Columbia University Astronomy and Astrophysics

Search for Transient Source IGR J18325-0756
J. P. Halpern

Lutovinov et al., ATel #154 described the basic variability properties of this source, which rose to as high as 40 mCrab. It is cataloged in Bird et al. 2006.

The field is blank in ROSAT and ASCA images. Images were obtained on the MDM 1.3m in R and in H-alpha. Unfortunately the shutter got stuck in the open position, which is why the bright stars are trailed. The small circle of radius 0.7' corresponds to the nominal 1&sigma error. Click on each image to get its jpeg file.

I obtained spectra of the two brightest stars inside the small circle using the MDM 2.4m. They are a G star and an M star, respectively. A very red star near the SE edge of the inner circle can be recognized because it is brigher in R than in H-alpha. Its coordinates are (J2000) 18h 32m 29.81s, -07°, 56' 47.4". It has USNO and 2MASS magnitudes R1=18.14, R2=19.90, I2=13.85, J=9.34, H=7.68, K=6.89. I obtained a spectrum of it on the MDM 2,4m, showing that it is an M star. So, no luck in identifying the source so far.

Landi et al., ATel #1423 reported a Swift X-ray source at (J2000) 18h 32m 28.3s, -07°, 56' 40.4", which I already knew about. I can see a faint star consistent with the coincident 2MASS star that they mention.

MDM 1.3m R-band (4.3' x 4.3')
(J2000) 18h 32m 28s, -07° 56' 24"
MDM 1.3m R
MDM 1.3m H-alpha


IGR J18325-0756, A. Lutovinov, S. Shaw, L. Foschini, J. Paul, ATel #154 (2003)

The Second IBIS/ISGRI Soft Gamma-ray Source Catalog, A.J. Bird, et al., Ap.J., 636, 765-776 (2006)

A Swift/XRT follow-up observation of the INTEGRAL source IGR J18325-0756, R. Landi, N. Masetti, V. Sguera, A. Bazzano, M. Flocchi, A. J. Bird, A. J. Dean, ATel #1423 (2008)



Last modified: March 14, 2008 Transient X-ray Source Page