Disentangling the nature of the prototype radio weak BL Lac

Contemporaneous multifrequency observations of WISE J141046.00+740511.2

¹ INAF – Osservatorio di Astrofisica e Scienza dello Spazio, Via Gobetti 93/3, 40129 Bologna, Italy
e-mail: ezequiel.marchesini@inaf.it
² Instituto de Astrofísica de La Plata, CONICET–UNLP, CCT La Plata, Paseo del Bosque, B1900FWA La Plata, Argentina
³ Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque, B1900FWA La Plata, Argentina
⁴ Instituto Argentino de Radioastronomía, CONICET-CICPBA-UNLP, CC5 (1894) Villa Elisa, Prov. de Buenos Aires, Argentina
⁵ Dipartimento di Fisica e Astronomia “Augusto Righi”, Università di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
⁶ Complejo Astronómico “El Leoncito” (CASLEO), CONICET-UNLP-UNC-UNSJ, San Juan, Argentina
⁷ Instituto de Astrofísica, Facultad de Ciencias Exactas, Universidad Andrés Bello, Fernández Concha 700, Las Condes, Santiago, RM, Chile
⁸ INFN – Istituto Nazionale di Fisica Nucleare, Sezione di Torino, Via Pietro Giuria 1, 10125 Turin, Italy
⁹ Dipartimento di Fisica, Università degli Studi di Torino, Via Pietro Giuria 1, 10125 Turin, Italy
¹⁰ East Asian Observatory, 660 North A’ohōkū Place, Hilo, Hawaii 96720, USA
¹¹ Instituto Nacional de Astrofísica, Óptica y Electrónica, Luis Enrique Erro #1, Tonantzintla, Puebla 72840, Mexico
¹² Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
¹³ Departamento de Física (EPS), Universidad de Jaén, Campus Las Lagunillas s/n, A3, 23071 Jaén, Spain
¹⁴ Instituto de Astrofísica de Canarias (IAC), 38205 La Laguna, Tenerife, Spain
¹⁵ Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
¹⁶ Instituto de Astrofísica de Andalucía – CSIC, Glorieta de la Astronomía, S/N, 18008 Granada, Spain
¹⁷ Department of Physics & Astronomy, University of Southampton, Southampton SO17 1BJ, UK

Received: 6 September 2022
Accepted: 4 November 2022

Abstract

Context. The γ-ray emitting source WISE J141046.00+740511.2 has been associated with a Fermi-LAT detection by crossmatching with Swift/XRT data. It has shown all the canonical observational characteristics of a BL Lac source, including a power-law, featureless optical spectrum. However, it was only recently detected at radio frequencies and its radio flux is significantly low.

Aims. Given that a radio detection is fundamental to associate lower-energy counterparts to Fermi-LAT sources, we aim to unambiguously classify this source by performing a multiwavelength analysis based on contemporaneous data.

Methods. By using multifrequency observations at the Jansky Very Large Array, Giant Metrewave Radio Telescope, Gran Telescopio Canarias, Gemini, William Herschel Telescope and Liverpool observatories, together with Fermi-LAT and Swift data, we carried out two kinds of analyses. On one hand, we studied several known parameters that account for the radio loudness or weakness characterization and their application to blazars (in general) and to our source (in particular). And, on the other hand, we built and analyzed the observed spectral energy distribution (SED) of this source to try to explain its peculiar characteristics.

Results. The multiwavelength analysis indicates that WISE J141046.00+740511.2 is a blazar of the high-frequency peaked (HBL) type that emits highly polarized light and that is likely located at a low redshift. In addition, the one-zone model parameters that best fit its SED are those of an extreme HBL (EHBL); this blazar type has been extensively predicted in theory to be lacking in the radio emission that is otherwise typical of canonical γ-ray blazars.

Conclusions. We confirm that WISE J141046.00+740511.2 is indeed a highly polarized BL Lac of the HBL type. Further studies will be conducted to explain the atypical low radio flux detected for this source.