Exploration of the high-redshift universe enabled by THESEUS

Experimental Astronomy - At peak, long-duration gamma-ray bursts are the most luminous sources of electromagnetic radiation known. Since their progenitors are massive stars, they provide a tracer...     

Variation of Leonid maximum times with location of observer

Abstract— A time adjustment from the Earth's centre to the observer's location is quantified and shown to improve the residuals between the observed time of pronounced Leonid showers and the time calculated from perturbed dust trails. A correlation with the exact time of closest approach to the nominal dust trail orbit would allow a further improvement in the residuals. However, there is no evidence for such a correlation, which suggests that the dust trail cross section is substantially elongated within the orbital plane. These results indicate that approaches to dust trails within 0.0005 AU are predictable with an uncertainty of ～5 min. Application of this correction to satellites confirms the utility of two strategies to minimise the impact risk. The time adjustment could be applied to any meteor stream.     

Long-term variability of the Be/X-ray binary EXO 2030+375

We present a multi-wavelength study of the Be/X-ray binary system EXO 2030+375. We report that the Be companion is currently in a low-activity phase as indicated by the notable decrease of the infrared and optical emission. If this trend continues the source will lose its circumstellar envelope. Infrared spectroscopy in the IJHK bands is presented for the first time, along with optical and X-ray observations. These infrared spectra agree with the optical companion being an early-type (B0) main-sequence star. When active EXO 2030+375 shows an X-ray outburst at each periastron passage of the neutron star. In addition to the maximum X-ray luminosity displayed at orbital phase ∼0.0, we find a smaller maximum in the light curve at phase ∼0.5. This second intensity peak may be explained if the velocity of the wind is lower than or comparable to the orbital velocity of the neutron star at apastron. We also comment on the relation between the optical/infrared behaviour and the X-ray emission and argue that the X-ray inactive period observed between 1993 August and 1996 April is a result of centrifugal inhibition of accretion of matter rather than a low-activity circumstellar disc.     

A search for radio remnants of ancient oriental “guest stars” with the westerbork telescope

Seven 1.5° × 1.5° fields in which “guest stars” had been reported by ancient oriental astronomers have been surveyed at 610 MHz for radio remnants with the Westerbork Telescope. No diffuse radio emission was detected. A list of discrete radio sources in the fields is given together with suggested optical identifications for those sources with |b| < 15°.     

The Chemical Diversity of Comets: Synergies Between Space Exploration and Ground-based Radio Observations

A fundamental question in cometary science is whether the different dynamical classes of comets have different chemical compositions, which would reflect different initial conditions. From the ground or Earth orbit, radio and infrared spectroscopic observations of a now significant sample of comets indeed reveal deep differences in the relative abundances of cometary ices. However, no obvious correlation with dynamical classes is found. Further results come, or are expected, from space exploration. Such investigations, by nature limited to a small number of objects, are unfortunately focussed on short-period comets (mainly Jupiter-family). But these in situ studies provide “ground truth” for remote sensing. We discuss the chemical differences in comets from our database of spectroscopic radio observations, which has been recently enriched by several Jupiter-family and Halley-type comets.     

Timing properties of the X-ray pulsar EXO 2030+375 during an X-ray outburst

We present Rossi X-ray Timing Explorer ( RXTE ) observations of the Be/X-ray transient EXO 2030+375 during an outburst after a period of quiescence between 1993 August and 1996 April. When active, EXO 2030+375 is normally detected at each periastron passage of the neutron star. Our observations correspond to the third periastron passage after the source 'turned on' again. All outbursts after the quiescent period, including the one reported here, have been occurring at a much earlier binary phase than in the past. We discuss the possible mechanisms that may explain this shift in the onset of the outburst. Pulsations in the X-ray radiation are detected throughout the entire run. The neutron star spun up during the outburst at a rate of −1.16×10⁻⁸ s s⁻¹, but no variations in the shape of the pulse profile as a function of intensity were seen. A correlation between the hardness ratio and the intensity is observed at low energies (6–12/2–6 keV). By comparing the magnetospheric and corotation radii we argue that the neutron star spins at a rate close to the equilibrium period. Finally, we perform pulse-phase spectroscopy and comment on changes seen as a function of spin phase.     

Observations of minor planets with the very large array

The weak thermal emission from the largest minor planets can be detected and measured at all points around their orbits at microwave frequencies using the Very Large Array (VLA). Position determinations of astrometric quality have been obtained, and flux measurements have provided size estimates. When enough precise positional observations have been accumulated, the orbits of the minor planets and the Earth can be determined. This will allow the equinox to be located within the radio reference frame, providing a truly fundamental coordinate system for radio source positions. It will also provide a means of relating the optical and radio (quasar) coordinate systems.The National Radio Astronomy Observatory is operated by Associated Universities, Incorporated, under contract with the National Science Foundation.     

Unveiling the formation of stars and planets with a large infrared-optical telescope

Diffraction-limited imaging in the near-IR (with the aid of adaptive optics) to middle-IR wavelengths will be a major breakthrough with 8m IR-optical telescopes. Special interest is on the scale of planet formation, that is, within 100 AU of the embedded sources in the nearby Taurus or Ophiuchus clouds. In this report, we demonstrate the sensitivity of a telescope with a virtual instrument that covers a wide spectral range.     

Study of the unknown hemisphere of mercury by ground-based astronomical facilities

The short exposure method proved to be very productive in ground-based observations of Mercury. Telescopic observations with short exposures, together with computer codes for the processing of data arrays of many thousands of original electronic photos, make it possible to improve the resolution of images from ground-based instruments to almost the diffraction limit. The resulting composite images are comparable with images from spacecrafts approaching from a distance of about 1 million km. This paper presents images of the hemisphere of Mercury in longitude sectors 90°–180°W, 215°–350°W, and 50°–90°W, including, among others, areas not covered by spacecraft cameras. For the first time a giant S basin was discovered in the sector of longitudes 250°–290°W, which is the largest formation of this type on terrestrial planets. Mercury has a strong phase effects. As a result, the view of the surface changes completely with the change in the planetary phase. But the choice of the phase in the study using spacecrafts is limited by orbital characteristics of the mission. Thus, ground-based observations of the planet provide a valuable support.     

Io's interaction with the magnetosphere

Jupiter's innermost Galilean satellite Io is regarded as a fairly good conductor ($\text{σ > 10}{}^{\mathrm{?5}}\text{Ω}{}^{\mathrm{?1}}\text{m}{}^{\mathrm{?1}}$). The trapping of magnetic field lines by Io and their deformation is described. A neutral point forms in the vicinity of the satellite. The magnetic field annihilation in the neutral point is enhanced by the emission of low frequency hmd waves. The power carried away by these waves may be as high 10¹⁵ W. The characteristic frequency of the wave and its variation while Io orbits around Jupiter is determined.     

Radio observations of comet 9P/Tempel 1 with the Australia Telescope facilities during the Deep Impact encounter

We present radio observations of comet 9P/Tempel 1 associated with the Deep Impact spacecraft collision of 2005 July 4. Weak 18-cm OH emission was detected with the Parkes 64-m telescope, in data averaged over July 4–6, at a level of  12 ± 3 mJy km s⁻¹  , corresponding to OH production rate  2.8 × 10²⁸  molecules s⁻¹ (Despois et al. inversion model, or  1.0 × 10²⁸ s⁻¹  for the Schleicher & A'Hearn model). We did not detect the HCN 1–0 line with the Mopra 22-m telescope over the period July 2–6. The 3σ limit of 0.06 K km s⁻¹ for HCN on July 4 after the impact gives the limit to the HCN production rate of  <1.8 × 10²⁵ s⁻¹  . We did not detect the HCN 1–0 line, 6.7 GHz CH₃OH line or 3.4-mm continuum with the Australia Telescope Compact Array (ATCA) on July 4, giving further limits on any small-scale structure due to an outburst. The 3σ limit on HCN emission of 2.5 K km s⁻¹ from the ATCA around impact corresponds to limit < 4 × 10²⁹ HCN molecules released by the impact.     

Productivity and impact of astronomical facilities: A recent sample

The papers published in 11 key astronomical journals in 2008, and a year of citations to those from the first half of the year, have been associated with the telescopes, satellites, and so forth where the data were gathered using a form of fractional counting. Some numbers are also given by journal, by subfield, and by wavelength band. The largest numbers of papers, and generally also quite highly cited ones, in their respective wavelength bands come from the Very Large Array, the Hubble Space Telescope, the Sloan Digital Sky Survey, the Spitzer Space Telescope, and the Chandra X‐ray Telescope. Optical astronomy is still the largest sector; and papers about cosmology and exoplanets are cited more often than papers about binary stars and planetary nebulae. The authors conclude that it is of equal importance to recognize (a) that a very large number of papers also come from less famous facilities, (b) that a very large fraction of papers (and their authors) are concerned with the less highly‐cited topics, (c) that many facilities are quite slow in achieving their eventual level of influence, and (d) that one really needs at least three years of citation data, not just one or two, to provide a fair picture of what is going on (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The planning of NOAO 8 m telescope enclosure and facilities

The National Optical Astronomy Observatories (NOAO) proposes to build 8 m telescopes at two locations. The Northern Hemisphere location is on Mauna Kea, Hawaii, and the Southern Hemisphere location is within the existing boundary of the Cerro Tololo Inter-American Observatory. This paper describes the sites under consideration and the facilities that support the operation of each telescope, namely, the telescope enclosure, the control facility, and the recoating facility.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.Operated by the Association of Universities for Research in Astronomy Inc., under contract with the National Science Foundation.     

Dependence of large SEP events with different energies on the associated flares and CMEs

To investigate the dependence of large gradual solar energetic particle(SEP) events on the associated flares and coronal mass ejections(CMEs), the correlation coefficients(CCs) between peak intensities of E 10 MeV(I_(10)), E 30 MeV(I_(30)) and E 50 MeV(I_(50)) protons and soft X-ray(SXR) emission of associated flares and the speeds of associated CMEs in the three longitudinal areas W0–W39, W40–W70(hereafter the well connected region) and W71–W90 have been calculated.Classical correlation analysis shows that CCs between SXR emission and peak intensities of SEP events always reach their largest value in the well connected region and then decline dramatically in the longitudinal area outside the well connected region, suggesting that they may contribute to the production of SEPs in large SEP events. Both classical and partial correlation analyses show that SXR fluence is a better parameter describing the relationship between flares and SEP events. For large SEP events with source location in the well connected region, the CCs between SXR fluence and I_(10), I_(30) and I_(50) are0.58±0.12, 0.80±0.06 and 0.83±0.06 respectively, while the CCs between CME speed and I_(10), I_(30) and I_(50) are 0.56±0.12, 0.52±0.13 and 0.48±0.13 respectively. The partial correlation analyses show that in the well connected region, both CME shock and SXR fluence can significantly affect I_(10), but SXR peak flux makes no additional contribution. For E 30 MeV protons with source location in the well connected region, only SXR fluence can significantly affect I_(30), and the CME shock makes a small contribution to I_(30), but SXR peak flux makes no additional contribution. For E 50 MeV protons with source location in the well connected region, only SXR fluence can significantly affect I_(50), but both CME shock and SXR peak flux make no additional contribution. We conclude that these findings provide statistical evidence that for SEP events with source locations in the well connected region, a CME shock is only an effective accelerator for E 30 MeV protons. However, flares are not only effective accelerators for E 30 MeV protons, but also for E 30 MeV protons, and E 30 MeV protons may be mainly accelerated by concurrent flares.     

Unravelling unidentified γ-ray sources with the large millimeter telescope

The understanding of the high energy γ-ray sky requires a coordinated multi-wavelength strategy. The Large Millimeter Telescope will be the largest and most sensitive single dish antenna operating between 0.8 mm and 3 mm in the foreseeable future. Its first light instrumentation and capabilities are well suited for studies of dust, dense molecular gas and the synchrotron emission from relativistic electrons. The Large Millimeter Telescope, due to enter commissioning and first light science phase in 2007, will be able to complement GLAST observations and help disentangling the nature of the new and old unidentified gamma-ray sources. Work sponsored by CONACyT grant SEP-2003-C02-42611.     

Curation planning and facilities for asteroid Bennu samples returned by the OSIRIS-REx mission

NASA's OSIRIS-REx spacecraft collected samples from carbonaceous near-Earth asteroid (101955) Bennu on October 20, 2020, and will deliver them to the Earth on September 24, 2023. The samples will be processed at the NASA Johnson Space Center (JSC), where most of the sample collection will be subsequently curated in a new cleanroom suite. The spacecraft collected loose regolith two ways: in a bulk sample chamber capable of holding up to 2 kg, and on industrial Velcro “contact pads” intended to collect small particles at the surface. Included in the JSC collection will be the bulk sample, the contact pads, contamination-monitoring witness plates, and supporting hardware. Planning for the curation of the samples and hardware started at the earliest phase of proposal development and continued in parallel with project development and execution. Because a major mission goal is characterization of organic compounds in the Bennu samples, extra effort was spent in the design stage to ensure a clean curation environment. Here, we describe the preparations to receive the sample, including the design, construction, outfitting, and monitoring of the cleanrooms at JSC; the planned recovery of the sample-containing capsule when it lands on Earth; and the approach to characterizing and cataloging the samples. These curation efforts will result in the distribution of pristine Bennu samples from JSC to the OSIRIS-REx science team, international partners, and the global scientific community for years to come.     

Can the optical very large array be coupled with the JNLT?

Coupling the JNLT with the Keck telescope is of considerable interest. Further enhancement may be possible with auxiliary small telescopes, as planned for ESO's VLT. Current plans for installing the optical very large array at Mauna Kea provide opportunities for extra OVLA telescopes near the JNLT.A coudé field slicer is proposed for interferometric observing of a reference star together with the main object. Additions to the JNLT coudé spectrograph are also suggested for use as a speckle camera with multiple spectral channels.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.