Alert Notice 822: HM Lup photometry and spectroscopy requested

May 1, 2023

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Ph.D. student Antonio Armeni (University of Tuebingen) has requested AAVSO observers' assistance in obtaining photometry and spectroscopy of the classical T Tau star HM Lup in support of observations with TESS scheduled for 2023 May 4 - June 2.

Armeni writes: “HM Lup is a young M-type star that accretes material from a circumstellar disk through a magnetosphere. With its accretion rate of 2.5 · 10−9 M⊙/yr in 2012 (Manara et al. 2022), HM Lup is among the strongest accretors in Lupus. The optical spectrum of HM Lup is rich in emission lines typical of a Classical T Tauri Star...

“Due to the accretion process, HM Lup is a very active star and it is both photometrically and spectroscopically variable. Therefore, it is essential to study this object using a multi-wavelength approach, by means of simultaneous observations in different spectral regions. Photometric data in the BVRI bands are crucial to study the accretion variability of this target. Spectroscopic observations of selected emission lines, such as Hbeta, He I 5876 + Na I D lines, the Mg I / Fe II lines around 5165-5185 Å, and Fe II 4924 and 5316, would be important to study the structure of the accretion flow."

BVRI observations (B and V of higher priority than R and I) are requested beginning immediately and continuing at a cadence of one to several times per night during the TESS observation window. HM Lup has a range of 14.45 - 14.95 V. The most recent observations reported to the AAVSO are from 2021 and showed it at magnitude 14.41 V +/- 0.027 on 2021 Sep. 28.97378 UT (J.-F. Hambsch, Mol, Belgium).

High-resolution spectroscopic coverage, especially of the lines indicated above, is also requested.

Coordinates (J2000): R.A. 15 47 50.63  Dec. -35 28 35.4   (from VSX entry for HM Lup)

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

Please report photometric and spectroscopic observations to the AAVSO International Database and the AAVSO Spectroscopic Database, respectively, using the name HM LUP.

This Alert Notice was compiled by Elizabeth O. Waagen using information provided by Antonio Armeni.


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