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We perform the asteroseismic fitting of four DAVs using a grid of WDEC models with chemical profiles that closely mimic those of the LPCODE models and compare them with published asteroseismic fitting results using the LPCODE. These four objects are KIC 11911480, J113655.17+040952.6, KIC 4552982, and GD 1212. The similarities in the results in those controlled experiments point to a consistency in the models. Given similar input, the LPCODE and the WDEC make similar models and calculate similar periods. We further perform the asteroseismic fitting of the same four DAVs by relaxing the constraints on the chemical profiles. We explore the effects of different methods for weighing the modes when calculating the goodness of fit of the models, as well as the effect of only including a subset of the known period spectrum. Such numerical experiments can help place recent and future efforts in the pipeline fitting of numerous DAVs and DBVs using the WDEC on a firmer footing. [ABSTRACT FROM AUTHOR]

With space missions such as Kepler, TESS, and Gaia, we have a wealth of data on pulsating white dwarfs that can be leveraged in white dwarf asteroseismology. We address the question of the proportion of white dwarfs with thin hydrogen layers versus those with thick hydrogen layers. We also provide a mass–radius relation for carbon–oxygen-core, hydrogen-atmosphere white dwarfs. Such a relationship can be used in conjunction with magnitudes and distance measurements to constrain the mass and effective temperature of the white dwarfs. We select nine hydrogen-atmosphere pulsating white dwarfs for their rich pulsation spectra. From such pulsation spectra, we can derive the asymptotic period spacing, which in turn allows us to determine the thickness of the hydrogen and helium envelope of the models, without having to perform period-by-period fitting. We find that the majority of the white dwarfs have thicker hydrogen layers and we determine an upper limit of M r = 1–10−2.2 for the location of the base of the helium layer, in accordance with stellar evolution models. We confirm a finding from earlier studies that used a mass–radius relation and Gaia data to determine the effective temperatures of white dwarfs. The Gaia data systematically point to white dwarfs of lower effective temperature than indicated by the spectroscopy. Our results also support the hypothesis that white dwarfs with thicker hydrogen layers are more common than those with thinner layers. [ABSTRACT FROM AUTHOR]

HD 327083 is a binary system that consists of two supergiant components and exhibits the B[e] phenomenon. In this paper, we report the determination of a new set of the system's fundamental parameters using a combination of photometric and spectroscopic data as well as the Gaia EDR3 distance. We found that the orbital period of the system is 107.68 ± 0.02 days. The spectral line content implies the effective temperatures of ≈7000 K and 25,400 ± 1400 K, while the photometric variations are consistent with the radii of ≈106 R ⊙ and ≈10 R ⊙ for the cool and hot components, respectively. The absorption lines of the cool component show a radial velocity semiamplitude of 48.3 ± 1.7 km s−1, similar to that of the emission lines that originate around the hot component. The inclination of the system to the line of sight is 47 − 20 + 17 °. Modeling of the system's evolutionary history suggests that the components have masses of ∼12.5 M ⊙ and currently undergo mass transfer between them. This configuration, which takes in heating of the surface of the cool component by the radiation from the hot one, can reproduce the photometric and spectroscopic data and is in agreement with previous infrared observations of the circumbinary disk. The results of this study further confirm the hypothesis that the reason for the presence of the B[e] phenomenon in most objects is a consequence of the evolution of various binary systems. [ABSTRACT FROM AUTHOR]

Dark matter could accumulate around neutron stars in sufficient amounts to affect their global properties. In this work, we study the effect of a specific model for dark matter—a massive and self-interacting vector (spin-1) field—on neutron stars. We describe the combined systems of neutron stars and vector dark matter using Einstein–Proca theory coupled to a nuclear matter term and find scaling relations between the field and metric components in the equations of motion. We construct equilibrium solutions of the combined systems, compute their masses and radii, and also analyze their stability and higher modes. The combined systems admit dark matter (DM) core and cloud solutions. Core solutions compactify the neutron star component and tend to decrease the total mass of the combined system. Cloud solutions have the inverse effect. Electromagnetic observations of certain cloud-like configurations would appear to violate the Buchdahl limit. This could make Buchdahl-limit-violating objects smoking gun signals for dark matter in neutron stars. The self-interaction strength is found to significantly affect both mass and radius. We also compare fermion Proca stars to objects where the dark matter is modeled using a complex scalar field. We find that fermion Proca stars tend to be more massive and geometrically larger than their scalar field counterparts for equal boson masses and self-interaction strengths. Both systems can produce degenerate masses and radii for different amounts of DM and DM particle masses. [ABSTRACT FROM AUTHOR]

Dark matter could accumulate around neutron stars in sufficient amounts to affect their global properties. In this work, we study the effect of a specific model for dark matter—a massive and self-interacting vector (spin-1) field—on neutron stars. We describe the combined systems of neutron stars and vector dark matter using Einstein–Proca theory coupled to a nuclear matter term and find scaling relations between the field and metric components in the equations of motion. We construct equilibrium solutions of the combined systems, compute their masses and radii, and also analyze their stability and higher modes. The combined systems admit dark matter (DM) core and cloud solutions. Core solutions compactify the neutron star component and tend to decrease the total mass of the combined system. Cloud solutions have the inverse effect. Electromagnetic observations of certain cloud-like configurations would appear to violate the Buchdahl limit. This could make Buchdahl-limit-violating objects smoking gun signals for dark matter in neutron stars. The self-interaction strength is found to significantly affect both mass and radius. We also compare fermion Proca stars to objects where the dark matter is modeled using a complex scalar field. We find that fermion Proca stars tend to be more massive and geometrically larger than their scalar field counterparts for equal boson masses and self-interaction strengths. Both systems can produce degenerate masses and radii for different amounts of DM and DM particle masses.

Hydrogen atmosphere white dwarf KUV03442+0719 was first reported as a pulsator by Gianninas et al. in 2006. Follow-up campaigns by Su et al. revealed more periods. Some spectroscopic results suggest that KUV03442+0719 has a slightly below-average mass and an effective temperature of 11,000 K. However, Gaia data (parallax and magnitude) suggest that it may be a low-mass white dwarf. Such an object would have a helium core. We perform asteroseismic fitting of KUV03442+0719, modeling it both as a carbon/oxygen normal mass white dwarf, and a helium-core low-mass white dwarf. To perform the study, we perform a grid search with WDEC models, refined by simplex minimization of the best fits. Both analyses result in best-fit models that are comparable in terms of quality of fit. More pulsation data would be required to allow us to distinguish between the two scenarios. We present and contrast our results with expectations from stellar evolution. We also provide analytic formulae for a temperature-dependent mass–radius relationship for helium-core white dwarfs. [ABSTRACT FROM AUTHOR]

Motivated by the recent surge in interest concerning white dwarf (WD) planets, this work presents the first numerical exploration of WD-driven atmospheric escape, whereby the high-energy radiation from a hot/young WD can trigger the outflow of the hydrogen–helium envelope for close-in planets. As a pilot investigation, we focus on two specific cases: a gas giant and a sub-Neptune-sized planet, both orbiting a rapidly cooling WD with mass M _* = 0.6 M _⊙ and separation a = 0.02 au. In both cases, the ensuing mass outflow rates exceed 10 ^14 g s ^−1 for WD temperatures greater than T _WD ≳ 50,000 K. At T _WD ≃ 18,000 K (22,000 K), the sub-Neptune (gas giant) mass outflow rate approaches 10 ^12 g s ^−1 , i.e., comparable to the strongest outflows expected from close-in planets around late main-sequence stars. Whereas the gas giant remains virtually unaffected from an evolutionary standpoint, atmospheric escape may have sizable effects for the sub-Neptune, depending on its dynamical history, e.g., assuming that the hydrogen–helium envelope makes up 1% (4%) of the planet mass, the entire envelope would be evaporated away so long as the planet reaches 0.02 au within the first 230 Myr (130 Myr) of the WD formation. We discuss how these results can be generalized to eccentric orbits with effective semimajor axis $a^{\prime} =a/{(1-{e}^{2})}^{1/4}$ , which receive the same orbit-averaged irradiation. Extended to a much broader parameter space, this approach can be exploited to model the expected demographics of WD planets as a function of their initial mass, composition, and migration history, as well as their potential for habitability.

We report the discovery of two directly imaged, giant planet candidates orbiting the metal-rich, hydrogen atmosphere white dwarfs WD 1202−232 and WD 2105−82. JWST’s Mid-Infrared Instrument (MIRI) data on these two stars show a nearby resolved source at a projected separation of 11.47 and 34.62 au, respectively. Assuming the planets formed at the same time as their host stars, with total ages of 5.3 and 1.6 Gyr, the MIRI photometry is consistent with giant planets with masses ≈1–7 M _Jup . The probability of both candidates being false positives due to red background sources is approximately 1 in 3000. If confirmed, these would be the first directly imaged planets that are similar in both age and separation to the giant planets in our own solar system, and they would demonstrate that widely separated giant planets like Jupiter survive stellar evolution. Giant planet perturbers are widely used to explain the tidal disruption of asteroids around metal-polluted white dwarfs. Confirmation of these two planet candidates with future MIRI imaging would provide evidence that directly links giant planets to metal pollution in white dwarf stars.

Rising ocean temperatures are threatening marine species and populations worldwide, and ectothermic taxa are particularly vulnerable. Echinoderms are an ecologically important phylum of marine ectotherms and shifts in their population dynamics can have profound impacts on the marine environment. The effects of warming on echinoderms are highly variable across controlled laboratory‐based studies. Accordingly, synthesis of these studies will facilitate the better understanding of broad patterns in responses of echinoderms to ocean warming. Herein, a meta‐analysis incorporating the results of 85 studies (710 individual responses) is presented, exploring the effects of warming on various performance predictors. The mean responses of echinoderms to all magnitudes of warming were compared across multiple biological responses, ontogenetic life stages, taxonomic classes, and regions, facilitated by multivariate linear mixed effects models. Further models were conducted, which only incorporated responses to warming greater than the projected end‐of‐century mean annual temperatures at the collection sites. This meta‐analysis provides evidence that ocean warming will generally accelerate metabolic rate (+32%) and reduce survival (−35%) in echinoderms, and echinoderms from subtropical (−9%) and tropical (−8%) regions will be the most vulnerable. The relatively high vulnerability of echinoderm larvae to warming (−20%) indicates that this life stage may be a significant developmental bottleneck in the near‐future, likely reducing successful recruitment into populations. Furthermore, asteroids appear to be the class of echinoderms that are most negatively affected by elevated temperature (−30%). When considering only responses to magnitudes of warming representative of end‐of‐century climate change projections, the negative impacts on asteroids, tropical species and juveniles were exacerbated (−51%, −34% and −40% respectively). The results of these analyses enable better predictions of how keystone and invasive echinoderm species may perform in a warmer ocean, and the possible consequences for populations, communities and ecosystems. [ABSTRACT FROM AUTHOR]

Sea Stars are one of the most incredible creatures in the coastal and open waters. In this study, 11 species of starfishes have been identified which belonging to six genera and five families in northern islands of Persian Gulf during May 2017 to September 2018. Among the species, Astropecten hemprichi (Müller & Troschel, 1842), Astropecten indicus (Döderlein, 1888), Astropecten polyacanthus polyacanthus (Muller and Troschel, 1842), Astropecten polyacanthus phragmorous (Muller and Troschel, 1842), Luidia hardwicki (Gray, 1840), Aquilonastra iranica (Mortensen, 1940), Linckia multifora (Lamarck, 1816), Culcita novaeguineae (Muller & Troschel, 1842) and Pentaceraster mammillatus (Audouin, 1826) have been reported in the past. The species of Aquilonastra watersi (O'Loughlin and Rowe, 2006) and Linckia laevigata (Linnaeus, 1758) are new recordsin the Persian Gulf.

Recent determinations of the total rate of the ^12 C+ ^12 C nuclear reaction show non-negligible differences with the reference reaction rate commonly used in previous stellar simulations. In addition, the current uncertainties in determining each exit channel constitute one of the main uncertainties in shaping the inner structure of super asymptotic giant branch stars that could have a measurable impact on the properties of pulsating ultramassive white dwarfs (WDs). We explore how new determinations of the nuclear reaction rate and its branching ratios affect the evolution of WD progenitors. We show that the current uncertainties in the branching ratios constitute the main uncertainty factor in determining the inner composition of ultramassive WDs and their progenitors. We found that the use of extreme branching ratios leads to differences in the central abundances of ^20 Ne of at most 17%, which are translated into differences of at most 1.3% and 0.8% in the cooling times and size of the crystallized core, respectively. However, the impact on the pulsation properties is small, less than 1 s for the asymptotic period spacing. We found that the carbon burns partially in the interior of ultramassive WD progenitors within a particular range of masses, leaving a hybrid CONe-core composition in their cores. The evolution of these new kinds of predicted objects differs substantially from the evolution of objects with pure CO cores. Differences in the size of the crystallized core and cooling times of up to 15% and 6%, respectively, lead to distinct patterns in the period spacing distribution.

We perform the asteroseismic fitting of four DAVs using a grid of WDEC models with chemical profiles that closely mimic those of the LPCODE models and compare them with published asteroseismic fitting results using the LPCODE. These four objects are KIC 11911480, J113655.17+040952.6, KIC 4552982, and GD 1212. The similarities in the results in those controlled experiments point to a consistency in the models. Given similar input, the LPCODE and the WDEC make similar models and calculate similar periods. We further perform the asteroseismic fitting of the same four DAVs by relaxing the constraints on the chemical profiles. We explore the effects of different methods for weighing the modes when calculating the goodness of fit of the models, as well as the effect of only including a subset of the known period spectrum. Such numerical experiments can help place recent and future efforts in the pipeline fitting of numerous DAVs and DBVs using the WDEC on a firmer footing.

With space missions such as Kepler, TESS, and Gaia, we have a wealth of data on pulsating white dwarfs that can be leveraged in white dwarf asteroseismology. We address the question of the proportion of white dwarfs with thin hydrogen layers versus those with thick hydrogen layers. We also provide a mass–radius relation for carbon–oxygen-core, hydrogen-atmosphere white dwarfs. Such a relationship can be used in conjunction with magnitudes and distance measurements to constrain the mass and effective temperature of the white dwarfs. We select nine hydrogen-atmosphere pulsating white dwarfs for their rich pulsation spectra. From such pulsation spectra, we can derive the asymptotic period spacing, which in turn allows us to determine the thickness of the hydrogen and helium envelope of the models, without having to perform period-by-period fitting. We find that the majority of the white dwarfs have thicker hydrogen layers and we determine an upper limit of M _r = 1–10 ^−2.2 for the location of the base of the helium layer, in accordance with stellar evolution models. We confirm a finding from earlier studies that used a mass–radius relation and Gaia data to determine the effective temperatures of white dwarfs. The Gaia data systematically point to white dwarfs of lower effective temperature than indicated by the spectroscopy. Our results also support the hypothesis that white dwarfs with thicker hydrogen layers are more common than those with thinner layers.

HD 327083 is a binary system that consists of two supergiant components and exhibits the B[e] phenomenon. In this paper, we report the determination of a new set of the system’s fundamental parameters using a combination of photometric and spectroscopic data as well as the Gaia EDR3 distance. We found that the orbital period of the system is 107.68 ± 0.02 days. The spectral line content implies the effective temperatures of ≈7000 K and 25,400 ± 1400 K, while the photometric variations are consistent with the radii of ≈106 R _⊙ and ≈10 R _⊙ for the cool and hot components, respectively. The absorption lines of the cool component show a radial velocity semiamplitude of 48.3 ± 1.7 km s ^−1 , similar to that of the emission lines that originate around the hot component. The inclination of the system to the line of sight is ${47}_{-20}^{+17}$ °. Modeling of the system's evolutionary history suggests that the components have masses of ∼12.5 M _⊙ and currently undergo mass transfer between them. This configuration, which takes in heating of the surface of the cool component by the radiation from the hot one, can reproduce the photometric and spectroscopic data and is in agreement with previous infrared observations of the circumbinary disk. The results of this study further confirm the hypothesis that the reason for the presence of the B[e] phenomenon in most objects is a consequence of the evolution of various binary systems.

Measuring the mass–radius relation of individual white dwarfs is an empirically challenging task that has been performed for only a few dozen stars. We measure the white dwarf mass–radius relation using the gravitational redshifts and radii of 135 white dwarfs in wide binaries with main-sequence companions. We obtain the radial velocities of these systems using the main-sequence companion, and subtract these Doppler redshifts from the white dwarfs’ apparent motions, isolating their gravitational redshifts. We use Gaia data to calculate the surface temperatures and radii of these white dwarfs, thereby deriving an empirical gravitational redshift–radius relation. This work demonstrates the utility of low-resolution Galactic surveys to measure the white dwarf equation of state. Our results are consistent with theoretical models, and represent the largest sample of individual white dwarf gravitational redshift measurements to date.

The recent collapse of predatory sunflower sea stars (Pycnopodia helianthoides) owing to sea star wasting disease (SSWD) is hypothesized to have contributed to proliferation of sea urchin barrens and losses of kelp forests on the North American west coast. We used experiments and a model to test whether restored Pycnopodia populations may help recover kelp forests through their consumption of nutritionally poor purple sea urchins (Strongylocentrotus purpuratus) typical of barrens. Pycnopodia consumed 0.68 S. purpuratus d−1, and our model and sensitivity analysis shows that the magnitude of recent Pycnopodia declines is consistent with urchin proliferation after modest sea urchin recruitment, and even small Pycnopodia recoveries could generally lead to lower densities of sea urchins that are consistent with kelp-urchin coexistence. Pycnopodia seem unable to chemically distinguish starved from fed urchins and indeed have higher predation rates on starved urchins owing to shorter handling times. These results highlight the importance of Pycnopodia in regulating purple sea urchin populations and maintaining healthy kelp forests through top-down control. The recovery of this important predator to densities commonly found prior to SSWD, whether through natural means or human-assisted reintroductions, may therefore be a key step in kelp forest restoration at ecologically significant scales. [ABSTRACT FROM AUTHOR]

Despite the high relevance of echinoderms in the Southern Mexican Pacific coral reef systems, there is no detailed analysis of their regional diversity. Based on records from field surveys and literature, this work analyzed for the first time the echinoderm species composition in coral reef systems in the Southern Mexican Pacific, evaluating their richness and distribution patterns. Fifty-two species represent the region (six Asteroidea, eight Echinoidea, 15 Ophiuroidea, and 23 Holothuroidea), a more significant number than other coral reef systems in the Mexican Pacific and Central America. New records are presented at the region, zone, and site level. At the zone level, the highest species richness occurred in Huatulco (52 species), followed by Ixtapa (45), Acapulco and Puerto Ángel (33), and Puerto Escondido (23). At the site level, La Entrega had the highest number of species (32), while various sites in Acapulco had <10 species. The species richness in the region showed considerably high representativeness since the non-parametric estimators suggested a potential increase of ~10% more species; a more significant percentage is expected in the Acapulco zone (47.5%). All echinoderms had 100% representativeness at the class level, except for Holothuroidea. It is recommended to use as many sampling methods and as many substrates as possible during different seasons and time days to contribute to increasing representativeness. Acapulco had an average taxonomic distinctness different from that predicted by regional models and an echinoderm assemblage more dissimilar from the other areas. The latter may be the product of the scarce sampling effort carried out in Acapulco and probably because it has one of the most degraded coral reef systems within the study area. [ABSTRACT FROM AUTHOR]

Sea Stars are one of the most incredible creatures in the coastal and open waters. In this study, 11 species of starfishes have been identified which belonging to six genera and five families in northern islands of Persian Gulf during May 2017 to September 2018. Among the species, Astropecten hemprichi (Müller & Troschel, 1842), Astropecten indicus (Döderlein, 1888), Astropecten polyacanthus polyacanthus (Muller and Troschel, 1842), Astropecten polyacanthus phragmorous (Muller and Troschel, 1842), Luidia hardwicki (Gray, 1840), Aquilonastra iranica (Mortensen, 1940), Linckia multifora (Lamarck, 1816), Culcita novaeguineae (Muller & Troschel, 1842) and Pentaceraster mammillatus (Audouin, 1826) have been reported in the past. The species of Aquilonastra watersi (O'Loughlin and Rowe, 2006) and Linckia laevigata (Linnaeus, 1758) are new records in the Persian Gulf. [ABSTRACT FROM AUTHOR]

The first data on lipid and fatty acid profiles for echinoderms and their symbionts with different lifestyle strategies are presented: tightly attached eulimids Thyca crystallina and Echineulima mittrei from sea stars Linclia laevigata and sea urchins Diadema setosum; and gall-forming eulimids from the genus Stiifer from sea stars Linckia laevigata and Culcita novaeguineae. The lipid profiles were studied using HPTLC and the fatty acids profile was analyzed by GC. The content of total lipids was higher in the tightly attached compared to gall-forming species. Triacylglycerols and cholesterol esters dominated in tightly attached symbionts. For all studied symbionts feeding on the fat-storing host tissues was revealed; however, the quality and degree of feeding differed. The cholesterol content was higher in tightly attached symbionts. It should be noted that the phospholipid content did not differ significantly in T. crystallina and S. utinomi from Linckia laevigata and E. mittrei from D. setosum, but it was lower in S. variabilis vs C. novaeguineae. For tightly attached molluscs, a predominance of monounsaturated fatty acids of bacterial and phytoplanktonic origins were detected, favoring additional food sources of exogenous origin. A significant amount of arachidonic fatty acid, as remarkable characteristic of tropic aquatic organisms and one of the detritus's trophic markers, was detected in all analyzed species. The value of the 18:1(n-9)/18:1(n-7) ratio, characterizing the degree of carnivory, is higher in gall-forming molluscs. The ratio 18:1(n-9)/16:0, indicating the activity of lipid metabolism, differed in symbionts; this is probably due to different sources and modes of their nutrition. [ABSTRACT FROM AUTHOR]

We describe four different approaches for the detection of magnetospheric accretion among Herbig Ae/Be stars with accretion disks. Studies of several unique objects have been carried out. One of the objects is the Herbig Ae star HD101412 with a comparatively strong magnetic field. The second is the early-type Herbig B6e star HD259431. The existence of a magnetosphere in these objects was not recognized earlier. In both cases, a periodicity in the variation of some line parameters, originating near the region of the disk/star interaction, has been found. The third object is the young binary system HD104237, hosting a Herbig Ae star and a T Tauri star. Based on the discovery of periodic variations of equivalent widths of atmospheric lines in the spectrum of the primary, we have concluded that the surface of the star is spotted. Comparing our result with an earlier one, we argue that these spots can be connected with the infall of material from the disk onto the stellar surface through a magnetosphere. The fourth example is the Herbig Ae/Be star HD37806. Signatures of magnetospheric accretion in this object have been identified using a different method. They were inferred from the short-term variability of the He I l5876 line profile forming in the region of the disk/star interaction. [ABSTRACT FROM AUTHOR]

Large quantities of microplastics end up in the marine environment, constituting a potential threat for many organisms even in remote protected areas where the extent of this type of pollution is still unknown. This study evaluated for the first time the occurrence of microplastics in benthic organisms from the Marine Protected Area Namuncurá at Burdwood Bank, Southwest Atlantic Ocean. Microplastics were isolated from the soft tissue of the sea stars Henricia obesa and Odontaster penicillatus using an oxidative treatment with hydrogen peroxide. The chemical composition of the particles was identified with Raman spectroscopy. Fibers and fragments were found in similar proportions in both species. Fibers were identified as semi-synthetic cellulose, while the polymeric composition of fragments was masked by the synthetic pigment Phthalo blue. Over half of the sea stars contained microplastics (61%). In H. obesa, the mean abundance was 1.00 ± 1.03 particles per individual and 3.34 ± 4.13 particles per gram, and in O. penicillatus, the mean abundance was 2.70 ± 2.91 particles per individual and 1.94 ± 2.09 particles per gram. Fibers were predominantly blue, and all fragments were bluish/turquoise. Microplastic sizes ranged from 24 to 1340 µm, and most particles (approximately 90%) were less than 1 mm. These results provide a baseline assessment of the abundance and type of microplastics in benthic organisms from this sub-Antarctic protected area and contribute to the scant data on microplastic pollution in the South Atlantic Ocean. [ABSTRACT FROM AUTHOR]

For isolated white dwarf (WD) stars, fits to their observed spectra provide the most precise estimates of their effective temperatures and surface gravities. Even so, recent studies have shown that systematic offsets exist between such spectroscopic parameter determinations and those based on broadband photometry. These large discrepancies (10% in Teff, 0.1 M⊙ in mass) provide scientific motivation for reconsidering the atomic physics employed in the model atmospheres of these stars. Recent simulation work of ours suggests that the most important remaining uncertainties in simulation-based calculations of line shapes are the treatment of 1) the electric field distribution and 2) the occupation probability (OP) prescription. We review the work that has been done in these areas and outline possible avenues for progress.

Hydrogen atmosphere white dwarf KUV03442+0719 was first reported as a pulsator by Gianninas et al. in 2006. Follow-up campaigns by Su et al. revealed more periods. Some spectroscopic results suggest that KUV03442+0719 has a slightly below-average mass and an effective temperature of 11,000 K. However, Gaia data (parallax and magnitude) suggest that it may be a low-mass white dwarf. Such an object would have a helium core. We perform asteroseismic fitting of KUV03442+0719, modeling it both as a carbon/oxygen normal mass white dwarf, and a helium-core low-mass white dwarf. To perform the study, we perform a grid search with WDEC models, refined by simplex minimization of the best fits. Both analyses result in best-fit models that are comparable in terms of quality of fit. More pulsation data would be required to allow us to distinguish between the two scenarios. We present and contrast our results with expectations from stellar evolution. We also provide analytic formulae for a temperature-dependent mass–radius relationship for helium-core white dwarfs.

TU Tau (=HD 38218 = HIP 27135) is a binary system consisting of a C-N carbon star primary and an A-type secondary. We report on new photometry and spectroscopy which tracked the recent disappearance of the A-star secondary. The dimming of the A star was gradual and irregular, with one or more brief brightenings, implying the presence of nonhomogeneities in the carbon star outflow. We also present evidence that the A star is actively accreting s -process enriched material from the carbon star and suggest that it will therefore eventually evolve into a Barium giant. This is an important system as well because the A-type star can serve as a probe of the outer atmosphere of the carbon star.

Hot DA white dwarfs (DAWDs) have fully radiative pure hydrogen atmospheres that are the least complicated to model. Pulsationally stable, they are fully characterized by their effective temperature T _eff and surface gravity $\mathrm{log}\,g$ , which can be deduced from their optical spectra and used in model atmospheres to predict their spectral energy distributions (SEDs). Based on this, three bright DAWDs have defined the spectrophotometric flux scale of the CALSPEC system of the Hubble Space Telescope (HST). In this paper we add 32 new fainter (16.5 < V < 19.5) DAWDs spread over the whole sky and within the dynamic range of large telescopes. Using ground-based spectra and panchromatic photometry with HST/WFC3, a new hierarchical analysis process demonstrates consistency between model and observed fluxes above the terrestrial atmosphere to

White dwarfs are excellent research laboratories as they reach temperatures, pressures, and magnetic fields that are unattainable on Earth. To better understand how these three physical parameters interact with each other and with other stellar features, we determined the magnetic field strength for a total of 804 hydrogen-rich white dwarfs (WDs) of which 287 are not in the literature. We fitted the spectra observed with the Sloan Digital Sky Survey using atmospheric models that consider the Zeeman effect due to the magnetic field at each point in the stellar disk. Comparing magnetic and nonmagnetic WDs, the literature already shows that the magnetic ones have on average higher mass than the nonmagnetic. In addition to that, magnetic fields are more common in cooler WDs than in hotter WDs. In consonance, we found that those with higher magnetic field strengths tend to have higher masses, and lower temperatures, for which models indicate the crystallization process has already started. This reinforces the hypothesis that the field is being generated and/or amplified in the cooling process of the white dwarf. Our sample constitutes the largest number of white dwarfs with determined magnetic fields to date.

In the framework of our extensive modeling study of the spectral evolution of white dwarfs, we present here a new set of detailed calculations of the transport of residual hydrogen in helium-rich white dwarfs. First, we investigate the so-called float-up process at high effective temperatures, whereby the upward diffusion of trace hydrogen leads to the formation of a hydrogen atmosphere. We examine the dependence of this phenomenon on the initial hydrogen abundance and on the strength of the radiative wind that opposes gravitational settling. Combined with our empirical knowledge of spectral evolution, our simulations provide new quantitative constraints on the hydrogen content of the hot helium-dominated white dwarf population. Then, we study the outcome of the so-called convective dilution process at low effective temperatures, whereby the superficial hydrogen layer is mixed within the underlying helium-rich envelope. In stark contrast with previous works on convective dilution, we demonstrate that, under reasonable assumptions, our models successfully reproduce the observed atmospheric composition of cool DBA stars, thereby solving one of the most important problems of the theory of spectral evolution. This major improvement is due to our self-consistent modeling of the earlier float-up process, which predicts the existence of a massive hydrogen reservoir underneath the thin superficial layer. We argue that the trace hydrogen detected at the surface of DBA white dwarfs is, in most cases, of primordial origin rather than the result of external accretion.

Sea stars can adhere to various underwater substrata using an adhesive secretion of which Sfp1 is a major component. Sfp1 is a multimodular protein composed of four subunits (Sfp1 Alpha, Beta, Delta, and Gamma) displaying different functional domains. We recombinantly produced two fragments of Sfp1 comprising most of its functional domains: the C-terminal part of the Beta subunit (rSfp1 Beta C-term) and the Delta subunit (rSfp1 Delta). Surface plasmon resonance analyses of protein adsorption onto different model surfaces showed that rSfp1 Beta C-term exhibits a significantly higher adsorption than the fibrinogen control on hydrophobic, hydrophilic protein-resistant, and charged self-assembled monolayers, while rSfp1 Delta adsorbed more on negatively charged and on protein-resistant surfaces compared to fibrinogen. Truncated recombinant rSfp1 Beta C-term proteins were produced in order to investigate the role of the different functional domains in the adsorption of this protein. The analysis of their adsorption capacities on glass showed that two mechanisms are involved in rSfp1 Beta C-term adsorption: (1) one mediated by the EGF-like domain and involving Ca2+ and Mg2+ ions, and (2) one mediated by the sequence of Sfp1 Beta with no homology with known functional domain in databases, in the presence of Na+, Ca2+ and Mg2+ ions. [ABSTRACT FROM AUTHOR]

Since the taxonomic revision of the Ophidiasteridae by H.L. Clark (1921), in which 20 genera were recognized as valid, several new genera and species were included in this family, and the boundaries between some of them became largely arbitrary. This also applies to Narcissia Gray, 1840, whose morphology and taxonomy are still very poorly understood today. The main goals of this research were: review the taxonomy of the genus Narcissia, from morphological studies; redescribe N. trigonaria Sladen, 1889s. str.; characterize N. canariensis (d'Orbigny, 1839) and N. gracilis A.H. Clark, 1916, the two valid species most similar to N. trigonaria; review the validity of N. ahearnae Pawson, 2007 and N. trigonaria var. helenae Mortensen, 1933; review the validity of N. gracilis malpeloensis Downey, 1975. Altogether 370 specimens were analysed. All morphological structures of taxonomic importance have been illustrated, and, for the first time, the internal characters of this group were studied, from electron microscopy and microtomography. A new diagnosis for the genus Narcissia was constructed. Narcissia trigonaria was redescribed from a large specimen, from the type locality (Bahia, Brazil). Narcissia ahearnae is considered a valid species, and N. canariensis and N. trigonaria distinct entities. Narcissia trigonaria var. helenae is placed in the synonymy of N. trigonaria, and N. gracilis malpeloensis into the synonymy of N. gracilis. The dataset obtained in this work is by far the most complete acquired for the genus Narcissia. [ABSTRACT FROM AUTHOR]

Concerned that our observations of cannibalism may be due to the lack of a suitable alternate food source, we then tested the effects of the presence of juvenile blue mussels ( I Mytilus edulis i ) on juvenile sea star cannibalism. Asterias, asteroidea, cannibalism, keystone, predation, recruitment, sea stars, starfish Keywords: Asterias; asteroidea; cannibalism; keystone; predation; recruitment; sea stars; starfish EN Asterias asteroidea cannibalism keystone predation recruitment sea stars starfish 1 4 4 08/05/21 20210801 NES 210801 Cannibalism is widespread across the animal kingdom, occurring in more than 1,300 species of invertebrates and vertebrates across terrestrial and aquatic habitats (Fox 1975, Polis 1981, Elgar and Crespi 1992). Although cannibalism is therefore both predicted and observed to be widespread in nature, we have recently observed cannibalism in an unexpected setting: among newly metamorphosed juvenile sea stars (Fig. [Extracted from the article]

Copyright of Croatian Journal of Ethnology & Folklore Research / Narodna Umjetnost is the property of Institute of Ethnology & Folklore Research and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A new phylogenetic analysis of the superorder Forcipulatacea is presented. Forcipulatacea is one of the three major groups of sea stars (Asteroidea: Echinodermata), composed of 400 extant species. The sampled taxa are thought to represent the morphological diversity of the group. Twenty-nine forcipulate taxa were sampled belonging to Asteriidae, Stichasteridae, Heliasteridae, Pedicellasteridae, Zoroasteridae and Brisingida. Specimens were dissected with bleach. Detailed description of the skeleton and the anatomy of the ossicles were investigated using scanning electron microscopy. Comparative anatomy allowed the scoring of 115 phylogenetically informative characters. The consensus tree resulting from the analysis recovers Asteriidae, Stichasteridae, Zoroasteridae and Brisingida as monophyletic. All types of morphological features contribute to tree resolution and may be appropriate for taxon diagnosis. The synapomorphies supporting different clades are described and discussed. Brisingida and Zoroasteridae are the best-supported clades. The potentially challenging position of Brisingida in the tree may be explained by homoplastic changes, but also by the presence of numerous non-applicable characters. [ABSTRACT FROM AUTHOR]

Reproduction is a highly expensive process that during gonadal development requires an important supply of nutrients. The allocation of energy can vary throughout the reproductive cycle, between sexes and development modes. During research cruise aboard the RV Puerto Deseado in April 2016, we collected fifteen species of sea stars from the southernmost region of Argentina. The main purposes of the present study were threefold: first, to revise and report novel information on the reproductive strategies and energetic density (ED) of body components from the asteroids of the southwestern Atlantic Ocean including Burdwood Bank/ MPA Namuncurá; second, to compare the ED of these body components across species with contrasting reproductive strategies; third, to provide a tool to estimate the ED from dry mass of organs of the sea star species examined. Ovaries of Diplopteraster verrucosus (a brooder with a nidamental chamber) revealed a significantly greater ED than did the testes (29.81 ± 1.38 and 17.76 ± 1.59, respectively). In Glabraster antarctica (a broadcaster with yolky eggs and facultative planktotrophic larvae), the gonads had EDs of 25.78 ± 3.16 and 19.21 ± 0.52 (females and males, respectively). While in Peribolaster folliculatus (a broadcaster with eggs with low yolk content and inferred planktotrophic larvae) there was no significant difference in the ED values between sexes (females: 22.79 ± 1.10 and males: 20.46 ± 1.05). For the pyloric caeca, ED values did not reveal any difference between sexes, although in P. folliculatus, the ED was significantly higher than that for D. verrucosus and G. antarctica (25.90 ± 1.00, 23.03 ± 0.34, and 22.66 ± 0.65, respectively). The body wall had higher ED values in D. verrucosus and P. folliculatus than that for all the sea star species analyzed (46.48 ± 1.63, 51.17 ± 1.34, respectively). Higher ED values in the ovaries could be related to the nutrition of offspring, while differences found in the body wall may reflect the skeletal structure of this body component. This research provides basic information for understanding the differences on energetic allocation when contrasting development modes are considered. [ABSTRACT FROM AUTHOR]

Marine invertebrates are exposed to endocrine disrupting compounds (EDCs) and must utilize defense mechanisms to survive and reproduce; however, little is known about the effects of EDCs on marine invertebrates. Using the sea urchin developmental model, we ascertained that embryos were sensitive at environmentally relevant concentrations to estradiol, ethynylestradiol, 4-octylphenol, tributyltin and o,p-DDD in a stage-specific manner with early embryos being the most sensitive.  Incubation with tamoxifen, a selective estrogen receptor modulator, 'protected' the embryos from estrogenic toxicity suggesting a receptor-mediated mechanism of toxicity.  Estradiol is produced during gastrulation and binds to a low-capacity, low-affinity receptor. Maternal exposure to EDCs altered embryo sensitivity and the expression of mRNA of a steroid receptor in the oocyte in a treatment and dose-dependent manner demonstrating that maternal EDC exposure in invertebrates may directly effect the embryos. A 'first-line-of-defense' mechanism present in many marine invertebrates is the multidrug resistance (MDR) transporter proteins which transport hydrophobic and conjugated compounds out of the cell. In sea stars, MDR transporters are expressed during oogenesis prior to oocyte maturation and an upregulation of MDR transport activity occurs during oocyte maturation. An increase in transport activity occurs during oocyte maturation and involves both permeability  glycoprotein (P-gp) and multidrug resistance-associated (MRP) transporters. The upregulation during maturation is initially due to a translocation of stored proteins to the oocyte cell membrane followed by translation of stored transporter mRNA. Expression of the transporters is not upregulated at fertilization in the sea star but there are changes in expression of the transporters after fertilization and during blastula formation and gastrulation. The inhibition of first cleavage in fertilized eggs by vinblastine is potentiated by specific inhibitors which also reduce first cleavage when used alone. The inhibition of cleavage suggests that MDR transporters may serve an important role in cell mitosis during early development. Several transcripts encoding MRP  transporters were identified using gene sequencing and eDNA macroarray technology including transcripts with homology to vertebrate MRPl, 5 and 8. In conclusion, these data demonstrate that marine invertebrates are sensitive to estrogenic compounds but do utilize defense mechanisms to ensure proper gametogenesis and embryonic development.

Sea stars are a key group of species in benthic marine ecosystems and represent the primary cause of mortality for cultured scallops. In the mariculture grounds of Japanese scallops (Mizuhopecten yessoensis) in north‐eastern Japan, two sea star species, Asterias amurensis (AA) and Distolasterias nipon (DN), are serious predators. However, the predatory impact of these sea stars on scallops remains unquantified, with limited information being available on the biological characteristics of DN. We compared the predatory impact of both sea star species by evaluating their predatory behaviour (i.e. probability of predation and number of captured scallops) on scallops in laboratory experiments. Both sea star species preferred smaller scallops over large ones, with the probability of predation and the number of scallops being preyed on increasing with increasing water temperature. However, DN had a greater predation impact than AA. For instance, the probability of predation by DN was higher, with more scallops being consumed. In particular, compared to AA, DN continuously captured small scallops and fed on larger scallops. Furthermore, the predatory impact of both sea star species (particularly DN) on small scallops peaked at high temperatures. In conclusion, our results present information that could help improve the survival rate of seeded scallops in mariculture systems. [ABSTRACT FROM AUTHOR]

Phase curves, or the change in observed illumination of the planet as it orbits around its host star, help us to characterize their atmospheres. However, the variability of the host star can make their detection challenging. The presence of starspots, faculae, flares, and rotational effects introduce brightness variations that can hide other flux variations related to the presence of an exoplanet: ellipsoidal variation, Doppler boosting, and a combination of reflected light and thermal emission from the planet. Here we present a study to quantify the effect of stellar variability on the detectability of phase curves in the optical. In the first stage we simulated ideal data, with different white noise levels, and with cadences and total duration matching a quarter of the Kepler mission. We performed injection and recovery tests to evaluate the minimum number of planetary orbits that need to be observed in order to determine the amplitude of the phase curve with an accuracy of 15%. We also evaluate the effect of a simplistic stellar variability signal with low amplitude in order to provide strong constraints on the minimum number of orbits needed under these ideal conditions. In the second stage we applied these methods to data from Q9 of the Kepler mission, known for its low instrumental noise. The injection and recovery tests are performed on a selected sample of the less noisy stars in different effective temperature ranges. Even for the shortest explored planet period of 1 day, we find that observing a single orbit of the planet fails to detect accurately more than 90% of the inserted amplitude. The best recovery rates, close to 48%, are obtained after 10 orbits of a 1 day period planet with the largest explored amplitude of 150 ppm. The temperature range of the host stars providing better recovery ratios is 5500 K < Teff < 6000 K. Our results provide guidelines to selecting the best targets in which phase curves can be measured to the greatest accuracy, given the variability and effective temperature of its host star, which is of interest for the upcoming TESS, CHEOPS, and PLATO space missions. [ABSTRACT FROM AUTHOR]

Context. Being the most numerous and oldest stars in the galaxy, M dwarfs are objects of great interest for exoplanet searches. The presence of molecules in their atmosphere complicates our understanding of their atmospheric properties. But great advances have recently been made in the modeling of M dwarfs due to the revision of solar abundances. Aims. We aim to determine stellar parameters of M dwarfs using high resolution spectra (R ∼ 90 000) simultaneously in the visible and the near-infrared. The high resolution spectra and broad wavelength coverage provide an unique opportunity to understand the onset of dust and cloud formation at cool temperatures. Furthermore, this study will help in understanding the physical processes which occur in a cool atmospheres, particularly, the redistribution of energy from the optical to the near-infrared. Methods. The stellar parameters of M dwarfs in our sample have been determined by comparing the high resolution spectra both in the optical and in the near-infrared simultaneously observed by CARMENES with the synthetic spectra obtained from the BT-Settl model atmosphere. The detailed spectral synthesis of these observed spectra both in the optical and in the near-infrared helps to understand the missing continuum opacity. Results. For the first time, we derive fundamental stellar parameters of M dwarfs using the high resolution optical and near-infrared spectra simultaneously. We determine Teff, log g and [M/H] for 292 M dwarfs of spectral type M0 to M9, where the formation of dust and clouds are important. The derived Teff for the sample ranges from 2300 to 4000 K, values of log g ranges from 4.5 ≤ logg ≤ 5.5 and the resulting metallicity ranges from −0.5 ≤ [M/H] ≤ +0.5. We have also explored the possible differences in Teff, log g and [M/H] by comparing them with other studies of the same sample of M dwarfs. [ABSTRACT FROM AUTHOR]

Majorana stars, the antipodal directions associated with the coherent states that are orthogonal to a spin state, provide a visualization and a geometric understanding of the structures of general quantum states. For example, the Berry phase of a spin-1/2 is given by half the solid angle enclosed by the close path of its Majorana star. It is conceivable that the Berry phase of higher spins may also be related to the geometry of the Majorana constellation. We find that for a spin-1 state, besides the expected contributions from the solid angles enclosed by the close paths of the two Majorana stars, the Berry phase includes a term related to the twist of the relative position vector around the barycenter vector of the two Majorana stars, i.e., the self-rotation of the constellation. Interestingly, if the spin-1 state is taken as a symmetrized two-qubit state, the extra contribution to the Berry phase is given by the self-rotation of the Majorana constellation weighted by the quantum entanglement of the two qubits. This discovery alludes to the relevance of the Majorana stellar geometry in representing the deep structures of quantum states and of quantum entanglement.

Absorption cells filled with diatomic iodine are frequently employed as wavelength reference for high-precision stellar radial velocity determination due to their long-term stability and low cost. Despite their wide-spread usage in the community, there is little documentation on how to determine the ideal operating temperature of an individual cell. We have developed a new approach to measuring the effective molecular temperature inside a gas absorption cell and searching for effects detrimental to a high-precision wavelength reference, utilizing the Boltzmann distribution of relative line depths within absorption bands of single vibrational transitions. With a high-resolution Fourier transform spectrometer, we took a series of 632 spectra at temperatures between 23 and 66°C. These spectra provide a sufficient basis to test the algorithm and demonstrate the stability and repeatability of the temperature determination via molecular lines on a single iodine absorption cell. The achievable radial velocity precision σRV is found to be independent of the cell temperature and a detailed analysis shows a wavelength dependence, which originates in the resolving power of the spectrometer in use and the signal-to-noise ratio. Two effects were found to cause apparent absolute shifts in radial velocity, a temperature-induced shift of the order of ∼1 m s−1 K−1 and a more significant effect resulting in abrupt jumps of ≥50 m s−1 is determined to be caused by the temperature crossing the dew point of the molecular iodine. [ABSTRACT FROM AUTHOR]

Although small starfish may exert significant grazing effects on hard substrata, quantification of these effects has been difficult because of methodological limitations. Previously, caging small starfish for field experiments has failed because animals can escape through cage meshes and confounding effects may arise as the starfish can feed on organisms growing on the fences themselves, rather than the surface under investigation. Here, we investigated the efficiency of alternative barrier methods, such as antifouling paint and sticky barriers, for shorter-term experimental manipulation of the herbivorous starfish Parvulastra exigua. Laboratory and field manipulations tested the hypotheses that barriers are efficient in retaining starfish within plots and that the chemical repellent of the barriers does not affect the normal functioning of starfish. The results showed that the sticky barrier did not deter P. exigua, but antifouling paint retained greater numbers of individuals within barrier plots than in controls, with no short-term effects on starfish righting response. [ABSTRACT FROM AUTHOR]

It has been hypothesized that stellar envelopes with positive binding energy may be ejected if the release of recombination energy can be triggered and the calculation of binding energy includes this contribution. The implications of this hypothesis for the evolution of normal hydrogen-rich stars have been investigated, but the implications for helium stars - which may represent mass-transfer or merger remnants in binary star systems-have not. Making a set of model helium stars, we find that those with masses between 0.9 and 2.4M☉ evolve to configurations with positive binding energy envelopes. We discuss consequences of the ejection hypothesis for such stars and possible observational tests of these predictions. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Zoology is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We investigate the masses of 'retired A stars' using asteroseismic detections on seven lowluminosity red-giant and sub-giant stars observed by the NASA Kepler and K2 missions. Our aim is to explore whether masses derived from spectroscopy and isochrone fitting may have been systematically overestimated. Our targets have all previously been subject to longterm radial velocity observations to detect orbiting bodies, and satisfy the criteria used by Johnson et al. to select survey stars which may have had A-type (or early F-type) mainsequence progenitors. The sample actually spans a somewhat wider range in mass, from ≈1 M☉ up to ≈1.7 M☉. Whilst for five of the seven stars the reported discovery mass from spectroscopy exceeds the mass estimated using asteroseismology, there is no strong evidence for a significant, systematic bias across the sample. Moreover, comparisons with other masses from the literature show that the absolute scale of any differences is highly sensitive to the chosen reference literature mass, with the scatter between different literature masses significantly larger than reported error bars. We find that any mass difference can be explained through use of different constraints during the recovery process. We also conclude that underestimated uncertainties on the input parameters can significantly bias the recovered stellar masses, which may have contributed to the controversy on the mass scale for retired A stars. [ABSTRACT FROM AUTHOR]

Little is observationally known about the progenitors of Type Ibc supernovae (SNe) or the typical activity of SNe progenitors in their final years. Here, we analyse deep Large Binocular Telescope imaging data spanning the 4 yr before and after the Type Ibc SN 2012fh using difference imaging. We place 1σ upper limits on the detection of the progenitor star at MU > -3.8, MB > -3.1, MV > -3.8 and MR > -4.0mag. These limits are the tightest placed on a Type Ibc SN to date and they largely rule out single star evolutionary models in favour of a binary channel as the origin of this SN.We also constrain the activity of the progenitor to be small on an absolute scale, with the RMS UBVR optical variability ≲ 2500 L☉ and long-term dimming or brightening trends ≲ 1000 L☉ yr-1 in all four bands. [ABSTRACT FROM AUTHOR]

Coral is an invertebrate animal that acts as a colony of individuals (polyps), for the purpose of reef building. In the case of "hard corals", the polyps aggregate and create a "hard" exoskeleton. This exoskeleton has a symbiotic relationship with zooxanthellae algae that reside with the hard tissues. This symbiosis allows the algae to use the coral's waste for photosynthesis and the coral uses the algal products for maintenance. A delicate relationship that dictates the life history of both organisms. The Crown of Thoms Sea Star (Acanthaster planci) is a predatory sea starfish that feeds on the polyps of most species of coral. The starfish can grow quite large (~ lmeter in diameter) and can consume up to 10 square meters of coral per annum. Although natural predators include the giant triton snail, the titan trigger fish, and several species of pufferfish and shrimp, the starfish is covered in venomous spines, so these predators are not very common. Since the 1960's, periodic population increases/outbreaks of the Crown of Thoms starfish have impacted the Great Barrier Reef ecosystem off the coast of Australia. An outbreak being defined by a population density of greater than 15 starfish per hectare. Starfish populations of this density can result in over 90% of the coral being stripped from the reef. Studies have shown that multiple factors affect the starfish population spikes, the most notable being human overfishing of the starfish predators, and human-induced nutrient spikes. In particular, nutrient spikes lead to more successful starfish larvae which, in turn results in a large number of starfish juveniles reaching maturity. In this StoryMap presentation, a time-series of heatmaps are used to demonstrate the delicate relationship between human activity, starfish population density, and coral distribution. The heatmaps demonstrate that there is a relationship between the anthropogenic activities and population spikes of the starfish and a subsequent decline in the coral reef. Surveys indicate that a healthy reef can recover within a 10 -- 20 year window. However, with increasing frequencies of starfish population spikes along with other environmental stressors, the corals may not be able to recover. [ABSTRACT FROM AUTHOR]