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<jats:title>Abstract</jats:title> <jats:p>The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory surveys the very high-energy sky in the 300 GeV to &gt;100 TeV energy range. HAWC has detected two blazars above 11<jats:italic>σ</jats:italic>, Markarian 421 (Mrk 421) and Markarian 501 (Mrk 501). The observations are comprised of data taken in the period between 2015 June and 2018 July, resulting in ∼1038 days of exposure. In this work, we report the time-averaged spectral analyses for both sources, above 0.5 TeV. Taking into account the flux attenuation due to the extragalactic background light, the intrinsic spectrum of Mrk 421 is described by a power law with an exponential energy cutoff with index <jats:inline-formula> <jats:tex-math> <?CDATA $\alpha =2.26\pm {\left(0.12\right)}_{\mathrm{stat}}{\left({}_{-0.2}^{+0.17}\right)}_{\mathrm{sys}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>α</mml:mi> <mml:mo>=</mml:mo> <mml:mn>2.26</mml:mn> <mml:mo>±</mml:mo> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mn>0.12</mml:mn> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>stat</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.17</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>sys</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac58f6ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> and energy cutoff <jats:inline-formula> <jats:tex-math> <?CDATA ${E}_{c}=5.1\pm {\left(1.6\right)}_{\mathrm{stat}}{\left({}_{-2.5}^{+1.4}\right)}_{\mathrm{sys}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>E</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>5.1</mml:mn> <mml:mo>±</mml:mo> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mn>1.6</mml:mn> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>stat</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2.5</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>1.4</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>sys</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac58f6ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> TeV, while the intrinsic spectrum of Mrk 501 is better described by a simple power law with index <jats:inline-formula> <jats:tex-math> <?CDATA $\alpha =2.61\pm {\left(0.11\right)}_{\mathrm{stat}}{\left({}_{-0.07}^{+0.01}\right)}_{\mathrm{sys}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>α</mml:mi> <mml:mo>=</mml:mo> <mml:mn>2.61</mml:mn> <mml:mo>±</mml:mo> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:mn>0.11</mml:mn> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>stat</mml:mi> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mfenced close=")" open="("> <mml:mrow> <mml:msubsup> <mml:mrow /> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.07</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.01</mml:mn> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:mfenced> </mml:mrow> <mml:mrow> <mml:mi>sys</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac58f6ieqn3.gif" xlink:type="simple" /> </jats:inline-formula>. The maximum energies at which the Mrk 421 and Mrk 501 signals are detected are 9 and 12 TeV, respectively. This makes these some of the highest energy detections to date for spectra averaged over years-long timescales. Since the observation of gamma radiation from blazars provides information about the physical processes that take place in their relativistic jets, it is important to study the broadband spectral energy distributions (SEDs) of these objects. For this purpose, contemporaneous data in the gamma-ray band to the X-ray range, and literature data in the radio to UV range, were used to build time-averaged SEDs that were modeled within a synchrotron-self Compton leptonic scenario.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Density irregularities are responsible for the scattering of radio waves in the solar wind and astrophysical plasmas. These irregularities significantly affect the inferred physical properties of radio sources, such as size, direction, and intensity. We present here a theory of angular broadening due to the scattering of radio waves by density irregularities that improves the existing formalism used to investigate radio wave scattering in the outer heliosphere and the very local interstellar medium. The model includes an inner scale and both latitudinal and radial dependencies for the density fluctuation spectra and propagation paths for the radiation both near and out of the ecliptic plane. Based on the pickup-ion-mediated solar wind model (PUI model) of Zank et al., we estimate the turbulence and solar wind quantities for the high-latitude fast solar wind. The predictions include the density variance, inner/dissipation scale, velocity correlation length, mean magnetic field, and proton temperature. The density turbulence amplitude is estimated in two ways. First, a simple scaling technique is used to extend the theoretical predictions of the PUI model for the high-latitude wind beyond the heliospheric termination shock. Second, the solar wind and turbulence quantities are calculated near the ecliptic plane using plasma and magnetometer data from the Voyager 2 spacecraft over the period 1977–2018. Based on the turbulence models and observations, we calculate the scattering angle of the radio sources in the high-latitude and near-ecliptic wind. Finally, we compare the numerical results with the analytic predictions from Cairns and Armstrong et al. and the observed source sizes.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Using pitch-angle-resolved electron fluxes recorded by the Mars Atmosphere and Volatile Evolution spacecraft over 5 yr, we present a detailed analysis of the occurrence patterns of photoelectron butterfly pitch-angle distributions (PADs) in the Martian ionosphere. Statistical analysis indicates that Martian photoelectron butterfly PADs favorably occur near the moderate crustal magnetic fields with a strength of 10–30 nT on the dayside and 10–15 nT on the nightside. The nightside occurrence rates are much higher. Furthermore, dayside butterfly PADs prefer to occur near the vertical magnetic field lines in the ionosphere, and the significant day-to-night transport of photoelectrons evades the nightside strongest magnetic anomaly regions. These features strongly support the idea that Martian photoelectron butterfly PADs are more likely to occur in eclipse or near the terminator and that they mainly form due to the adiabatic evolution of photoelectrons that transport along the closed cross-terminator magnetic field lines. Despite the negligible energy dependence in the darkness, the occurrence rate of dayside butterfly PADs observed at higher altitudes and near the subsolar region increases with energy, presumably related to the increased proportion of electrons from the solar wind when measured at relatively higher electron energies, which, however, is limitedly understood and deserves future investigation. Our comprehensive observations suggest the diverse influence of Martian magnetic topology on the ionospheric plasma in different spatial regions, and, in turn, analysis of their influence allows us a better understanding of the intricate Martian global magnetic system.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We compare dynamical mass estimates based on spatially extended stellar and ionized gas kinematics (<jats:italic>M</jats:italic> <jats:sub> dyn,*</jats:sub> and <jats:italic>M</jats:italic> <jats:sub>dyn,eml</jats:sub>, respectively) of 157 star-forming galaxies at 0.6 ≤ <jats:italic>z</jats:italic> &lt; 1. Compared with <jats:italic>z</jats:italic> ∼ 0, these galaxies have enhanced star formation rates, with stellar feedback likely affecting the dynamics of the gas. We use LEGA-C DR3, the highest-redshift data set that provides sufficiently deep measurements of a <jats:italic>K</jats:italic> <jats:sub> <jats:italic>s</jats:italic> </jats:sub>-band limited sample. For <jats:italic>M</jats:italic> <jats:sub> dyn,*</jats:sub>, we use Jeans anisotropic multi-Gaussian expansion models. For <jats:italic>M</jats:italic> <jats:sub>dyn,eml</jats:sub>, we first fit a custom model of a rotating exponential disk with uniform dispersion, whose light is projected through a slit and corrected for beam smearing. We then apply an asymmetric drift correction based on assumptions common in the literature to the fitted kinematic components to obtain the circular velocity, assuming hydrostatic equilibrium. Within the half-light radius, <jats:italic>M</jats:italic> <jats:sub>dyn,eml</jats:sub> is on average lower than <jats:italic>M</jats:italic> <jats:sub> dyn,*</jats:sub>, with a mean offset of –0.15 ± 0.016 dex and galaxy-to-galaxy scatter of 0.19 dex, reflecting the combined random uncertainty. While data of higher spatial resolution are needed to understand this small offset, it supports the assumption that the galaxy-wide ionized gas kinematics do not predominantly originate from disruptive events such as star formation–driven outflows. However, a similar agreement can be obtained without modeling from the integrated emission line dispersions for axis ratios <jats:italic>q</jats:italic> &lt; 0.8. This suggests that our current understanding of gas kinematics is not sufficient to efficiently apply asymmetric drift corrections to improve dynamical mass estimates compared with observations lacking the signal-to-noise ratio required for spatially extended dynamics.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Primordial magnetic fields (PMFs) could explain the large-scale magnetic fields present in the universe. Inflation and phase transitions in the early universe could give rise to such fields with unique characteristics. We investigate the magnetohydrodynamic evolution of these magnetogenesis scenarios with cosmological simulations. We evolve inflation-generated magnetic fields either as (i) uniform (homogeneous) or as (ii) scale-invariant stochastic fields, and phase-transition-generated ones either as (iii) helical or as (iv) nonhelical fields from the radiation-dominated epoch. We find that the final distribution of magnetic fields in the simulated cosmic web shows a dependence on the initial strength and the topology of the seed field. Thus, the observed field configuration retains information on the initial conditions at the moment of the field generation. If detected, PMF observations would open a new window for indirect probes of the early universe. The differences between the competing models are revealed on the scale of galaxy clusters, bridges, as well as filaments and voids. The distinctive spectral evolution of different seed fields produces imprints on the correlation length today. We discuss how the differences between rotation measures from highly ionized regions can potentially be probed with forthcoming surveys.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A reliable estimate of the redshift distribution <jats:italic>n</jats:italic>(<jats:italic>z</jats:italic>) is crucial for using weak gravitational lensing and large-scale structures of galaxy catalogs to study cosmology. Spectroscopic redshifts for the dim and numerous galaxies of next-generation weak-lensing surveys are expected to be unavailable, making photometric redshift (photo-<jats:italic>z</jats:italic>) probability density functions (PDFs) the next best alternative for comprehensively encapsulating the nontrivial systematics affecting photo-<jats:italic>z</jats:italic> point estimation. The established stacked estimator of <jats:italic>n</jats:italic>(<jats:italic>z</jats:italic>) avoids reducing photo-<jats:italic>z</jats:italic> PDFs to point estimates but yields a systematically biased estimate of <jats:italic>n</jats:italic>(<jats:italic>z</jats:italic>) that worsens with a decreasing signal-to-noise ratio, the very regime where photo-<jats:italic>z</jats:italic> PDFs are most necessary. We introduce Cosmological Hierarchical Inference with Probabilistic Photometric Redshifts (<jats:sc>CHIPPR</jats:sc>), a statistically rigorous probabilistic graphical model of redshift-dependent photometry that correctly propagates the redshift uncertainty information beyond the best-fit estimator of <jats:italic>n</jats:italic>(<jats:italic>z</jats:italic>) produced by traditional procedures and is provably the only self-consistent way to recover <jats:italic>n</jats:italic>(<jats:italic>z</jats:italic>) from photo-<jats:italic>z</jats:italic> PDFs. We present the <jats:monospace>chippr</jats:monospace> prototype code, noting that the mathematically justifiable approach incurs computational cost. The <jats:sc>CHIPPR</jats:sc> approach is applicable to any one-point statistic of any random variable, provided the prior probability density used to produce the posteriors is explicitly known; if the prior is implicit, as may be the case for popular photo-<jats:italic>z</jats:italic> techniques, then the resulting posterior PDFs cannot be used for scientific inference. We therefore recommend that the photo-<jats:italic>z</jats:italic> community focus on developing methodologies that enable the recovery of photo-<jats:italic>z</jats:italic> likelihoods with support over all redshifts, either directly or via a known prior probability density.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Power spectra of spatial fluctuations of X-ray emission may impose constraints on the origins of the emission independent of that from the energy spectra. We generated spatial power spectrum densities (PSDs) of blank X-ray skies observed with the Suzaku X-ray observatory utilizing the modified Δ-variance method. Using the total measured count rate as the diagnostic tool, we found that a model consisting of the sum of two components, one for the unresolved faint point sources and one for the uniform flat-field emission, can represent well the observed PSD in three different energy bands (0.2–0.5, 0.5–2, and 2–10 keV); only an upper limit is obtained for the latter component in 2–10 keV. X-ray counting rates corresponding to the best-fit PSD model functions and diffuse emission fractions were estimated, and we confirmed that the sum of the counting rates of two model components is consistent with those actually observed with the detector for all energy bands. The ratio of the flat-field counting rate to the total in 0.5–2 keV, however, is significantly larger than the diffuse emission fraction estimated from the model fits of energy spectra. We discussed that this discrepancy can be reconciled by systematic effects in the PSD and energy spectrum analyses. The present study demonstrates that the spatial power spectrum analysis is powerful in constraining the origins of the X-ray emission.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Presolar stardust grains found in primitive meteorites are believed to retain the isotopic composition of stellar outflows at the time of grain condensation. Therefore, laboratory measurements of their isotopic ratios represent sensitive probes for investigating open questions related to stellar evolution, stellar explosions, nucleosynthesis, mixing mechanisms, dust formation, and galactic chemical evolution. For a few selected presolar grains, classical novae have been discussed as a potential source. For SiC, silicate, and graphite presolar grains, the association is based on the observation of small <jats:italic>N</jats:italic>(<jats:sup>12</jats:sup>C)/<jats:italic>N</jats:italic>(<jats:sup>13</jats:sup>C) and <jats:italic>N</jats:italic>(<jats:sup>14</jats:sup>N)/<jats:italic>N</jats:italic>(<jats:sup>15</jats:sup>N) number abundance ratios compared to solar values, and abundance excesses in <jats:sup>30</jats:sup>Si relative to <jats:sup>29</jats:sup>Si, as previously predicted by models of classical novae. We report on a direct measurement of the <jats:sup>29</jats:sup>Si(p,<jats:italic>γ</jats:italic>)<jats:sup>30</jats:sup>P reaction, which strongly impacts simulated <jats:italic>δ</jats:italic> <jats:sup>29</jats:sup>Si values from classical novae. Our new experimental <jats:sup>29</jats:sup>Si(p,<jats:italic>γ</jats:italic>)<jats:sup>30</jats:sup>P thermonuclear reaction rate differs from previous results by up to 50% in the classical nova temperature range (<jats:italic>T</jats:italic> = 100–400 MK), while the rate uncertainty is reduced by up to a factor of 3. Using our new reaction rate in Monte Carlo reaction network and hydrodynamic simulations of classical novae, we estimate <jats:italic>δ</jats:italic> <jats:sup>29</jats:sup>Si values with much reduced uncertainties. Our results establish <jats:italic>δ</jats:italic> <jats:sup>29</jats:sup>Si values measured in presolar grains as a sensitive probe for assessing their classical nova paternity. We also demonstrate that <jats:italic>δ</jats:italic> <jats:sup>30</jats:sup>Si values from nova simulations are currently not a useful diagnostic tool unless the large uncertainty of the <jats:sup>30</jats:sup>P(p,<jats:italic>γ</jats:italic>)<jats:sup>31</jats:sup>S reaction rate can be significantly reduced.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We present an optical/near-IR survey of 11 variable young stars (EXors and EXor candidates) aimed at deriving and monitoring their accretion properties. About 30 optical and near-infrared spectra (<jats:inline-formula> <jats:tex-math> <?CDATA ${\mathfrak{R}}\sim 1500\mbox{--}2000$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="fraktur">R</mml:mi> <mml:mo>∼</mml:mo> <mml:mn>1500</mml:mn> <mml:mo>–</mml:mo> <mml:mn>2000</mml:mn> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5a49ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>) were collected between 2014 and 2019 with the Large Binocular Telescope (LBT). From the spectral analysis we have derived the accretion luminosity (<jats:italic>L</jats:italic> <jats:sub>acc</jats:sub> ) and mass accretion rate (<jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{M}}_{\mathrm{acc}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>acc</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5a49ieqn2.gif" xlink:type="simple" /> </jats:inline-formula> ), the visual extinction (<jats:italic>A</jats:italic> <jats:sub>V</jats:sub>), the temperature and density of the permitted line formation region (<jats:italic>T</jats:italic>, <jats:italic>n</jats:italic> <jats:sub>H</jats:sub>), and the signature of the outflowing matter. Two sources (ASASSN-13db and iPTF15afq) have been observed in outburst and quiescence, three during a high level of brightness (XZ Tau, PV Cep, and NY Ori), and the others in quiescence. These latter have <jats:italic>L</jats:italic> <jats:sub>acc</jats:sub> and <jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{M}}_{\mathrm{acc}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>acc</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5a49ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> in line with the values measured in classical T Tauri stars of similar mass. All sources observed more than once present <jats:italic>L</jats:italic> <jats:sub>acc</jats:sub> and <jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{M}}_{\mathrm{acc}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>acc</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5a49ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> variability. The most extreme case is ASASSN-13db, for which <jats:inline-formula> <jats:tex-math> <?CDATA ${\dot{M}}_{\mathrm{acc}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>M</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>̇</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>acc</mml:mi> </mml:mrow> </mml:msub> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjac5a49ieqn5.gif" xlink:type="simple" /> </jats:inline-formula> decreases by two orders of magnitude from the outburst peak in 2015 to quiescence in 2017. Also, in NY Ori <jats:italic>L</jats:italic> <jats:sub>acc</jats:sub> decreases by a factor 25 in one year. In 80% of the sample we detect the [O <jats:sc>i</jats:sc>] 6300 Å line, a tracer of mass loss. From the variability of the H<jats:italic>α</jats:italic>/[O <jats:sc>i</jats:sc>] 6300 Å ratio, we conclude that mass accretion variations are larger than mass loss variations. From the analysis of the H <jats:sc>i</jats:sc> recombination lines, a correlation is suggested between the density of the line formation region, and the level of accretion activity of the source.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We have used the Shanghai Tianma Radio Telescope to search for three OH transitions at 4.7 GHz toward 155 northern star formation regions. We detect 4.7 GHz OH masers in 18 star formation regions, 8 of which are reported here for the first time. From these 18 sources, we detect 6 4660 MHz masers, 13 4765 MHz masers, and no 4750 MHz masers. A further 1 source (Sgr B2N) has been re-detected with broad quasi-thermal emission in all three OH lines. W49SW was re-detected with broad quasi-thermal emission at both 4660 and 4750 MHz. One source (W31, G010.626−0.387) was re-detected with quasi-thermal emission at both 4750 and 4765 MHz. One source (G005.885−0.392) was first detected with quasi-thermal emission at 4660 MHz. We have investigated the associations between the detected 4.7 GHz OH masers with ground-state OH masers near 1.7 GHz, 6.7 GHz methanol masers and 22 GHz water masers reported in the literature. We find that the presence of 1665 MHz OH masers is a better indicator of the presence of 4.7 GHz OH masers than 1720 MHz OH masers. The majority of the 4.7 GHz OH masers are associated with 6.7 GHz methanol and/or 22 GHz water masers. We have compared the characteristics of our detections with those reported previously in the literature and found that only five sources are fairly stable.</jats:p>