From jop at astro.columbia.edu Fri Nov 3 04:08:02 2006 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 3 Nov 2006 04:08:02 -0500 (EST) Subject: (cba:news) tonight's SWIFT observation of "Var Cas 06" Message-ID: Dear CBAers, We managed to obtain a target-of-opportunity SWIFT X-ray observation of the new transient in Cas (0009+54), scheduled for 1330 UT today. It would be great if optical time series were obtained very close to it! Sorry for the short notice, but we were approved just 4 hours ago. Tomorrow night would be really good too. This could be an awfully interesting object. So far it looks pretty unique - not quite looking like any of the usual suspects... joe From jop at astro.columbia.edu Fri Nov 3 04:38:56 2006 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 3 Nov 2006 04:38:56 -0500 (EST) Subject: (cba:news) coords for the Cas transient Message-ID: along with a brief description of our TOO proposal... > > We propose to obtain a short X-ray observation of the recently > discovered outbursting star in Cassiopeia ("Var Cas 2006"). The > quiescent counterpart appears to be a distant (1 Kpc) B star, and the > 4 magnitude outburst is by far the largest ever seen in such a star. > This could be the signature of an accreting compact star in a close binary, > or it could be an extremely violent ejection of a shell by the B star > which has oddly failed to show emission lines at any time in its > history. The first scenario would produce a strong hard X-ray source > -- probably >0.5 UFU -- while the second would produce only soft X-rays > or none at all. A short observation with Swift would easily distinguish > between these. > > Exact 2000 coords: 00 09 21.98 from Tycho-2 astrometry > +54 39 43.9 > > V= 7.4 in outburst Oct 30, =9.5 on Nov 2, probably 11.6 by about Nov. 9. > From jop at astro.columbia.edu Fri Nov 3 04:41:17 2006 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 3 Nov 2006 04:41:17 -0500 (EST) Subject: (cba:news) CBET 711: 20061031 : BRIGHT VARIABLE STAR IN CASSIOPEIA (fwd) Message-ID: and here's the IAU circular... Subject: CBET 711: 20061031 : BRIGHT VARIABLE STAR IN CASSIOPEIA Electronic Telegram No. 711 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS at CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) CBAT at CFA.HARVARD.EDU (science) URL http://cfa-www.harvard.edu/iau/cbat.html BRIGHT VARIABLE STAR IN CASSIOPEIA S. Nakano, Sumoto, Japan, reports the discovery by Akihiko Tago (Ayabe, Tsuyama, Okayama-ken, Japan) of a brightening star on 30-s CCD frames taken with a 70-mm f/3.2 lens and a Canon EOS 20Da digital camera (limiting magnitude 12), with the following magnitudes available: Oct. 25.538 UT, 10.7; 27.409, 10.5; 30.411, 8.8; 31.469, 7.5. Tago adds that a star of mag 11.8 (which did not vary on past images) is located very close to the new variable's position, for which he identifies GSC 3656.1328 with R.A.= 0h09m21s.81, Decl.= +54o39'43".8, equinox 2000.0); apparently this is the same star listed in the USNO-A2 catalogue as 1425.00229853, having position end figures 22s.00, 44".0, with blue mag 11.9 and red mag 11.3. NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2006 CBAT 2006 October 31 (CBET 711) Daniel W. E. Green From jop at astro.columbia.edu Sun Nov 5 05:24:53 2006 From: jop at astro.columbia.edu (Joe Patterson) Date: Sun, 5 Nov 2006 05:24:53 -0500 (EST) Subject: (cba:news) More on Var Cas 06 Message-ID: Dear CBAers, Keep after the bright new star in Cas! We're pressing ahead with it on every front we can: X-ray, UV, spectroscopy, calibrated photometry, and time-series photometry. For northerners, it's now a perfect target up there in Cas, successfully shrugging off the challenges of the full Moon. The nature of the star seems quite mysterious... a garden-variety A star jumps 4 magnitudes, and still looks like a garden-variety A star! Message on other stars later today... joe BTW a V filter would be a nice choice for a time series. B would be pretty good too. From jop at astro.columbia.edu Wed Nov 8 01:28:10 2006 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 8 Nov 2006 01:28:10 -0500 (EST) Subject: (cba:news) Var Cas 06 - keep going! Message-ID: Dear CBAers, The new variable in Cas continues to tantalize, and it looks pretty promising for an interpretation as a nearby microlens. Continued coverage is essential! Please let me know if I can help with charts, etc. Over the next 7-14 days the photometry will go a long way towards testing this fascinating hypothesis! The variable is GSC 3656-1328, and the comparison I recommend is GSC 3656-1399. V-band would be best, but I can use a different band - and also unfiltered if you don't have filters. Any more European data coming? I have one night from Arto - anything else in the pipeline? joe From jop at astro.columbia.edu Wed Nov 8 10:22:18 2006 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 8 Nov 2006 10:22:18 -0500 (EST) Subject: (cba:news) var cas 06 again... Message-ID: Dear CBAers, I just wanted to scho Tom's remarks. Over the next 1-3 weeks, we want to track this thing down to minimum light, and beyond. Even a short run, or a snapshot, is fine if it's decently calibrated. Best is a V filter, preferably with GSC 3656-1399 as a comparison. A different comparison star is OK, and unfiltered is OK too, as long as you clearly specify what comp you used. Whether the star's light curve ever wiggles, we dunno (so far no) - but how it returns to minimum may well provide a nice test for a microlens hypothesis. Of course, any earlier data would be mighty nice too! joe From jop at astro.columbia.edu Wed Nov 8 20:50:57 2006 From: jop at astro.columbia.edu (Joe Patterson) Date: Wed, 8 Nov 2006 20:50:57 -0500 (EST) Subject: (cba:news) EG Aqr and Var Cas 06 Message-ID: Dear CBAers, Rod Stubbings reports that EG Aqr has jumped into outburst, the first in a few decades perhaps... and Gianluca Masi reports superhumps! Our kind of star, equatorial, and at a decent time of year. Let's fire away on this star! And Var Cas, well, I've bent your ear enough on it. It's also known as GSC 3656-1328, and 3656-1399... which would make a fine comp star. joe From jop at astro.columbia.edu Fri Nov 10 14:15:12 2006 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 10 Nov 2006 14:15:12 -0500 (EST) Subject: (cba:news) IAU Telegram on EG Aqr Message-ID: Here's the notice - fire away, looks like a piece of red meat to CBAers! joe ---------- Forwarded message ---------- Date: Fri, 10 Nov 2006 13:43:07 -0500 (EST) From: IAUC mailing list To: iauc at libraries.cul.columbia.edu Subject: CBET 734: 20061110 : EG AQUARII Electronic Telegram No. 734 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS at CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) CBAT at CFA.HARVARD.EDU (science) URL http://cfa-www.harvard.edu/iau/cbat.html EG AQUARII E. O. Waagen, AAVSO, writes that this dwarf nova was reported in outburst by R. Stubbings (Tetoora Road, Victoria, Australia) at visual magnitude 12.4 on Nov. 8.48 UT, confirmed by H. Maehara (Japan) via CCD at V = 13.08 on Nov. 8.630. This outburst is only the third known outburst from this variable (R.A. = 23h25m19s.17, Decl. = -8o18'18.9, equinox 2000.0, from USNO-B1.0; minimum photographic magnitude around 18.5) to have been observed. Previous outbursts of EG Aqr occurred in October- November 1958 (only two known photographic magnitudes, 14.8 and 14.0) and August 1959 (photographic magnitudes 14.0, 17.2, and additional values as it declined back toward minimum). CCD observations now by several observers -- including T. Vanmunster (Belgium), T. Krajci (USA), D. Wells (USA), P. De Ponthiere (Belgium), H. Hautecler (Belgium), L. Monard (South Africa), and S. Dvorak (USA) -- clearly show superhumps, indicating that EG Aqr is a SU UMa-type dwarf nova; data collected as the superoutburst progresses are being analyzed to determine the superhump behavior and refine the variable classification. All CCD observations reported to the AAVSO may be found on the AAVSO website (www.aavso.org). Charts and photometric sequence information are available through the AAVSO website, as announced by A. Henden in AAVSO Special Notice 24. Additional visual magnitude estimates reported to the AAVSO: Oct. 28.541 UT, [15.6 (Stubbings); Nov. 8.532, 12.5 (Stubbings); 8.934, 13.1 (G. Poyner, Birmingham, England); 9.437, 12.7 (Stubbings); 9.726, 12.9 (W. Kriebel, Schierling/Walkenstetten, Germany); 9.794, 12.8 (H. Hautecler, Boutersem, Belgium); 9.802, 12.7 (P. Schmeer, Bischmisheim, Germany); 9.880, 12.9 (Poyner); 10.448, 12.9 (Stubbings); 10.490, 12.7 (Stubbings); 10.524, 12.7 (Stubbings). CCD magnitudes, unfiltered unless otherwise noted, contributed to the AAVSO: Oct. 31.174, R = [16.5 (Schmeer); Nov. 8.326, R = 12.7 (Schmeer); 9.047, 13.4 (T. Krajci, Cloudcroft, NM); 9.0496, V = 13.31 (D. Wells, Missouri City, TX); 9.287, 13.1 (Krajci); 9.762, 12.9 (P. De Ponthiere, Lesve, Belgium); 9.801, 13.2 (De Ponthiere); 10.289, 13.2 (Krajci). NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2006 CBAT 2006 November 10 (CBET 734) Daniel W. E. Green _______________________________________________ iauc mailing list iauc at astro.columbia.edu https://mail.astro.columbia.edu/mailman/listinfo/iauc From jop at astro.columbia.edu Sun Nov 12 22:25:10 2006 From: jop at astro.columbia.edu (Joe Patterson) Date: Sun, 12 Nov 2006 22:25:10 -0500 Subject: (cba:news) Var Cas 06, he liveth Message-ID: <4557E596.5010200@astro.columbia.edu> Dear CBAers, Don't forget ol' Var Cas 06 = GSC 3656-1328 (w/3656-1399 as comp star). We've been studying that star as an excellent candidate for microlensing (ATel should be coming out tomorrow). The event is not quite over yet, and the rate of return to normal will be a significant constraint in judging whether the microlensing interpretation holds up. So follow that star! I realize the apparently constant light level will not impress the neighbors, or yourself either... but this is a sturdy investment! V filter would be nice, but we can definitely use unfiltered as well. Tom, I've been putting all of the data on your instrumental delta-mag scale, since you have the bulk of the data. This means that your runs are especially critical, since the delta-mags don't need any conversion. I hope you can spare some more time for little VarCas! joe From jop at astro.columbia.edu Mon Nov 13 06:17:27 2006 From: jop at astro.columbia.edu (Joe Patterson) Date: Mon, 13 Nov 2006 06:17:27 -0500 Subject: (cba:news) Var Cas 06, one more time - not yet a done deal! Message-ID: <45585447.5070703@astro.columbia.edu> Dear CBAers, Anticipating your disappointment at seeing such a flat light curve, I forward to try to keep motivation high! The only caveat is that you should not extend observations beyond about 1.8 airmasses - beyond which, differential extinction sort of kills. (Very different from our usual targets, since we normally remove slow trends in searching for periodic effects) We've invested a lot in GSC 3656-1399 as a comp now, so that really needs to be the one. Careful about saturation... joe ------------------------------------------------------------------------------ ------------------------------------------------------------------------------ The Astronomer's Telegram http://www.astronomerstelegram.org ------------------------------------------------------------------------------ Posted: Fri Nov 10 01:30:02 EST 2006 -- Mon Nov 13 01:30:00 EST 2006 ============================================================================== ATEL #942 ATEL #942 Title: VAR CAS 2006, A Nearby Microlens? Author: D. Spiegel et al. (Columbia U.) Queries: jop at astro.columbia.edu Posted: 12 Nov 2006; 19:55 UT Subjects: Optical, X-ray, Microlensing Events, Transients, Variables, Stars D. Spiegel, J. Patterson, E. Gotthelf, J. Sokoloski, N. Zimmerman, N. Mirabal, Columbia U.; T. Krajci, CBA-New Mexico, R. Koff, CBA-Colorado; P. de Ponthiere, CBA-Lesve; A. Oksanen, CBA-Finland; S. Dong, S. Gaudi, L. Watson, Ohio State U.; R. Remillard, MIT Kavli Institute for Space Research. Time-series photometry of the new transient in Cassiopeia (GSC 3656-1328, see CBET #711) during November 1-10 with the telescopes of the Center for Backyard Astrophysics (CBA) reveals no variability other than the timescale of overall decay. Snapshot BVRI magnitudes show no discernible change in color, and continued spectral coverage is consistent with the A-star description given by Munari et al. (CBET #718), with no emission components. Study of the RXTE All-Sky-Monitor database shows no detections over the 10-year lifetime of RXTE, and a 5000 s observation with SWIFT on November 3 shows no 0.5-10 Kev flux to a limit of 10**-12 ergs cm-2 s-1. These observations are difficult to reconcile with any of the easy-to-imagine theories for the transient's origin: a dwarf nova, an X-ray transient, an erupting shell star. But the properties and light curve can be acceptably fit by a microlens interpretation (see also ATEL #931), despite the very low optical depth to microlensing for such a nearby star (1 Kpc). This may provide an opportunity to study a nearby microlens, with observable effects from parallax. Continued photometric and spectroscopic observation is vital to severely test this idea. Archival searches of this region during the pre-maximum phase (October 18-31) are especially critical, as the existing data are sparse. Since the transient appears to have reached V=7.5, even images from very small cameras may be quite helpful. Of course, any evidence that GSC 3656-1328 is an intrinsic variable star is even more crucial! ------------------------------------------------------------------------------ Password Certification: Joseph Patterson (jop at astro.columbia.edu) http://www.astronomerstelegram.org/?read=942 ============================================================================== Your keywords: Radio, Millimeter, Sub-Millimeter, Far-Infra-Red, Infra-Red, Optical, Ultra-Violet, X-ray, Gamma Ray, >GeV, Request for Observations, A Comment, AGN, Asteroids, Binaries, Black Holes, Comets, Cosmic Rays, Cataclysmic Variables, Globular Clusters, Gamma-Ray Bursts, Meteors, Microlensing Events, Neutron Stars, Novae, Planets, Planets (minor), Pulsars, Quasars, Soft Gamma-ray Repeaters, Solar System Objects, The Sun, Supernovae, Supernova Remnants, Transients, Variables, Stars ============================================================================== This is an automatically-generated notice. If you'd like to be removed from the mailing list, please visit the The Astronomer's Telegram at http://www.astronomerstelegram.org . From jop at astro.columbia.edu Tue Nov 21 23:00:27 2006 From: jop at astro.columbia.edu (Joe Patterson) Date: Tue, 21 Nov 2006 23:00:27 -0500 (EST) Subject: (cba:news) november stars Message-ID: Dear CBAers, I attach a short semi-popular paper I just finished on the new variable in Cassiopeia (Var Cas 06, as it is currently known). It was a big CBA effort, with contributions from Arto Oksanen, Pierre de Ponthiere, David Boyd, Dave Messier, Donn Starkey, and Carole Haswell (along with several students from the Open University)... but the principal data (certainly in the CBA, and I think in the world also) were from Tom Krajci and Bob Koff. Their precise data on the very first night after the announcement was the critical element in certifying the microlens fit. So... you can read about it. I'm pretty sure it's the first such event in history: a high-magnification event for a nearby star. I'll put up the figures on the website in a couple days. Time for new favorite stars! I've been waiting for November, to promote two fascinating stars now transiting near local midnight. RX0354-16 is a strange novalike variable with an enormous proper motion... a very tempting target, as it is likely to teach us something new about the local population of CVs. Porb is still unknown, and there is some indication it might be as low as 40 minutes. The magnitude is listed as 16.0-18.4 ("Eri" in the Downes et al. catalog), although actual dwarf-nova eruptions are probably not present. A great southern - and marginally equatorial - object if you can handle the faintness! Likewise for SDSS0407-06, also "Eri" in Downes et al. Alon Retter and Alex Liu wrote a nice paper on this star last year. Our coverage verified the many periods they found, and I expect this star to be so rich in periodic content that it will be a prime target for two months or more. Stated as 15-17, and probably a dwarf nova. Good target regardless of brightness. There's a new eruptive object in Leo, too,and Tom's photometry suggests an 80 minute period. I'm going to wait another day or two before signing on to this one, though. Northern-only targets. RX0636+35 ("Aur") is a shiny new DQ Her star, about 15.8 and a likely collection of strict periods. Very nice target, and new to us. Also an old friend: V405 Aur, another DQ Her star and a great target for lousy conditions. Most of the other targets from last month can be retired. Exceptions are certainly AO Psc and FO Aqr: 1-3 hour observations of these stars in the evening sky continue to be quite useful. Happy observing! Please let me, and all of us, know what you find in these various new targets... joe -------------- next part -------------- THE HALLOWEEN TRANSIENT OF 2006: A NEARBY MICROLENS? On 31 October 2006, the IAU's Bureau of Astronomical Telegrams sent out a strange announcement: an 11th magnitude star in Cassiopeia had suddenly jumped to 7th magnitude. I remember feeling a bit skeptical; I knew Dan Green was not generally fond of pranks... but it *was* Halloween... and his office *was* known as the BATroom... and I remembered a past announcement of Santa's reindeer. Still, the e-mailed telegram was not quite strange enough for a good prank; and the discovery was credited to Akihiko Tago, one of the world's most famous discoverers of comets and novae. Then a second IAU email a few hours later provided further details, and confirmation: GSC 3656-1328 had really erupted. All over the world, programs of visual and photographic observation began, with results shard through internet news-groups. Two members of the Center for Backyard Astrophysics network (Bob Koff and Tom Krajci) immediately started time-series photometry of the transient. Their light curves showed a blue star at V=8.9 and fading rapidly at 1.5 magnitudes per day. Initially, the greatest oddity was the apparent association with a seemingly normal A star; this did not seem to resemble any known class of variable star. The oddities quickly grew. On 3 November, we had a busy day. 1. We obtained a target-of-opportunity X-ray observation with SWIFT, which showed no detectable flux. 2. Our colleague Ron Remillard (MIT) searched the RXTE All-Sky Monitor data for any sign of an X-ray transient; there was no detectable signal on the days of outburst, nor on any other timescale over the mission's 10-year baseline. 3. We studied available data on the color of the outburst light. To within 0.05 mag, the outburst had the same color as the A star in quiescence (B-V=0.20). 4. We received a fascinating new telegram (CBET 718) which deepened the mystery. The spectra reported by Ulisse Munari (Padova Observatory) indicated a fairly normal A-star spectrum as early as November 1.1, with no emission components and no evidence of rapid rotation. And a search by Sergei Antipin (Sternberg Astronomical Institute) of 400 photographic plates during 1964-94 revealed no variation from a mean mpg=11.8, the same brightness seen in modern surveys (Tycho, USNO, TASS, etc.) By the end of November 3, all the easy-to-imagine theories for the outburst (prank, X-ray transient, cataclysmic variable, rapidly rotating shell star) appeared to be ruled out. A constant star had jumped 4 magnitudes in a week, and now was returning to normalcy in another week. No X-rays, no flickering, no evident change in color or spectrum. Amazing. Stellar zoology didn't seem to have a place for this event. Actually, there is a place; it just has a very low *a priori* likelihood. Add 10 magnitudes, and this would describe a common microlensing event in the Magellanic Clouds. And the assembled light curve was looking cuspy and symmetric, the characteristic shape of microlensing events. The words were first pronounced in print by Maciej Mikolajewski (Nicolaus Copernicus University). Although a microlens is a mere accident of geometry, it's a new toy in astrophysics; and as every parent (or dog-owner) knows, new toys are vastly more interesting than the old ones. By November 4, hundreds of astronomers were discussing this in seminars, corridors, and internet groups. More variable-star observers took notice, and the star's fade to quiescence was thoroughly covered. Calls went out for images of Cassiopeia during the sparsely covered rise and maximum, and digital photos were retrieved by British amateurs Keith Geary and Mike Collins. Careful analysis of Geary's image by Michael Richmond (Rochester Institute of Technology) showed how these unfiltered images from short-focus lenses in crowded star fields could yield calibrated magnitudes. And most importantly, images were found in the test runs of the new northern station of the All-Sky Automated Survey (ASAS) at Haleakala, Hawaii. ASAS is an automated array of telephoto lenses which image the entire visible sky every night through V and I filters. The images flow through an analysis pipeline and produce beautiful long-term light curves of variable stars. A collaboration between Bohdan Paczynski (Princeton) and Grzegorz Pojmanski (University of Warsaw), ASAS-South has been in operation at Las Campanas Observatory in Chile since 2000, and has become a spectacularly useful tool. In 2006, a northern station began test runs at Haleakala. Pojmanski, the modern virtuoso of variable-star research, quickly retrieved and analyzed many images of the star for us, with 5 covering rise and maximum light. These were especially critical, since they yielded calibrated magnitudes through standard filters. Our discussions with microlens experts at Ohio State (Subo Dong, Scott Gaudi, Andy Gould) and Notre Dame (Dave Bennett) taught us the importance of finding data acquired during the rise and maximum. A foreground unseen star or planet crossing the line of sight to a distant star should produce a *symmetrical* disturbance in the image due to microlensing. The light curve has to be achromatic, symmetric, and follow a specific mathematical shape. This is a very exacting requirement. After Dong's careful splicing of early magnitudes from small cameras, the ASAS magnitudes, and the extensively observed decline portions, it was evident that the entire light curve really did conform in detail to the prediction based on microlensing. The accompanying figure shows excellent agreement with the theory: at about 2200 UT on Halloween (local midnight in Transylvania), an unknown massive object apparently crossed in front of GSC 3656-1328. In a microlens event, a foreground star has to accidentally cross within ~20 microarcseconds of the source star. This is extremely rare ("one in a million per year"), and therefore searches concentrate on regions where there are many thousands of source stars (other galaxies), or lines of sight containing thousands of potential lensing stars (near the plane of the Milky Way). The "optical depth" to microlensing increases as the square of the distance, so all known microlensing events are very distant. That's why all microlensed stars are quite faint, and why this event was so surprising. Dave Bennett estimated that an event like this -- high-magnification microlensing of a bright star -- should be seen from Earth only once per 30 years, and even that rate assumes that we never miss any. Is it reasonable to associate this brightening with such an unlikely event? Perhaps. First, since the set of all possible unlikely events is infinite, individual unlikely events happen frequently! Second, it's worth noting who made the discovery: a man who has been sweeping the sky for novae and comets, and finding them, for... well, for 40 years (his first discovery was in 1968). No other event like this has been seen by Tago, or by anyone else. So maybe one per 30 years is about right. But this estimate is for high-magnification microlensing of bright stars. Slightly fainter stars (say V=13) are much more numerous, and lower-magnification events are more likely since they do not require very close approaches to the line of sight. So a targeted all-sky search for such events with wide-field cameras might indeed find a decent supply. And this is an exciting prospect, because the accident of microlensing enables us to discover fine details of invisible stars (the lenses), including planets, even Earth-mass planets. So powerful a diagnostic exists because the lens passes within ~1 AU of the line of sight, offering a transient opportunity to scan the lens's gravity field at planetary distances. About a dozen planets have been discovered with this technique, all in fields well-monitored by the established microlens search programs (Galactic bulge, LMC, etc.). The Halloween transient lures us with the prospect of learning more by extending this to the entire sky. So... did the lensing star on Halloween have planets? We don't know - we managed to obtain enough light curve to certify the lens, but not the nearly continuous coverage needed to see the small deviations from symmetry that are the signature of planets. We just weren't ready this time. But there will be a next time. And it is likely that the heroes of next time will be mainly amateur astronomers, who are globally distributed and can pounce quickly on newly discovered transients, obtaining the critical data in the narrow window around maximum light. Even in the present case, when hundreds of professional astronomers were excited by the event, the main heroes were amateurs (Tago, Krajci, Koff; and the many astronomers sending observations to internet news-groups). While I was writing this paper, Andy Gould told me a fascinating story about the involvement of an amateur scientist in the *theory* of microlensing. Einstein wrote his famous theory paper in 1936, where he calculated that such a stellar event would probably never be observed. There is evidence he worked out the theory in 1912, and then set it aside as of little interest. The Hungarian engineer Mandl pestered Einstein about it, even travelling to Princeton when Einstein didn't answer his mail. Eventually Einstein gave in and published the result in 1936... and then wrote a followup letter to the editor of *Science* saying that the result, which "Mister Mandl squeezed out of me", was useless but publishing it was good because "it makes the poor guy happy". Other professional astronomers remained similarly myopic, until Paczynski's famous revival of the subject in 1986. Finally, do we know with certainty that the Halloween transient was a microlensing event? No; the case seems very strong, but certainty is too lofty a standard. I think we can say this: the event signifies either a microlens, or something even more exotic: a unique variable star that manages to mimick a microlensing light curve in fine detail, and not offer any of the credentials of known variables. Search programs in the LMC have monitored nightly millions of A stars, and never found a light curve like this -- or more correctly, "everything that *looked* like a a microlens *was* a microlens" (Dave Bennett). Both hypotheses are worth exploring; but Ockham's Razor now seems to strongly favor interpretation of the transient as a spectacular microlensing event, which may kick off a new chapter in the history of professional-amateur collaboration. From jop at astro.columbia.edu Thu Nov 23 14:21:48 2006 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 23 Nov 2006 14:21:48 -0500 (EST) Subject: (cba:news) november stars, redux Message-ID: Dear CBAers, Despite my cheerleading for RX0354-16 a few days ago, I no longer think it's a winner. Berto's and Tom's data suggest that it's too hard (faint) a target, and some other data lying around a corner suggested that it might not be so unusual - except for the one circumstance of high space velocity, which is not exactly up our alley. So I'm hooting it off the stage. SDSS0407-06 remains a very good target, though, from all known hemispheres. Other supplements to the last announcement: BW Scl, in the south, and HS2331+3905 are still very, very good targets, if you can handle the faintness (about 16.7). These bookended N/S stars show a fascinating array of periods, including some not really seen in any other CVs. More details after I return from compulsory national eating rituals... Oh, and FS Aur! Time to start up our annual (northern) campaign on this star again. Talk about rituals. This one is easier at about 14.5-15. joe From jop at astro.columbia.edu Fri Nov 24 06:16:43 2006 From: jop at astro.columbia.edu (Joe Patterson) Date: Fri, 24 Nov 2006 06:16:43 -0500 Subject: (cba:news) Re: (cba:chat) FS Aur outburst In-Reply-To: <107443.27781.qm@web30501.mail.mud.yahoo.com> References: <107443.27781.qm@web30501.mail.mud.yahoo.com> Message-ID: <4566D49B.1040902@astro.columbia.edu> Whoa! This is great news. Let me refresh everyone on FS Aur, the star that has *completely* defied efforts to understand. The radial-velocity period is 0.059 days, and we generally assume P(vrad) = Porb. CVs of that Porb are decently understood - nearly all are SU UMa stars, with superoutbursts, superhumps, etc... we all know the drill. But FS Aur certainly has no superoutbursts or superhumps - just these rare and brief outbursts which don't fit into any known scheme for understanding eruptions. None have ever been followed well with time-series photometry (though I think Tom Krajci covered one decently from one longitude). The other mystery - the biggest one I guess - is that there's a large-amplitude signal at 0.142 d in the light curve... unrelated to everything else about the star, but obviously of deep significance (because the amplitude is very large). So let's follow it into its latest adventure. BTW I have a draft of a paper on FS Aur - collaboration with the AAVSO - which is almost done and just waiting for the sky to settle down a bit! joe Jeannie Monteith wrote: > Yes, I am about to start it now. > TUT & Jeannie Campbell > Whispering Pine Observatories > HArrison ARK, USA > --- bart staels wrote: > >> I just ended a 7-hour run on FS Aur ; is definitely in outburst >> (14.891 in the beginning of the run and 14.187 near the end); anyone >> able to take over in the States? >> >> stargreetings >> >> Bart Staels >> CBA Flanders >>