Science Archives Publication System

Quasi-periodic Oscillation in Seyfert Galaxies: Significance Levels. The Case of Markarian 766

DOI: 10.1086/338252 Bibcode: 2001ApJ...562L.121B

Yaqoob, Tahir; Staubert, Rüdiger; Wilms, Jörn +2 more

We discuss methods to compute significance levels for the existence of quasi-periodic oscillations (QPOs) in active galactic nuclei (AGNs) that take the red-noise character of the X-ray light curves of these objects into account. Applying epoch folding and periodogram analysis to the XMM-Newton observation of the Seyfert galaxy Mrk 766, a possible…

2001 • The Astrophysical Journal

XMM-Newton 52

Chromospheric Heating in the Late Phase of Two-Ribbon Flares

DOI: 10.1086/320553 Bibcode: 2001ApJ...552..849C

De Pontieu, B.; Czaykowska, A.; Alexander, D.

Fast upflows observed in the late gradual phase of an M6.8 two-ribbon flare by the Solar and Heliospheric Observatory/Coronal Diagnostic Spectrometer have provided evidence for the presence of chromospheric evaporation more than an hour after the impulsive phase of the flare. The chromospheric heating necessary to generate these upflows requires t…

2001 • The Astrophysical Journal

SOHO 52

Imaging and Photometry of Comet C/1999 S4 (LINEAR) Before Perihelion and After Breakup

DOI: 10.1126/science.1058886 Bibcode: 2001Sci...292.1348F

Woodney, Laura M.; Schleicher, David G.; Farnham, Tony L. +3 more

We analyzed photometric measurements and images of comet C/LINEAR before perihelion and after its breakup. Results from our photometry data include a lower limit of 0.44 kilometer for the radius of the nucleus before breakup, and a determination that it was depleted in carbon-chain molecules relative to most other comets. Our imaging and modeling …

2001 • Science

eHST 52

The host galaxy and optical light curve of the gamma-ray burst GRB 980703

DOI: 10.1051/0004-6361:20010311 Bibcode: 2001A&A...371...52H

Tanvir, N.; Pedersen, H.; Fynbo, J. P. U. +10 more

We present deep HST/STIS and ground-based photometry of the host galaxy of the gamma-ray burst GRB 980703 taken 17, 551, 710, and 716 days after the burst. We find that the host is a blue, slightly over-luminous galaxy with V_gal = 23.00 +/- 0.10, (V-R)_gal = 0.43 +/- 0.13, and a centre that is ~0.2 mag bluer…

2001 • Astronomy and Astrophysics

eHST 52

Ultraluminous Infrared Galaxies: Mergers of Sub-L* Galaxies?

DOI: 10.1086/323945 Bibcode: 2001ApJ...563..546C

Lucas, Ray A.; Colina, Luis; Bushouse, Howard +6 more

A sample of 27 low-redshift, mostly cool, ultraluminous infrared galaxies (ULIRGs) has been imaged at 1.6 µm with the Hubble Space Telescope (HST) Near-Infrared Camera and Multi-Object Spectrometer (NICMOS). The majority (67%) of the sample's galaxies are multiple-nucleus galaxies with projected separations of up to 17 kpc, and the rest of t…

2001 • The Astrophysical Journal

eHST 52

Star clusters in M 33. IV. A new survey from deep HST images

DOI: 10.1051/0004-6361:20000263 Bibcode: 2001A&A...366..498C

Ford, H. C.; Bianchi, L.; Chandar, R.

We have detected 102 star clusters in M 33, from 35 deep Hubble Space Telescope (HST) WFPC2 fields taken from our program and from the HST archive. Twenty-eight fields have V and I band imaging, and an additional seven fields are imaged in a single V filter. Eighty-two of the clusters were previously unknown. Integrated photometry reveals that 25 …

2001 • Astronomy and Astrophysics

eHST 52

Hubble Space Telescope Observations of Dust and Star-forming Regions in the Ocular Galaxy IC 2163 and Its Spiral Companion NGC 2207

DOI: 10.1086/318036 Bibcode: 2001AJ....121..182E

Brinks, Elias; Struck, Curtis; Elmegreen, Bruce G. +4 more

Hubble Space Telescope observations in U, B, V, and I passbands of the interacting spiral galaxies IC 2163 and NGC 2207 are used to measure extinctions in the cloud and intercloud regions and ages and luminosities of the star-forming regions. The extinction in the part of NGC 2207 seen in projection against IC 2163 was determined by using the meth…

2001 • The Astronomical Journal

eHST 52

ISOCAM Imaging of Comets 103P/Hartley 2 and 2P/Encke

DOI: 10.1006/icar.2000.6546 Bibcode: 2001Icar..149..339E

Fulle, M.; Brucato, J. R.; Mennella, V. +7 more

We present the results of ISOCAM observations performed on Comets 2P/Encke and 103P/Hartley 2, on 31 October 1997 and 1 January 1998, respectively. Images were obtained in the broadband filters LW3 (centered at 15.00 µm) and LW10 (centered at 11.50 µm). Tail models have been applied to the images to analyze the evolution of the dust co…

2001 • Icarus

ISO 52

NGC 6543: The Rings Around the Cat's Eye

DOI: 10.1086/318052 Bibcode: 2001AJ....121..354B

Balick, Bruce; Hajian, Arsen R.; Wilson, Jeanine

Hubble archival images of NGC 6543 reveal a series of at least nine regularly spaced concentric circular rings that surround the famous nebular core, known as the Cat's Eye Nebula. The rings are almost certainly spherical bubbles of periodic isotropic nuclear mass pulsations that preceded the formation of the core. The bubbles are detected solely …

2001 • The Astronomical Journal

eHST 52

The Stellar Content of the Super-Star Clusters in NGC 1569

DOI: 10.1086/321152 Bibcode: 2001AJ....122..815O

Aloisi, Alessandra; Leitherer, Claus; Origlia, Livia +2 more

We discuss HST Faint Object Spectrograph (FOS) ultraviolet spectroscopy and Near-Infrared Camera and Multiobject Spectrometer (NICMOS) photometry of four young super-star clusters in the central region of the irregular starburst galaxy NGC 1569. The new observations, coupled with previous HST WFPC2 photometry and ground-based optical spectroscopy,…

2001 • The Astronomical Journal

eHST 51