Field Trip To Observatoire De Haute-Provence Report

Field Trip To Observatoire De Haute-Provence ReportShaoshan ZengAbstractA group of 9 students from University College London (UCL) exit be visiting the Observatoire de Haute-Provence (OHP) in France between 14th February and 22nd February 2015. Students are expected to use the CCD camera on the 1.20m setting to image 2 RR Lyrae unsettled sensations XY CVn and RR Gem. Also, students depart use the Aurelie spectrograph on the 1.52m telescope to harbour high up resoluteness spectra of lambent spectroscopic binary systems within the spectral region 4070-4130. The main subject of this report will focus on the observing facilities available at the OHP and background information of the objects to be targeted. And the last section of this report is the observing journal containing solely the data obtained at the telescope.ContentsOverview of lObservatorie de Haute-Provence (OHP)Brief HistoryLocationPrevious scientific workObserving conditionsObserving InstrumentsThe 1.20m reach The 1.52m TelescopeThe Aurelie SpectrogrphScientific Programme for 1.2m TelescopeScientific Programme for 1.52m TelescopeTargetsRR Lyrae inconstant starsSpectroscopic binariesObserving DiaryReferencesAppendix 1. Light curves of RR Lyrae variable stars.Appendix 2. Finder Charts1. Overview of lObservatorie de Haute-Provence (OHP)HistoryThe observatory is owned by the Centre National de la Recherche Scientifique (CNRS) and is funded by the Institut National des Sciences de lUnivers (INSU). Originally, OHP was built as a national facility for Frence astronomers in 1937 and later on in 1949, the facilities at the OHP were available to be used by foreign visiting astronomers. In 1943, the scratch astronomical observations were do with the 1.20m telescope and the first research paper were published a year later.1.2 LocationOHP is located in St Michel, near Forcalquier in the Alpes de Haute-Provence, southeastern France. The coordinates of OHP areLongitude = 0h 22m 52s ELatitude = +43 5 5 46Altitude = 650mPrevious scientific workOHP has done some remarkable work on the detection of extra-solar planets. This studies started with the discovery of 51 Peg-b in 1995 using the ELODIE spectrograph on the 1.93m telescope and fol low-pitcheded by many more discoveries such as Glises 876, the third nearest known star to the Sun were found in 1998 and HD190228b was announced in 2000 as a giant planet orbiting the host star. In 2006, ELODIE was replaced by a stabilised high resolution spectrograph called SOPHIE at the 1.93m telescope of OHP. It is operated by using a large survey for search for northern extrasolar planets through the radial velocity method. Nowadays, SOPHIE plays a significant contribution to the follow-up of transiting exoplanet candidates from photometric surveys include SWASP, CoRoT and Kepler.1.4 Observing ConditionsThe reason for OHP grounded on this site is mainly because the benefit of having higher probabilities on clear switch and favourable weather conditions throughout the year and the average atmospheric extinction at OHP is approximately twice that for ESO at La Silla. On average, about 60% of nights are considered to be suitable for astronomical observations. This can be showed by the yearly breakdown which based on a statistics made from 1965 to 2004 170 nights are excellent conditions, 50 nights with very s dispirit cloud and 70 nights are being partly cloudy. Despite of the weather conditions, the image attribute is as well the key factor to provide advantageously observation. At OHP, the seeing disk is just about 2 arcsec and can be lower down to 1 arcsec occasionally which compares to the image quality at ULO is about 4-5 arcsec. However, about 45 days per year on average (commonly in winter) cold wind flows from the northwest which is known as Mistral would cause the degradation of seeing, sometimes the quality of the seeing can severely decline to over 10 arcsec. But the advantage of having the Mistral winds is good weather usually follow as the winds usually clear up the slash.2. Observing InstrumentsThere are four main telescopes operate at OHP 1.93m, 1.52m, 1.20m and 0.80m. Typically, 1.52m and 1.20m telescopes will be used to undertake studies during the field trip.2.1 The 1.20m TelescopeThis is the first telescope installed at OHP and operates since 1943. It only has a Newton focus which is corresponded to a focus proportionality of f/6. As an improvement, the telescope is now equipped with a CCD camera for direct imaging and photometry. It is usually operated for studies of variability of X-ray sources, imaging of galaxies and H II regions as well as the faint solar system objects.2.2 The 1.52m TelescopeThis is the telescope that have been in use since 1967 at OHP and is used accompanied with the high resolution Aurelie spectrograph which is positioned at the Coude focus. Thus, most of the spectroscopic studies are carried out by using this telescope. The Coude focus is the only f ocus of this telescope and the focal proportionality is f/27.6 which is almost identical to the 1.52m telescope at the ESO at La Silla. Even though it needed to be pointed manually, all other functions are automated. The telescope is equipped with a CCD camera, used from acquiring the target and automatic guiding. The camera has a field of view of 3 x 4.2.3 The Aurelie SpectrographThe Aurelie spectrograph is a high resolution spectrograph that has been developed and installed on the 1.52m telescope in 1989 at the OHP. The goal of using such high quality promoter is to obtain spectra at very high resolutions over the spectral range of 3900 to 10000 and because of the average seeing conditions at the OHP, the Aurelie spectrograph is overly designed to obtain the largest optical efficiency and small amount of scattered light with an entrance aperture at about 3 arcsec wide. The detector attached to the spectrograph is called Thomson TH7832 which is a elongated array CCD-like detect or. The array is made of 2048 pixels of which 2036 are usable. The advantage of using this detector is it is very clean meaning it exhibits no interference fringes or persistence effect and this would give the benefit to detect very weak absorption lines.3. Scientific Programme for 1.2m TelescopeThe main purpose of this programme is to obtain images of two RR Lyrae variable stars RR Gem and XY CVn by using Cousins B- and V-band filters followed by calibrating these images with respect to stars of known magnitude near to the target star. This will be down over the course of 6 nights with 1.2m telescope. As a result, light curves of these stars will be obtained over several cycles of variation in order to calculate the pulsation period of each of the two stars. The light curve of XY CVn will be compared to that of RR GEM as the light curve of XY CVn is more symmetrical. From experience gained last few years (between 2003 and 2014) of UCL field trips who also faultless the task with the same telescope, CCD and filters conclude that the movie times should be around 1-3 minutes in each of the filter for RR Gem and because XY CVn is fainter than RR Gem, it requires longer ikon time of around 4 minutes in each of the B and V-bands. If the star has magnitude at around 11, a signal to noise balance of at least 100 should be obtained with a 60 second or even shorter exposure in the V-band. The same signal to noise ratio is also kept for the B-band.Other than evaluating the result obtaining in the programme, observations of these two targets will also be compared to those obtained during the UCL field trip of 2000 to 2014. This should give more accurate work out period and overtone modulation of the light curves to the stars.RR Lyrae stars are pulsating variables with about half the the great unwashed of the Sun but probably much older and hotter than the Sun. They belong to low mass Population II and they are abundant in globular clusters. RR Lyrae variables are special because they growing larger and smaller in size with their smarting changing significantly. In general, they have periods of 0.2 to 1 day and spectral types of A2 to F6 which have an average effective temperature of 7000K and a luminosity typical around 80 Lsun. close to of them have similar light curves to those of Cepheid variables and obey a period luminosity relation which is approximatelyLog10 P = -0.85M + constantThese properties make RR Lyrae variables become excellent mensuration candles as if the period of time it takes for an RR Lyrae to go through its cycle of brightening and dimming is known, then the absolute luminosity of that star can be estimated. The absolute luminosity shows how bright a star would be if it was a certain distance away from us. From this, the distance to the star can be determined if the measure brightness of the star appear to us compared to its absolute luminosity.4. Scientific Programme for 1.52m TelescopeFor this programme, the Aurel ie spectrograph on the 1.52m telescope will be used to obtain high resolution spectra of a selection of targets which are known to be spectroscopic binary systems that in the spectral region of 4070-4130. By analysing these spectra, weak absorption lines should be decided to measure the changes in the radial velocity of a star by applying the cross correlation technique. Since the field trip group in 2006 and 2010-2014 also completed the similar task with Aurelie, the analysed results from this field trip will be compared to those obtained in previous years and hopefully this will result in an improvement of chassis coverage for all of the systems, especially for targets with long period. By combining all the data sets, a number of physical parameters such as the mass ratio, the mass function, the period and the orbital eccentricity can be estimated for each binary system. As H (4101) is included in the targeted spectral region, the appearance of this line in obtained spectra also need to be investigated as it changes as a function of spectral type.In order to resolve the weak lines and measure their wavelengths accurately, a spectrographic resolving power power of at least R = 40000 is required. Such high resolution that in use should also provide accurate information of radial and rotational velocities for each target. A wavelength coverage of at least 60 is needed to include enough weak lines simultaneously and to make sure the continuum level outback(a) the H line could be estimated. Despite of these, useful weak lines can only be obtain with a signal to noise ratio of at least 250 due to the fact that the equivalent widths of the weak lines are expected to be with several m. And more importantly, the total integration time of all of the start should be controlled to be 120 minutes or less because the resolution of orbital phase of 1.52m telescope would become poor if longer exposure time is used.Spectroscopic binaries involve two stars orbiting around their common centre of mass. These two stars are so close together that can only be seen as one object, and over period of time, there is Doppler shift change in the observing spectrum. In other words, if the star does exist in a binary system, they are of similar luminosity, each spectral line will twice over the course of one orbit, split into two, reach a supreme separation and then move back together again due to the Doppler shift caused by their radial velocity. Among all the targets, the star Uma is of particular pursuance as it has a long period of 44 years while other target stars have relatively short periods and has an orbit that is not clearly determined. It thought to have passed periastron in 2000, so it would be interesting to compare its measured radial velocity with that from spectral obtained during 2006 to 2014.5. Target stars5.1 RR Lyrae Variable StarsThe stars that will be observing for the investigation of the light curves of RR Lyrae variable stars on the 1.2m telescope are shown below in skirt 1 along with their coordinate, magnitudes and period.Table 1. Investigate RR Lyrae variable starsRR Gem is a type a RR Lyrae variable, it is well located for observation between UT 1800 to 2400 in late January to February at OHP. This light curve of this type of star will show a steep increase in brightness at first, the brightness will then lightly fade away until a minimum is reached.The finding charts for RR Gem can be found in Appendix 1. (A1) and the calibration stars are shown in Table 2 below.Table 2. Calibration stars for RR GemXY CVn is a type c RR Lyrae variable, it is well located for observation in the morning in January and February at OHP. antithetical to RR Gem, the light curve of this type of star is more symmetrical.The finding charts for both target stars can be found in Appendix 1.5.2 Spectroscopic binaries targetsThe stars for which I am responsible for background research for the programme occurring on the 1.52m telesco pe are shown in Table 3 below.Table 3. Spectroscopic binaries targetsBoth of the targets are circumpolar which will never set throughout the night, this makes them easily observable in night time. For HR 4072, it would be best observed at around 000-100 UT and CrB should be best observed at 600-700 UT as these time will be the target just crossways the meridian i.e at their highest point in the sky. However, 600-700UT would correspond to 700-800 local time at OHP, would pass the sun rise time and the sky is bright already. Thus, target CrB can be observed in the early morning before sunrise when it still high up in the sky before crossing the meridian.The finding charts for both target stars can be found in Appendix 2.6. Observing JournalReferenceshttp//www.obs-hp.fr -the OHP websitehttp//www.simbad.com -online star cataloguehttp//www.aavso.org/ -online database for variable stars, obtain light curves and finding charts2015 UCL Field Trip Observation Plans (Stephen Boyle, Septemb er 2014)Appendix 1A1. Finding Chart of RR Gem (AAVSO)A2. Finding chart of XY CVn (AAVSO)