We present analysis of MACHO Alert 95-30, a dramatic gravitational microlensing event towards the Galactic bulge whose peak magnification departs significantly from the standard point-source microlensing model. Alert 95-30 was observed in real-time by the Global Microlensing Alert Network (GMAN), which obtained densely sampled photometric and spectroscopic data throughout the event. We interpret the light-curve "fine structure" as indicating transit of the lens across the extended face of the source star. This signifies resolution of a star several kpc distant.We find a lens angular impact parameter θ min /θ source = 0.715 ± 0.003. This information, along with the radius and distance of the source, provides an additional constraint on the lensing system. Spectroscopic and photometric data indicate the source is an M4 III star of radius 61 ± 12R ⊙ , located on the far side of the bulge at ∼ 9 kpc. We derive a lens angular velocity, relative to the source, of 21.5 ± 4.9 km s −1 kpc −1 , where the error is dominated by uncertainty in the source radius. Likelihood analysis yields a median lens mass of 0.67 +2.53 −0.46 M ⊙ , located with 80% probability in the Galactic bulge at a distance of 6.93 +1.56 −2.25 kpc. If the lens is a main-sequence star, we can include constraints on the lens luminosity. This modifies our estimates to M lens = 0.53 +0.52 −0.35 M ⊙ and D lens = 6.57 +0.99 −2.25 kpc. Spectra taken during the event show that the absorption line equivalent widths of Hα and the TiO bands near 6700Å vary, as predicted for microlensing of an extended source. This is most likely due to center-to-limb variation in the stellar spectral lines. The observed spectral changes further support our microlensing interpretation. These data demonstrate the feasibility of using microlensing limb crossings as a tool to probe stellar atmospheres directly.Subject headings: dark matter -gravitational lensing -stars: low-mass, brown dwarfsstars: late-type -stars: atmospheres Table 4. Photometry of the source star in MACHO 95-30Observed Extinction Dereddened Abs Mag, 8 kpc Abs Mag, 9 kpc V = 16.21 A V = 1.35 V 0 = 14.86 M V = +0.34 M V = +0.59 K = 9.98 A K = 0.15 K 0 = 9.83 M K = −4.69 M K = −4.45 V − R = 1.39 E(V − R) = 0.34 V − R 0 = 1.05 J − K = 1.12 E(J − K) = 0.23 J − K 0 = 0.89 H − K = 0.26 E(H − K) = 0.08 H − K 0 = 0.18 V − K = 6.23 E(V − K) = 1.21 V − K 0 = 5.03 Bolometric BC K = −2.7 ± 0.1 M bol = −2.0 M bol = −2.25

We systematically surveyed period variations of superhumps in SU UMa-type dwarf novae based on newly obtained data and past publications. In many systems, the evolution of the superhump period is found to be composed of three distinct stages: an early evolutionary stage with a longer superhump period, a middle stage with systematically varying periods, and a final stage with a shorter, stable superhump period. During the middle stage, many systems with superhump periods of less than 0.08 d show positive period derivatives. We present observational characteristics of these stages and give greatly improved statistics. Contrary to an earlier claim, we found no clear evidence for a variation of period derivatives among different superoutbursts of the same object. We present an interpretation that the lengthening of the superhump period is a result of the outward propagation of an eccentricity wave, which is limited by the radius near the tidal truncation. We interpret that late-stage superhumps are rejuvenated excitation of a 3:1 resonance when superhumps in the outer disk are effectively quenched. The general behavior of the period variation, particularly in systems with short orbital periods, appears to follow a scenario proposed in Kato, Maehara, and Monard (2008, PASJ, 60, L23). We also present an observational summary of WZ Sge-type dwarf novae. Many of them have shown long-enduring superhumps during a post-superoutburst stage having longer periods than those during the main superoutburst. The period derivatives in WZ Sge-type dwarf novae are found to be strongly correlated with the fractional superhump excess, or consequently with the mass ratio. WZ Sge-type dwarf novae with a long-lasting rebrightening or with multiple rebrightenings tend to have smaller period derivatives, and are excellent candidates for those systems around or after the period minimum of evolution of cataclysmic variables.

In early 2002 V838 Monocerotis had an extraordinary outburst, the nature of which is still unclear. The optical light curve showed at least three peaks, and imaging revealed a light echo around the object – evidence for a dust shell which was emitted several thousand years ago and now reflecting light from the eruption. Spectral analysis suggests that the object was relatively cold throughout the event, which was characterized by an expansion to extremely large radii. We show that the three peaks in the light curve have a similar shape and thus it seems likely that a certain phenomenon was three times repeated. Our suggestion that the outburst was caused by the expansion of a red giant, followed by the successive swallowing of three relatively massive planets in close orbits, supplies a simple explanation to all observed peculiarities of this intriguing object.

The new-ray burst (GRB) mission Swift has obtained pointed observations of several classical novae in outburst. We analyzed all the observations of classical novae from the Swift archive up to 2006 June 30. We analyzed usable observations of 12 classical novae and found 4 nondetections, 3 weak sources, and 5 strong sources. This includes detections of two novae exhibiting spectra resembling those of supersoft X-ray binary source spectra (SSS), implying ongoing nuclear burning on the white dwarf surface. With these new Swift data, we add to the growing statistics of the X-ray duration and characteristics of classical novae.

We report new photometry of the cataclysmic variable AM Canum Venaticorum, comprising 670 hr over 227 nights during 1992È1999. The data demonstrate conclusively that (1) the fundamental period is 1051.2 s, with a well-deÐned waveform which has not changed during the four decades of study ; (2) this period wanders erratically by D0.2 s on a timescale of 3È6 months ; and (3) the light curve contains a rich spectrum of periodic signals, at least 20 of them. We also report a secure detection of a photometric signal at 1028.7322 ^0.0003 s, consistent with the orbital period previously hypothesized to explain the spectroscopic variations.The behavior of the 1051 s signal is consistent with the hypothesis of a superhump origin, and the discovery of a signal at the presumed is yet another strong argument for this hypothesis. Apparently P orb superhumps can manufacture a very complex spectrum of photometric periods, and they can remain stable for many thousands of cycles. But most are harmonics and sidebands of the truly fundamental clocks in the binary, at and the diskÏs two likely periods of precessionÈat 13.36 and 16.69 hr. It is plausible that the P orb latter correspond to the periods of apsidal advance and nodal regression. The former is steadily present, evidently producing the well-known superhump. The signatures of nodal regression, primarily the 1011.4 s "" negative superhump,ÏÏ are more variable. The sideband structure of the harmonics obeys Ðrm selection rules, which may reveal intricate details of structure in the accretion disk. And somehow all these exotic clocks manage to coexist and remain relatively stable, despite being putatively seated in the relatively sloppy structure of a disk, highly sheared and unsupported by pressure ! ÈÈÈÈÈÈÈÈÈÈÈÈÈÈÈ 1 Center for Backyard Astrophysics (East),