BL Lacertae objects from the EXOSAT high galactic latitude survey: Constraints on the LogN-LogS and on the cosmological evolution

2005 ◽  
pp. 231-241 ◽  
Author(s):  
P. Giomm ◽  
G. Tagliaferri ◽  
K. Beuermann ◽  
G. Branduardi-Raymont ◽  
R. Brissenden ◽  
...  
Keyword(s):  
Cosmological Evolution ◽  
Galactic Latitude ◽  
Bl Lacertae Objects ◽  
High Galactic Latitude ◽  
Bl Lacertae

The luminosity function and cosmological evolution of X-ray-selected BL Lacertae objects

1991 ◽  
Vol 380 ◽  
pp. 49 ◽  
Author(s):  
Simon L. Morris ◽  
John T. Stocke ◽  
Isabella M. Gioia ◽  
Rudy E. Schild ◽  
Anna Wolter ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Cosmological Evolution ◽  
Bl Lacertae Objects ◽  
X Ray ◽  
Bl Lacertae

On the Cosmological Evolution of BL Lacertae Objects

2002 ◽  
Vol 566 (1) ◽  
pp. 181-186 ◽  
Author(s):  
A. Caccianiga ◽  
T. Maccacaro ◽  
A. Wolter ◽  
R. Della Ceca ◽  
I. M. Gioia
Keyword(s):  
Cosmological Evolution ◽  
Bl Lacertae Objects ◽  
Bl Lacertae

scholarly journals SAO 244567 (HEN1357): A Post-Agb Star which has turned into a Planetary Nebula within the last 20 years

1998 ◽  
Vol 11 (1) ◽  
pp. 358-358
Author(s):  
M. Parthasarathy
Keyword(s):  
Planetary Nebula ◽  
Far Infrared ◽  
Central Star ◽  
Terminal Velocity ◽  
Galactic Latitude ◽  
Iras Source ◽  
High Galactic Latitude ◽  
Alpha Emission ◽  
Early Type Star ◽  
Emission Strength

SAO 244567 (Henl357) (IRAS 17119-5926) is a high galactic latitude (1 = 331°, b = −12°) early type star, originally classified as a B or A type H-alpha emission line star by Henize (1976). It is an IRAS source with far infrared colours similar to planetary nebulae. The IUE ultraviolet spectra obtained during the last eight years show that the central star is rapidly evolving. It is found that the central star of this young PN has faded by a factor of 3 within the last seven eight years. The terminal velocity of the stellar wind has decreased from −3500 km/sec in 1988 to almost zero in 1994. In 1988 the C IV (1550A) line which was a P-Cygni profile with strong absorption component had almost vanished by 1994. The CIII] 1909A emission strength increased markedly within 4 years from 1988 to 1992. The optical spectra obtained since 1990 shows very clearly only the nebular spectrum which is very similar to that of low excitation planetary nebula. The optical spectrum of SAO 244567 obtained in 1971 shows that it was a post-AGB B 1 or B2 supergiant at that time. This result shows that SAO 244567 has turned into a planetary nebula within the last 20 years. Recently Bobrowsky (1994) obtained narrowband optically resolved images in both H-beta and [OIII] 5007A with the HST planetary camera which revealed a well resolved nebula of size 2 seconds of arc. In this paper we discuss the recent new results.

scholarly journals Unexpected circular radio objects at high Galactic latitude

2021 ◽  
Vol 38 ◽  
Author(s):  
Ray P. Norris ◽  
Huib T. Intema ◽  
Anna D. Kapińska ◽  
Bärbel S. Koribalski ◽  
Emil Lenc ◽  
...  
Keyword(s):  
Galactic Latitude ◽  
High Galactic Latitude ◽  
Square Kilometre Array ◽  
Pilot Survey ◽  
The Universe

Abstract We have found a class of circular radio objects in the Evolutionary Map of the Universe Pilot Survey, using the Australian Square Kilometre Array Pathfinder telescope. The objects appear in radio images as circular edge-brightened discs, about one arcmin diameter, that are unlike other objects previously reported in the literature. We explore several possible mechanisms that might cause these objects, but none seems to be a compelling explanation.

scholarly journals Astrophysical implications of binary black holes in BL Lacertae objects

2002 ◽  
Vol 388 (2) ◽  
pp. 470-476 ◽  
Author(s):  
F. De Paolis ◽  
G. Ingrosso ◽  
A. A. Nucita
Keyword(s):  
Black Holes ◽  
Bl Lacertae Objects ◽  
Binary Black Holes ◽  
Bl Lacertae

scholarly journals Longterm optical monitoring of bright BL Lacertae objects with ATOM: Spectral variability and multiwavelength correlations

2014 ◽  
Vol 573 ◽  
pp. A69 ◽  
Author(s):  
Alicja Wierzcholska ◽  
Michał Ostrowski ◽  
Łukasz Stawarz ◽  
Stefan Wagner ◽  
Marcus Hauser
Keyword(s):  
Optical Monitoring ◽  
Spectral Variability ◽  
Bl Lacertae Objects ◽  
Bl Lacertae

scholarly journals Detection of Hα Emission on High Velocity 21 cm Clouds

1990 ◽  
Vol 139 ◽  
pp. 193-198
Author(s):  
Guido Münch ◽  
Eckhart Pitz
Keyword(s):  
High Velocity ◽  
Galactic Latitude ◽  
Emission Rates ◽  
High Galactic Latitude ◽  
Continuum Intensity ◽  
Lyman Continuum ◽  
Local Standard ◽  
Direct Measurements ◽  
Hα Emission ◽  
Local Standard Of Rest

The measurement of Hα emission on two high galactic latitude clouds known to emit 21 cm lines with local standard of rest (LSR) velocities of −50 and −85 km s−1 is reported. The Hα lines have been found nearly at the velocities of the 21 CM features and have emission rates of 0.2 Rayleigh. The diffuse Lyman continuum intensity required to produce HI ionization at the measured rate is in agreement with the direct measurements made with the ultraviolet (UV) spectrometer of the Voyager 2 spacecraft.

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