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Observations of V420 Aur (HD 34921) needed to support spectroscopy

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發表於 2016-10-5 06:35:19 | 顯示全部樓層 |閱讀模式
AAVSO Alert Notice 554

October 3, 2016

Observations of V420 Aur (HD 34921) needed to support spectroscopy


Marcella Wijngaarden and Kelly Gourdji (graduate students at the
University of Amsterdam/Anton Pannekoek Institute for Astronomy)
have requested AAVSO observers' assistance in providing optical
photometry in support of their high-resolution spectroscopy with
the Mercator telescope + Hermes spectrograph in La Palma 2016
October 7 through 17.

They write: "[V420 Aur (HD 34921) is] the optical Be star that is
part of a peculiar High Mass X-ray Binary...[that exhibits highly]
complex and variable spectra...it is difficult to construct a
physical model of this HMXB system. Though based on these
observations, the system is thought to contain a B[e] star with a
dense plasma region, an accretion disk around a neutron star, a
shell and circumstellar regions of cold dust. It has been over a
decade since the last spectra were taken, and, given the highly
variable nature of this star, we expect new observations to yield
new information that will contribute to a better understanding of
this system."

Observations in BVRI are requested beginning immediately and
continuing through October 24. The PI's write: "Observations using
other filters will be useful as well as long as there are multiple
observations in these bands. In all cases, timeseries in a few
bands (i.e. BVRI) are preferred over single/a few observations in
the other bands as it is the variability on relatively short
timescales that is most important. Unfiltered observations are in
this case also useful but preferably only when they are available
for multiple nights (in order to cross-match with other
observations).

"The target is bright so exposures should be long enough to reach
good signal to noise in order to see the small variability
amplitude but without saturating the target/comparison stars." With
a range of V = 7.35 - 7.51, V420 Aur is a good candidate for PEP,
DSLR, and CCD photometry. Its very small amplitude makes it a
challenging target for visual observations.

The PI's continue: "We will study the variability on several
timescales, so observations starting from a few per night to high
cadence timeseries are useful. Especially in the [October 7-17]
period the higher rate the better.

"Observations starting as soon as possible are ideal, for these the
requirements are the same as above...We request the same
observations until one week after the spectroscopic observing
run...[so] that hopefully we have enough to phase fold the data."

Coordinates (2000.0): R.A. 05 22 35.23  Dec. +37 40 33.6

Charts with a comparison star sequence for V420 Oph may be created
using the AAVSO Variable Star Plotter (VSP,https://www.aavso.org/vsp).

Please submit observations to the AAVSO International Database
using the name V420 OPH.

This campaign is being followed on the AAVSO Observing Campaigns
webpage (https://www.aavso.org/observing-campaigns). A thread has
been created on the Campaigns and Observation Reports forum at
(https://www.aavso.org/content/v420-aur-hd-34921-observing-campaign).


This AAVSO Alert Notice was compiled by Elizabeth O. Waagen.

----------------------------------
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ALERT NOTICE ARCHIVE AND SUBSCRIPTION INFORMATION

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