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Description
This table contains some of the results from the first dedicated radio continuum survey of a Kepler K2 mission field, Field 1, covering the North Galactic Cap. The survey was wide-field, contemporaneous, multi-epoch, and multi-resolution in nature and was conducted at low radio frequencies between 140 and 200 MHz. The multi-epoch and ultra-wide-field (but relatively low-resolution) part of the survey was provided by 15 nights of observation using the Murchison Widefield Array (MWA) over a period of approximately a month, contemporaneous with K2 observations of this field. The multi-resolution aspect of the survey was provided by the low-resolution (4 arcminutes) MWA imaging, complemented by non-contemporaneous but much higher resolution (20 arcseconds) observations using the Giant Metrewave Radio Telescope (GMRT). The survey is, therefore, sensitive to the details of radio structures across a wide range of angular scales. Consistent with other recent low radio frequency surveys, no significant radio transients or variables were detected in the survey. The resulting source catalogs consist of 1,085 and 1,468 detections in the two MWA observation bands (centered at 154 and 185 MHz, respectively) and 7445 detections in the GMRT observation band (centered at 148 MHz), over 314 square degrees. The survey is presented as a significant resource for multi-wavelength investigations of the more than 21,000 target objects in the K2 field. In the reference paper, the authors briefly examined their survey data against K2 target lists for dwarf star types (stellar types M and L) that had been known to produce radio flares. This survey included contemporaneous observations of the K2 Field 1 made with the MWA and historical (from 2010-2012) observations made with the Tata Institute of Fundamental Research (TIFR) GMRT Sky Survey (TGSS; see <a href="http://tgss.ncra.tifr.res.in/">http://tgss.ncra.tifr.res.in/</a>), via the TGSS Alternative Data Release 1 (ADR1; Intema et al. 2016, in prep.). The MWA and GMRT are radio telescopes operating at low radio frequencies (approximately 140-200 MHz for the work described here). The K2 mission Campaign 1 was conducted on Field 1 (center at J2000.0 coordinates RA of 11:35:45.51 and Dec of +01:25:02.28;), covering the North Galactic Cap, between 2014 May 30 and August 21. The details of the MWA observations are described in Table 1 of the reference paper (available at <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/152/82/table1.dat">https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/152/82/table1.dat</a>), showing the 15 observations conducted over a period of approximately one month in 2014 June and July. All observations were made in a standard MWA imaging mode with a 30.72-MHz bandwidth consisting of 24 contiguous 1.28-MHz "coarse channels", each divided into 32 "fine channels" each of 40-kHz bandwidth (a total of 768 fine channels across 30.72 MHz). The temporal resolution of the MWA correlator output was set to 0.5s. All observations were made in full polarimetric mode, with all Stokes parameters formed from the orthogonal linearly polarized feeds. Observations were made at two center frequencies, 154.88 and 185.60 MHz, with two 296-s observations of the K2 field at each frequency on each night of observation, accompanied by observations of one of three calibrators (Centaurus A, Virgo A, or Hydra A) at each frequency, with 112-s observations. The observed fields were tracked, and thus, due to the fixed delay settings available to point the MWA primary beam, the tracked RA and Dec changes slightly between different observations (always a very small change compared to the MWA field of view). The total volume of MWA visibility data processed was approximately 2.2 TB. The synthesized beam at 154 MHz is approximately 4.6 x 4.2 arcminutes at a position angle of 105 degrees, and approximately 4 x 3 arcminutes at a position angle of 109 degrees at 185 MHz. The 154 MHz images have a typical noise of 100 mJy/beam, while the 184 MHz images have a typical noise of 70 mJy/beam. A source catalog was produced from each of the two frequencies of MWA data and given in Table 2 of the reference paper. The final set of MWA images after source finding yielded a total of 1,085 radio sources at 154 MHz, and 1,471 sources at 185 MHz over 314 square degrees, at an angular resolutions of ~4 arcminutes: this MWA catalog is contained in this HEASARC table, which thus has 1,085 + 1,471 = 2,556 entries. The GMRT images, after source finding, yielded a total of 7,445 radio sources over the same field, at an angular resolution of ~0.3 arcminutes: the GMRT catalog is contained in a separate HEASARC table GMRTK2F1LF which is available at <a href="http://heasarc.gsfc.nasa.gov/W3Browse/radio-catalog/gmrtk2f1lf.html">http://heasarc.gsfc.nasa.gov/W3Browse/radio-catalog/gmrtk2f1lf.html</a>. Thus, the overall survey covers multiple epochs of observation, spans approximately 140-200 MHz, is sensitive to structures on angular scales from arcseconds to degrees, and is contemporaneous with the K2 observations of the field over a period of approximately one month. This table was created by the HEASARC in December 2016 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/152/82">CDS Catalog J/AJ/152/82</a> file table2.dat (the MWA Kepler 2 Field 1 source catalog). This is a service provided by NASA HEASARC .
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