LPV Humps


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

  • SFRA Frank Schorr - fschorr at comcast dot net
  • Special thanks to MDW Walter MacDonald
  • Special thanks to Neil Butterworth

Introduction:

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.

Classification attempt

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:

  • The period-spectrum correlation for the "complicated Mira" stars is weak or non-existant.
  • The period distribution of stars with the 'complex' light curves the maximum in the period distribution was 350-400 days while just 250-300 days for the Miras with 'simple' light curves.
  • Absolute bolometric magnitudes tended to be higher in the Miras with 'complex' light curves
  • According to Melikian, polarimetric observations of a group of Mira variables that contained both 'simple' and 'complex' light curves, 50% of the 'complex' light curve stars found polarization which was over twice as much of the Miras with 'simple' light curves.

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.

Measurement attempt

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.


http://www.springerlink.com/content/q82910824434n110/.  Thanks to James Bedient for this information.

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/

I may use a subset of the measurements mentioned in these three papers.


My project

Discovery/Identification:
  • I sampled the light curves for about 450 LPVs using data for the last 10 years from the AAVSO International database and the ASAS1, ASAS2 and ASAS3 databases
  • 57 LPVs that appears to have "hump" events - please see Table 1 below
  • 30 or so possible candidates - Please see Table 2
  • Developing ways to measure the relationship of these events to the light curve of the star.

Table 1:

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. 


  RA (J2000.0)  DEC (J2000.0)  Star
 Event type  Cycle Period
 Spectrum  N d (4)
 Type Source
 Next Event (JD)
 Next Event Calendar
 Comments
 00 23 13.27  +55 47 33.2  T-CAS  Dual Maxima?      2.61    T. Lange  
Study Star
 00 54 53.85  +58 33 49.2  W-CAS  Hump on RLC  405.50  C7,1e  .47    SFRA      
Study Star
 01 19 41.97  +72 36 40.7   S-CAS  Hump on RLC  612.4  S3,4e-S5,8e  .59    SFRA      Study Star
 02 29 15.31  -26 05 55.7   R-FOR  Hump on RLC  388.7  C4,3e(Ne)  1.21    SFRA      
 04 33 32.83  -63 01 45.0  R-RET  Hump on RLC  278.6  M4e-M7.5e  .57    SFRA  
   
 04 40 08.87  +66 08 48.6  T-CAM  Hump and DM?  373.2  S4,7e-S8.5,8e  .61          Study Star
 04 40 30.09  -38 14 06.9  R-CAE  Hump on RLC  391  M6e  1.11    SFRA      
 05 17 17.69
 +53 35 10.1
 R-AUR
 Hump on RLC  458  M6.5e-M9.5e  1.71          Study Star
 05 29 00.90  -04 41 32.8   S-ORI  Hump on RLC  @420  M6.5e-M9.5e  3.81m  D  SFRA

 Study Star
 05 41 56.59   +38 55 55.8  SZ-AUR  Hump on RLC  457.5  M6.5e-M9.5e  1.08  D        
 05 52 36.80  +15 58 14.4  RU-TAU  Hump on RLC  544.6  M3.5e-M6.5  3.52  D?  SFRA      Study Star
 05 55 49.17  +20 10 30.7  U-ORI  Hump on RLC  368.3  M6e-M9e  .33    SFRA      
 06 02 32.28  +74 30 27.2  V-CAM  Hump on RLC    M7e  .28    SFRA      Study Star
 06 17 53.0  -00 20 33.5  S-SEX  Moving Hump?  264.9  M2e-M5e  2.85    SFRA      
 06 26 42.88   +47 14 23.6  GQ-AUR
 Hump on RLC  304.8   M3  .87  S   MDW      
 07 01 18.01  +55 19 49.8  R-LYN  Hump on RLC  378.8  S2.5,5e-S6,8e  3.53    SFRA     Study Star
 07 05 36.20  -73 00 52.0  R-VOL  Hump on RLC  453.6   C(N)e  .54    SFRA      
 07 29 45.58  -73 22 44.0  S-VOL  Hump on RLC  394.8  M4e  1.09    SFRA      
 07 41 20
 +08 22 49
 u-cmi
 Hump on RLC
 413.9 M4e   MDW   
 09 44 58.97  -24 01 15.7  RR-HYA  Hump on RLC  343.5  M3.0e-M8e  .65    SFRA      
 09 52 54.28   -54 10 47.9  Z-VEL  Hump on RLC  411.4  M9e  .17    SFRA      
 10 24 25
 -60 11 29
 CK-CAR
 Dual Maxima
 266 M3.5lab      
 10 51 19
 -28 3 41
 RS-HYA
 Hump on RLC
 338.6 M6e 2.86     
 10 52 05.5
 -62 28 59.6
 BX-CAR
 Dual Maxima
 427 M7e     
 12 16 16.79  -56 17 09.6  BH-CRU  Hump on RLC  530  SC4.5/8-e- SC7/8-e  6.09    BIW      "Dual-Maxima Mira project" star
 13 29 42.78  -23 16 52.8  R-HYA  Hump on RLC   388.9  M6e-M9eS (Tc)  8.01    SFRA     "Dual-Maxima Mira project" star
 13 34 41.05  +73 25 52.9  T-UMI  Hump on RLC  301  M4e-M6e  23.90    G. Foster     Study Star
14 16 34.32  -59 54 49.3  R-CEN  Moving Hump?  546.2  M4e-M8iie  8.63    SFRA      "Dual-Maxima Mira project" star
15 21 39.53
 +14 18 53.1  S-SER  Hump on RLC  371.8  M5e-M6e  1.59    SFRA      
 00 15 22.27  -32 02 43.0  S-SCL  Hump on RLC  362.5  M3e-M93(Tc)  2.27    SFRA      
 15 35 57.35  -49 30 28.7  R-NOR  Double Maxima  507.5  M3e-M6ii  2.89    M. Templeton      "Dual-Maxima Mira project" star
 16 10 14.52  +25 04 14.4  RU-HER  Hump on RLC   484.3  M6e-M9  .89  D  SFRA      Study Star
 16 51 53.92  +14 56 30.7  S-HER  Hump on RLC  307.3  M4,Se-M7.5,Se  .75    R. Huziak    
 16 59 49.73  +52 19 04.4  WZ-DRA  Hump on RLC  401.7  M6e           Study Star
 17 42 25.21  -43 45 01.3  RU-SCO  Hump on RLC  370.8  M4/6e-M7ii-iiie  3.70    SFRA  
   
 17 54 10.57  -34 20 27.3  BN-SCO  Hump on RLC  616  ?            "Dual-Maxima Mira project" star
 18 28 48.74  +06 17 53.0  T-SER  Hump on RLC  338.1  M7e  .19    SFRA      
 18 44 52.11  +34 40 33.4  RY-LYR  Hump on RLC    325.8  .15    SFRA      
 19 13 54.60  -18 51 42.1  RX-SGR  Hump on RLC  335.2  M5e  .87    SFRA      
 19 19 52.46  -31 42 53.9  SW-SGR  Hump on RLC   289.9  M5e-M8  1.19    SFRA      
 19 50 33.92  +32 54 50.6  CHI-CYG  Hump on RLC  408  S6,2e-S10,4e(MSe)  .63    R. Huziak    
 20 05 29.85  +57 59 09.1  S-CYG    322.9  S2.5.1e (M3.5-M7e)  1.39    R. Huziak     No event for a number of cycles
 20 14 45.12  -46 58 55.0  R-TEL  Hump on RLC  467  M5iie-M7e      SFRA      
 20 15 33.52  +31 04 20.1  SX CYG  Hump on RLC  411  M7e  .08    SFRA      
  20 32 33.48  +54 57 00.5  ST-CYG  Hump on RLC  337.3  M5.5e-M8.0e  .23     R. Huziak      Study Star
  21 09 31.78  +68 29 27.2  T-CEP  Hump on RLC  388.1  M5.5e-M8.8e 1.47 m          Study Star
 21 35 12.83  +78 37 28.2  S-CEP  Moving Hump?  486.8  C7,4e(N8e)  1.01    Marsakova      Study Star
 22 07 29.82 +37 44 07.1 W-LAC Hump on RLC 328.5 M7e-M8e3.28 S SFRA   
 22 08 54.31  +12 32 24.5  T-PEG  Hump on RLC  379.4  M6e-M8e  1.73    SFRA      
 22 12 16.18  +14 33 12.2  RS-PEG
 Hump on RLC  415.4  M6e-M9e  3.40    SFRA      
 22 23 12.87  -22 03 23.8  RT-AQR  Moving Hump?
 252.2  M5e-M6e  .39    SFRA      
 22 25 40.93  -37 34 09.2  T-GRU  DM?  136.5  M1iae-M2ibe  .53    SFRA      
 22 57 06.49   -20 20 35.5  S-AQR  Hump on RLC  279.3  M4e-M6e  1.47    SFRA      
 23 06 39.17  +10 32 36.1  R-PEG  Hump on RLC  378.1  M6e-M9e  .91    SFRA    
 23 19 50.50  +26 16 43.6  W-PEG  Hump on RLC  345.5  M6e-M8e  .54    SFRA  2455760
 
 23 20 32.62  +08 55 08.2  S-PEG  Hump on RLC  319.2  M5e-M8.5e  .70    SFRA      
 23 56 27.56  -49 47 12.6  R-PHE  Hump on RLC  269.3  M2(ii)e- M4(iii)e  .99    SFRA      
                       
                       

Table 2

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

 COORDS    STAR  Type  N d (4)
 Next Event
 Curve  Source  Status
 0051+34    RR AND   Asc  .34    RR-AND  MDW  
 0540+37     RU AUR  Asc  1.21
 RU-AUR  MDW  *
 0732-20    Z PUP   1.22
   Z-PUP    * Small hump at JD 2454818
 0942+11    R LEO    2.20      SFRA
 1319-60    TT CEN  Asc      TT-CEN    "Dual-Maxima Mira project" star
 1513+36    RT BOO    1.16        JAAVSO V33 page 52
 1625+18    U HER  Asc  .04    U-HER  SFRA  Showing promise
 1845+43    RW LYR  Desc  .81    RW-LYR  SFRA  * -
 1910+67    U DRA  Asc  2.46
 U-DRA    
 2013+38    RS CYG
 Dbl Max?
 
 RS-CYG  SFRA  SRA
  2049+31    AM CYG  Asc  
 AM-CYG    
 2105+29    TW CYG  Asc  2.37
 TW-CYG  SFRA  *
 2122+21    SW PEG
 Asc.  
 SW-PEG    
 2111+13    AN PEG
 Asc.  3.02
 AN-PEG    
     U UMI
 Asc  2.21        
  19 13 20.82  +32 03 17.7  EL LYR
 Asc  2.81      
     WZ GEM
 Asc  2.83        
                 
    PQ CEP
       
Michael Poxon  possible
   CT LAC
    Templeton et al
 Dual Maxima Study Star
     R AQR
 Dbl Max           "Dual-Maxima Mira project" star
 0932-62    R CAR
   17.02    
 
 1003-46    V415 VEL
           SRA - "Dual-Maxima Mira project" star
 1053-61    CL CAR
 Unstable      CL-CAR    SRC - Unstable light curve -  "Dual-Maxima Mira project" star
     UZ CIR
 Dbl Max           "Dual-Maxima Mira project" star
     FK PUP
 Dbl Max           SR - "Dual-Maxima Mira project" star
 1305-26    KN HYA
 Asc & Desc
     kn-hya   SR -  Ascending & descending
 1606-21    Z SCO
 Desc?  .00    Z-SCO    


Classification/Description:

Some ideas:
 
- 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?


References and articles

Good article on Humps and Bumps: http://www.aavso.org/vstar/templeton.pdf


Mattei, Mayall and Waagen, "Maxima and Minima of Long Period Stars, 1949-1975", AAVSO


M.R Templeton, J.A. Mattei and L.A. Willson, "Secular Evolution in MIRA Variable Pulsations", The Astronomical Journal, 130:776-778, 2005 August

Footnotes

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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Mike Simonsen,
Feb 23, 2010, 8:55 PM
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