The solar limb during eclipses: Flash Spectrum Region and Baily beads

Costantino SigismondiICRA-Sapienza, Roma; Université de Nice-Sophia Antipolis

and IRSOL Istituto Ricerche Solari di Locarno

sigismondi@icra.it

post-éclipse meeting, IAP 30.9.2010

ICRA and solar physicswww.icra.it/solar

Participating institutions

ICRA, International Center for Relativistic AstrophysicsSapienza University of Rome # IOTA ES and US * #Osservatorio Astronomico di Roma #Basilica di Santa Maria degli Angeli, Roma *Yale Astronomy Department #Université de Nice-Fizeau Dept. #Observatoire de la Cote d'Azur(Calern site PICARD Sol)*Institute d'Astrophysique de Paris * #IRSOL * ## data and analysis * observations (CLAVIUS)

Classification of Solar diameter measurements

Measuring radius from Earth

Drift-scan:

solar angular speed * transit time = diameter

problem: seeing

• Angular direct measurements– problem: seeing, optical aberration

• Mercury and Venus transits: planetary speed * transit time = diameter

- problem: scintillation, black drop

• Eclipses with Baily’s beads– problem: scintillation, signal to noise, filter, FSR

Last solar cycle XXIII: SOHO data (June 2010)

Calibrating eclipses for studying secular variations

Eclipse Problem 1: scintillation

Problem 2: Flash Spectrum Region

Flash Spectrum (1905)

Problem 3: lunar profile

Watts (1962) σ>0.2” randomKaguya (2009) σ<<0.01” sampling each 0.5”-5”

Sampling 1-10 km

Real lunar limb vs Watts profile (Kilcic, Sigismondi, Rozelot &

Guhl, So. Phys. 2009)

10 km

Locarno Solar Obsevratory IRSOL Istituto Ricerche Solari di Locarno

δR=-0.41”±0.05 ” (Kilcic et al. 2009)

on 29 march 2006,in agreement with SOHO 2003 data

preliminary:δR=-0.36”±0.15” on 15 Jan 2010,based on 6 beads from R.Nugent

LIMB DARKENING FUNCTION WITH BAILY’S BEADS ANALYSIS

Andrea Raponi and C. SigismondiSapienza University of Rome

Total Solar Irradiance changed in the past, so also the diameter?

Hendrick Avercamp (1585-1643), Amsterdam

Eclipses

Beads of 15/01/2010 by R. Nugent with Kaguya profile; software Occult

Solar Limb and LDF

seeing and inflection point

Baily’s bead light curve

depends on

Valley’s profile

+ real LDF

scintillation

LDF and Flash Spectrum Region?

computing LDF from light curve and Kaguya lunar profile

LDF from 2 different beads x:units of 6 mas

Synthetic LDF from Poissonian noise

Notes: quartz oscillators physicsThewlis Enc. Dictionary of Physics, Pergamon Press 1962 Quartz, the

preparation and use of, oscillators

Annular Eclipse of 22/9/2006 2 watches: SONY e CASIO

in French Guyana the temperature was > 8 °C than in Rome

Roman tradition in solar diameter

….and in eclipses:In 1581 edition Clavius wrote:

relinquebatur in Sole circulus quidam exilis undique totam lunam ambiens. He actually saw an annular eclipse. The Sun in 1567 was >2.5 arcsec larger than now ? Not possible for physical reasons…