From jop at astro.columbia.edu Sat May 5 15:33:19 2018 From: jop at astro.columbia.edu (Joe Patterson) Date: Sat, 5 May 2018 15:33:19 -0400 Subject: (cba:news) ASASSN-18ey = MAXI J1820+070 Message-ID: <5f829af1-e1a6-0c06-7d9c-dbe1cec3210c@astro.columbia.edu> Hi CBAers, Some of you probably saw the ATEl that Michael Richmond and Stephen Brincat sent out, reporting, among other things, a 3.4 hour period in the light curve of this still crazy-bright X-ray (presumably black-hole) transient. Origin unknown, but let's jump in and figure it out! All longitudes and latitudes and lassitudes invited. As usual, long (3+ hours) coverage will have greatest impact. But all the data show a point-to-point scatter far greater than the error of measurement. This means that there is considerable source variation on timescales of just a few seconds - basically unlike CVs, which are considerably fonder of timescales around *minutes*, not *seconds*. We found a similar thing years ago: a 6-second QPO in our study of 1118+48, another black-hole transient. So as long as the source is bright (now 12.5) and assuming your measurement error can tolerate it, keep the integrations short! (Can't be any more quantitative than that, since we don't actually know the timescale). I certainly recommend this guy as #1 priority. Some of you are doing a great job with AM CVn, and our many-month coverage of it will have great impact. But old Maxie has highest priority whenever it's above 2 airmasses - certainly at non-USA longitudes, and I'd say at USA also. joe p ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Thu May 10 06:00:57 2018 From: jop at astro.columbia.edu (Joe Patterson) Date: Thu, 10 May 2018 06:00:57 -0400 Subject: (cba:news) ASASSN-18ey = MAXI j1820-070 Message-ID: <848bf068-3b1d-f2ec-d2e4-25da3e19bf20@astro.columbia.edu> Hi CBAers, Some great data on this star rolling in. It's declining VERY slowly - still about V-12.8 - and showing some waves suggestive of a period near 3.5 or 7 hours. Promises to be a great target for the next month or more. While a few runs showed some quasi-periodic oscillations with a timescale near 12 s, this is a REALLY awkward timescale for us to investigate. The readout ("dead") time is a mighty big price to pay, and I suggest we abandon this (high-speed) observing style. We'll get much better sensitivity if we adopt integration times appropriate for the brightness - maybe 20 sec in clear light, or ~40 s in V (still bright enough for V, if you like your V filter). The equatorial location and short northern nights are also somewhat problematic, since we thrive on LONG nightly time series. We can overcome this with an even-more-than-usually-extensive spread in terrestrial longitude. And let's do it! This ia the brightest black-hole transient in many years, and we already have a nice supply of X-ray and Hubble data to accompany the optical time series. The most prolific observers so far are Michael Richmond in Rochester, NY, John Rock in England, Tonny Vanmunster in Belgium, and Stephen Brincat in Malta. The first three are in famously cloudy and certainly northern locations, so their luck can't continue long. There's not much data yet from the western USA, so that would help a lot. Also AU/NZ, Africa, and southern Europe (except Brincat) have been quiet. Oops, I forgot Josch Hambsch from Chile. His data, nearly every night and well-calibrated, will eventually have a big impact. But the lower time resolution makes it less suitable for *defining* the features (eclipses?) in the light curve. So I hope that the USA observers will keep a close watch on this fascinating star - which seems ready to surrender a few secrets, but is making us work hard for them! joe p ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jp42 at columbia.edu Mon May 14 15:11:42 2018 From: jp42 at columbia.edu (Joe Patterson) Date: Mon, 14 May 2018 15:11:42 -0400 Subject: (cba:news) N Sco 1437 outburst, AM CVn, HP Lib, ASASSN-18ey (Maxie) In-Reply-To: <4f88149a-9567-4fa6-5199-0001178b84e5@dcsi.net.au> References: <4f88149a-9567-4fa6-5199-0001178b84e5@dcsi.net.au> Message-ID: Hi CBAers, The message below - from Rod Stubbings, who never misses anything - vaults this star into a CBA target of prime importance.? The star itself was recently discovered as a dwarf-nova coincident with a 1437 classical nova.? So it's plenty interesting from that standpoint.? Even more because it appears to be eclipsing.? The 2000 coordinates are 17h 01m 28.53s, -43d 05m 57s.? It's a crowded field, but since the dwarf-nova is now quite bright, that should help! There appear to many physically significant timescales in this star: a 30-minute spin (or something similar) period, a 12 hour orbital period, and the (unknown but maybe ~300 d) outburst period.? Very ripe for CBA analysis! It has been our finest year on AM CVn, and some continuation of the coverage would help.? But, whatever your latitude, i hope you give prime attention to HP Lib.? Only once, 20 years ago, did we concentrate on this star, and it is high time we make it a major target for a couple of months. Maxie also deserves your continued close attention.? We probably will have a second HST observation in the next few weeks... but we need maximally continuous coverage to detect and track its tricky 3- or 6-hour variation (orbital, maybe?). A lot of data coming in.? And now that classes/exams/grading is all finished, I can dive into the analysis with the energy it deserves. joe p -------- Forwarded Message -------- Subject: [vsnet-alert 22160] N Sco 1437 outburst Date: Mon, 14 May 2018 21:25:13 +1000 From: Rod Stubbings To: vsnet-alert N Sco 1437 is in outburst N SCO 1437 180513.517 160 Stu.RASNZ N SCO 1437 180514.458 121 Stu.RASNZ -- Rod Stubbings Tetoora Road Observatory Victoria, Australia Telescope: "Infinity" 22" f/3.8 stubbo at dcsi.net.au http://rodstubbingsobservatory.wordpress.com/ ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jop at astro.columbia.edu Mon May 21 06:15:49 2018 From: jop at astro.columbia.edu (Joe Patterson) Date: Mon, 21 May 2018 06:15:49 -0400 Subject: (cba:news) SDSS J141118.31+481257.6 = AM CVn star in Bootes Message-ID: Dear CBAers, We've never observed this star before, but its nature (a long-period AM CVn star), brightness (14-15), and sky position (transiting near midnight) make it ideal for us. Among the several unique stars cavorting in tonight's sky, here's one in the far north, making it ideal in this season of short nights. Let's definitely *replace* AM CVn itself with J1411+48 as the prime northern target. Not to take away from MAXI = ASASSN-18ey. That one gets better with each passing week - because of sky position, because the amplitude of variation grows (and PROBABLY gets more coherent), and more generally, because bright black-hole transients are so rare. Finally among these true glamor targets is Nova Sco 1437. Two of us - Berto and Greg Bolt - are having a fine old time tracking its remarkable periodic signals (an eclipse and a DQ Her-type signal). It's in the far south, unavailable to most of us. But judging from coverage so far, the weather in Perth and the Karoo has been excellent! Pardon me from failing to mention other targets for now. Getting a little behind with all this new stuff arriving! joe p ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ From jp42 at columbia.edu Wed May 30 07:51:20 2018 From: jp42 at columbia.edu (Joe Patterson) Date: Wed, 30 May 2018 07:51:20 -0400 Subject: (cba:news) Fwd: (cba:chat) some ASASSN-18ey = MAXI j1820-070 = "Maxie" chatter In-Reply-To: References: Message-ID: <8447f451-680c-1283-b4fc-de0630d98658@columbia.edu> Forwarded to cba-news just to cover the AU/NZ observers who could really help in this enterprise... joe p -------- Forwarded Message -------- Subject: (cba:chat) some ASASSN-18ey = MAXI j1820-070 = "Maxie" chatter Date: Tue, 29 May 2018 12:08:42 -0400 From: Joe Patterson Reply-To: To: Hi CBAers, I've more or less kept up with the impressive flow of CBA data on this fascinating star.? The light curves are plenty noisy - all due to noise in the STAR, not the measurement - but suggest a wave of period 0.328 d, about twice that reported by Michael R. and Josch H.? It sometimes appears as a double-hump wave, so it's tricky to tell them apart.? The wave also may not be phase-stable, suggesting it might be a superhump rather than the true orbital period.? Either is mighty welcome of course, but especially the superhump since such things can reveal the mass ratio - and thus possibly the black-hole mass. These black-hole transients are RARE in our galaxy - I only know of ~8 in the last 40 years.? The noise (flickering, quasi-periods) in the light curve is annoying, but this object will repay close study over the next couple of months. It would be great to get some data from AU/NZ.? The longish period (assuming it's correct) creates some aliasing issues, and northern Europe is substantially handicapped by the short nights.? Despite the marginally northern dec, *southern* observers are in the best position to get long runs.? Especially in Oceania, of course! No disrespect for the other great star of the season, SDSS 1411+48, which is flashing eclipses, rotation-period signals and a well-defined dwarf-nova outburst.? I haven't yet gotten down and dirty with this data, but it sure looks like fun.? The star has dipped to 17.5, but keep watch on it; these stars can stage comebacks! joe p On 5/28/2018 3:39 PM, Josch Hambsch wrote: > > Hi Joe, > > I have been following 18ey every clear night since its discovery. > > Attached a screen shot from PERANSO showing most of the data (the gap > between about day 40 and 60 I still need to fill, data are available). > > As you can see there is a long term periodicity of about 37 days (the > one peak at about day 21 is due to observations in I and V band > filters, need to be removed). As well in the past two nights a > periodicity of about 0.16 days (about 3.8h) popped up as seen in the > colored data. Maybe this confirms what has been found by M. Richmond > in ATEL #11596. > > Regards, > > Josch > > *From:*cba-chat [mailto:cba-chat-bounces at cbastro.org] *On Behalf Of > *Stephen M. Brincat > *Sent:* Freitag, 11. Mai 2018 10:28 > *To:* cba-chat at cbastro.org > *Subject:* Re: (cba:chat) (cba:news) ASASSN-18ey = MAXI j1820-070 > > Hi Joe, > > I regret that I will not be in a position to image for some days as I > am going through a mount upgrade. Weather can also be uncooperative > here as at this time of the year, humid conditions bring over low > altitude clouds that form over the mainland. This winter we had > persistent cloud cover with the remaining few clear nights coupled > with high winds. > > >> The most prolific observers so far are Michael Richmond in Rochester, > NY, John Rock in England, Tonny Vanmunster in Belgium, and Stephen Brincat > in Malta.? The first three are in famously cloudy and certainly northern > locations, so their luck can't continue long. > > Regards & Clear Skies, > > Stephen > > > /Flarestar Observatory > IAU/MPC code: 171 > flarestar.weebly.com [ flarestar. weebly. com ] / > > On 10 May 2018 at 12:00, Joe Patterson > wrote: > > Hi CBAers, > > Some great data on this star rolling in.? It's declining VERY slowly - > still about V-12.8 - and showing some waves suggestive of a period > near 3.5 or 7 hours.? Promises to be a great target for the next month > or more. > > While a few runs showed some quasi-periodic oscillations with a > timescale near 12 s, this is a REALLY awkward timescale for us to > investigate.? The readout ("dead") time is a mighty big price to pay, > and I suggest we abandon this (high-speed) observing style.? We'll get > much better sensitivity if we adopt integration times appropriate for > the brightness - maybe 20 sec in clear light, or ~40 s in V (still > bright enough for V, if you like your V filter). > > The equatorial location and short northern nights are also somewhat > problematic, since we thrive on LONG nightly time series. We can > overcome this with an even-more-than-usually-extensive spread in > terrestrial longitude.? And let's do it!? This ia the brightest > black-hole transient in many years, and we already have a nice supply > of X-ray and Hubble data to accompany the optical time series. > > The most prolific observers so far are Michael Richmond in Rochester, > NY, John Rock in England, Tonny Vanmunster in Belgium, and Stephen > Brincat in Malta. The first three are in famously cloudy and certainly > northern locations, so their luck can't continue long.? There's not > much data yet from the western USA, so that would help a lot.? Also > AU/NZ, Africa, and southern Europe (except Brincat) have been quiet. > > Oops, I forgot Josch Hambsch from Chile.? His data, nearly every night > and well-calibrated, will eventually have a big impact.? But the lower > time resolution makes it less suitable for *defining* the features > (eclipses?) in the light curve.? So I hope that the USA observers will > keep a close watch on this fascinating star - which seems ready to > surrender a few secrets, but is making us work hard for them! > > joe p > > ____________________________________________________________ > Center for Backyard Astrophysics (CBA) mailing lists > https://cbastro.org/communications/mailing-lists/ > > > > Virenfrei. www.avast.com > > > > <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > > > ____________________________________________________________ > Center for Backyard Astrophysics (CBA) mailing lists > https://cbastro.org/communications/mailing-lists/ ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/ ____________________________________________________________ Center for Backyard Astrophysics (CBA) mailing lists https://cbastro.org/communications/mailing-lists/