Astronomical Informant

2022-06-20 19:02:16 ATel 15446: Swift Observations of MAXI J1957+032 during its 2022 outburst
https://www.astronomerstelegram.org/?read=15446

MAXI J1957+032 has been reported to be in a new outburst by the MAXI/GSC (ATel #15440). On 2022 June 19 the NICER X-ray telescope detected MAXI J1957+032 with a 0.3-10 keV flux of 2.5e-10 erg/s/cm^2. ... Aprire / Come

2022-06-20 13:04:07 ATel 15445: Search for an optical and NIR counterpart of the newly discovered Accreting Millisecond X-ray Pulsar MAXI J1816-195
https://www.astronomerstelegram.org/?read=15445

MAXI J1816-195 is a newly discovered X-ray transient (ATel #15418). The source was first detected with the MAXI/GSC on 2022 June 7 (MJD 59737; ATel #15418); its X-ray position was then confirmed with higher precision by Swift/XRT observations (ATel #15421). ... Aprire / Come

2022-06-20 05:37:04 arXiv:We propose a novel design for a lightweight, high-performance space-based solar power array combined with power beaming capability for operation in geosynchronous orbit and transmission of power to Earth. We use a modular configuration of small, repeatable unit cells, called tiles, that each individually perform power collection, conversion, and transmission. Sunlight is collected via lightweight parabolic concentrators and converted to DC electric power with high efficiency III-V photovoltaics. Several CMOS integrated circuits within each tile generates and controls the phase of multiple independently-controlled microwave sources using the DC power. These sources are coupled to multiple radiating antennas which act as elements of a large phased array to beam the RF power to Earth. The power is sent to Earth at a frequency chosen in the range of 1-10 GHz and collected with ground-based rectennas at a local intensity no larger than ambient sunlight. We achieve significantly reduced mass compared to previous designs by taking advantage of solar concentration, current CMOS integrated circuit technology, and ultralight structural elements. Of note, the resulting satellite has no movable parts once it is fully deployed and all beam steering is done electronically. Our design is safe, scalable, and able to be deployed and tested with progressively larger configurations starting with a single unit cell that could fit on a cube satellite. The design reported on here has an areal mass density of 160 g/m2 and an end-to-end efficiency of 7-14%. We believe this is a significant step forward to the realization of space-based solar power, a concept once of science fiction.

via astro-ph updates on arXiv.org https://ift.tt/CM9wbJz Aprire / Come

2022-06-20 05:36:56 arXiv:We study the distributions of the baryons in massive halos ($M_{vir} > 10^{13} \ h^{-1}M_{\odot}$) in the $Magneticum$ suite of Smoothed Particle Hydrodynamical cosmological simulations, out to the unprecedented radial extent of $10 R_{500,\mathrm c}$. We confirm that, under the action of non-gravitational physical phenomena, the baryon mass fraction is lower in the inner regions ($6 R_{500,\mathrm c}$), where the baryon depletion factor $Y_{\rm bar} = f_{\rm bar} / (\Omega_{\rm b}/\Omega_{\rm m})$ approaches the value of unity, expected for "closed-box" systems. We find that both the radial and mass dependency of the baryon, gas, and hot depletion factors are predictable and follow a simple functional form. The star mass fraction is higher in less massive systems, decreases systematically with increasing radii, and reaches a constant value of $Y_{\rm star} \approx 0.09$, where also the gas metallicity is constant, regardless of the host halo mass, as a result of the early ($z>2$) enrichment process.

via astro-ph updates on arXiv.org https://ift.tt/6PXVpc8

2 views02:36

Aprire / Come

2022-06-20 05:36:53 arXiv:We report the results of a 2019-2021 monitoring campaign with Swift and associated target-of-opportunity observations with XMM-Newton and NuSTAR, examining the spectral and timing behavior of the highly variable ultraluminous X-ray source (ULX) NGC 925 ULX-3. We find that the source exhibits a 127-128 day periodicity, with fluxes typically ranging from 1e-13 to 8e-13 ergs/s/cm2. We do not find strong evidence for a change in period over the time that NGC 925 ULX-3 has been observed, although the source may have been in a much lower flux state when first observed with Chandra in 2005. We do not detect pulsations, and we place an upper limit on the pulsed fraction of ~40% in the XMM-Newton band, consistent with some previous pulsation detections at low energies in other ULXs. The source exhibits a typical ULX spectrum that turns over in the NuSTAR band and can be fitted using two thermal components. These components have a high temperature ratio that may indicate the lack of extreme inner disk truncation by a magnetar-level magnetic field. We examine the implications for a number of different models for superorbital periods in ULXs, finding that a neutron star with a magnetic field of ~10^12 G may be plausible for this source. The future detection of pulsations from this source would allow for the further testing and constraining of such models.

via astro-ph updates on arXiv.org https://ift.tt/FN7CzAw Aprire / Come

2022-06-20 04:37:13 arXiv:We present Suzaku observations of the Abell 98 (A98) triple galaxy cluster system and the purported intercluster filament. The three subclusters are expected to lie along a large scale cosmic filament. With partial azimuthal coverage of the northernmost cluster, we find that the inferred entropy profile of this relatively low mass cluster ($kT \approx 2.8$ keV) adheres to expectations from models of self-similar pure gravitational collapse in the region of the virial radius. There is evidence of extended structure beyond $r_{200}$ to the north of the northernmost cluster, along the merger axis, with properties consistent with what is expected for the warm-hot intergalacitc medium (WHIM; $kT = 0.11_{-0.02}^{+0.01}$ keV, $n_e = {7.6 \times 10^{-5}}^{+3.6 \times 10^{-5}}_{-3.6 \times 10^{-5}}$~cm$^{-3}$). No such emission is detected at the same radius in regions away from the merger axis, consistent with the expectation that the merger axis of this triple system lies along a large scale cosmic filament. In the bridge region between A98N and A98S, there is evidence of filamentary emission at the $2.2\sigma$ level, as well as a tentative detection of cool gas ($kT \sim 1$ keV). The entropy profile of this intercluster filament suggests that the A98 system is most likely aligned closer to the plane of the sky rather than along the line of sight. The structure to the north of the system, as well as in between A98N and A98S is indicative that the clusters are connected to a larger-scale structure spanning at least 4 Mpc.

via astro-ph updates on arXiv.org https://ift.tt/n4S9He7 Aprire / Come

2022-06-20 04:37:11 arXiv:We make the case that there can be no low-redshift solution to the $H_0$ tension. To robustly answer this question, we use a very flexible parameterization for the dark energy equation of state such that every cosmological distance still allowed by data exists within this prior volume. To then answer whether there exists a satisfactory solution to the $H_0$ tension within this comprehensive parameterization, we constrained the parametric form using different partitions of the Planck cosmic microwave background, SDSS-IV/eBOSS DR16 baryon acoustic oscillation, and Pantheon supernova datasets. When constrained by just the cosmic microwave background dataset, there exists a set of equations of state which yields high $H_0$ values, but these equations of state are ruled out by the combination of the supernova and baryon acoustic oscillation datasets. In other words, the constraint from the cosmic microwave background, baryon acoustic oscillation, and supernova datasets together does not allow for high $H_0$ values and converges around an equation of state consistent with a cosmological constant. Thus, since this very flexible parameterization does not offer a solution to the $H_0$ tension, there can be no solution to the $H_0$ tension that adds physics at only low redshifts.

via astro-ph updates on arXiv.org https://ift.tt/j5riYFb Aprire / Come

2022-06-20 04:37:09 arXiv:The period and the period derivative of a pulsar are critical magnitudes for defining the properties of the magnetospheric size and plasma dynamics. The pulsar light cylinder, the magnetic field intensity nearby it, and the curvature radius all depend on these timing properties, and shape the observed high-energy synchro-curvature emission. Therefore, the radiative properties of pulsars are inextricably linked to them. This fact poses the question of how well does a given pulsar's spectral energy distribution embeds information of the timing parameters, and if so, whether we can deduce them if they have not been measured directly. This is relevant to possibly constrain the timing properties of potential pulsar candidates among unidentified $\gamma$-ray sources. We consider well-measured pulsar spectra blinding us from the knowledge of their timing properties, and address this question by using our radiative synchro-curvature model that was proven able to fit the observed spectra of the pulsar population. We find that in the majority of the cases studied (8/13), the spin period is constrained within a range of about one order of magnitude, within which the real period lies. In the other cases, there is degeneracy and no period range can be constrained. This can be used to facilitate the blind search of pulsed signals.

via astro-ph updates on arXiv.org https://ift.tt/D1VsmfG Aprire / Come

2022-06-18 07:55:20 VP Hosts NASA for Family STEM Event, Disney Pixar’s Lightyear Viewing
http://www.nasa.gov/press-release/vp-hosts-nasa-for-family-stem-event-disney-pixar-s-lightyear-viewing

Vice President Kamala Harris and Second Gentleman Douglas Emhoff hosted an evening of NASA STEM activities Friday at the Naval Observatory for military families and local students and their families, which included a special screening of Disney Pixar’s Lightyear. Aprire / Come

2022-06-18 06:31:29 VP Hosts NASA for Family STEM Event, Disney Pixar’s Lightyear Viewing
http://www.nasa.gov/press-release/vp-hosts-nasa-for-family-stem-event-disney-pixar-s-lightyear-viewing

Vice President Kamala Harris and Second Gentleman Douglas Emhoff hosted an evening of NASA STEM activities Friday at the Naval Observatory for military families and local students and their families, which included a special screening of Disney Pixar’s Lightyear. Aprire / Come