Monthly Notices of the Royal Astronomical Society Letters

Gough, D O

doi: 10.1093/mnrasl/slz044pmid: N/A

Much of our understanding of the internal structure of the Sun derives from so-called standard theoretical solar models. Unfortunately, none of those models agrees completely with observations. The discrepancy is commonly associated with chemical abundance, and has led to what is now called the solar abundance problem, the resolution of which has previously been out of sight. But now the Borexino Collaboration, which recently announced measurements of the pp-chain solar neutrinos, are optimistic that they will be able to measure the flux ΦCNO of the neutrinos emitted by the relatively weak CNO cycle. Since C, N, and O constitute the majority of the heavy elements, that measurement will permit a crucial determination of the heavy-element abundance Zc in the Sun’s energy-generating core, thereby shedding important light on the problem. To accomplish that determination, a robust relation between Zc and ΦCNO will be required. That relation is $Z_{\rm c}= 0.400\, \Phi _{\rm CNO}$, where ΦCNO is in units of 1010 cm−2 s−1.

Wootton, Bethany A; Parker, Richard J

doi: 10.1093/mnrasl/sly238pmid: N/A

ABSTRACTHabitable zones are regions around stars where large bodies of liquid water can be sustained on a planet or satellite. As many stars form in binary systems with non-zero eccentricity, the habitable zones around the component stars of the binary can overlap and be enlarged when the two stars are at periastron (and less often when the stars are at apastron). We perform N-body simulations of the evolution of dense star-forming regions and show that binary systems where the component stars originally have distinct habitable zones can undergo interactions that push the stars closer together, causing the habitable zones to merge and become enlarged. Occasionally, overlapping habitable zones can occur if the component stars move further apart, but the binary becomes more eccentric. Enlargement of habitable zones happens to one to two binaries from an average initial total of 352 in each simulated star-forming region, and demonstrates that dense star-forming regions are not always hostile environments for planet formation and evolution.

Roychowdhury, Sambit; Arabsalmani, Maryam; Kanekar, Nissim

doi: 10.1093/mnrasl/slz035pmid: N/A

We report Giant Metrewave Radio Telescope H i 21 cm imaging of CGCG 137–068, the host galaxy of the fast-evolving luminous transient (FELT) AT2018cow. This is the first study of the gas properties of a FELT host galaxy. We obtain a total H i mass of (6.6 ± 0.9) × 108 M⊙ for the host galaxy, which implies an atomic gas depletion time of 3 Gyr and a gas-to-stellar mass ratio of 0.47, consistent with values in normal star-forming dwarf galaxies. At spatial resolutions of ≥6 kpc, the H i of CGCG 137–068 appears to be distributed in a disc, in mostly regular rotation. However, at spatial resolutions of 2 kpc, the highest column density H i is found to lie in an asymmetric ring around the central regions, with H i column densities ≥1021 cm−2; AT2018cow lies within this high column density ring. This H i ring could be suggestive of an interaction between CGCG 137–068 and a companion galaxy. Such a ring is ideal for the formation of compact regions of star formation hosting massive stars, favouring massive star progenitor models for AT2018cow. We measure a 1.4 GHz flux density of 1.13 ± 0.13 mJy for AT2018cow on 2018 August 27.

Devereux, C; Geach, J E; Hardcastle, M J

doi: 10.1093/mnrasl/slz024pmid: N/A

We present a new measurement of the linear bias of radio-loud active galactic nuclei (RLAGNs) at $z$ ≈ 0.3 and $L_{\rm 1.4GHz}\gt 10^{23}\, {\rm W\, Hz^{-1}}$ selected from the Best & Heckman (2012) sample, made by cross-correlating the RLAGN surface density with a map of the convergence of the weak lensing field of the cosmic microwave background from Planck. We detect the cross-power signal at a significance of 3σ and use the amplitude of the cross-power spectrum to estimate the linear bias of RLAGNs, b = 2.5 ± 0.8, corresponding to a typical dark matter halo mass of $\log _{10}(M_{\rm h} /h^{-1} M_\odot)=14.0^{+0.3}_{-0.5}$. When RLAGNs associated with optically selected clusters are removed we measure a lower bias corresponding to $\log _{10}(M_{\rm h} /h^{-1} M_\odot)=13.7^{+0.4}_{-1.0}$. These observations support the view that powerful RLAGNs typically inhabit rich group and cluster environments.

Menou, Kristen

doi: 10.1093/mnrasl/slz041pmid: N/A

Turbulent vertical transport driven by double-diffusive shear instabilities is identified as likely important in hot exoplanet atmospheres. In hot Jupiter atmospheres, the resulting vertical mixing appears sufficient to alleviate the nightside cold trap, thus facilitating the maintenance of nocturnal clouds on these planets. The strong level of vertical mixing expected near hot Jupiter thermal photospheres will impact their atmospheric chemistry and even their vertical structures where cloud radiative feedback proves important.

Hess, P O; Boller, Th; Müller, A; Stöcker, H

doi: 10.1093/mnrasl/slz040pmid: N/A

We present a resumé on the modified theory of gravity, called pseudo-complex General Relativity (pc-GR). It is the second in a series of papers, where the first one (Boller et al. 2019; referred to as Paper I) discussed the observational consequences of pc-GR. In this paper, we concentrate on the underlying theory. PC-GR involves an algebraic extension of the standard theory of GR and it depends on two phenomenological parameters. An element included in pc-GR that is not present in standard GR is the energy–momentum tensor corresponding to an anisotropic ideal fluid, which we call dark energy. The two parameters are related to the coupling of mass to the dark energy and its fall-off as a function of r. The consequences and predictions of this theory will be discussed in the context of the observational results of the Even Horizon Telescope, expected soon. Our main result is that due to the accumulation of dark energy near a large mass, the modified theory predicts a dark ring followed by a bright ring in the emission profile of the accretion disc. We also discuss the light ring in the equatorial plane.

Jackman, James A G; Wheatley, Peter J; Bayliss, Daniel; Burleigh, Matthew R; Casewell, Sarah L; Eigmüller, Philipp; Goad, Mike R; Pollacco, Don; Raynard, Liam; Watson, Christopher A; West, Richard G

doi: 10.1093/mnrasl/slz039pmid: N/A

We present the detection of a ΔV ∼ −10 flare from the ultracool L2.5 dwarf ULAS J224940.13−011236.9 with the Next Generation Transit Survey (NGTS). The flare was detected in a targeted search of late-type stars in NGTS full-frame images and represents one of the largest flares ever observed from an ultracool dwarf. This flare also extends the detection of white-light flares to stars with temperatures below 2000 K. We calculate the energy of the flare to be $3.4^{+0.9}_{-0.7}\times 10^{33}$ erg, making it an order of magnitude more energetic than the Carrington event on the Sun. Our data show how the high-cadence NGTS full-frame images can be used to probe white-light flaring behaviour in the latest spectral types.

Zampieri, Luca; Burtovoi, Aleksandr; Fiori, Michele; Naletto, Giampiero; Spolon, Alessia; Barbieri, Cesare; Papitto, Alessandro; Ambrosino, Filippo

doi: 10.1093/mnrasl/slz043pmid: N/A

We report the first detection of an optical millisecond pulsar with the fast photon counter Aqueye+ in Asiago. This is an independent confirmation of the detection of millisecond pulsations from PSR J1023+0038 obtained with SiFAP at the Telescopio Nazionale Galileo. We observed the transitional millisecond pulsar PSR J1023+0038 with Aqueye+ mounted at the Copernicus telescope in 2018 January. Highly significant pulsations were detected. The rotational period is in agreement with the value extrapolated from the X-ray ephemeris, while the time of passage at the ascending node is shifted by 11.55 ± 0.08 s from the value predicted using the orbital period from the X-rays. An independent optical timing solution is derived over a baseline of a few days that has an accuracy of ∼0.007 in pulse phase (∼12 μs in time). This level of precision is needed to derive an accurate coherent timing solution for the pulsar and to search for possible phase shifts between the optical and X-ray pulses using future simultaneous X-ray and optical observations.

Martinez-Medina, Luis; Pichardo, Barbara; Peimbert, Antonio; Valenzuela, Octavio

doi: 10.1093/mnrasl/slz042pmid: N/A

Recently, the Gaiadata release 2 (DR2) showed us the richness in the kinematics of the Milky Way disc. Of particular interest is the presence of ridges covering the stellar velocity distribution, Vϕ–R; as shown by others, it is likely that these ridges are the signature of phase mixing, transient spirals, or the bar. Here, with a Galactic model containing both, bar and spirals, we found the same pattern of ridges extending from the inner to the outer disc. Interestingly, ridges in the Vϕ–R plane correlate extremely well with wiggles in the computed rotation curve (RC). Hence, although the DR2 reveals (for the first time) such substructures in a wide spatial coverage, we notice that we have always seen such a pattern of ridges, but projected into the form of wiggles in the RC. The separation and amplitude of the wiggles strongly depend on the extension and layout of ridges in the Vϕ–R plane. This means that within the RC are encoded the kinematic state of the disc and information about the bar and spiral arms. The amplitude of the wiggles suggests that similar features currently observable in external galaxies' RCs have similar origins, triggered by spirals and bars.

Vedantham, H K; Ravi, V

doi: 10.1093/mnrasl/slz038pmid: N/A

ABSTRACTThe extreme, time-variable Faraday rotation observed in the repeating fast radio burst (FRB) 121102 and its associated persistent synchrotron source demonstrates that some FRBs originate in dense, dynamic, and possibly relativistic magneto-ionic environments. Besides rotation of the linear polarization vector (Faraday rotation), such media can generally convert linear to circular polarization (Faraday conversion). We use non-detection of Faraday conversion, and the temporal variation in Faraday rotation and dispersion in bursts from FRB 121102 to constrain models where the progenitor inflates a relativistic nebula (persistent source) confined by a cold dense medium (e.g. supernova ejecta). We find that the persistent synchrotron source, if composed of an electron–proton plasma, must be an admixture of relativistic and non-relativistic (Lorentz factor γ < 5) electrons. Furthermore, we independently constrain the magnetic field in the cold confining medium, which provides the Faraday rotation, to be between 10 and 30 mG. This value is close to the equipartition magnetic field of the confined persistent source implying a self-consistent and overconstrained model that can explain the observations.