Outburst στον U Sco!!!

[ΙΑΝΟΣ]

Δύο ερασιτέχνες αστρονόμοι από την Φλόριντα ανίχνευσαν πρώτοι την δραστηριότητα που φαίνεται πως έχει ξεκινήσει στον επαναληπτικό καινοφανή U Sco, έντεκα χρόνια μετά το τελευταίο outburst που είχε εμφανίσει στις 25 Φεβρουαρίου του 1999 φτάνοντας το μέγεθος των 7.5 mag.

 

Το σύστημα U Sco αναμένεται να παρατηρηθεί έντονα τους επόμενους μήνες από επαγγελματίες και ερασιτέχνες αστρονόμους , αλλά και από τα τηλεσκόπια Hubble, Swift και Spitzer που από την πρώτη στιγμή καταγράφουν όλα εκείνα τα στοιχεία που θα βοηθήσουν τους αστρονόμους να ξεκλειδώσουν τα μυστήρια των λευκών νάνων, των αλληλεπιδρώντων διπλών συστημάτων, των δίσκων προσαύξησης και τους προγόνους των υπερκαινοφανών τύπου Ia.

 

Ο U Sco είναι ένας εξαιρετικά γρήγορος καινοφανής (extremely fast nova). Αυτή τη στιγμή διανύει τις μέγιστες τιμές της λαμπρότητάς του (περίπου 9mag) ενώ πολύ γρήγορα θα ξεκινήσει το σύντομο ταξίδι της επιστροφής του προς το 19ο μέγεθος χάνοντας περίπου 1 mag, της λαμπρότητάς του, κάθε 24 ώρες!

 

Αν και δύσκολη η εποχή που διανύουμε για παρατηρήσεις στον αστερισμό του Σκορπιού, παραθέτω έναν χάρτη της περιοχής. Για περισσότερες πληροφορίες:

www.aavso.org

 

 

 

 

φιλικά,

Θανάσης

[PapGeo]

Ευχαριστούμε για την ενημέρωση!

 

 

Update 2010 January 29:

 

"...Spectroscopy by observers in Japan and India has revealed similar spectroscopic features to those seen before, notably the very broad emission lines indicating a large expansion velocity for the ejected nova shell; the edges of the shell are travelling at 11,000 kilometers per second relative to the the star! "

[Bi2L]

Ευχαριστουμε Θαναση,

 

 

 

εδω το λινκ AAVSO Alert Notice 415 - Recurrent Nova U Scorpii in outburst

 

 

 

Αν και δύσκολη η εποχή που διανύουμε για παρατηρήσεις στον αστερισμό του Σκορπιού, παραθέτω έναν χάρτη της περιοχής.

Για οποιον θελει παντως να τον παρατηρησει, ο Σκορπιος ανεβαινει τις πρωινες ωρες.

[Bi2L]

πηγη skyandtelescope.com

http://www.skyandtelescope.com/community/skyblog/observingblog/43435242.html

U Scorpii: Recurrent Nova About to Blow Up?

April 29, 2009

by Bradley E. Schaefer

 

Novae explode without warning, and even recurrent novae are pretty unpredictable. (For instance, we've been waiting way too long for T Pyxidis to erupt again; see Sky & Telescope, April 2002, page 93).

 

 

Scorpius is well placed after midnight or 1 a.m. in May, by late evening in June, and after dark in July and August. On the chart above, the black square shows the area of the closeup comparison-star chart below. Click on the chart for a larger, more printable view.

Sky & Telescope diagram

 

 

But here's a prediction about a recurrent nova that should go off in a specific year: 2009. I've calculated that the recurrent nova U Scorpii, north of Antares and east of the head of Scorpius, should explode any month now. My "crystal ball" is based on old archival photographs and data from amateur astronomers. This brings a golden opportunity for amateurs and professionals to catch the early hours of a nova eruption and to prepare in advance for an intensive observing campaign.

 

"Recurrent novae" are those that have had more than one eruption observed within a century or so. Classical novae too are believed to repeat, but on timescales of perhaps 1,000 to 100,000 years; we just haven't been watching long enough to see them do it yet.

 

U Sco is one of the most famous recurrent novae. In quiescence it usually hovers around magnitude 17.6, but in outburst it briefly shoots up by about 8 or 9 magnitudes. In fact, U Sco is the all-time fastest nova known. Its brightening from minimum to maximum takes only about 5 hours, and its decline to two magnitudes below maximum takes about 38 hours. U Sco's last three eruptions, in 1979, 1987, and 1999, were all discovered by amateur astronomers.

 

 

Comparison-star magnitudes (courtesy AAVSO) are given for stars around U Scorpii with decimal points omitted. Click on the chart for a larger, more printable version.

Sky & Telescope diagram

I've thoroughly searched the old photographic sky-patrol plates stored at the Harvard College Observatory, and old magnitudes recorded in the archives of the Royal Astronomical Society of New Zealand, to discover three more eruptions of U Sco. With these, the pattern of eruption since 1900 has been once every 10 ± 2 years. (Eruptions were likely missed around 1927 and 1957 because Scorpius is hidden in conjunction with the Sun every November and December). Based on this, a simple expectation is that the next eruption will come about 10 years after 1999.

 

But a better, physically-motivated calculation can be made from the brightness records of the star between eruptions. Like other cataclysmic variables, U Sco is a close binary pair with one star feeding a stream of hydrogen onto a companion white dwarf. When the hydrogen piles up deep enough on the white dwarf's surface, it explodes in a runaway thermonuclear reaction — a thin-shell hydrogen bomb. The system's brightness in quiescence (slightly variable) is a measure of the rate at which matter is falling onto the white dwarf. Based on past eruption cycles, we know when enough accumulates to trigger the explosion. Using this, the prediction is for an eruption is April 2009 ± 1.0 year.

 

In other words, sometime in the next year more likely than not.

 

Ναι το κειμενο ειναι απο τις 29 Απριλίου, 2009

αλλα οι χαρτες παραμενουν οι ιδιοι...