A. Petriella

Study of the luminous blue variable star candidate G26.47+0.02 and its environment

Aims. The luminous blue variable (LBV) stars are peculiar very massive stars. The study of these stellar objects and their surroundings is important for understanding the evolution of massive stars and its effects on the interstellar medium. We study the LBV star candidate G26.47+0.02. Methods. Using several large-scale surveys in different frequencies we performed a multiwavelength study of G26.47+0.02 and its surroundings. Results. We found a molecular shell (seen in the 13CO J = 1–0 line) that partially surrounds the mid-infrared nebula of G26.47+0.02, which suggests an interaction between the strong stellar winds and the molecular gas. From the HI absorption and the molecular gas study we conclude that G26.47+0.02 is located at a distance of ∼4.8 kpc. The radio continuum analysis shows both thermal and non-thermal emission toward this LBV candidate, pointing to wind-wind collision shocks from a binary system. This hypothesis is supported by a search of near-IR sources and the Chandra X-ray analysis. Additional multiwavelength and long-term observations are needed to detect some possible variable behavior, and if that is found, to confirm the binary nature of the system.

The molecular gas around the luminous blue variable star G24.73+0.69

Aims. We study the molecular environment of the luminous blue variable star G24.73+0.69 to investigate the origin of the two infrared shells around this massive star and determine its effects on the surrounding interstellar medium. Methods. We analyze the distribution of the molecular gas using the 13 CO J = 1–0 emission extracted from the Galactic Ring Survey. We use near- and mid-infrared data from 2MASS and GLIMPSE to identify the young stellar objects in the field. Results. We discover the molecular counterpart to the outer infrared shell around G24.73+0.69. The CO shell was probably blown by the stellar wind of the star mainly during its main sequence phase. We also find molecular gas that corresponds to the inner infrared shell, although its origin remains uncertain. We identify seven young stellar objects within the molecular material, whose birth might have been triggered by the stellar wind of the luminous blue variable star. We suggest that both G24.73+0.69 and the progenitor of the nearby supernova remnant G24.7+0.6 were formed from the same natal cloud and represent the most evolved members of a so far undetected cluster of massive stars.

An X-ray study of the supernova remnant G20.0-0.2 and its surroundings

Fil: Petriella, Alberto. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Astronomia y Fisica del Espacio(i); Argentina; Universidad de Buenos Aires; Argentina;

The southern molecular environment of SNR G18.8+0.3

Aims. In a previous paper we have investigated the molecular environment towards the eastern border of the SNR G18.8+0.3. Continuing with the study of the surroundings of this SNR, in this work we focus on its southern border, which in the radio continuum emission shows a very peculiar morphology with a corrugated corner and a very flattened southern flank. Methods. We observed two regions towards the south of SNR G18.8+0.3 using the Atacama Submillimeter Telescope Experiment (ASTE) in the 12 CO J=3‐2. One of these regions was also surveyed in 13 CO and C 18 O J=3‐2. The angular and spectral resolution of these observations were 22 ′′ , and 0.11 km s −1 . We compared the CO emission to 20 cm radio continuum maps obtain as part of the Multi-Array Galactic Plane Imaging Survey (MAGPIS) and 870µm dust emission extracted from the APEX Telescope Large Area Survey of the Galaxy. Results. We discovered a molecular feature with a good morphological correspondence with the SNR’s southernmost corner. In particular, there are indentations in the radio continuum map that are complemented by protrusions in the molecular CO image, strongly suggesting that the SNR shock is interacting with a molecular cloud. Towards this region we found that the 12 CO peak is not correlated with the observed 13 CO peaks, which are likely related to a nearby Hii region. Regarding the most flattened border of SNR G18.8+0.3, where an interaction of the SNR with dense material was previously suggested, our 12 CO J=3‐2 map show no obvious

Discovering a misaligned CO outflow related to the red MSX source G034.5964-01.0292

Aims. The red MSX source G034.5964-01.0292 (MSXG34), catalogued as a massive young stellar object, was observed in molecular lines with the aim of discovering and studying molecular outflows. Methods. We mapped a region of 3 � × 3 � centred at MSXG34 using the Atacama Submillimeter Telescope Experiment in the 12 CO J = 3–2 and HCO + J = 4–3 lines with an angular and spectral resolution of 22 �� and 0.11 km s −1 . Additionally, public 13 CO J = 1–0 and near-IR UKIDSS data obtained from the Galactic Ring Survey and the WFCAM Sciencie Archive were analysed. Results. We found that the 12 CO spectra towards the YSO present a self-absorption dip, as is common in star-forming regions, and spectral wings that indicate outflow activity. The HCO + was detected only towards the MSXG34 position at vLSR ∼ 14. 2k m s −1 ,i n coincidence with the 12 CO absorption dip and approximately with the velocity of previous ammonia observations. HCO + and NH3 are known to be enhanced in molecular outflows. When we analysed the spectral wings of the 12 CO line, we discovered misaligned red- and blue-shifted molecular outflows associated with MSXG34. The near-IR emission shows a cone-like nebulosity composed of two arc-like features related to the YSO, which might be due to a cavity cleared in the circumstellar material by a precessing jet. This can explain the misalignment in the molecular outflows. From the analysis of the 13 CO J = 1–0 data we suggest that the YSO is very likely related to a molecular clump ranging between 10 and 14 km s −1 . This suggests that MSXG34, with an associated central velocity of about 14 km s −1 , may be located in the background of this clump. Thus, the blue-shifted outflow is probably deflected by the interaction with dense gas along the line of sight. From a spectral energy distribution analysis of MSXG34 we found that its central object probably is an intermediate-mass protostar.

The molecular environment of the pillar-like features in the H ii region G46.5–0.2

CONICET ANPCYT UBA (UBACyT) from Argentina Varsavsky Foundation FONDECYT(CHILE) 1140839

Radio and X-ray properties of the source G29.37+0.1 linked to HESS J1844−030

Fil: Castelletti, Gabriela Marta. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Astronomia y Fisica del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomia y Fisica del Espacio; Argentina