NGC 7654: An interesting cluster to study star formation history

Pandey, A. K.; Nilakshi,; Ogura, K.; Sagar, Ram; Tarusawa, K.

doi:10.1051/0004-6361:20010642

Cited by 47 publications

(99 citation statements)

References 26 publications

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“…The discrepancy was confirmed by Nov. 18 data. We found that a similar discrepancy of the V band zero-points for NGC 7654 was also found by Pandey et al (2001). In detail, however, their magnitudes were not consistent with ours, but ∼0.09 mag fainter.…”

Section: Photometric Calibrationsupporting

confidence: 70%

The Anomalous X-ray Pulsar 4U 0142+61: Variability in the infrared and a spectral break in the optical

Hulleman

Kerkwijk

Kulkarni

2004

A&A

129

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Abstract. We present new optical and infrared observations of the counterpart to the Anomalous X-ray Pulsar (AXP) 4U 0142+61 taken with the Keck I telescope. The counterpart is found to be variable in the infrared. This contrasts with our optical observations, which do not show any evidence for variability. Apart from the variability the AXP shows a remarkable spectral energy distribution. In particular, we find a sudden drop in flux going from V to B, presumably due to a spectral feature. We compare our results to those obtained for the two other securely identified AXP counterparts, to 1E 2259+586 and 1E 1048.1−5937. 4U 0142+61 is very similar to the former source in its X-ray timing and spectral properties, and we find that this similarity extends to the quiescent infrared to X-ray flux ratio. For 1E 1048.1−5937, which has different X-ray properties, the situation is less clear: in one observation, the infrared to X-ray flux ratio was much larger, but another observation gave an upper limit which is consistent with that observed for 4U 0142+61. Assuming the quiescent ratios are all similar, we estimate the optical and infrared brightnesses for the three AXPs that remain to be identified as well as for the four Soft Gamma-ray Repeaters. We also discuss briefly how the observed optical and infrared emission might arise, in particular in the context of the magnetar model.

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Section: Photometric Calibrationsupporting

confidence: 70%

The Anomalous X-ray Pulsar 4U 0142+61: Variability in the infrared and a spectral break in the optical

Hulleman

Kerkwijk

Kulkarni

2004

A&A

129

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“…However, there is evidence that indicates non-coeval star formation in a few young open clusters (e.g. Pandey et al 2001 and references therein). Siess et al (1997), in the case of the intermediate age cluster Pleiades found that the observed morphology of the CMDs is best reproduced by invoking a large age dispersion (∼3×10 7 yr).…”

Section: Synthetic Colour-magnitude Diagrammentioning

confidence: 99%

Photometric binary content in intermediate/old open clusters

Sandhu¹,

Pandey²,

Sagar³

2003

A&A

Self Cite

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Abstract. The stellar evolutionary models by Bertelli et al. (1994) have been used to generate synthetic colour-magnitude diagrams (CMDs) of open clusters. A comparison of the synthetic integrated luminosity function (ILF) and synthetic colour distribution with the corresponding observed distributions is used to estimate the photometric binary content in three intermediate age open clusters, which is found to be about 30% in these clusters.

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“…We therefore plan to carry out extensive study of clusters showing the presence of a corona using wide field deep CCD photometric observations. The present paper is the second in that series, the first paper under this programme being a CCD photometric study of the cluster NGC 7654 (Pandey et al 2001).…”

Section: Introductionmentioning

confidence: 96%

A comprehensive study of the rich open star cluster NGC 2099 based on deep $\vec{BVI}$ CCD observations

Nilakshi¹,

Sagar²

2002

A&A

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Abstract. The CCD observations of the rich open star cluster NGC 2099 and its surrounding field region have been carried out up to a limiting magnitude of V ∼ 22 mag in B, V and I passbands for the first time. A total of ∼12 000 stars have been observed in the area of about 24 × 34 in the cluster region, as well as ∼2180 stars in the ∼12 × 12 area of the field region located ∼45 away from the cluster center. The cluster parameters determined by fitting the convective core overshoot isochrones in the V, (B − V ) and V, (V − I) diagrams are E(B − V ) = 0.30 ± 0.04 mag, distance = 1360 ± 100 pc, age = 400 Myr and metallicity Z = 0.008. A welldefined cluster main sequence spread over about 8 mag in range is observed for the first time. Its intrinsic spread amounting to ∼0.06 mag in colour is almost the same over the entire brightness and can be understood in terms of the presence of physical/optical binaries. The core and cluster radii determined from the radial stellar density profiles are 185 and 1000 respectively. Only about 22% of cluster members are present in the core region. The effects of mass segregation, most probably due to dynamical evolution, have been observed in the cluster. The mass function slope of the entire cluster is ∼−0.67 ± 0.12. It becomes closer to the Salpeter value of −1.35, if flattening in the cluster mass function due to presence of both binaries and a much more extended corona is considered.

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NGC 7654: An interesting cluster to study star formation history

Cited by 47 publications

References 26 publications

The Anomalous X-ray Pulsar 4U 0142+61: Variability in the infrared and a spectral break in the optical

The Anomalous X-ray Pulsar 4U 0142+61: Variability in the infrared and a spectral break in the optical

Photometric binary content in intermediate/old open clusters

A comprehensive study of the rich open star cluster NGC 2099 based on deep $\vec{BVI}$ CCD observations

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