arXiv subjects

J. H. Fan

Publications and source records attributed to J. H. Fan.

98 records · Page 6Linked to original sources

arXiv1999

Infrared Variation of Blazars

In this paper, the historical infrared (JHK) data compiled from the published literature are presented here for 30 blazars. Maximum near-IR variations are found and compared with the optical ones. For the color-magnitude relation, some objects show that the color index increases with magnitude while 1253-055 shows complex behaviour, which perhaps suggests that the emission mechanism consists of, at least, two parts. The spectral indexes are in the range of $α_{IR}$ = 0.77 to 2.37.

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arXiv1999

Infrared Variation of Radio Selected BL Lacertae Objects

In this paper, the historical infrared (JHK) data compiled from the published literature are presented in electronic form for 40 radio selected BL Lacertae objects (RBLs) for the first time. Largest variations are found and compared with the largest optical variation. Relations between color index and magnitude and between color-color indices are discussed individually. For the color-magnitude relation, some objects (0048-097, 0735+178, 0851+202, 1215+303, 1219+285, 1749+096, and perhaps 0219+428, 0537-441, 1514-241) show that color index increases with magnitude indicating that the spectrum flattens when the source brightens while some other objects (0754+100, 1147+245, 1418+546, and 1727+502) perhaps show an opposite behaviour, while remaining objects do not show any clear tendency; For color-color relation, it is found common that (J-K) is closely correlated with (J-H) while (J-H) is not correlated with (H-K).

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arXiv1999

Long-term infrared variation of 3C 279 and 4C 29.45

In this paper, the historical infrared (JHK) data compiled from 22 publications are presented for 3C279 and 4C29.45. Relation between color index and magnitude and between color-color indices are discussed. (J-K) is found closely correlated with (J-H) while (J-H) is almost not correlated with (H-K), which is perhaps due to two facts of (1) (J-K) shows wider distribution than (J-H) and (H-K) and (2) the spectrum deviates from the power law. For color-magnitude relation, there is a correlation of color index increasing with magnitude for 3C279 suggesting that the spectrum flattens when the source brightens. But an opposite tendency is also noted between (H-K) and J when I is fainter than 14 magnitude, which suggests that the near-IR spectrum of 3C279 consists of, at least, two components. No similar result is found for 4C29.45. The largest amplitude infrared variation is smaller than but comparable with the largest amplitude variation for the two objects.

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arXiv1998

Historic Light Curve and Long-term Optical Variation of BL Lacertae 2200+420

In this paper, historical optical(UBVRI) data and newly observed data from the Yunnan Observatory of China(about100 years) are presented for BL Lacertae. Maximum variations in UBVRI: 5.12, 5.31, 4.73, 2.59, and 2.54 and color indices of U-B = -0.11 +/- 0.20, B-V= 1.0 +/- 0.11, V-R= 0.73 +/- 0.19, V-I= 1.42 +/- 0.25, R-I= 0.82 +/- 0.11, and B-I= 2.44 +/- 0.29 have been obtained from the literature; The Jurkevich method is used to investigate the existence of periods in the B band light curve, and a long-term period of 14 years is found. The 0.6 and 0.88 year periods reported by Webb et al.(1988) are confirmed. In addition, a close relation between B-I and B is found, suggesting that the spectra flattens when the source brightens.

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arXiv1998

Correlation between the gamma-ray and the radio emissions

In this paper, the correlation between the gamma-ray and the radio bands is investigated. The results show that there is a closer correlation between the gamma-ray emission and the high frequency (1.3mm, 230GHz) radio emission for maximum data than between the gamma-ray and the lower frequency (5GHz) radio emissions, which means that the gamma-ray is associated with the radio emission from the jet.

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arXiv1998

BL Lac Objects and Relativistic Beaming Model

In this paper: 1. The assumption of the dependence of Doppler factor on the emission frequency (Fan et al. 1993) is used to explain the observational differences between the radio-selected BL Lac objects(RBLs) and the X-Ray-Selected BL Lac objects (XBLs): a) Hubble relation; b) different multiwavelength correlations; c) different regions in the effective spectral index diagram; d) different polarization. The results suggest that RBLs and XBLs are the same. 2. From the analysis of the relation between infrared magnitude and redshift, it is proposed that the parent population of BL Lac objects should be FRI radio galaxies and FRII(G) radio galaxies showing the optical spectra of a galaxy. 3. From the superluminal motion, the assumption (Fan et al. 1993) is confirmed. 4. Based on the relation between polarization and Doppler factor (Fan et al. 1997, A&A, 327, 947), it is proposed that the ratio of the beamed luminosity to the unbeamed luminosity in the source frame of OVVs/HPQs is smaller than that of BL Lac objects.

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arXiv1998

Long-term Variation of AGNs

In this paper, we will discuss the long-term variations in the optical and the infrared bands of some AGNs. It is interesting to note that the reported periods of AGNs are of the similar values (about 10 years, see Fan et al. 1998a, ApJ, 507 in press, and references therein). DCF method shows the optical and infrared bands are strongly correlated suggesting that the emission mechanisms in the two bands have a common origin.

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arXiv1998

The infrared and optical variability of OJ 287

In this paper, the long-term historical optical (UBVRI) and near-infrared (JHK) data are presented with some new observations in the optical (February 1994-January 1995) and near-infrared (November 1995) bands included for BL Lac object OJ287. The new optical data in V-band are in agreement with the results reported by other authors (Sillanpaa et al. 1996a; Arimoto et al. 1997), a close correlation between the color index of B-V and the magnitude V has been obtained from our new observations; The new infrared observations presented here indicate that the source was at a high level in the infrared band during the observation period; From the available literature, we have got that the largest variations for UBVRIJHK bands are respectively: 4.72mag, 5.93mag, 5.18mag, 4.45mag, 4.07mag, 3.87mag, 3.78mag, and 3.54mag. A strong correlation is found between the optical and near-infrared bands when the DCF method is used, which suggests that these two bands have the same emission mechanism.

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