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Observations requested for b Per December 2016 eclipse

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發表於 2016-12-3 06:36:13 | 顯示全部樓層 |閱讀模式
[size=13.3333px]AAVSO Alert Notice 563

[size=13.3333px]December 2, 2016

[size=13.3333px]Observations requested for b Per December 2016 eclipse

[size=13.3333px]An AAVSO campaign on the bright star b Per has been launched at
[size=13.3333px]the request of Dr. Donald F. Collins, who writes:

[size=13.3333px]"Dr. Donald F. Collins (AAVSO member, Swannanoa, NC), Dr. Robert
[size=13.3333px]Zavala (US Naval Observatory, Flagstaff Station), Dr. Anatoly
[size=13.3333px]Miroshnichenko (University of North Carolina at Greensboro), and
[size=13.3333px]Jason Sanborn (Lowell Observatory) have requested high
[size=13.3333px]time-resolution observations of the bright star b Persei [HIP 20070,
[size=13.3333px]SAO 29531, HR 1324, HD 26961, V ~ 4.57] during the next predicted
[size=13.3333px]eclipse, or transit, of the third star across the system as it is
[size=13.3333px]predicted to transit the inner pair of the triple system **DURING
[size=13.3333px]THE WEEK CENTERED ON DECEMBER 15, 2016**. Well-sampled light curves
[size=13.3333px]can provide timing data for the orbits with much greater precision
[size=13.3333px]than astrometry or spectroscopy alone.

[size=13.3333px]"Three campaigns by the AAVSO (AAVSO Alert Notice 476, January 4,
[size=13.3333px]2013; AAVSO Alert Notice 507, January 7, 2015; and AAVSO Alert
[size=13.3333px]Notice 537, February 26, 2016) have successfully observed three
[size=13.3333px]transits between the inner A-B pairs each with the third star. The
[size=13.3333px]second transit (January 2015) was observed 704 days after the first
[size=13.3333px]observed transit. Long time-series observations of the January 2015
[size=13.3333px]transit detected multiple dips in the light curve as the third star
[size=13.3333px]alternately transited the A and B components and the inner rotating
[size=13.3333px]system. A third transit was observed successfully by AAVSO observers
[size=13.3333px]in March 2016. During March 2016 transit the third star transited on
[size=13.3333px]the opposite sides of the inner A-B pair from the first two observed
[size=13.3333px]transits. We are trying to sort out whether the third star is
[size=13.3333px]blocked by the inner A-B pair or the A-B pair blocks the light of
[size=13.3333px]the third star in each. Results of the previous campaigns may be
[size=13.3333px]seen at the links below:

[size=13.3333px]January 2013:  [size=13.3333px]http://inside.warren-wilson.edu/~dcollins/bPersei/

[size=13.3333px]January 2015:  [size=13.3333px]https://www.aavso.org/campaign-highlight-b-persei

[size=13.3333px]and [size=13.3333px]http://inside.warren-wilson.edu/~dcollins/bPersei/bPersei2015Eclipse/b_Persei2015eclipse.html

[size=13.3333px]The last link above includes an animation attempting to simulate
[size=13.3333px]the eclipse of the orbiting stars in the system.

[size=13.3333px]The plot showing the result of the March 2016 campaign may be seen
[size=13.3333px]on the AAVSO webpage for this Alert Notice
[size=13.3333px]([size=13.3333px]https://www.aavso.org/aavso-alert-notice-563[size=13.3333px]).

[size=13.3333px]"The inner pair of stars [in b Per] orbit in a low-inclination
[size=13.3333px](non-eclipsing) orbit with a 1.523 day period that shows a small
[size=13.3333px]ellipsoidal variation (0.06 V p-p) due to the gravitational
[size=13.3333px]distortion of the two stars. This is shown as the small
[size=13.3333px]out-of-eclipse eclipse oscillations in the [figure showing the
[size=13.3333px]March 2016 eclipse that may be seen on the AAVSO webpage for this
[size=13.3333px]Alert Notice]. The third star of the system transits the inner pair
[size=13.3333px]every 702 - 705 days, no eclipse had been detected before the 2013
[size=13.3333px]AAVSO campaign.  

[size=13.3333px]"Observers are asked to obtain high-resolution time-series
[size=13.3333px]observations in V during the eclipses as well as time-series
[size=13.3333px]observations of the system out of eclipse **BEGINNING ABOUT
[size=13.3333px]DECEMBER 8, 2016, [AND CONTINUING FOR ABOUT A WEEK AFTER THE
[size=13.3333px]ECLIPSE]** in order to calibrate the varying offsets from different
[size=13.3333px]observing systems. It is recommended to use the star HIP 20156 =
[size=13.3333px]SAO 39457 = HR 1330 = HD 27084 (the star labeled '55') in the AAVSO
[size=13.3333px]finder chart at 5.456 V as the comparison star. For a check star
[size=13.3333px]HIP 20370 (J2000 RA, dec = 04 19 13.24, +50 02 55.30) may be used
[size=13.3333px]if the observer's field of view is about one degree. This star is
[size=13.3333px]not in the AAVSO sequence. Any other AAVSO sequence stars may be
[size=13.3333px]used as check stars if available in the observer's field of view.

[size=13.3333px]"CCD and DSLR observers should follow some simple guidelines to
[size=13.3333px]observe bright stars. Integration times should be kept longer than
[size=13.3333px]about 15 seconds by stopping down the aperture of the optics if
[size=13.3333px]necessary. Otherwise atmospheric scintillations add significantly
[size=13.3333px]to the noise. With short focal-length telescopes or lenses - needed
[size=13.3333px]for large fields of view for bright stars and the sequences -
[size=13.3333px]de-focusing (FWHM ~ 4 pixels) is also necessary to avoid
[size=13.3333px]under-sampling among pixels on the detector array. Co-adding the
[size=13.3333px]photometry data (between 5 and 20 observations averaged) or
[size=13.3333px]stacking the same number of images will reduce the point-to-point
[size=13.3333px]noise even further. It is also important to obtain out-of-eclipse
[size=13.3333px]observations both before and after the event in order to match the
[size=13.3333px]varying zero point offsets from different observers and to match
[size=13.3333px]the out-of-eclipse light curves with the ellipsoidal light curve of
[size=13.3333px]b Persei. Observers should also concentrate on obtaining time-series
[size=13.3333px]of long duration each night - especially in mid-eclipse as the
[size=13.3333px]transit time duration between any two stars is about six hours.

[size=13.3333px]"We also need a wider longitudinal spread in observers in order to
[size=13.3333px]insure that observations cover the entire transit event that
[size=13.3333px]experiences several eclipses and re-emergences during the 2-4 day
[size=13.3333px]event. Observers from western N. America, Pacific islands, and
[size=13.3333px]Asia are especially needed in addition to continued good coverage
[size=13.3333px]from Europe and eastern North America.

[size=13.3333px]"Photoelectric observers are especially encouraged to contribute to
[size=13.3333px]the campaign.

[size=13.3333px]"Dr. Anatoly Miroshnichenko and his students at the University of
[size=13.3333px]North Carolina at Greensboro have been obtaining extensive
[size=13.3333px]high-resolution spectroscopy of the b Persei system this observing
[size=13.3333px]season to help with the campaign."

[size=13.3333px]A thread has been created on the Campaigns and Observation Reports
[size=13.3333px]forum at ([size=13.3333px]https://www.aavso.org/content/december-2016-b-per-campaign[size=13.3333px])
[size=13.3333px]to share rapid developments, observing techniques, and notices
[size=13.3333px]concerning the eclipse progress.

[size=13.3333px]Coordinates for b Per:  R.A. 04 18 14.62  Dec. +50 17 43.8  (J2000)

[size=13.3333px]Charts with a comparison star sequence for b Per may be created
[size=13.3333px]using the AAVSO Variable Star Plotter (VSP, [size=13.3333px]https://www.aavso.org/vsp[size=13.3333px]).
[size=13.3333px]Please choose comp/check stars as requested above, if possible.

[size=13.3333px]Please submit observations to the AAVSO International Database
[size=13.3333px]using the name b PER. Do NOT also send observations to Dr. Collins.

[size=13.3333px]This campaign is being followed on the AAVSO Observing Campaigns
[size=13.3333px]webpage ([size=13.3333px]https://www.aavso.org/observing-campaigns[size=13.3333px]).


[size=13.3333px]This AAVSO Alert Notice was compiled by Elizabeth O. Waagen
[size=13.3333px]primarily utilizing text provided by Dr. Donald Collins.

[size=13.3333px]----------------------------------
[size=13.3333px]SUBMIT OBSERVATIONS TO THE AAVSO

[size=13.3333px]Information on submitting observations to the AAVSO may be found at:
[size=13.3333px]https://www.aavso.org/webobs

[size=13.3333px]ALERT NOTICE ARCHIVE AND SUBSCRIPTION INFORMATION

[size=13.3333px]An Alert Notice archive is available at the following URL:
[size=13.3333px]https://www.aavso.org/alert-notice-archive

[size=13.3333px]Subscribing and Unsubscribing may be done at the following URL:
[size=13.3333px]https://www.aavso.org/observation-notification#alertnotices

[size=13.3333px]-------------------------------------------------
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