PKS 1538+149 also known as 4C 14.60, is a BL Lacertae object[1] located in the constellation of Serpens. The redshift of the object is found to be (z) 0.605[2] and was discovered through photoelectric observations in February 1975 by astronomers who observed it had a continuous spectra.[3] The radio spectrum of the source is flat, describing it a flat-spectrum radio source (FRSQ).[4]
Description
PKS 1538+149 is shown undergoing a decrease in brightness levels by displaying a low visual magnitude of 1.7 as observed by E.R. Craine and K. Johnson.[3] It is noted to be variable too, when it was detected by J.T. Pollock in 1975, who noted the object had an amplitude exceeding more than a magnitude of 2.8 ± 0.20, however it has no evidence of variations in X-ray flux.[5][6] During the period between April and June 1986, the light curve data, showed it undergoing a decrease of 0.0026 magnitude per day, averaging on the magnitude of 18.54.[7] The object is also classified as a blazar due to its high optical polarization, displaying large variations more than 1 magnitude while the spectral index described as both steep and also variable, remained constant.[8][9][10]
The radio structure of PKS 1538+149 is described as compact. On arcsecond scales, the source has a size of 6 centimeters with radio emission depicted as being concentrated in its northern region.[11] Observations also showed the source is elongated with radio frequency identification imaging finding the emission further extends northwest by 60 milliarcseconds and by 10 milliarcseconds at 8.4 GHz frequencies.[12] It is found PKS 1538+149 has a jet with jet power of 2.36 x 1045ergs with an opening angle of 16.1°. The radio core is noted shifting by 0.032 milliarcseconds in frequencies of 8.1-15.3 GHz.[13]
Earlier observations, especially using near-infrared H-band found PKS 1538+149 has an unresolved host galaxy.[14] Imaging with Hubble Space Telescope would later reveal the host galaxy is indeed a round elliptical galaxy, surrounded by several other faint galaxies within its vicinity. It has a low surface brightness and V-I color of 2.85. A de Vaucouleurs model also described the host galaxy as large and luminous with a measured magnitude of -25.1 and length of 21 kilometers in size.[15] A central supermassive black hole mass of 7.54 x 104Mʘ was found for the object.[4]
^Zensus, J. A.; Ros, E.; Kellermann, K. I.; Cohen, M. H.; Vermeulen, R. C.; Kadler, M. (August 2002). "Sub-milliarcsecond Imaging of Quasars and Active Galactic Nuclei. II. Additional Sources". The Astronomical Journal. 124 (2): 662–674. arXiv:astro-ph/0205076. Bibcode:2002AJ....124..662Z. doi:10.1086/341585. ISSN0004-6256.
