Hints of γ-ray orbital variability from γ2 Velorum

Martí-Devesa, G.; Reimer, O.; Li, Jian; Torres, D. F.

doi:10.1051/0004-6361/202037462

Cited by 19 publications

(17 citation statements)

References 43 publications

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“…However, high-energy emission from PACWBs lies mainly below the detection thresholds of the current instrumentation. The only exceptions are η Car (Tavani et al 2009;Abdo et al 2010;Reitberger et al 2015) and WR 11 (Pshirkov 2016;Martí-Devesa et al 2020). For this reason, radio observations constitute the most adequate approach to investigate these systems, especially from the point of view of their NT physics.…”

Section: Introductionmentioning

confidence: 99%

Megahertz emission of massive early-type stars in the Cygnus region

Benaglia

Becker

Ishwara‐Chandra

et al. 2020

Publ. Astron. Soc. Aust.

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Massive, early-type stars have been detected as radio sources for many decades. Their thermal winds radiate free–free continuum and in binary systems hosting a colliding-wind region, non-thermal emission has also been detected. To date, the most abundant data have been collected from frequencies higher than 1 GHz. We present here the results obtained from observations at 325 and 610 MHz, carried out with the Giant Metrewave Radio Telescope, of all known Wolf-Rayet and O-type stars encompassed in area of $\sim$ 15 sq degrees centred on the Cygnus region. We report on the detection of 11 massive stars, including both Wolf-Rayet and O-type systems. The measured flux densities at decimeter wavelengths allowed us to study the radio spectrum of the binary systems and to propose a consistent interpretation in terms of physical processes affecting the wide-band radio emission from these objects. WR 140 was detected at 610 MHz, but not at 325 MHz, very likely because of the strong impact of free–free absorption (FFA). We also report—for the first time—on the detection of a colliding-wind binary system down to 150 MHz, pertaining to the system of WR 146, making use of complementary information extracted from the Tata Institute of Fundamental Research GMRT Sky Survey. Its spectral energy distribution clearly shows the turnover at a frequency of about 600 MHz, that we interpret to be due to FFA. Finally, we report on the identification of two additional particle-accelerating colliding-wind binaries, namely Cyg OB2 12 and ALS 15108 AB.

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Section: Introductionmentioning

confidence: 99%

Megahertz emission of massive early-type stars in the Cygnus region

Benaglia

Becker

Ishwara‐Chandra

et al. 2020

Publ. Astron. Soc. Aust.

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“…Both confirmed cases behave differently, showing that the γ-ray emissivity is highly dependent on the particularities of each system. The case of γ 2 Velorum showed HE emission during apastron, with no detection of radio synchrotron (Benaglia et al 2019;Martí-Devesa et al 2020). This is unexpected because classical models estimate L γ ∼ 1/d, where d is the distance between both components of a binary.…”

Section: The Population Of Cwbs At High Energiesmentioning

confidence: 92%

“…Unfortunately, only one other CWB has been detected in γrays: γ 2 Velorum, also known as WR 11 (Pshirkov 2016;Martí-Devesa et al 2020). Despite numerous efforts, CWBs with significant synchrotron radio emission have been elusive to detection both with orbital and ground-based γ-ray observatories (Romero et al 1999;Aliu et al 2008;Werner et al 2013;del Palacio et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Eta Carinae with Fermi-LAT: Two full orbits and the third periastron

Martí-Devesa,

Reimer

2021

Preprint

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Context. Colliding-wind binaries are massive stellar systems featuring strong, interacting winds. These binaries may be actual particle accelerators, making them variable γ-ray sources due to changes in the wind collision region along the orbit. However, only two of these massive stellar binary systems have been identified as high-energy sources. The first and archetypical system of this class is η Carinae, a bright γ-ray source with orbital variability peaking around its periastron passage. Aims. The origin of the high energy emission in η Carinae is still unclear, with both lepto-hadronic and hadronic scenarios being under discussion. Moreover, the γ-ray emission seemed to differ between the two periastrons previously observed with the Fermi Large Area Telescope. Continuing observations might provide highly valuable information for the understanding of the emission mechanisms in this system. Methods. We have used almost 12 years of data from the Fermi Large Area Telescope. We studied both low and high energy components, searching for differences and similarities between both orbits, and made use of this large dataset to search for emission from nearby colliding-wind binaries. Results. We show how the energy component above 10 GeV of η Carinae peaks months before the 2014 periastron, while the 2020 periastron is the brightest to date. Additionally, upper limits are provided for the high-energy emission in other particle-accelerating colliding-wind systems. Conclusions. Current γ-ray observations of η Carinae strongly suggest that the wind collision region of this system is perturbed from orbit to orbit affecting particle transport within the shock.

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“…However, high-energy emission from PACWBs lies mainly below the detection thresholds of the current instrumentation. The only exceptions are η Car (Tavani et al, 2009;Abdo et al, 2010;Reitberger et al, 2015) and WR 11 (Pshirkov, 2016;Martí-Devesa et al, 2020). For this reason, radio observations constitute the most adequate approach to investigate these systems, especially from the point of view of their non-thermal physics.…”

Section: Introductionmentioning

confidence: 99%

Megahertz emission of massive early-type stars in the Cygnus region

Benaglia,

De Becker,

Ishwara-Chandra

et al. 2020

Preprint

View full text Add to dashboard Cite

Massive, early type stars have been detected as radio sources for many decades. Their thermal winds radiate free-free continuum and in binary systems hosting a colliding-wind region, non-thermal emission has also been detected. To date, the most abundant data have been collected from frequencies higher than 1 GHz. We present here the results obtained from observations at 325 and 610 MHz, carried out with the Giant Metrewave Radio Telescope, of all known Wolf-Rayet and O-type stars encompassed in area of ∼15 sq degrees centred on the Cygnus region. We report on the detection of 11 massive stars, including both Wolf-Rayet and O-type systems. The measured flux densities at decimeter wavelengths allowed us to study the radio spectrum of the binary systems and to propose a consistent interpretation in terms of physical processes affecting the wide-band radio emission from these objects. WR 140 was detected at 610 MHz, but not at 325 MHz, very likely because of the strong impact of free-free absorption. We also report -for the first time -on the detection of a colliding-wind binary system down to 150 MHz, pertaining to the system of WR 146, making use of complementary information extracted from the TIFR GMRT Sky Survey. Its spectral energy distribution clearly shows the turnover at a frequency of about 600 MHz, that we interpret to be due to free-free absorption. Finally, we report on the identification of two additional particle-accelerating colliding-wind binaries, namely Cyg OB2 12 and ALS 15108 AB.

show abstract

Hints of γ-ray orbital variability from γ² Velorum

Cited by 19 publications

References 43 publications

Megahertz emission of massive early-type stars in the Cygnus region

Megahertz emission of massive early-type stars in the Cygnus region

Eta Carinae with Fermi-LAT: Two full orbits and the third periastron

Megahertz emission of massive early-type stars in the Cygnus region

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