Results from UBVRI optical photometric observations of the pre-main se- quence star V350 Cep during the period 2004-2014 are presented. The star was dis- covered in 1977 due to its remarkable increase in brightness by...Results from UBVRI optical photometric observations of the pre-main se- quence star V350 Cep during the period 2004-2014 are presented. The star was dis- covered in 1977 due to its remarkable increase in brightness by more than 5 mag （R）. In previous studies, V350 Cep was considered to be a potential FUor or EXor eruptive variable. Our data suggest that during the period of observations the star maintains its maximum brightness with low amplitude photometric variations. Our conclusion is that V350 Cep was probably an intermediate object between FUors and EXors, similar to V1647 Ori.展开更多
In this paper results from the optical photometric observations of the pre-main sequence star V1180 Cas are reported.The star is a young variable associated with the dark cloud Lynds 1340,located at a distance of 600 ...In this paper results from the optical photometric observations of the pre-main sequence star V1180 Cas are reported.The star is a young variable associated with the dark cloud Lynds 1340,located at a distance of 600 pc from the Sun in the star-forming region in Cassiopeia.V1180 Cas shows large amplitude variability,interpreted as a combination of accretion-induced and extinction-driven effects.Our data from VRI CCD photometric observations of the star were collected from September 2011 to February 2022.During our monitoring,we recorded several brightness dips with large amplitudes of up to 5 mag(I band).At the same time,increases in brightness over periods of several weeks have also been recorded.In this paper,we compare the photometric data obtained for V1180 Cas with observations of other low-mass pre-main sequence objects.展开更多
Results from optical CCD photometric observations of 13 pre-main-sequence stars collected during the period from February 2007 to November 2020 are presented.These stars are located in the association Cepheus OB3,in t...Results from optical CCD photometric observations of 13 pre-main-sequence stars collected during the period from February 2007 to November 2020 are presented.These stars are located in the association Cepheus OB3,in the field of the young star V733 Cephei.Photometric observations,especially concerning the long-term variability of the stars,are missing in the literature.We present the first longterm V(RI)c monitoring for them,that cover 13 years.Results from our study indicate that all of the investigated stars manifest strong photometric variability.The presented paper is a part of our program for the photometric study of pre-main-sequence stars located in active star-forming regions.展开更多
We present a catalog including 11 204 spectra of 10436 early-type emission-line stars from LAMOST DR2, among which 9752 early-type emission-line spectra are newly discovered. For these early- type emissionqine stars, ...We present a catalog including 11 204 spectra of 10436 early-type emission-line stars from LAMOST DR2, among which 9752 early-type emission-line spectra are newly discovered. For these early- type emissionqine stars, we discuss the morphological and physical properties of their low-resolution spectra. In this spectral sample, the Hα emission profiles display a wide variety of shapes. Based on the Hα line profiles, these spectra are categorized into five distinct classes： single-peak emission, single-peak emission in absorption, double-peak emission, double-peak emission in absorption, and P-Cygni profiles. To better understand what causes the Hc~ line profiles, we divide these objects into four types from the perspective of physical classification, which include classical Be stars, Herbig Ae/Be stars, close binaries and spectra contaminated by H n regions. The majority of Herbig Ae/Be stars and classical Be stars are identified and separated using a （H-K, K-W1） color-color diagram. We also discuss 31 binary systems that are listed in the SIMBAD on-line catalog and identify 3600 spectra contaminated by HⅡ regions after cross-matching with positions in the Dubout-Crillon catalog. A statistical analysis of line profiles versus classifications is then conducted in order to understand the distribution of Hc~ profiles for each type in our sample. Finally, we also provide a table of 172 spectra with Fen emission lines and roughly calculate stellar wind velocities for seven spectra with P-Cygni profiles.展开更多
We present a comprehensive study of star formation toward the H II re- gion Sharpless 155 （$155）. Star-formation activities therein were investigated based on multi-wavelength data from optical to the far-infrared. ...We present a comprehensive study of star formation toward the H II re- gion Sharpless 155 （$155）. Star-formation activities therein were investigated based on multi-wavelength data from optical to the far-infrared. The surface density distri- bution of selected 2MASS sources toward S 155 indicates the existence of a compact cluster, which is spatially consistent with the position of the exciting source of the Htt region, HD 217086. A sample of more than 200 sources with excessive emission in the infrared were selected based on their 2MASS color indices. The spatial distri- bution of the sample sources reveals the existence of three young subclusters in this region, among which subcluster A is spatially coincident with the bright rim of the H II region. In addition, photometric data from the WISE survey were used to identify and classify young stellar objects （YSOs）. To further explore the evolutionary stages of the candidate YSOs, we fit the spectral energy distributions of 44 sources, which led to the identification of 14 Class I, 27 Class II and 3 Class Ⅲ YSOs. The spatial distribu- tion of the classified YSOs at different evolutionary stages presents a spatiotemporal gradient, which is consistent with a scenario of sequential star formation. On the other hand, Herschel PACS observations toward the interface between S 155 and the ambi- ent molecular cloud disclose an arc-shaped dust layer, the origin of which could be attributed to the UV dissipation from early type stars, e.g. HD 217061, in S155. Four dusty cores were revealed by the Herschel data, which hints at new generations of star formation.展开更多
基金supported by ESF and the Bulgarian Ministry of Education and Science under the contract BG051PO001-3.3.06-0047
文摘Results from UBVRI optical photometric observations of the pre-main se- quence star V350 Cep during the period 2004-2014 are presented. The star was dis- covered in 1977 due to its remarkable increase in brightness by more than 5 mag （R）. In previous studies, V350 Cep was considered to be a potential FUor or EXor eruptive variable. Our data suggest that during the period of observations the star maintains its maximum brightness with low amplitude photometric variations. Our conclusion is that V350 Cep was probably an intermediate object between FUors and EXors, similar to V1647 Ori.
基金partly supported by the National RI Roadmap Project(contracts D01-383/18.12.2020 and D01-176/29.07.2022)of the Ministry of Education and Science of the Republic of Bulgaria。
文摘In this paper results from the optical photometric observations of the pre-main sequence star V1180 Cas are reported.The star is a young variable associated with the dark cloud Lynds 1340,located at a distance of 600 pc from the Sun in the star-forming region in Cassiopeia.V1180 Cas shows large amplitude variability,interpreted as a combination of accretion-induced and extinction-driven effects.Our data from VRI CCD photometric observations of the star were collected from September 2011 to February 2022.During our monitoring,we recorded several brightness dips with large amplitudes of up to 5 mag(I band).At the same time,increases in brightness over periods of several weeks have also been recorded.In this paper,we compare the photometric data obtained for V1180 Cas with observations of other low-mass pre-main sequence objects.
基金partly supported by the National Science Fund of the Ministry of Education and Science of Bulgaria under grant DN 18-10/2017funds of the project RD-08-125/2021 of the University of Shumen。
文摘Results from optical CCD photometric observations of 13 pre-main-sequence stars collected during the period from February 2007 to November 2020 are presented.These stars are located in the association Cepheus OB3,in the field of the young star V733 Cephei.Photometric observations,especially concerning the long-term variability of the stars,are missing in the literature.We present the first longterm V(RI)c monitoring for them,that cover 13 years.Results from our study indicate that all of the investigated stars manifest strong photometric variability.The presented paper is a part of our program for the photometric study of pre-main-sequence stars located in active star-forming regions.
基金supported by the National Key Basic Research Program of China (Grant No. 2014CB845700)the National Natural Science Foundation of China (Grant Nos. 11390371 and 11233004)The Guo Shou Jing Telescope (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, LAMOST) is a National Major Scientific Project built by the Chinese Academy of Sciences. Funding for the project has been provided by the National Development and Reform Commission
文摘We present a catalog including 11 204 spectra of 10436 early-type emission-line stars from LAMOST DR2, among which 9752 early-type emission-line spectra are newly discovered. For these early- type emissionqine stars, we discuss the morphological and physical properties of their low-resolution spectra. In this spectral sample, the Hα emission profiles display a wide variety of shapes. Based on the Hα line profiles, these spectra are categorized into five distinct classes： single-peak emission, single-peak emission in absorption, double-peak emission, double-peak emission in absorption, and P-Cygni profiles. To better understand what causes the Hc~ line profiles, we divide these objects into four types from the perspective of physical classification, which include classical Be stars, Herbig Ae/Be stars, close binaries and spectra contaminated by H n regions. The majority of Herbig Ae/Be stars and classical Be stars are identified and separated using a （H-K, K-W1） color-color diagram. We also discuss 31 binary systems that are listed in the SIMBAD on-line catalog and identify 3600 spectra contaminated by HⅡ regions after cross-matching with positions in the Dubout-Crillon catalog. A statistical analysis of line profiles versus classifications is then conducted in order to understand the distribution of Hc~ profiles for each type in our sample. Finally, we also provide a table of 172 spectra with Fen emission lines and roughly calculate stellar wind velocities for seven spectra with P-Cygni profiles.
基金Supported by the National Natural Science Foundation of China
文摘We present a comprehensive study of star formation toward the H II re- gion Sharpless 155 （$155）. Star-formation activities therein were investigated based on multi-wavelength data from optical to the far-infrared. The surface density distri- bution of selected 2MASS sources toward S 155 indicates the existence of a compact cluster, which is spatially consistent with the position of the exciting source of the Htt region, HD 217086. A sample of more than 200 sources with excessive emission in the infrared were selected based on their 2MASS color indices. The spatial distri- bution of the sample sources reveals the existence of three young subclusters in this region, among which subcluster A is spatially coincident with the bright rim of the H II region. In addition, photometric data from the WISE survey were used to identify and classify young stellar objects （YSOs）. To further explore the evolutionary stages of the candidate YSOs, we fit the spectral energy distributions of 44 sources, which led to the identification of 14 Class I, 27 Class II and 3 Class Ⅲ YSOs. The spatial distribu- tion of the classified YSOs at different evolutionary stages presents a spatiotemporal gradient, which is consistent with a scenario of sequential star formation. On the other hand, Herschel PACS observations toward the interface between S 155 and the ambi- ent molecular cloud disclose an arc-shaped dust layer, the origin of which could be attributed to the UV dissipation from early type stars, e.g. HD 217061, in S155. Four dusty cores were revealed by the Herschel data, which hints at new generations of star formation.
