The Zwicky Transient Facility (ZTF) is performing a three-day cadence survey of the visible northern sky (∼3π) with newly found transient candidates announced via public alerts. The ZTF Bright ...Transient Survey (BTS) is a large spectroscopic campaign to complement the photometric survey. BTS endeavors to spectroscopically classify all extragalactic transients with mpeak ≤ 18.5 mag in either the gZTF or rZTF filters, and publicly announce said classifications. BTS discoveries are predominantly supernovae (SNe), making this the largest flux-limited SN survey to date. Here we present a catalog of 761 SNe, classified during the first nine months of ZTF (2018 April 1-2018 December 31). We report BTS SN redshifts from SN template matching and spectroscopic host-galaxy redshifts when available. We analyze the redshift completeness of local galaxy catalogs, the redshift completeness fraction (RCF; the ratio of SN host galaxies with known spectroscopic redshift prior to SN discovery to the total number of SN hosts). Of the 512 host galaxies with SNe Ia, 227 had previously known spectroscopic redshifts, yielding an RCF estimate of 44% 4%. The RCF decreases with increasing distance and decreasing galaxy luminosity (for z < 0.05, or ∼200 Mpc, RCF 0.6). Prospects for dramatically increasing the RCF are limited to new multifiber spectroscopic instruments or wide-field narrowband surveys. Existing galaxy redshift catalogs are only ∼50% complete at r 16.9 mag. Pushing this limit several magnitudes deeper will pay huge dividends when searching for electromagnetic counterparts to gravitational wave events or sources of ultra-high-energy cosmic rays or neutrinos.
While it is clear that Type Ia supernovae (SNe) are the result of thermonuclear explosions in C/O white dwarfs (WDs), a great deal remains uncertain about the binary companion that facilitates the ...explosive disruption of the WD. Here, we present a comprehensive analysis of a large, unique data set of 127 SNe Ia with exquisite coverage by the Zwicky Transient Facility (ZTF). High-cadence (six observations per night) ZTF observations allow us to measure the SN rise time and examine its initial evolution. We develop a Bayesian framework to model the early rise as a power law in time, which enables the inclusion of priors in our model. For a volume-limited subset of normal SNe Ia, we find that the mean power-law index is consistent with 2 in the rZTF-band ( ), as expected in the expanding fireball model. There are, however, individual SNe that are clearly inconsistent with . We estimate a mean rise time of 18.9 days (with a range extending from ∼15 to 22 days), though this is subject to the adopted prior. We identify an important, previously unknown, bias whereby the rise times for higher-redshift SNe within a flux-limited survey are systematically underestimated. This effect can be partially alleviated if the power-law index is fixed to = 2, in which case we estimate a mean rise time of 21.7 days (with a range from ∼18 to 23 days). The sample includes a handful of rare and peculiar SNe Ia. Finally, we conclude with a discussion of lessons learned from the ZTF sample that can eventually be applied to observations from the Vera C. Rubin Observatory.
The final fate of massive stars, and the nature of the compact remnants they leave behind (black holes and neutron stars), are open questions in astrophysics. Many massive stars are stripped of their ...outer hydrogen envelopes as they evolve. Such Wolf-Rayet stars
emit strong and rapidly expanding winds with speeds greater than 1,000 kilometres per second. A fraction of this population is also helium-depleted, with spectra dominated by highly ionized emission lines of carbon and oxygen (types WC/WO). Evidence indicates that the most commonly observed supernova explosions that lack hydrogen and helium (types Ib/Ic) cannot result from massive WC/WO stars
, leading some to suggest that most such stars collapse directly into black holes without a visible supernova explosion
. Here we report observations of SN 2019hgp, beginning about a day after the explosion. Its short rise time and rapid decline place it among an emerging population of rapidly evolving transients
. Spectroscopy reveals a rich set of emission lines indicating that the explosion occurred within a nebula composed of carbon, oxygen and neon. Narrow absorption features show that this material is expanding at high velocities (greater than 1,500 kilometres per second), requiring a compact progenitor. Our observations are consistent with an explosion of a massive WC/WO star, and suggest that massive Wolf-Rayet stars may be the progenitors of some rapidly evolving transients.
The vascular adventitia acts as a biological processing center for the retrieval, integration, storage, and release of key regulators of vessel wall function. It is the most complex compartment of ...the vessel wall and is composed of a variety of cells, including fibroblasts, immunomodulatory cells (dendritic cells and macrophages), progenitor cells, vasa vasorum endothelial cells and pericytes, and adrenergic nerves. In response to vascular stress or injury, resident adventitial cells are often the first to be activated and reprogrammed to influence the tone and structure of the vessel wall; to initiate and perpetuate chronic vascular inflammation; and to stimulate expansion of the vasa vasorum, which can act as a conduit for continued inflammatory and progenitor cell delivery to the vessel wall. This review presents the current evidence demonstrating that the adventitia acts as a key regulator of vascular wall function and structure from the outside in.
Topographically complex regions on land and in the oceans feature hotspots of biodiversity that reflect geological influences on ecological and evolutionary processes. Over geologic time, topographic ...diversity gradients wax and wane over millions of years, tracking tectonic or climatic history. Topographic diversity gradients from the present day and the past can result from the generation of species by vicariance or from the accumulation of species from dispersal into a region with strong environmental gradients. Biological and geological approaches must be integrated to test alternative models of diversification along topographic gradients. Reciprocal illumination among phylogenetic, phylogeographic, ecological, paleontological, tectonic, and climatic perspectives is an emerging frontier of biogeographic research.
Topographically complex regions today feature high taxonomic and ecological diversity.
Ancient topographic diversity gradients arose and declined over millions of years.
Paleontological and modern data are crucial to understand topographic diversity gradients.
Topographically complex regions have high conservation value.
ABSTRACT
AM CVn systems are ultra-compact, hydrogen-depleted, and helium-rich, accreting binaries with degenerate or semidegenerate donors. We report the discovery of five new eclipsing AM CVn ...systems with orbital periods of 61.5, 55.5, 53.3, 37.4, and 35.4 min. These systems were discovered by searching for deep eclipses in the Zwicky Transient Facility (ZTF) light curves of white dwarfs selected using Gaia parallaxes. We obtained phase-resolved spectroscopy to confirm that all systems are AM CVn binaries, and we obtained high-speed photometry to confirm the eclipse and characterize the systems. The spectra show double-peaked H e lines but also show metals, including K and Zn, elements that have never been detected in AM CVn systems before. By modelling the high-speed photometry, we measured the mass and radius of the donor star, potentially constraining the evolutionary channel that formed these AM CVn systems. We determined that the average mass of the accreting white dwarf is ≈0.8 M⊙, and that the white dwarfs in long-period systems are hotter than predicted by recently updated theoretical models. The donors have a high entropy and are a factor of ≈2 more massive compared to zero-entropy donors at the same orbital period. The large donor radius is most consistent with H e-star progenitors, although the observed spectral features seem to contradict this. The discovery of five new eclipsing AM CVn systems is consistent with the known observed AM CVn space density and estimated ZTF recovery efficiency.
The age of lineages has become a fundamental datum in studies exploring the interaction between geological transformation and biotic diversification. However, phylogeographical studies are often ...biased towards lineages that are younger than the geological features of the landscapes they inhabit. A temporally deeper historical biogeography framework may be required to address episodes of biotic diversification associated with geologically older landscape changes. Signatures of such associations may be retained in the genomes of ecologically specialized (stenotopic) taxa with limited vagility. In the study presented here, genetic data from montane scorpions in the Vaejovis vorhiesi group, restricted to humid rocky habitats in mountains across southwestern North America, were used to explore the relationship between scorpion diversification and regional geological history.
Strong phylogeographical signal was evident within the vorhiesi group, with 27 geographically cohesive lineages inferred from a mitochondrial phylogeny. A time-calibrated multilocus species tree revealed a pattern of Miocene and Pliocene (the Neogene period) lineage diversification. An estimated 21 out of 26 cladogenetic events probably occurred prior to the onset of the Pleistocene, 2.6 million years ago. The best-fit density-dependent model suggested diversification rate in the vorhiesi group gradually decreased through time.
Scorpions of the vorhiesi group have had a long history in the highlands of southwestern North America. Diversification among these stenotopic scorpions appears to have occurred almost entirely within the Neogene period, and is temporally consistent with the dynamic geological history of the Basin and Range, and Colorado Plateau physiographical provinces. The persistence of separate lineages at small spatial scales suggests that a combination of ecological stenotopy and limited vagility may make these scorpions particularly valuable indicators of geomorphological evolution.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract We have discovered that the H α emission-line star Haro 5-2, located in the 3–6 Myr old Ori OB1b association, is a young quadruple system. The system has a 2+2 configuration, with an outer ...separation of 2.″6 and with resolved subarcsecond inner binary components. The brightest component, Aa, dominates the A-binary; it is a weak-line T Tauri star with spectral type M2.5±1. The two stars of the B component are equally bright at J , but the Bb star is much redder. Optical spectroscopy of the combined B pair indicates a rich emission-line spectrum with a M3±1 spectral type. The spectrum is highly variable and switches back and forth between a classical and a weak-line T Tauri star. In the near-IR, the spectrum shows Paschen β and Brackett γ in emission, indicative of active accretion. A significant mid-IR excess reveals the presence of circumstellar or circumbinary material in the system. Most multiple systems are likely formed during the protostellar phase, involving flybys of neighboring stars followed by an inspiraling phase driven by accretion from circumbinary material and leading to compact subsystems. However, Haro 5-2 stands out among young 2+2 quadruples, as the two inner binaries are unusually wide relative to the separation of the A and B pair, allowing future studies of the individual components. Assuming the components are coeval, the system could potentially allow stringent tests of pre-main-sequence evolutionary models.
Helium is expected to be present in the massive ejecta of some hydrogen-poor superluminous supernovae (SLSN-I). However, until now only one event has been identified with He features in its ...photospheric spectra (PTF10hgi). We present the discovery of a new He-rich SLSN-I, ZTF19aawfbtg (SN2019hge), at z = 0.0866. This event has more than 10 optical spectra at phases from −41 to +103 days relative to the peak, most of which match well with that of PTF10hgi. Confirmation comes from a near-IR spectrum taken at +34 days, revealing He i features with P-Cygni profiles at 1.083 and 2.058 m. Using the optical spectra of PTF10hgi and SN2019hge as templates, we examined 70 other SLSNe-I discovered by Zwicky Transient Facility in the first two years of operation and found five additional SLSNe-I with distinct He-features. The excitation of He i atoms in normal core-collapse supernovae requires nonthermal radiation, as proposed by previous studies. These He-rich events cannot be explained by the traditional 56Ni mixing model because of their blue spectra, high peak luminosities, and long rise timescales. Magnetar models offer a possible solution since pulsar winds naturally generate high-energy particles, potential sources of nonthermal excitation. An alternative model is the interaction between the ejecta and dense H-poor circumstellar material, which may be supported by observed undulations in the light curves. These six SLSNe-Ib have relatively low-peak luminosities (rest frame Mg = −20.06 0.16).
Macrophage accumulation is not only a characteristic hallmark but is also a critical component of pulmonary artery remodeling associated with pulmonary hypertension (PH). However, the cellular and ...molecular mechanisms that drive vascular macrophage activation and their functional phenotype remain poorly defined. Using multiple levels of in vivo (bovine and rat models of hypoxia-induced PH, together with human tissue samples) and in vitro (primary mouse, rat, and bovine macrophages, human monocytes, and primary human and bovine fibroblasts) approaches, we observed that adventitial fibroblasts derived from hypertensive pulmonary arteries (bovine and human) regulate macrophage activation. These fibroblasts activate macrophages through paracrine IL-6 and STAT3, HIF1, and C/EBPβ signaling to drive expression of genes previously implicated in chronic inflammation, tissue remodeling, and PH. This distinct fibroblast-activated macrophage phenotype was independent of IL-4/IL-13-STAT6 and TLR-MyD88 signaling. We found that genetic STAT3 haplodeficiency in macrophages attenuated macrophage activation, complete STAT3 deficiency increased macrophage activation through compensatory upregulation of STAT1 signaling, and deficiency in C/EBPβ or HIF1 attenuated fibroblast-driven macrophage activation. These findings challenge the current paradigm of IL-4/IL-13-STAT6-mediated alternative macrophage activation as the sole driver of vascular remodeling in PH, and uncover a cross-talk between adventitial fibroblasts and macrophages in which paracrine IL-6-activated STAT3, HIF1α, and C/EBPβ signaling are critical for macrophage activation and polarization. Thus, targeting IL-6 signaling in macrophages by completely inhibiting C/EBPβ or HIF1α or by partially inhibiting STAT3 may hold therapeutic value for treatment of PH and other inflammatory conditions characterized by increased IL-6 and absent IL-4/IL-13 signaling.
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