36 research outputs found
The faint outskirts of the blue compact galaxy Haro 11: is there a red excess?
Previous studies of the low surface brightness host of the blue compact
galaxy (BCG) Haro 11 have suggested an abnormally red color of V-K=4.2+-0.8 for
the host galaxy. This color is inconsistent with any normal stellar population
over a wide range of stellar metallicities (Z=0.001-0.02). Similar though less
extreme host colors have been measured for other BCGs and may be reconciled
with population synthesis models, provided that the stellar metallicity of the
host is higher than that of the ionized gas in the central starburst. We
present the deepest V and K band observations to date of Haro 11 and derive a
new V-K color for the host galaxy. Our new data suggest a far less extreme
colour of V-K=2.3+-0.2, which is perfectly consistent with the expectations for
an old host galaxy with the same metallicty as that derived from nebular
emission lines in the star-forming center.Comment: This paper contains 8 figures and 2 table
Promise of persistent multi-messenger astronomy with the Blazar OJ 287
Successful observations of the seven predicted bremsstrahlung flares from the unique bright blazar OJ 287 firmly point to the presence of a nanohertz gravitational wave (GW) emitting supermassive black hole (SMBH) binary central engine. We present arguments for the continued monitoring of the source in several electromagnetic windows to firmly establish various details of the SMBH binary central engine description for OJ 287. In this article, we explore what more can be known about this system, particularly with regard to accretion and outflows from its two accretion disks. We mainly concentrate on the expected impact of the secondary black hole on the disk of the primary on 3 December 2021 and the resulting electromagnetic signals in the following years. We also predict the times of exceptional fades, and outline their usefulness in the study of the host galaxy. A spectral survey has been carried out, and spectral lines from the secondary were searched for but were not found. The jet of the secondary has been studied and proposals to discover it in future VLBI observations are mentioned. In conclusion, the binary black hole model explains a large number of observations of different kinds in OJ 287. Carefully timed future observations will be able to provide further details of its central engine. Such multi-wavelength and multidisciplinary efforts will be required to pursue multi-messenger nanohertz GW astronomy with OJ 287 in the coming decades
Promise of Persistent Multi-Messenger Astronomy with the Blazar OJ 287
Successful observations of the seven predicted bremsstrahlung flares from the unique bright blazar OJ 287 firmly point to the presence of a nanohertz gravitational wave (GW) emitting supermassive black hole (SMBH) binary central engine. We present arguments for the continued monitoring of the source in several electromagnetic windows to firmly establish various details of the SMBH binary central engine description for OJ 287. In this article, we explore what more can be known about this system, particularly with regard to accretion and outflows from its two accretion disks. We mainly concentrate on the expected impact of the secondary black hole on the disk of the primary on 3 December 2021 and the resulting electromagnetic signals in the following years. We also predict the times of exceptional fades, and outline their usefulness in the study of the host galaxy. A spectral survey has been carried out, and spectral lines from the secondary were searched for but were not found. The jet of the secondary has been studied and proposals to discover it in future VLBI observations are mentioned. In conclusion, the binary black hole model explains a large number of observations of different kinds in OJ 287. Carefully timed future observations will be able to provide further details of its central engine. Such multi-wavelength and multidisciplinary efforts will be required to pursue multi-messenger nanohertz GW astronomy with OJ 287 in the coming decades
Spectral Type and Geometric Albedo of (98943) 2001 CC21, the Hayabusa2# Mission Target
We conducted optical polarimetry and near-infrared spectroscopy of JAXA's
Hayabusa2# mission target, (98943) 2001 CC21, in early 2023. Our new
observations indicated that this asteroid has a polarimetric inversion angle of
~21 deg, absorption bands around 0.9 and 1.9 um, and a geometric albedo of
0.285 +- 0.083. All these features are consistent with those of S-type but
inconsistent with L-type. Based on this evidence, we conclude that JAXA's
Hayabusa2# spacecraft will explore an S-type asteroid with albedo and size
(0.42-0.56 km when we assume the absolute magnitude of 18.6) similar to (25143)
Itokawa.Comment: 5 pages, 3 figures, Submitted to MNRAS Letter on 2023 April