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Alert Notice 656: Chandra observation date revised for XZ Tau and HL Tau

November 7, 2018: Further to AAVSO Alert Notice 654, the date and time of the Chandra observations of the T Tauri stars XZ Tau and HL Tau scheduled for 2018 November 15 have been revised to November 11 and 12.

Dr. David Principe (MIT) informs us that Chandra is now scheduled to observe the targets on:

2018 Nov. 11 17:37 - Nov. 12 00:01 UT
2018 Nov. 12 08:01 - Nov. 12 14:27 UT

As he said in AAVSO Alert Notice 654, "We request photometric observations in any optical band (preferably V, B, and/or R in that order) of the XZ Tau binary.

"It would be ideal to observe [XZ Tau] during...or within a few days of the Chandra observations. Its outburst state is not expected to change much on timescales of days and thus one or two observations per night would be useful in determining its accretion state (whether it is in outburst or not). The purpose of the Chandra observations are to identify signatures of accretion shocks on the surface of the star and thus determining its outburst state with optical photometry is helpful.

"...HL Tau is ~30" away from XZ Tau and is also a target of these Chandra observations. We request to include this object in the field of view of any XZ Tau photometric measurements if possible, however, this target is not a priority as it is not expected to display optical variability of the same type as XZ Tau. Near-IR J, H, K photometric measurements of XZ Tau and HL Tau could also be helpful but are not necessary."

For additional information about the target stars and this campaign, please see AAVSO Alert Notice 654.

Coordinates (2000, from VSX), Range, Type:
XZ Tau   R.A. 04 31 40.08   Dec. +18 13 57.1   10.4 - 16.62 B   CTTS/ROT
HL Tau   R.A. 04 31 38.47   Dec. +18 13 58.1   15.1 - 17.2: B   INT

Charts with comparison star sequences for XZ Tau and HL Tau may be created using the AAVSO Variable Star Plotter (VSP).

Please submit observations to the AAVSO International Database using the names XZ TAU and HL TAU.

AAVSO Forums: This campaign is the topic of the AAVSO Campaigns and Observing Reports forum thread https://www.aavso.org/xz-tau-hl-tau-chandra-campaign

and the AAVSO YSO forum thread https://www.aavso.org/xz-tau-hl-tau-chandra-campaign-0

This AAVSO Alert Notice was compiled by Elizabeth O. Waagen using material provided by Dr. David Principe.

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