Radio Telescope Research Articles

MIGHTEE-H i: deep spectral line observations of the COSMOS field

ABSTRACT The MIGHTEE survey utilizes the South African MeerKAT radio telescope to observe four extragalactic deep fields, with the aim of advancing our understanding of the formation and evolution of galaxies across cosmic time. MIGHTEE’s frequency coverage encompasses the $\textrm {H}\scriptstyle \mathrm{I}$ line to a redshift of z $\simeq$ 0.58, and OH megamasers to z $\simeq$ 0.9. We present the MIGHTEE-$\textrm {H}\scriptstyle \mathrm{I}$ imaging products for the COSMOS field, using a total of 94.2 h on-target and a close-packed mosaic of 15 individual pointings. The spectral imaging covers two broad, relatively interference-free regions (960–1150 and 1290–1520 MHz) within MeerKAT’s L-band, with up to 26 kHz spectral resolution (5.5 km s$^{-1}$ at z = 0). The median noise in the highest spectral resolution data is 74 μJy beam$^{-1}$, corresponding to a 5$\sigma$$\textrm {H}\scriptstyle \mathrm{I}$ mass limit of 10$^{8.5}$ M$_{\odot }$ for a 300 km s$^{-1}$ line at z = 0.07. The mosaics cover $\gt $4 deg$^{2}$, provided at multiple angular resolution / sensitivity pairings, with an angular resolution for $\textrm {H}\scriptstyle \mathrm{I}$ at z = 0 of 12 arcsec. We describe the spectral line processing workflow that will be the basis for future MIGHTEE-$\textrm {H}\scriptstyle \mathrm{I}$ products, and validation of, and some early results from, the spectral imaging of the COSMOS field. We find no evidence for line emission at the position of the z = 0.376 $\textrm {H}\scriptstyle \mathrm{I}$ line reported from the CHILES survey at a $\gt $94 per cent confidence level, placing a 3$\sigma$ upper limit of 8.1 $\times$ 10$^{9}$ M$_{\odot }$ on $M_{\mathrm{HI}}$ for this galaxy. A public data release accompanies this article.

Survey of complex organic molecules in starless and pre-stellar cores in the Perseus molecular cloud

ABSTRACT Cold ($\sim$10 K) and dense ($\sim 10^{5}$ cm$^{-3}$) cores of gas and dust within molecular clouds, known as starless and dynamically evolved pre-stellar cores, are the birthplaces of low-mass (M$\le$ few M$_\odot$) stars. As detections of interstellar complex organic molecules, or COMs, in starless cores has increased, abundance comparisons suggest that some COMs might be seeded early in the star formation process and inherited to later stages (i.e. protostellar discs and eventually comets). To date observations of COMs in starless cores have been limited, with most detections reported solely in the Taurus molecular cloud. It is therefore still a question whether different environments affect abundances. We have surveyed 35 starless and pre-stellar cores in the Perseus molecular cloud with the Arizona Radio Observatory (ARO) 12 m telescope detecting both methanol, CH$_3$OH, and acetaldehyde, CH$_3$CHO, in 100 per cent and 49 per cent of the sample, respectively. In the sub-sample of 15 cores where CH$_3$CHO was detected at $\gt 3\sigma$ ($\sim$18 mK) with the ARO 12 m, follow-up observations with the Yebes 40 m telescope were carried out. Detections of formic acid, t-HCOOH, ketene, H$_2$CCO, methyl cyanide, CH$_3$CN, vinyl cyanide, CH$_2$CHCN, methyl formate, HCOOCH$_3$, and dimethyl ether, CH$_3$OCH$_3$, are seen in at least 20 per cent of the cores. We discuss detection statistics, calculate column densities, and compare abundances across various stages of low-mass star formation. Our findings have more than doubled COM detection statistics in cold cores and show COMs are prevalent in the gas before star and planet formation in the Perseus molecular cloud.

Scientific preparation for JRT: Wind pressure prediction model for large radio telescope based on real data from multi-sensors

Jingdong 120-meter radio telescope (JRT) is poised to become the world's largest single-aperture fully steerable medium-low frequency radio telescope. However, like other large-aperture radio telescopes, the JRT is vulnerable to wind loads, which can cause structural deformation and pointing errors. Addressing this challenge requires the ability to predict dynamic winds in real-time. This study developed a wind pressure preprocessing and prediction model using sensor data collected from the Kunming 40-meter radio telescope (KRT), enabling real-time prediction of wind pressure on the telescope. The model employs adaptive noise and Variational Mode Decomposition (VMD) techniques to eliminate random noise from the original wind pressure data. Subsequently, wind pressure predictions are made using a Bidirectional Long Short-term Memory (BiLSTM) model. By conducting predictions under various stabilization conditions and conducting a thorough analysis of measurement data from five sensors, the study has achieved impressive results in predicting wind pressure on the KRT reflector surface. The proposed model demonstrates the lowest MAE, RMSE, and MAPE, while achieving the highest R2 across various data sets. Where the average R2 of the proposed model is 0.9392 at 45° pitch angle attitude and the RMSE, MAE and MAPE values are 1.4923, 1.2377 and 1.82% respectively. This model helps wind load monitoring of real-time wind pressure monitoring of the telescope surface, to study the effects of wind load on pointing accuracy. By adjusting the control parameters to reduce wind load interference, to ensure the high-precision work of a large radio telescope, such as JRT.

A global view on star formation: The GLOSTAR Galactic plane survey

Context. The GLObal view on STAR formation in the Milky Way (GLOSTAR) survey studies star formation with the Very Large Array (VLA) and the Effelsberg 100 meter radio telescope in the Galactic plane between −2° < ℓ < 60° and |b| < 1°, and the Cygnus X region (76° < ℓ < 83° and −1° < b < 2°), with unprecedented sensitivity in both flux density (1σ ~50 μJy beam−1) and the capability of detecting emission with angular scales in the range from 1.″0 to the largest radio structures in the Galaxy on the order of a few degrees in size. Aims. Here, we provide a complete GLOSTAR-VLA D-configuration radio source catalog for the part of the Galactic disk covered. A catalog for the “pilot region” between 28° < ℓ < 36° has been published in a previous paper and here we present the complementary catalog for the area within 2° < ℓ < 28°, 36° < ℓ < 60° and |b| < 1°. Methods. Observations were taken with the VLA in a 4–8 GHz band to image 100 square degrees of the inner Galactic disk at a reference frequency of 5.8 GHz, using a total of 260 h of telescope time. We determined spectral indices (α; Sν ∝ να) inside the observed band and in the frequency range of 1.4–5.8 GHz by complementing our results with those from The HI/OH/Recombination line survey of the inner Milky Way (THOR), which covers 1–2 GHz. Results. The final images have an angular resolution of 18″ and an average sensitivity of 123 μJy beam−1. The sensitivity is better (~60 μJy beam−1) in areas free of extended emission. The complementary Galactic disk catalog presented in this work consists of 11 211 radio sources. Of these, 1965 are known large-scale structure sources such as star-forming region complexes, well-known supernova remnants (SNRs), SNR candidates, or parts thereof. The remaining 9227 are discrete individual sources. Source parameters–namely flux densities, sizes, spectral indices, and classifications-are reported. We identify 769 H II region candidates, 359 of which have been newly classified as such. The mean value of spectral indices of 225 H II regions is +0.14 ± 0.02, consistent with most of them emitting optically thin thermal radio emission. Combining our results with the previously published catalog of the pilot region, the final GLOSTAR-VLA D-configuration catalog contains 12 981 radio sources.

LOFAR PL610 Station Data Product Specification

ABSTRACT Since 2017, the Space Research Centre of the Polish Academy of Sciences in Warsaw, Poland, has measured and gathered over 35,000 hours of observations with the use of the LOw Frequency ARray (LOFAR) radio telescope. This paper outlines the Standard Data Product acquired from the LOFAR PL610 station located in Borówiec, Poland. Within this context, we detail the data products that are accessible, provide metadata descriptions for them, and include an example of the data under both quiet and disturbed ionospheric conditions.

Improving Radio Signal from Baghdad University Radio Telescope Using the Savitzky-Golay Filter

Astronomical radio observations from a small radio telescope suffer from various types of noise. Hence, astronomers continuously search for new techniques to eliminate or reduce such noise and obtain more accurate results. This research investigates the impact of implementing the Savitzky-Golay filter on enhancing radio observation signals retrieved from the Baghdad University Radio Telescope (BURT). Observations from BURT were carried out for different Galactic coordinates, and then a MATLAB code was written and used to implement the Savitzky-Golay filter for the collected data. This process provides an assessment of the ability of the filter to reduce noise and improve the quality of the signal. The results of this research clearly showed that applying the Savitzky-Golay filter reduces the noise and enhances the signal of astronomical radio observations. However, the filter should be used appropriately to preserve the original features of the signal. In conclusion, the filter is considered an efficient tool for enhancing the radio signal by reducing the noise and smoothing the signal. Therefore, the filter provides a substantial contribution and improvement to the field of radio astronomy.

Comparison of NH3 and 12CO, 13CO, C18O Molecular Lines in the Aquila Rift Cloud Complex

The observations of the Aquila Rift cloud complex at 23.708 and 115.271 GHz made using the Nanshan 26 m radio telescope and the 13.7 m millimeter-wavelength telescope are presented. We find that the CO(1 − 0) gas distribution is similar to the NH3 gas distribution in the Aquila Rift cloud complex. In some diffusion regions characterized by CO, we identified several dense clumps based on the distribution of detected ammonia molecular emission. Through the comparison of spectral line parameters for NH3, 13CO, and C18O, our study reveals that the line center velocities of the NH3, 13CO, and C18O lines are comparable and positively correlated, indicating that they originate from the same emission region. No significant correlation was identified for other parameters, including integrated intensity, line widths, main beam brightness temperature, as well as the column densities of NH3, 13CO, and C18O. The absolute difference in line-center velocities between the 13CO and NH3 lines is less than both the average line width of NH3 and that of 13CO. This suggests that there are no significant movements of NH3 clumps in relation to their envelopes. The velocity deviation is likely due to turbulent activity within the clumps.

A power spectrum approach to the search for axion-like particles from resolved galaxy clusters using CMB as a backlight

Axions or axion-like particles (ALPs) are hypothetical particles predicted by beyond standard model theories, which make one of the dark matter candidates. These particles can convert into photons and vice-versa in the presence of a magnetic field, with a probability decided by its coupling strength gaγ . One of the ways to detect these particles is by using the Cosmic Microwave Background (CMB) as a backlight. As the CMB photons pass through a galaxy cluster, they can get converted into ALPs in the mass range 10-15 eV to 10-11 eV through resonant conversion in the presence of cluster magnetic fields. This leads to a polarized spectral distortion (α-distortion) in the CMB as the photon polarization parallel to the magnetic field in the galaxy cluster is involved in the conversion. The fluctuations in the magnetic field and electron density in a galaxy cluster lead to spatially varying α-distortion around the cluster, with a power spectrum that is different from the lensed E-mode and B-mode CMB polarization power spectrum for the standard model of cosmology. By measuring the difference in the polarization power spectrum around a galaxy cluster from the all-sky signal, one can find new α-distortion in the sky. For the resolved galaxy clusters, if the redshift, electron density, and magnetic field profiles of the cluster can be constrained using optical, X-ray, and radio observations, one can measure the coupling strength gaγ from the ALP power spectrum. The contamination from CMB and galactic foregrounds such as synchrotron and dust can be mitigated by using multiple frequency bands by leveraging on the difference in the spectral shape of the signal from foregrounds. Using the ILC technique to clean the foregrounds, we show that the new power spectrum-based approach of the resolved galaxy clusters from upcoming CMB experiments such as Simons Observatory and CMB-S4 can detect (or put constraints) on the ALP-photon coupling strength of gaγ < 5.2 × 10-12 GeV-1 and gaγ < 3.6 × 10-12 GeV-1 at 95% C.I. respectively for ALPs of masses 10-13 eV or for smaller gaγ for lighter ALP masses.

Astrometry and Precise Radial Velocities Yield a Complete Orbital Solution for the Nearby Eccentric Brown Dwarf LHS 1610 b

The LHS 1610 system consists of a nearby (d = 9.7 pc) M5 dwarf hosting a candidate brown dwarf companion in a 10.6 days, eccentric (e ∼ 0.37) orbit. We confirm this brown dwarf designation and estimate its mass ( 49.5−3.5+4.3 M Jup) and inclination (114.5° −10.0+7.4 ) by combining discovery radial velocities (RVs) from the Tillinghast Reflector Echelle Spectrograph and new RVs from the Habitable-zone Planet Finder with the available Gaia astrometric two-body solution. We highlight a discrepancy between the measurement of the eccentricity from the Gaia two-body solution (e = 0.52 ± 0.03) and the RV-only solution (e = 0.3702 ± 0.0003). We discuss possible reasons for this discrepancy, which can be further probed when the Gaia astrometric time series become available as part of Gaia Data Release 4. As a nearby mid-M star hosting a massive short-period companion with a well-characterized orbit, LHS 1610 b is a promising target to look for evidence of sub-Alfvénic interactions and/or auroral emission at optical and radio wavelengths. LHS 1610 has a flare rate (0.28 ± 0.07 flares per day) on the higher end for its rotation period (84 ± 8 days), similar to other mid-M dwarf systems such as Proxima Cen and YZ Ceti that have recent radio detections compatible with star–planet interactions. While available Transiting Exoplanet Survey Satellite photometry is insufficient to determine an orbital phase dependence of the flares, our complete orbital characterization of this system makes it attractive to probe star–companion interactions with additional photometric and radio observations.

Resolving a Candidate Dual Active Galactic Nucleus with ∼100 pc Separation in MCG-03-34-64

We report the serendipitous multiwavelength discovery of a candidate dual black hole system with a separation of ∼100 pc, in the gas-rich luminous infrared galaxy MCG-03-34-64 (z = 0.016). Hubble Space Telescope/Advanced Camera for Surveys observations show three distinct optical centroids in the [O iii] narrow-band and F814W images. Subsequent analysis of Chandra/ACIS data shows two spatially resolved peaks of equal intensity in the neutral Fe Kα (6.2–6.6 keV) band, while high-resolution radio continuum observations with the Very Large Array at 8.46 GHz (3.6 cm band) show two spatially coincident radio peaks. Fast shocks as the ionizing source seem unlikely, given the energies required for the production of Fe Kα. If confirmed, the separation of ∼100 pc would represent the closest dual active galactic nuclei reported to date with spatially resolved, multiwavelength observations.

A spatially resolved radio spectral study of the galaxy M 51

Context. Radio continuum emission from galaxies at gigahertz frequencies can be used as an extinction-free tracer of star formation. However, at frequencies of a few hundred megahertz, there is evidence for low-frequency spectral flattening. Aims. We wish to understand the origin of this low-frequency flattening better, and to this end, we performed a spatially resolved study of the nearby spiral galaxy M51. We explored the different effects that can cause a flattening of the spectrum towards lower frequencies, such as free–free absorption and cosmic-ray ionisation losses. Methods. We used radio continuum intensity maps between 54 and 8350 MHz at eight different frequencies, with observations at 240 MHz from the Giant Metrewave Radio Telescope presented for the first time. We corrected for the contribution from thermal free–free emission using an H α map that was corrected for extinction with 24 μm data. We fitted free–free absorption models to the radio spectra to determine the emission measure (EM) as well as polynomial functions to measure the non-thermal spectral curvature. We also obtained a new extinction-corrected H α intensity map from the Metal-THINGS survey using integral field unit spectroscopy. Results. The non-thermal low-frequency radio continuum spectrum between 54 and 144 MHz is very flat and even partially inverted, particularly in the spiral arms; in contrast, the spectrum at higher frequencies is typical for a non-thermal radio continuum spectrum. However, we did not find any correlation between the EMs calculated from radio and from H α observations; instead, the non-thermal spectral curvature weakly correlates with the H I gas-mass surface density. This suggests that cosmic-ray ionisation losses play an important role in the low-frequency spectral flattening. Conclusions. The observed spectral flattening towards low frequencies in M51 is caused by a combination of ionisation losses and free–free absorption. The reasons for this flattening need to be understood in order to use sub-gigahertz frequencies as a tracer of star formation.

FAST Ultra-Deep Survey: Data Release for FUDS0

We have used the Five-hundred-meter Aperture Spherical radio Telescope (FAST) to conduct a blind ultradeep survey for neutral hydrogen (H i). We present the complete results from the first of six fields (FUDS0). These observations of 95 hr allowed us to achieve a high-sensitivity (∼50 μJy beam−1) and a high-frequency resolution (22.9 kHz) over an area of 0.72 deg2. We detected 128 galaxies in H i distributed over the redshift range of 0 < z < 0.4, with H i masses in the range of 6.67≤log(MHI/h70−2M⊙)≤10.92 , and three faint high-velocity clouds, with a peak column density of N H i ≤ 3.1 × 1017 cm−2. Of the galaxies, 95 are new detections and six have z > 0.38, where no unlensed H i emission has previously been directly detected. Estimates of completeness and reliability are presented for the catalog. The consistency of continuum and H i flux estimates with the NRAO VLA Sky Survey and the Arecibo Ultra-Deep Survey, respectively, confirms the accuracy of the calibration method and data reduction pipeline developed for the full FAST Ultra-Deep Survey.

Timing of Millisecond Pulsars in NGC 6752. III. On the Presence of Nonluminous Matter in the Cluster’s Core

Millisecond pulsars are subject to accelerations in globular clusters (GCs) that manifest themselves in both the first and second spin period time derivatives, and can be used to explore the mass distribution of the potentials they inhabit. Here we report on over 20 yr of pulsar timing observations of five millisecond radio pulsars in the core of the core-collapse GC NGC 6752 with the Parkes (Murriyang) and MeerKAT radio telescopes, which have allowed us to measure the proper motions, positions, and first and second time derivatives of the pulsars. The pulsar timing parameters indicate that all the pulsars in the core experience accelerations and jerks that can be explained only if an amount of nonluminous mass of at least 2.56 × 103 M ⊙ is present in the core of NGC 6752. On the other hand, our studies highly disfavor the presence of an intermediate-mass black hole at the center of the cluster, with a mass equal to or greater than ∼3000M ⊙.

Bright unintended electromagnetic radiation from second-generation Starlink satellites

We report on the detection of unintended electromagnetic radiation (UEMR) from the second-generation of Starlink satellites. Observations with the LOFAR radio telescope between 10 to 88 MHz and 110 to 188 MHz show broadband emission covering the frequency ranges from 40 to 70 MHz and 110 to 188 MHz from the v2-Mini and v2-Mini Direct-to-Cell Starlink satellites. The spectral power flux density of this broadband UEMR varies from satellite to satellite, with values ranging from 15 to 1300 Jy, between 56 and 66 MHz, and from 2 to 100 Jy over two distinct 8 MHz frequency ranges centered at 120 and 161 MHz. We compared the detected power flux densities of this UEMR to that emitted by the first generation v1.0 and v1.5 Starlink satellites. When correcting for the observed satellite distances, we find that the second-generation satellites emit UEMR that is up to a factor of 32 stronger compared to the first generation. The calculated electric field strengths of the detected UEMR exceed typical electromagnetic compatibility standards used for commercial electronic devices as well as recommended emission thresholds from the Radiocommunication Sector of the International Telecommunications Union (ITU-R) aimed at protecting the 150.05–153 MHz frequency range allocated to radio astronomy. We characterize the properties of the detected UEMR with the aim of assisting the satellite operator with the identification of the cause of the UEMR.

The Formation of Milky Way “Bones”: Ubiquitous HI Narrow Self-absorption Associated with CO Emission

Long and skinny molecular filaments running along Galactic spiral arms are known as “bones,” since they make up the skeleton of the Milky Way. However, their origin is still an open question. Here, we compare spectral images of HI taken by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) with archival CO and Herschel dust emission to investigate the conversion from HI to H2 in two typical Galactic bones, CFG028.68-0.28 and CFG047.06+0.26. Sensitive FAST HI images and an improved methodology enabled us to extract HI narrow self-absorption (HINSA) features associated with CO line emission on and off the filaments, revealing the ubiquity of HINSA toward distant clouds for the first time. The derived cold HI abundances, [HI]/[H2], of the two bones range from ∼(0.5 to 44.7) × 10−3, which reveal different degrees of HI–H2 conversion, and are similar to those of nearby, low-mass star-forming clouds, Planck Galactic cold clumps, and a nearby active high-mass star-forming region G176.51+00.20. The HI–H2 conversion has been ongoing for 2.2–13.2 Myr in the bones, a timescale comparable to that of massive star formation therein. Therefore, we are witnessing young giant molecular clouds (GMCs) with rapid massive star formation. Our study paves the way of using HINSA to study cloud formation in Galactic bones and, more generally, in distant GMCs in the FAST era.

Results of the follow-up of ANTARES neutrino alerts

High-energy neutrinos could be produced in the interaction of charged cosmic rays with matter or radiation surrounding astrophysical sources. To look for transient sources associated with neutrino emission, a follow-up program of neutrino alerts has been operating within the ANTARES collaboration since 2009. This program, named TAToO, has triggered robotic optical telescopes (MASTER, TAROT, ROTSE and the SVOM ground based telescopes) immediately after the detection of any relevant neutrino candidate and scheduled several observations in the weeks following the detection. A subset of ANTARES events with highest probabilities of being of cosmic origin has also been followed by the Swift and the INTEGRAL satellites, the Murchison Widefield Array radio telescope and the H.E.S.S. high-energy gamma-ray telescope. The results of twelve years of observations are reported. In September 2015, ANTARES issued a neutrino alert and during the follow-up, a potential transient counterpart was identified by Swift and MASTER. A multi-wavelength follow-up campaign has allowed to identify the nature of this source and has proven its fortuitous association with the neutrino. No other optical and X-ray counterpart has been significantly associated with an ANTARES candidate neutrino signal. Constraints on transient neutrino emission have been set. The return of experience is particularly important for the design of the alert system of KM3NeT, the next generation neutrino telescope in the Mediterranean Sea.

Extended CO(1–0) survey and ammonia measurements towards two bubble regions in W5

The feedback effect of massive stars can either accelerate or inhibit star formation activity within molecular clouds. Studying the morphology of molecular clouds near W5 offers an excellent opportunity to examine this feedback effect. We conducted a comprehensive survey of the W5 complex using the Purple Mountain Observatory 13.7 m millimeter telescope. This survey includes 12CO, 13CO, and C18O (J = 1 − 0), with a sky coverage of 6.6 deg2 (136.0° &lt; l &lt; 138.75°, 0° &lt; b &lt; 2.4°). Furthermore, we performed simultaneous observations of the NH3 (1,1) and NH3 (2,2) lines in the four densest star-forming regions of W5, using the 26 m radio telescope of the Xinjiang Astronomy Observatory (XAO). Our analysis of the morphological distribution of the molecular clouds, distribution of high-mass young stellar objects (HMYSOs), 13CO/C18O abundance ratio, and the stacked average spectral line distribution at different 8 μm thresholds provide compelling evidence of triggering. Within the mapped region, we identified a total of 212 molecular clumps in the 13CO cube data using the astrodendro algorithm. Remarkably, approximately 26.4% (56) of these clumps demonstrate the potential to form massive stars and 42.9% (91) of them are gravitationally bound. Within clumps that are capable of forming high-mass stars, there is a distribution of class I YSOs, all located in dense regions near the boundaries of the HII regions. The detection of NH3 near the most prominent cores reveals moderate kinetic temperatures and densities (as CO). Comparing the Tkin and Tex values reveals a reversal in trends for AFGL 4029 (higher Tex and lower Tkin) and W5-W1, indicating the inadequacy of optically thick CO for dense region parameter calculations. Moreover, a comparison of the intensity distributions between NH3 (1,1) and C18O (1–0) in the four densest region reveals a notable depletion effect in AFGL 4029, characterised by a low Tkin (9 K) value and a relatively high NH3 column density, 2.5 × 1014 cm−2. By classifying the 13CO clumps as: “feedback,” “non-feedback,” “outflow,” or “non-outflow” clumps, we observe that the parameters of the “feedback” and “outflow” clumps exhibit variations based on the intensity of the internal 8 μm flux and the outflow energy, respectively. These changes demonstrate a clear linear correlation, which distinctly separate them from the parameter distributions of the “non-feedback” and “non-outflow” clumps, thus providing robust evidence to support a triggering scenario.

Unveiling Frequency-dependent Eclipsing in Spider Millisecond Pulsars Using Broadband Polarization Observations with the Parkes

This study presents an orbital-phase-dependent analysis of three black widow spider millisecond pulsars (BW MSPs), aiming to investigate the magnetic field within the eclipse environment. The ultrawide-bandwidth low-frequency receiver of the Parkes Murriyang radio telescope is utilized for full polarization observations covering frequencies from 704−4032 MHz. Depolarization of pulsed emission is observed during the eclipse phase of three BW MSPs, namely PSR J0024−7204J, PSR J1431−4715, and PSR J1959+2048, consistent with previous studies of other BW MSPs. We estimated orbital-phase-dependent rotation measure values for these MSPs. The wide bandwidth observations also provided constraints on the eclipse cutoff frequency for these BW MSPs. For PSR J0024−7204J, we report temporal variation of the eclipse cutoff frequency coupled with changes in the electron column density within the eclipse medium across six observed eclipses. Moreover, the eclipse cutoff frequency for PSR J1431−4715 is determined to be 1251 ± 80 MHz, leading to the conclusion that synchrotron absorption is the primary mechanism responsible for the eclipsing. Additionally, for PSR J1959+2048, the estimated cutoff frequency exceeded 1400 MHz, consistent with previous studies. With this investigation, we have doubled the sample size of BW MSPs with orbital-phase-resolved studies, allowing a better probe of the eclipse environment.

Spectral cleaving in solar type II radio bursts: Observations and interpretation

Context. Shock waves in the solar corona are associated with solar flares and coronal mass ejections (CMEs). Type II solar bursts are radio signatures of shock waves in the solar corona. They are driven by solar flares or CMEs. Despite extensive studies, the intricate spectral patterns observed in type II solar bursts occasionally pose new challenges for the theory of electron acceleration in shocks. Aims. We study a newly identified feature in type II solar bursts called spectral cleaving. This feature is characterized by the actual branching of a type II radio emission lane in radio spectral data. Methods. We analyzed the type II burst exhibiting spectral cleaving in high-fidelity dynamic spectra obtained using the URAN-2 radio telescope (8.25–33 MHz; Poltava region, Ukraine) on 2011 February 14. The high-resolution spectrograms were examined to ascertain its spectral morphology. Results. Our research represents the first recognition of spectral cleaving as a peculiarity of type II bursts that is yet to be classified. This effect occurs due to the shift (or migration) of radio source(s) along a shock front, which in turn is caused by changes in the magnetic field orientation ahead of the propagating shock front. Conclusions. The spectral cleaving observed in solar type II bursts reveals a distinct phenomenon that indicates complex interactions between shock waves and magnetic fields in the solar corona. This discovery enhances our understanding of the mechanisms behind solar radio emissions and emphasizes the need for further observational studies to verify these findings.

The factors that influence protostellar multiplicity

Context. Protostellar multiplicity is common at all stages and mass ranges. However, the factors that determine the multiplicity of protostellar systems have not been systematically characterized through their molecular gas. Aims. We characterize the physical properties of the Perseus molecular cloud at ≥5000 AU scales by mapping the diagnostic molecular lines. Methods. We used Nobeyama 45m Radio Observatory (NRO) on-the-fly maps of HCN, HNC, HCO+, and N2H+ (J=1–0) toward five subregions in Perseus, complemented with single-pointing Atacama Pathfinder Experiment (APEX) observations of HNC (J = 4–3), to derive the physical parameters of the dense gas. The spatial resolutions of both observations were ~18″, which is equivalent to ~5000 AU scales at the distance of Perseus. The kinetic gas temperature was derived from the I(HCN)/I(HNC) J ratio, and the H2 density was obtained from the HNC J=4–3/J=1–0 ratio. These parameters were used to obtain the N2H+ (cold) and HCO+ (warm) gas masses. The inferred and derived parameters were then compared to source the parameters, including protostellar multiplicity, bolometric luminosity, and dust envelope mass. Results. The inferred mean kinetic gas temperature (I(HCN)/I(HNC) J=1–0 ratio; ranging between 15 and 26 K), and H2 volumetric density (HNC J=4–3/J=1–0; 105−106 cm−3) are not correlated with multiplicity in Perseus. The derived gas and dust masses, 1.3 to 16 × 10−9 M⊙ for the cold-gas mass (N2H+), 0.1 to 25 M⊙ for the envelope dust masses (850 μm), and 0.8 to 10 × 10−10 M⊙ for the warm-gas mass (HCO+), are correlated to multiplicity and to the number of protostellar components. The warm-gas masses are lower by a factor of 16 than the cold-gas masses. Conclusions. The gas and dust mass is correlated to multiplicity at ~5000 AU scales in Perseus. Higher-order multiples tend to have higher gas and dust masses in general, while close binaries (separations ≤7″) and single protostars have similar gas and dust mass distributions. On the other hand, the H2 density and kinetic gas temperature are not correlated with multiplicity.