(cba:news) FO Aqr, back in the saddle again...

Joe Patterson jop at astro.columbia.edu
Thu Oct 9 07:12:11 EDT 2014


Dear CBAers,

FO Aquarii, one of our oldest friends, is misbehaving.  The 21 minute 
period is shortening over the years, as are nearly all DQ Her stars (aka 
intermediate polars).  But the 2013/4 period change is much too fast - 
way out of bounds.  The star did something like this before (period 
increasing), and I suspect now that I was too hasty in regarding such 
misadventures as the result of some inscrutable noise process.  It might 
be, of course... but now I realize I have to go through the 33 years of 
timings and study the residuals after the long-term period decrease is 
removed.

Or better yet, if someone else did.

Anyway, regardless of whether anyone is willing to put me out of my 
misery, it's important to put the star back on the menu.  Still pretty 
well placed in the night sky... available to all hemispheres... and 
plenty bright (about 14.0), with a very large pulse amplitude. 
Actually, for any of you unacquainted with this star, it has one of the 
most beautiful light curves in our collection.  I attach a splice of 
2013 data from Berto and Greg Bolt.  You can see that it deserves its 
title: King of the DQ Herculis stars!  A good comparison is the AAVSO 
122 star (V=12.213).

Although short runs are definitely useful, longish (3-4 hrs) runs are 
preferred, because there are signals closely spaced in frequency (the 
spin frequency, plus an orbital sideband)... and technically it takes a 
full 4.8 hr orbit to *fully* resolve them.  It's not a hugely 
significant point, because with abundant data the signals are very well 
distinguished.  But longer is better.

Enrique actually started the season back in July, so we have a decent 
baseline already.  But let's get some good round-the-world coverage now, 
so we can explore these odd period changes in a supposedly 
well-understood star (not!).

joe

p.s. Josch, with the pulse period being relatively long and the 
amplitude high, it might be a good target for your mode of observing.
Nightly observing with a single telescope would also allow us to check 
on whether the night-to-night phase changes (which also occur) are 
related to changes in brightness (accretion rate??).  That's always been 
an unknown, and I've never had the data to evaluate it.
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80.55745      1.425
80.55780      1.410
80.55814      1.464
80.55849      1.499
80.55884      1.414
80.55918      1.452
80.55953      1.504
80.55988      1.529
80.56023      1.540
80.56057      1.441
80.56092      1.499
80.56127      1.503
80.56161      1.546
80.56196      1.498
80.56231      1.432
80.56266      1.404
80.56300      1.337
80.56335      1.310
80.56370      1.279
80.56405      1.233
80.56440      1.146
80.56475      1.166
80.56510      1.195
80.56545      1.183
80.56579      1.200
80.56614      1.188
80.56649      1.163
80.56683      1.153
80.56718      1.132
80.56753      1.130
80.56788      1.124
80.56822      1.145
80.56857      1.136
80.56892      1.174
80.56927      1.195
80.56961      1.195
80.56996      1.192
80.57031      1.219
80.57065      1.300
80.57100      1.365
80.57135      1.433
80.57170      1.451
80.57204      1.493
80.57239      1.485
80.57274      1.512
80.57308      1.535
80.57343      1.536
80.57378      1.512
80.57413      1.524
80.57447      1.487
80.57483      1.446
80.57518      1.470
80.57553      1.490
80.57587      1.507
80.57622      1.509
80.57657      1.477
80.57692      1.342
80.57726      1.254
80.57761      1.278
80.57796      1.282
80.57830      1.234
80.57865      1.147
80.57900      1.158
80.57935      1.114
80.57969      1.051
80.58004      1.051
80.58039      1.038
80.58073      1.075
80.58108      1.129
80.58143      1.146
80.58178      1.140
80.58212      1.135
80.58247      1.164
80.58282      1.155
80.58317      1.164
80.58351      1.194
80.58386      1.227
80.58421      1.256
80.58455      1.300
80.58490      1.280
80.58525      1.302
80.58560      1.400
80.58594      1.352
80.58629      1.296
80.58664      1.350
80.58698      1.442
80.58734      1.479
80.58769      1.436
80.58804      1.428
80.58839      1.467
80.58873      1.445
80.58908      1.387
80.58943      1.450
80.58977      1.445
80.59012      1.444
80.59047      1.383
80.59082      1.355
80.59116      1.319
80.59151      1.300
80.59186      1.288
80.59220      1.305
80.59255      1.257
80.59290      1.225
80.59325      1.163
80.59359      1.072
80.59394      1.047
80.59429      1.042
80.59464      1.096
80.59498      1.137
80.59533      1.141
80.59568      1.094
80.59602      1.105
80.59637      1.131
80.59672      1.112
80.59707      1.164
80.59741      1.189
80.59776      1.214
80.59811      1.251
80.59845      1.255
80.59880      1.278
80.59915      1.295
80.59951      1.336
80.59986      1.318
80.60020      1.342
80.60055      1.370
80.60090      1.401
80.60124      1.420
80.60159      1.425
80.60194      1.431
80.60229      1.464
80.60263      1.483
80.60298      1.479
80.60333      1.462
80.60367      1.494
80.60402      1.492
80.60437      1.451
80.60472      1.426
80.60506      1.384
80.60541      1.356
80.60576      1.297
80.60611      1.337
80.60645      1.310
80.60680      1.293
80.60715      1.237
80.60749      1.255
80.60784      1.270
80.60819      1.204
80.60854      1.169
80.60888      1.223
80.60923      1.218
80.60958      1.243
80.60992      1.248
80.61027      1.232
80.61063      1.179
80.61098      1.251
80.61133      1.218
80.61167      1.251
80.61202      1.286
80.61237      1.299
80.61271      1.293
80.61306      1.270
80.61341      1.263
80.61376      1.301
80.61410      1.374
80.61445      1.361
80.61480      1.340
80.61514      1.420
80.61549      1.486
80.61584      1.529
80.61619      1.489
80.61653      1.460
80.61688      1.468
80.61723      1.411
80.61758      1.380
80.61792      1.371
80.61827      1.359
80.61862      1.375
80.61896      1.346
80.61932      1.275
80.61967      1.258
80.62002      1.229
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