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."
Monitoring requested for dust production study in developing planetary systems
Huan Meng and Dr. George Rieke (University of Arizona) have requested AAVSO assistance in monitoring three bright stars with developing planetary systems. The stars have been observed with NASA's Spitzer Space Telescope to have varying levels of dust in the circumstellar disk. These varying levels are thought to be produced through collisions among the asteroid-size debris in the disk. AAVSO monitoring is requested to make certain that the variations are not caused by variability in the stars themselves and for correlation with Spitzer data being obtained. For a more comprehensive explanation of the basis for this campaign, please see their article.
This campaign begins immediately and runs in two segments, now through May and September through December. The targets are BD+20 307, HD 15407A, and HD 23514; two are 9th magnitude in V and one is 7th in V. For each target the coordinates, basic photometry, desired time coverage, and comparison star information are given below. Observations in V are requested, with a S/N of about 100 so that the accuracy will be 1-2%. The comparison stars have been chosen to be within the same field of view as the variable.
TARGET 1: BD+20 307
Coordinates: R.A. 01 54 50.34 Dec. +21 18 22.5' (J2000)
B = 9.5, V = 9.0, R = 8.7
Desired Time Coverage: 2013 ASAP - April 21; September 24 - November 17
Comparison star for BD+20 307: choice between two unnamed stars:
12th magnitude unnamed star
Coordinates: R.A. 01 54 45.78 Dec. +21 16 55.1' (J2000)
V = 12.45
separation on the sky 1.8'
magnitude difference 3.4
or 10th magnitude unnamed star
Coordinates: R.A. 01 54 27.38 Dec. +21 10 46.7' (J2000)
V = 10.75
separation on the sky 9.3'
magnitude difference 1.75
TARGET 2: HD 15407A
Coordinates: R.A. 02 30 50.66 Dec. +55 32 54.2 (J2000)
B = 7.4, V = 7.0, R = 6.7
Desired Time Coverage: 2013 ASAP - May 14; October 14 - December 18
Comparison star for HD 15407A: HD 15407B
Coordinates: R.A. 02 30 48.6 Dec. +55 33 06.4 (J2000)
V = 9.60
separation on the sky 21"
magnitude difference 2.7
TARGET 3: HD 23514
Coordinates: R.A. 03 46 38.40 Dec. +22 55 11.2 (J2000)
B = 9.9, V = 9.5, R = 9.2
Desired Time Coverage: 2013 ASAP - May 17; October 21 - December 14
Comparison star for HD 23514 (BD+22 550): BD+22 552
Coordinates: R.A. 03 46 47.06 Dec. +22 54 52.43 (J2000)
V = 10.76
separation on the sky 2'
magnitude difference 1.3
Charts for these targets may be created using the AAVSO Variable Star Plotter. Observations should be submitted to the AAVSO International Database using the names BD+20 307, HD 15407A, and HD 23514, respectively. Regular observations of these stars during these intervals will be very important in analyzing the complex behavior of these systems. All contributions will be appreciated by the astronomers, and continuous monitoring especially so. The astronomers have indicated that observers who have done a significant amount of meaningful work would be co-authors of the resulting paper.
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."
Dr. Hans Moritz Guenther (Harvard-Smithsonian Center for Astrophysics) has requested nightly observations of the classical T Tauri star BP Tau in support of upcoming Chandra X-ray observations in his study of the accretion processes underway in this star.
Dr. Guenther writes: "... BP Tau is a classical T Tauri star in the Taurus-Aurigae star forming region. It is surrounded by a thick accretion disk. Material is falling from the accretion disk onto that star and we want to study this accretion shock and its interaction with the other layers of the star. The accretion shock is very hot (2-4 Mio Kelvin) and can be best seen in X-rays, but support from optical observers is needed. Specifically, we want to find out (1) if the X-ray spot is seen at the same time as bright or dark spots on the stellar surface, and (2) if the optical brightness changes, when the X-ray flux suddenly goes up or down due to changes of the rate of accretion or stellar flares. To do all this we need optical light curves over several weeks, so that we can see the rotational modulation and the average fluctuation in the light curve. For this we ask for the help of the AAVSO.
"BP Tau was observed with the XMM-Newton satellite a few years ago and it is (after TW Hya) the second X-ray brightest classical T Tauri star in the sky. Now, we will observe BP Tau with Chandra for 9 days. This will be the longest X-ray exposure ever obtained for a young star. Unfortunately, the Chandra satellite is ageing and very restricted on where it can point on the sky, so the observation has to be split over several months. Precise times (UT) for observation are:
Dec 22 22:52 through Dec 23 10:00
Dec 25 14:46 through Dec 26 06:06
Dec 27 17:58 through Dec 28 16:18
Dec 30 08:20 through Dec 31 12:00
Jan 02 07:09 through Jan 03 07:09
Time-series observations (multicolor or V) are requested for these windows for correlation with the Chandra observations (one to two observations per night outside of these windows). These high-cadence observations would be extremely valuable and very much appreciated. Regarding the cadence, Dr. Guenther writes: "With X-rays we record the arrival time of every single photon which means that we can decide on the time binning after the observation. Thus, a high cadence would be good, but of course there is an upper limit because it's not a very bright star."
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|