NGC752XMM - NGC 752 XMM-Newton X-Ray Point Source Catalog
Very little is known about the evolution of stellar activity between the ages of the Hyades (0.8 Gyr) and the Sun (4.6 Gyr). To gain information on the typical level of coronal activity at a star's intermediate age, the authors have studied the X-ray emission from stars in the 1.9 Gyr-old open cluster NGC 752. They analyzed a ~ 140 ks Chandra observation of NGC 752 and a ~50 ks XMM-Newton observation of the same cluster. They detected 262 X-ray sources in the Chandra data and 145 sources in the XMM-Newton observation. Around 90% of the catalogued cluster members within Chandrás field of view are detected in the X-ray observation. The X-ray luminosity of all observed cluster members (28 stars) and of 11 cluster member candidates was derived. These data indicate that, at an age of 1.9 Gyr, the typical X-ray luminosity Lx of the cluster members with masses of 0.8 to 1.2 solar masses is 1.3 x 1028 erg s-1, which is approximately a factor of 6 times less intense than that observed in the younger Hyades. Given that Lx is proportional to the square of a star's rotational rate, the median Lx of NGC 752 is consistent, for t >= 1 Gyr, with a decaying rate in rotational velocities vrot ~ t-alpha with alpha ~ 0.75, steeper than the Skumanich relation (alpha ~ 0.5) and significantly steeper than that observed between the Pleiades and the Hyades (where alpha <0.3), suggesting that a change in the rotational regimes of the stellar interiors is taking place at an age of ~ 1 Gyr.
NGC 752 was observed for 49 ks by the XMM-Newton EPIC camera on February 5, 2003 starting at 23:29:25 UT, and the nominal pointing was towards J2000.0 RA and Declination of (01:57:38, +37:47:60), thus the XMM-Newton field-of-view (FOV) includes the Chandra FOV. For the source detection, the authors used the PWXDETECT code developed at Palermo Observatory and derived from the analogous Chandra PWDETECT code based on wavelet transform analysis. This allows the three EPIC exposures (PN, MOS1 and MOS2) to be combined in order to gain a deeper sensitivity with respect to the source detection based on single images. There were 145 point sources detected in the energy band 0.5 - 2.0 keV. An extended source (not listed in this present table), very likely a galaxy cluster, is also visible in the EPIC data.
The authors searched for 2MASS counterparts to the XMM-Newton sources using a search radius of 5 arcsec and found a counterpart for 38 sources. As for the Chandra data, all sources with a visible counterpart from DLM94 have also a 2MASS counterpart, so this leaves 15 XMM-Newton sources with a 2MASS counterpart and no counterpart in Daniel et al. (1994, PASP, 106, 281); of these, 3 were also detected by Chandra; of the other 12, 10 are outside the Chandra FOV, while two are within it (XMM-Newton sources 58 and 65). Source 65 was caught by XMM-Newton during the decay phase of a flare, which explains why it is not detected in the Chandra data. For source 58 there is no immediate explanation for this, since the light curve does not show evidence of a flare. No additional near-IR counterpart to the XMM-Newton sources was found within the Point Source Reject Table of the 2MASS Extended Mission.
The X-ray luminosity of solar-mass stars in the intermediate age open cluster NGC 752. Giardino G., Pillitteri I., Favata F., Micela G. <Astron. Astrophys. 490, 113 (2008)> =2008A&A...490..113G
A running X-ray source number in order of increasing J2000 Right Ascension which uniquely identifies the XMM-Newton source.
The name of the XMM-Newton X-ray source using the '[GPF2008] XMM' prefix (for Giardino, Pillitteri, Favata 2008 Chandra X-ray Observatory) and the source number. This was created by the HEASARC in the absence of any naming convention for these sources having been registered with the CDS Dictionary of Astronomical Nomenclature.
This parameter flags the following possible issues about the XMM-Newton X-ray sources:
+ = source could be spurious (detection scale of ~2.8" is small for XMM) - = corresponding Chandra source does not have 2MASS counterpart
The Right Ascension of the XMM-Newton X-ray source in the selected equinox. This was given in J2000 coordinates and to a precision of 0.1 seconds of time in the original table.
The Declination of the XMM-Newton X-ray source in the selected equinox. This was given in J2000 coordinates and to a precision of 1 arcsecond in the original table.
The Galactic Longitude of the XMM-Newton X-ray source.
The Galactic Latitude of the XMM-Newton X-ray source.
The XMM-Newton X-ray source EPIC (PN+MOS1+MOS2) count rate, in counts per second. (The HEASARC believes this is in the 0.5 - 2.0 keV energy band.)
The RMS uncertainty in the count rate, in ct/s.
A running X-ray source number in order of increasing J2000 Right Ascension which uniquely identifies the Chandra source counterpart to the XMM-Newton source, as given in the NGC752CXO table.
The radial distance between the XMM-Newton X-ray source and the Chandra counterpart, in arcseconds.
The 2MASS J magnitude of the near-IR counterpart to the XMM-Newton X-ray source.
The 2MASS H magnitude of the near-IR counterpart to the XMM-Newton X-ray source.
The 2MASS K magnitude of the near-IR counterpart to the XMM-Newton X-ray source.
The radial distance between the XMM-Newton X-ray source and the 2MASS counterpart, in arcseconds.