Light Curve Templete/Observing Form For Visual SNe Observers.
The following charts/text are intended as tools for monitoring the Type Ia supernovae (SNe) event visually or photographically (utilizing telescope equipped CCD equipment).The files include: A replication of The Type Ia SNe, V-magnitude (with data point checks from other cited references)and color index (B-V) templete (to indicate a general color-related trend of the type Ia SNe (nutemp.gif) weaned from Bruno Leibundgut's (hereafter BL) monumental paper: "Supernova Studies VII, An Atlas of Light Curves of SNe, Type I" (1991). Observing forms for logging magnitude estimates (form, sncurv.gif) and the templete forms (avcurv.gif, snetem.gif) which are uncluttered versions of the templete are presented, and are intended for use in comparing individual or aquired observations verses the mean SN Type Ia, V magnitude light curve (BL). It is the hope of this study to, with precise standarized comparison stars, and enough interested and seasoned observing participants to form a database where the visual lightcurve behavior of various Type Ia SNe events can be logged and evaluated. An analysis of amateur magnitude estimates involving the bright supernova SN 1989B in NGC 3627 (M66) is displayed. keywords: supernova, type Ia, templete, light curve, visual, CCD observations
The charts were created using the Paintbrush tool (Windows 3.1), and converted to the .gif format using Paint Shop Pro (for easier transmission), these charts can be converted back into the .bmp format, so that data points could be plotted verses the V magnitude templete (BL). The scales of the chart are displayed, as are a projected error bar. These charts were constructed by eye comparison, after having taken a sample of BL's work, (figures 65 and 71) they were enlarged to 200% to construct a templete that agrees fairly well with the data presented and referred to in various professional papers. One word of caution: The scaling of BL's templete is ~1.5 to 1 (days to magnitude), the light curves by this author embrace a scaling of 1 to 1, this to make it easier to insert data. Thusly, the templete light curves (SHL) appear to be "flatter", especially in snetem.gif at maximum light as compared to BL's templete.
Informational data displayed in nutemp.gif, is in pretty good agreement with cited references utilizing BL's templete, the only noteworthy exceptions are the decay to 15 days, where the magnitude decline difference approaches 0.08m,(for the designated period), plus the Full Width, Full Maximum (one magnitude from maximum light estimate [Leibundgut,1993]), differs by ~1.4 days. In addition, the decline (per day) from day 6 to day 20 (Phillips, et.al 1992), differs by 0.0016m for the period cited, and the magnitude decline (per day) from day 50 to day 80 (Leibundgut, 1993) differs by 0.002m for that time period. This I attribute to replicating errors of the light curve, however in the visual mode, this should not be of too much consequence. The participant might also consider re-tracing the chart in snetemp.gif and avcurv.gif with a fine marker, to alleviate some of the "ragged edges" induced by computer representation of the templete...this if a direct method of entering magnitude estimate points is preferred. Also the magnitude scale tick marks can be adjusted to accomodate specific events.
PURPOSE OF THIS EXCERCISE
Visual magnitude estimates (by the amateur community) have, by and large, presented many problems of magnitude estimate scatter in the past due to various individual personal equations (scope, site, atmospheric extinction, position angle, age, color sensitivity, non-usage of filters [CCD], etc.), but most importantly from a lack of good photometrically sequenced magnitude comparison stars in the location of the SN event. Hopefully channels of communication with various organizations or individuals can be opened to initiate a cooperative effort to transmit information concerning acceptable standarized comparison stars used in individual events. I believe this might help alleviate some of the problems involving the making of acceptable amateur light curves. It might be noted that several papers have been published that address this issue and/or consider transformation formulae for magnitude reductions around various events (de Vaucouleurs and Corwin, 1985; de Vaucouleurs, Corwin, and Skiff, 1994, Richmond et. al, 1994 and Pierce, Jacoby, 1995).
In the absence of a more definitive method of transforming visual magnitudes to V-band magnitude values, we will for the time being, experiment and adopt (author's initiative) a value of V = visual - 0.3m (with a scatter of 0.10m) when utilizing comparison stars where V-band magnitudes are made available (preferred reference: Thompson/Bryan "Supernova Charts" (1989). These corrected values may then be entered in the appropriate column in the log sheet (form). (NOTE: No correlation between color value comparisons will be made at this time.
While SNe events might appear as point sources to the earthbound observer the following suggestion is offered by Brian Skiff (Lowell Observatory, in a message to the Novanet, 3/7/95) which might be considered involving usage of CCD-generated (with certain implications regarding "naked-eye photometry")..."It should be noted that in principle there is no way to transform data from emission-line objects like novae and supernovae to any standard photometric scale based on ordinary stars. The spectra are simply too dissimiliar to avoid systematic errors between different filter/detector combinations. The problem is most acute toward the blue, but workable with broadband filters in the red--as long as long as each system is well calibrated...."
It may be prudent to use the templete's snetemp.gif and/or avcurv.gif to register any corrections (to magnitude) AFTER the data points have been obtained and noted on form and sncurv.gif, thus eliminating a tendency for bias towards the mean light curves which might influence the intended outcome....
P.S. Completed forms of any past or future SN event are welcomed by the author and will be used (with appropriate credit) to archive and research information on the behavior of this fascinating phenomena.