Skip to main content

Web Publications


          THE AMERICAN ASSOCIATION OF VARIABLE STAR OBSERVERS
               25 Birch Street, Cambridge, MA 02138 USA
                BITNET:  aavso@cfa     SPAN:  cfa::aavso
                    INTERNET:  aavso@cfa.harvard.edu
               Tel. 617-354-0484       FAX 617-354-0665


                AAVSO ALERT NOTICE 204 (March 22, 1995)


A VERY SUCCESSFUL ASTRO-2 MISSION COMPLETED

Space shuttle Endeavour landed on March 18, 1995, after a very successful 
ASTRO-2 Mission.  This is a brief report on the mission for the observations 
of variable stars, particularly cataclysmic variables (CVs).

Thanks to your enthusiastic response and dedicated monitoring of variable 
stars in the observing program of the ASTRO-2 mission, we provided continuous 
updates, quite often three times in 24 hours, to the scientists at Marshall 
Space Flight Center on the behavior of these stars.

I want to share with you some of the e-mails I received from the ASTRO-2 
Science Team during the mission, updating us on its status:

March 2 - " As I write this, we are 1hr 30 minutes into the flight and all 
looks well..."

March 4 - "... We got our first observations of CVs this morning.  VW Hyi was 
still in quiescence...we see the WD {white dwarf}... we also have a short 
spectrum of YZ Cnc {at minimum}... Overall things are going very well...  
continued thanks..."

March 8 - "We obtained excellent observations of SS Cyg and U Gem this morning.
Both are quite different from what we observed with Astro-1, presumably due 
to the fact that they are much further along from outburst than then. ...The 
reports you have been sending have been extremely useful.. Continued thanks"

March 9 -  "Our observation of WX Hyi last night {fading from maximum} was 
quite interesting, with very high energy lines present.  It is important to 
get good continued magnitudes for it -- as we wait for VW Hyi.  Thanks..."

March 9 -  " We have just begun the first two LONG (3000 seconds) AM Her 
exposures with HUT {Hopkins Ultraviolet Telescope} on the Astro-2 Mission!  
The data are coming in in real time, and they look great!!... Thanks again 
for all your work..."

March 10 -  "Our observations today of AM Her {at bright state} and EM Cyg 
{at maximum} were quite spectacular.  We observe Z Cam and WX Hyi tomorrow..."

March 11 -  ".. our coordinated observations with ASCA {x-ray satellite) on 
Z Cam were successful.  While ASCA was recording 0.2 counts/s, HUT was 
recording 2500 counts/s..."

March 11 -  "We should have observed EF Eri {at minimum state} this morning 
and WX Hyi once again this evening.  We are awaiting for EM Cyg to start down 
before observing it again -- and for VW Hyi (or U Gem) to go off.  All is 
well here..."

March 13 -  "Can you give me an indication of what you think EM Cyg is likely 
to do - i.e. is it likely to start going down soon.  We observed it for the 
second time last night.  The HUT spectrum looked similar to the one we 
observed 3 days ago {at maximum}.  Thanks..."

March 14 - "Thanks for the information.  I hope it goes down {it did!}.  It 
looks like the end of science operations for Astro will be Thursday night and 
the shuttle will return to earth on Friday afternoon {it returned one day 
later due to weather}... Thanks again..."

March 15 - "Thank you for the information about EM Cyg {started to fade}.  We 
are going to observe it tomorrow, which will be the last CV observation for 
Astro-2.  Shutdown for the experiment is tomorrow night.  Please communicate 
to everyone how valuable their help has been for us... Here is a complete list 
of the CVs we observed, in no particular order:

"SS Cyg, U Gem, VW Hyi, EF Eri, AM Her, EM Cyg, WX Hyi, Z Cam, EX Hya, and 
YZ Cnc.

"It's pretty impressive... Best regards and thanks again..." 

The above sampling of e-mails speaks for itself of your significant 
contributions to this mission.  Besides the cataclysmic variables, variable 
star targets ASTRO-2 monitored included symbiotic stars and a few of the 
recent novae.  Again, your observations helped in the satellite scheduling of 
these objects - as William Blair, a mission scientist, said, "That's crucial 
information for us.  It's driving the way we're planning observations, what 
we want to do with these targets."

For your interest, accompanying this Alert Notice are AAVSO light curves of 
12 of the ASTRO-2 target cataclysmic variables, including observations
reported to the AAVSO by you through March 19-20, two days after the end of 
the mission.

Your efforts were VERY MUCH appreciated by the whole ASTRO-2 Science Team and 
by the NASA ASTRO-2 Program Scientist, so much so that NASA arranged a phone 
interview for me with an Associated Press editor to give information on the 
contribution of amateur astronomers to this mission.  A very nice article was 
prepared and released by the Associated Press which was published on March 9 
in different parts of the country; a copy of the article as it appeared in the 
Boston Globe accompanies this Alert Notice.

After the publication of the article, both the public affairs people at 
Marshall Space Flight Center and we at AAVSO were contacted by several 
reporters who wanted to interview the amateur astronomer(s) in their community 
who were contributing to ASTRO-2.  Several observers have already been 
contacted by the press.  If an article about you has appeared in your local 
newspaper, we would very much appreciate receiving a copy for the AAVSO 
archives.

In addition, NASA arranged for a reporter-and-videographer team to visit the 
AAVSO to film a story on how we at the AAVSO were coordinating this project.  
Also, our member Bill Dillon, who lives near a NASA Center, was interviewed
as to how he was doing his observing for the ASTRO-2 mission.  These 
interviews were combined into a program, which was aired on NASA-Select 
television several times, starting on Sunday, March 11.  Later the NASA 
ASTRO-2 Program Scientist wrote:

March 13 - "I was delighted by the Mission Update story Sara Moquin and Mike 
Arrington put together on AAVSO. It is at least a small testimony to the high 
regard in which this particular mission, and NASA Astrophysics, in general 
holds the contributions of AAVSO and its dedicated membership..."

All of this acknowledgment is truly a testimony to the important role that 
you, our observers, played in the success of the observations of variables 
for this Mission.

If you have a photograph of yourself with your telescope and/or observatory 
please send us a print for our records.  We would like to make a collage of 
these photographs for this and future missions and observing programs.

Please continue to monitor the following CVs that were observed with the 
ASTRO-2 so that we can provide a complete set of data for before, during, and 
after the mission to the Science Team for the correlation of the satellite 
data:

            0139+37 AR And    0804+28 YZ Cnc    0640-16 HL CMa
            0207-63 WX Hyi    0814+73 Z Cam     0829+53 SW UMa
            0219+27 RW Tri    1247-28 EX Hya    1004-69 OY Car
            0309-22 EF Eri    1813+49 AM Her    1325-54 BV Cen
            0409-71 VW Hyi    1934+30 EM Cyg


SUPEROUTBURST OF 1051+50 CY URSAE MAJORIS

The dwarf nova-type cataclysmic variable (SU UMa subclass) is having a 
superoutburst, as indicated by the following observations:

Mar 13.874, <13.2, G. Poyner, Birmingham, England; 18.044, <13.2, P. Schmeer, 
Bischmisheim, Germany; 18.974, <13.2, Poyner; 19.892, 12.3, Schmeer; 19.897, 
12.4, Poyner; 20.025, 12.3, Schmeer; 20.814, 12.2, Schmeer; 20.948, 12.1, 
Schmeer; 21.136, 13.3, M. Adams, Fort Davis, TX; 21.85, 12.7, L. Jensen, 
Farum, Denmark; 21.969, 12.3, Schmeer; 22.845, 12.4, Schmeer. 33 

The last superoutburst of CY UMa was in the end of March to the beginning of 
April 1993, when it reached magnitude 11.9 at maximum.

Please use the accompanying AAVSO "e" scale chart in making your observations.
We note that the sequence by S. Fujino, Japan, on a finder chart provided to 
us by Patrick Schmeer, Germany, is significantly brighter than that of AAVSO's.
The AAVSO photovisual sequence was obtained by Charles Scovil, extrapolating 
from the photoelectric magnitudes of the Guide Star Photoelectric Catalog 
(Lasker et al. 1988, ApJ. Suppl., 68, 1), which should not be confused with 
the Guide Star Catalog on CD-ROM.  Below are the magnitudes from the finder 
chart by the AAVSO and by Fujino:

   AAVSO magnitude       Fujino magnitude      Compass direction
   115                   ---                   N
   ---                   137                   N
   147                   140                   NE
   148                   139                   SE
   135                   129                   SE
   ---                   132                   SE
   123                   ---                   SE
   156                   146                   SW
   140                   136                   SW
   108                   ---                   SW
   ---                   116                   SW
   132                   124                   W
   ---                   150                   NW
   144                   137                   NW

We welcome comments from observers on both sequences.

We are very concerned about the inhomogeneity of the magnitude sequences used 
among observers around the world.  It becomes extremely difficult to compile 
observations from observers who do not use the same sequence.  We try hard to 
have a sequence that is satisfactory, however, we do not claim that AAVSO 
sequences are the best.  We are in the process of having a rigorous evaluation 
of our Preliminary Chart sequences.  Again, we welcome comments from our 
observers, who are the ultimate judges on the quality of the sequences.


OUTBURST OF 0203+56A UV PERSEI

The dwarf nova-type cataclysmic variable (SU UMa subclass) UV Per has 
undergone and is beginning to fade from a short outburst, as indicated by the 
following observations:

Mar 7.863, <14.9, G. Poyner, Birmingham, England;  8.808, <14.9, Poyner; 
10.080, <14.1, T. Vanmunster, Landen Belgium; 11.032, 18.1 CCDV, R. Zissell,
S. Hadley, MA; 11.133, <14.1, Vanmunster; 12.819, <14.9, Poyner; 13.851, 
<14.3, Poyner; 18.808, <15.2, Poyner; 19.393, <15.6, Poyner; 20.833, <13.5, 
P. Schmeer, Bischmisheim, Germany (via G. Poyner); 20.911, 13.9, B. Worraker, 
Didcot, England (via G. Poyner); 21.104, 12.6, M. Adams, Fort Davis, TX; 
21.78, 12.3, L. Jensen, Farum, Denmark; 21.80, 12.5, M. Verdenet, 
Bourbon-Lancy, France; 21.801, 12.8, L. Szentasko, Budapest, Hungary; 21.809, 
12.9, J. Pietz, Erftstadts, Germany; 21.816, 12.3, Schmeer; 21.83, 12.8, 
Verdenet; 22.000, 12.7, J. McKenna, Upper Montclair, NJ; 22.840, 13.5, Schmeer.

The last outburst of UV Per, a superoutburst, occurred in late May - early 
June 1994, when it reached magnitude 11.8 at maximum (please see AAVSO Alert 
Notice 186).

Please use the AAVSO "f" scale chart that was distributed with AAVSO Alert 
Notice 186  to monitor UV Per.  We again note that the sequence on this chart 
was revised in 1981, and that observers should NOT use the pre-1981 UV Per 
charts.  Also, when reporting your observations to AAVSO Headquarters, please 
indicate which chart (including date of issue) and which comparison stars you 
are using.  


REMINDER -- MONITORING 0749+22 U GEMINORUM

U Gem continues to be at minimum since its outburst in August-September 1994.
This is the longest minimum with no observing gaps since 1984.  Several 
astronomers with observing programs using EUVE and HST are awaiting the next 
outburst.  Please continue to monitor U Gem closely and inform us as soon as 
you observe it brightening, i.e., magnitude 13.5 and brighter.

U Gem has fairly deep (0.5 magnitude) eclipses of the "hot spot" on the 
accretion disk by the cool companion.  Dr. B. Paczynski of Princeton 
University, who strongly recommends that visual and particularly CCD observers 
monitor the eclipses, recently wrote, "The eclipses last only about 10 
minutes.  Their width varies by a factor of almost 2 with time: they are 
widest right after the eruption, and gradually narrow down with time, being 
the narrowest just before the eruption.  This change is believed to be caused 
by the change in the geometrical size of the accretion disk ... It would be 
very interesting to find out what is the eclipse now, over 200 days since the 
last eruption."  Magnitude estimates of the eclipses should be made every 
minute and recorded to four places of the decimal of the JD.  The eclipses 
have the following elements (J. Smak 1993, Acta Atronomica, 43, 121):

      HJD Primary Minimum = HJD 2437638.82627 + 0.1769061898 * E,
                                       (+/- 8)       (+/- 30)

where E is the cycle number.

In addition to the eclipses, U Gem has a "hump,"  a photometric feature with 
an amplitude of 0.7 magnitude that lasts half of the orbital period and peaks 
at phase 0.85, where phase 0.00 is the middle of the eclipse.  Dr. Paczynski 
also suggests that observers monitor these "humps," particularly while U Gem 
begins its rise.  The humps disappear when the system brightens to magnitude 
12 and re-appear again after the outburst when U Gem becomes fainter than 
magnitude 12.

The hump is believed to be due to the "hot spot" created by the stream of 
material from the cool companion colliding with the outer edge of the 
accretion disk.  Dr. Paczynski writes further, "...little is known about the 
stability of this 'hump,' yet it provides a direct measure of the amount of 
energy released in the stream-disk collision.  It is not known is it constant 
between the eruptions, is it constant from year to year, and in particular, 
how does it look ... now, when U Gem has not erupted for over 200 days."

CORRECTION TO AAVSO ALERT NOTICE 196 - 2110+13 EF PEGASI

The location of the close companion to EF Peg should read 5.34 arcseconds away
at position angle 112 degrees (Howell et al. 1993, Publ. Astron. Soc. Pacific,
105, 579).  We thank Patrick Schmeer for bringing this correction to our
attention.


Observers are welcome to use our charge-free number (800-642-3883) to report
observations.  The answering machine is on nights and weekends for your
convenience.  We also encourage observers to send observations by fax at
617-354-0665 or by e-mail through the Internet at aavso@cfa.harvard.edu.

Again, on behalf of the ASTRO-2 Science Team and all of us at Headquarters,
my sincerest thanks to you for your dedicated efforts and valuable observations.

Good Observing!

Janet A.Mattei
Director

Keywords:
AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484