An XMM-Newton look at the strongly variable radio-weak BL Lac Fermi J1544-0639

F. Ursini, L. Bassani, F. Panessa, E. Pian, G. Bruni, A. Bazzano, N. Masetti, K. Sokolovsky, P. Ubertini

Resultado de la investigación: Contribución a una revistaArtículo

Resumen

Context. Fermi J1544-0639/ASASSN-17gs/AT2017egv was identified as a gamma-ray/optical transient on May 15, 2017. Subsequent multiwavelength observations suggest that this source may belong to the new class of radio-weak BL Lacs. Aims. We studied the X-ray spectral properties and short-term variability of Fermi J1544-0639 to constrain the X-ray continuum emission mechanism of this peculiar source. Methods. We present the analysis of an XMM-Newton observation, 56 ks in length, performed on February 21, 2018. Results. The source exhibits strong X-ray variability, both in flux and spectral shape, on timescales of ∼10 ks, with a harder-when-brighter behaviour typical of BL Lacs. The X-ray spectrum is nicely described by a variable broken power law, with a break energy of around 2.7 keV consistent with radiative cooling due to Comptonization of broad-line region photons. We find evidence for a "soft excess", nicely described by a blackbody with a temperature of ∼0.2 keV, consistent with being produced by bulk Comptonization along the jet.

Idioma originalInglés
Número de artículoA116
PublicaciónAstronomy and Astrophysics
Volumen622
DOI
EstadoPublicada - 6 feb 2019

Áreas temáticas de ASJC Scopus

  • Astronomía y astrofísica
  • Ciencias planetarias y espacial

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    Ursini, F., Bassani, L., Panessa, F., Pian, E., Bruni, G., Bazzano, A., Masetti, N., Sokolovsky, K., & Ubertini, P. (2019). An XMM-Newton look at the strongly variable radio-weak BL Lac Fermi J1544-0639. Astronomy and Astrophysics, 622, [A116]. https://doi.org/10.1051/0004-6361/201834662