Two new Blazars behind the Milky Way and their Fermi-LAT 2FGL identifications

ATel #4243; G. Tsarevsky (Astro Space Center RAS, Moscow & ASA, Sydney), N. Kardashev (Astro Space Center RAS), O. B. Slee (CASA-ATNF, Sydney), V. Goranskij (SAI, Moscow University), J. de Freitas Pacheco, P. de Laverny & F. Thevenin (Observatoire de la Cote dAzur, Nice, France), E. Barsukova & A. Burenkov (SAO RAS, Russia), R. Stathakis (AAO, Sydney)
on 8 Jul 2012; 06:37 UT
Credential Certification: Gregory S. Tsarevsky (Greg.Tsar@gmail.com)

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We report on detection of two objects with featureless optical spectra discovered in the course of a systematic search near the plane of the Galaxy for so-called very active stars (VASC, or possible microquasars). They are characterized by a hard X-ray binary-like spectrum (Motch, C. et al. 1998, A&AS 132, 341) and activity in the radio domain.
The VAS candidates have been selected from the Bright ROSAT Source Catalogue (1XRS) in the Zone of Avoidance ( b < 20d), and were tentatively identified in the GB6/PMM/NVSS radio surveys. Most of them were observed at 4.8 and 8.6 GHz with the Australia Telescope Compact Array (ATCA) and Very Large Array (VLA).
Precise radio coordinates have led to optical identifications for 60 VASCs, and a sub-sample of five of them were observed with the AAT (3.9-m), BTA (6-m) and VLT (8-m) telescopes. Moderate-dispersion spectroscopy revealed that two of these five are compact sources with featureless spectra (see Tsarevsky et al. 2005, A&A, 438, 949). This puts them into the BL Lac type objects. Also, their flat-like radio spectra are compatible with the suggested blazar classification.
Additionally, the WISE IR colors of VASC J1942+10 obey well the BLL (BZB) classification and, also, the BZB – Gamma-ray association due to the WISE Gamma-ray Blazar Strip (WGS) criterion developed by Massaro F., et al. (2012 ApJ, 750, 138) - as clearly illustrated in Fig 2 taken from that paper.
Unfortunately VASC J1353-66 is somewhat below of the WISE detection level.
The equivalent widths (EW) of the interstellar NaI D1 line measured in the VLT spectra are saturated for both sources, which implies that they are highly reddened distant objects.

These sources have good identifications in the Fermi-LAT 2FGL Catalog at the >95% confidence level as presented below in the table (with corresponding radio – Gamma-ray positional offsets):

 
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              Radio Coordinates:        b   Optical    Blazar 2FGL Catalog      r-Gamma        
VASC Name     RA J2000     DEC J2000  [deg] Spectrum    Type  Identification    [arcm]  Note   
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VASC J1353-66 13 53 40.15 -66 39 57.6 -4.5  featureless  BZB? 2FGL J1353.5-6640   1.2    1    
VASC J1942+10 19 42 47.48 +10 33 27.1 -6.4  featureless  BZB  2FGL J1942.8+1033   0.6    2    
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Notes:
1. VASC J1353-66: due to the NOMAD database, it shows marginal evidence of proper motion. If confirmed, it would imply the discovery of a new type of galactic source. So we encourage precise astrometry of this possibly unique object. Until that is done, its BLL (BZB) classification is doubtful.
2. VASC J1942+10: this flat-like spectrum, ~100 mJy flux density BZB-2FGL object is a prospective target for further investigation with high resolution Space – Ground RadioAstron Interferometer.
A summary Table with all mentioned multifrequency parameters is posted at ftp://www.asc.rssi.ru/Gregory.Tsarevsky/.
We are grateful to M. Rupen for the JVLA 4.8 GHz observations of many VASC objects.