Alert Notice 800: Photometry needed for five YSO stars in support of spectroscopy

November 17, 2022

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Ruhee Kahar (University of Dundee) and colleagues at several institutions have requested AAVSO observers' assistance in monitoring five YSO stars in support of high-resolution spectra data obtained with CARMENES in a study of accreting young stars. The targets are given in the table below.

This campaign is underway now and ends on November 30.  

Kahar writes: "We are taking repeated high-resolution spectra of intermediate-mass young stars to study the velocities and temporal variability of accretion related lines in these objects. The sample of stars includes HAeBe stars and massive T Tauri stars that will evolve into A and B stars. The connection between both types is at present unclear and may be related to the magnetic activity of the future star. Previous observations of these objects also indicate some evidence of extinction by circumstellar material.

"We will be measuring the time variability (in velocity and relative intensity) of the emission lines to study the structure of the accretion columns. Non-axisymmetric structures are revealed as the star rotates. Using the archival data alongside this new data will also allow us to study the evolutionary status of the star-disc connection as well as to complete the gas emission information from the emission lines of the circumstellar material that crosses the stellar disc. This is a first-time exploration of the circumstellar environment in intermediate-mass young stars, where the mechanisms of accretion may deviate from magnetospheric and are poorly understood.

"These targets have all been observed by the AAVSO in the past, and we are [asking for AAVSO assistance] to get simultaneous photometry to complete the analysis.

"Since we are looking for rotational modulations in stars with rotational periods of a couple of days, daily observations would be best, but observations with cadences ~1-3 days are acceptable and, in the worst case, any observation during the spectroscopy run would be highly appreciated. The minimum acceptable S/N is greater than 30.

Professional spectroscopic observations are scheduled for November 18, 23, and 28. AAVSO coverage is requested for November 17-19, 22-24, and 27-29 UT, however, observations on all nights from now through November 30 wold be very welcome. "Repeated CCD/CMOS observations in many filters (priority order is VRIB) would be appreciated and can help to disentangle accretion from extinction events, but if this is not possible, a time series in a single filter would be very good too." Unfiltered data reduced to a zeropoint (CV/CR/CI/CB) are not appropriate for this campaign. DSLR data are not requested.

The researchers may want to see images if they need to recalibrate the data using field stars other than those selected as comparison stars. Please reduce and submit your observations to the AAVSO International Database as usual, but hold on to your images if possible. When the researchers see the data in the AID, some observers may be asked for their images; this would happen within about a month after the campaign ends. Observers are asked to make the exposures deep enough to show other objects in the image (but without saturating the target).

CARMENES is the Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs.

Name RA (2000) Dec (2000) Range Type
RY TAU 04 21 57.41 +28 26 35.6 9.3-11.7 V CTTS/ROT
UX ORI 05 04 29.99 -03 47 14.3 9.4-12.7 V UXOR
CO ORI 05 27 38.33 +11 25 38.9  9.9-12.8 V UXOR
RR TAU 05 39 30.51 +26 22 27.0 10.2-14.3 V UXOR
R MON 06 39 09.96 +08 44 10.2 10.7-13.2 V UXOR

The link on each name in the table goes to the VSX page for that target.

Charts with comparison stars for these targets may be created using the AAVSO Variable Star Plotter (VSP).

Please submit observations to the AAVSO International Database using the names given in the table.

This Alert Notice was compiled by Elizabeth O. Waagen using information provided by Ruhee Kahar.


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