Article from:Xingming Observatory
Initiator:Xing Gao（高兴）

About the Initiative

To amateur astronomers with fixed observation sites, I now invite you to join the global monitoring network for the recurrent nova T Coronae Borealis (T CrB) hosted by Xingming Observatory (MPC Code: C42, N86, N88, N89).

To join the monitoring network, one should have access to a fixed observation site and fixed observation equipment capable of continuously observing the target, T CrB. At least 20 images need to be taken per observation night, with the ideal scenario being all-night monitoring over an extended period.

Large-aperture telescopes are not a must, and even camera lenses are acceptable (though all-sky cams are not recommended due to their relatively low limiting magnitude). The optimal focal length is 400-1000 mm. We do not recommend using telescopes with very long focal lengths (e.g., SCs and RCs), as the field of view is too small. They may not be suitable for photometry due to insufficient comparison stars. Therefore, telescopes with apertures ranging from 80mm to 200mm, which are commonly used by amateur astronomers, are generally the most appropriate.

For more information about T Crb, please refer to the following websites:

https://www.aavso.org/recurrent-nova-science-tasks-observers-worldwide

http://xjltp.china-vo.org/recurrent_nova-schaefer.html (in Chinese)

http://xjltp.china-vo.org/tcrb_kepu.html (in Chinese)

Currently, historical observation data on the eruption process of this recurrent nova are very scarce. Based on previous similar models, we can only estimate that the nova will erupt within a year, with the full eruption process lasting several hours and potentially featuring a brief ‘plateau’ period. Consequently, the initial observation of the eruption process is of significant importance. This is why we have established a global monitoring network to invite both amateur and professional astronomers from around the world. We will collaborate with a team from Tsinghua University to compile and publish the observation results. If your data is cited, we will invite you to become a co-author of the resulting paper.

As mentioned above, the timely processing of the observation data is critical. We have developed a program that can perform photometry on your observation data locally on your computer in real-time. The processed data are then transferred to the server of Xingming Observatory. Since only data, not images, are transferred, the data size for one night potentially being only tens of kilobytes.

To use the program, the observer needs to take a few images first and send them to us. We will create an alignment template file (for the program to perform automatic photometry) for you.

Participation in the joint observation network is voluntary, and there is no mandatory requirement for how much time one needs to observe during the night. We encourage as many participants as possible and aim for a broad distribution of observations. Our goal is to produce scientifically valuable work and to connect with more individuals in this field. If you are interested in joining the network, please join the T CrB Global Monitoring WeChat group or email us at gaoxing8888@sina.com. Alternatively, you can add me on WeChat (User ID: firststar1974), and I will invite you to the group.

Xing Gao（高兴）
Xingming Observatory

About the target

The target for observation is T CrB, with coordinates RA= 15h59m30s and Dec=+25°55′ 13″. It also has other names in different catalogs, such as SAO 84129, HIP 78322, PPM 104498, GSC 2037:1144, B+26 2765, HD 143454, etc. The apparent magnitude is about 10.3.

We recommend a field of view of 1 degree by 1 degree. An FoV smaller than 0.5 degrees by 0.5 degrees may not be suitable for this work. (There are some exceptions — please email us for more details. If the FoV is too large (e.g. using a camera lens with a short focal length), image distortion may occur. Then, we suggest using appropriate partial readout when conducting observations, such as using #subframe 0.5 (for ACP scheduling). If you need guidance on the appropriate size of the partial readout, please email us for further discussion. If image file size is a concern, you may also use BIN 4 mode, as long as the program is able to perform photometry properly.

We recommend capturing images at a frequency of approximately 1 frame per minute, and capturing a frame less frequently than every 5 minutes is not advised. Additionally, we suggest taking flat, dark, and bias images daily. Although these fields are not required for this program, they are essential for future scientific data processing and calibration if the eruption is detected. Please ensure that the calibration fields match the captured images, namely BIN mode and temperature. Please retain the captured images for at least ten days.

The following figure is a reference image of the target (North is on the right).

The red circles C1, C2, C3, D1, and D2 in the picture are the comparison stars used by the program to perform differential photometry. Please make sure that these stars are present in the images you are taking. The following figure shows the position and brightness information of each star.

It is acceptable as long as the image you capture includes these stars. North does not need to be oriented to the right, and a mirrored image is also acceptable (e.g., if the camera is mounted at the primary focal point).

Why to monitor it?

Human understanding of recurrent novae is still quite limited. Monitoring T CrB represents an exceptional opportunity for amateur astronomers to contribute to a significant scientific endeavor. The details of its eruption can only be captured through very continuous monitoring. Many aspects of this work are unprecedented, making it a historically significant scientific project. Every day, professionals and amateurs worldwide are closely monitoring its activity, as evidenced by the online data from AAVSO. The race to be the first to detect its eruption is highly competitive.

Some screenshots about our program

The following is a graph published on the web page.

Q&A

1. Can I shoot with a 12-bit digital camera?

A: Yes, as long as the file is saved in a 16-bit fits format.

2. What filter should I use?

A: If it is a color camera, then just shoot directly. It is recommended not to add light pollution filters or other cut-off filters. If it is a monochrome camera, then please add the three-color R, G, and B filters for photography in front. If it is a photometric filter, you can use V, R, I or Sloan’s g’, r’, i’. You can also capture images without a filter. Please inform us what filter you are using anyway.

3. How long should the exposure time be?

A: First, locate to the previous atlas in the article and make sure you captured the right star, T CrB. Please make sure that T CrB is not saturated in the image. Ideally, the ADU (Analog-to-Digital Unit) value of T CrB should be around 10,000. It is necessary to reserve a certain amount of brightness increase space for it, since it is going to erupt.

The figure below shows that the maximum ADU value of T CrB is 7,152, with an acceptable signal-to-noise ratio of around 100.

4. How many photos should be taken continuously?

A: The more the better, preferably all night, but not less than 20 photos per night.

5. Is the focus required to be very accurate?

A: No, overly sharp stars are not conducive for the program to perform photometry. In some cases, appropriate de-focusing is even required, especially when using BIN4 mode. However, avoid defocusing to the point where the stars appear as circles. In principle, it is acceptable as long as the program can recognize the stars.

6. How many sites have already joined the network?

A: We will assign a unique number to each site (or individual) that successfully participates in the monitoring. Subsequently, the data collected will be published on our website. The current list of assigned numbers is as follows:

TW001 = Vancouver, Canada

TW002 = New Mexico, USA

TW003 = Chile

TW004 = Surrey ,Canada

TW005 = California ,USA

TE001 = Urumqi Xingming Observatory, China

TE002 = Yanqing, Beijing, China

TE003 = Wuding, Yunnan, China

TE004 = Yinchuan, Ningxia, China

TE005 = Pingliang, Gansu, China

TE006 = Zhangjiakou, Herbei, China

TE007 = Shijiazhuang, Herbei, China

TE008 = Qingyuan, Guangdong, China

TE009 = Xuyi, Jiangsu, China

TE010 = Strand, Norway

TE011 = Haba Lake，Ningxia, China

7. Can there be multiple equipment observing at the same site?

A: Indeed, the more data we have, the better. There is no conflict, and the data from multiple equipment can support each other. We welcome more observatories and individuals to join us, as this will strengthen our efforts significantly.

Disclaimer

Participation in this joint observation network is voluntary and conducted cooperatively. If you want to protect your own data and keep them proprietary, please withdraw voluntarily. We do not assume responsibility for disputes caused by the use of related data. While we will make every effort to maximize the value of your data, we cannot guarantee that your data will be used over others’. We will list the relevant participants or team members in the publication. (In principle, a team should not exceed three people).

The site can be a commercial remote observatory, but the name of the company or other non-astronomy-related organizations will not be mentioned. If a paper is ultimately published, the selection of co-authors will be decided by the paper’s first author. Neither I, Gao Xing, nor Xingming Observatory will participate in this decision, though we will recommend including individuals who have significantly contributed to the project. Based on past experiences, if the author is not affiliated with a professional astronomical team, the first author generally recommends that the author be affiliated with Xingming Observatory, but this will be at the discretion of the first author.

If the author of the paper wishes to use your observation data, please cooperate in protecting the relevant data during the exclusive period to avoid negatively impacting the publication of the paper. For any related issues not mentioned above, I, on behalf of the Xingming Observatory team, reserve the final right of interpretation and will actively coordinate. I hope to avoid any disharmony and thank you for your understanding and cooperation.

Initiative of T Crb Global Monitoring Network（Xingming Observatory）