NEXXUS - The database for Nearby X-ray and extreme UV emitting Stars
How to search in NEXXUS and interpret the available data
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Star data
ROSAT data
XMM-Newton data
Star data
ROSAT data
XMM-Newton data
You can search in several star catalogues. NEXXUS is based on the Catalogue of Nearby Stars (CNS) containing stars within a distance of 25 pc to the sun in its updated Version. This Version of CNS contains the older versions of this catalogue: Stars contained in CNS1 (W. Gliese: [First] Catalogue of Nearby Stars, 1957) or in CNS2 (W. Gliese: [Second] Catalogue of Nearby Stars, Edition 1969) that have Gliese (Gl) Numbers, the Supplement to the CNS2 (W. Gliese and H. Jahreiss, 1979) containing the Gliese-Jahreiss (GJ) stars and its update, the 3rd version from 1991, where the newly added stars got the designation NN and later on numbers. Every star in NEXXUS will be found either in the Gliese (Gl), Gliese-Jahreiss (GJ), Additions in 3rd Version or latest Additions section.
The Luyten Half Second Catalogue (LHS) in its second edition (W.J. Luyten, 1979) lists stars with proper motions exceeding 0.5" annually. For nearby stars typically showing high proper motion almost the whole LHS Catalogue is contained in NEXXUS. The so-called Giclas numbers indicate stars from the Lowell Proper Motion Survey (H.L. Giclas, R. Burnham Jr., N.G. Thomas, Northern Hemisphere 1971, Southern Hemisphere 1978).
The catalogue lists contain the whole sample of screened stars, those which are linked to a star page were identified as X-ray or extreme UV sources. That means stars which are not linked were checked, but refused or not detected.
For a search by coordinates just enter the coordinates of your object in the given form to see if there is a star identified with an X-ray source at the selected position. Search by coordinates will provide you a list of stars with its designations and coordinates (or a message if no star is found). For more information about the star and the identified x-ray and extreme UV source(s) the link "more" will guide you to the star page.
Search by colour index or distance will give you a list of detected stars within the chosen values. Note that the input of the full interval for B-V (-0.25 to 2.50) will not provide you the full sample of detected stars because not for every star the colour index B-V is available.
For a search by colour index or distance fill only the two interval parameters and leave the other two empty. Search by colour index and distance can also be combined, when all four parameters where filled.
A search by colour index or distance produces a star list similar to search by coordinates, but with additional star information containing colour index and distance.
The ROSAT X-Ray All-Sky Survey Image Browser provides an X-ray colour image of the region around the star's position. At Simbad you can find objects in 10 arcmin around the star's coordinates.
The Star Information
First column are different catalogue names of the star. Every star in NEXXUS is either listed in CNS1, CNS2 or its additions and therefore has a Gl, GJ or CNS number. Stars with Gl numbers without a decimal point (e.g. Gl 471) are numbered in the CNS1, stars with Gl numbers with a decimal point (e.g. Gl 471.2) are additional stars numbered in the CNS2. The CNS1 stars were ordered by right ascension (B1950!) and the new stars from CNS2 added between them. The GJ stars from the Supplement to the CNS2 are divided in two parts: Newly added nearby stars got numbers starting with 1001 and suspected nearby stars with uncertain distance data starting with 2001. Stars from the 3rd version were first not been numbered, but got the designation NN. The Centre de Données astronomiques de Strasbourg added a number starting with 3001 to these NN stars and later converted this designation into GJ. CNS numbering for the NN stars was done later (after new additions). Therefore there ist no relation between these numbers and the new GJ numbers according to Simbad! To avoid confusion I numbered these stars with the designation CNS. Stars with CNS3 numbers are contained in Woolley's Catalogue of stars within 25 pc of the sun but not in CNS1/2. Stars with CNS4 numbers are the stars from the 3rd version described above. Designations with CNS5 to CNS8 indicate later additions to the Catalogue of Nearby Stars.
If a star is numbered in the LHS or Giclas Catalogue, these numbers are mentioned in addition. In the LHS Catalogue stars with proper motions larger than 2 "/yr are numbered 1 to 100, between 1 and 2 "/yr 101 to 1000, numbers 1001 through 5000 are assigned to stars with proper motions between 0.5 and 1 "/yr. The stars with motions between 0.480 and 0.499 "/yr have been assigned numbers larger than 5000. Numbers larger than 6000 refer to stars for which at one time or another a value larger than 0.49 "/yr was published.
Right ascension and declination of the stars are according to CNS and for J2000.0. The coordinates are not very precise (for CNS is not a positon catalogue), the accuracy of RA is only given in integers of seconds and of DE in tenth of arcminutes.
Proper motion is provided as values for Mu and Theta, meaning the total proper motion in "/yr and its direction angle. Radial velocity is given in km/sec. There are some stars for which no information about these three values is available.
Next column is Spectral type or colour class together with luminosity and additions. The colour Index B-V can also be found but note that for a significant part of the sample B-V is not available. (Mostly because of missing B magnitudes for faint M-stars)
The V magnitude of any star is converted by the distance which is derived from the parallax into the absolute magnitude MV. Parallaxes are trigonometric or photometric, partly Hipparcos data.
For more information about the star enter its designation (Gl, GJ, LHS or Giclas numbers, not CNS) in Simbad or see in ARICNS where also more information about the data can be found.
The ROSAT All Sky Survey The ROSAT PSPC performed an all-sky survey during the first half year (1990/91) of the ROSAT mission. X-ray sources in the ROSAT All Sky Survey (RASS) are derived from ROSAT All-Sky Bright Source Catalogue (Voges et al. 1999) or ROSAT All-Sky Survey Faint Source Catalogue (Voges et al. 2000). A star can only have one correlated RASS source. The RASS sources are unique, its detection number is also its designation. RASS detection numbers can therefore directly be entered in Simbad. The name includes the '1RXS' acronym, and is based on the J2000.0 position (format JHHMMSS.S+DDMMSS) of the source.
The ROSAT Position Sensitive Proportional Counter
The ROSAT PSPC data were taken from the Second ROSAT Source Catalog of Pointed Observations (ROSAT Consortium, ROSAT News No. 72, 25-May-2000). PSPC data available is similar to RASS but with further information.
PSPC detection numbers are similar to RASS detection numbers but they are not unique. Detections with the same position will have the same detection name.
Therefore pointed observations can clearly be identified by a Sequence ID which contains a six-digit sequence number and a source number. The first digit of the sequence number indicates the target of the observation. (See ROSAT Observation categories for the meaning of the digits.) Most of the sequences in NEXXUS begin with 2, meaning the target was a normal star or white dwarf, indicating the identified star was anyway target of the observation. When other digits appear, the star was just coincidently in the field of view of the observation.
The off-axis angle OAX (in arcminutes) is a sign for quality of coordinates and point spread function.
The Observation Times for a sequence number were presented as year-month-day numbers.
Pointed observations also contain links to colour images from the X-ray data similar to All Sky Survey Image Browser. In these images, the sources are numbered according to the last 3 digits of the source numbers from the sequence ID.
The ROSAT Position Sensitive Proportional Counter with Filter
The data from Pointed Observations with the PSPC with boron filter were taken from the Second ROSAT Source Catalog of Pointed Observations with the Position Sensitive Proportional Counter with Filter. (The ROSAT Consortium, ROSAT NEWS No. 74)
PSPCF data are similar to PSPC data, but the conversion factor for the X-ray luminosity is 3E-11 ergs/cm^2/counts.
The ROSAT High Resolution Imager
The ROSAT HRI data were obtained from the ROSAT Source Catalog of Pointed Observations with the High Resolution Imager, 3rd Release. (The ROSAT Consortium, ROSAT NEWS No. 71).
HRI data differ only little from RASS and PSPC data: Instead of the likelihood you find the Signal-to-Noise Ratio SNR. The conversion factor for the X-ray luminosity is 2.4E-11 ergs/cm^2/counts.
The ROSAT Wide Field Camera Survey
The ROSAT Wide Field Camera (WFC) performed the all-sky survey at EUV wavelengths. The survey was conducted in two filter bands: S1 is 90-206eV (60-140 Å) mean 125eV (100 Å) and S2 which is 62-110eV (110-200 Å), mean 90eV (140 Å)
ROSAT WFC Survey sources have detection numbers similar to the X-ray sources, but with a less precise format (JHHMM+DDM) for position. Therefore, Right ascension and Declination for the source were given additionally. WFC Survey sources are unique like RASS sources.
The Count Rate is splitted into S1 and S2 and given in counts/sec. Instead of likelihood or Signal-to-Noise Ratio there is the significance, given for both filter bands and combined by sqrt(sigS1^2 + sigS2^2).
The ROSAT Wide Field Camera Pointed Observations
Pointed Observations with the WFC were taken parallel to the X-ray observations, so they also have the sequence numbers in the Sequence IDs. Sources from WFC pointed observations have no detection number like the X-ray sources and the WFC Survey sources, only an integer as a source number. J2000 coordinates for the sources were therefore given too.
Pointed observations were taken in one filter band only, so there is only one Count Rate and the Filter mentionend.
Instead of the observation interval in year, month and day, the beginning of the observation is given as modified Julian Date.
For more information about ROSAT see also ROSAT Home Page at MPE.
