Evidence for inflows and outflows in the nearby black hole transient Swift J1727.8-162

We present 20 epochs of optical spectroscopy obtained with the GTC-10.4m telescope across the bright discovery outburst of the black hole candidate Swift J1727.8-162. The spectra cover the main accretion states and are characterised by the presence of hydrogen and helium emission lines, commonly observed in these objects. They show complex profiles, including double-peaks, but also blue-shifted absorptions (with blue-edge velocities of 1150 km/s), broad emission wings and flat-top profiles, which are usual signatures of accretion disc winds. Moreover, red-shifted absorptions accompanied by blue emission excesses suggest the presence of inflows in at least two epochs, although a disc origin cannot be ruled out. Using pre-outburst imaging from Pan-STARRS, we identify a candidate quiescent optical counterpart with a magnitude of g = 20.8. This implies an outburst optical amplitude of DV = 7.7, supporting an estimated orbital period of 7.6 h, which favours an early K-type companion star. Employing various empirical methods we derive a distance to the source of d = 2.7 +- 0.3 kpc, corresponding to a Galactic Plane elevation of z = 0.48 +- 0.05 kpc. Based on these findings, we propose that Swift J1727.8-162 is a nearby black hole X-ray transient that exhibited complex signatures of optical inflows and outflows throughout its discovery outburst.Comment: 4 Figures, 1 table. Appendix with 1 table. Accepted for publication in A&A Letters. Two typos in section 4.3 have been amended in the latest ArXiv version. Ar/AV =2.271 should be instead Ar/E(B-V) = 2.271. The Porb units in the equation should be in days (as in the original paper, Casares 2018). Neither of these actually affect any of the results of the pape

A study of the galaxy redshift distribution toward the cosmic microwave background cold spot in the Corona Borealis supercluster

We present a study of the spatial and redshift distributions of Sloan Digital Sky Survey (SDSS) galaxies toward the position of CrB-H, a very deep and extended decrement in the Cosmic Microwave Background (CMB), located within the Corona Borealis supercluster (CrB-SC). It was found in a survey with the Very Small Array (VSA) interferometer at 33 GHz, with a peak negative brightness temperature of -230 muK, and deviates 4.4-sigma from the Gaussian CMB (G\'enova-Santos et al.). Observations with the Millimeter and Infrared Testa Grigia Observatory (MITO) suggested that 25$^+21_-18% of this decrement may be caused by the thermal Sunyaev-Zel'dovich (tSZ) effect (Battistelli et al.). Here we investigate whether the galaxy distribution could be tracing either a previously unnoticed galaxy cluster or a Warm/Hot Intergalactic Medium (WHIM) filament that could build up this tSZ effect. We find that the projected density of galaxies outside Abell clusters and with redshifts 0.05<z<0.12 at the position of CrB-H is the highest in the area encompassed by the CrB-SC. Most of these galaxies are located around redshifts z=0.07 and z=0.11, but no clear connection in the form of a filamentary structure is appreciable in between. While the galaxy distribution at z=0.07 is sparse, we find evidence at z=0.11 of a galaxy group or a low-mass galaxy cluster. We estimate that this structure could produce a tSZ effect of ~ -18 muK. The remaining VSA signal of ~ -212 muK is still a significant 4.1-sigma deviation from the Gaussian CMB. However, the MITO error bar allows for a larger tSZ effect, which could be produced by galaxy clusters or superclusters beyond the sensitivity of the SDSS. Contributions from other possible secondary anisotropies associated with these structures are also discussed.Comment: 11 pages, 5 figures, 3 tables. Accepted in MNRA

Functional studies of signaling pathways in peri-implantation development of the mouse embryo by RNAi

BACKGROUND: Studies of gene function in the mouse have relied mainly on gene targeting via homologous recombination. However, this approach is difficult to apply in specific windows of time, and to simultaneously knock-down multiple genes. Here we report an efficient method for dsRNA-mediated gene silencing in late cleavage-stage mouse embryos that permits examination of phenotypes at post-implantation stages. RESULTS: We show that introduction of Bmp4 dsRNA into intact blastocysts by electroporation recapitulates the genetic Bmp4 null phenotype at gastrulation. It also reveals a novel role for Bmp4 in the regulation the anterior visceral endoderm specific gene expression and its positioning. We also show that RNAi can be used to simultaneously target several genes. When applied to the three murine isoforms of Dishevelled, it leads to earlier defects than previously observed in double knock-outs. These include severe delays in post-implantation development and defects in the anterior midline and neural folds at headfold stages. CONCLUSION: Our results indicate that the BMP4 signalling pathway contributes to the development of the anterior visceral endoderm, and reveal an early functional redundancy between the products of the murine Dishevelled genes. The proposed approach constitutes a powerful tool to screen the functions of genes that govern the development of the mouse embryo

Too dense to go through: The importance of low-mass clusters for satellite quenching

We study the evolution of satellite galaxies in clusters of the C-EAGLE simulations, a suite of 30 high-resolution cosmological hydrodynamical zoom-in simulations based on the EAGLE code. We find that the majority of galaxies that are quenched at $z=0$ ($\gtrsim$ 80$\%$) reached this state in a dense environment (log$_{10}$M$_{200}$[M$_{\odot}$]$\geq$13.5). At low redshift, regardless of the final cluster mass, galaxies appear to reach their quenching state in low mass clusters. Moreover, galaxies quenched inside the cluster that they reside in at $z=0$ are the dominant population in low-mass clusters, while galaxies quenched in a different halo dominate in the most massive clusters. When looking at clusters at $z>0.5$, their in-situ quenched population dominates at all cluster masses. This suggests that galaxies are quenched inside the first cluster they fall into. After galaxies cross the cluster's $r_{200}$ they rapidly become quenched ($\lesssim$ 1Gyr). Just a small fraction of galaxies ($\lesssim 15\%$) is capable of retaining their gas for a longer period of time, but after 4Gyr, almost all galaxies are quenched. This phenomenon is related to ram pressure stripping and is produced when the density of the intracluster medium reaches a threshold of $\rho_{\rm ICM}$ $\sim 3 \times 10 ^{-5}$ n$_{\rm H}$ (cm$^{-3}$). These results suggest that galaxies start a rapid-quenching phase shortly after their first infall inside $r_{200}$ and that, by the time they reach $r_{500}$, most of them are already quenched.Comment: 14 pages, 8 figures, Submitted to MNRA

Evidence for a black hole in the historical X-ray transient A 1524-61 (=KY TrA)

We present VLT spectroscopy, high-resolution imaging and time-resolved photometry of KY TrA, the optical counterpart to the X-ray binary A 1524-61. We perform a refined astrometry of the field, yielding improved coordinates for KY TrA and the field star interloper of similar optical brightness that we locate $0.64 \pm 0.04$ arcsec SE. From the spectroscopy, we refine the radial velocity semi-amplitude of the donor star to $K_2 = 501 \pm 52$ km s$^{-1}$ by employing the correlation between this parameter and the full-width at half-maximum of the H$\alpha$ emission line. The $r$-band light curve shows an ellipsoidal-like modulation with a likely orbital period of $0.26 \pm 0.01$ d ($6.24 \pm 0.24$ h). These numbers imply a mass function $f(M_1) = 3.2 \pm 1.0$ M$_\odot$. The KY TrA de-reddened quiescent colour $(r-i)_0 = 0.27 \pm 0.08$ is consistent with a donor star of spectral type K2 or later, in case of significant accretion disc light contribution to the optical continuum. The colour allows us to place a very conservative upper limit on the companion star mass, $M_2 \leq 0.94$ M$_\odot$, and, in turn, on the binary mass ratio, $q = M_2/M_1 \leq 0.31$. By exploiting the correlation between the binary inclination and the depth of the H$\alpha$ line trough, we establish $i = 57 \pm 13$ deg. All these values lead to a compact object and donor mass of $M_1 = 5.8^{+3.0}_{-2.4}$ M$_\odot$ and $M_2 = 0.5 \pm 0.3$ M$_\odot$, respectively, thus confirming the black hole nature of the accreting object. In addition, we estimate a distance toward the system of $8.0 \pm 0.9$ kpc.Comment: 7 pages, 5 figure

Genes Dev

Almost half of our genome is occupied by transposable elements. Although most of them are inactive, one type of non-long terminal repeat (LTR) retrotransposon, long interspersed nuclear element 1 (LINE1), is capable of retrotransposition. Two studies in this issue, Pezic and colleagues (pp. 1410-1428) and Castro-Diaz and colleagues (pp. 1397-1409), provide novel insight into the regulation of LINE1s in human embryonic stem cells and mouse germ cells and shed new light on the conservation of complex mechanisms to ensure silencing of transposable elements in mammals

The binary mass ratio in the black hole transient MAXI J1820+070

We present intermediate resolution spectroscopy of the optical counterpart to the black hole X-ray transient MAXI J1820+070 (=ASASSN-18ey) obtained with the OSIRIS spectrograph on the 10.4-m Gran Telescopio Canarias. The observations were performed with the source close to the quiescent state and before the onset of renewed activity in August 2019. We make use of these data and K-type dwarf templates taken with the same instrumental configuration to measure the projected rotational velocity of the donor star. We find $v_{rot} \sin i = 84 \pm 5$ km s$^{-1}$ ($1\!-\!\sigma$), which implies a donor to black-hole mass ratio $q = {M_2}/{M_1} = 0.072 \pm 0.012$ for the case of a tidally locked and Roche-lobe filling donor star. The derived dynamical masses for the stellar components are $M_1 = (5.95 \pm 0.22)\sin ^{-3}i$ $M_\odot$ and $M_2 = (0.43 \pm 0.08) \sin^{-3}i$ $M_\odot$. The use of $q$, combined with estimates of the accretion disk size at the time of the optical spectroscopy, allows us to revise our previous orbital inclination constraints to $66^{\circ} < i < 81^{\circ}$. These values lead to 95% confidence level limits on the masses of $5.73 <M_1(M_\odot) < 8.34$ and $0.28 < M_2(M_\odot) < 0.77$. Adopting instead the $63 \pm 3^{\circ}$ orientation angle of the radio jet as the binary inclination leads to $M_1 = 8.48^{+0.79}_{-0.72} M_\odot$ and $M_2 = 0.61^{+0.13}_{-0.12} M_\odot$ ($1\!-\!\sigma$).Comment: 8 pages, 2 figures. Accepted for publication in ApJ