V405 Peg (RBS1955)


SIMBAD RA2000: 23h 09m 49.33s, DE2000: +21D 35' 18.0"



MDM 2.4m finding chart (click to get the full resolution)


The comparison star is the star SE to the target labeled 14.49 (I-band magnitude)
A UBVI sequence of field stars is available in tabular form.
Finding chart, list of field stars, light curves and spectrum below are adapted from
Thorstensen et al. 2009, PASP 121, 465: V405 Peg: a nearby, low-luminosity cataclysmic binary

SDSS finding chart, photometry and high state spectrum

SDSS high state magnitudes: u=15.78 g=16.10 r=15.35 i=14.65 z=14.09
Low state magnitudes (Bessel): I=14.14, B ~ 17.9

Light curves (I-band) and optical spectra through high and low states
The orbital period is Porb = Pspec=4.263hrs

Low-state photometric period agrees with spectroscopic period.
No stable photometric pattern (I-band) observed in a high state. Photometric periods appear and disappear.

Photometric support for XMM-Newton observations

XMM-Newton is scheduled with start time 2009-12-29, UT18:51:56. The observations will last 44000 seconds, more than 12 hours, and cover almost three orbital cycles of the binary. The optical monitor onboard the satellite will be used in fast mode and serves as fast photometer in the ultraviolet. Supporting ground-based optical photometry helps to uncover the accretion state of the binary, update the optical ephemeris, and establish the broad-band spectral energy distribution from the optical to the UV and X-rays and thus uncover the true nature of the binary. Ideally, optical and X-ray observations are performed simultaneously, weather and visibility constraints may prevent this. We therefore ask for time-resolved, near-coincident observations in I- and B-bands during the period December 27/28 to December 30/31. The I-band shall be used for comparison with the large body of existing data, the B-band is expected to show the highest variability (orbital variability and transition between high, low and intermediate(?) states). The occurrence of high and low states cannot be predicted in advance and the transition time scale between different states is likely days.

Potential observers are kindly asked to go for the shortest observation times feasible depending on aperture and brightness of the target. Data can be sent directly to aschwope@aip.de (PI of the XMM-observations)


Clear skies and Merry Christmas.
Thankfully, Axel Schwope