Comparison stars

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Colour chart A

Credit: SDSS  /  Size 13´× 13´ /  Chart by S. Karge

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Colour chart B

This 3´× 3´section from SDSS shows the quasar host of MRK 478 as a slightly
oval galaxy disk (apparent diameter 30"×20") with a bright stellar core.

Credit: SDSS  /  Size 3´× 3´

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Notes

Markarian 478 (MRK 478 for short) is a bright quasar in Bootes, about 3.5° SE of Gamma Bootis. MRK 478 was discovered in 1972 by the UV-Continuum-Survey run by Markarian et al. (MRK) at the Astrophysical Observatory in Byurakan/Armenia. Main goal was the spectroscopic search for "blue" galaxies with excessive UV-emission. MRK 478 was detected as a very compact, star-like object. As a blue star-like object it was also detected by both the Palomar-Green Bright Quasar Survey (PG) and the Extreme Ultraviolet Explorer (EUVE). The quasar host is a spiral galaxy with an apparent diameter of 30"×20". The host itself shows clear signs of disturbance, detectible as faint shells or arms. The very bright nucleus emits a Narrow-Line Seyfert 1-spectrum (NLS1), very similar to that found with I Zw 1. MRK 478 is a low amplitude variable object with a total range of less than 1 magnitude. Visual observers need at least an 8- to 10-inch telescope to glimpse this stellar object. Using large aperture telescopes, the quasar becomes either star-like or a star-like object, enveloped by a very diffuse and small halo. With very large aperture and high power, observers may recognize a slightly bluish hue of the bright star-like nucleus, a result of the UV-excess of this active galactic nucleus. CCD observers, as well as visual observers, shall use the comparison stars given above. ____________ Finding MRK 478 is an easy task due to its position 3.5° SE of Gamma Bootis. A little south of Gamma Bootis, a chain of stars of mag 6 and mag 7 directly point to the quasar. Only 1.5° NE, we find the faint galaxy NGC 5695, also known as MRK 686, an active galaxy with S2-spectrum. As with MRK 478, this AGN was also found by the UV-Continuum-Survey mentioned above. Observers who like to track down some more very old quasi-stellar photons may turn to quasar PG 1411+442, a bright 14-mag object at a distance of about 1×109 light-years, some 10° NW of MRK 478. Another bright quasi-stellar object is PKS 1424+240, a variable 14-mag BL Lac object, located about 12° SSW of MRK 478.

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Literature

de Grijp, M.H.K., Miley, G.K., et al. 1987, A&AS, 70, 95; Warm IRAS Sources. I. A Catalogue of AGN Candidates from      the Point Source Catalogue (PSC). Gondhalekar, P.M., Kellett, B.J., et al. 1994, MNRAS, 268, 973; ROSAT/XRT-PSPC Observations and the Ionizing      Continuum of the Seyfert 1 Galaxy Mrk 478. Hansen, T. 1991, Deep Sky Magazine 34, 32; The "Deepest" Deep Sky Objects. Karge, S.; Helle Quasare für 8- bis 10-Zoll Teleskope. Ein Beobachtungsführer zur visuellen Beobachtung von Quasaren      und BL Lacertae Objekten; Frankfurt 2005. Khachikian, E.E., Weedman, D.W. 1974, ApJ, 192, 581; An Atlas of Seyfert Galaxies. Markarian, B.E., Lipovetzki, V.A. 1972, Astrophysics, 8, 89; Galaxies with Ultraviolet Continuum V. Peterson, B.M., Fricke, K., et al. 1981, PASP, 93, 281; UBV Photometry of Markarian and S0 galaxies. Schmidt, M., Green, R.F. 1983, ApJ, 269, 352; Quasar Evolution derived from the Palomar Bright Quasar Survey and      other complete Quasar Surveys. Steinicke, W.; Katalog heller Quasare und BL Lacertae Objekte; Umkirch 1998. Steinicke, W.; Beobachtungsliste für helle Quasare; Umkirch 1999. Véron-Cetty, M.-P., Véron, P. 2001, A&A 374, 92; A Catalogue of Quasars and Active Nuclei: 10th edition. Véron-Cetty, M.-P., Véron, P. 2003, A&A 412, 399; A Catalogue of Quasars and Active Nuclei: 11th edition. Véron-Cetty, M.-P., Véron, P. 2006, A&A 455, 776; A Catalogue of Quasars and Active Nuclei: 12th edition. Véron-Cetty, M.-P., Véron, P. 2010, A&A 518, 10; A Catalogue of Quasars and Active Nuclei: 13th edition. Webb, W., Malkan, M. 2000, ApJS, 130, 165; Comparison star sequences for optical photometry of Active Galactic      Nuclei and Quasars.

 

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Links: APASS Chara/PEGA Sloan Digital Sky Survey

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© Stefan Karge (FQM)  /  last obs. 2024-08-21

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