High Energy Astrophysics at Southampton

我们的研究涉及致密天体，即白矮星、中子星和黑洞(BHS)，包括恒星大小和超大质量(SMBH)。我们的目标是了解它们是如何演化的，以及它们是如何产生辐射的。X射线双星(XRBs)，其中包含了围绕BHS和中子星的明亮吸积盘，可以详细地检查这些盘是如何变化的。因为它们变化很快，所以可以对变异性进行许多测量，让我们看到不同频率的变异性是如何联系在一起的。使用这些测量，我们可以测试关于物质如何以及为什么会通过圆盘坠入的基本想法。利用红外辐射的变化，我们可以观察喷流的变化，并了解圆盘是如何供给我们在XRBs中看到的相对论喷流的。喷流发出的强无线电辐射经常伴随着吸积，特别是在XRBs的“硬”状态下。我们将研究射电发射，如LOFAR和eMerlin等新天文台所看到的射电发射与X射线发射之间的关系，作为研究吸积/流出联系的一种手段。我们将研究为什么在硬态源中，势吸积能有时能有效地转化为辐射，有时则不能。我们将测量黑洞自转，这在确定有多少吸积能量可以被释放为辐射方面很重要。研究双星系统中的大质量恒星及其演化可以为银河系和附近星系最近的恒星形成提供重要的见解。SMC演化的恒星群体表明，最近与其伴生星系的湍流相互作用，产生了一个非常活跃的恒星形成时期。这些大质量恒星中的许多都经历了超新星阶段的演化，产生了大量的中子星。对这一群体的研究揭示了对恒星演化本质的重要洞察。积累的白矮星(AWD)具有重要的天体物理意义。它们包括Ia型超新星前体，驱动它们演化的过程在许多其他环境中也是相关的。在这里，我们将扩展我们在AWDS和相关系统演变方面的领先工作。我们将实现一条新的AWD演化轨迹，直接探测第一个亚恒星次星，确定AWD的空间密度，搜索“死亡的”AWD，并确定第一个双简并SN Ia前身。我们将研究恒星质量BHS和SMBH(即AGN)之间的关系，询问诸如变化时间尺度或能带之间的时间滞后，尺度是否仅与质量有关，还是与吸积率有关。我们将观察有喷流的活动星系核和没有喷流的活动星系核是否有不同的变化，以及X射线和伽马射线是否有不同的变化。我们将观察在有和没有喷流的情况下活动星系核中的光学和射电变化与X射线变化的关系。因此，在不同的活动星系核类型中，我们将确定不同波段的辐射是如何产生的，在哪里产生，以及它们为什么不同。来自SMBHs的大规模喷流可以延伸数百万光年的距离，不仅将能量传输到它们的宿主星系，而且还传输到周围的星系团或星系团。这种能量输入对星系和星系团的形成和演化起着重要作用。我们将使用新的射电设施，例如LOFAR和e-Merlin，来测量不同群体的射电活动星系核的能量影响，并研究它们的生命周期，以了解它们在星系演化中的作用。SMBH可能存在于所有星系的核中，但由于吸积率很低，通常无法检测到。为了研究这些主宰局部宇宙的低光度活动星系核，我们正在对附近星系的最佳选择样本Palomar样本进行灵敏的射电和X射线测量，以发现微弱的活动星系核并确定哪些宿主星系属性(如质量、恒星形成速率)对活动星系核的亮度最强控制。我们还将对射电发射、X射线发射和黑子质量之间的关系进行最干净的测量。

Our research concerns compact objects, ie white dwarfs, neutron stars and black holes (BHs), both stellar sized and supermassive (SMBHs). We aim to understand how they evolve and how they produce radiation.X-ray binaries (XRBs), which contain bright accretion discs around BHs and neutron stars, allow detailed examination of how these discs vary. As they vary quickly, many measurements of variability can be made, allowing us to see how variability at different frequencies is tied together. Using these measurements, we can test fundamental ideas about how and why matter falls in through discs. Using variations in the infrared emission, we can look at variations in the jet, and learn how the discs feed the relativistic jets we see in XRBs.Strong radio emission from the jet often accompanies accretion, particularly in the `hard' state of XRBs. We will investigate how radio emission, as seen in new observatories such as LOFAR and eMERLIN, is related to X-ray emission, as a means of studying the accretion/outflow connection. We will study why, in hard state sources, the potential accretion energy is sometimes converted efficiently into radiation, and sometimes not. We will measure black hole spin, which is important in determining how much of the accretion energy can be liberated as radiation.Studying massive stars in binary systems and their evolution gives important insight into recent star formation in the Milky Way and nearby galaxies. The evolved stellar population of the SMC points to recent turbulent interactions with its companion galaxy, producing a very active period of star formation. Many of these massive stars have evolved through a supernova phase, producing a large population of neutron stars. Studies of this population are revealing crucial insight into the nature of stellar evolution.Accreting white dwarfs (AWD) are astrophysically important. They include Type Ia Supernova progenitors, and the processes that drive their evolution are relevant in many other settings. Here we will extend our leading work on the evolution of AWDs and related systems. We will implement a new evolution track for AWDs, directly detect the first sub-stellar secondary, determine the space density of AWD, carry out a search for "dead" AWDs and confirm the first double-degenerate SN Ia progenitor.We will study the relationship between stellar-mass BHs and SMBHs (ie AGN), asking whether properties such as variability timescales, or time lags between energy bands, scale only with mass, or also with accretion rate. We will see whether AGN which have jets vary differently to those which don't, and if X-rays and Gamma-rays vary differently. We will observe how optical and radio variations are related to X-ray variations in AGN with and without jets. Thus, in different AGN types, we will determine how and where the emissions in different wavebands are produced and why they vary.The large-scale jets from SMBHs can extend for distances of millions of light years, transporting energy not only to their host galaxy but also to the surrounding group or cluster of galaxies. This energy input plays an important role in how galaxies and clusters form and evolve. We will use new radio facilities, e.g. LOFAR and e-MERLIN, to measure the energetic impact of, and investigate the life cycles of, different populations of radio-loud AGN, to understand their role ingalaxy evolution.SMBHs exist in the nuclei of possibly all galaxies but are often undetectable due to very low accretion rates. To study these low luminosity AGN, which dominate the local universe, we are making a sensitive radio and X-ray survey of the best-selected sample of nearby galaxies, the Palomar sample, to find faint AGN and determine which host galaxy properties (eg mass, starformation rate) most strongly control AGN luminosity. We will also perform the cleanest measurement yet of how radio emission, X-ray emission and BH mass are related.