M. A. Trinidad

Large Proper Motions in the Jet of the High-Mass YSO Cepheus A HW2

Using high angular resolution (~025-005) Very Large Array (VLA) observations made at 3.6 cm, 1.3 cm, and 7 mm during the period 1991-2004, we report the detection of large proper motions in the components of the radio continuum jet associated with the high-mass young stellar object (YSO) HW2 in the star-forming region Cepheus A. The relative proper motions observed for the two main components of the outflow, moving away from the central source in nearly opposite directions, are of the order of 140 mas yr-1, or ~480 km s-1 at a distance of 725 pc. The proper motions observed in the northeast and southwest lobes are not completely antiparallel, and the central elongated source seems to be changing orientation. We discuss possible scenarios to account for these and other observed characteristics. We also report the detection of a 7 mm compact continuum condensation of emission near the center of the thermal radio continuum jet, which we propose as the location of the exciting star.

Observations of Water Masers and Radio Continuum Emission in AFGL 2591

We report results of continuum (1.3 and 3.6 cm) and H2O maser line high angular resolution observations, made with the Very Large Array (VLA) in the A configuration, toward the star-forming region AFGL 2591. Three radio continuum sources (VLA 1, VLA 2, and VLA 3) were detected in the region at 3.6 cm, and one source (VLA 3) at 1.3 cm. VLA 1 and VLA 2 appear resolved and their spectral indices suggest free-free emission from optically thin H II regions. VLA 3 is elongated in the east-west direction, along the axis of the bipolar molecular outflow observed in the region. Its spectral energy distribution is consistent with it being a ~200 AU optically thick disk plus a photoionized wind. In addition, we detected 85 water maser spots toward the AFGL 2591 region, which are distributed in three main clusters. Two of these clusters are spatially associated with VLA 2 and VLA 3, respectively. The third cluster of masers, including the strongest water maser of the region, does not coincide with any known continuum source. We suggest that this third cluster of masers is excited by an undetected protostar that we predict to be located 05 (500 AU) north from VLA 3. The maser spots associated with VLA 3 are distributed along a shell-like structure of 001 size, showing a peculiar velocity-position helical distribution. We propose that VLA 3 is the powering source of the observed molecular outflow in this region. Finally, we support the notion that the AFGL 2591 region is a cluster of B0-B3 type stars.

Detection of a Candidate for the Exciting Source of the Expanding Water Maser Bubble in Cepheus A

We report sensitive, high angular resolution VLA 3.6 cm and 7 mm continuum observations toward the star-forming region Cepheus A. Three embedded young stellar objects (YSOs) were found within a projected area of 06 × 06 (400 × 400 AU2). One of the sources is the already known radio continuum jet HW2 (detected at 3.6 cm and 7 mm), while the other two weak sources were not previously known. One of these two new sources is detected only at 7 mm and is located 015 south from HW2. The other source, detected only at 3.6 cm, is located 06 south from HW2 and nearly coincides with the center of the enigmatic expanding bubble of water masers recently detected with the Very Long Baseline Array. We suggest that this radio continuum source is the embedded YSO powering the water maser structure, but its nature is still unknown at present. We also discuss possible scenarios that could explain the surprisingly precise spherical geometry of the water maser bubble.

Very Large Array Simultaneous 1.3?cm Continuum and H2O Maser Observations toward IRAS?20126+4104

We have observed simultaneously the 1.3 cm continuum and H2O maser emission toward the high-mass protostar IRAS 20126+4104 with the Very Large Array (VLA) in its A configuration, providing an angular resolution of 01. We have detected an unresolved continuum source [I20126N(1.3 cm)] nearly coinciding with the strongest peak of the northern double continuum source previously detected at 3.6 cm in the field and suggested to be a radio jet. In addition, we have detected 29 water maser spots, 21 of which are tightly grouped in a cluster of 01 size displaced 007 (120 AU) northwest of I20126N(1.3 cm). The relative positions of the masers with respect to I20126N(1.3 cm) have been established with 10 mas of accuracy. The overall spatial distribution and line-of-sight velocity components of the water maser spots associated with I20126N(1.3 cm) are fully consistent with those previously found by Moscadelli and collaborators through VLBI measurements and interpreted as tracing a conical outflow, with the powering source (suggested to be traced by a one-sided radio continuum jet) located at the cone vertex. Within this very reasonable scenario, our observations would indicate that the source I20126N(1.3 cm) is showing the position of the high-mass protostar. Analyzing the spatiokinematic distribution of the VLA water masers, we propose that their motions also show, in addition to proper motions on the order of 100 km s-1 seen in the plane of the sky, a component of rotation with velocities on the order of 20 km s-1. The water masers seem then to be both rotating (as evidenced from their radial velocities) and changing their position in the plane of the sky (from the proper motions). Within this scenario, some of the water maser spots could be within a rotating circumstellar disk of 170 AU size around a protostar of 20 M⊙ if it is located at the center of the water maser cluster rather than located at the position of I20126N(1.3 cm). Then, I20126N(1.3 cm) would trace one of the two peaks of a two-sided thermal jet, with the high-mass protostar located in between. We think that simultaneous high angular resolution and sensitive multifrequency (from centimeter to submillimeter wavelengths) observations are the key studies to knowing both the nature of the continuum emission (one- or two-sided jet?) and the location of the high-mass protostar, which is very relevant for modeling this important object.

Time series of high-resolution spectra of SN 2014J observed with the TIGRE telescope

We present a time series of high resolution spectra of the Type Ia supernova 2014J, which exploded in the nearby galaxy M82. The spectra were obtained with the HEROS echelle spectrograph installed at the 1.2 m TIGRE telescope. We present a series of 33 spectra with a resolution of R = 20, 000, which covers the important bright phases in the evolution of SN 2014J during the period from January 24 to April 1 of 2014. The spectral evolution of SN 2014J is derived empirically. The expansion velocities of the Si II P-Cygni features were measured and show the expected decreasing behaviour, beginning with a high velocity of 14,000 km/s on January 24. The Ca II infrared triplet feature shows a high velocity component with expansion velocities of > 20, 000 km/s during the early evolution apart from the normal component showing similar velocities as Si II. Further broad P-Cygni profiles are exhibited by the principal lines of Ca II, Mg II and Fe II. The TIGRE SN 2014J spectra also resolve several very sharp Na I D doublet absorption components. Our analysis suggests interesting substructures in the interstellar medium of the host galaxy M82, as well as in our Milky Way, confirming other work on this SN. We were able to identify the interstellar absorption of M82 in the lines of Ca II H & K at 3933 and 3968 A as well as K I at 7664 and 7698 A. Furthermore, we confirm several Diffuse Interstellar Bands, at wavelengths of 6196, 6283, 6376, 6379 and 6613 A and give their measured equivalent widths.

RADIO JETS AND DISKS IN THE INTERMEDIATE-MASS STAR-FORMING REGION NGC2071IR

We report the results of simultaneous radio continuum and water maser observations toward the NGC 2071IR star-forming region, carried out with the VLA in its A configuration. We detect continuum emission toward the infrared sources IRS 1 and IRS 3 at 1.3 and 3.6 cm. In addition, a new continuum source, VLA 1, is also detected at both wavelengths, which is located between IRS 1 and IRS 3. IRS 1 breaks up into three continuum peaks (IRS 1E, 1C, and 1W), aligned in the east-west direction (P.A. = 100°). IRS 1 is the central source, while the sources E and W seem to be condensations ejected by IRS 1. In the same way, IRS 3 is also forming a triple system (IRS 3N, 3C and 3S), which is elongated in the northeast-southwest direction and the condensations, IRS 3N and IRS 3S, are symmetrically located along the major axis. Based on the morphology and the continuum emission, we suggest that both IRS 1 and IRS 3 are radio jets, which have ejected condensations into the interstellar medium. Moreover, IRS 1 and IRS 3 seem to be the driving sources of the large-scale outflows observed in H2 and CO, respectively. In addition, we also detected water emission toward the systems IRS 1, IRS 3, and the new source VLA 1. Based on the spatial-kinematic distribution of the water masers, we find evidence that the water masers are tracing part of circumstellar disks around IRS 1C and IRS 3C. Moreover, we estimate that the sources IRS 1C and IRS 3C have central masses of ~5 and ~1 M ☉, respectively. We conclude that the radio continuum and water maser emission are tracing disk-YSO-outflow systems toward IRS 1 and IRS 3, which are low- and intermediate-mass young stellar objects, respectively.

A very young, compact bipolar H2O maser outflow in the intermediate-mass star-forming LkHα 234 region

We report multi-epoch VLBI H

High-Resolution H2O Maser Observations toward IRAS Sources in Bright-Rimmed Clouds

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SEARCHING FOR THE DRIVING SOURCE OF THE CO MOLECULAR OUTFLOW IN THE HIGH-MASS STAR-FORMING REGION G240.31+0.07

O maser observations towards the compact cluster of YSOs close to the Herbig Be star LkH

INTERFEROMETRIC OBSERVATIONS TOWARD THE HIGH-MASS YOUNG STELLAR OBJECT IRAS 23139+5939: RADIO CONTINUUM AND WATER MASER EMISSION

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