2012: The Year in Science
2012 was another good year for science generated by the international variable star community, and your efforts played a role in helping advance the science of variable star astronomy. The AAVSO as an organization continued to play a major role in providing access to amateur and professional data archives, along with providing new means to obtain observations (via AAVSOnet) and publish results (via the Journal of the AAVSO). While the AAVSO is a member organization headquartered in the United States, we are proud to have a truly global community of observers, and equally proud to partner with many other variable star organizations around the world including: the British Astronomical Association Variable Star Section (BAAVSS), Variable Stars South (VSS) and the Royal Astronomical Society of New Zealand, the L'Association Française des Observateurs d'Étoiles Variables (AFOEV), the Royal Astronomical Society of Canada (RASC), and others. All of us at headquarters are gratified that so many of our colleagues in international organizations choose to be members and observers of the AAVSO as well as their own national organizations.
In calendar 2012, at least 90 publications appeared in print using the data archives of the AAVSO, resources like the AAVSOnet telsecope network, or AAVSO-hosted projects, or which involved direct participation by observers of the AAVSO community. It's difficult to estimate, but the true number of papers using data from the AAVSO archive is likely higher, as this total only includes papers submitted to arXiv.org containing the word "AAVSO" in a searchable way, or papers communicated directly to AAVSO staff and included in our AAVSO in Print feature.
In the short article below, I'll highlight just some of the items in the astronomical literature from 2012 that utilized amateur data or included members of the AAVSO among their authors.
Clusters, cluster studies, and new surveys
Databases created and hosted by the AAVSO played a role in a number of papers during the past year, with both the APASS and VSX databases being used. APASS itself was one of the catalog inputs for the recently released UCAC-4 catalog, the long-awaited successor to the US Naval Observatory's UCAC-3. APASS provided photometry for UCAC-4, giving this important catalog an important photometric component to go along with its astrometry. APASS photometry -- as served through our website, or provided by staff -- provided important assistance to a number of galactic surveys, for example Glushkova et al, Turner et al., and Casetti-Dinescu et al.
VSX, the volunteer-created and led Variable Star Index, is also becoming an increasingly important source of information for the research community. The VSX catalog was a key starting point for several survey papers including Anderson et al., Zejda et al., and Fruth et al., and authors are increasingly finding that the amateur-led community is actively finding new variable stars long before the professional community does. VSX not only provides a record of discovery for these stars, but can also help the professional community understand their own data, and even calibrate their variable star detection algorithms. As always, VSX remains a volunteer-led effort, and the participants in VSX efforts deserve the thanks of the greater astronomical community, amateur and professional alike.
RR Lyrae and Cepheids
There were a handful of papers dealing with RR Lyrae and Cepheid variables, both fundamental calibrators of the distance ladder. Majaess et al. (including AAVSO Councillor David Turner) published two papers on these stars, one on each of Cepheids (zeta Gem) and RR Lyrae stars (in clusters); both of these studies used AAVSOnet telescopes for data collection. Sipahi et al used data held in the International Database to perform a study of the Anomalous Cepheid TYC 1031-1262-1 (aka ASAS J182611+1212.6), which is a cepheid and an eclipsing binary. Their work put good constraints on both the masses and radii of these stars, making this system potentially useful for calibrating structural models of Cepheids.
Finally, there were three data-intensive papers by the RR Lyrae community, two of which (both by de Ponthierre et al. [1,2]) were led by the amateur community, and a third (Le Borgne et al.) which featured substantial contributions by the worldwide amateur community. The Blazhko effect remains an important topic of research in RR Lyrae studies. Data sources like the Kepler satellite have provided new insights into the Blazhko phenomenon, but intensive ground-based studies still have an important role to play, and the field is a productive one for the CCD community.
Long-Period EBs: epsilon Aurigae, EE Cep, and (maybe?) V383 Sco
The eclipses are over for now, but both epsilon Aurigae and EE Cephei are still producing interesting papers from their recent eclipses. Epsilon Aurigae's nature is still in question, but new and old data will continue to clarify the picture. Hoard et al analyzed a multiwavelength dataset including optical data from the AAVSO along with Herschel infrared data to better constrain the properties of the eclipsing body, while Mauclaire et al and Leadbeater et al highlighted some of the spectroscopic results from the recent eclipse. Galan et al published two papers in 2012 on two other interesting long-period eclipsers, EE Cep, and V383 Sco. EE Cep was shown to be a similar system to epsilon Aurigae, while V383 Sco is (probably) a system in a similar state as the two better-known stars. Interestingly, the paper on V383 Sco doesn't involve data for this specific star, but instead used the more extensive data archive for other Mira and semiregular variables to help develop a model for color dependence of variations in V- and I-bands.
Cataclysmic variables of diverse types remain one of the most-requested targets of amateur observations by the research community, and no fewer than 32 publications on cataclysmics, symbiotic stars, and novae appeared in print during calendar 2012 written by or based upon the observations of the amateur community. What is particularly exciting about many of these papers is that the observers themselves are fully involved as coauthors in the work, and share credit with the leaders in the projects. In some cases, the papers and projects are themselves led by members of the amateur community, highlighting the impact that the amateur community can have in this field. Cataclysmics are rich targets for new observations, as many interesting problems in accretion astrophysics and binary star evolution can be approached using short-term but intensive campaigns of photometry; good science can often result from just a few seasons of intensive time-series coverage, and groups such as the Center for Backyard Astrophysics and VSNET have been pushing the boundaries of what groups of dedicated observer communities can do. Along with new observations, new information is also being gained by looking at long-term observations available from the AAVSO archives, and combining archival and new photometry with ground- and space-based multiwavelength observations.
There are too many papers to list individually, but there are plenty of highlights. The amateur community both participated in and led a number of targeted campaigns, for example the Shears et al. collaborations on SDSS J0932 and PU UMa to pin down their orbital and superhump periods. Another great project was a study of SW Sex stars by BAA President David Boyd, published in JAAVSO this year, showing period evolution in some stars that's contrary to previous understanding. Amateurs also continue to make critical contributions to professional-led research programs. One of the great highlights of the year was the Center for Backyard Astrophysics (CBA) study of BK Lyncis, recently transitioned from novalike variable to outbursting dwarf nova. Based on amateur-generated time-series of the star, the physics of the accretion disk and the overall system have been revealed, and BK Lyn is now believed to be an old post-nova; Patterson et al put forward the interesting hypothesis that the amount of time since the last nova eruption is a key "second parameter" in the evolution of cataclysmic variables.
Amateurs have been participants in several Hubble Space Telescope campaigns, giving satellite operators the all-clear to observe important CVs. This year the global amateur community have been assisting with a number of similar campaigns, and one of these from several years ago -- on the WZ Sge star GW Librae -- is now in print. As campaigns continue, the research community increasingly depends upon the resources and efforts of the amateur observational community, and it looks to be an increasingly valuable partnership.
Along with new observations, historical observations also often supplement multiwavelength research, and several additional papers making multiwavelength studies of CVs appears in 2012, including: Harrison et al (infrared observations with Herschel), Orio (X-ray observations), Godon et al (ultraviolet observations with FUSE), Evans and Gehrz (more infrared observations), Ashish et al. (nova observations in radio waves), Beuermann et al (X-ray observations of AM Her), and more. Such studies highlight an important fact about your observations, namely that they may be used well into the future for purposes we don't know yet.
Young Stellar Objects
The amateur community has increased its participation in YSO research with a new observing section and renewed focus on these interesting stars. Several studies of both recent and historical data sets of YSOs were published in 2012, including HBC 722/V2492 Cyg (Green et al.; Dunham et al), EX Lupi (Teets et al.; Sicilia-Aguilar et al), and GM Cep (Chen et al.). The Green et al paper on HBC 722 used recent observations to develop new models for the behavior of the accretion flow onto this protostar, while the Dunham paper were looking *around* the variable at millimeter wavelengths, finding several new obscured protostars nearby, but not the variable itself (which is itself an interesting result -- putting upper limits on the strength of the mass of HBC 722's accretion disk.) The Teets et al. paper on EX Lupi used both optical and X-ray data to tie changes in brightness to variations in mass accretion rate onto the protostar. Sicilia-Aguilar et al found a similar result, using both optical photometry and spectroscopy to tie EX Lupi's 2008 outburst to variation in the mass accretion rate. Like CV research, multiwavelength observations that include optical data from the amateur community are becoming the norm, and we're learning new things about YSOs -- both their environments and the details of how and why they vary -- as a result. We have observing campaigns (both professional- and amateur-led) that are currently active, and we look forward to seeing more in print about YSOs in 2013.
Long Period Variables and other evolved stars
Historically, the LPVs have been the most- and longest-observed stars by the amateur community, and archival data for these objects continues to provide important information for researchers. As with CVs, we can learn a great deal about long period variables and other evolved objects through multiwavelength observations. The long-term optical light curves of LPVs have provided reference data for several papers in 2012. As an example, Mayer et al used these data to phase infrared observations by the Herschel satellite in their study of AGB star environments and their mass loss; Smolders et al used Spitzer to obtain infrared spectra of S-type stars, and also used light curves from the AAVSO for optical comparison.
Another important field in AGB star research is interferometry at radio, infrared and optical wavelengths. Interferometry makes it possible to image these stars -- not just measure the overall brightness, but take a picture of the star -- and a number of papers made use of amateur data from the AAVSO archives to obtain pulsational information about these objects. What's especially exciting is that targets for interferometry are bright stars -- exactly the ones that the amateur community have been observing for so long! Examples of interferometric studies include Hillen et al (observing with Palomar Testbed Interferometer), Barnaby et al (using an aperture mask on the 8-meter VLT), Richards et al (observing water masers with the MERLIN array), and both Paladini et al and Zhao-Geisler et al. (using MIDI on the VLT Interferometer).
Finally, I'll include one special class of evolved stars in with this bunch: the R Coronae Borealis stars. These objects remain exciting targets for both the amateur and professional communities, not only for their dramatic variations, but because they're slowly revealing more information about the end stages of stellar evolution. One paper by Jeffers et al used a variety of data -- polarimetry from ExPo at the Isaac Newton Telescope, imaging with HST, and archival light curves -- to physically understand the cloud around R Coronae Borealis during its dramatic fade of the past several years. Another was by Kameswara Rao et al. on DY Cen, using long-term light curves to better understand long-term variability. Their paper highlights the very interesting result that DY Cen is currently the only known proven binary star among the RCB class. In addition to those two papers, I'm also very happy to highlight the review of R Coronae Borealis stars by Geoff Clayton and published in the Journal of the AAVSO. He provided important background on these stars, along with motivations for both new and continuing observations. It's good reading for anyone interested in learning more about these stars and why they're worth your time and observations.
The number and diversity of publications generated from amateur data is an important metric of the community's impact on science. If you want an even more comprehensive picture of the science generated by the AAVSO community during 2012, I urge you to visit our AAVSO in Print page and see for yourself the great science being done by, and with the help of, the amateur variable star observer community. However I think one can take a few things away from this broad overview.
One is that your observations are being used in very diverse ways, and ground-based photometry is being effectively paired with any number of other data sets and research strategies. Two, I think the current topics of interest show value in both long-term monitoring of variables and intensive, short-term campaigns. There's no fixed strategy for what observations are necessarily most productive, but in general the papers utilizing archival data seem to concentrate on objects with long-term variations -- the Miras, semiregulars, R CrB stars, and others. Objects with very short-term variations -- cataclysmics and YSOs -- are a mix, but short-term, focused and intensive campaigns are providing interesting new results. I would argue that both are valuable approaches for observers to take, and which you try is more a matter of personal preference as much as scientific result. Lastly, there are a number of papers producing very interesting astrophysics from very bright stars -- brighter than V=12, and often much brighter. This is increasingly the realm solely of the amateur and small college community as major national and international observatories focus attention (and budgets) on very large telescopes. We're now in an era where even 4-meter telescopes are considered "small", which leaves an extraordinary array of targets unobserved -- and unobservable -- by major instruments. There are valid scientific reasons for the larger research community to push the boundaries of the field with powerful instrumentation, but definitely be aware there's an awful lot of astronomy and astrophysics left to learn, precisely where your instruments are most powerful. I think the research community will become increasingly reliant on the international amateur community in the years to come, and there's also room for researchers within the amateur community to define their own projects and answer interesting questions.
I look forward to seeing more great science in print in the year to come, and we're already actively adding to AAVSO in Print in just the first month of the year. There are any number of ways you can participate in science, and I hope you take every opportunity to do so. Your only limitations are your imagination and clouds, and I wish you very clear skies in 2013!