Alert Notice 843: Photometry of R Mon, UX Ori, CO Ori, RR Tau, and RY Tau needed now in support of spectroscopic campaign

November 21, 2023

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Ruhee Kahar (University of Dundee (UD)) and Drs. Aurora Sicilia-Aguilar (UD), Justyn Campbell-White (European Southern Observatory), Ignacio Mendigutia (CAB,CSIC-INTA), Veronica Roccatagliata (Univ. Pisa), and Scott Gregory (UD) request AAVSO observers' assistance in monitoring five Young Stellar Objects - RY Tau, UX Ori, RR Tau, CO Ori, and R Mon - in support of spectroscopy being obtained with the CAHA 3.5-m telescope at Calar Alto Observatory (CARMENES) in a study of accreting young stars.

Spectroscopy observations will be carried out at Calar Alto on November 21, 22, and 23.

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."

Simultaneous photometric coverage is requested to determine the status of the source during the observational period, and " complete the spectral information, including the presence of obscuring dust from the inner disk, and confirming rotational periods. Although intermediate-mass stars lack the cold spots of low-mass stars, their rotation can be measured due to the accretion spots and occultations by inner disc material at the corotation radius, which are very common."

CCD observations are requested beginning immediately and continuing through December 10. DSLR photometry is also valuable, particularly if the observations are transformed to Johnson/Cousins magnitudes.

Multiple observations per night are needed. Alternating among available filters would be appreciated if possible as they "...can help to disentangle accretion from extinction events". If that is not possible, time series in a single filter would also be very good. Prioritization of filters is VRIB. A minimum S/N > 30 is needed.

***Observers are requested to keep their images in case they are needed by the astronomers. Information will be posted in the forum threads above in a timely manner along with instructions on how and where to send them.***

Spectroscopy is not requested for this campaign.

CARMENES stands for Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrographs.

Targets (all are of equal priority)

Object RA (2000) Dec (2000) Range (from VSX) 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
RR TAU 05 39 30.51 +26 22 27.0 10.2-14.3 V UXOR
CO ORI 05 27 38.33 +11 25 38.9 9.9-12.8 V UXOR
R MON 06 39 09.96 +08 44 10.2  10.7-13.2 V UXOR

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

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

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen using material supplied by Ruhee Kahar.


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