Low-frequency GMRT observations of ultra-cool dwarfs

Zic, Andrew; Lynch, C.; Murphy, Tara; Kaplan, David L.; Chandra, Poonam

doi:10.1093/mnras/sty3163

Cited by 11 publications

(9 citation statements)

References 73 publications

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“…The dashed and dotted lines mark the detection thresholds of our most and least sensitive observations, those at GJ 176 and HD 178911B, respectively, relative to these flare energies. Williams et al 2014Williams et al , 2017Zic et al 2019;Richey-Yowell et al 2020). The two AO discoveries of the coolest known radio-flaring brown dwarfs near the brown dwarf/ exoplanet boundary are marked by filled stars (Route & Wolszczan 2012, 2016a.…”

Section: Discussionmentioning

confidence: 99%

“…Figure2. Logarithmic plots of νL ν radio luminosity upper limits versus spectral type (left panel) or exoplanet mass (right panel) of surveyed brown dwarf and low-mass stellar companions, as compared to previously detected radio-emitting UCDs(Burgasser et al 2015;Route & Wolszczan 2016b;Route 2017a;Williams et al 2014Williams et al , 2017Zic et al 2019;Richey-Yowell et al 2020). The two AO discoveries of the coolest known radio-flaring brown dwarfs near the brown dwarf/ exoplanet boundary are marked by filled stars(Route & Wolszczan 2012, 2016a.…”

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confidence: 99%

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ROME III. The Arecibo Search for Auroral Emissions and Star-Planet Interactions at 5 GHz

Route¹,

Wolszczan²

2022

Preprint

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Despite many attempts to detect radio emissions from magnetized exoplanets, a reproducible, unambiguous detection remains elusive. On the other hand, the search for periodic radio emissions from exoplanet host stars that may be induced by star-planet interactions in, for example, hot Jupiter systems, has only recently begun. In this third paper of the ROME (Radio Observations of Magnetized Exoplanets) series, we present the results of a targeted radio survey of 17 nearby systems that host exoplanet, brown dwarf, and low-mass stellar companions conducted with the Arecibo radio telescope at ∼5 GHz. This GHz-frequency survey has the greatest frequency coverage of any to date, while providing mJy-level sensitivity over <1 s integration times. Neither auroral radio emissions from the substellar targets, nor exoplanet-induced stellar radio bursts were detected. These results are considered within the context of observed brown dwarf radio emissions, which support magnetospheric phenomenon similar to that found at Jupiter. We also describe the orbital phase coverage of our data for systems that may feature star-planet interactions, and briefly examine our results within the context of other searches for star-planet interactions within the same systems. Finally, as several of our targets are within their respective systems' habitable zones, we consider the implications of our survey on the search for technosignatures within those systems.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

ROME III. The Arecibo Search for Auroral Emissions and Star-Planet Interactions at 5 GHz

Route¹,

Wolszczan²

2022

Preprint

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“…As FAST is sensitive to rapidly varying radio emission, here we have only estimated the detection rate of flaring UCDs from those unbiased, targeted surveys since 2002 (Berger 2002(Berger , 2006Burgasser & Putman 2005;Phan-Bao et al 2007;Antonova et al 2008Antonova et al , 2013McLean et al 2012;Route & Wolszczan 2013, 2016bWilliams et al 2014;Lynch et al 2016;Zic et al 2019). Here the term 'unbiased' means that the targets are selected without preferences, e.g.…”

Section: Detection Rate Of Radio-flaring Ucds From Unbiased Surveysmentioning

confidence: 99%

The Potential of Detecting Radio-flaring Ultracool Dwarfs at L band in the FAST Drift-scan Survey

Tang,

Tsai,

2022

Preprint

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The Five-hundred-meter Aperture Spherical radio Telescope (FAST) completed its commissioning and began the Commensal Radio Astronomy FasT Survey (CRAFTS), a multi-year survey to cover 60% of the sky, in 2020. We present predictions for the number of radio-flaring ultracool dwarfs (UCDs) that are likely to be detected by CRAFTS. Based on the observed flaring UCDs from a number of unbiased, targeted radio surveys in the literature, we derive a detection rate of ≥3%. Assuming a flat radio spectrum νL ν ∝ ν β+1 with β = -1.0 for UCD flares, we construct a flare luminosity function dN/dL ∝ L −1.96±0.45 (here L = νL ν ). CRAFTS is found to be sensitive enough for flares from UCDs up to ∼180 pc. Considering the Galactic thin disk, we carry out a 3D Monte Carlo simulation of the UCD population, which is then fed to mock CRAFTS observations. We estimate that ∼170 flaring UCDs would be detected through transient searches in circular polarization. Though only marginally sensitive to the scale height of UCDs, the results are very sensitive to the assumed spectral index β. For β from 0 to -2.5, the number of expected detections increases dramatically from ∼20 to ∼3460. We also contemplate the strategies for following up candidates of flaring UCDs, and discuss the implications of survey results for improving our knowledge of UCD behavior at L band and dynamos.

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“…(1) in Williams 2018). A VLA detection at 4-8 GHz implies a magnetic field of at least B ≥ 2 kG (Kao et al 2016), and only LOFAR and GMRT, which work at MHz frequencies, have the potential to probe weaker magnetic fields, but such observations of ultracool BDs have proven to be challenging (Burningham et al 2016;Zic et al 2019). An ALMA detection at 85-101 GHz would place a lower limit at B ≥ 34 kG, an essentially unphysical value for lowmass stars (Reiners & Basri 2007).…”

Section: The Magnetic Field Of W0855mentioning

confidence: 99%

A search for millimeter emission from the coldest and closest brown dwarf with ALMA

Petry

Ivanov

2020

A&A

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Context. WISE J085510.83−071442.5 (W0855) is a unique object: with Teff ≈ 250 K it is the coldest known brown dwarf (BD), located at only ≈2.2 pc form the Sun. It is extremely faint, which makes any astronomical observations difficult. However, at least one remotely similar ultra-low-mass object, the M9 dwarf TVLM 513-46546, has been shown to be a steady radio emitter at frequencies up to 95 GHz with superimposed active states where strong, pulsed emission is observed. Aims. Our goal is to determine the millimeter radio properties of W0855 with deep observations around 93 GHz (3.2 mm) in order to investigate whether radio astrometry of this object is feasible and to measure or set an upper limit on its magnetic field. Methods. We observed W0855 for 94 min at 85.1–100.9 GHz on 24 December 2019 using 44 of the Atacama Large millimeter Array (ALMA) 12 m antennas. We used the standard ALMA calibration procedure and created the final image for our analysis by accommodating the Quasar 3C 209, the brightest nearby object by far. Furthermore, we created a light curve with a 30 s time resolution to search for pulsed emission. Results. Our observations achieve a noise RMS of 7.3 μJy beam−1 for steady emission and of 88 μJy for 30 s pulses in the aggregated bandwidth (Stokes I). There is no evidence for steady or pulsed emission from the object at the time of the observation. We derive 3σ upper limits of 21.9 μJy on the steady emission and of 264 μJy on the pulsed emission of W0855 between 85 GHz and 101 GHz. Conclusions. Together with the recent non-detection of W0855 at 4–8 GHz, our constraints on the steady and pulsed emission from W0855 confirm that the object is neither radio-loud nor magnetospherically particularly active.

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Low-frequency GMRT observations of ultra-cool dwarfs

Cited by 11 publications

References 73 publications

ROME III. The Arecibo Search for Auroral Emissions and Star-Planet Interactions at 5 GHz

ROME III. The Arecibo Search for Auroral Emissions and Star-Planet Interactions at 5 GHz

The Potential of Detecting Radio-flaring Ultracool Dwarfs at L band in the FAST Drift-scan Survey

A search for millimeter emission from the coldest and closest brown dwarf with ALMA

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