-m telescope of the Observatorio Astronómico Nacional San Pedro Mártir, the 6.5-m Magellan-1 telescope, and the 10.4-m Gran Telescopio Canarias. To derive the parameters of both systems, we fitted the obtained light curves with a model assuming heating of the companion by the pulsar. We also analysed archival X-ray data obtained with the XMM-Newton observatory. Results. For the first time, we firmly identified J1513−2550 in the optical and both pulsars in X-rays. The optical light curves of both systems have a single peak per orbital period with a peak-to-peak amplitude of ≳2 magnitudes. The J2017−1614 light curves are symmetric, while J1513−2550 demonstrates strong asymmetry whose nature remains unclear. Conclusions. We constrained the orbital inclinations, pulsar masses, companion temperatures and masses, and the distances to both systems. We also conclude that J2017−1614 may contain a massive neutron star of 2.4 ± 0.6 M⊙. The X-ray spectra of both sources can be fitted by power laws with parameters typical of black widow systems.

Spot modelling through multi-band photometry. Analysis of V1298 Tau

Stellar activity is comprised of various phenomena, mainly spots and faculae. It is one of the main sources of noise in exoplanetary observations because it affects both spectroscopic and photometric observations. In studying young active planetary systems, we need to model the activity of the host stars to remove astrophysical noise from our observational data. We model the contribution of stellar spots in photometric observations. Through the use of multi-band photometry, we aim to extract the geometric properties of the spots and constrain their temperatures. We analysed multi-band photometric observations acquired with the 80 cm Marcon telescope of the Osservatorio Polifunzionale del Chianti of V1298 Tau, assuming the photometric modulation observed in different bands is attributed to cold spots. We constrained the effective temperature of the active regions present on the surface of V1298 Tau, resulting from a combination of spots and faculae. We tested our hypothesis on solar data, verifying that we successfully measured the size of the dominant active region and its averaged effective temperature.

Emission-line galaxies at z ∼ 1 from near-IR HST Slitless Spectroscopy: Metallicities, star formation rates and redshift confirmations from VLT/FORS2 spectroscopy

Abstract We follow up emission line galaxies identified through the near-infrared slitless HST/WFC3 WISP survey with VLT/FORS2 optical spectroscopy. Over 4 WISP fields, we targetted 85 of 138 line emission objects at 0.4 < z < 2 identified in WFC3 spectroscopy. Half the galaxies are fainter than HAB = 24 mag, and would not have been included in many well-known surveys based on broad-band magnitude selection. We confirm 95% of the initial WFC3 grism redshifts in the 38 cases where we detect lines in FORS2 spectroscopy. However, for targets which exhibited a single emission line in WFC3, up to 65% at z < 1.28 did not have expected emission lines detected in FORS2 and hence may be spurious (although this false-detection rate improves to 33% using the latest public WISP emission line catalogue). From the Balmer decrement the extinction of the WISP galaxies is consistent with A(Hα) = 1 mag. From SED fits to multi-band photometry including Spitzer 3.6 μm, we find a median stellar mass of log10(M⋆/M⊙) = 8.94. Our emission-line-selected galaxies tend to lie above the star-forming main sequence (i.e. higher specific star formation rates). Using [O iii], [O ii] and Hβ lines to derive gas-phase metallicities, we find typically sub-solar metallicities, decreasing with redshift. Our WISP galaxies lie below the z = 0 mass-metallicity relation, and galaxies with higher star formation rates tend to have lower metallicity. Finally, we find a strong increase with redshift of the Hα rest-frame equivalent width in this emission-line selected sample, with higher EW0 galaxies having larger [O iii]/Hβ and O32 ratios on average, suggesting lower metallicity or higher ionisation parameter in these extreme emission line galaxies.

K2-399 b is not a planet

Context. The transit technique has been very efficient over the past decades in detecting planet-candidate signals. The so-called statistical validation approach has become a popular way of verifying a candidate’s planetary nature. However, the incomplete consideration of false-positive scenarios and data quality can lead to misinterpretation of the results. Aims. In this work, we revise the planetary status of K2-399 b, a validated planet with an estimated false-positive probability of 0.078% located in the middle of the so-called Neptunian desert, and hence a potential key target for atmospheric prospects. Methods. We used radial velocity data from the CARMENES, HARPS, and TRES spectrographs, as well as ground-based multiband transit photometry provided by LCOGT MuSCAT3 and broad band photometry to test the planetary scenario. Results. Our analysis of the available data does not support the existence of this (otherwise key) planet, and instead points to a scenario composed of an early G-dwarf orbited –with a period of a 846.62−0.28+0.22 days– by a pair of eclipsing M-dwarfs (hence a hierarchical eclipsing binary) likely in the mid-type domain. We thus demote K2-399 b as a planet. Conclusions. We conclude that the validation process, while very useful to prioritize follow-up efforts, must always be conducted with careful attention to data quality while ensuring that all possible scenarios have been properly tested to get reliable results. We also encourage developers of validation algorithms to ensure the accuracy of a priori probabilities for different stellar scenarios that can lead to this kind of false validation. We further encourage the use of follow-up observations when possible (such as radial velocity and/or multiband light curves) to confirm the planetary nature of detected transiting signals rather than only relying on validation tools.

Revealing the chemical structure of the magellanic clouds with APOGEE. I. Calculating individual stellar ages of RGB stars in the large magellanic cloud

Abstract Stellar ages are critical for understanding the temporal evolution of a galaxy. We calculate the ages of over 6000 red giant branch stars in the Large Magellanic Cloud (LMC) observed with SDSS-IV / APOGEE-S. Ages are derived using multi-band photometry, spectroscopic parameters ($\rm T_{eff}$, log g, [Fe/H], and [α/Fe]) and stellar isochrones and the assumption that the stars lie in a thin inclined plane to get accurate distances. The isochrone age and extinction are varied until a best match is found for the observed photometry. We perform validation using the APOKASC sample, which has asteroseismic masses and accurate ages, and find that our uncertainties are ∼20% and range from ∼1–3 Gyr for the calculated ages (most reliable below 10 Gyr). Here we present the LMC age map as well as the age-radius relation and an accurate age-metallicity relation (AMR). The age map and age-radius relation reveal that recent star formation in the galaxy was more centrally located and that there is a slight dichotomy between the north and south with the northern fields being slightly younger. The northern fields that cover a known spiral arm have median ages of ≳2 Gyr, which is the time when an interaction with the SMC is suggested to have happened. The AMR is mostly flat especially for older ages although recently (about 2.0–2.5 Gyr ago) there is an increase in the median [Fe/H]. Based on the time frame, this might also be attributed to the close interaction between the LMC and SMC.

Euclid. III. The NISP instrument

The Near-Infrared Spectrometer and Photometer (NISP) on board the satellite provides multiband photometry and $R slitless grism spectroscopy in the 950--2020\,nm wavelength range. In this reference article, we illuminate the background of NISP's functional and calibration requirements, describe the instrument's integral components, and provide all its key properties. We also sketch the processes needed to understand how NISP operates and is calibrated as well as its technical potentials and limitations. Links to articles providing more details and the technical background are included. The NISP's 16 H2RG detectors with a plate scale of $ deliver a field of view of 0.57\,deg$^2$. In photometric mode, NISP reaches a limiting magnitude of sim \,24.5\,AB\,mag in three photometric exposures of about 100\,s in exposure time for point sources and with a S/N of five. For spectroscopy, NISP's point-source sensitivity is a SNR = 3.5 detection of an emission line with flux sim \,$2 $ integrated over two resolution elements of 13.4\ in 3times 560\,s grism exposures at 1.6\ (redshifted Halpha ). Our calibration includes on-ground and in-flight characterisation and monitoring of the pixel-based detector baseline, dark current, non-linearity, and sensitivity to guarantee a relative photometric accuracy better than 1.5<!PCT!> and a relative spectrophotometry better than 0.7<!PCT!>. The wavelength calibration must be accurate to 5\ or better. The NISP is the state-of-the-art instrument in the near-infrared for all science beyond small areas available from HST and JWST -- and it represents an enormous advance from any existing instrumentation due to its combination of field size and high throughput of telescope and instrument. During six-year survey covering 14\,000\,deg$^2$ of extragalactic sky, NISP will be the backbone in determining distances of more than a billion galaxies. Its near-infrared data will become a rich reference imaging and spectroscopy data set for the coming decades.

The Fourth S-PLUS Data Release: 12-filter photometry covering ~3000 square degrees in the southern hemisphere

The Southern Photometric Local Universe Survey (S-PLUS) is a project to map $ sq deg of the sky using twelve bands (seven narrow and five broadbands). Observations are performed with the T80-South telescope, a robotic telescope located at the Cerro Tololo Observatory in Chile. The survey footprint consists of several large contiguous areas, including fields at high and low galactic latitudes, and towards the Magellanic Clouds. S-PLUS uses fixed exposure times to reach point source depths of about $21$ mag in the $griz$ and $20$ mag in the $u$ and the narrow filters. This paper describes the S-PLUS Data Release 4 (DR4), which includes calibrated images and derived catalogues for over 3000 sq deg, covering the aforementioned area. The catalogues provide multi-band photometry performed with the tools DoPHOT and SExtractor -- point spread function ( and aperture photometry, respectively. In addition to the characterization, we also present the scientific potential of the data. We use statistical tools to present and compare the photometry obtained through different methods. Overall we find good agreement between the different methods, with a slight systematic offset of 0.05\,mag between our and aperture photometry. We show that the astrometry accuracy is equivalent to that obtained in previous S-PLUS data releases, even in very crowded fields where photometric extraction is challenging. The depths of main survey (MS) photometry for a minimum signal-to-noise ratio $S/N = 3$ reach from $ for the bluer bands to $ mag on the red. The range of magnitudes over which accurate photometry is obtained is shallower, reaching $ to $ mag depending on the filter. Based on these photometric data, we provide star-galaxy-quasar classification and photometric redshift for millions of objects. We demonstrate the versatility of the data by presenting the results of a project to identify members of four Abell galaxy clusters in the Local Universe. The S-PLUS DR4 data allow for a reliable assessment of cluster membership out to a large radius corresponding to $5 $. The S-PLUS DR4 can be accessed through the survey data portal. All the software used to generate the catalogues for this release and the scientific investigation presented is available in the collaboration GitHub repository. The S-PLUS DR4 consists of a large, calibrated public dataset, providing powerful ways for studying Galactic and extra-galactic objects through an extensive set of (broad and narrow) filters.

OMEGACat. III. Multiband Photometry and Metallicities Reveal Spatially Well-mixed Populations within ω Centauri’s Half-light Radius

ω Centauri, the most massive globular cluster in the Milky Way, has long been suspected to be the stripped nucleus of a dwarf galaxy that fell into the Galaxy a long time ago. There is considerable evidence for this scenario including a large spread in metallicity and an unusually large number of distinct subpopulations seen in photometric studies. In this work, we use new Multi-Unit Spectroscopic Explorer spectroscopic and Hubble Space Telescope photometric catalogs to investigate the underlying metallicity distributions as well as the spatial variations of the populations within the cluster up to its half-light radius. Based on 11,050 member stars, the [M/H] distribution has a median of (−1.614 ± 0.003) dex and a large spread of ∼1.37 dex, reaching from −0.67 to −2.04 dex for 99.7% of the stars. In addition, we show the chromosome map of the cluster, which separates the red giant branch stars into different subpopulations, and analyze the subpopulations of the most metal-poor component. Finally, we do not find any metallicity gradient within the half-light radius, and the different subpopulations are well mixed.

No Longer Impossible: The Self-lensing Binary KIC 8145411 is a Triple

Five self-lensing binaries (SLBs) have been discovered with data from the Kepler mission. One of these systems is KIC 8145411, which was reported to host an extremely low mass (ELM; 0.2 M ⊙) white dwarf (WD) in a 456 days orbit with a solar-type companion. The system has been dubbed “impossible,” because evolutionary models predict that ∼0.2 M ⊙ WDs should only be found in tight orbits (P orb ≲ days). In this work, we show that KIC 8145411 is in fact a hierarchical triple system: it contains a WD orbiting a solar-type star, with another solar-type star ∼700 au away. The wide companion was unresolved in the Kepler light curves, was just barely resolved in Gaia DR3, and is resolved beyond any doubt by high-resolution imaging. We show that the presence of this tertiary confounded previous mass measurements of the WD for two reason: it dilutes the amplitude of the self-lensing pulses, and it reduces the apparent radial velocity (RV) variability amplitude of the WD’s companion due to line blending. By jointly fitting the system’s light curves, RVs, and multi-band photometry using a model with two luminous stars, we obtain a revised WD mass of (0.53 ± 0.01)M ⊙. Both luminous stars are near the end of their main-sequence evolution. The WD is thus not an ELM WD, and the system does not suffer the previously proposed challenges to its formation history. Similar to the other SLBs and the population of astrometric WD binaries recently identified from Gaia data, KIC 8145411 has parameters in tension with standard expectations for formation through both stable and unstable mass transfer (MT). The system’s properties are likely best understood as a result of unstable MT from an AGB star donor.

Atmospheric Waves Driving Variability and Cloud Modulation on a Planetary-mass Object

Planetary-mass objects and brown dwarfs at the transition (T eff ∼ 1300 K) from relatively red L dwarfs to bluer mid-T dwarfs show enhanced spectrophotometric variability. Multiepoch observations support atmospheric planetary-scale (Kelvin or Rossby) waves as the primary source of this variability; however, large spots associated with the precipitation of silicate and metal clouds have also been theorized and suggested by Doppler imaging. We applied both wave and spotted models to fit near-infrared (NIR), multiband (Y/J/H/K) photometry of SIMP J013656.5+093347 (hereafter SIMP0136) collected at the Canada–France–Hawaii Telescope using the Wide-field InfraRed Camera. SIMP0136 is a planetary-mass object (12.7 ± 1.0 M J) at the L/T transition (T2 ± 0.5) known to exhibit light-curve evolution over multiple rotational periods. We measure the maximum peak-to-peak variability of 6.17% ± 0.46%, 6.45% ± 0.33%, 6.51% ± 0.42%, and 4.33% ± 0.38% in the Y, J, H, and K bands, respectively, and find evidence that wave models are preferred for all four NIR bands. Furthermore, we determine that the spot size necessary to reproduce the observed variations is larger than the Rossby deformation radius and Rhines scale, which is unphysical. Through the correlation between light curves produced by the waves and associated color variability, we find evidence of planetary-scale, wave-induced cloud modulation and breakup, similar to Jupiter’s atmosphere and supported by general circulation models. We also detect a 93.°8 ± 7.°4 (12.7σ) phase shift between the H − K and J − H color time series, providing evidence for complex vertical cloud structure in SIMP0136's atmosphere.

CEERS: 7.7 μm PAH Star Formation Rate Calibration with JWST MIRI

We test the relationship between UV-derived star formation rates (SFRs) and the 7.7 μm polycyclic aromatic hydrocarbon luminosities from the integrated emission of galaxies at z ∼ 0–2. We utilize multiband photometry covering 0.2–160 μm from the Hubble Space Telescope, CFHT, JWST, Spitzer, and Herschel for galaxies in the Cosmic Evolution Early Release Science (CEERS) Survey. We perform spectral energy distribution (SED) modeling of these data to measure dust-corrected far-UV (FUV) luminosities, L FUV, and UV-derived SFRs. We then fit SED models to the JWST/MIRI 7.7–21 μm CEERS data to derive rest-frame 7.7 μm luminosities, L 770, using the average flux density in the rest-frame MIRI F770W bandpass. We observe a correlation between L 770 and L FUV, where logL770∝(1.27±0.04)logLFUV . L 770 diverges from this relation for galaxies at lower metallicities, lower dust obscuration, and for galaxies dominated by evolved stellar populations. We derive a “single-wavelength” SFR calibration for L 770 that has a scatter from model estimated SFRs (σ ΔSFR) of 0.24 dex. We derive a “multiwavelength” calibration for the linear combination of the observed FUV luminosity (uncorrected for dust) and the rest-frame 7.7 μm luminosity, which has a scatter of σ ΔSFR = 0.21 dex. The relatively small decrease in σ suggests this is near the systematic accuracy of the total SFRs using either calibration. These results demonstrate that the rest-frame 7.7 μm emission constrained by JWST/MIRI is a tracer of the SFR for distant galaxies to this accuracy, provided the galaxies are dominated by star formation with moderate-to-high levels of attenuation and metallicity.

Combined spin orientation and phase function of asteroids

Context. Large sky surveys provide numerous non-targeted observations of small bodies of the Solar System. The upcoming LSST of the Vera C. Rubin Observatory will be the largest source of small body photometry in the next decade. With non-coordinated epochs of observation, colors – and therefore taxonomy and composition – can only be computed by comparing absolute magnitudes obtained in each filter by solving the phase function (evolution of brightness of the small body against the solar phase angle). Current models in use in the community (HG, HG12*, and HG1G2), however, fail to reproduce the long-term photometry of many targets due to the change in the aspect angle between apparitions. Aims. We aim to derive a generic yet simple phase function model accounting for the variable geometry of the small bodies over multiple apparitions. Methods. As a spinoff of the HG1 G2 model, we propose the sHG1G2 phase function model in which we introduce a term describing the brightness changes due to spin orientation and polar oblateness. We applied this new model to 13 245 908 observations of 122 675 Solar System objects (SSOs). These observations were acquired in the g and r filters with the Zwicky Transient Facility between November 1, 2019 and December 1, 2023. We retrieved them and implemented the new sHG1G2 model in FINK, a broker of alerts designed for the LSST. Results. The sHG1G2 model leads to smaller residuals than other phase function models, providing a better description of the photometry of asteroids. We determined the absolute magnitude, H, and phase function coefficients (G1, G2) in each filter, the spin orientation (α0, δ0), and the polar-to-equatorial oblateness, R, for 95 593 SSOs, which constitutes about a tenfold increase in the number of characterized objects compared to the current census. Conclusions. The application of the sHG1 G2 model to ZTF alert data using the FINK broker shows that the model is appropriate for extracting physical properties of asteroids from multi-band and sparse photometry, such as the forthcoming LSST survey.

Detection of Na in the atmosphere of the hot Jupiter HAT-P-55b

The spectral signatures of optical absorbers, when combined with those of infrared molecules, play a critical role in constraining the cloud properties of exoplanet atmospheres. We aim to use optical transmission spectroscopy to confirm the tentative color signature previously observed by multiband photometry in the atmosphere of hot Jupiter HAT-P-55b. We observed a transit of the HAT-P-55b with the OSIRIS spectrograph on the Gran Telescopio Canarias (GTC). We created two sets of spectroscopic light curves, using the conventional band-integrated method and the newly proposed pixel-based method, to derive the transmission spectrum. We performed Bayesian spectral retrieval analyses on the transmission spectrum to interpret the observed atmospheric properties. The transmission spectra derived from the two methods are consistent, both spectrally resolving the tentative color signature observed by MuSCAT2. The retrievals on the combined OSIRIS and MuSCAT2 transmission spectrum yield a detection of Na at 5.5σ and a tentative detection of MgH at 3.4σ. The current optical-only wavelength coverage cannot constrain the absolute abundances of the atmospheric species. Space-based observations covering the molecular infrared bands or ground-based high-resolution spectroscopy are needed to further constrain the atmospheric properties of HAT-P-55b.

The original composition of the gas forming first-generation stars in clusters: Insights from HST and JWST

Globular cluster (GC) stars composed of pristine material, also known as first-generation (1G) stars, are not chemically homogeneous as they exhibit extended sequences in the chromosome map (ChM). Recent studies characterized 1G stars within the center of 55 Galactic GCs, revealing metallicity variations. Despite this progress, several unanswered questions persist, particularly concerning the link between the 1G metallicity spread and factors such as the radial distance from the cluster center or the host GC parameters. Additionally, it remains unclear whether the extended 1G sequence phenomenon is exclusive to old Galactic GCs with multiple populations. This work addresses these open issues, examining 1G stars in different environments. First, we combine Hubble Space Telescope (HST) and James Webb Space Telescope photometry of the GC 47\,Tucanae to study 1G stars at increasing distances from the cluster center. We find that metal-rich 1G stars are more centrally concentrated than metal-poor ones, suggesting a metallicity radial gradient. Additionally, the two groups of 1G stars share similar kinematics. Since our analysis focuses on giant stars in the cluster center and M dwarfs in external fields, we discuss the possibility that the metallicity distribution depends on stellar mass. Subsequently, we analyze HST multi-band photometry of two simple-population clusters, NGC\,6791 and NGC\,1783, revealing elongated sequences in the ChM associated with metallicity variations. Finally, we investigate the 1G color distribution in 51 GCs, finding no connections with the host cluster parameters. These results shed light on the complex nature of 1G stars, providing insights into the GC formation environment.

A MIRI Search for Planets and Dust around WD 2149+021

The launch of JWST has ushered in a new era of high-precision infrared astronomy, allowing us to probe nearby white dwarfs for cold dust, exoplanets, and tidally heated exomoons. While previous searches for these exoplanets have successfully ruled out companions as small as 7–10 Jupiter masses (M Jup), no instrument prior to JWST has been sensitive to the likely more common sub-Jovian-mass planets around white dwarfs. In this paper, we present the first multiband photometry (F560W, F770W, F1500W, F2100W) taken of WD 2149+021 with the Mid-Infrared Instrument on JWST. After a careful search for both resolved and unresolved planets, we do not identify any compelling candidates around WD 2149+021. Our analysis indicates that we are sensitive to companions as small as ∼0.5 M Jup outwards of 1.″263 (28.3 au) and ∼1.0 M Jup at the innermost working angle (0.″654, 14.7 au) at 3 Gyr with 5σ confidence, placing significant constraints on any undetected companions around this white dwarf. The results of these observations emphasize the exciting future of sub-Jovian planet detection limits by JWST, which can begin to constrain how often these planets survive their host stars' evolution.