The 6th Cambridge Survey of radio sources covers most of the sky north of Dec>30{deg} with an angular resolution of 4.2x4.2cosec{delta} arcmin^2^ and a limiting flux density of 120mJy at 151MHz. This paper, the first of a series, describes the telescope and the methods used to produce the survey maps and source list, and presents maps of a circular area of radius 10{deg} centered on the North Celestial Pole and a list of 1761 sources north of {delta}>+80{deg}.
The 6th Cambridge survey of radio sources covers most of the sky north of +30{deg} with an angular resolution of 4.2x4.2cosec{delta}arcmin^2^ and reaches a limiting flux density of 190mJy at 151MHz in the present zone. In this paper the methods used to produce the survey maps from a non-tracking telescope operating at declinations other than the north celestial pole are described: this forms the basis for all future papers in the series. Maps of a high galactic latitude region are presented 30{deg}<{delta}<51{deg}, 08h30m<{alpha}<17h30m, together with a list of 8278 sources in the 2030deg^2^ covered. A source count over the range 200mJy<S(151)<100Jy is derived.
The 6th Cambridge Survey of radio sources covers most of the sky north of 30{deg} with an angular resolution of 4.2x4.2cosec{delta} arcmin^2^ and a limiting flux density of 160mJy at 151MHz, with completeness achieved at 600mJy. This paper presents 8749 sources in the 1950deg^2^ region 48{deg}<{delta}<68{deg}, 05h25m<{alpha}<18h17m.
The 6th Cambridge Survey of radio sources covers most of the sky north of 30{deg} with an angular resolution of 4.2x4.2cosec{delta} arcmin^2^ and a limiting flux density of 160mJy at 151MHz, with completeness achieved at 600mJy. This zone covers the declinations 67{deg}--82{deg} region 48{deg}<{delta}<68{deg}, 05h25m<{alpha}<18h17m.
The 6th Cambridge Survey of radio sources covers most of the sky north of 30{deg} with an angular resolution of 4.2x4.2cosec{delta} arcmin^2^ and a limiting flux density of 160mJy at 151MHz, with completeness achieved at 600mJy. This paper presents, in the declination ranges 48{deg}<{delta}<68{dec} the zones Va (01h34<{alpha}<06h14) and Vb (17h16<{alpha}<20h24)
We present the results of a multi-site photometric campaign carried out in 2004-2008 for the Algol-type eclipsing binary system CT Her, the primary component of which shows delta Scuti-type oscillations. Our data consist of differential light curves collected in the filters B and V which have been analysed using the method of Wilson-Devinney (Phoebe). After identification of an adequate binary model and removal of the best-matching light curve solution, we performed a Fourier analysis of the residual B and V light curves to investigate the pulsational behaviour.
We investigate the massive star population of NGC 6822 with ground-based UBV photometry covering the whole of the galaxy and HST WFPC2 photometry with filters F255W, F336W, F439W, and F555W of two fields containing very rich and crowded OB associations. The four-band WFPC2 photometry is used to derive Teff and E(B-V). H-R diagrams are constructed for the OB associations included in our fields. These show that 10Myr old populations are present in OB 9 and OB 6, while more recent star formation have occurred in OB 8, OB 13, OB 15, and OB 7. Two particularly interesting H II regions, Hubble V and Hubble X, are included in our fields. The luminous massive stars that power these bright H II regions (H{alpha} luminosity several times that of the Orion nebula), could be resolved even in their dense cores thanks to the HST spatial resolution. Our data reveal very young (a few million years), apparently coeval populations, with several massive star candidates.
With the advent of the Legacy Survey of Space and Time, time-domain astronomy will be faced with an unprecedented volume and rate of data. Real-time processing of variables and transients detected by such large-scale surveys is critical to identifying the more unusual events and allocating scarce follow-up resources efficiently. We develop an algorithm to identify these novel events within a given population of variable sources. We determine the distributions of magnitude changes (dm) over time intervals (dt) for a given passband f, p_f_^(dm|dt)^, and use these distributions to compute the likelihood of a test source being consistent with the population or being an outlier. We demonstrate our algorithm by applying it to the DECam multiband time-series data of more than 2000 variable stars identified by Saha+ (2019, J/ApJ/874/30) in the Galactic Bulge that are largely dominated by long-period variables and pulsating stars. Our algorithm discovers 18 outlier sources in the sample, including a microlensing event, a dwarf nova, and two chromospherically active RS CVn stars, as well as sources in the blue horizontal branch region of the color-magnitude diagram without any known counterparts. We compare the performance of our algorithm for novelty detection with the multivariate Kernel Density Estimator and Isolation Forest on the simulated PLAsTiCC data set. We find that our algorithm yields comparable results despite its simplicity. Our method provides an efficient way for flagging the most unusual events in a real-time alert-broker system.
We characterize the absolute magnitudes and colors of RR Lyrae stars in the globular cluster M5 in the ugriz filter system of the Dark Energy Camera (DECam). We provide empirical period-luminosity (P-L) relationships in all five bands based on 47 RR Lyrae stars of the type ab and 14 stars of the type c. The P-L relationships were found to be better constrained for the fundamental-mode RR Lyrae stars in the riz passbands, with dispersions of 0.03, 0.02 and 0.02mag, respectively. The dispersion of the color at minimum light was found to be small, supporting the use of this parameter as a means to obtain accurate interstellar extinctions along the line of sight up to the distance of the RR Lyrae star. We found a trend of color at minimum light with a pulsational period that, if taken into account, brings the dispersion in color at minimum light to 0.016 mag for the (r-i), (i-z), and (r-z) colors. These calibrations will be very useful for using RR Lyrae stars from DECam observations as both standard candles for distance determinations and color standards for reddening measurements.