IAU Circulars and Ephemerids of HD209458 transit

update: 2 December 1999

Circular No. 7323
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION

HD 209458
E. Poretti, Brera Astronomical Observatory, writes: "Forty-six V photoelectric measurements of HD 209458 obtained with the Merate 0.5-m telescope show that a transit (depth 0.016 +/- 0.002 mag) started at Nov. 25.815 UT. Observations began at Nov. 25.74, but stopped at Nov. 25.91 due to large airmass, before egress. Analysis of B photometry is in progress."
Independent reports have been received from S. Soderhjelm, Lund Observatory; and from N. Robichon and F. Arenou, DASGAL, Observatoire de Paris, Meudon, of the existence of five HD 209458 transits in 89 separate Hipparcos photometric measurements obtained between 1991 Apr. 17 and Nov. 4. Robichon and Arenou report that the mean depth of the transits is 0.025 +/- 0.004 magnitude in the Hipparcos H_p band, corresponding to a relative depth in the flux of 2.3 +/- 0.4 percent (results submitted to A.Ap.). Using the epoch T_c of Charbonneau et al. (submitted to Ap.J. Lett.; see also IAUC 7315), periods of 3.524738 +/- 0.000015 (Robichon and Arenou) and 3.52473 +/- 0.00005 (Soderhjelm) days have been derived. Soderhjelm's details will appear on IBVS 4816.

Circular No. 7315
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION

HD 209458
In response to a request from the Central Bureau, D. W. Latham, Harvard-Smithsonian Center for Astrophysics, communicates on behalf also of D. Charbonneau, T. M. Brown, M. Mayor, and T. Mazeh: "We have prepared an updated ephemeris for the transits of HD 209458. This ephemeris is based on 150 velocity observations dating back to Aug. 1997 (made with HIRES on Keck I, as part of the G Dwarf Planet Search under NASA time, with ELODIE on the 1.93-m telescope at Observatoire de Haute Provence, and with CORALIE on the new Swiss 1.2-m telescope at La Silla; a paper describing the spectroscopic results is in preparation) and on two complete transit observations obtained on 1999 Sept. 8 and 15 (made by Charbonneau and Brown with the STARE instrument at the High Altitude Observatory, National Center for Atmospheric Research, Boulder, and reported in a paper submitted to Ap.J. Lett. by Charbonneau, Brown, Latham, and Mayor). G. Torres has carried out a simultaneous solution of the radial velocities and the transit observations and provided the following orbital period and epoch of transit center: P = 3.52433 +/- 0.00027 days, T_c = 2451430.8238 +/- 0.0033 (HJD). Predictions for the center of the transits through the end of Dec. 1999 are: HJD 2451508.3590 +/- 0.0080, 2451511.8833 +/- 0.0083, 2451515.4077 +/- 0.0086, 2451518.9320 +/- 0.0089, 2451522.4563 +/- 0.0091, 2451525.9806 +/- 0.0094, 2451529.5050 +/- 0.0097, 2451533.0293 +/- 0.010, 2451536.554 +/- 0.010, 2451540.078 +/- 0.011, 2451543.602 +/- 0.011. Observers should plan to monitor the star for at least 2 hr before and after these times of transit center. Our identification of HD 209458 as a prime target for transit observations was made possible by the many contributions of the G Dwarf Planet Search, ELODIE, and CORALIE teams: J. L. Beuzit, M. Burnet, G. A. Drukier, D. Naef, F. Pepe, C. Perrier, D. Queloz, N. Santos, J. P. Sivan, G. Torres, S. Udry, and S. Zucker."

Circular No. 7314
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION

HD 209458
R. Rebolo, M. R. Zapatero Osorio, H. J. Deeg, and J. Licandro, Instituto de Astrofisica de Canarias; and J. Marti, University of Jaen, report: "CCD photometry of the star HD 209458 obtained at the 1.5-m Spanish Telescope at Calar Alto reveals a transit egress of the planet reported on IAUC 7307, with a depth of 0.023 +/- 0.005 mag, on Nov. 18.87 UT. Ingress started before observations, but assuming an orbital period of 3.523 days, the transit lasts 3.0 +/- 0.1 hr. Best fits give an orbital inclination of 87.0 +/- 0.5 deg and a planet radius 1.34 +/- 0.07 that of Jupiter."
R. A. Street, T. A. Lister, A. Cameron, and K. Horne, St. Andrews University, report that 640-nm narrowband CCD photometry of HD 209458 with the 0.9-m Gregory telescope in St. Andrews confirms that a planetary transit with depth of 0.019 +/- 0.003 mag occurred from Nov. 18.760 +/- 0.021 to 18.903 +/- 0.031 UT. Z. Ioannou, C. Hellier, R. D. Jeffries, and T. Naylor, Keele University, report that V-band photometry with the 0.6-m telescope at Keele Observatory are consistent with an egress as reported above, but the increasing airmass makes the data from this time onwards unreliable. For further details, see http://star-www.st-and.ac.uk/~ras11/indexPS.html."

Circular No. 7317
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION

HD 209458
G. Gonzalez, University of Washington, writes that he obtained differential CCD photometry of HD 209458 during Nov. 22.07-22.35 UT, using the the Manastash Ridge Observatory 0.76-m telescope, with C. Laws and M. Braunstein. An 8-nm-side filter centered at 673 nm was used to obtain images every about 3 min. They detect a dimming of HD 209458 starting at Nov. 22.28 +/- 0.015 day, but they did not observe long enough to see last contact, due to the low altitude of the star. They estimate that the dimming amounted to about 0.028 mag (using two comparison stars that were each about 4 mag fainter than HD 209458).