chrismlt

Campagne d'observation de b Per, étoile triple à éclipses

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Bonjour tous,

 

 

APPEL AUX OBSERVATEURS

 

La campagne d'observation de l'étoile b Per a débuté en 2013 et se poursuit au rythme de deux éclipses tous les 700 jours environ, séparées par quelques mois, l'une dite éclipse principale et l'autre secondaire.

Il s'agit d'un système triple non optique, que l'on essaye de caractériser. Donald Collins est le scientifique référent, en liaison avec l'AAVSO.

 

Nous avons pu observer une éclipse principale fin décembre 2021, et cette fois, il s'agit de se consacrer à l'observation de l'éclipse secondaire. Profondeur environ 0,5 mag, durée trois jours, sur fond de variation ellipsoidales mineures. (https://fr.wikipedia.org/wiki/Étoile_variable_ellipsoïdale )

 

 

"The observation window should last at least 2 weeks beginning about September 19, 2022, which is about 10 days before the predicted date of mid-eclipse (UT September 29.41, 2022 ± 0.1 d ). It is important that observers observe several long time-series observations both before the eclipse and after the eclipse as well as all parts of the eclipse."  (Extrait de l'alert AAVSO 791)

 

La période d'observation débute donc DES A PRESENT, car il faut ancrer chaque courbe photométrique  avant l'éclipse.

 

L'étoile est très brillante, et il est assez facile de faire de bonnes images. Je peux donner un coup de main pour le débutant. Petit matos, voire téléobjectif et simple APN sur monture de base OK.

 

Il y a pas mal de suspense, car la réalité ne colle jamais tout à fait avec les prévisions de Don Collins ; en d'autre termes, on ne sait pas exactement quand ça va débuter, même si on en a une petite idée, combien de temps ça va durer, à quelle profondeur ça va aller, ni qui va avoir la primeur de crier "victoire" le premier, avec une observation positive. Belle émulation avec les collègues européens et américains.

 

Ce doit être ma cinquième ou sixième observation depuis 2015, à la grosse louche, et j'y retourne chaque fois avec un plaisir consommé à l'avance. Petit plus cette fois : le ciel et la température seront plus cléments que les fois précédentes - en plein hiver glaglagla gel et tout ça au programme.

 

RDV ici et sur le forum AAVSO pour les news.

 

Ci-dessous, la courbe obtenue lors de la précédente éclipse, histoire de se mettre dans l'ambiance. En haut, les observations, en bas : la prévision.

 

 

6329fd81e999b_eclipsebper.jpg.ef57401320ec9df75b27dbce91e4b96a.jpg

 

 

 

Ci-dessous, le champ imagé avec une FS102 + réduc F6, diaphragmée à 50 mm (résultant fd 12,8), canon 650 D, très fortement défocalisé, afin de contrer la saturation qui arrive très vite. Poses de 180 secondes à 100 iso.

 

 

632a008214f09_BPer20200118blueskylowquality.jpg.c818f7c6432c64d93333325c7958201f.jpg

 

 

 

Bien à vous, hardis les mollets, bons cieux et BONNES MESURES :)

C.

 

 

AAVSO Alert Notice 791

 

September 9, 2022

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
- Campaigns and Observation Reports: https://www.aavso.org/b-per-sep-2022-eclipse
- Eclipsing Binaries: https://www.aavso.org/b-per-sep-2022-eclipse-01

Please subscribe to these threads if you are participating in the campaign so you can be updated by the astronomers and by HQ. Join in the discussion or ask questions there!

Dr. Donald F. Collins (AAVSO member), Dr. Robert Zavala (US Naval Observatory, Flagstaff Station), Jason Sanborn (Lowell Observatory), and Dr. Anatoly Miroshnichenko (University N. Carolina, Greensboro) have requested highly time-resolved observations of the bright star b Persei during the upcoming predicted secondary eclipse of the third star as it passes behind the AB inner pair.

They provide the following information:

"The bright (4.6V) hierarchical triple-star system b Persei (HD 26961, HIP 20070, HR 1324, SAO 24531) consists of a non-eclipsing close-orbiting binary pair (1.53 d period) and a third star in a highly inclined orbit (period = 704.48 d). The close-orbiting binary pair shows ellipsoidal variation of about 0.06 magnitude peak-to-peak. The AAVSO has discovered that the third star undergoes eclipses with the close-orbiting binary pair. These consist of primary eclipses (the third star partially blocks the light from the close orbiting pair) and secondary eclipses (the close-orbiting pair partially or fully block the light of the third star). Previous AAVSO campaign* results beginning in January 2015 are shown in Figures 1 and 2. The light curves show out-of-eclipse ellipsoidal variations as well as relatively deep eclipses during the transits. Eclipses in the b Persei system were unknown until the first AAVSO observations in 2013 (Collins 2013).

"The observation window should last at least 2 weeks beginning about September 19, 2022, which is about 10 days before the predicted date of mid-eclipse (UT September 29.41, 2022 ± 0.1 d ). It is important that observers observe several long time-series observations both before the eclipse and after the eclipse as well as all parts of the eclipse.

“Observers are asked to obtain high-resolution time-series observations of long duration (several hours) in V (or the green channel from DSLR cameras) during the eclipses as well as as many as possible out-of-eclipse time-series observations of the system during the 20-day window centered on the September 29 eclipse (September 19 – October 8). Out-of-eclipse data are needed to calibrate the various offsets expected from different observing systems.

“It is recommended to use the star labeled '55' (AUID 000-BLL-386 = HIP 20156 = SAO 39457 = HR 1330 = HD 270840) in the AAVSO finder chart at 5.456 V for the comparison star. For a check star HIP 20370 (J2000 RA, Dec = 04 21 45.47 +50 02 06.64) may be used if the observer's field of view is about one degree. This star is not in the AAVSO sequence. Any other AAVSO sequence stars may be used as a check star if available in the observer's field of view. New observers are welcome - especially Asian and Pacific observers to help fill the gaps in the transit light curves. Atmospheric scintillations are a major problem with bright star observations due to the necessary short exposure times. These are removed by obtaining many short exposures which can then be averaged by image stacking or averaging the results of many short exposures.

"DSLR guidelines may be found in the AAVSO DSLR Observing Manual. Another resource for DSLR photometry may be found by Buchheim (2018, used with Buchheim’s permission) ."

"Recent campaigns by AAVSO observers (AAVSO Alert Notices 476 (Jan 2013), 507 (Jan 2015), 537 (Feb 2016), 563 (Dec 2016), 610 (Jan 2018), 655 (Oct 2018), 688 (Dec 2019), and 721 (October 2020)) have revealed the following:

1. Both the primary and secondary transits show significant light curve dips in total brightness on the order of 0.1 mag to 0.5 mag.

2. Distinguishing between primary and secondary eclipses has been made possible from radial velocity observations by Anatoly Miroshnichenko, which are shown as a dashed curve for the December 2016 eclipse in Figure 1. The long period radial velocity of the A star shows that the A star begins to approach the Earth after passing from beyond the transit. Only the A star exhibits suitable spectral lines for RV measurements.

3. The orbital period for the C star is 704.5 ± 0.1 d, based on a linear fit to the fitted dates of the four high-resolved time-series of secondary eclipses. The previously published orbital period is 702 d (Hill 1976).

4. Each transit (or eclipse) is different – due to the lack of a simple commensurate relationship between the short period A-B stars and the long period of the of the AB-C triple system.

5. The deepest relative minimum observed occurred during the primary eclipse of January 2020 at mJD 1867.4 (Figure 2). The solid curve in Figure 2 (the simple model) calculates the result if the C star (spectral class F, luminosity 2 x Lsolar) is fully ingressed over the “disk” of the primary star A (spectral class A-V, luminosity 10 x Lsolar).

 

 

bPer-Sep2022-Figure1-AN791.png.f518432690b34257fe55778aac884223.png

 

 

Figure 1. The four previously-observed secondary eclipses of b Persei. The solid black curves are a simple model fit to the observations. The different colors and symbols in the observations represent the individual observations contributed by the various observers. The dashed sinusoidal curve in the middle panel represents the graphical radial velocity of the component star A based on data from A. Miroshnichenko. The red solid sinusoidal curves in each panel represent the fit to ellipsoidal data. The heavy black curves are a simple model fit to the observations.

 

 

bPer-Sep2022-Figure2-AN791.png.55ec79b106dd4896fb425a63c5ffb6df.png

 

 

Figure 2. The four previously-observed by AAVSO primary eclipses of b Persei. The different colors and symbols for the observations represent the different observers who contributed to the data. The solid black curves are a simple model fit to the observations. The lighter sinusoidal curves represent the fit to ellipsoidal data.

 

 

Coordinates (2000): R.A. 04 18 14.62 Dec. +50 17 43.8 (from VSX entry for b Per)

Finder charts with comparison stars for b Per may be created using the AAVSO Variable Star Plotter (VSP).

Please submit all photometry data to the AAVSO International Database via WebObs at the AAVSO site using the name “B PER”.

Be sure to subscribe to the forum threads given above to be advised of latest developments, eclipse onsets, and observing ideas.

References
Buchheim, R. K. 2018, “Lessons from DSLR Photometry of b Per “Third Star” Eclipse (February 2018)”, SAS-2018 The Symposium on Telescope Science and ALPO Annual 2018 Meeting, Proceedings for the 37th Annual Conference of the Society for Astronomical Sciences [http://www.socastrosci.org/Publications.html] pp 71-77.
[Note: Bob Buchheim has given AAVSO permission to make available a stand-alone copy of his presentation on the AAVSO web site for observers' easy access – dfc]

Collins, D. F. 2013, “Observations of an Eclipse of bright star b Persei by the Third Star in February 2013”,, AAVSO Spring 2013 meeting, Boone, NC, abstract only (https://www.aavso.org/sites/default/files/spring%202013%20paper%20sched.pdf).

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen using material provided by Dr. Donald Collins and colleagues.

-------------------------------------------------
SUBMIT OBSERVATIONS TO THE AAVSO

Information on submitting observations to the AAVSO may be found at:
 - Photometry/visual observations: https://www.aavso.org/webobs
 - Spectroscopy: https://www.aavso.org/apps/avspec/

ALERT NOTICE ARCHIVE AND SUBSCRIPTION INFORMATION

An Alert Notice archive is available at the following URL:
https://www.aavso.org/aavso-alert-notices-for-observing-campaigns-and-discoveries

Subscribing and Unsubscribing may be done at the following URL:
https://www.aavso.org/aavso-alert-notice-subscribe

-------------------------------------------------

Please support the AAVSO and its mission -- Join or donate today:
https://www.aavso.org/apps/donate/

 

 

Copyright © 2022 American Association of Variable Star Observers, All rights reserved.
You are receiving this email because you subscribed to the AAVSO Alert Notices. If you wish to unsubscribe, please go to your "My account" page on the AAVSO website and unclick the "Alert Notices" box under the "Email settings" tab. Thank you.

Our mailing address is:American Association of Variable Star Observers

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Etoile double

B Persei

Information du catalogue: Étoiles

Extended Hipparcos Compilation

Magnitude visuelle: 4.600

Indice de couleur B-V: 0.043

Magnitude bleue: 4.643

Magnitude I: 4.444

Classe spectrale: A1III

Mouvement propre en ascension droite: 45.900 [mas/y]

Mouvement propre en déclinaison: -59.700 [mas/y]

Parallaxe: 10.400 [mas]

Distance: 313.6 années-lumière

HD: 26961

BD: BD+49 1150

HIP: 20070

HR: 1324

Composant: A

Bayer: B

Constellation: Persée

Vitesse radiale: 21.0 [km/s]

Coordonnées: Apparente

Apparente AD: 04h19m57.225s DE:+50°20'52.98"

Moyenne de la date AD: 04h19m57.713s DE:+50°20'56.50"

Astrométrique J2000 AD: 04h18m14.726s DE:+50°17'42.42"

SOURCE: CARTE du CIEL

Jean Marc

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Salut Jml !

 

Contrairement à ce qu'indique CdC, b Per est réellement un système triple, dont la première éclipse, pourtant soupçonnée depuis des décennies de se produire à intervalle, n'a été observée qu'en 2013. Depuis lors, il s'agit de caractériser le système. C'est un travail de longue haleine, car il faut attendre 702 jours entre chaque éclipse ...

 

"

The eclipse is nearing.  Predicted JD:2459852.4 =  UT Sept. 29,41 

The beginnings of eclipse typically comes 1.5 to 2 days prior to the midpoint.  That is ~Sept 26 UT.

Don (CDK) "

 

(sans compter une ou deux soirées d'observations préalables)

 

Bons cieux,

C

 

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Salut, je n'y connais pas grand chose en photométrie; la seule chose que je sais faire c'est des vidéos .SER que je réduit sous Tangra. ca peut marcher ?

Ou bien j'acquiers des Fits et quelqu'un d'autre se charge de les réduire ?

J'imagine que les darks sont utiles ? Pour les flats je n'ai jamais trouvé d'écran qui aille...ça va quand même ?

Chez moi ( env. 28° Lat Nord ) b Per n'est pas circum-polaire, ma fenêtre d'observation sera plus réduite.

Jean Marc

 

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Salut Jean Marc,

 

Oui, il faut faire des darks et des flats, et surtout faire en sorte que l étoile ne soit pas saturee, tout en posant suffisamment longtemps pour battre la scintillation qui limite la précision des mesures. En pratique, poser genre une minute, defocaliser et bien fermer les optiques pour réduire le flux. Timing à la seconde ça va bien. Une fois les images pretraitees, je peux soit les mesurer, soit te renvoyer vers un tuto. 

 

Pour ce qui me concerne, après des mois de cieux clairs, la semaine s annonce compliquée.

 

Bon cieis 

C

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Les flats, selon ton optique, un fond de ciel bleu peut suffire. Je fais ainsi et ça marche.

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Il y a 3 heures, chrismlt a dit :

te renvoyer vers un tuto. 

Oui je veux bien et si je n'y arrive pas je t'enverrai les images.

Merci

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Bonsoir Jean-Marc.

 

Tiens, voici un tuto qui devrait te permettre de franchir le pas en photométrie. On s'en fait un monde, mais c'est finalement assez simple. Le plus important, c'est d'acquérir des images susceptibles d'être mesurées sans biais. Dit comme ça ça peut faire peur, mais c'est bien plus facile que de faire des images léchées de belles nébuleuses, la preuve, j'y arrive :D. Un bon timing, un bon prétraitement et aucune saturation, et roule ma poule.

Pour ce qui est de b Per, il faut des mesures avant l'éclipse, et là, ça va commencer à faire short - enfin je ne sais pas comment est ton ciel ce soir. Ici, c'est mort.

Sinon, bah, tu seras prêt pour la prochaine fois. Ou alors tu vois à faire des mesures de variables, des transits d'exoplanètes ... les alertes AAVSO. Une fois qu'on a mordu dans la pomme, ce ne sont pas les fruits qui manquent.

Si tu as un souci, n'hésite pas.

 

https://millimagjournal.wordpress.com/photometrie-iris/

 

Bon ciel,

Christophe

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Il y a 2 heures, chrismlt a dit :

je ne sais pas comment est ton ciel ce soir.

La tempête tropicale "Hermine" s'en va tout doucement... :|

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Salut tous,

 

Une petite précision de la part De D. Collins, sur le forum AAVSO.

 

b Persei transit/eclipse may begin tonight! Monday 24 Sept 2022

There is a  possibility that a partial grazing secondary eclipse of b Persei may begin tonight Sept 26-25  (JD 2459859).  Remember we expect the center of the 3-4 day transit to be Sept. 29.   All observers with clear weather are requested to observe at least one observation per hour (or continuously) throughout the night.  If observing intermittently throughout the night, it is important to observe a burst of images especially exposures are short (less than 60 sec).   A solution is to expose for many exposures of short duration to prevent saturation of detectors and include enough exposures so that the total integration time (exposure time multiplied by the number of images in a burst of images) be larger than about 60 sec.  This reduces the fluctions inherent in scintillations from Earth's atmosphere.  I can co-add the multiple  photometry results from burst from many rapid observations after downloading the results from the AAVSO database.

Please observe as long as possible each night between now and October 2.

Many Thanks in advance to all observers who are braving the post-midnight observation windows for this fall's event!!

Don (CDK)

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