Collaborations now have their own page! This is your start point for all information on these campaigns.
August 1, 2013: Dr. Hans Moritz Guenther (Harvard-Smithsonian Center for Astrophysics) has requested nightly observations of the classical T Tauri star AA Tau in order to schedule x-ray observations with XMM-Newton that have been planned for between 2013 August 15 and September 15.
The purpose of the AAVSO observations is to determine whether AA Tau is at a suitable magnitude for the satellite observations. Taurus is difficult to observe during this time period but that is exactly why AAVSO assistance is needed! AA Tau is a morning object, and also, many of the professional ground-based telescopes are offline because of the US southwest monsoon season. Since it is critical to know the brightness of AA Tau, your observations will be truly essential.
Nightly visual and snapshot (not more than once per night) observations beginning now and continuing through September 20 are needed. Coverage beginning ahead of the XMM window is requested because there is a one- to two-week lead time for the target to be inserted into the telescope schedule. Continuing the nightly observations a few days beyond the end of the XMM window will give better optical context for the x-ray data. AA Tau ranges between ~12.8V and ~16.1V; since December 2011 or earlier it has been at ~14.5V. The most recent observation in the AAVSO International Database shows it at 14.779V on 2013 Feb 5 (JD 2456328.75602) (J. Roe, Bourbon, MO).
Dr. Guenther writes, "AA Tau is a classical T Tauri star in the Taurus-Auriga star forming region. It is surrounded by a thick accretion disk. Material is falling from the accretion disk onto that star. In the case of AA Tau this disk is seen nearly edge-on. For decades the light curve of AA Tau showed regular eclipsing events when the accretion funnel, that connects the star and the disk, rotated through the line of sight. However, earlier this year J. Bouvier and his group found that this behavior changed dramatically: AA Tau now seems to be deeply absorbed all the time (V band 14.5 mag). In collaboration with this group we will perform X-ray observations of AA Tau with the XMM-Newton satellite...
"[Your observations are needed] so we can make sure that is it still in the low state when the XMM-Newton observations happen. Observations in calibrated bands (e.g. V) are preferred, but not required. [High] precision is not required, since even data with large uncertainties should allow us to check if AA Tau is at 14.5 mag or at 12.8 mag...Fainter-than observations of <13.0 or fainter will also be useful to us. Your help with this project will be greatly appreciated."
Our colleague Bill Herbst writes "Rachel Pedersen of Bates College and I have obtained time on the SMARTS 1.3 and 1.5 m for the entire month of September to observe T Ori, once per night. It would be WONDERFUL if the AAVSO could announce a campaign on this star in support of our measurements. We would basically like as much photometry as could be obtained. Accuracies of about 0.1 mag are fine, so visual observers can be included."
Continuing Collaboration on T Tau Stars
Darryl Sergison (University of Exeter) has requested AAVSO assistance with a campaign he is carrying out on five T Tauri stars. This study is the one for which AAVSO observers carried out a preliminary campaign last year (see Alert Notice 473 and Special Notice #306). The star list is revised and expanded from last year's list of targets. This campaign will run from now at least through the end of the 2013-2014 observing season.
This is part of an on-going study into the nature of pre-main-sequence low mass stars, using time series optical spectroscopy and UV-Visual-IR photometry and offers a great opportunity for professional-amateur collaboration as the objects (with V magnitudes of 10 - 13) are well within the reach of photometry by small telescopes. Amateur observations are uniquely useful in the study of chaotically variable young stars as they offer crucial datapoints in the light curve between observations made by professional telescopes.
Investigations include a range of phenomena with characteristic timescales of months to tens of minutes, and filtered CCD measurements in any of B, V, Ic, or Rc would be great on any of these timescales. Low cadence (nightly or twice a night) is useful, higher cadence (hourly or long time series) is better! Unfiltered is of less use due to the difficulties with system response and changing air-mass. Visual estimates ranging from monthly to twice in a night would be great. All contributing observers will be acknowledged in published papers.
|V1068 TAU||12.60 - 13.21V||R=11.8||K7V|
Monitoring requested for developing planetary systems dust production study
Dr. George Rieke (University of Arizona) and colleagues have requested AAVSO assistance in monitoring four stars with developing planetary systems. The targets are RZ Psc, HD 15407A, V488 Per, and HD 23514. This campaign is similar to the one conducted in 2013 (see AAVSO Alert Notice 482).
Dr. Rieke writes: "We have obtained 130 hours of time on the Spitzer Space Telescope to continue monitoring planetary debris disks for variability. We are asking for help from AAVSO for this program.
Debris disks - systems of dust and particles associated with planetary systems - are most easily observed from the infrared emission of their dust when it is warmed by the star, although a small number have also been observed in scattered emission, mostly by HST. They are a powerful approach to understanding planetary systems and their evolution because they can be detected at all phases of the development of a planetary system, and to large distances. Hundreds of them are known from IRAS, ISO, Spitzer, WISE, and Herschel. Among these hundreds, there are about a dozen where there is evidence that massive collisions are occurring right now, collisions that are building planets in much the same way that a large body added most of its mass to that of the Earth and created the Moon as a byproduct when the Solar System was young... A paper from Science describing the most thoroughly studied such system [may be found at the link given at the end of this notice]. A second paper on a larger number of variable debris disks has been submitted and we have received the referee report; the necessary revisions will be complete soon for final publication.
A key part of our program is to obtain optical photometry of the same stars that we are observing in the infrared under the Spitzer program. The optical data are needed to verify that any changes we see in the infrared are not just driven by changes in the brightness of the star, but are truly due to changes in the structure or dust content of the debris disk. AAVSO observers provided this support for our previous program, as summarized in the paper about to go back to the journal after refereeing; all of those who contributed data are co-authors of the paper.
"We request AAVSO to take similar observations for the new program. The table below lists the stars we are observing and basic information about them, and the two visibility windows for Spitzer (all observations will be obtained within the range of dates indicated)."
This campaign begins immediately and runs in two segments, now through May and September through December.
|Target||SpT||Age||Vmag||R.A. (2000)||Dec. (2000)||Spitzer visibility windows in 2015|
|(MYr)||1st Segment / 2nd segment|
|RZ Psc||KOIV||35||11.29||01 09 42.06||+27 57 01.95||Mar 14-Apr 24 / Oct 10-Nov 20|
|HD 15407A||F5V||80||6.95||02 30 50.66||+55 32 54.2||Apr 05-May 24 / Nov 07-Dec 28|
|V488 Per||KOIV||60||12.83||03 28 18.68||+48 39 48.2||Apr 17-May 30 / Nov 15-Dec 31|
|HD 23514||F5V||150||9.43||03 46 38.40||+22 55 11.2||Apr 18-May 26 / Nov 13-Dec 23|
Dr. Rieke and AAVSO recognize that all of these targets will be very near conjunction between now and the end of May, and so may be extremely difficult if not impossible to observe from the ground until nearly the end of the first segment. However, they are all observable with Spitzer during the first segment because of its orbit. Any morning observations that you are able to make will be greatly appreciated! During the second segment, the stars will be much better placed for observations from the ground; these observations will also be greatly appreciated. We will issue a Special Notice to remind observers before the second segment begins.
Observations in V are requested, with a S/N of about 100 so that the accuracy will be 1-2%. Observations should begin at least one week before the visibility window opens and finish one week after the window closes. No specific comparison stars are assigned for each target, but observers are requested to use only those in the sequences available via the AAVSO Variable Star Plotter. It is essential that observers report the comparison stars used when submitting their observations to the AAVSO. Observations should be submitted to the AAVSO International Database using the names RZ PSC, HD 15407A, HD 23514, and V488 PER, respectively.
The paper from Science may be found here:
Added note by section leader: There are several interesting articles on RZ Piscium, and this one at Astronomy and Astrophysics has links to a few others by the same authors.