Variability of the Radio Nucleus of the Galaxy M81

Bietenholz, M. F.; Bartel, N.; Rupen, M. P.

doi:10.1017/s0252921100045206

International Astronomical Union Colloquium

1998

DOI: 10.1017/s0252921100045206

|View full text |Cite

Variability of the Radio Nucleus of the Galaxy M81

M. F. Bietenholz

N. Bartel

M. P. Rupen

Abstract: A b s t r a c t .We report on V L A and V L B I observations of t h e nucleus of t h e nearby spiral galaxy M81. T h e V L A observations show t h e flux density of t h e nucleus to be variable by 50%. T h e VLBI observations indicate t h a t t h e s t r u c t u r e of t h e nucleus of M81 is s o m e w h a t variable on timescales of weeks.

Help me understand this report

Search citation statements

Order By: Relevance

Paper Sections

Select...

Citation Types

Supporting

Mentioning

Contrasting

Year Published

1999

2000

Publication Types

Select...

Article2

Relationship

Self Cite1

Independent1

Authors

Journals

Cited by 2 publications

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

Discovery of Radio Outbursts in the Active Nucleus of M81

Dyk

Pooley³

et al. 1999

The Astronomical Journal

View full text Add to dashboard Cite

The low-luminosity active galactic nucleus of M81 has been monitored at centimeter wavelengths since early 1993 as a by-product of radio programs to study the radio emission from supernova 1993J. The extensive data sets reveal that the nucleus experienced several radio outbursts during the monitoring period. At 2 and 3.6 cm, the main outburst occurred roughly in the beginning of 1993 September and lasted for approximately 3 months ; at longer wavelengths, the maximum Ñux density decreases and the onset of the burst is delayed. These characteristics qualitatively resemble the standard model for adiabatically expanding radio sources, although certain discrepancies between the observations and the theoretical predictions suggest that the model is too simplistic. In addition to the large-amplitude, prolonged variations, we also detected milder changes in the Ñux density at 3.6 cm and possibly at 6 cm on short day) timescales. We discuss a possible association between the radio activity and an optical Ñare ([1 observed during the period that the nucleus was monitored at radio wavelengths.

show abstract

Discovery of Radio Outbursts in the Active Nucleus of M81

Dyk

Pooley³

et al. 1999

The Astronomical Journal

View full text Add to dashboard Cite

show abstract

A Stationary Core with a One‐sided Jet in the Center of M81

Bietenholz

Bartel

Rupen

2000

ApJ

Self Cite

112

View full text Add to dashboard Cite

The nucleus of the nearby spiral galaxy M81 was observed at 8.3 GHz with a global VLBI array at 20 epochs over four and a half years, with a linear resolution at the source of about 2000 AU or 0.01 pc. Phase-referenced mapping with respect to the geometric center of supernova 1993J in the same galaxy enabled us to find, with a standard error of about 600 AU, a stationary point in the source south-east of the brightness peak. We identify this point as the location of the core and the putative black hole at the gravitational center of the galaxy. The 2σ upper bound on the core's average velocity on the sky is ≤ 40 µas yr −1 or ≤ 730 km s −1 (relative to the center of SN1993J, in excess of galactic rotation). A short, one-sided jet extends towards the north-east from the core, in projection approximately in line with the rotation axis of the galaxy, and towards the well-known extended emission 1 kpc further out. The orientation of the jet varies smoothly, with timescales of about one year, and an rms of 6 • , around its mean position angle of 50 • . Occasionally the jet appears to bend to the east. The length of the jet is only about 1 mas (3,600 AU), and varies with an rms of about 20% from epoch to epoch. The inferred speeds are below 0.08c. The total flux density of the core-jet varies erratically, changing on occasion by a factor of two over a few weeks, without any significant changes in the source size and orientation. The inferred velocity of the plasma flow is > 0.25c. The results are consistent with a model in which plasma condensations with short lifetimes are ejected relativistically from the core on a timescale of less than a few weeks. The condensations travel along a tube whose pattern and geometry are also variable but only on a timescale of about one year. The central engine of M81 has qualitative similarities to those of powerful active galactic nuclei of radio galaxies and quasars, and may also represent in power and size a scaled-up version of the largely hidden nucleus in our own Galaxy.

show abstract

scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.

Contact Info

customersupport@researchsolutions.com

10624 S. Eastern Ave., Ste. A-614

Henderson, NV 89052, USA

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

Blog Terms and Conditions API Terms Privacy Policy Contact Cookie Preferences Do Not Sell or Share My Personal Information

Made with 💙 for researchers

Part of the Research Solutions Family.

Variability of the Radio Nucleus of the Galaxy M81

Cited by 2 publications

References 4 publications

Discovery of Radio Outbursts in the Active Nucleus of M81

Discovery of Radio Outbursts in the Active Nucleus of M81

A Stationary Core with a One‐sided Jet in the Center of M81

Contact Info

Product

Resources

About