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ASASSN-18ey: a suspected black-hole binary in a bright outburst

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clittlefield
ASASSN-18ey: a suspected black-hole binary in a bright outburst

The outbursting black-hole binary ASASSN-18ey (MAXI J1820+070) is currently the subject of a flurry of circulars at The Astronomer's Telegram, but it hasn't received much attention from amateurs. This object shows rapid, aperiodic optical variations on a range of timescales, from milliseconds to several tens of seconds. Even with noise from seeing variations and scintillation, I suspect that amateurs should be able to detect the slower flares, as their amplitude (several tenths of a magnitude) is rather large and the system is bright enough (V = 12.75 on March 16; my measurement) for small telescopes to use short exposure times, particularly if no filter is used. A cadence of < 10 sec per image should be feasible for many amateurs, although at such a fast cadence, it is important to ensure that (1) the computer's clock is accurate and (2) the CCD shutter lag is corrected for.

During an outburst, much of the system's accretion disk falls into the black hole. The rapid optical flaring is thought to originate from a relativistic jet, X-ray pulses from the inner disk that are subseqently reprocessed into optical wavelengths, or some combination of the two. Bright optical outbursts in such systems are relatively uncommon.

The system's J2000 coordinates are 18 20 21.95, +07 11 07.3.

Best,

Colin

FRF
FRF's picture
Observed with V filter?

Hi Colin,

Have you obvserved ASASSN-18ey with V filter?
In this case I gonna write you an email, since it seems I've discovered an SR variable only a arcmin from ASASSN-18ey.

Clear skies,

Robert Fidrich (FRF)

hambsch
hambsch's picture
Short cadence

Hi,

I will try to get some imaging tonight using 10 sec exposure times using Clear filter.

Josch

Deconinck Michel
Deconinck Michel's picture
Thank you for this post Colin

Thank you for this post Colin !!!

Maybe of very small scientific value but I estimated this object this morning (2018-03-19 4:12 UTC) +/- +12.3 and as often I did a sketch of the field.

Did you think that we could be able to detect visualy some variations or scintillation, if yes I'll have to try again.

Clear sky to you all.

 

Michel (DMIB)

weo
weo's picture
AAVSO Alert Notice 624

AAVSO Alert Notice 624 announces a request for observations of ASASSN-18ey = MAXI J1820+070. Please see the notice for details and observing instructions.

Many thanks, and Good observing,

Elizabeth Waagen, AAVSO HQ

FRF
FRF's picture
Vend43: a new SR variable near ASASSN-18ey (MAXI J1820+070)

A few days ago I discovered a new SRB type variable only 6.5' from ASASSN-18ey (MAXI J1820+070). The period of Vend43 is 89.1 days. Range: 15.1-16.1V
If you observe ASASSN-18ey with V filter, don't forget to do photometry of Vend43 too!

Thanx for Colin Littlefield for providing new photometry for Vend43!

AAVSO chart with Vend43 in the centre:
https://www.aavso.org/apps/vsp/chart/X22757EY.png

More details:

https://www.aavso.org/vsx/index.php?view=detail.top&oid=611969

Clear skies,

Robert Fidrich
HAA/VSS
Vendégcsillag-kereső (Guest Star Hunter) team

weo
weo's picture
XMM and VLT campaign on ASASSN-18ey = MAXI J1820+070

AAVSO Alert Notice 625 announces a multiwavelength campaign beginning TONIGHT on ASASSN-18ey = MAXI J1820+070. Please see the notice for details and observing instructions.

Many thanks, and Good observing,

Elizabeth Waagen, AAVSO HQ

 

gsivakoff
Update on outburst and call to action

Hi All,

I apologize for not getting back to you all sooner. I have been travelling quite a bit lately, all while trying to juggle observations of multiple transients on a variety of multi-wavelength facilities.

Black hole X-ray binaries tend to undergo one of two types of outbursts. The first (often called a "canonical outburst") involves a variety of changes in the properties of the disk that feeds the black hole and the jets/winds that can escape before they fall within the black hole's event horizon. The second (often called a "hard-state-only outburst") only involves the  "hard" and the "hard-intermediate" accretion states. Each outburst provides different opportunities for studying the connection between accretion inflows and outflows.

MAXI J1820+070/ASASSN-18ey (hereafter MAXI J1820+070 to save a few characters) has appeared to have stalled its evolution in the "hard" state. This behaviour tends to occur in "hard-state-only" outbursts. For observers, the stalled behaviour means an extended opportunity to study the "hard" accretion state (which has an analogue with the accretion state of the vast majority of accreting supermassive black holes). While many of our observational programs were hoping to catch that transition from the "hard" state through the "intermediate" states to the "soft" state, we have adapted our plans to this outburst's behaviour. (And to be fair, many observational programs were already designed for the "hard" state).

A second implication of the stalled behaviour at its current bright levels is that MAXI J1820+070 may be atypically close for a black hole X-ray binary. I have estimated that the source could be only 1 kpc (3260 light-years) away, which would make it one of the nearest black hole X-ray binaries. This possibility has many of us quite excited; GAIA should provide the distance measurement via parallax soon.

I am leading what I like to call a "blitz" campaign on the source. I use this term for a significant multiwavelength campaign focussed on a single day. My collaborators and I have planned this blitz for the night of April 11th. (Again I apologize for the short delay, but putting this together has taken all of my time recently). The campaign is designed to measure both rapid variability features (0.01 - 100 Hz) from X-ray to radio frequencies and the (quasi-)simultaneous broad-band spectral energy distribution. Since the campaign is focusing on facilities that can see MAXI J1820+070 at some time within the window of April 12th 05:00 -  15:00 UTC, we strongly encourage multiwavelength observations (and communication of those observations) within that window. Observations within approximately 24 hours on either side of the window will also be useful for this campaign.

For those with the capacity to do many high cadence CCD/CMOS observations on this bright source, we have been using the following comparison star:  URAT1 486-270264 (Zacharias et al. 2015) at RA=18h20m26.43s, Dec=+07d10m11.8s. For an example, see http://www.astronomerstelegram.org/?read=11437

I have reports that 1 Hz (1-second exposure) imaging can be done on a 12" telescope with a fairly standard CCD. Although I cannot verify what the readout time or the what type of shutter was used. If you are going to try high cadence observations, be aware that both readout time and your shutter may be a limiting factor. Some detectors are capable of sub-array modes that reduce readout time at the sacrifice of your field of view.

Clear skies!

Greg Sivakoff, on behalf of a large (and fairly open!) collaboration

hambsch
hambsch's picture
Observations

Hi,

I am observing this object since I know about. I have reduced exposure times serval times. From tonight onwards I will try to expose for 2 s in both I and V bands.

Data are sent to the AAVSO database. AAVSO initial is HMB.

Josch

weo
weo's picture
ASASSN-18ey observations needed now - AAVSO Alert Notice 630

AAVSO Alert Notice 630 announces the campaign by Dr. Greg Sivakoff on ASASSN-18ey taking place tonight and tomorrow. Please see the notice for details and observing instructions, and for important information about the comp star to use for high-cadence time series.

Many thanks, and Good observing,

Elizabeth O. Waagen, AAVSO HQ

clittlefield
Shutter lag and accuracy of timestamps

While CCD shutter lag can normally be neglected for long exposure times, it becomes increasingly important in short exposures. For example, I measured the shutter lag of my university's CCD to be about 3 seconds, defined as the difference between the actual time at which the shutter opened and the timestamp recorded in the .fits header. This means that the timestamp of each image is three seconds early, which is problematic when observing with 1- or 2-second exposures. I recommend that each ASASSN-18ey observer measure the shutter lag in their camera so that their timestamps are as accurate as possible.

Best,

Colin

libmar96
CMOS follow-up

I plan to observe this target today using 203/800 and ASI178MM-c CMOS camera with FTP and Time The Sat (GPS application) for precise times. Both show almost the same time, based on my previous attempts with asteroid occultations (<0.1s difference). Such target would require exposure of 0.1-0.2s when CV or 0.5-1.0s with V or R. Because there is almost no delay between frames, do you really need thousands of short cadency measurements or you prefer binned ones (eg. 25x0.2s)?

Regards,

Gabriel Murawski

clittlefield
fast flaring

Hi Gabriel,

Although I'm not part of this campaign, my advice would be go to as fast as possible while maintaining an adequate SNR. In ATel 11426 (Sako et al.) and ATel 11437 (Gandhi et al.), there are reports of fast, large-amplitude flaring on timescales of much shorter than one second. In binned observations, these flares would be averaged out, so I suspect that your fastest-possible cadence would be the most useful to Dr. Sivakoff and his colleagues.

Best,

Colin

pablotwa
pablotwa's picture
I just uploaded several hundred observations in BVI and CV

I just uploaded several hundred observations in BVI and CV do you guys need me to share the subs from Vphot?. Also do we need to observe it tonight April the 13th LAX time into the morning of the 14th?. I used comp star 128 as the check star on all filters except B because 128 was too faint so I used 109 instead for B.

Pablo

weo
weo's picture
Please observe through night of April 13/14

Yes, please observe ASASSN-18ey through the night of April 13/14. That will give 24 hours of coverage after the "blitz" window, as Dr. Sivakoff requested, and a little bit more for luck!

Thanks and Good observing,

Elizabeth

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