Fwd: XRT (and EIS?) obs of stars

hi Leon,

sorry, I didnt get your message right away due to an cerebral blockage in my
mailer. Hence my message partially dittoing yours.

I could, on say, a monthly basis, do a "look-ahead" scan of the solar path
in the sky to look for strong, steady Xray sources which will pass thru the
XRT FOV. They need not be eclipsed by the Sun, since passing thru the
off-limb polar regions would be interesting as well, I would think.
Sound worthwhile? I think it is worth an experiment at some point at least.

steve

Begin forwarded message:

From: Peter Smith <plsmith@cfa.harvard.edu>
Date: November 28, 2006 3:00:06 AM JST
To: Steve Saar <saar@head.cfa.harvard.edu>
Cc: Leon Golub <lgolub@cfa.harvard.edu>, Ed DeLuca <edeluca@cfa.harvard.edu>, llundquist@cfa.harvard.edu, Mark Weber <mweber@head.cfa.harvard.edu>, Jay Bookbinder <jbookbinder@cfa.harvard.edu>
Subject: XRT (and EIS?) obs of stars

Here are some possibilities:

Crab Nebula ~ June 14 (almost 5 Rsun away, but maybe worth the effort)
I Gem about June 21 G5 III
WY Gem June 23 K5
Rho Leo Aug 28 B1 I
CN Leo Sep 4 Cataclysmic Variable
HD144608 Nov 25 G3 III
Nu1 Sgr Jan 1 K2 V
HD206301 Feb 10 G2 IV
38 Aqr Feb 19

I haven't checked trajectories well, but 38 Aqr and Rho Leo should pass
behind the sun.

Peter

Steve Saar wrote:

hi again,
it seems that since omega sco is not a major Xray source, if XRT misses it it is not a great loss. (Its more useful for the EIS folks, given its UV continuum). We should definintely be on the lookout for other stellar eclipses tho- any source with a nice, well defined Xray continuum could potentially be used as a flashlight thru solar coronal structures, which would
absorb the stellar Xrays in selected lines, permitting diagnosis of the absorbing solar features (densities, temperatures, sizes) in the best cases.
Is there any quicky program that predicts the RA DEC of the sun for any give date/time? One could potentially cross match this with eg, the Rosat catalog to look for bright Xray eclipsers.
cheers,
steve

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Cc: Steve Saar <saar@head.cfa.harvard.edu>, Leon Golub

<golub@head.cfa.harvard.edu>, Ed Deluca <deluca@head.cfa.harvard.edu>

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From: Loraine Lundquist <llundquist@cfa.harvard.edu>
Subject: Re: XRT (and EIS?) obs of omega Sco
Date: Mon, 27 Nov 2006 21:03:41 +0900
To: Peter Smith <plsmith@cfa.harvard.edu>

Peter,

I regret to say that our observation table for omega Sco was interrupted due to errors by XRT. We will note the times for the other stellar observations -- but please remind us again when they come around.

Loraine

On Nov 23, 2006, at 2:50 AM, Peter Smith wrote:

Leon, Ed, Mark:

I've refined my calculations (but am still working from interpolations on
a paper plot).

Omega Sco enters extreme NE corner of FOV at ~02:15 UT on November 25
Omega Sco passes behind the sun at position angle 21.3 degrees (about
   eleven o'clock) at ~5:50 UT
Omega Sco reappears at PA -40.6 (about one thirty o'clock) at ~13:00 UT
Omega Sco leaves the FOV at ~15:00, at which time it is about 0.75
   solar radii (Ro) above Sun center.

Assumption: FOV is 32 arcmin square

John Raymond says that Omega Sco is likely to have a soft x-ray spectrum.
He and I don't know our way around the ROSAT catalog: he suggests that
we ask Steve Saar for an opinion.

Omega Sco moves one solar diameter in ~12.75 hours: 2.5 arcsec/sec.

I don't know how big EIS's "slots" are, but I were EIS, I'd position a
slot about 0.1 Ro above the limb for 2 one-hour periods:
04:30 - 05:30 UT 0.6 Ro to east, 0.9 Ro to north
13:30 - 14:20 UT 0.8 Ro to west, 0.75 Ro to north
and let the star drift across the slit.

If this doesn't work, we should remember 38 Aqr (~Feb 20) and rho Leo
(~30 Aug). These are O or B; I don't know whether the have a soft X-
ray spectrum.

And there are some cooler stars suggested by John. I'll talk to Steve.

Peter

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Peter L. Smith - Harvard-Smithsonian Center for Astrophysics
60 Garden Street, MailStop-50, Cambridge, MA, 02138 USA
   office: 617-495-4984 - mobile: 617-851-6924
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