arXiv subjects

Josep M. Masqué

Publications and source records attributed to Josep M. Masqué.

16 recordsLinked to original sources

arXiv2026

Dynamical masses of young stellar objects with the VLBA: DYNAMO-VLBA: Radio binary stars in Orion

We present results from a multi-epoch Very Long Baseline Array (VLBA) survey conducted as part of the DYNAMO-VLBA project, aimed at measuring the dynamical masses of young stellar systems in the Orion complex. Our observations include 19 radio sources associated with 15 binary or multiple young systems. For four visual binaries in which both components were detected, the derived Keplerian orbits yield model-independent stellar masses; in particular, Brun~656 and HD~294300 show excellent agreement between VLBA-based and spectral-energy-distribution-based estimates, providing valuable benchmarks for pre-main-sequence evolutionary models. The component NU Ori C is confirmed as an intermediate-mass ($\sim$7\,M$_\odot$) star with nonthermal radio emission, offering rare evidence of magnetic activity near the boundary with the high-mass regime. Several additional sources exhibit astrometric accelerations or periodic residuals, revealing unseen companions and extending dynamical constraints to systems with only one radio-emitting component. These results highlight the capability of very long baseline interferometry astrometry to obtain precise and model-independent masses of young binaries, providing critical empirical anchors for stellar evolution models and new insights into the origin of magnetism in intermediate-mass stars.

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arXiv2026

Dynamical masses of YSOs with the VLBA: DYNAMO VLBA: Trigonometric parallaxes and proper motions of YSOs in Orion

We present results from a multi-epoch Very Long Baseline Array (VLBA) survey of compact radio sources in the Orion complex, conducted within both the DYNAMO-VLBA and the GOBELINS projects. Our observations detected 216 compact radio sources, of which 58 yielded reliable multi-epoch astrometric solutions. For these sources, we derived trigonometric parallaxes and proper motions with typical precisions of about 0.05 mas and 0.10 mas yr$^{-1}$, respectively. The measured parallaxes range between 2.26 and 2.65 mas, corresponding to distances of 380 - 440 pc, and delineate the depth of the Orion star-forming complex. We determine mean distances of $405\pm16$ pc for NGC 2068, $403\pm5$ pc for NGC 2024, $407\pm12$ pc for the $σ$ Orionis region, $388.5\pm1.7$ pc for the Orion Nebula Cluster (ONC), and $438\pm12$ pc for L1641. A comparison with Gaia DR3 astrometry for 28 common sources reveals negligible mean parallax offsets ($Δ\varpi=-0.02\pm0.01$ mas) and small systematic differences in proper motions ($\sim$0.07 mas yr$^{-1}$), likely due to residual rotation of the Gaia reference frame. Our results demonstrate the capability of high-precision radio astrometry to map embedded stellar populations and to provide an independent calibration of the Gaia reference system in obscured regions.

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arXiv2025

Dynamical mass of the Serpens intermediate-mass young stellar system EC\,95 with DYNAMO--VLBA

We present dynamical mass measurements, obtained from multi-epoch Very Long Baseline Interferometry (VLBI) observations, for the young multiple stellar system EC\,95, located in the core of the Serpens star-forming region. Our dataset includes both archival data and more recent observations obtained as part of the \textit{Dynamical Masses of Young Stellar Multiple Systems with the VLBA project} (DYNAMO--VLBA), totalling 32 epochs over 12 years of observation. The observations span more than half of the EC\,95AB orbit, which has an estimated period of $21.6\pm0.1$ years, and yield masses of $2.15\pm0.10$ M$_\odot$ for EC\,95A and $2.00\pm0.12$ M$_\odot$ for EC\,95B. Furthermore, for the first time, we have estimated the mass of the third component (EC\,95C) using four available radio detections as well as an infrared observation. We find it to be 0.26 $^{+0.53}_{-0.46}$ M$_\odot$, suggesting that E\,95C is a low-mass T Tauri star. We conclude that EC\,95 is a hierarchical triple system comprised of a tight central binary proto-Herbig\,AeBe system and a lower mass companion on a wider orbit. These results contribute to improve our understanding of the stellar dynamics in this system and provide valuable insights into its triple nature.

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arXiv2025

VLBA Detections in the Oph-S1 Binary System near Periastron Confirmation of its Orbital Elements and Mass

Oph-S1 is the most luminous and massive stellar member of the nearby Ophiuchus star-forming region. Previous Very Long Baseline Array (VLBA) observations have shown it to be an intermediate-mass binary system ($\sim 5\,{\rm M}_\odot$) with an orbital period of about 21 months, but a paucity of radio detections of the secondary near periastron could potentially have affected the determination of its orbital parameters. Here, we present nine new VLBA observations of Oph-S1 focused on its periastron passage in early 2024. We detect the primary in all observations and the secondary at five epochs, including three within about a month of periastron passage. The updated orbit, determined by combining our new data with 35 previous observations, agrees well with previous calculations and yields masses of $4.115 \pm0.039 \,{\rm M}_\odot$ and $0.814\pm0.006 \,{\rm M}_\odot$ for the two stars in the system.

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arXiv2025

The arc-shaped radio source at the center of NGC 6334A: Is it a colliding wind region of two young massive stars or the bow shock of a runaway star?

New multi-wavelength Karl G. Jansky VLA observations of CKR02A, the compact radio source in the center of the compact HII region NGC 6334A, are presented. The observations were carried out in five epochs and included the frequency ranges 8.0 - 12.0 GHz (X-band), 18.0 - 26.0 GHz (K-band), and 29.0 - 37.0 GHz (Ka-band). The source is detected and resolved in all the observed epochs and in all bands. The source shows a clear arc-shaped structure consistent with a bow shock. The analysis of the spectral index maps indicates that its spectral index is $α=-0.68\pm0.17$, suggesting that the emission is non-thermal. Two astronomical objects can explain the emission nature and morphology of the source: a colliding wind region of two massive stars or the bow shock of a massive runaway star. However, no massive stars are reported so far in the center of NGC 6334A, though its presence is also suggested by the free-free radio emission of the C-HII region itself. Using ancillary VLA data, we measured a preliminary proper motion of $19\pm6$ mas yr$^{-1}$, equivalent to a velocity of $120\pm40$ km s$^{-1}$. A detailed discussion of the implications of both scenarios is provided. Finally, a list of compact radio sources in the vicinity of NGC 6334A is given and briefly discussed.

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arXiv2024

Dynamical mass of the Ophiuchus intermediate-mass stellar system S1 with DYNAMO-VLBA

We report dynamical mass measurements of the individual stars in the most luminous and massive stellar member of the nearby Ophiuchus star-forming region, the young tight binary system S1. We combine 28 archival datasets with seven recent, proprietary VLBA observations obtained as part of the \textit{Dynamical Masses of Young Stellar Multiple Systems with the VLBA} project (DYNAMO--VLBA), to constrain the astrometric and orbital parameters of the system, and recover high accuracy dynamical masses. The primary component, S1A, is found to have a mass of 4.11$\pm$0.10~M$_\odot$, significantly less than the typical value, $\sim$~6~M$_\odot$ previously reported in the literature. We show that the spectral energy distribution of S1A can be reproduced by a reddened blackbody with a temperature between roughly 14,000~K and 17,000~K. According to evolutionary models, this temperature range corresponds to stellar masses between 4~M$_\odot$ and 6~M$_\odot$ so the SED is not a priori inconsistent with the dynamical mass of S1A. The luminosity of S1 derived from SED-fitting, however, is only consistent with models for stellar masses above 5~M$_\odot$. Thus, we cannot reconcile the evolutionary models with the dynamical mass measurement of S1A: the models consistent with the location of S1A in the HR diagram correspond to masses at least 25\% higher than the dynamical mass. For the secondary component, S1B, a mass of 0.831~$\pm$~0.014~M$_\odot $ is determined, consistent with a low-mass young star. While the radio flux of S1A remains roughly constant throughout the orbit, the flux of S1B is found to be higher near the apastron.

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arXiv2023

ALMA Observations of the Extraordinary Carina Pillars: A Complementary Sample

We present a study of six dusty and gaseous pillars (containing the HH 1004 and HH 1010 objects) and globules (that contain the HH 666, HH 900, HH 1006, and HH 1066 objects) localized in the Carina nebula using sensitive and high angular resolution ($\sim$0.3$''$) Atacama Large Millimeter/Sub-millimeter Array (ALMA) observations. This is a more extensive study that the one presented in \citet{Cortes}. As in this former study, we also analyzed the 1.3 mm continuum emission and C$^{18}$O(2$-$1), N$_2$D$^+$(3$-$2) and $^{12}$CO(2$-$1) spectral lines. These new observations revealed the molecular outflows emanating from the pillars, the dusty envelopes$+$disks that are exciting them, and the extended HH objects far from their respective pillars. We reveal that the masses of the disks$+$envelopes are in a range of 0.02 to 0.38 M$_\odot$, and those for the molecular outflows are of the order of 10$^{-3}$ M$_\odot$, which suggests that their exciting sources might be low- or intermediate-mass protostars as already revealed in recent studies at infrared and submillimeter bands. In the regions associated with the objects HH 900 and HH 1004, we report multiple millimeter continuum sources, from where several molecular outflows emanate.

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arXiv2022

The population of compact radio sources in M 17

We present a catalog of radio sources of the M 17 region based on deep X band radio observations centered at 10 GHz obtained with the Jansky Very Large Array in the A configuration. We detect a total of 194 radio sources, 12 of them extended and 182 compact. We find that a significant fraction (at least 40% in our catalog) have suspected gyrosynchrotron emission associated with stellar coronal emission. By comparing the radio luminosities of our sources with their X ray counterparts, when available, we find that they are underluminous in X rays with respect to the Güdel Benz relation, but a correlation with a similar slope is obtained provided that only sources with evident non thermal nature are selected from the sample compiled for the Orion Nebula Cluster (ONC) and M 17. The comparison of M 17 with the ONC and NGC 6334D-F leads to a similar luminosity function for the three regions, at least for the more luminous sources. However, the radio sources in M 17 are three times more numerous compared to the other regions at a given luminosity and their spatial distribution differs from that of Orion. Moreover, an arc-shaped structure of 40$"$ in extent is observed in our map, identified previously as an ionizing front, with the cometary Hyper Compact source UC1 at its focus. Archival 1 mm ALMA data reveals compact emission coincident with the radio wavelength peak, possibly associated with a protostellar disk of the massive star exciting UC1.

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arXiv2020

Exploring the nature of compact radio sources associated to UCHII regions

We present Very Large Array 7 mm continuum observations of four Ultra-Compact (UC)HII regions, observed previously at 1.3 cm, in order to investigate the nature of the compact radio sources associated with these regions. We detected a total of seven compact radio sources, four of them with thermal emission, and two compact radio sources have clear non-thermal emission. The thermal emission is consistent with the presence of an ionized envelope, either static (i.e., trapped in the gravitational radius of an associated massive star) or flowing away (i.e., a photo-evaporative flow). On the other hand, the nature of the non-thermal sources remains unclear and several possibilities are proposed. The possibility that most of these compact radio sources are photo-evaporating objects and the remaining ones more-evolved objects is consistent with previous studies on UCHII regions.

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arXiv2018

GMRT observations of the protostellar jet associated with \iras

We report continuum GMRT observations aimed to explore the behavior of the jet associated with IRAS 16547-4247 at very low frequencies (325 MHz and 610 MHz). The obtained maps reveal an elongated morphology in the SE-NW direction. In addition, the 610 MHz map shows three knots associated to the elongated morphology that seems to correspond to the triple radio source identified as the jet seen at higher frequencies. However, at 325 MHz, although an elongated morphology is also observed, only two knots appear in the map. By comparing our knot positions at both frequencies with a precessing jet model used in a previous work, we find that the knots fall closely to the wiggling path and, hence, they likely represent shocks of the material of the precessing jet with the medium. Only the nature of the southernmost knot detected at 325 MHz remains unclear. Besides, we found that the whole emission of the lobes is non-thermal down to very low frequencies and that the possible associated emission mechanisms work differently in in both lobes, causing the discrepancies between observed frequencies. To explain these discrepancies we investigate mechanisms such as synchrotron radiative losses in a magnetic field of about 0.5 mG in the shocks and find this possibility unlikely to occur. Alternatively, we invoke interaction with an inhomogeneous medium as the most probable scenario.

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arXiv2017

Searching for compact radio sources associated to UCHII regions

Ultra-Compact (UC)HII regions represent a very early stage of massive star formation whose structure and evolution are not yet fully understood. Interferometric observations in recent years show that some UCHII regions have associated compact sources of uncertain nature. Based on this, we carried out VLA 1.3 cm observations in the A configuration of selected UCHII regions in order to report additional cases of compact sources embedded in UCHII regions. From the observations, we find 13 compact sources associated to 9 UCHII regions. Although we cannot establish an unambiguous nature for the newly detected sources, we assess some of their observational properties. According to the results, we can distinguish between two types of compact sources. One type corresponds to sources that probably are deeply embedded in the dense ionized gas of the UCHII region. These sources are being photo-evaporated by the exciting star of the region and will last for 10$^4-10^5$ yr. They may play a crucial role in the evolution of the UCHII region as the photo-evaporated material could replenish the expanding plasma and might provide a solution to the so-called lifetime problem for these regions. The second type of compact sources is not associated with the densest ionized gas of the region. A few of these sources appear resolved and may be photo-evaporating objects such as those of the first type but with significantly lower mass depletion rates. The rest of sources of this second type appear unresolved and their properties are varied. We speculate on the similarity between the sources of the second type and those of the Orion population of radio sources.

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arXiv2015

Proper motions of the outer knots of the HH 80/81/80N radio-jet

(abridged) The HH 80/81/80N jet extends from the HH 80 object to the recently discovered Source 34 and has a total projected jet size of 10.3 pc, constituting the largest collimated radio-jet system known so far. It is powered by IRAS 18162-2048 associated with a massive young stellar object. We report 6 cm JVLA observations that, compared with previous 6 cm VLA observations carried out in 1989, allow us to derive proper motions of the HH 80, HH 81 and HH 80N radio knots located about 2.5 pc away in projection from the powering source. For the first time, we measure proper motions of the optically obscured HH 80N object providing evidence that HH 81, 80 and 80N are associated with the same radio-jet. We derived tangential velocities of these HH objects between 260 and 350 km/s, significantly lower than those for the radio knots of the jet close to the powering source (600-1400 km/s) derived in a previous work, suggesting that the jet material is slowing down due to a strong interaction with the ambient medium. The HH 80 and HH 80N emission at 6 cm is, at least in part, probably synchrotron radiation produced by relativistic electrons in a magnetic field of 1 mG. If these electrons are accelerated in a reverse adiabatic shock, we estimate a jet total density of $\lesssim1000$ cm$^{-3}$. All these features are consistent with a jet emanating from a high mass protostar and make evident its capability of accelerating particles up to relativistic velocities.

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arXiv2013

New Radio Continuum Observations of the Compact Source Projected Inside NGC 6334A

A handful of HII regions are known to exhibit a compact radio source near their centers. The nature of these compact radio sources is not well established. We present the analysis of new as well as archival Very Large Array observations of the compact source projected near the center of the NGC 6334A HII region, part of the NGC 6334 complex. We show that the compact source is time variable on a scale of years and determine for one epoch a non-thermal spectrum, suggestive of synchrotron emission. We propose that this source could be the wind interaction region of a massive binary system that could be the ionizing source of NGC 6334A.

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arXiv2013

Interferometric observations of nitrogen-bearing molecular species in the star-forming core ahead of HH 80N

We present VLA NH3 and PdBI NH2D and H13NC observations of the star forming core ahead of HH 80N, the optically obscured northern counterpart of the Herbig-Haro objects HH 80/81. The main goal is to determine the kinematical information of the high density regions of the core ($n\lesssim 10^5$ cm$^{-3}$), missed in previous works due to the depletion of the species observed (e.g. CS). The obtained maps show different kinematical signatures between the eastern and western parts of the core, suggesting a possible dynamical interaction of the core with the HH 80/81/80N outflow. The analysis of the Position-Velocity (PV) plots of these species rules out a previous interpretation of having a molecular ring-like structure of $6\times 10^4$ AU of radius traced by CS infalling onto a central protostar found in the core (IRS1). High degree of deuteration, with respect to the central part of the core harboring IRS1, is derived in the eastern part, where a dust condensation (SE) is located. This deuteration trend of NH3 suggests that SE is in a prestellar evolutionary stage, earlier than that of the IRS1. Since SE is the closest condensation to the HH 80N/81/80N outflow, in case of having outflow-core dynamical interaction, it should be perturbed first and be the most evolved condensation in the core. Therefore, the derived evolutionary sequence for SE and IRS1 makes the outflow triggered star formation on IRS1 unlikely.

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arXiv2012

Centimeter continuum observations of the northern head of the HH 80/81/80N jet: revising the actual dimensions of a parsec scale jet

We present 6 and 20 cm JVLA/VLA observations of the northern head of the HH 80/81/80N jet, one of the largest collimated jet systems known so far, aimed to look for knots further away than HH 80N, the northern head of the jet. Aligned with the jet and 10 arcmin northeast of HH 80N, we found a radio source not reported before, with a negative spectral index similar to that HH 80, HH 81 and HH 80N. The fit of a precessing jet model to the knots of the HH 80/81/80N jet, including the new source, shows that the position of this source is close to the jet path resulting from the modeling. If the new source belongs to the HH 80/81/80N jet, its derived size and dynamical age are 18.4 pc and >9000 yr, respectively. If the jet is symmetric, its southern lobe would expand beyond the cloud edge resulting in an asymmetric appearance of the jet. Based on the updated dynamical age, we speculate on the possibility that the HH 80/81/80N jet triggered the star formation observed in a dense core found ahead of HH 80N, which shows signposts of interaction with the jet. These results indicate that pc scale radio jets can play a role on the stability of dense clumps and the regulation of star formation in the molecular cloud.

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arXiv2009

The molecular emission of the irradiated star forming core ahead of HH 80N

We present a Berkeley-Illinois-Maryland Association (BIMA) Array molecular survey of the star forming core ahead of HH 80N, the optically obscured northern counterpart of the Herbig-Haro objects HH 80/81. Continuum emission at 1.4 mm and 8 micron is detected at the center of the core, which confirms the presence of an embedded very young stellar object in the core. All detected molecular species arise in a ring-like structure, which is most clearly traced by CS(2-1) emission. This molecular ring suggests that strong molecular depletion occurs in the inner part of the core (at a radius of ~0.1 pc and densities higher than ~5 x 10^4 cm^{-3}). Despite of the overall morphology and kinematic similarity between the different species, there is significant molecular differentiation along the ring-like structure. The analysis of the chemistry along the core shows that part of this differentiation may be caused by the UV irradiation of the nearby HH 80N object, that illuminates the part of the core facing HH 80N, which results in an abundance enhancement of some of the detected species.

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