Spectroscopic madness—A golden age for amateurs Thomas Eversberg Schno¨rringenTelescopeScienceInstitute(STScI),AmKielshof21a,51105Ko¨ln,Germany Publishedinproceedingsof 1 ”StellarWindsinInteraction”,editorsT.EversbergandJ.H.Knapen. 1 0 Fullproceedingsvolumeisavailableonhttp://www.stsci.de/pdf/arrabida.pdf 2 n a J 4 Abstract: Today,professionalinstrumentationisdominatedbyheavilyoversubscribedtelescopeswhichfocus ] mainly on a limited number of “fashionable” research topics. As a result, time acquisition for massive star R S research, including extended observation campaigns, becomes more difficult. On the other hand, massive star . investigationsbyamateurastronomersperformingspectroscopicmeasurementsareonalevelwhichcanfulfil h p professional needs. I describe the instrumentation available to the amateur, their observational skills and the - o potentialcontributiontheycanmaketotheprofessionalcommunity. r t s a 1 Introduction [ 1 v The so-called “Golden Age of Astronomy” not only influences professional scientific work but also 0 the amateur domain. Large instrumentation such as 1m class telescopes have reached the amateur 8 6 domain(Fig.1)andopticsandCCDdetectorsareavailableoff-the-shelfforrelativelylowprices. To- 0 dayamateurscanaccomplishextraordinaryspectroscopicresults,whichwouldhavebeenimpossible . 1 afewdecadesago. Forinstance,atypicalamateurdeepskyobserverwithasmallhometelescopecan 0 achieve results comparable to modern professional instrumentation, as shown in Fig. 2 for the Hub- 1 1 ble Deep Field. Only about two decades ago amateur astronomers began with serious spectroscopic : v measurementsofrelativelybrightobjects,guidedbyprofessionalneeds. Todayaworldwidenetwork i X ofspectroscopistswithhotspotsinFranceandGermanyhasbeenestablished. Itincludesinstrumen- r tal experts who build their own equipment, scientists by education and pure beginners. Information a exchange is done via internet (mailing lists, discussion forums, websites) and regular international conferences. Itculminatesinvariousprofessional-amateur(ProAm)projects,mainlyonhotstars. 2 State-of-the-art amateur spectroscopy In the past few years, various spectrographs have been successfully designed and constructed by dedicatedamateurastronomersusingoff-the-shelfopticsandblazedgratings,andhavebeenproperly adapted to respective telescopes. Two examples using standard photographic optics are shown in Fig. 3. The first generation of instruments delivering a spectral resolution of more than 10.000 are now also available commercially. The most popular device is the LHIRES III Littrow spectrograph Workshop“StellarWindsinInteraction”ConventodaArra´bida,2010May29-June2 Figure1: The1.2mMelletelescopeisthelargestamateurinstrumentinGermany. Figure 2: The Hubble Deep Field. Left: HST. Right: C14, 18h exposure time, 10km outside Cologne. Thefaintestobjectshaveabout23magnitudesinV. CourtesyJo¨rgZborowska. by the company Shelyak in France (Fig. 4). Because of its simple plug-and-play design for typical amateur telescopes like Celestron and Meade it is widely used for different campaigns (see below). Above this, skilled amateurs now start to design their own Echelle spectrographs. Two examples are shown in Fig. 5. Today, the first off-the-shelf Echelle spectrographs are also available, including a complete and tested software routine for a “plug-and-play” data reduction chain (Fig. 6)1. Amateur andoff-the-shelfEchellespectrographshavethesameperformancebutareoftencheaperthansimilar professional prototypes for small telescopes. This is mainly due to commercial off-the-shelf serial production. 3 Long-term campaigns, surveys, monitoring Amateur spectroscopic equipment can easily be used for scientific investigations of stellar physics, particularly the study of bright emission line stars where line profile analysis of their often fast vary- ingspectracanbeperformed. Forinstance,usingastandard10inchtelescope,asignal-to-noiseratio (S/N) of about 100 can be achieved within 30minutes for a star of about 8 magnitudes in V and for a two pixel resolution of about 1A˚. Objects of the order of V =10mag and fainter are generally ex- cluded due to limited amateur telescope apertures, although with longer exposure times and/or lower S/N this limit can be extended to even fainter stars. Hence, amateur spectroscopists can fill specific 1www.shelyak.com 56 Figure 3: Typical amateur self-made spectrographs. Left: Device by Bernd Marquardt (Germany). Right: ThemaximumefficiencydevicebytheauthorandKlausVollmann(Germany). Figure4: Off-the-shelfstandardLittrowspectrographLHIRESIIIfromShelyak. gaps for detailed investigations. These are A) spectroscopic long-term campaigns monitoring line profiles for periods of the order of months or even years, B) surveys to support detailed observations bylargeorspace-basedtelescopesandC)monitoringofspecificspectroscopicparametersovermany years. 3.1 The long-term (cid:15) Aurigae campaign A prominent example of a long-term amateur campaign is the eclipsing binary (cid:15) Aurigae (F0Ia + companion)withanorbitalperiodofabout27years2. Therespectivecampaigngroup3 isinternation- ally acting for the 2009 - 2011 eclipse of the star system. A periodic campaign newsletter regularly highlights recent events. Hα time series, obtained by Christian Buil from his balcony in Marseille using a Shelyak Echelle spectrograph (Fig. 6) is shown in Fig. 7. Because of its long period of 27 years(cid:15)Aurigaeissimplyaprototypeobjectforamateurobservations,impossibletoperformbypro’s onsuchatimescale(seealsoR.Leadbeater,theseproceedings). 2http://www.threehillsobservatory.co.uk/epsaur spectra.htm 3http://www.hposoft.com/Campaign09.html 57 Figure 5: Two Echelle prototypes both with grating cross-dispersers designed by the amateurs Berthold Stober (left) and Tobias Feger (right). The final device will be mounted in a solid casing. Notethewoodenrack(left)foreasyandfastgeometricalimprovements. Figure6: Off-the-shelffiber-fedEchellewithprismcross-disperserfromShelyak. 3.2 The long-term Mons campaign The archetype of colliding-wind binary systems is the 7.9-year period and highly excentric WR+O binary system WR 140 (HD193793). Twenty-six amateurs and professionals from eight countries observed the prominent CIII wind line and its excess during periastron passage from Tenerife and from various home observatory in Europe to estimate the ephemeris of the system. All stations used the LHIRES III spectrograph. As part of this global campaign, Robin Leadbeater obtained spectra duringperiastronpassagefromhishomeobservatory(Fig.8). Figure8alsoshowshistwospectraof CIII/CIV before and during periastron passage obtained with his configuration. The inset shows the resultingexcessemissionduetothewind-windinteractionshockcone. 3.3 Surveys A ”classical” example for an astronomical survey, supported by amateur observers, has been the astrometric High Precision Parallax Collecting Satellite (Hipparcos), launched in 1989. Amateur astrometry has been performed for centuries and dedicated amateurs had already the respective ex- perience to obtain high precision data. As a result, many observers contributed their measurements to perform a successful satellite project. Such ProAm surveys are today possible in spectroscopy, as well. The presently most popular spectroscopic survey is the COROT Be Stars Survey4 project for the astroseismology satellite COROT (COnvection, ROtation and planetary Transits). A respective 4http://www.astrosurf.org/buil/corot/data.htm 58 Figure 7: Hα time series for the eclipsing binary (cid:15) Aur between July 21, 2009 and March 10, 2010 with 3-days increment. Celestron C11, Shelyak Echelle spectrograph, average spectral resolving powerR=11000. Figure 8: Left: The private Three Hills Observatory of Robin Leadbeater in Cumbria, England, consisting of a Vixen 20cm Cassegrain and an off-the-shelf LHIRES III Littrow slit spectrograph. Right: SpectralvariabilityofWR140withinsevenweeksobtainedwiththeleftinstrument. amateur COROT survey of bright stars (e.g., Be stars), as performed under professional supervision can help understanding spectral variability like non-radial pulsations or oscillations in the respective Be star disks. Example spectrA, obtained by a French amateur group around C. Buil, are shown in Figs.9and10. 3.4 Monitoring Themostproblematictaskforprofessionalspectroscopyisprobablyextremelylong-termmonitoring of specific spectral parameters. Only snapshots within relatively short time-scales are usually possi- ble, resulting in large time gaps. The true long-term description of the physical behaviour remains hidden. Delays in publishing results, sometimes for several years, do not match the regular needs of a pro. Continuous monitoring is not a priority in professional spectroscopy. This, however, is one of thecornerstonesofamateurworkusingsimplestandardprocedures(e.g.,equivalentwidthandradial velocity measurements) combined with well-known equipment and good routines. An example is showninFig.11fortheBestarδ Scorpii. ThisBestarbinarywithanorbitalperiodofabout11years isoneofthekeytargetsofamateurworkandfornumerousobservations. Thenextperiastronpassage will take place in July 2011 and is already in the focus of an extended ProAm campaign, including observationsfromTeideobservatory,asforWR140(seeSection3.2). 59 Figure9: HαamateurCOROTsurveyspectrumoftheV =6.14B9VestarHD194244,obtainedwith aCelestronC11andanLHIRESIIIspectrographwith2700sexposuretime. Figure10: HαamateurCOROTsurveyspectrumoftheV =7.65B5IIIestarHD171219. Instrumental setupasabove,but1800sexposuretime. 4 How to establish a ProAm campaign If the professional community wants to take advantage of amateur measurements one should keep some basic issues in focus. Instrumental knowledge and observational hands-on skills are already present in the amateur domain. On the other hand, scientific knowledge (e.g., physics, procedures, data interpretation) need to be contributed by those who have a complete university education in this field and already have the relevant experience. The professional community can not expect complete campaignproposalsfromamateurastronomersbutshouldfirsttaketheirspecificspectroscopicneeds to the amateurs and discuss them. For instance, the Mons campaign on WR 140 took only place because of a close contact between a professional scientist (Tony Moffat) and one of his previous students who is now active in the German amateur community. The COROT Be stars survey project is mainly driven by a professional group5 working closely together with amateurs in France6, Ger- many7 and elsewhere. Potential ProAm campaigns need some basic details. After an announcement in the respective communities it is essential to give information about the physical background and basic parameters (e.g., S/N, spectral resolution, etc.) to all interested observers. This is best done by a respective website. Unfortunately, there are only two well established communities of significant size, namely in France and Germany. In these two communities, respective discussion forums are available and it is recommended to use them for proper discussion. For the campaign management it 5http://www.ster.kuleuven.be/coralie/members.htm 6http://astrosurf.com/aras 7http://spektroskopie.fg-vds.de 60 Figure 11: Hα equivalent width measurements for the Be star δ Scorpii over about nine years. Note that the first measurements taken by professionals (blue circles) have been dramatically extended by agroupofamateurastronomers. is also recommended to separate science from administration issues. A highlight of each campaign is potential observing time at a professional observatory. Amateurs regularly do not have such ac- cess but are generally highly interested to go for it—often even at their own expense (if limited), as happened for the Mons campaign. Finally one should find some minimum financial resources (de- pendingontheobservatorysite)tocoverpotentialfinancialdeficits(higherequipmenttransportation costs,unforeseenevents,etc.). 5 Future plans and Summary In May 2010 most of the key players in the WR 140 MONS campaign organised a wrap-up meet- ing at Convento da Arra´bida8 close to Lisbon, of which these are the proceedings. The group, now called “ConVento”, will establish an informal website covering future ProAm campaigns, respective informationaboutspecificstellartargetsandamailinglist/discussionforum. Everyinterestedspec- troscopist and photometrist is invited to join the group. The link to this website will soon be found at www.stsci.de. Considering the present situation in astronomy it seems obvious that skilled and so- phisticated amateurs equipped with state-of-the art instrumentation in their domain, can successfully contribute their knowledge and enthusiasm to modern spectroscopic campaigns, either at their home observatoriesoratprofessionalsites. Theonlyobstacletomakingcontinuousobservationslikethose atprofessionalsitesisthelocalweatherandthefactthatamateurastronomerusuallyhavetoworkin their daily job. This however can be circumnavigated by joint campaigns, as shown above. It is up to theprofessionalcommunitytouncoverthisvaluabletreasure. Acknowledgements IthankTonyMoffat,ThierryMorelandGregorRauwfortheirlastingsupport. 8http://astrosurf.com/joseribeiro/e arrabida.htm 61 62