Period Change of the Eclipsing Binary V442 Cas

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• Period Change of the Eclipsing Binary V442 Cas
• By Gary Billings

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Revised Abstract

• I have determined new times of minimum for the
  Algol-type eclipsing binary V442 Cas, using CCD
  and archival (plate) observations. When combined
  with published data (including other very recent
  observations), the 70 year O-C curve shows a
  period change in the 1960s.

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Browsing old STs...

• Interesting star very deep, and total(!),
  primary eclipse
• not an intensely studied star
• period 3.592 days
• at max V12.75, Mpg13.2
• at min V16.3, Mpg17
• Primary is A0 V, secondary gt M5V (Halbadel, 1984)

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Step 1 recover the ephemeris
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Best night
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Step 2 Determine ToM
A Tracing paper method. Adjust base ToM and
period, and overplot all time series and their
reverses, mirrored about the trial ToMs.

• My ToM 2453352.888(2)
• This fits with a later published CCD obsn from
  one month earlier, within my error.

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Phased Primary Minimum
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In search of more data -- Harvard Plate
Collection
Photos David Turner
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Step 3 -- Can it be seen on the plates?

• V442 Cas is normally at mpg13.2. Fainter than
  mpg16 at minimum
• not visible on AC series plates
• RH series plates have depths from less than
  mpg12.6 to deeper than 16. Typically 14 or
  deeper.
• Comp stars of mpg 12.6 and 13.8 (USNO A2.0) used
• Finally, on the 47th RH plate I examined, from
  25/26 July 1932, the comps were visible but V442
  Cas was not! (But Id had many chances to
  observe my favourite open cluster, NGC 7789...)
• Examined 229 plates. Found the target at normal
  brightness on 198 plates, faint 12 times, and
  possibly faint 4 times on poor plates. On the
  remaining 15 plates, my comps were not visible.
• The key data was from only 3 nights...

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Phased plate observations
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3 key nights

• Single fainter thans per night are not useful,
  as the ToM uncertainty is approx ? 0.04 periods
  ? 0.14 days.
• On one night, the target was invisible on two
  plates sufficiently far apart that the range of
  possible ToMs was not too large
• On two nights, multiple plates caught the edge of
  the eclipse, so the ToM could be inferred with
  useful accuracy

Kurochkin 1982
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An early result -- continuous period decrease
1960
1945
1936
GWB plate obsns
GWB plate obsns
IBVS 5595, and GWB
IBVS 5595, and GWB
2004
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Other data
Kreiner, 2004
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A beautiful theory destroyed by more data
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A beautiful theory destroyed by more data
3.592244
3.592205
3.592108
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Is the period presently constant? Does it
increase?
This point is 0.03 days off the new fit, but this
is a CCD ToM with stated uncertainty of 0.0000
(IBVS 5595)
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Is the period presently constant?
A possible solution another recent period
decrease
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Does this star sometimes undergo period increase?
Another possibility period increases and
decreases. Hall (1989), Zavala et al. (2002),
discuss this -- however, there is very little
data about Algols with such late secondaries.
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Conclusions

• Ephemerides for observation planning 2453309.781
  6 3.592108 E 2453309.7816 3.592055 E
• V442 Cas underwent a dramatic period change in
  the 1960s.
• The period since has been generally constant, but
  small variations cannot be ruled out, including
  another recent period change since 2451028.
• Continued monitoring is encouraged -- especially
  with ToM accuracies of better than 0.01 days.

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References

• Brno, 1995, Contributions of the Public
  Observatory and Planetarium in Brno, Volume
  311-42
• Caton, D.B., and Smith, A.B., 2005, IBVS 5595.
• Halbedel, E.M., 1984, PASP 9698-104.
• Hall, D.S., 1989, Space Science Reviews 50
  219-233.
• Hoffmeister, Von C., 1966, AN 289, 139.
• Kreiner, J.M., 2004. Acta Astronomica
  54207-210.
• Kurochkin, N.E., 1982, Perem. Zvezdy Supplement
  4, N20, 166. (In Russian.)
• Meinunger, L., 1968, IBVS 269.
• Prokofjeva, V.V., and Epishev, V.P., 1969, IBVS
  376.
• Zavala, Robert T., et al., 2002, AJ 123450-457.

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Acknowledgments

• David B. Williams, for introducing me to the
  Harvard plate collection, and helping me find
  much of the published data.
• Alison Doane, Curator of the Harvard College
  Observatory Photographic Plate Collection, for
  access to the stacks.
• Dr. Jerzy Kreiner, Cracow Pedagogical University,
  for kindly sending me his data collection on this
  star.

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Additional materials - 1

• GCVS record
• NNo GCVS 1950.0 2000.0 Type Max Min Epoch Year
  Period M-m Spectrum References Other design.
• 180442 V0442 Cas 233749.4534056
  234014.8535734 EA/SD 13.2 17.0 p
  43079.465 3.592205 11 07255 05310
• 180442 V0442 Cas 234014.81 535734.0 0.001
  0.0082000.0 Tyc2
• S 09484 V0442 Cas
• REFERENCE to a chart or photograph
• 05310 L.Meinunger, MVS 5, H.1, 6, 1968.
• REFERENCE to a study of the star
• 07255 N.E.Kurochkin, Perem. Zvezdy Supplement 4,
  N20, 166, 1982.
• REMARK
• d 0.025P. P var? Since 1972 P 3.592120d.

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Additional materials - 2
Hall (1989)
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Additional materials - 3

• At primary eclipse, the cooler/larger star (M5V)
  is in front, and the eclipse is total.
• The secondary eclipse must be annular, with the
  small hot star (A0V) traversing the big cool one.