A variety of interesting objects such as Wolf–Rayet stars, tight OB associations, planetary nebulae, X-ray binaries, etc., can be discovered as point or compact sources in Hα surveys. How these objects distribute through a galaxy sheds light on the galaxy star formation rate and history, mass distribution, and dynamics. The nearby galaxy M33 is an excellent place to study the distribution of Hα-bright point sources in a flocculant spiral galaxy. We have reprocessed an archived WIYN continuum-subtracted Hα image of the inner 6farcm5 × 6farcm5 of M33 and, employing both eye and machine searches, have tabulated sources with a flux greater than approximately 10−15 erg cm−2s−1. We have effectively recovered previously mapped H ii regions and have identified 152 unresolved point sources and 122 marginally resolved compact sources, of which 39 have not been previously identified in any archive. An additional 99 Hα sources were found to have sufficient archival flux values to generate a Spectral Energy Distribution. Using the SED, flux values, Hα flux value, and compactness, we classified 67 of these sources.

We report the joint WASP/KELT discovery of WASP-167b/KELT-13b, a transiting hot Jupiter with a 2.02-d orbit around a V = 10.5, F1V star with [Fe/H] = 0.1 ± 0.1. The 1.5 RJup planet was confirmed by Doppler tomography of the stellar line profiles during transit. We place a limit of <8 MJup on its mass. The planet is in a retrograde orbit with a sky-projected spin–orbit angle of λ = −165° ± 5°. This is in agreement with the known tendency for orbits around hotter stars to be more likely to be misaligned. WASP-167/KELT-13 is one of the few systems where the stellar rotation period is less than the planetary orbital period. We find evidence of non-radial stellar pulsations in the host star, making it a δ-Scuti or γ-Dor variable. The similarity to WASP-33, a previously known hot-Jupiter host with pulsations, adds to the suggestion that close-in planets might be able to excite stellar pulsations.

We report the discovery of KELT-20b, a hot Jupiter transiting a $V\sim 7.6$ early A star, HD 185603, with an orbital period of $P\simeq 3.47$ days. Archival and follow-up photometry, Gaia parallax, radial velocities, Doppler tomography, and AO imaging were used to confirm the planetary nature of KELT-20b and characterize the system. From global modeling we infer that KELT-20 is a rapidly rotating ($v\sin {I}_{* }\simeq 120\,\mathrm{km}\ {{\rm{s}}}^{-1}$) A2V star with an effective temperature of ${T}_{\mathrm{eff}}={8730}_{-260}^{+250}$ K, mass of ${M}_{* }={1.76}_{-0.20}^{+0.14}\ \,{M}_{\odot }$, radius of ${R}_{* }={1.561}_{-0.064}^{+0.058}\ \,{R}_{\odot }$, surface gravity of $\mathrm{log}{g}_{* }={4.292}_{-0.020}^{+0.017}$, and age of  $\lesssim 600\,\mathrm{Myr}$. The planetary companion has a radius of ${R}_{P}={1.735}_{-0.075}^{+0.070}\,\,{R}_{{\rm{J}}}$, a semimajor axis of $a={0.0542}_{-0.0021}^{+0.0014}$ au, and a linear ephemeris of ${\mathrm{BJD}}_{\mathrm{TDB}}=2457503.120049\pm 0.000190$ $+E(3.4741070\pm 0.0000019)$. We place a $3\sigma $ upper limit of $\sim 3.5\,\,{M}_{{\rm{J}}}$ on the mass of the planet. Doppler tomographic measurements indicate that the planetary orbit normal is well aligned with the projected spin axis of the star ($\lambda =3\buildrel{\circ}\over{.} 4\pm 2\buildrel{\circ}\over{.} 1$). The inclination of the star is constrained to $24\buildrel{\circ}\over{.} 4\lt {I}_{* }\lt 155\buildrel{\circ}\over{.} 6$, implying a three-dimensional spin–orbit alignment of $1\buildrel{\circ}\over{.} 3\lt \psi \lt 69\buildrel{\circ}\over{.} 8$. KELT-20b receives an insolation flux of $\sim 8\times {10}^{9}\,\mathrm{erg}\,{{\rm{s}}}^{-1}\,{\mathrm{cm}}^{-2}$, implying an equilibrium temperature of of ~2250 K, assuming zero albedo and complete heat redistribution. Due to the high stellar ${T}_{\mathrm{eff}}$, KELT-20b also receives an ultraviolet (wavelength $d\leqslant 91.2$ nm) insolation flux of $\sim 9.1\times {10}^{4}\,\mathrm{erg}\,{{\rm{s}}}^{-1}\,{\mathrm{cm}}^{-2}$, possibly indicating significant atmospheric ablation. Together with WASP-33, Kepler-13 A, HAT-P-57, KELT-17, and KELT-9, KELT-20 is the sixth A star host of a transiting giant planet, and the third-brightest host (in V) of a transiting planet.

During the Space Telescope and Optical Reverberation Mapping Project observations of NGC 5548, the continuum and emission-line variability became decorrelated during the second half of the six-month-long observing campaign. Here we present Swift and Chandra X-ray spectra of NGC 5548 obtained as part of the campaign. The Swift spectra show that excess flux (relative to a power-law continuum) in the soft X-ray band appears before the start of the anomalous emission-line behavior, peaks during the period of the anomaly, and then declines. This is a model-independent result suggesting that the soft excess is related to the anomaly. We divide the Swift data into on- and off-anomaly spectra to characterize the soft excess via spectral fitting. The cause of the spectral differences is likely due to a change in the intrinsic spectrum rather than to variable obscuration or partial covering. The Chandra spectra have lower signal-to-noise ratios, but are consistent with the Swift data. Our preferred model of the soft excess is emission from an optically thick, warm Comptonizing corona, the effective optical depth of which increases during the anomaly. This model simultaneously explains all three observations: the UV emission-line flux decrease, the soft-excess increase, and the emission-line anomaly.

The amount of ultraviolet irradiation and ablation experienced by a planet depends strongly on the temperature of its host star. Of the thousands of extrasolar planets now known, only six have been found that transit hot, A-type stars (with temperatures of 7,300–10,000 kelvin), and no planets are known to transit the even hotter B-type stars. For example, WASP-33 is an A-type star with a temperature of about 7,430 kelvin, which hosts the hottest known transiting planet, WASP-33b (ref. 1); the planet is itself as hot as a red dwarf star of type M (ref. 2). WASP-33b displays a large heat differential between its dayside and nightside2, and is highly inflated–traits that have been linked to high insolation3, 4. However, even at the temperature of its dayside, its atmosphere probably resembles the molecule-dominated atmospheres of other planets and, given the level of ultraviolet irradiation it experiences, its atmosphere is unlikely to be substantially ablated over the lifetime of its star. Here we report observations of the bright star HD 195689 (also known as KELT-9), which reveal a close-in (orbital period of about 1.48 days) transiting giant planet, KELT-9b. At approximately 10,170 kelvin, the host star is at the dividing line between stars of type A and B, and we measure the dayside temperature of KELT-9b to be about 4,600 kelvin. This is as hot as stars of stellar type K4 (ref. 5). The molecules in K stars are entirely dissociated, and so the primary sources of opacity in the dayside atmosphere of KELT-9b are probably atomic metals. Furthermore, KELT-9b receives 700 times more extreme-ultraviolet radiation (that is, with wavelengths shorter than 91.2 nanometres) than WASP-33b, leading to a predicted range of mass-loss rates that could leave the planet largely stripped of its envelope during the main-sequence lifetime of the host star.