Alert Notice 684: Photometry requested for campaign on V1491 Cyg

Note: This campaign is continued until 2040 (very longterm!).  -  Elizabeth O. Waagen, 16 April 2020

November 1, 2019

AAVSO Forum threads (scroll to the bottom of a thread for latest posts):
 - Campaigns and Observing Reports:
 - Young Stellar Objects:

Dr. Dirk Froebrich (University of Kent) has requested AAVSO observations to support their upcoming observations of V1491 Cyg. He writes:

"Background: We have recently discovered that the young variable star V1491 Cyg (situated in the Pelican Nebula IC5070) is periodically occulted by material in its circumstellar disk. Our light-curves indicate a period of about 180 days and occultations lasting 1-2 weeks. These obscurations could be caused by the Hill sphere of an orbiting protoplanet.

"We will be conducting a [four-week], high cadence, multi-wavelengths optical monitoring campaign (in UBVRIHa) of this source to map out the next occultation, which is predicted to occur in mid November 2019. Thus, our campaign will run from [1 November 2019] to [30 November 2019].

"We will observe the target using:

i) The University of Kent's Beacon Observatory (longitude ~1deg East).

ii) Our network of amateur astronomers who work with us as part of our HOYS-CAPS(*) citizen science project.

iii) Observations with the LCO (in particular the 1m telescope at the McDonald Observatory (longitude ~104deg West).

"Given the position of the object (highest right after sunset) we would like to request one set of images in all available filters per observer per night. We would like to request assistance from AAVSO observers to cover longitudinal gaps and to account for potential bad weather at our other observing sites.

"Observations: We request CCD or DSLR observations of the target as often as possible and in as many optical filters as are available. In particular we would like BVRI(RGB) observations, but U and Halpha are welcome as well if the equipment is available and the object can be detected.

"The brightness of the object outside occultations is: B~16.5-17.0, V~14.9-15.4, R~14.2-14.6, I~13.5-13.9; during the occultations the object will be about 0.8mag fainter in all filters. Thus, all the observations should be deep enough to detect the target star at all states with good signal to noise, as we do not know the exact behaviour of the object during this period (the star is intrinsically variable by +-0.5mag outside the occultations).

"All images should be dark and flat-field corrected. The field of view should be large enough to ensure a sufficient number of comparison stars is available to perform an accurate relative photometric calibration as well to allow us to estimate any colour terms in the photometry.

"Please stack individual images taken in the same filter per night for an improved signal to noise before submission, but only if they are taken no further apart than 2hrs. Images taken over a longer duration should be stacked separately.

"Data Submission: As this object is in IC5070, and thus part of our HOYS-CAPS citizen science project, the reduced images should be submitted in FITS format via our web-upload system (**). Once they are processed the photometry of all the stars in the images will be available immediately publicly via our web interface.

"To ensure accurate processing, the FITS header should contain information of the filter used, the total exposure time of the stacked images and the mid-point of the integrations in each stack."

"Observations should also be submitted to the AAVSO International Database using WebObs and the name V1491 CYG." Please be sure to include the space before the constellation abbreviation.

Charts with comparison stars for V1491 Cyg may be created using the AAVSO Variable Star Plotter (VSP).

"In case of any questions please contact the PI at or use the HOYS-CAPS facebook group(***)".


Coordinates (2000):  RA  20 51 04.65    Dec  +44 23 50.1   (from VSX)

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


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