|Frankfurt Quasar Monitoring|
|TXS 0506+056 = MG 0509+0541|
|Cross-Identifications|| MG J0509+0541, TXS 0506+056, ZS 0506+056
QSO B0506+056, RX J0509.3+0541, 0506+056
2MASS J05092597+0541353, GB6 J0509+0541
87GB 050645.2+053747, 1FGL J0509.3+0540
EGR J0509+0550, 1RXS J050927.0+054145
CGRaBS J0509+0541, MG1 J050927+0541
|Equat. coordinates||RA 05 09 25.9 DE +05 41 35 (J2000)|
|Total mag range (mv) (5)||14.23 - 16.1|
|Catalog Magnitude (1)||16.00|
|Absolute Magnitude (1)||--- MB|
|Light Travel-Time (6)||3.78 × 109 yrs|
|1||15.143 (0.041)||14.495 (0.037)
|4||15.583 (0.023)||15.032 (0.055)|
|5||15.692 (0.023)||15.241 (0.050)|
||16.050 (0.114)||15.364 (0.035)|
||16.227 (0.095)||15.824 (0.056)|
| TXS 0506+056 = MG
0509+0541 is a variable BL Lac object in Orion, roughly 4° W of
Bellatrix (Gam Ori). The
designation TXS 0506+056
refers to the Texas Survey of Radiosources (TXS), where this object was discovered as a radio source in the period 1975-1981. |
The other designation, MG 0509+0541, stands for the MIT-Green Bank 5 GHz Survey (MG). During this radio survey the object was not only detected as well in 1981-82, but the stellar optical counterpart was identified on POSS plates with a magnitude of B=16.0 and R=15.5, respectively.
Today, TXS 0506+056 is classified as a BL Lac object due to its (nearly) featureless spectrum. It took until 2018, when the first redshift could be determined based on very weak emission lines, detected with the 10.4-metre Gran Telescopio Canarias.
TXS 0506+056 attracted attention in September 2017, when a high-energy neutrino was detected
by IceCube, designated IceCube-170922A. The arrival direction of this 290 TeV neutrino (!) was
consistent with the location of gamma-ray blazar TXS 0506+056 = MG 0509+0541, observed to be
in a flaring state (see light curve above) with enhanced gamma-ray activity in the GeV range.
As for most BL Lac objects, this source was found to be rapidly variable in the optical by nearly 2 magnitudes, ranging between 14.2 - 16.1 mag. During bright state, visual observers may observe this blazar with telescopes of 8- to 10-inch of aperture. The object appears stellar even with large apertures.
CCD observers, as well as visual observers, shall use the comparison stars given above.
TXS 0506+056 is located in eastern Orion, only about 4° W of Bellatrix (Gamma Ori). The constellation Orion is well known for its spectacular nebula landscapes, like the Great Orion Nebula M42/43 (12° SE), the Horse Head Nebula B33/IC 434 (11° SE) and the Flame Nebula NGC 2024 (11° SE), just to mention the most popular ones.
A more challenging deep sky object is another quasar, PKS 0405-12, a bright 14-mag stellar object at a distance of more than 5×109 light-years, located some 23° SW in Eridanus.
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