Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p>Nulling pulsars are pulsars whose observed flux occasionally disappears, but the mechanism behind the cessation is not well understood. Motivated by the correlation between pulse width and nulling fraction found in Sheikh &amp; MacDonald, we compile all 378 nulling pulsars to date with their pulse widths in a machine-readable table. We also include the observing frequency and time resolution of each pulse width measurement. Such a table will be useful for future studies of this population.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Stars in multiple systems offer a unique opportunity to learn about stellar formation and evolution. As they settle down into stable configurations, multiple systems occur in a variety of hierarchies and a wide range of separations between the components. We examine 11 known and 11 newly discovered multiple systems including at least one M dwarf with the latest astrometric data from Gaia Early Data Release 3 (EDR3). We find that the individual components of systems at very wide separations are often multiple systems themselves.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The upcoming X-ray missions based on the microcalorimeter technology require exquisite precision in spectral simulation codes in order to match the unprecedented spectral resolution. In this work, we improve the fluorescence K<jats:italic>α</jats:italic> energies for Si <jats:sc>ii–xi</jats:sc> and S <jats:sc>ii–xiii</jats:sc> in the code Cloudy. In particular, we provide here a patch to update the Cloudy fluorescence energy table, originally based on Kaastra &amp; Mewe, with the laboratory energies measured by Hell et al. The new Cloudy simulations were used to model the Chandra/HETG spectra of the High Mass X-ray Binary Vela X-1, showing a remarkable agreement and a dramatic improvement with respect to the current release version of Cloudy (C17.02).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present <jats:italic>V</jats:italic> and <jats:italic>I</jats:italic> photometry for the Be/X-ray binary Swift J010745.0-722740 taken in 1997–2020. The data show recurring outbursts, with an amplitude up to 0.4 mag and an improved orbital period of 1180.0 ± 0.3 days. The light curve during outburst has a double-peaked profile, with a rapid rise and gradual decline. The effective temperature of the outburst region is ∼6200 K, much cooler than that of an underlying Be star.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present time resolved low resolution spectra of BLAP-009 and BLAP-014 collected with SPRAT on the Liverpool Telescope. The spectra were median-stacked in four ranges of phase. It was intended to note the variation in the shape of the helium absorption lines as a function of phase, but they do not appear to vary with time in low resolution spectra. The lack of clear offsets in the absorption lines suggest that there can only be small radial velocity due to either unseen companion or rapid expansion/contraction of the envelope.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>1RXS J180431.1-273932 is an intermediate polar: a cataclysmic variable star with a rapidly rotating, magnetized white dwarf. We analyze the system’s Kepler K2 short-cadence light curve and identify a strong, highly coherent pulse with a period of 0.0057171 ± 0.0000002 days, which matches the proposed white dwarf rotational period identified in previous X-ray studies. We establish an ephemeris for the optical spin pulse.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The mission of the 2000 kg Cassini spacecraft concluded on 2017 September 15, by its deliberate entry into Saturn’s atmosphere at some 31.1 km s<jats:sup>−1</jats:sup>. Observations, using Hubble and groundbased observatories, to attempt optical detection of this 0.25 kT “artificial meteor” are summarized. No signatures were identified. A challenge with observing the event is that due to atmospheric drag, its timing was not completely deterministic months or even days in advance, a particular problem for space observatories. While imaging observations needed no geometric specification more than “Saturn,” observations with spectrometers required pointing the instrument aperture or slit at the specific impact site. Since giant planet longitude systems are not always familiar, distribution of an unambiguous “finder chart” showing the location of the predicted entry site on the disk is essential, as is clarity on whether stated times are spacecraft event time, or Earth received time (light-travel time, 83 minutes, later).</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigate the orientation of the photospheric magnetic fields in the solar polar region using observations from the Helioseismic and Magnetic Imager (HMI). Inside small patches of significant polarization, the inferred magnetic field vectors at 1″ scale appear to systematically deviate from the radial direction. Most tilt toward the pole; all are more inclined toward the plane of sky compared to the radial vector. These results, however, depend on the “filling factor” <jats:italic>f</jats:italic> that characterizes the unresolved magnetic structures. The default, uninformative <jats:italic>f</jats:italic> ≡ 1 for HMI will incur larger inclination and less radial fields than <jats:italic>f</jats:italic> &lt; 1. The observed trend may be a systematic bias inherent to the limited resolution.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The International Astronomical Youth Camp (IAYC) is an astronomy education outreach event with more than 50 yr of history and over 1700 unique participants from 81 nationalities. The International Workshop for Astronomy e.V. is the non-profit organization behind the IAYC, established in 1979 and based in Germany. The IAYC’s unprecedented longevity in a rapidly globalizing world has meant that financial inequities decreases the reach of the camp to people from the Global South compared to Global North countries. Though nationalities represented per camp has increased steadily since its inception, the share of participants from eastern Europe and Africa has dropped, while those from western Europe and North America have increased. This note examines how camp cost, location, and leadership affects nationality diversity among participants, and how astronomy outreach events must reckon with funding for less privileged participants with limited access to resources.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present X-ray analysis of three short Chandra observations of M87. The basis of this analysis is the search for possible new ultraluminous X-ray sources (ULXs) in M87's globular clusters (GCs) and attempt to quantify possible variability within the observations. We searched Chandra ObsIDs 1808 (2000 July 30, 14 ks) Wilson &amp; Yang, 3975 (2002 November 17, 5 ks) and 3977 (2003 February 4, 5 ks) Harris et al. and identified one previously discovered GC ULX, and two new GC ULX candidates. Analysis of the light-curves revealed no new evidence of variability in these sources for the duration of the observations.</jats:p>