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PKS 0405–385
PKS 0405–385
	The blazar PKS 0405-385.
Observation data (Epoch J2000.0)
Constellation	Eridanus
Right ascension	04h 06m 59.035s
Declination	−38° 26′ 28.04″
Redshift	1.285
Type	FSRQ
Other designations
	4FGL J0407.0-3826
	See also: Quasar, List of quasars

PKS 0405–385 is a blazar^[5] in the constellation of Eridanus. This is a compact radio quasar with a redshift (z) of 1.285, an indicator of its significant distance.^[6] The radio spectrum of this source appears flat, making it a flat-spectrum radio quasar (FSRQ).^[3]

Description

The visible light spectrum of PKS 0405–385 displays strong, broad emission lines, with an intermediate absorption occurring at a redshift of 0.875.^[6] Examination using VLBI shows the radio source spans less than five microarcseconds (μas) in angle.^[7] In 1993, this quasar was found to undergo variation in radio flux density during time spans of less than an hour. This variability is intermittent during episodes lasting for weeks or months.^[6]^[8] The radio flux was also found to vary on longer timescales for periods of a month or two.^[9]

If the short-term variation were due to the quasar, it would imply an extreme brightness temperature of about 10²¹ K.^[6] Instead, it was proposed that the variation was the result of interstellar scintillation due to ionized clouds in the Milky Way.^[9]^[10] The radio emission from the quasar underwent rotation of linear polarization during these events, lending support to the idea of scintillation.^[11] A scattering medium at a distance of 3–30 pc would explain these observations, bringing the modelled peak brightness temperature down to a more plausible 2.0×10¹³ K.^[12]^[9] The episodic nature of the rapid variations may be explained by changes in the quasar or the interstellar medium.^[7] PKS 0405–385 is one of only three known extreme scintillators, the others being PKS 1257−326 and J1819+385.^[7]

In 2022, the gamma ray emission from PKS 0405–385 was found to undergo quasi-periodic oscillation with a period of about 2.8 years. This may be explained by helical motion in a jet originating from the supermassive black hole (SMBH), or the core SMBH is itself a binary system.^[13]^[5] Enhanced gamma ray activity was observed from this source in 2019 and 2023.^[3]^[14]

References

^ ^a ^b Charlot, P.; et al. (2020), "The third realization of the International Celestial Reference Frame by very long baseline interferometry", Astronomy and Astrophysics, 644: A159, arXiv:2010.13625, Bibcode:2020A&A...644A.159C, doi:10.1051/0004-6361/202038368, S2CID 225068756.
^ Drinkwater, M. J.; et al. (January 1997), "The Parkes Half-Jansky Flat-Spectrum Sample", Monthly Notices of the Royal Astronomical Society, 284 (1): 85–125, arXiv:astro-ph/9609019, Bibcode:1997MNRAS.284...85D, doi:10.1093/mnras/284.1.85, ISSN 0035-8711.
^ ^a ^b ^c Dai, X.; et al. (March 2019), "Significant Flux Increase of Blazar PKS 0405-385 Detected by ASAS-SN", The Astronomer's Telegram, 12609, Bibcode:2019ATel12609....1D.
^ "QSO B0405-385". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2024-10-13.
^ ^a ^b Gong, Yunlu; et al. (June 2022), "Quasiperiodic Behavior in the γ-Ray Light Curve of the Blazar PKS 0405-385", The Astrophysical Journal, 931 (2), id. 168, arXiv:2205.02402, Bibcode:2022ApJ...931..168G, doi:10.3847/1538-4357/ac6c8c.
^ ^a ^b ^c ^d Kedziora-Chudczer, L.; et al. (November 1997), "PKS 0405-385: The Smallest Radio Quasar?", The Astrophysical Journal, 490 (1): L9–L12, arXiv:astro-ph/9710057, Bibcode:1997ApJ...490L...9K, doi:10.1086/311001.
^ ^a ^b ^c Kedziora-Chudczer, L. (June 2006), "Long-term monitoring of the intra-day variable quasar PKS 0405-385", Monthly Notices of the Royal Astronomical Society, 369 (1): 449–464, Bibcode:2006MNRAS.369..449K, doi:10.1111/j.1365-2966.2006.10321.x.
^ Cimo, G.; et al. (September 2004), Green, D. W. E. (ed.), "PKS 0405-385", IAU Circular, 8403: 1, Bibcode:2004IAUC.8403....1C.
^ ^a ^b ^c Protheroe, R. J. (May 2003), "The brightness temperature problem in extreme intra-day variable quasars: a model for PKS 0405-385", Monthly Notice of the Royal Astronomical Society, 341 (1): 230–238, arXiv:astro-ph/0301431, Bibcode:2003MNRAS.341..230P, doi:10.1046/j.1365-8711.2003.06429.x.
^ Kedziora-Chudczer, L. L.; et al. (1998), Zensus, J. A.; et al. (eds.), "PKS 0405-385 as Seen by the ISM Telescope", Radio Emission from Galactic and Extragalactic Compact Sources, IAU Colloquium 164, ASP Conference Series, vol. 144, p. 267, Bibcode:1998ASPC..144..267K.
^ Rickett, Barney J.; et al. (2002), "Interstellar Scintillation Explains the Intraday Variations in the Linear Polarisation of Quasar PKS 0405-385 at cm-wavelengths", Publications of the Astronomical Society of Australia, 19 (1): 106–110, Bibcode:2002PASA...19..106R, doi:10.1071/AS01119.
^ Rickett, Barney J.; et al. (December 2002), "Interstellar Scintillation of the Polarized Flux Density in Quasar PKS 0405-385", The Astrophysical Journal, 581 (1): 103–126, arXiv:astro-ph/0208307, Bibcode:2002ApJ...581..103R, doi:10.1086/344167.
^ Nowakowski, Tomasz (May 16, 2022), "Quasi-periodic oscillation detected in blazar PKS 0405-385", phys.org, retrieved 2024-10-12.
^ Bernard, Denis (August 2023), "Fermi-LAT detection of enhanced gamma-ray activity from the FSRQ PKS 0405-385", The Astronomer's Telegram, 16183, Bibcode:2023ATel16183....1B.