2025ApJ...985L..15A

Query : 2025ApJ...985L..15A

2025ApJ...985L..15A - Astrophys. J., 985, L15 (2025/May-3)

High Optical-to-X-Ray Polarization Ratio Reveals Compton Scattering in BL Lacertae's Jet.

AGUDO I., LIODAKIS I., OTERO-SANTOS J., MIDDEI R., MARSCHER A., JORSTAD S., ZHANG H., LI H., DI GESU L., ROMANI R.W., KIM D.E., FENU F., MARSHALL H.L., PACCIANI L., ESCUDERO PEDROSA J., ACEITUNO F.J., AGIS-GONZALEZ B., BONNOLI G., CASANOVA V., MORCUENDE D., PIIROLA V., SOTA A., KOUCH P.M., LINDFORS E., McCALL C., JERMAK H.E., STEELE I.A., BORMAN G.A., GRISHINA T.S., HAGEN-THORN V.A., KOPATSKAYA E.N., LARIONOVA E.G., MOROZOVA D.A., SAVCHENKO S.S., SHISHKINA E.V., TROITSKIY I.S., TROITSKAYA Y.V., VASILYEV A.A., ZHOVTAN A.V., MYSERLIS I., GURWELL M., KEATING G., RAO R., KANG S., LEE S.-S., KIM S., CHEONG W.Y., JEONG H.-W., ANGELAKIS E., KRAUS A., BLINOV D., MAHARANA S., BACHEV R., JORMANAINEN J., NILSSON K., FALLAH RAMAZANI V., CASADIO C., FUENTES A., TRAIANOU E., THUM C., GOMEZ J.L., ANTONELLI L.A., BACHETTI M., BALDINI L., BAUMGARTNER W.H., BELLAZZINI R., BIANCHI S., BONGIORNO S.D., BONINO R., BREZ A., BUCCIANTINI N., CAPITANIO F., CASTELLANO S., CAVAZZUTI E., CHEN C.-T., CIPRINI S., COSTA E., DE ROSA A., DEL MONTE E., DI LALLA N., DI MARCO A., DONNARUMMA I., DOROSHENKO V., DOVCIAK M., EHLERT S.R., ENOTO T., EVANGELISTA Y., FABIANI S., FERRAZZOLI R., GARCIA J.A., GUNJI S., HAYASHIDA K., HEYL J., IWAKIRI W., KAARET P., KARAS V., KISLAT F., KITAGUCHI T., KOLODZIEJCZAK J.J., KRAWCZYNSKI H., LA MONACA F., LATRONICO L., MALDERA S., MANFREDA A., MARIN F., MARINUCCI A., MASSARO F., MATT G., MITSUISHI I., MIZUNO T., MULERI F., NEGRO M., NG C.-Y., O'DELL S.L., OMODEI N., OPPEDISANO C., PAPITTO A., PAVLOV G.G., PEIRSON A.L., PERRI M., PESCE-ROLLINS M., PETRUCCI P.-O., PILIA M., POSSENTI A., POUTANEN J., PUCCETTI S., RAMSEY B.D., RANKIN J., RATHEESH A., ROBERTS O.J., SGRO C., SLANE P., SOFFITTA P., SPANDRE G., SWARTZ D.A., TAMAGAWA T., TAVECCHIO F., TAVERNA R., TAWARA Y., TENNANT A.F., THOMAS N.E., TOMBESI F., TROIS A., TSYGANKOV S.S., TUROLLA R., VINK J., WEISSKOPF M.C., WU K., XIE F. and ZANE S.

Abstract (from CDS):

Blazars, supermassive black hole systems with highly relativistic jets aligned with the line of sight, are the most powerful long-lived emitters of electromagnetic emission in the Universe. We report here on a radio-to-gamma-ray multiwavelength campaign on the blazar BL Lacertae with unprecedented polarimetric coverage from radio to X-ray wavelengths. The observations caught an extraordinary event on 2023 November 10-18, when the degree of linear polarization of optical synchrotron radiation reached a record value of 47.5%. In stark contrast, the Imaging X-ray Polarimetry Explorer found that the X-ray (Compton scattering or hadron-induced) emission was polarized at less than 7.4% (3σ confidence level). We argue here that this observational result rules out a hadronic origin of the high-energy emission and strongly favors a leptonic (Compton scattering) origin, thereby breaking the degeneracy between hadronic and leptonic emission models for BL Lacertae and demonstrating the power of multiwavelength polarimetry to address this question. Furthermore, the multiwavelength flux and polarization variability, featuring an extremely prominent rise and decay of the optical polarization degree, is interpreted for the first time by the relaxation of a magnetic “spring” embedded in the newly injected plasma. This suggests that the plasma jet can maintain a predominant toroidal magnetic field component parsecs away from the central engine.

Abstract Copyright: © 2025. The Author(s). Published by the American Astronomical Society.

Journal keyword(s): Active galaxies - BL Lacertae objects - Relativistic jets - Non-thermal radiation sources

Simbad objects: 2

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Number of rows : 2
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 QSO B1502+1041 Bla 15 04 24.97978391 +10 29 39.1985309   18.97 18.56 18.94   ~ 634 1
2 NAME BL Lac BLL 22 02 43.2913536816 +42 16 39.979416792   15.66 14.72     ~ 2397 1

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