A Method To Remove Fringes From Images Using Wavelets

We have developed a new method that uses wavelet analysis to remove interference fringe patterns from images. This method is particularly useful for flat fields in the common case where fringes vary between the calibration and object data. We analyze the efficacy of this method by creating fake flats with fictitious fringes and removing the fringes. We find that the method removes 90% of the fringe pattern if its amplitude is equal to the random noise level and 60% if the fringe amplitude is $\approx 1/10$ of the noise level. We also present examples using real flat field frames. A routine written in the Interactive Data Language (IDL) that implements this algorithm is available from the authors and as an attachment to this paper.Comment: 7 pages, 14 figures. Accepted to the Astrophysical Journal. (The quality of the figures in this preprint has been downgraded in order to fulfill arXiv requirements. Check journal for the high-quality figures

Estimation of Exoplanetary Planet-to-Star Radius Ratio with Homomorphic Processing

In this paper a homomorphic filtering scheme is proposed to improve the estimation of the planet/star radius ratio in astronomical transit signals. The idea is to reduce the effect of the short-term earth atmosphere variations. A two-step method is presented to compute the parameters of the transit curve from both the unfiltered and filtered data. A Monte Carlo analysis is performed by using correlated and uncorrelated noise to determine the parameters of the proposed FFT filter. The method is tested with observations of WASP-19b and WASP-17b obtained with the FORS2 instrument at the Very Large Telescope (VLT). The multi parametric fitting and the associated errors are obtained with the JKTEBOP software. The results with the white light of the exo-planet data mentioned above suggest that the homomorphic filtering can lead to substantial relative reductions in the error bars as high as 45.5% and 76.9%, respectively. The achieved reductions in the averaged error bars per channel were 48.4% with WASP-19b and 63.6% with WASP-17b. Open source MATLAB code to run the method proposed here can be downloaded from http://www.cmrsp.cl. This code was used to obtain the results presented in this paper

CE-315 : A New Interacting Double-degenerate Binary Star

We present spectroscopic observations of object CE-315 revealing a blue continuum with strong emission lines. Most of the detected lines are identified with He I or He II in emission with a handful of faint lines of nitrogen. Notable is the complete absence of hydrogen lines. The He lines exhibit triple-peaked profiles with remakably broad widths, of about 2000 km/s (FWZP). The observations show that CE-315 is an interacting binary system with an orbital period of 65.1 +/- 0.7 minutes, and a mass ratio of 0.022. We conclude that the most likely scenario for this object is that of an accreting 0.77 solar mass white dwarf with a 0.017 solar mass helium white dwarf as mass donor.Comment: Astrophysical Journal, 20 page

The Peculiar Photometric Properties of 2010 WG9: A Slowly-Rotating Trans-Neptunian Object from the Oort Cloud

We present long-term BVRI observations of 2010 WG9, an ~100-km diameter trans-Neptunian object (TNO) with an extremely high inclination of 70 deg discovered by the La Silla - QUEST southern sky survey. Most of the observations were obtained with ANDICAM on the SMARTS 1.3m at Cerro Tololo, Chile from Dec 2010 to Nov 2012. Additional observations were made with EFOSC2 on the 3.5-m NTT telescope of the European Southern Observatory at La Silla, Chile in Feb 2011. The observations reveal a sinusoidal light curve with amplitude 0.14 mag and period 5.4955 +/- 0.0025d, which is likely half the true rotation period. Such long rotation periods have previously been observed only for tidally-evolved binary TNOs, suggesting that 2010 WG9 may be such a system. We predict a nominal separation of at least 790 km, resolvable with HST and ground-based systems. We measure B-R = 1.318 +/- 0.029 and V-R = 0.520 +/- 0.018, consistent with the colors of modestly red Centaurs and Damocloids. At I-band wavelengths, we observe an unusually large variation of color with rotational phase, with R-I ranging from 0.394 +/- 0.025 to 0.571 +/- 0.044. We also measure an absolute R-band absolute magnitude of 7.93 +/- 0.05 and solar phase coefficient 0.049 +/- 0.019 mag/deg.Comment: 17 pages, 5 figure

Millimagnitude Photometry for Transiting Extrasolar Planetary Candidates III: Accurate Radius and Period for OGLE-TR-111-b

We present accurate V-band photometry for a planetary transit of OGLE-TR-111 acquired with VIMOS at the ESO Very Large Telescope. The measurement of this transit allows to refine the planetary radius, obtaining R_p= 1.01 +/- 0.06 R_J. Given the mass of M_p = 0.53 M_J previously measured from radial velocities, we confirm that the density is rho_p= 0.6 +/- 0.2 g/cm^3. We also revise the ephemeris for OGLE-TR-111-b, obtaining an accurate orbital period P= 4.014484 +/- 0.000014 days, and predicting that the next observable transits would occur around December 2006, and after that only in mid-2008. Even though this period is different from previously published values, we cannot yet rule out a constant period.Comment: 16 pages (including figures), 5 figures, 1 table. Accepted for publication in the Astrophysical Journa

ALMA Observations of Io Going into and Coming out of Eclipse

We present 1-mm observations constructed from ALMA [Atacama Large (sub)Millimeter Array] data of SO₂, SO and KCl when Io went from sunlight into eclipse (20 March 2018), and vice versa (2 and 11 September 2018). There is clear evidence of volcanic plumes on 20 March and 2 September. The plumes distort the line profiles, causing high-velocity (≳500 m/s) wings, and red/blue-shifted shoulders in the line profiles. During eclipse ingress, the SO₂ flux density dropped exponentially, and the atmosphere reformed in a linear fashion when re-emerging in sunlight, with a "post-eclipse brightening" after ∼10 minutes. While both the in-eclipse decrease and in-sunlight increase in SO was more gradual than for SO₂, the fact that SO decreased at all is evidence that self-reactions at the surface are important and fast, and that in-sunlight photolysis of SO₂ is the dominant source of SO. Disk-integrated SO₂ in-sunlight flux densities are ∼2--3 times higher than in-eclipse, indicative of a roughly 30--50% contribution from volcanic sources to the atmosphere. Typical column densities and temperatures are N ≈ (1.5±0.3)×10¹⁶ cm⁻² and T ≈ 220−320 K both in-sunlight and in-eclipse, while the fractional coverage of the gas is 2--3 times lower in-eclipse than in-sunlight. The low level SO₂ emissions present during eclipse may be sourced by stealth volcanism or be evidence of a layer of non-condensible gases preventing complete collapse of the SO₂ atmosphere. The melt in magma chambers at different volcanoes must differ in composition to explain the absence of SO and SO₂, but simultaneous presence of KCl over Ulgen Patera