In:
Publications of the Astronomical Society of Japan, Oxford University Press (OUP), Vol. 60, No. 5 ( 2008-10-25), p. 1001-1006
Abstract:
We present the results of monitoring observations of a 6.7GHz methanol maser in Cepheus A (Cep A) using the Yamaguchi 32m radio telescope and of imaging observations conducted with the JVN (Japanese VLBI Network). We identified five spectral features, which are grouped into two groupes: redshifted ($-$1.9 and $-$2.7kms$^{-1}$) and blueshifted ($-$3.8, $-$4.2, and $-$4.9kms$^{-1}$). We detected rapid variabilities in these maser features within a monitoring period of 81d. The redshifted features decreased in flux density to 50% of the initial value, while the blueshifted ones rapidly increased within 30d. The time variation in these maser features had two remarkable properties: synchronization and negative correlation between the redshifted and the blueshifted. Based on the JVN observations, we found that the maser spots were associated with the CepAHW2 object and had an arched structure with a scale of $\sim$1400AU; also, separations of the five maser features were found to be larger than 100AU. These properties of the masers, namely, the synchronization of the flux variation and the spectral and spatial isolations of the features, suggest that collisional excitation by a shock wave from a common exciting source is unlikely to happen. Instead, the synchronized time variation of the masers can be explained if all of the maser features are excited by infrared radiation from the dust that is heated by a common exciting source with a rapid variability.
Type of Medium:
Online Resource
ISSN:
2053-051X
,
0004-6264
DOI:
10.1093/pasj/60.5.1001
Language:
English
Publisher:
Oxford University Press (OUP)
Publication Date:
2008
detail.hit.zdb_id:
2206640-8
detail.hit.zdb_id:
2083084-1
SSG:
16,12
Permalink