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Alert Notice 406: Observing Campaign to Monitor Magnetically-Active Dwarfs for Long-Term Variability

October 7, 2009
 

The observers of the AAVSO are asked to participate in a long-term photometric monitoring campaign on a number of magnetically active dwarf stars, requested by Dr. Styliani (Stella) Kafka of the Department of Terrestrial Magnetism, Carnegie Institute of Washington.  She requests long-term monitoring of these targets with an observing frequency of one observation every three days taken with one or more filters. When multiple filters are available, the preferred observations are (in order of precedence): Rc, V, Ic, and B.  Please observe such that you obtain a signal to noise of at least 50 (100 or higher is preferred).

These objects are all nearby dwarfs known or suspected to have magnetic activity, primarily of the UV Ceti (flare star) or BY Draconis subtypes. Long-term photometric monitoring of these objects will be used in conjunction with other multiwavelength observations from ground-based facilities including the Magellan 6.5-meter and DuPont 2.5-meter telescopes in Chile to understand the long-term magnetic activity cycles of these stars.  Such a study can reveal information about the physical natures of these stars, but also about their near space environments and habitability for life.

These objects are red, and the variability amplitudes are low, often well below 0.1 magnitudes.  The long-term variability due to stellar activity cycles may be much lower. Photometric accuracy rather than the number of observations are key to the success of this project. Unaccounted-for atmospheric effects such as extinction will likely overwhelm any long-term signal from these stars. Observers are strongly urged to fully calibrate their systems and to carefully reduce and transform their photometry to standard photometric passbands, including corrections for airmass/atmospheric extinction. 

Because of the long-term nature of this project, observers are asked to select one or more targets from the list below that are best suited to their system, and to add them to their observing schedules at a low priority. One observation every few days will be sufficient to trace the long-term behavior.  Intensive time-series is not required, although observers may detect rapid, large-amplitude variations occurring in the flare stars; if you believe a flare is occurring during your exposure, please indicate this in the comments field when submitting data. Note that flares will have much larger amplitude at bluer wavelengths.

At the present time, only a small number of these objects have comparison stars within half a degree: V998 Ori, YZ CMi, NSV 4776, and NSV 22079. We recommend beginning observations with these stars, and then checking the information website (given below) to see which stars have updated sequences.

Please also note that the majority of these stars are high proper motion systems.  Charts generated with AAVSO VSP may not accurately reflect the current positions of these objects.  If you perform automated aperture photometry of your exposures, please verify that the object is in the expected position.  We also request that you save your reduced frames for future analysis.  We may request that you submit your frames to the AAVSO website or directly to Dr. Kafka at some point.

This campaign is being organized at AAVSO Headquarters by Dr. Matthew Templeton on behalf of Dr. Kafka.  For more information, news updates, sequence information, and background on this project, please see the AAVSO information page at

[broken link]

http://www.aavso.org/news/kafka_2009.shtml        

Please contact Matthew Templeton (matthewt at aavso.org) for AAVSO- or other observing-related questions, and Stella Kafka (stellakafka at gmail.com) for specific science- or project-related questions.

Table 1: List of targets for Alert Notice 406.  Note that the RA/Dec will not include proper motion (if any) since 2000.


Name                  RA(J2000)    Dec(J2000)    Mag./range  Band
-----------------------------------------------------------------
NSV 15022            00:06:42.70  -07:32:35.0  13.74 ( ? )    V
YZ Cet               01:12:30.60  -16:59:56.0  12.10 ( ? )    V
TZ Ari               02:00:15.30  +13:03:40.0  12.26 ( ? )    V
NSV 15849            03:57:28.70  -01:09:34.0   8.06 (0.1)    V
DY Eri               04:15:21.70  -07:36:37.0  11.17 ( ? )    V
NSV 16153            04:42:55.77  +18:57:29.4   9.98 (0.034)  V
NSV 16181            04:52:05.70  +06:28:36.0  13.0 - 13.7    P
NSV 2075             05:31:27.39  -03:40:38.0   7.96 (0.008)  V
V0998 Ori            05:32:14.70  +09:49:15.0  11.48 ( ? )    V
AP Col               06:04:52.10  -34:33:36.0  13.4  ( ? )    V
YZ CMi               07:44:40.20  +03:33:09.0  11.12 ( ? )    V
NSV 4776             10:12:03.40  -02:40:26.0  10.63 ( ? )    V
ASAS J101218-0344.8  10:12:17.66  -03:44:44.3   9.27 (0.011)  V
NSV 18415            10:28:55.60  +00:50:28.0   9.63 - 9.68   V
RY Sex               10:36:01.20  +05:07:13.0  12.55 ( ? )    V
EE Leo               10:50:52.10  +06:48:29.0  11.64 - 11.7   V
CN Leo               10:56:28.90  +07:00:53.0  13.54 ( ? )    V
NSV 19498            12:50:43.60  -00:46:05.0   8.46 ( ? )    V
FN Vir               13:00:33.50  +05:41:08.0  13.37 ( ? )    V
EQ Vir               13:34:43.20  -08:20:31.0   9.31 ( ? )    V
NSV 6329             13:35:24.70  -00:23:30.0  10.26 - 10.33  V
NSV 6431             13:45:37.70  +14:54:43.0   8.46 - 8.5    V
NSV 20124            14:30:47.70  -08:38:47.0  10.81 (0.6)    B
HN Lib               14:34:16.80  -12:31:10.0  10.3 - 10.33   V
ksi Boo              14:51:23.40  +19:06:02.0   4.52 - 4.67   V
NSV 6884             15:00:43.60  -11:07:43.0   9.47 - 9.54   V
HO Lib               15:19:26.80  -07:43:20.0  10.56 - 10.58  V
V2306 Oph            16:30:18.10  -12:39:45.0  10.05 - 10.1   V
NSV 8176             17:05:16.50  -05:04:45.0  10.06 ( ? )    V 
NSV 21919            17:25:45.20  +02:06:41.0   7.51 - 7.56:  V
NSV 22079            17:28:39.94  -46:53:42.6   9.37 (0.008)  V
NSV 10167            18:05:07.59  -03:01:52.6   9.28 - 9.43   V
V2391 Oph            18:05:27.30  +02:30:00.0   4.14 - 4.16   Hp
NSV 10635            18:19:50.90  -01:56:19.0   9.65 - 9.69   V
V1285 Aql            18:55:27.40  +08:24:09.0  10.2  ( ? )    V
HU Del               20:29:47.60  +09:41:18.0  13.04 ( ? )    V
OQ Del               20:39:37.70  +04:58:19.0   7.88 (0.04)   V
NSV 13417            20:56:46.70  -10:26:02.0  11.4  ( ? )    V
IL Aqr               22:53:16.70  -14:15:49.0  10.15 - 10.19  V
BR Psc               23:49:12.50  +02:24:04.0   8.93 - 9.03   V

AAVSO participation in this project is important and your help will be greatly appreciated!

Clear skies, and Good observing,

Matthew Templeton
AAVSO

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