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.
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.
Chart links are obsolete; 11/2013 create charts using VSP at http://www.aavso.org/vsp
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
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