Gamma-ray Burst host galaxy gas and dust

We report on the results of a study to obtain limits on the absorbing columns to wards an initial sample of 10 long Gamma-Ray Bursts observed with BeppoSAX, using a new approach to SED fitting to nIR, optical and X-ray afterglow data, in count space and including the effects of metallicity. When testing MW, LMC and SMC extinction laws we find that SMC-like extinction provides the best fit in most cases. A MW-like ext inction curve is not preferred for any of these sources, largely since the 2175A bump, in principle detectable in all these afterglows, is not present in the data. We rule out an SMC-like gas-to-dust ratio or lower value for 4 of the hosts analysed here (assuming SMC metallicity and extinction law) whilst the remainder of the sample have too large an error to discriminate. We provide an accurate estimate of the line-of-sight extinction, improving upon the uncertainties for the majority of the extinction measurements made in previous studies of this sample.Comment: 3 pages, 1 figure, MG11 proceeding

Optical Polarimetry of the May 2022 Lunar Eclipse

The sunlight reflected from the Moon during a total lunar eclipse has been transmitted through the Earth's atmosphere on the way to the Moon. The combination of multiple scattering and inhomogeneous atmospheric characteristics during that transmission can potentially polarize that light. A similar (although much smaller) effect should also be observable from the atmosphere of a transiting exoplanet. We present the results of polarization observations during the first 15 minutes of totality of the lunar eclipse of 2022 May 16. We find degrees of polarization of 2.1 +/- 0.4 per cent in B, 1.2 +/- 0.3 per cent in V, 0.5 +/- 0.2 per cent in R and 0.2 +/- 0.2 per cent in I. Our polarization values lie in the middle of the range of those reported for previous eclipses, providing further evidence that the induced polarization can change from event to event. We found no significant polarization difference (<0.02 per cent) between a region of dark Mare and nearby bright uplands or between the lunar limb and regions closer to the disk centre due to the different angle of incidence. This further strengthens the interpretation of the polarization's origin being due to scattering in the Earth's atmosphere rather than by the lunar regolith.Comment: Accepted for publication in MNRA

Optical Polarimetry of the May 2022 Lunar Eclipse

The sunlight reflected from the Moon during a total lunar eclipse has been transmitted through the Earth's atmosphere on the way to the Moon. The combination of multiple scattering and inhomogeneous atmospheric characteristics during that transmission can potentially polarize that light. A similar (although much smaller) effect should also be observable from the atmosphere of a transiting exoplanet. We present the results of polarization observations during the first 15 minutes of totality of the lunar eclipse of 2022 May 16. We find degrees of polarization of 2.1 +/- 0.4 per cent in B, 1.2 +/- 0.3 per cent in V, 0.5 +/- 0.2 per cent in R and 0.2 +/- 0.2 per cent in I. Our polarization values lie in the middle of the range of those reported for previous eclipses, providing further evidence that the induced polarization can change from event to event. We found no significant polarization difference (<0.02 per cent) between a region of dark Mare and nearby bright uplands or between the lunar limb and regions closer to the disk centre due to the different angle of incidence. This further strengthens the interpretation of the polarization's origin being due to scattering in the Earth's atmosphere rather than by the lunar regolith.Comment: Accepted for publication in MNRA

Seminal plasma and prostaglandin E2 up-regulate fibroblast growth factor 2 expression in endometrial adenocarcinoma cells via E-series prostanoid-2 receptor-mediated transactivation of the epidermal growth factor receptor and extracellular signal-regulated kinase pathway

We report a multiwavelength (X-ray, ultraviolet/optical/infrared, radio) analysis of the relativistic tidal disruption event candidate Sw J2058+05 from 3 months to 3 yr post-discovery in order to study its properties and compare its behavior with that of Sw J1644+57. Our main results are as follows. (1) The long-term X-ray light curve of Sw J2058+05 shows a remarkably similar trend to that of Sw J1644+57. After a prolonged power-law decay, the X-ray flux drops off rapidly by a factor of $\gtrsim 160$ within a span of $\Delta$$t$/$t$ $\le$ 0.95. Associating this sudden decline with the transition from super-Eddington to sub-Eddington accretion, we estimate the black hole mass to be in the range of $10^{4-6}$ M$_{\odot}$. (2) We detect rapid ($\lesssim 500$ s) X-ray variability before the dropoff, suggesting that, even at late times, the X-rays originate from close to the black hole (ruling out a forward-shock origin). (3) We confirm using HST and VLBA astrometry that the location of the source coincides with the galaxy's center to within $\lesssim 400$ pc (in projection). (4) We modeled Sw J2058+05's ultraviolet/optical/infrared spectral energy distribution with a single-temperature blackbody and find that while the radius remains more or less constant at a value of $63.4 \pm 4.5$ AU ($\sim 10^{15}$ cm) at all times during the outburst, the blackbody temperature drops significantly from $\sim$ 30,000 K at early times to a value of $\sim$ 15,000 K at late times (before the X-ray dropoff). Our results strengthen Sw J2058+05's interpretation as a tidal disruption event similar to Sw J1644+57.Comment: Replaced with the published version of the manuscrip

The host-galaxy response to the afterglow of GRB 100901A

For Gamma-Ray Burst 100901A, we have obtained Gemini-North and Very Large Telescope optical afterglow spectra at four epochs: one hour, one day, three days and one week after the burst, thanks to the afterglow remaining unusually bright at late times. Apart from a wealth of metal resonance lines, we also detect lines arising from fine-structure levels of the ground state of Fe II, and from metastable levels of Fe II and Ni II at the host redshift (z = 1.4084). These lines are found to vary significantly in time. The combination of the data and modelling results shows that we detect the fall of the Ni II 4 F9/2 metastable level population, which to date has not been observed. Assuming that the population of the excited states is due to the UV-radiation of the afterglow, we estimate an absorber distance of a few hundred pc. This appears to be a typical value when compared to similar studies. We detect two intervening absorbers (z = 1.3147, 1.3179). Despite the wide temporal range of the data, we do not see significant variation in the absorption lines of these two intervening systems.Comment: 17 pages, 9 figures. Accepted by Monthly Notices of the Royal Astronomical Society on Jan 11th 201

The diversity of kilonova emission in short gamma-ray bursts

The historic first joint detection of both gravitational-wave and electromagnetic emission from a binary neutron star merger cemented the association between short gamma-ray bursts (SGRBs) and compact object mergers, as well as providing a well-sampled multi-wavelength light curve of a radioactive kilonova (KN) for the first time. Here, we compare the optical and near-infrared light curves of this KN, AT 2017gfo, to the counterparts of a sample of nearby (z < 0.5) SGRBs to characterize their diversity in terms of their brightness distribution. Although at similar epochs AT 2017gfo appears fainter than every SGRB-associated KN claimed so far, we find three bursts (GRBs 050509B, 061201, and 080905A) where, if the reported redshifts are correct, deep upper limits rule out the presence of a KN similar to AT 2017gfo by several magnitudes. Combined with the properties of previously claimed KNe in SGRBs this suggests considerable diversity in the properties of KN drawn from compact object mergers, despite the similar physical conditions that are expected in many NS–NS mergers. We find that observer angle alone is not able to explain this diversity, which is likely a product of the merger type (NS–NS versus NS–BH) and the detailed properties of the binary (mass ratio, spins etc.). Ultimately disentangling these properties should be possible through observations of SGRBs and gravitational-wave sources, providing direct measurements of heavy element enrichment throughout the universe

VLT/X-shooter spectroscopy of the candidate black-hole X-ray binary MAXI J1659-152 in outburst

We present the optical to near-infrared spectrum of MAXI J1659-152, during the onset of its 2010 X-ray outburst. The spectrum was obtained with X-shooter on the ESO - Very Large Telescope (VLT) early in the outburst simultaneous with high quality observations at both shorter and longer wavelengths. At the time of the observations, the source was in the low-hard state. The X-shooter spectrum includes many broad (~2000 km/s), double-peaked emission profiles of H, HeI, HeII, characteristic signatures of a low-mass X-ray binary during outburst. We detect no spectral signatures of the low-mass companion star. The strength of the diffuse interstellar bands results in a lower limit to the total interstellar extinction of Av ~ 0.4 mag. Using the neutral hydrogen column density obtained from the X-ray spectrum we estimate Av ~1 mag. The radial-velocity structure of the interstellar NaI D and CaII H & K lines results in a lower limit to the distance of ~ 4 +/- 1 kpc, consistent with previous estimates. With this distance and Av, the dereddened spectral energy distribution represents a flat disk spectrum. The two subsequent 10 minute X-shooter spectra show significant variability in the red wing of the emission-line profiles, indicating a global change in the density structure of the disk, though on a timescale much shorter than the typical viscous timescale of the disk.Comment: Accepted for publication in ApJ Letter

AT2023fhn (the Finch): a luminous fast blue optical transient at a large offset from its host galaxy

Luminous fast blue optical transients (LFBOTs) – the prototypical example being AT 2018cow – are a rare class of events whose origins are poorly understood. They are characterized by rapid evolution, featureless blue spectra at early times, and luminous X-ray and radio emission. LFBOTs thus far have been found exclusively at small projected offsets from star-forming host galaxies. We present Hubble Space Telescope, Gemini, Chandra, and Very Large Array observations of a new LFBOT, AT 2023fhn. The Hubble Space Telescope data reveal a large offset (&amp;gt;3.5 half-light radii) from the two closest galaxies, both at redshift z ∼ 0.24. The location of AT 2023fhn is in stark contrast with previous events, and demonstrates that LFBOTs can occur in a range of galactic environments

JEAN-JACQUES ROUSSEAU – FRÈRE ENNEMI OF POLITICAL LIBERALISM

Je li Rousseau samorazumljivi neprijatelj političkog liberalizma, kao što glasi čuveni besprizivni pravorijek I. Berlina? Drukčije rečeno, je li on zastupnik radikalne (čak “totalitarne”) demokracije, apologet pučke suverenosti i opaki plebejski “prijatelj naroda” (tzv. “pozitivne slobode”), koji previđa važnost negativne slobode individua i podjele vlasti? Zagovara li Rousseau, kao republikanski politički teoretičar, s jedne strane i politički liberalizam, a s druge strane ne samo različito nego i oprečno shvaćanje političke slobode? U prvom se dijelu izlaganja podsjeća na to da se Rousseauova politička teorija oblikuje u osviještenoj i potpunoj opreci spram fiziokratskog ekonomskog liberalizma, koji slobodu svodi na ekonomsku i pravnu, a modernog čovjeka na bourgeois. U tome je Rousseau veoma blizak Tocquevilleu koji fiziokratsku doktrinu dovodi u pitanje sa stajališta političkog liberalizma. U drugom dijelu sažeto se prikazuje i vrednuje kritika Rousseauova političkog nauka (političke slobode i pučke suverenosti) sa stajališta klasičnoga političkog liberalizma B. Constanta. U trećem se završnom i najvažnijem dijelu pokazuje da primjerena usporedba Rousseauova i liberalnoga političkog nauka mora pažljivo razlikovati pojmovne sklopove u kojima se očituje srodnost (poimanje naroda i podjele vlasti) od onih u kojima se očituje suprotnost (poimanje naroda, zakona, općenite volje i citoyena). Otuda je Rousseau i frere i ennemi, dakle, frere ennemi političkoga liberalizma, premda ne i ekonomskog liberizma.Is Rousseau unquestionably an enemy of political liberalism, as per the famous irrevocable judgment of I. Berlin? In other words, is he a representative of radical (even “totalitarian”) democracy, an apologist of popular sovereignty and a vicious plebeian “friend of the people” (of so-called “positive freedom”), who overlooks the importance of negative freedom of individuums and the separation of powers? Are Rousseau as republican political theorist on the one hand and political liberalism on the other advocates not only of different, but opposite perceptions of political freedom? The first part of the paper recalls the fact that Rousseau’s political theory is shaped in a deliberate and complete opposition with regard to the physiocratic economic liberalism, which reduces freedom to its economic and legal aspects, and the modern man to a bourgeois. In this Rousseau is very close to Tocqueville, who questions the physiocratic doctrine from the standpoint of political liberalism. The second part provides a concise presentation and evaluation of the critique of Rousseau’s political doctrine (of political freedom and popular sovereignty) from the standpoint of B. Constant’s classic political liberalism. In the third, final and most important part, the author shows that an adequate comparison of Rousseau’s doctrine with the liberal political doctrine must carefully distinguish between the conceptual clusters reflecting affinity (the people and the separation of powers) and the ones reflecting opposition (the people, the law, the general will and the citoyen). On the basis of this distinction, Rousseau turns out to be both frere and ennemi – i.e. frere ennemi – of political liberalism, but not of economic liberism as well