Map for Monday evening (Jan. 15 UT) occultations in AZ & CA949 Hel & 801 Helwerthia
Bright asteroidal occultation Mon. pm Jan. 14, Indio, CA to Flagstaff, across Kansas & NY
I sent the message below to observers in central Arizona and to a couple in Calif., but the occultation is visible over a long path that crosses North America from north of San Diego to Portsmouth, NH. Poor weather is currently forecast over most of the path, but weather forecasts this far out can change. The European and NWS forecasts currently say it should be clear in the path across Kansas, and probably also over s.w. Colorado & the St. Joseph, MO area. Partly cloudy skies are expected from n.e. Illinois to the Atlantic coast, so there’s some chance in those areas, too. The event time in Kansas to Toledo, OH is 4:13 UT of Jan. 15 UT (10:13pm CST or 11:13pm EST of Jan. 14 local date) and a minute later over the rest of the path, to the southern tip of Nova Scotia, where the event altitude will be only 6 deg. above the western horizon. Of course, it’ll be higher farther west, 10 deg. in NH; 20 deg. at Toledo, OH; and 28 deg. at St. Joseph, MO. Two other good occultations are described at the bottom of the message.
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We invite you to join our multi-station deployment for this occultation that will be visible from 75 miles northwest of Phoenix and/or 125 miles east of Los Angeles. It is an occultation of 8.2-magnitude SAO 110258 by the 34km asteroid (801) Helwerthia that’s predicted to occur over southern Calif. at 8:11pm PST and over west-central and northern Arizona a minute later (9:12pm MST = 4:12 UT of Jan. 15 UT). The spectral type A3 star, also known as HIP 9272, is in Cetus 2.3 deg. south and a little west of 3rd-magnitude alpha Piscium and 1.0 deg. west-northwest of 5.4-mag. 60 Ceti (which forms a half-deg.-wide pair with 6.0-mag. 61 Ceti). SAO 110258 is at J2000 RA 1h 59m 10.4s, Dec -00 deg. 30’ 25”. If a central occultation occurs at your location, the star will disappear for about 2.5 seconds with a spectacular 8-mag. drop, to the 17th mag. of the asteroid, unless the star is a previously-unknown close double (very possible for this spectral type), in which case, there may be a smaller drop, or the disappearance and/or reappearance may occur in quick steps. The Moon will be only 9 deg. (towards the east-northeast) of the target, but near first quarter, 59% sunlit, that shouldn’t be much of a problem for a star this bright, and may actually help locate the target. Some path maps, finder charts of different scales to locate the star, and other event details are at http://www.asteroidoccultation.com/2019_01/0115_801_62642.htm.
Our preferred deployment area is northwest of Phoenix, along US 93 from northwest of Congress to northwest of Wikieup, AZ; the occultation will occur there at an altitude of 46 deg. in the southwest, azimuth 230 deg. But depending on help we might get from others and the weather, we might deploy along highways and roads farther west, as far west as Indio, Calif. The predicted path is shown on a fairly detailed map of s. Calif. & w. AZ at the top of https://occultationpages.com/20190115hel.html (Thanks, Steve Messner, for posting, the map was generated from the Google Map for the event at http://www.poyntsource.com/New/Global.htm and manually annotated), between the two dark blue lines extending from southwest to northeast across the map; they are labelled “Helwerthia N. lim.” and “Helwerthia S. Limit”. But the predicted path is rather uncertain; the 1-sigma uncertainty is 0.84 path-widths. Even at the predicted central line (the green line between the two limits), the chance for an occultation is only 45%, while it’s 38% at the limits and 14% at the red “1-sigma” limit lines. Steve Messner also posted the N. American maps for the event, and an earlier one (see below) from Steve Preston’s site, on his page for the events. In order to have a good chance of covering Helwerthia, it will be necessary to place stations roughly equi-distant across the zone between the two red lines. We hope to deploy as many as 10 stations, which should give us 3 or 4 chords across Helwerthia. But there are just under 3 hours of useable dark time after dusk; in order to get around that problem, we’ll need to deploy 7 stations on paver stones with paver mounts the night before, similar to what we did in North Carolina last May for the asteroid Elektra, but this is a brighter star so we hope to run more stations. Any help others might give us with the effort would help us complete the effort, and possibly even deploy 2 or 3 more stations. Let me know if you might be able to join the effort. If not, it would be useful to observe from your home with your own equipment, since Helwerthia could have a small satellite that might occult the star briefly even 400 km from the path. The long-range weather forecast is poor, but it could improve as we get closer to the event. It’s also poor for the night before, when we’d need to pre-point the scopes on paver stones. We will cancel the effort if the forecast stays poor. Cloud cover forecasts from both the NWS and the European model, and this message, will be posted later at https://occultationpages.com/20190115hel.html .
Another Occultation the Same Night: Remarkably, 2.5h before the Helwerthia occultation, in the approximate same area there will be an occultation by the 65-km asteroid (949) Hel, so it could be a “Hel-ish” night. The asteroid was named for the Norse goddess of the dead, whose domain also bore her name; the English word “hell” is at least partly derived from it. Both asteroids were discovered by Max Wolf at Heidelberg Observatory in the early 20th century. The Hel occultation will need larger telescopes since it is of a fainter star, 12.4-mag. UCAC4-622-024707 in Auriga about 5 deg. north of 1.6-mag. El Nath and only 0.3 deg. northwest of M36 at J2000 RA 5h 34m 39.8s, Dec +34 deg. 20’ 41”. Some path maps, finder charts of different scales to locate the star, and other event details are at http://www.asteroidoccultation.com/2019_01/0115_801_62642.htm . The path is also shown on the map at https://occultationpages.com/20190115hel.html described above for Helwerthia, with the Hel occultation limits shown as black lines, also from southwest to northeast but at a steeper angle than those for Helwerthia. The Hel event 1-sigma lines are the dashed lines. But the Hel event occurs around nautical twilight; I’ve labelled the Sun altitude at 1-deg. intervals along the Hel occultation southern limit. In the more western parts of the path in California, west of the Salton Sea, the twilight may wash out the target star with wider field-of-view telescopes. The Hel occultation will occur approximately at an altitude of 42 deg. in the east (azimuth 72 deg.); a central occultation should last 5s with a 2.5-mag. drop. The Hel and Helwerthia paths cross at Joshua Tree Nat. Park, but twilight will be relatively bright there. The center of the Hel path crosses US 93 near Kingman, so quite far from Helwerthia there; the northern 1-sigma zone for Helwerthia overlaps with the southern 1-sigma zone for Hel along US 93 north of Wikieup. But for our deployment, I’ll devote resources almost exclusively to the Helwerthia event. The path for the Hel occultation crosses Utah, s. & e. Wyoming, ND, & Winnipeg (at 1:40 UT), and on to s. Greenland, n. Scandinavia, & western Russia.
Good Euryanthe occultation in Phoenix area Jan. 19 pm; other Future Occultations: At 3:58am MST Thurs. Jan. 17, there will be an occultation of a 13.4-mag. star by the asteroid (984) Gretia northeast of the Phoenix area; we may deploy 3 or 4 stations for it, weather permitting. We may have a small effort, one or two stations, for an occultation by (1232) Cortusa at 3:52 am Sat. Jan. 19 over the southern Phoenix area. But we’ll devote most of our effort for an occultation that evening, 10:02pm Sat. Jan. 19 over the Phoenix region, mainly the southern and eastern suburbs, when (527) Euryanthe will occult 8.9-mag. SAO 110872 = TYC 0054-00311-1 = UCAC4-486-004122 (spectral type F8); we plan a major multi-station deployment for that, and encourage observers across the region to help, at least trying to observe the bright event from home. The Euryanthe path also crosses San Pedro Martir Observatory; Albuquerque is at the s. limit; over Topeka, KS & St. Joseph, MO; Gary, IN & Detroit at the n. limit; then like Helwerthia, e. to Portsmouth, NH. The Moon will be 98% sunlit for the Euryanthe occultation as there will be a total lunar eclipse 24h later; fortunately for the Euryanthe event, the Moon will not be a problem as it will be 61 deg. away from SAO 110872 at the time. Some occultations of stars by the Moon can be observed during the total lunar eclipse; the brightest two are mag. 7.8 and 7.9. Some more information about these and other occultations in Arizona are (or soon will be) tabulated and described at http://iota.jhuapl.edu/AZoccs.htm. A few more events in January, and many in February, will be added to the AZoccs Web site in a few days. For information about observing occultations in general, see www.occultations.org/observing/ .
David and Joan Dunham, email@example.com
Bright asteroidal occultation Mon. pm Jan. 14, Indio, CA to Flagstaff, across Kansas & NY
Text and weather maps below
Forecast maps as of AM 1/14
Clear Sky Chart