| PKS 0405–385 | |
|---|---|
 The blazar PKS 0405-385. | |
| Observation data (Epoch J2000.0) | |
| Constellation | Eridanus |
| Right ascension | 04 06 59.035 |
| 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 in the constellation of Eridanus. This is a compact radio quasar with a redshift (z) of 1.285, an indicator of its significant distance. The radio spectrum of this source appears flat, making it a flat-spectrum radio quasar (FSRQ).
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. Examination using VLBI shows the radio source spans less than five microarcseconds (μas) in angle. 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. The radio flux was also found to vary on longer timescales for periods of a month or two.
If the short-term variation were due to the quasar, it would imply an extreme brightness temperature of about 10 K. Instead, it was proposed that the variation was the result of interstellar scintillation due to ionized clouds in the Milky Way. The radio emission from the quasar underwent rotation of linear polarization during these events, lending support to the idea of scintillation. 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 2.0×10 K. The episodic nature of the rapid variations may be explained by changes in the quasar or the interstellar medium. PKS 0405–385 is one of only three known extreme scintillators, the others being PKS 1257−326 and J1819+385.
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. Enhanced gamma ray activity was observed from this source in 2019 and 2023.
References
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
