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SuperWASP observations of the 2007 outburst of Comet 17P/Holmes
We present wide-field imaging of the 2007 outburst of Comet 17P/Holmesobtained serendipitously by SuperWASP-North on 17 nights over a 42-nightperiod beginning on the night (2007 October 22-23) immediately prior tothe outburst. Photometry of 17P's unresolved coma in SuperWASP datataken on the first night of the outburst is consistent with exponentialbrightening, suggesting that the rapid increase in the scatteringcross-section of the coma could be largely due to the progressivefragmentation of ejected material produced on a very short time-scale atthe time of the initial outburst, with fragmentation time-scalesdecreasing from tfrag ~ 2 × 103 to ~1× 103 s over our observing period. Analysis of theexpansion of 17P's coma reveals a velocity gradient suggesting that theouter coma was dominated by material ejected in an instantaneous,explosive manner. We find an expansion velocity at the edge of the dustcoma of vexp = 0.55 +/- 0.02 kms -1 and a likelyoutburst date of t0 = 2007 October 23.3 +/- 0.3, consistentwith our finding that the comet remained below SuperWASP's detectionlimit of mV ~ 15mag until at least 2007 October 23.3.Modelling of 17P's gas coma indicates that its outer edge, which wasobserved to extend past the outer dust coma, is best explained with asingle pulse of gas production, consistent with our conclusionsconcerning the production of the outer dust coma.
| Membership of low-mass stars in the open cluster Alpha Persei
The results of a combined astrometric, photometric, and spectroscopicsearch for low-mass members in the intermediate-age open cluster AlphaPersei are presented. Over 130 low-mass new members have been identifiedto M(v) about 12.5, almost doubling the previous number of knownmembers. The new membership information suggests a slight upwardrevision of Alpha Per's age to about 8 x 10 exp 7 yr. Alpha Per isnoticeably spatially elongated in a direction parallel to the Galacticplane, most likely due to tidal deformation. Analysis of thedistribution of relative H-alpha emission strengths among Alpha Permembers confirms the view that the mean H-alpha strength decreases inincreasingly older systems. Allowing for survey incompleteness, onecannot reject the idea that the luminosity function is consistent withthe field luminosity function to M(v) about 9 or 10.
| A spectrophotometric survey of stars along the Milky Way. IV
In the present paper a catalogue of spectrophotometric quantities,spectral types, monochromatic magnitudes and colour equivalents is givenfor all stars brighter than the magnitude m4400 = 10.5 in aregion of the Milky Way in Perseus. No absorption is found for starscloser than about r = 100 pc. The absorbing clouds are situated atdistances closer than 1 kpc and at about 2.5 kpc in the local arm andthe Perseus arm, respectively. The space between the two arms is freefrom absorption. It is also concluded that the Perseus arm continuesbeyond l = 140 deg, containing not only hydrogen gas but also dust to atleast l = 150 deg), while the content of OB stars decreases abruptly atl = 140 deg.
| The H-R diagram of the alf Per cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76..242M&db_key=AST
| Photometry of the α Persei Cluster.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1960ApJ...132...68M&db_key=AST
| Eigenbewegungen in der Umgebung von α Persei
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Observation and Astrometry data
| Constellation: | Περσεύς |
| Right ascension: | 03h38m15.41s |
| Declination: | +51°35'22.5" |
| Apparent magnitude: | 10.396 |
| Proper motion RA: | 10.1 |
| Proper motion Dec: | -8.4 |
| B-T magnitude: | 11.136 |
| V-T magnitude: | 10.458 |
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