2025A&A...694A..46A

Query : 2025A&A...694A..46A

2025A&A...694A..46A - Astronomy and Astrophysics, volume 694A46 (2025/2-1)

Continuation of an optical spectroscopic campaign of Fermi blazar candidates with TNG: Discovery of a new changing-look blazar.

ALVAREZ CRESPO N., DOMINGUEZ A., PALIYA V.S., CHAMORRO CAZORLA M., SANCHEZ BLAZQUEZ P. and GIL DE PAZ A.

Abstract (from CDS):

Context. Blazars are a distinct subclass of active galactic nuclei (AGN), known for their fast variability, high polarization, and intense emission across the electromagnetic spectrum, from radio waves to gamma rays. Gamma-ray blazar candidates of uncertain type (BCU) are an ongoing challenge in gamma-ray astronomy due to difficulties in classification and redshift determination.
Aims. This study continues an optical spectroscopic campaign aimed at identifying the characteristics of BCUs to improve classification and redshift estimates, particularly focusing on low-synchrotron-peak sources.
Methods. We conducted a detailed analysis of optical spectroscopic data for a sample of 21 low-synchrotron-peak BCUs plus one bl lac with contradictory results in the literature, using the 3.58-m Telescopio Nazionale Galileo (TNG, La Palma, Spain).
Results. Our analysis identifies 14 out of the 21 BCUs as flat-spectrum radio quasars (FSRQs), demonstrating the effectiveness of our selection criteria. Notably, four FSRQs have redshifts exceeding 1, including 4FGL J2000.0+4214 at z = 2.04. Six sources are classified as bl lacs, with one of them, 4FGL J0746.5-0719, showing a featureless spectrum in this work despite previously exhibiting strong lines, suggesting it may be a changing-look blazar. One source remains classified as a BCU due to a noisy spectrum. Additionally, we observed a bl lac object, 4FGL J1054.5+2211, due to inconsistent redshift estimates in the literature, but we could not confirm any redshift due to its featureless spectrum. Our findings provide insights into the classification and redshift estimation of blazar candidates, emphasizing the need for continued spectroscopic monitoring.

Abstract Copyright: © The Authors 2025

Journal keyword(s): galaxies: active - BL Lacertae objects: general - galaxies: distances and redshifts

Simbad objects: 33

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Number of rows : 33
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 4FGL J0128.2+4400 Bz? 01 28 17.6 +44 00 06           ~ 12 0
2 NVSS J012826+440430 Rad 01 28 26.17 +44 04 29.5           ~ 4 1
3 4FGL J0138.6+2923 Bz? 01 38 39.3 +29 23 08           ~ 4 0
4 4FGL J0304.5+3349 Bz? 03 04 33.1 +33 49 34           ~ 8 0
5 4C 33.06 QSO 03 04 41.36244275 +33 48 43.5308746           ~ 37 1
6 4FGL J0328.9+3514 Bz? 03 28 58.4 +35 14 56           ~ 6 0
7 3FHL J0429.7+2845 BLL 04 29 49.9 +28 43 09           ~ 22 0
8 NVSS J042950+284252 Rad 04 29 49.9894213152 +28 42 53.133395688           ~ 6 1
9 4FGL J0436.2-0038 Bz? 04 36 12.1 -00 38 49           ~ 14 0
10 NVSS J043614-003637 BLL 04 36 14.5798 -00 36 38.601           ~ 2 0
11 3FGL J0539.2-0536 Bz? 05 39 45.8 -05 21 20           ~ 14 0
12 PMN J0540-0514 rG 05 39 59.9373092016 -05 14 41.300066796           ~ 20 1
13 4FGL J0614.8+6136 Bz? 06 14 53.1 +61 36 28           ~ 12 0
14 7C 070112.19+450709.00 BLL 07 04 50.9696880576 +45 02 41.819661132           ~ 22 2
15 4FGL J0713.0+5738 Bz? 07 13 02.4 +57 38 04           ~ 9 0
16 GB6 J0713+5738 Rad 07 13 04.547 +57 38 10.12           ~ 5 0
17 NVSS J073258+491657 Rad 07 32 58.4404 +49 16 59.078           ~ 4 1
18 4FGL J0733.0+4915 Bz? 07 33 03.8 +49 15 24           ~ 7 0
19 2MASS J07462747-0709498 QSO 07 46 27.4935479828 -07 09 49.630479430           ~ 33 0
20 87GB 105148.6+222705 BLL 10 54 30.6250887672 +22 10 54.796074852 17.67 17.39 17.20 17.1   ~ 68 1
21 4FGL J1229.1+5521 Bz? 12 29 11.4 +55 21 07           ~ 6 0
22 2MASS J15165000+2636369 QSO 15 16 50.0092057224 +26 36 37.077498468   18.33 18.01     ~ 37 0
23 4FGL J1556.6+1417 Bz? 15 56 36.8 +14 17 09           ~ 7 0
24 NVSS J155645+141549 rG 15 56 45.5716263419 +14 15 49.070066310           ~ 3 1
25 4FGL J1754.7+3444 Bz? 17 54 43.0 +34 44 30           ~ 8 0
26 GB6 B1753+3443 Rad 17 54 52.0 +34 43 15           ~ 3 0
27 ICRF J195922.0+384654 QSO 19 59 22.03929689 +38 46 54.1656101           ~ 35 1
28 PSO J299.9948+42.2296 Bla 19 59 58.7685155508 +42 13 46.740125678           ~ 33 1
29 NVSS J212031+443433 Rad 21 20 31.77414308 +44 34 34.2655623           ~ 27 1
30 4FGL J2120.7+4428 Bz? 21 20 46.5 +44 28 53           ~ 8 0
31 4FGL J2139.1+3724 Bz? 21 39 09.2 +37 24 47           ~ 6 0
32 4FGL J2317.0+3756 Bz? 23 17 04.3 +37 56 15           ~ 6 0
33 NVSS J231710+375948 Rad 23 17 10.2775464264 +37 59 48.328085364           ~ 6 1

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