Monthly Notices of the Royal Astronomical Society Letters

Flekkøy, Eirik Grude; Toussaint, Renaud

doi: 10.1093/mnrasl/slad049pmid: N/A

ABSTRACTWe obtain the exact statistical distribution of expected detection rates that may be obtained from the detection of ‘Oumuamua, which currently belongs to a class of objects that is only observed once in our Solar system. The derivation of the distribution of future detection rates starts from the assumption that the detection is a result of a Poisson process, and uses Bayes theorem along with information theory to get the result. We derive the probability for the next such observation along with the confidence limits of this prediction assuming that observations are done with the forthcoming Vera C. Rubin Observatory. This probability depends on the estimates of detection rates that existed prior to the ‘Oumuamua observation. However, unless the constraints given by these model-based estimates are within an order of magnitude of the actual detection rate, they have a negligible effect on the probability of making a second observation. The results are generalized to the expected future case where more than one observation exists.

Klitsch, Anne; Davis, Timothy A; Hamanowicz, Aleksandra; van de Voort, Freeke; Péroux, Céline; Zwaan, Martin A

doi: 10.1093/mnrasl/slad053pmid: N/A

ABSTRACTDespite its crucial role in galaxy evolution, the complex circumgalactic medium (CGM) remains underexplored. Although, it is known to be multiphase, the importance of the molecular gas phase to the total CGM mass budget is, to date, unconstrained. We present the first constraints on the molecular gas covering fraction in the CGM of low-redshift galaxies, using measurements of CO column densities along sightlines towards mm-bright background quasars with intervening galaxies. We do not detect molecular absorption against the background quasars. For the individual, low-redshift, ‘normal’ galaxy haloes probed here, we can therefore rule out the presence of an extremely molecular gas-rich CGM, as recently reported in high-redshift protoclusters and around luminous active galactic nuclei. We also set statistical limits on the volume filling factor of molecular material in the CGM as a whole, and as a function of radius. Interstellar medium-like molecular clouds of ∼30 pc in radius with column densities of N(CO) ≳ 1016 cm−2 have volume filling factors of <0.2 per cent. Large-scale smooth gas reservoirs are ruled out much more stringently. The development of this technique in the future will allow deeper constraining limits to be set on the importance (or unimportance) of molecular gas in the CGM.

Dattatrey, Arvind K; Yadav, R K S; Kumawat, Gourav; Rani, Sharmila; Singh, Gaurav; Subramaniam, Annapurni; Singh, Ravi S

doi: 10.1093/mnrasl/slad059pmid: N/A

ABSTRACTWe report the discovery of four blue lurkers with low- and extremely low mass white dwarf (ELM WD) companions in the Galactic globular cluster NGC 362 using AstroSat’s Ultra Violet Imaging Telescope (UVIT). We analysed the multiwavelength spectral energy distribution (SED) of far-ultraviolet-bright main-sequence stars using data from the UVIT, Ultraviolet Optical Telescope, Gaia EDR3, and 2.2-m ESO/MPI telescopes. Two each of low-mass WDs and ELM WDs are found as companions for the four blue lurkers by the fitting of two-component SED models. The effective temperatures, radii, luminosities, and masses of two low-mass WDs are (35 000, 23 000) K, (0.04, 0.05) R⊙, (1.45, 0.22) L⊙, and (0.2, 0.2) M⊙, while the two ELM WDs are (14 750, 14 750) K, (0.09, 0.10) R⊙, (0.34, 0.40) L⊙, and (0.18, 0.18) M⊙, respectively. The position of blue lurkers within the cluster shows that they originated via the Case A/B mass-transfer mechanism in a low-density environment. This is the first detection of blue lurkers with low-mass WDs and ELM WDs as companions in a globular cluster. The companion’s cooling age is less than 4 Myr, which suggests that they were just recently formed. These binary systems might have originated due to the cluster’s recent core collapse.

Quirino, Diogo; Gilli, Gabriella; Kaltenegger, Lisa; Navarro, Thomas; Fauchez, Thomas J; Turbet, Martin; Leconte, Jérémy; Lebonnois, Sébastien; González-Galindo, Francisco

doi: 10.1093/mnrasl/slad045pmid: N/A

ABSTRACTThe recently discovered super-Earth LP 890-9 c is an intriguing target for atmospheric studies as it transits a nearby, low-activity late-type M-dwarf star at the inner edge of the Habitable Zone. Its position at the runaway greenhouse limit makes it a natural laboratory to study the climate evolution of hot rocky planets. We present the first 3D-Global Climate Model exo-Venus model for a modern Venus-like atmosphere (92 bar surface pressure, realistic composition, and H2SO4 radiatively-active clouds), applied to the tidally-locked LP 890-9 c to inform observations by JWST and future instruments. If LP 890-9 c has developed into a modern exo-Venus, then the modelled temperatures suggest that H2SO4 clouds are possible even in the substellar region. Like on modern Venus, clouds on LP 890-9 c would create a flat spectrum. The strongest CO2 bands in transmission predicted by our model for LP 890-9 c are about 10 ppm, challenging detection, given JWST estimated noise floor. Estimated phase curve amplitudes are 0.9 and 2.4 ppm for continuum and CO2 bands, respectively. While pointing out the challenge to characterise modern exo-Venus analogues, these results provide new insights for JWST proposals and highlight the influence of clouds in the spectrum of hot rocky exoplanet spectra.

Del Santo, M; Pinto, C; Marino, A; D’Aì, A; Petrucci, P-O; Malzac, J; Ferreira, J; Pintore, F; Motta, S E; Russell, T D; Segreto, A; Sanna, A

doi: 10.1093/mnrasl/slad048pmid: N/A

ABSTRACTThe transient X-ray source MAXI J1810−222 was discovered in 2018 and has been active ever since. A long combined radio and X-ray monitoring campaign was performed with Australia Telescope Compact Array and Swift, respectively. It has been proposed that MAXI J1810−222 is a relatively distant black hole X-ray binary, albeit showing a very peculiar outburst behaviour. Here, we report on the spectral study of this source making use of a large sample of NICER observations performed between 2019 February and 2020 September. We detected a strong spectral absorption feature at ∼1 keV, which we have characterized with a physical photoionization model. Via a deep scan of the parameters space, we obtained evidence for a spectral-state dependent outflow, with mildly relativistic speeds. In particular, the soft and intermediate states point to a hot plasma outflowing at 0.05–0.15c. This speeds rule-out thermal winds and hence, they suggest that such outflows could be radiation pressure or (most likely) magnetically driven winds. Our results are crucial to test current theoretical models of wind formation in X-ray binaries.

Banerjee, Anuvab; Sharma, Ajay; Mandal, Avijit; Das, Avik Kumar; Bhatta, Gopal; Bose, Debanjan

doi: 10.1093/mnrasl/slad057pmid: N/A

ABSTRACTIn this study, we carry out a comprehensive variability analysis of the BL Lac object 4FGL J2202.7+4216 detected by the Fermi-LAT, over a period of more than 3 yr, from 2019 April 27 to 2022 August 09. We detect the presence of quasi-periodic fluctuations with a period of ∼100 d with a confidence level exceeding 4σ. We also tentatively detect two other quasi-periodic fluctuations with a period of ∼75 and ∼50 d, which persist over the entire duration of observation. This is the first time such a variability feature pertaining to this source is being reported. We propose that the observed quasi-periodic oscillations may be related to the precession of the blazar jet with a high Lorentz factor or to the motion of a plasma blob through the helical structure of the jet. The harmonicity among the detected periodicities suggests the global p-mode oscillations of the thick disc to be a plausible mechanism as well. For a decisive conclusion on the physical origin of such fluctuation, further multiwavelength complementary observations, especially very long baseline interferometric observations, would be required.

Flower, D R

doi: 10.1093/mnrasl/slad047pmid: N/A

ABSTRACTIt has been suggested recently that three-body recombination of two protons and an electron might be significant in the formation of atomic hydrogen in the early Universe. We demonstrate that this process is completely negligible in the primordial plasma and that the value of the redshift, at which the transition from ionized to atomic hydrogen occurs, is determined by an equilibrium between the rates of two-body radiative recombination of a proton and an electron and its inverse, namely photoionization of atomic hydrogen.

Asada, Yoshihisa; Sawicki, Marcin; Desprez, Guillaume; Abraham, Roberto; Bradač, Maruša; Brammer, Gabriel; Harshan, Anishya; Iyer, Kartheik; Martis, Nicholas S; Mowla, Lamiya; Muzzin, Adam; Noirot, Gaël; Ravindranath, Swara; Sarrouh, Ghassan T E; Strait, Victoria; Willott, Chris J; Zabl, Johannes

Ferrami, G; Wyithe, J Stuart B

doi: 10.1093/mnrasl/slad050pmid: N/A

ABSTRACTThe bright end of the rest-frame ultraviolet luminosity function (UVLF) of high-redshift galaxies is modified by gravitational lensing magnification bias. Motivated by recent discoveries of very high-z galaxies with JWST, we study the dependence of magnification bias on the finite size of sources at 6 < z < 14. We calculate the magnification probability distributions and use these to calculate the magnification bias assuming a rest-frame Schechter UVLF for galaxies at redshift 6 < z < 14. We find that the finite size of bright high-redshift galaxies together with lens ellipticity significantly suppresses magnification bias, producing an observed bright end which declines more sharply than the power law resulting from assumption of point sources. By assuming a luminosity–size relation for the source population and comparing with the observed z  = 6 galaxy luminosity function from Harikane et al. (2022), we show that the UVLF can be used to set mild constraints on the galaxies intrinsic size, favouring smaller galaxies compared to the fiducial luminosity–size relation. In the future, wide surveys using Euclid and Roman Space Telescope will place stronger constraints. We also tabulate the maximum magnification possible as a function of source size and lens ellipticity.

Martin, Rebecca G

doi: 10.1093/mnrasl/slad061pmid: N/A

ABSTRACTSuperorbital periods are observed in the optical light curves of many Be/X-ray binaries yet their origin has remained somewhat elusive. We suggest that precession of the spin axis of the Be star can drive superorbital periods, particularly for short orbital period binaries. We consider the short orbital period ($P_{\rm orb}=16.6\, \rm d$) and highly eccentric (eb = 0.72) Be/X-ray binary A0538−66 that has a superorbital period of $421\, \rm d$. First, we show that the spin axis precession time-scale is about twice the observed superorbital period. Then, with hydrodynamic simulations we show that the Be star decretion disc can remain locked to the equator of the precessing Be star. At each periastron passage of the neutron star, material is accreted into a disc around the neutron star. The neutron star disc nodally precesses on the same time-scale as the Be star disc and therefore both discs can contribute to the observed superorbital period. For wider and less eccentric binary systems, the Be star disc can have a larger radial extent and more complex behaviour is expected as a result of disc warping and breaking.