I am currently revamping both these pages and this "project". This will continue as time permits. - Frank
I can often be found most evenings in the
AAVSO chat room. If you want to chat about this project or and other facets of variable stars please stop by any evening. http://www.aavso.org/chat
I started this project for the learning experience and to delve deeper into the aspects of the "humps" on light curves of various LPVs I noticed while observing. At this point this is not a "scientific" project but a project to create a list or "catalog" and gather more information on LPVs that show this particular type of behavior to see if there is a reason to start a scientific "project" to discover more about this type of behavior. I hope to collect data that might be helpful to a researcher.
These "humps" or "bumps" seem to mostly appear on the rising portion of LPV's light curve as seen in the light curve of the 900 day light curve of RU HER above. A "hump" is a spot on the light curve where the slope of the curve is altered to make it look like the brightening (or dimming) of the LPV "stalls" for a period of time. (sometimes this is called "stalling" or a "shoulder")
Sometimes the brightness (or dimness) reverses direction giving the impression of an early maxima or even a double maxima for that cycle. This may or may not be related to the "double" or "dual" maxima behavior of some "LPV" stars.
At this time I am focusing my energies on my favorite target S ORI and any of the "hump" LPVs that can give me data for it's full cycle such as T CAS, W CAS, S CAS, T CAM, R AUR, V CAM, R LYN, T UMI, WZ DRA, ST CYG, T CEP, S CEP and CT LAQ.
I would argue that perhaps the most interesting parts of the light curve for these stars are at the maxima at the beginning of the LC (light curve) cycle, the part of the LC leading into the start of the "hump" event, the time of the "hump" event itself, and the LC as the "hump" event ends. At these times I would think one observation a day is the proper cadence of observations to be able to gather the most useful information.
In N. D. Melikian's paper, "Classification of the Light Curves of Mira Variables" (Astrophysics, Vol. 42, No. 4, 1999), Melikian puts forth arguments to classify the light curves of Mira variables based on the "shape" of their light curves. Mira stars that have a purely sinusoidal shapes would be "simple" light curves. Mira stars that have very complicated light curves, often with "hump" on the ascending (or decending) light curve including potential dual maxima curve would be classified as having 'complicated light curves'.
After studying the light curves for 223 Mira stars he found the following:
He felt there was a real difference in the light curves based on the shape of their light curves.
Some astronomers have said that all MIRAs have "humps" at one time or the other but I haven't seen this yet in the light curves I've looked at.
A paper published in Astrophysics, Vol. 50, No. 1, 2007, titled "VARIABILITY OF LONG-PERIOD PULSATING STARS. III. CHANGES IN THE PARAMETERS OF HUMPS AT THE ASCENDING BRANCH" by V. I. Marsakova and I. L. Andronov, may have answered a lot of the questions I have concerning the "humps". The paper can be found at.
There are two more papers in this series that talks about the methods used to produce the data in the above paper:
Variability of long-period pulsating stars. I. Methods for analyzing observations - http://www.springerlink.com/content/n611125846588r70/
Variability of long-period pulsating stars. II. Additional parameters for classifying stars - http://www.springerlink.com/content/y03752753h358375/
List of 57 LPVs that show distinct "humps" and/or double maximas since 2000. Please click on the star name to see a light curve for that star and possible other data.
Below is a table of LPV hump stars candidates.
Those with event predictions are listed first in order of date. The rest are listed in order of RA.
Some of these stars may not be hump stars, particularly those flagged in red, and probably those flagged in yellow
- Accurately measure the time from the Maxima at the beginning of the cycle to the Maxima at the end of the cycle for each LPV that shows hump event. Accurately measure each period for that LPVs for all cycles (get the period of the cycle). If a particular cycle does not have a "hump" in it compare it's period to the period of a cycle with a "hump" event to see if this affects the cycle period.
- Measure the time from the Maxima at the beginning of the cycle to the beginning of "hump" event to understand how far into each cycle the "hump" event starts and the relationship of the start of the event from the beginning Maxima to the length of the overall cycle. Compare this value between cycles for the same LPV
- Measure the time from the beginning of the hump to the end of the hump. Compare how the length of the "hump" event changes between cycles.
- Calculate the length of the "hump" event compared to the length of the period of the cycle the hump occurs in to see if there is a relationship.
- Calculate the length of the "hump" events between cycles to see if there is a period to the "length".
- Calculate the length of time from the beginning or one "hump" event to the beginning of the next "hump" event to see if there any hidden periods in the "hump" events.
- Any other suggestions?
Good article on Humps and Bumps: http://www.aavso.org/vstar/templeton.pdf
M.R Templeton, J.A. Mattei and L.A. Willson,
"Secular Evolution in MIRA Variable Pulsations", The Astronomical
Journal, 130:776-778, 2005 August
Note 1 - "Fast Variations of the Mean Brightness and Other Light Curve Parameters of the Carbon Mira-Type Star S CEP", JAAVSO Volume 27, Number 2, 1999, Pages 141-145, Vladislova I. Marsakova. He describes in detail the "hump" on the ascending curve that this star showed for about a half of it's studied cycles. He also reports two cycles in a rows between JD 2428250 and 242950 where the light curve becomes unstable with an almost Double Maxima look on the second cycle. Currently, the last cycle of S Cep showed this same type of unstable behavior. (about JD 2454423 to 2454894) Perhaps the next cycle of will continue this behavior. At the time of writing (Feb 7 2010) it appears the S CEP is around minima so this could be a good star to observe over the next couple of months.
Note 2 - JAAVSO Volume 25, Number 2, 1997, page 58
Note 3 - N.D. Melikian, Astrophysics, Vol. 42, No. 4, 1999, pages 408-418 - Melikian did a study of 223 Miras with light curve information from the HIPPARCOS space telescope. No list of the stars studied is supplied.
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