2025A&A...700A.229L

Query : 2025A&A...700A.229L

2025A&A...700A.229L - Astronomy and Astrophysics, volume 700A229 (2025/8-1)

Exploring the most extreme gamma-ray blazars using broadband spectral energy distributions.

LAINEZ M., NIEVAS-ROSILLO M., DOMINGUEZ A., CONTRERAS J.L., GONZALEZ J.B., DINESH A. and PALIYA V.S.

Abstract (from CDS):

Context. Extreme high-synchrotron peaked blazars (EHSPs) are rare high-energy sources characterised by synchrotron peaks beyond 1017 Hz in their spectral energy distributions (SEDs). Their extreme properties challenge conventional blazar emission models and provide a unique opportunity to test the limits of particle acceleration and emission mechanisms in relativistic jets. However, the number of identified EHSPs is still small, limiting comprehensive studies of their population and characteristics.
Aims. This study aims to identify new EHSP candidates and characterise their emission properties, including synchrotron peak frequencies, Compton dominance, and jet environments. It also examines how EHSPs fit within the broader framework of the blazar sequence, providing insights into their role in the population of active galactic nuclei.
Methods. A sample of 124 γ-ray blazars was analysed, selected for their high synchrotron peak frequencies and γ-ray emission properties, with a focus on sources showing low variability and good broadband data coverage. Their SEDs were constructed using archival multi-wavelength data from the SSDC SED Builder service, supplemented with recent Swift-UVOT, Swift-XRT, and Fermi-LAT observations. The SEDs were modelled with a one-zone synchrotron/synchrotron-self-Compton framework, classifying sources by synchrotron peak frequency. EHSP properties are compared to other blazar populations, and their detectability with the Cherenkov Telescope Array Observatory (CTAO) is assessed.
Results. We identify 66 new EHSP candidates, significantly expanding the known population. A clear correlation between synchrotron peak frequency and the magnetic-to-kinetic energy density ratio is found, with the most extreme EHSPs nearing equipartition. This indicates that as the synchrotron peak shifts to higher frequencies, the energy stored in the magnetic field becomes comparable to that of the relativistic electrons, suggesting a more balanced and energetically efficient jet environment in the most extreme blazars. Host galaxy emission is detected in many sources, but no significant differences are observed between elliptical and lenticular hosts. Finally, our analysis suggests that nine high-synchrotron peaked/EHSPs could be observed by CTAO at >5σ (20 at >3σ) in 20-hour exposures, a feasible integration time for Imaging Atmospheric Cherenkov Telescopes, indicating that while the overall detection rate remains modest, a subset of these sources is within reach of next-generation very-high-energy gamma-ray instruments.

Abstract Copyright: © The Authors 2025

Journal keyword(s): radiation mechanisms: non-thermal - galaxies: active - BL Lacertae objects: general - galaxies: jets

VizieR on-line data: <Available at CDS (J/A+A/700/A229): tablec1.dat tablec2.dat table2.dat>

Simbad objects: 126

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Number of rows : 126
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 1RXS J000320.4-524727 BLL 00 03 19.5968903177 -52 47 27.278010635           ~ 36 1
2 2MASS J00083540-2339279 BLL 00 08 35.3995342872 -23 39 28.008110844     17.90     ~ 49 1
3 2MASX J00135605-1854066 BLL 00 13 56.0426451480 -18 54 06.702770232   17.01   15.82   ~ 86 1
4 2MASS J00292862+2053339 Bla 00 29 28.6066603763 +20 53 33.900675689           ~ 19 0
5 PMN J0039-2220 BLL 00 39 08.2102455744 -22 20 01.478410368   16.29       ~ 63 1
6 RX J0049.6-4151 BLL 00 49 38.9453193927 -41 51 37.527882036           ~ 29 1
7 HE 0052-2511 BLL 00 54 46.7593476432 -24 55 29.219073024 17.06 16.85 16.78     ~ 57 0
8 RX J0059.2-0150 Bla 00 59 16.9278313536 -01 50 17.664890784   17.5       ~ 51 1
9 PMN J0102-2001 Bla 01 02 50.9622625673 -20 01 58.330689204           ~ 27 1
10 NVSS J012152-391547 rG 01 21 52.7000848821 -39 15 44.288893145           ~ 27 1
11 2MASS J01233839-2310585 BLL 01 23 38.3498181576 -23 10 58.873955124     19.00 17.6   ~ 43 1
12 1RXS J012657.1+330730 BLL 01 26 57.2379078072 +33 07 30.315326268     17.70 18.7   ~ 30 0
13 [VV2006] J013241.1-080406 BLL 01 32 41.1259581192 -08 04 04.837806948   17.51 16.50 15.86   ~ 56 1
14 2MASX J01464857-5202332 BLL 01 46 48.5843293896 -52 02 33.647970516   16.79   15.19   ~ 67 1
15 PMN J0150-5450 BLL 01 50 44.5339581141 -54 50 05.057783770           ~ 30 1
16 SDSS J020226.41+084913.6 BLL 02 02 26.4227476680 +08 49 13.691480520     19.00 19   ~ 53 1
17 1RXS J021206.0-255808 Bla 02 12 05.7611260363 -25 57 58.383836515           ~ 20 0
18 RX J0216.5+2314 BLL 02 16 32.0944044336 +23 14 50.353758528       18.4   ~ 36 0
19 1RXS J023428.6+804341 Bla 02 34 30.6135943747 +80 43 37.273811400           ~ 19 0
20 1RXS J024151.6-160339 Bla 02 41 51.4039213238 -16 03 33.636046962           ~ 19 1
21 RX J0304.5-0054 BLL 03 04 33.9589424424 -00 54 04.710232836   19.58 18.96 18.3   ~ 46 1
22 NVSS J030515-160814 BLL 03 05 15.0695002294 -16 08 16.687113582           ~ 50 1
23 1RXS J030926.2-395927 Bla 03 09 26.0600477592 -39 59 28.185201852           ~ 18 1
24 RX J0314.3+0620 BLL 03 14 23.9279493480 +06 19 56.525566764       17.5   ~ 45 1
25 1RXS J032342.6-011131 BLL 03 23 43.6189299792 -01 11 46.206256992 17.67 17.48 16.96 17.4   ~ 27 1
26 1FGL J0323.7-0106 mul 03 23 45.3 -01 11 25           ~ 57 0
27 NVSS J033050-240612 Bz? 03 30 50.0338878777 -24 06 12.041162023           ~ 16 0
28 1RXS J033623.3-034727 BLL 03 36 23.8026141624 -03 47 38.594258592   18.53   16.91   ~ 38 0
29 1RXS J035725.7-031740 BL? 03 57 26.1013040739 -03 17 59.502335776           ~ 17 0
30 1RXS J035855.6-305437 BLL 03 58 56.1047599056 -30 54 47.886192072           ~ 28 0
31 1RXS J040928.4+320251 BL? 04 09 28.5141243132 +32 02 46.119516404           ~ 22 0
32 1RXS J042012.8-601446 AGN 04 20 11.0300589689 -60 15 05.167986705           ~ 25 0
33 1RXS J042900.5-323633 BLL 04 29 00.1791493200 -32 36 41.096135520     19.00 18.3   ~ 23 0
34 2FGL J0440.9+2749 BLL 04 40 50.3648111616 +27 50 46.889071404       18.4   ~ 53 1
35 1RXS J044127.8+150455 BLL 04 41 27.4667781960 +15 04 55.600800780       18.4   ~ 29 0
36 1RXS J050335.6-111504 BLL 05 03 35.4199786056 -11 15 06.738530040       19.9   ~ 27 0
37 PMN J0505+0416 BLL 05 05 34.7693853576 +04 15 54.577536876 18.07 17.80 17.56 16.8   ~ 83 1
38 NVSS J050650+032401 BLL 05 06 50.1481553527 +03 23 58.762381653           ~ 29 1
39 1RXS J050938.3-040037 BLL 05 09 38.1791014104 -04 00 45.682814376   19.10   17.92   ~ 78 0
40 NVSS J052645-151900 Bla 05 26 45.4471523354 -15 19 00.394839948         16.558 ~ 20 0
41 1RXS J053629.4-334302 BLL 05 36 29.0674147920 -33 43 02.465333796 17.11 16.97 16.93 16.8   ~ 58 1
42 2FGL J0537.7-5716 BLL 05 37 48.9538387032 -57 18 30.099289860 17.85 17.77 17.34     ~ 48 0
43 1RXS J055717.0-061705 Bla 05 57 16.8396368306 -06 17 06.828429628           ~ 22 0
44 PMN J0558-3839 BLL 05 58 06.4316057352 -38 38 31.590709152   17.50 17.1     ~ 93 1
45 ESO 254-17 BLL 06 06 35.7349083888 -47 29 54.821851188   14.63 14.6 12.76   ~ 59 1
46 1RXS J061105.7+432352 BLL 06 11 06.59117 +43 23 57.4542           ~ 30 1
47 1RXS J064444.2-285120 BLL 06 44 43.7639388123 -28 51 16.720471211           ~ 31 1
48 ATO J112.6086+33.1230 BLL 07 30 26.0641211808 +33 07 22.907483652     17.38 17.4   ~ 52 0
49 RX J0731.8+2804 BLL 07 31 52.7289827136 +28 04 32.936159892       16.2   ~ 44 1
50 2FGL J0737.5-8246 BLL 07 37 06.09652 -82 48 40.0144           ~ 33 0
51 1RXS J074707.6+851211 BLL 07 47 16.1527432872 +85 12 08.624543324           ~ 38 0
52 1RXS J075936.1+132123 Bla 07 59 36.1360145184 +13 21 17.841223152           ~ 22 0
53 1RXS J080458.3-062432 BLL 08 04 57.7391420976 -06 24 26.201080368   18.9   17.0   ~ 31 1
54 NVSS J081338-035716 BLL 08 13 38.0632797594 -03 57 17.317406787           ~ 25 1
55 RX J0819.2-0756 BLL 08 19 17.5832101176 -07 56 26.141444304       18.4   ~ 43 0
56 1RXS J082904.5+175415 BLL 08 29 04.8275335680 +17 54 15.865834356           ~ 63 1
57 2MASS J08422550+0252524 BLL 08 42 25.5099162360 +02 52 52.694388300   19.93 19.26 17.8   ~ 44 0
58 2MASX J08503620+3455231 BLL 08 50 36.1948739592 +34 55 22.779038172   18.73 17.85 14.3   ~ 74 1
59 RX J0909.0+2311 BLL 09 09 00.6253772472 +23 11 12.975311832       16.7   ~ 70 1
60 PMN J0912-2103 BLL 09 13 00.2229216720 -21 03 21.039728508   17.82   16.42   ~ 82 1
61 1RXS J092057.2-225716 BLL 09 20 57.4792644359 -22 57 21.376854316           ~ 29 0
62 RX J0924.0+0533 BLL 09 24 01.0396071048 +05 33 45.408775212   18.96 18.65 18.2   ~ 43 1
63 RX J0954.1+4914 BLL 09 54 09.8719327752 +49 14 59.557692012   19.33 19.10 19.5   ~ 75 0
64 M 82 AGN 09 55 52.430 +69 40 46.93 9.61 9.30 8.41     ~ 6156 6
65 1RXS J095627.2-095720 Bla 09 56 28.2142037784 -09 57 19.191491424   17       ~ 28 1
66 NVSS J102100+162553 BLL 10 21 00.3533388672 +16 25 54.017072220       18.4   ~ 23 0
67 RX J1107.8+1502 BLL 11 07 48.0634235400 +15 02 10.558629456     18.20     ~ 70 1
68 RX J1123.8+7230 BLL 11 23 49.1707779048 +72 29 59.649084744           ~ 38 0
69 1RXS J113209.3-473844 Bla 11 32 09.2583762628 -47 38 53.358834060           ~ 28 0
70 2MASS J12132311-2618075 BLL 12 13 23.1258631512 -26 18 07.803817092   17.8 19.0 17.6   ~ 47 1
71 1RXS J122534.0-344737 BLL 12 25 36.8191255384 -34 47 21.763020315           ~ 30 1
72 NVSS J123123+142123 BLL 12 31 23.9056875672 +14 21 24.429803472     17.70 16.9   ~ 75 0
73 2MASS J12362302+3900012 BLL 12 36 23.0166791832 +39 00 00.971219484   19.34 18.65 17.5   ~ 51 0
74 RX J1237.6+6258 BLL 12 37 39.0753390528 +62 58 42.801146328   18.89 18.25 17   ~ 116 0
75 PMN J1241-1456 BLL 12 41 49.3631635080 -14 55 58.509612984     17.90 17.7   ~ 55 1
76 PMN J1253-3932 BLL 12 53 41.2576033944 -39 31 59.450276892   18.73   17.18   ~ 35 1
77 2FGL J1256.5-1145 BLL 12 56 15.9520325496 -11 46 37.335959904   16.39   15.07   ~ 67 1
78 RX J1310.2-1157 BLL 13 10 12.4576837032 -11 57 46.687156416   17.34   16.00   ~ 38 0
79 LBQS 1308+0051 BLL 13 11 06.4762326096 +00 35 10.045283820   18.53 18.01     ~ 60 0
80 NVSS J132617+123006 BLL 13 26 17.7036437760 +12 29 58.736692644   19.51 18.63 16.6   ~ 50 0
81 RX J1331.0+5655 BLL 13 31 02.9152240728 +56 55 41.759497704   20.49 19.45     ~ 33 0
82 RX J1336.1+2320 BLL 13 36 12.1589772816 +23 19 58.041745932       18.2   ~ 35 0
83 NVSS J134042-041006 BLL 13 40 42.0173568000 -04 10 07.046694084           ~ 46 1
84 RX J1353.4+5601 BLL 13 53 28.0474623240 +56 00 56.986350984   19.31 18.92 16.4   ~ 43 0
85 2MASS J14002208-4008235 Bla 14 00 22.08072 -40 08 23.5572           ~ 14 0
86 FIRST J141927.4+044513 BLL 14 19 27.5002614096 +04 45 13.731125256   18.80 18.31     ~ 60 0
87 2MASS J14395085-3955185 BLL 14 39 50.85960 -39 55 18.5988           ~ 30 0
88 2MASS J14405293+0610162 BLL 14 40 52.9387587024 +06 10 16.192432236 17.77 17.41 17.34     ~ 76 1
89 4FGL J1447.0-2657 Bz? 14 46 56.8503565804 -26 56 58.313021856           ~ 26 1
90 1RXS J150636.4-054011 BLL 15 06 37.1078795520 -05 40 04.824178464     20.0 19.1   ~ 24 0
91 PMN J1518+0613 Bla 15 18 45.7276771080 +06 13 56.112249504   16.65   15.37   ~ 66 1
92 RX J1532.0+3016 BLL 15 32 02.2318415520 +30 16 28.855961652           ~ 97 1
93 RX J1533.1+1854 BLL 15 33 11.2518579384 +18 54 29.054401704           ~ 64 0
94 RX J1533.4+3416 BLL 15 33 24.2707322904 +34 16 40.306756692   18.59 18.31 18.1   ~ 62 0
95 2MASS J15344720+3715545 BLL 15 34 47.2078521912 +37 15 54.618295464   18.26 17.57     ~ 89 1
96 PMN J1539-1128 BLL 15 39 41.1987284184 -11 28 35.428726344         16.848 ~ 38 1
97 NVSS J155432-121322 Bla 15 54 32.5971424603 -12 13 25.283970061           ~ 17 0
98 RX J1605.3+5421 BLL 16 05 19.0570123248 +54 20 59.952793272 19.39 19.80 19.08 18.9   ~ 50 1
99 1RXS J163717.1+131418 BLL 16 37 16.7397764544 +13 14 38.783839668   19.61 19.09 18.3   ~ 31 0
100 1RXS J165655.0-201049 BLL 16 56 55.1472819362 -20 10 56.345720505           ~ 35 1
101 1RXS J171921.2+120711 BLL 17 19 21.4981636892 +12 07 21.942105019           ~ 32 1
102 RX J1757.2+7033 BLL 17 57 13.0521071712 +70 33 37.820087172       18   ~ 87 1
103 1RXS J180847.3+241923 Bla 18 08 45.6981784272 +24 19 05.617585751           ~ 16 0
104 SDSS J182419.05+430949.5 BLL 18 24 19.0466236321 +43 09 49.396418758           ~ 45 1
105 RX J1841.3+2909 BLL 18 41 21.7201454496 +29 09 41.032048536   17.6   16.7   ~ 42 1
106 1RXS J184822.6+653700 BLL 18 48 22.4966893920 +65 36 57.823557264       18.6   ~ 31 0
107 1RXS J185024.6+263159 Bla 18 50 24.0290262072 +26 31 53.688230364           ~ 21 0
108 1RXS J192325.9-250228 BL? 19 23 25.4194639178 -25 02 08.733087379           ~ 16 0
109 1RXS J194422.6-452326 BLL 19 44 22.3904632368 -45 23 32.530725708           ~ 43 1
110 1RXS J195503.1-564031 BLL 19 55 02.8617649615 -56 40 28.814904257           ~ 41 1
111 PKS J2015+1622 Bla 20 15 03.8152445868 +16 22 27.339640591           ~ 31 1
112 SUMSS J202143-722609 BLL 20 21 43.8839510029 -72 26 11.864268033           ~ 18 0
113 RX J2030.8+1935 BLL 20 30 57.1340134032 +19 36 12.930528420           ~ 59 2
114 SUMSS J203451-420024 BLL 20 34 51.0909972120 -42 00 38.437476084           ~ 43 1
115 2MASS J20400660-4620180 Bla 20 40 06.60720 -46 20 18.0960           ~ 17 0
116 LEDA 621219 Bla 20 41 50.2441037088 -37 33 39.982399236   17.45   15.95   ~ 33 1
117 1RXS J205242.6+081039 BLL 20 52 42.6125135040 +08 10 40.625854752       18.9   ~ 26 0
118 2MASS J21124295+0818355 BLL 21 12 43.0067060867 +08 18 35.251701198           ~ 38 2
119 PMN J2145+0720 BLL 21 45 52.2999532008 +07 19 27.205685508       16   ~ 120 1
120 1RXS J223249.5-202232 BLL 22 32 48.7981989312 -20 22 26.127442200           ~ 32 0
121 1RXS J224642.0-520638 Bla 22 46 42.1007015532 -52 06 40.394463736     18.2     ~ 55 1
122 PMN J2258-5526 BLL 22 58 18.9908859024 -55 25 37.397815356           ~ 61 1
123 1RXS J230636.0-110350 BLL 23 06 34.9995759288 -11 03 48.248438076     19.30 20   ~ 23 0
124 MCG-07-47-031 BLL 23 19 05.8954756632 -42 06 48.297034584   16.60 15.46     ~ 121 0
125 2FGL J2341.7+8016 BLL 23 40 54.2290641384 +80 15 16.020826848     18.90 16.8   ~ 59 1
126 NVSS J235612+403648 Bla 23 56 12.7423370256 +40 36 46.976785524           ~ 40 1

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