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(cba:news) Fwd: (cba:chat) some ASASSN-18ey = MAXI j1820-070 = "Maxie" chatter (Joe Patterson) [2018-05-30T11:51:24Z]

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 <jp42@xxxxxxxxxxxx>
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@xxxxxxxxxxx] *On Behalf Of *Stephen M. Brincat 
*Sent:* Freitag, 11. Mai 2018 10:28
*To:* cba-chat@xxxxxxxxxxx
*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 <jop@xxxxxxxxxxxxxxxxxx <mailto:jop@xxxxxxxxxxxxxxxxxx>> 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

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