Preliminary results from the occultation of Epsilon Geminorum by Mars on 8 April 1976

Abstract

view Abstract Citations (4) References (5) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Preliminary results from the occultation of epsilon Geminorum by Mars on 8 April 1976. de Vaucouleurs, G. ; Nather, R. E. ; Young, P. J. Abstract Preliminary reduction of the light curve observed with a pulse-counting photometer (10-msec resolution) at the 91-cm reflector of McDonald Observatory gives the following ingress, egress, and mideclipse times for the half-intensity points: Ingress 1=00h 55" 30'.62 +0'. 19 UTC; Engress 1=01h 00" 22'.39 +0'. 17 UTC; p = h 57" 56'.51 +0.13 UTC; Apparent duration=291'.77+0'.26 =6.0338+0.0054. The dis- appearance curve at ingress had an apparent scale height A'1 = 0' .0131+ 0'.0016 (m.e.) corresponding, for an assumed angle of 23' between the star path and the vertical, to a normal scale height A =0'.0120= 12.9 + 1.4 km. There were two bright flashes (observed also visually) about 3 and 5 sec after the half-intensity point. The reappearance curve at egress was much steeper and peculiar in shape, the apparent scale height A'a=0'.0086+ 0'.0008 corresponds to A =O'.OO79 = 8.5+0.8 km. Assuming a pure, molecular CO2 atmosphere and an effective gravity g (z i)= 356 cm sec at the occultation level (z 8 1 km), the re- lation between scale height and temperature is T = 18.84 A, giving T1 =243+26 K at ingress and T = 160 + 15 K at egress. The reduced mass of gas above the half-intensity level was m = 8.1 mg (=4.1 cm STP) at ingress, m a =2.9 mg (= 1.4 cm STP) at egress, corresponding to an atmospheric pressure P =(2.87+O.78) atm =(2.91+0.79) dyn at ingress, pa=(1.01+0.26) atm =(1.11+0.26) dyn at egress. The optical depth of CO2 for ultraviolet radiation below the photodissociation threshold ( < 1700 A) justifies a posteriori the assumption of a pure, molecular atmosphere. Publication: The Astronomical Journal Pub Date: December 1976 DOI: 10.1086/111998 Bibcode: 1976AJ.....81.1147D Keywords: Light Curve; Mars (Planet); Stellar Occultation; Stellar Spectrophotometry; Atmospheric Refraction; Visual Observation; Astronomy full text sources ADS | data products SIMBAD (1)